Overview of cogeneration technologies of using biomass with the instructions for using profitability

analysis software1 - 2nd edition

May 2017

Prepared by: Fahrudin Kulic and Dusan Gvozdenac

The opinions and statements in this document do not necessarily reflect the views of USAID or the

United States Government

1 This document will be continuosly updated during duration of the project.

2

CONTENT

1 INTRODUCTION ............................................................................................................................. 6

2 USING BIOMASS IN ENTITY ACTION PLANS .................................................................................. 7

2.1 Using biomass in the Action Plan of Federation of BiH ......................................................... 7

2.1.1 Guaranteed purchase prices for biomass in FBiH .................................................. 8

2.2 Republika Srpska Action Plan for using biomass ................................................................... 9

2.2.1 Guaranteed purchase prices in the RS ................................................................. 10

3 BIOMASS ..................................................................................................................................... 13

3.1 Woody biomass ................................................................................................................... 13

3.2 Wet biomass ........................................................................................................................ 17

4 SIMPLIFIED PROCEDURE FOR ENERGY SYSTEM ANALYSIS ......................................................... 18

4.1 Annual or seasonal efficiency of energy systems ............................................................... 20

4.2 Energy system of the Medium Density Fiberboard (MDF) factory ..................................... 20

5 PROJECT ECONOMIC FEASIBILITY ANALYSIS ............................................................................... 21

5.1 Economic parameters ......................................................................................................... 21

6 COMMERCIAL TECHNOLOGIES FOR USING BIOMASS ................................................................ 26

7 DIRECT COMBUSTION WITH STEAM CYCLE ................................................................................ 27

7.1 Plants with a condensing turbine with one regulated extraction ...................................... 28

7.2 Steam generator (boiler) ..................................................................................................... 31

8 GASIFICATION AND GAS TURBINES ............................................................................................ 32

8.1 Technical description of the facility and processes ............................................................ 32

8.1.1 Types of gasifiers ................................................................................................. 34 8.1.2 Gas cooling and cleaning ..................................................................................... 36 8.1.3 Gas engines and electricity generator ................................................................. 37

9 DIRECT COMBUSTION WITH ORGANIC RANKINE CYCLE (ORC) .................................................. 37

9.1 Description of the facility .................................................................................................... 37

9.2 Benefits of ORC turbines ..................................................................................................... 38

10 BIOGAS PRODUCTION AND GAS ENGINES ................................................................................. 39

10.1 Biogas production process .................................................................................................. 39

10.2 Biogas yield of different organic materials ......................................................................... 40

10.3 Biogas production plants ..................................................................................................... 41

11 INSTRUCTIONS FOR USING THE COST-EFFECTIVENESS ANALYSIS SOFTWARE .......................... 45

11.1 Initial steps .......................................................................................................................... 45

11.2 Profile .................................................................................................................................. 47

11.3 Software module for technologies ...................................................................................... 48

11.3.1 General Data ........................................................................................................ 48 11.3.2 Steam turbine ...................................................................................................... 53

12 CONCLUSION .............................................................................................................................. 60

3

LITERATURE ........................................................................................................................................ 61

LIST OF FIGURES Figure 3.1 Measuring units for wood volume [29] ............................................................................ 13

Figure 4.1 Schematic of a complex energy system ............................................................................ 19

Figure 4.2 Schematic of a energy system at a wood processing plant [31] ...................................... 21

Figure 7.1 Schematic of a plant with the condensing turbine with one regulated extraction (a) and a

plant with a back pressure turbine (b) ............................................................................................... 27

Figure 7.2 Basic schematic of a steam turbine plant ......................................................................... 29

Figure 8.1 Wood biomass gasification plant ...................................................................................... 33

Figure 8.2 Counter-current gasifier.................................................................................................... 34

Figure 8.3 Co-current gasifier ............................................................................................................ 35

Figure 8.4 Cross-draft gasifier ............................................................................................................ 35

Figure 8.5 Schematic of the process .................................................................................................. 36

Figure 9.1 General schematic of an ORC plant .................................................................................. 38

Figure 10.1 Vertical and horizontal digester construction ................................................................ 42

Figure 10.2 Biogas production plant .................................................................................................. 43

Figure 10.3 Cogeneration plant schematics ...................................................................................... 43

Figure 10.4 Schematics of the raw materials and products of the biogas plant ............................... 44

Figure 11.1 Home page of the investment cost-effectiveness analysis software ............................. 45

Figure 11.2 Registration of users ....................................................................................................... 46

Figure 11.3 User sign in ...................................................................................................................... 47

Figure 11.4 User profile...................................................................................................................... 47

Figure 11.5 Steam turbine module at the home page ....................................................................... 48

Figure 11.6 General Data in the Steam Turbine Module ................................................................... 49

Figure 11.7 Help for parameter ......................................................................................................... 50

Figure 11.8 Input of parameter value that is outside the normal scope ........................................... 51

Figure 11.9 Steam turbine parameters .............................................................................................. 54

Figure 11.10 Parameters of the steam boiler .................................................................................... 55

Figure 11.11 Investment costs of a steam plant ................................................................................ 56

Figure 11.12 Operational costs of a steam plant ............................................................................... 57

Figure 11.13 Energy and financial parameters of the steam plant ................................................... 58

Figure 11.14 NPV and IRR of the steam plant .................................................................................... 59

4

LIST OF TABLES

Table 2.1 Overview of the incentivized generation of electricity from biomass from 2012-2015 in

FBIH [1] ................................................................................................................................................. 7

Table 2.2 Overview of the incentivized generation of electricity from biomass from 2016-2020 in

FBIH [1] ................................................................................................................................................. 7

Table 2.3 Guaranteed purchase prices for electricity from biomass in FBiH [19] ............................... 9

Table 2.4 Overview of the incentivized generation of electricity from biomass from 2009 – 2014 in

RS [2] .................................................................................................................................................... 9

Table 2.5 Overview of the incentivized generation of electricity from biomass 2015-2020 in the RS

[2] ....................................................................................................................................................... 10

Table 2.6 Guaranteed purchase price in KM/kWh for electricity from biomass in the RS [18] ........ 11

Table 2.7 Guaranteed purchase prices for biomass plants in BiH ..................................................... 11

Table 2.8 Guaranteed purchase prices for biogas plants in BiH ........................................................ 12

Table 3.1 Woody biomass conversion rates [29] ............................................................................... 14

Table 3.2 Dependance of wet content and moisture ........................................................................ 15

Table 3.3 Mass density and moisture of the main solid biofuels [29] ............................................... 15

Table 3.4 Mass and bulk density of the main tree species, depending on moisture [29] ................. 16

Table 3.5 Calorific value of woody biomass ....................................................................................... 16

Table 3.6 Typical biogas content ........................................................................................................ 17

Table 8.1 Gas composition resulting from gasification of coal and biomass .................................... 33

Table 10.1 The characteristics and biogas yields from domestic animals manure ........................... 40

Table 10.2 Coefficient of livestock units* .......................................................................................... 41

Table 11.1 Approximate values of the specific investments ............................................................. 52

Table 11.2 Cogeneration plants manufacturers ................................................................................ 52

5

FOREWORD

The USAID Energy Investment Activity (EIA) Project is promoting the use of biomass for energy

purposes in the agriculture and wood-processing industries. To meet this goal, one of the planned

activities is the provision of technical assistance to small and medium-sized enterprises (SME) from

these sectors in the preparation of projects for the construction of plants for generation of

electricity and thermal energy (cogeneration) using the residue from wood processing and

agriculture (biomass). Through these activities EIA wants to increase the utilization of available

biomass, increase the share of renewable energy in electricity generation and provide additional

income for the SMEs and thereby improve their businesses. An additional objective of the USAID

EIA project is to look at the adequacy of the existing legal framework and system of incentives for

the use of biomass for generation of electricity and thermal energy and propose changes to the

relevant institutions in order to improve them.

USAID EIA developed the “Catalog of energy technologies for electricity and thermal energy

generation using biomass,“2 which can assist SMEs with becoming familiar with cogeneration

technologies using biomass. This document presents the key characteristics of these technologies,

with the detailed descriptions and calculation examples being found in the Catalog; along with this

overview of technologies, the current system of incentives is also given for the production of

electricity from biomass, biomass characteristics and approach to the analysis of energy systems. In

addition, instructions for using the software are also provided, with which one can evaluate the

profitability of investing in cogeneration biomass plants. In order to provide the user a complete

overview of the calculation process, the software allows the user to change a significant number of

input parameters in the techno-economic analysis; and, in addition, the software shows the

parameter values, with the calculation based on the input parameters.

2 The Second edition of the Catalog from December 2016 is available on www.usaideia.ba.

6

1 INTRODUCTION

Bosnia and Herzegovina (BiH) signed the Treaty Establishing the Energy Community in 2005, which

aims to integrate the signatory countries (contracting parties) in the energy market of the European

Union (EU) on the basis of establishing a binding legal framework. By signing the Treaty, contracting

parties have committed themselves to implement the EU directives and regulations according to

the decisions of the Energy Community. The Energy Community issued Decision D/2012/04/MC-EnC

[6] in relation to Directive 2009/28 /EC on the promotion of the use of energy from renewable

sources. The Decision stipulates that BiH should increase the share of energy from renewable

sources from 34% in gross final energy consumption in 2009 to 40 % in 2020.

To achieve this goal, entity action plans were made for use of renewable energy sources (RES) in

which the amount of electricity that should be generated from a variety of types of RES, including

biomass are defined (see Section 2 USING BIOMASS IN ENTITY ACTION PLANS).

From Table 2.2 and Table 2.5 it can be seen that in the Federation of BiH (FBiH), the planned

generation of electricity from biomass is 30 GWh in 2020 and in the Republika Srpska (RS) 44.56

GWh, or a total of 74.56 GWh in Bosnia and Herzegovina in 2020.

The levels of guaranteed purchase prices of electricity generated from biomass are shown in

7

Table 2.3 and Table 2.6, which are the only financial incentive that exists in BiH for generation of

electricity from renewable sources, including biomass. In many countries, including Croatia,

cogeneration based on renewable resources is particularly stimulated, provided that the efficiency

of the cogeneration plant is in excess of the prescribed efficiency; but it is usually around 50%. For

such installations the guaranteed purchase price of electricity is increased by a certain amount (in

Croatia 20%). It is expected that in the near future, BiH will introduce some sort of incentive for

cogeneration from RES.

This document presents the key characteristics of commercial cogeneration technologies used in companies from the wood processing and agricultural sectors. The current system of incentives is also discussed for the production of electricity from biomass, in addition to biomass characteristics and approach to the analysis of energy systems. These topics are explained in more detail in the “Catalog of energy technologies for electricity and thermal energy generation using biomass” (Catalog), where examples of the techno-economic analysis of biomass cogeneration plants are demonstrated. These analyses, used for the development of software, were done using calculations in Excel; the instructions for use are at the end of this document. The analysis of individual projects and determination of important parameters, including the investment profitability parameter, can be done by using the software for the techno-economic analysis of selected technologies. Software users (potential investors) can easily change the input parameters used in the analysis of the project and select the economically and technically most beneficial variant.

Relevant institutions can use the software to analyze the various examples (projects) of the selected technologies and determine how many projects are viable with the current incentives, whether the existing incentives are sufficient to motivate the investors to invest in such projects and whether they will be able to achieve the planned share of biomass in the electricity generation. With the help of this software, an analysis of the parameters of the current system of incentives and their impact on the profitability of projects can be made and thus assist the relevant institutions to determine in which direction the existing regulations should be changed with an aim of achieving goals already stated in the Action Plans.

2 USING BIOMASS IN ENTITY ACTION PLANS

Energy issues in BiH are under the jurisdiction of entities, so both entities drafted Action Plans for

using renewable energy sources.

2.1 Using biomass in the Action Plan of Federation of BiH

FBiH Action Plan for the use of renewable energy sources was published in May 2014 by the Federal

Ministry of Energy, Mining and Industry (FMERI) [1]. The planned share of RES in the final

consumption of energy from RES regarding heating, cooling, electricity and transport was defined

in the FBiH Action Plan. To realize the planned consumption of electricity from RES, the quotas for

electricity produced from RES are set and they will be incentivized until 2020. The quotas for

electricity generation from biomass are shown in the following tables.

8

Table 2.1 Overview of the incentivized generation of electricity from biomass from 2012-2015 in FBIH [1]

Hours of operation

per annum

2012 2013 2014 2015

MW GWh MW GWh MW GWh MW GWh

ENERGY FROM BIOMASS

6.500 0.000 0.000 0.000 0.000 0.923 6.000 1.846 12.000

solid 0.000 0.000 0.000 0.000 0.923 6.000 1.846 12.000

biogas 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

bio-liquids 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

Table 2.2 Overview of the incentivized generation of electricity from biomass from 2016-2020 in FBIH [1]

Hours of operation

per annum

2016 2017 2018 2019 2020

MW GWh MW GWh MW GWh MW GWh MW GWh

ENERGY FROM BIOMASS

6500 2.154 14.000 2.769 18.000 3.385 22.000 3.846 25.000 4.615 30.000

solid 2.154 14.000 2.769 18.000 3.385 0.000 3.846 25.000 4.615 30.000

biogas 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

bio-liquids

0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

The table above shows that in 2016 14 GWh of electricity from biomass was planned, and all of it

from solid biomass, without the planned participation of biogas and bio-liquids. The reason for this

is that there was no interest in projects for construction of electricity generation facilities using

biogas and bio-liquids, so the quantities were not planned either. However, according to the FBiH

RES Law [29] the quantities should be revised every 18 months in regard to the project applications;

it is anticipated that in the next version, expected in the first half of 2016, biogas quotas should be

included. Since to date no biomas plant has been built in FBiH, the entire quota of 14 GWh is

available, which corresponds to the installed capacity of 2.15 MWe with 6.500 operational hours

per year at full capacity. In 2020, the electricity generated from biomass should be 30 GWh (4.61

MW of installed capacity).

2.1.1 Guaranteed purchase prices for biomass in FBiH

The Federation Energy Regulatory Commission (FERC) has approved guaranteed purchase prices

(feed-in-tariffs) for electricity from RES, shown in

9

Table 2.3 [19]. The contract on purchase of electricity at the guaranteed purchase prices with a

12-year term is signed with the Operator for Renewable Energy Sources and Efficient

Cogeneration. The table shows that the price varies depending on the installed electrical capacity

of the biomass plants and that plants are divided into four groups [19]:

1) Up to 23 kW

2) From 23 to 150 kW

3) From 10 kW to 1.000 kW i

4) From 1.000 kW to 10.000 kW

For biomass power plants over 10.000 kW capacity, electricity can not be purchased at the

guaranteed purchase price, while for the biogas plants the largest allowed capacity is 1.000 kW. It

should be noted that it is necessary to fulfill the conditions prescribed by FERC and the FBiH RES

Operator in order to achieve the right to sell electricity at the guaranteed purchase price and one of

the conditions is that all the plant’s equipment must be new.

10

Table 2.3 Guaranteed purchase prices for electricity from biomass in FBiH [19]

Type of plant according to the

type of primary

energy source

Power

Worki

ng hours

Unit value of

investment

(TINV)

Operational

and

Maintenance costs

(TR&O)

Fuel Costs

(Tgoriva)

Reimbursement factor of

invested

capital (Fz,n)

Generation

cost per

electricity unit

(TPc)

Reference

price

(RC)

Tariff

coefficient

(C)

Guaranteed

price (GC)

kW h/year KM/kW KM/kW KM/kW

h % KM/kWh KM/kWh KM/kWh

1 2 3 4 5 6 7=5+4/2

+(3*6)/2 8 9=7/8 10=8*9

Biomass Power

Plant

a) micro 23 6.500 7.000 708 0.055 13.90 0.31292 0.099458 3.1462 0.31292

b) mini 150 6.500 6.800 326 0.055 13.90 0.24987 0.099458 2.5123 0.24987

c) small 1.000 6.500 6.600 294 0.055 13.90 0.24067 0.099458 2.4198 0.24067

d) medium 10.000 6.500 6.600 206 0.055 13.90 0.22706 0.099458 2.2829 0.22706

e) large - - - - - - - - - -

Biogas Power

Plant

a) micro 23 8.000 5.800 263 0.039 13.90 0.71160 0.099458 7.1547 0.71160

b) mini 150 8.000 5.800 195 0.039 13.90 0.66637 0.099458 6.7000 0.66637

c) small 1.000 7.000 7.800 376 0.039 13.90 0.27891 0.099458 2.8043 0.27891

d) medium - - - - - - - - - -

e) large - - - - - - - - - -

2.2 Republika Srpska Action Plan for using biomass

The RS Action Plan for using renewable energy sources was published in May 2014 by the RS

Government [2]. The planned share of RES in the final energy consumption from RES in heating,

cooling, electricity and transport was defined in the Action Plan. To realize the planned consumption

of electricity from RES, the quotas for electricity produced from RES are set and they will be

incentivized until 2020. The quotas for electricity generation from biomass are shown in the

following tables.

Table 2.4 Overview of the incentivized generation of electricity from biomass from 2009 – 2014 in RS [2]

MW GWh MW GWh MW GWh MW GWh MW GWh MW GWh

ENERGY FROM BIOMASS 0.00 0.00 0.00 0.00 0.83 2.23 3.3 8.91 4.13 11.14 4.95 13.37

solid 0.00 0.00 0.00 0.00 0.00 0.00 2.0 5.91 2.5 7.39 3.0 8.87

biogas 0.00 0.00 0.00 0.00 0.00 0.00 1.3 3.0 1.63 3.75 1.95 4.5

bio-liquids 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

2013 20142009 2010 2011 2012

11

Table 2.5 Overview of the incentivized generation of electricity from biomass 2015-2020 in the RS [2]

The foregoing table shows that for the year 2016 out of the 20.05 GWh of electricity planned from

biomass, 13.3 GWh comes from solid biomass and 6.75 GWh comes from biogas, without the

planned participation of bio-liquids. In 2016, two plants in RS, with the right to sell electricity at the

incentive price, have been put into operation (http://www.reers.ba/).

The biogas plant is at the farm in Donji Zabari, with the capacity of 989 kW and an annual planned

generation of 8.275 GWh. If this plant achieves its planned generation of 8.275 GWh, it will fullfil

the total planned generation of electricity from biogas for 2017. In 2018, only the amount of 1.475

GWh would be left for another power plant on biogas.

The second plant in the incentive system in the RS is the wood biomas facility within the Toplane

Prijedor company, with the capacity of 250kW.

In 2020, electricity generated from biomass should be 44.56 GWh. The planned installed capacity

is 16.5 MW, but the quotas are filled on the basis of electricity production rather than installed

capacity. From the relation between generation and capacity, we can see that it is planned that the

plants will work 2.700 hours, which is very little to make the investment worthwhile. We can see

that in the case of biogas plant in Donji Zabari, the number of planned annual operational hours is

8.275 GWh/989 kW = 8.367 hours. Although 8.367 hours is perhaps an overly optimistic estimate,

it is closer to the real value than 2.700 hours from the action plan. This does not affect the amount

of electricity from RES that will be incentivized in the RS, it only means that the total installed

capacity will be significantly less than the planned 16.5 MW.

2.2.1 Guaranteed purchase prices in the RS

The RS Energy Regulatory Commission (RSERC) has approved guaranteed purchase prices (feed-in

tariffs) for electricity from RES, which are included in Table 2.6 [18]. The contract on purchase of

electricity at guaranteed purchase prices is signed with the Operator for renewable energy

sources and efficient cogeneration (Elektroprivreda RS) for period of 15 years. The table shows

that the price varies depending on the installed electric power of the biomass plant and that the

plant size is divided into only two groups :

1) Up to 1,000 kW, and

2) From 1,000 kW to 10,000 kW

12

For biomass power plants over 10,000 kW capacity, electricity is not purchased at the guaranteed

purchase price, while for the biogas plants the largest allowed capacity is 1,000 kW.

It should be noted that it is necessary to fulfill the conditions set out by RSERC and the RES Operator

in the RS in order to achieve the right to purchase electricity at the guaranteed purchase price, and

one of the conditions is that all the plant’s equipment must be new.

Table 2.6 Guaranteed purchase price in KM/kWh for electricity from biomass in the RS [18]

Type of plant per energy source and installed capacity

Sale in compulsory purchase per feed-in tariffs

Market sale and consumption for own needs

Feed-in tariff

KM/kWh

Referent price

KM/kWh

Premium (in feed-in

tariff) KM/kWh

Referent price KM/kWh

Premium KM/kWh

Solid biomass power plants

up to and including 1 MW 0.2413 0.0570 0.1843 0.0776 0.1637

over 1 MW up to and including 10 MW 0.2261 0.0570 0.1691 0.0776 0.1485

Agricultural biogas plants up to and including 1 MW 0.2402 0.0570 0.1832 0.0776 0.1626

Landfill gas in the efficient co-generation plant

Sale in compulsory purchase per feed-in tariffs

Market sale and consumption for own needs

Feed-in tariff

KM/kWh

Referent price

KM/kWh

Premium (in feed-in

tariff) KM/kWh

Referent price KM/kWh

Premium KM/kWh

up to and including 1 MW 0.0698 0.0570 0.0128 0.0776 0

over 1 MW up to and including 10 MW 0.0570 0.0570 0 0.0776 0

For ease of comparison of guaranteed purchase prices between FBiH and RS, the prices are shown

in parallel columns in the following two tables.

Table 2.7 Guaranteed purchase prices for biomass plants in BiH

Installed electrical

capacity (kW) FBIH (EUR/MWh) RS (EUR/MWh)

to 23 159.99 123.37 23-150 127.76 123.37

150-200 123.05 123.37 200-300 123.05 123.37

13

300-700 123.05 123.37 700-1000 123.05 123.37

1.000-2000 116.09 115.60 2.000-10.000 116.09 115.60

Table 2.8 Guaranteed purchase prices for biogas plants in BiH

Installed

electrical

capacity (kW)

FBIH

(EUR/MWh)

RS

(EUR/MWh)

to 23 363,84 122,81 23-150 340,71 122,81

150-200 142,60 122,81 200-300 142,60 122,81 300-700 142,60 122,81

700-1000 142,60 122,81

The foregoing table shows that in the RS guaranteed purchase price for electricity from plants up to

1MW capacity is constant, and it is known that the specific investment cost (EUR/kW) decreases

with the increase of capacity, so plants are more cost effective as the capacity increases. The most

cost-effective are those with capacity of 1 MW.

The higher guaranteed purchase prices for electricity are set for plants with lesser capacity in FBiH

with the aim to achieve similar cost-effectiveness for all plants, although in FBiH the range of 150 to

1000 kW is large and the specific investment price within this range is not constant. Thus, within

this group it is most worthwhile to build a plant of 1MW, if a sufficient amount of biomass can be

provided as well as the investment funds. The difference in price for biomass between 150kW and

151kW is about 5.5 %, while for the biogas that difference is as much as 58 %. This means that the

profitability of the 150kW plant will be significantly higher and thus more interesting for the

investors.

14

3 BIOMASS

Biomass is a renewable source of energy, and one of the definitions for biomass is given in the EU

RES Directive 2009/28/EC:

“biomass is the biodegradable fraction of products, waste and residues from biological origin from

agriculture (including vegetal and animal substances), forestry and related industries including

fisheries and aquaculture, as well as the biodegradable fraction of industrial and municipal waste.”

This analysis will focus on the use of solid (wood) and wet biomass, as these forms of biomass are

the most interesting in BiH for production of electricity. The decision to focus on these two types of

biomass will result in the selection of cogeneration technologies.

3.1 Woody biomass

Units used for wood volume are [29]:.

Solid cubic meter (m3), which is used for the volume of wood without gaps. This

measurement is often used for tree trunks.

Stacked cubic meter (prm) is used for neatly stacked wooden logs, but it includes the

air space.

Bulk cubic meter (nm) is used for wood chips, but it includes the air space.

Figure 3.1 Measuring units for wood volume [29]

15

The following table shows the conversion rates of stacked cubic meters (prm), bulk cubic meters

(nm) and solid cubic meters (m3) for the most common types of woody biomass.

Table 3.1 Woody biomass conversion rates [29]

The moisture of wood biomass is determined as a percentage of water weight in the entire mass of

wet biomass:

v v

s v

m mW

m m m

, (2.1)

wherein:

W - moisture, [-]

m - mass of wet biomass, [kg]

mv - water weight (moisture) in the biomass, [kg]

ms - dry biomass weight, [kg]

Often, in some cases, moisture is expressed in relation to the weight of dry biomass and called wet

content. The link between moisture and wet content is:

v

s

m WU

m 1 W

(2.2)

wherein U represents the wet content.

Very often the W and U are expressed as a percentages. Table 3.2 shows in percentages the

dependence of wet content and moisture.

16

Table 3.2 Dependance of wet content and moisture

Moisture, W % 5 10 15 20 25 30 35 40 45 50 55 60

Wet content, U % 5.3 11.1 17.6 25.0 33.3 42.9 53.8 66.7 81.8 100 122 150

With regard to moisture, woody biomass can be divided into the following groups:

Raw wood: W ≥ 40%

Partially semi dry wood: W = 20 – 40%

Semi dry wood: W = 8 – 22%

Completely dry wood: W = 0%

As can be seen from the preceding data, the moisture of biomass can be different; and if we add

that the calorific value of this biomass is dependent on moisture, then it is quite an important factor

that must be carefully analyzed in the choice of fuel, as well as in checking of the technical

characteristics of the combustion chamber or in the economic analysis of the application of the

selected or available fuel. In the absence of the accurate values of calorific value for a certain wet

content of woody biomass, the following empirical formulas can be used:

𝐻𝑑 = 18.282 ∙ (1 − 𝑊) − 2.5 ∙ 𝑊 [𝑀𝐽

𝑘𝑔] (2.3)

𝐻𝑔 = 𝐻𝑑 + 1,35 + 2,5 ∙ 𝑊 [𝑀𝐽

𝑘𝑔] (2.4)

wherein Hd is the lower and Hg the upper calorific value.

The following table shows mass density and moisture of the main solid biofuels.

Table 3.3 Mass density and moisture of the main solid biofuels [29]

17

The following table shows the mass and bulk density of the main tree species, depending on

moisture.

Table 3.4 Mass and bulk density of the main tree species, depending on moisture [29]

Elemental composition of dry woody mass is almost the same for any type of wood. The average

elemental composition of woody mass (by weight) is: 49.6 % carbon (C); 6.3 % hydrogen (H2); 44.1

% oxygen (O2), with a negligible content of nitrogen, phosphorus and alkali metals.

Table 3.5 shows the calorific values of different wood biomass for two main cases: completely dry

wood and wood with 15% of moisture. The same table shows the approximate density of the woody

biomass, as well as thermal power per cubic meter and stacked cubic meter.

Table 3.5 Calorific value of woody biomass

Type of woody biomas

Density, [kg/m3]

Calorific value

at W=0%, [MJ/kg]

Calorific value at W=15%

[MJ/kg] [GJ/m3] [GJ/prm]*

Hornbeam 830 17.01 13.31 11.05 7.73

Beech 720 18.82 14.84 10.68 7.48

Oak 690 18.38 14.44 9.96 6.97

Ash 690 17.81 13.98 9.65 6.75

Elm 680 - 14.70 10.00 7.00

Maple 630 17.51 13.73 8.65 6.05

Acacia 770 18.95 14.97 11.53 8.07

Birch 650 19.49 15.43 10.03 7.02

Chestnut 570 - 13.29 7.58 5.30

White willow 560 17.85 13.65 7.64 5.35

Grey willow 560 17.54 13.73 7.69 5.38

18

Black elder 550 18.07 14.21 7.82 5.47

White elder 550 17.26 13.52 7.44 5.21

Black poplar 450 17.26 13.15 5.92 4.14

Spruce 470 19.66 15.60 7.33 5.13

Fir 450 19.49 15.45 6.95 4.87

Pine 520 21.21 16.96 8.82 6.17

Larch 590 16.98 13.86 8.18 5.72

Douglas fir 530 19.18 15.20 8.06 5.64

In conversion from volume in cubic meters, factor 0.7 is taken factor 0.7 (Also see Table 3.1 Woody biomass conversion

rates {30}).

3.2 Wet biomass

While woody biomass is clearly defined and recognizable, moist (wet) biomass is very diverse in

origin and therefore also in the content; but the typical characteristic of wet biomass is the large

water content. Below are listed the possible raw materials that are the content of this type of

biomass, along with the composition of biogas obtained from wet biomass. The technologies for

processing this type of biomass to obtain biogas will be explained later. The produced biogas can be

used to produce thermal energy or to power engines or gas turbines and produce electricity and

thermal energy.

Biogas is mainly a mixture of methane, carbon dioxide and other gases in smaller percentages. Table

3.6 shows the typical biogas content.

Table 3.6 Typical biogas content

Methane (СН4) 50 - 65 %

Carbon dioxide (СО2) 30 - 45 %

Water (Н2О) 0 - 5 %

Nitrogen (N2) 0 - 3 %

Oxygen (О2) 0 - 1 %

Hydrogen sulfide (Н2S) < 1 % (vol)

Temperature 30° С

Pressure 1.0 bar

Density around 1.25 kg/m3 with 55%

СН4

Thermal power around 5.5 kWh/m3 (4,4

kWh/kg)

Some of the types of raw material for the production of biogas are: different types of industrial

waste, agricultural residue, manure from domestic animals, cultivated biomass generated by waste

water treatment and sewage. Agricultural waste is mixed, and, as a result, bacterial activity is

19

increased, especially if the waste is in a state of decay. Fresh plant material can be used in order to

increase the yield of biogas.

4 SIMPLIFIED PROCEDURE FOR ENERGY SYSTEM ANALYSIS

The simplified approach to the analysis of energy systems is based on the introduction of the

efficiency degree or effectiveness of the various energy processes within a plant. The proposed and

implemented calculations for the individual plants are relieved of the largely theoretical analysis;

only brief reminders of all terms necessary for a complete understanding of the problem are given.

As a result, engagement in deeper explanations and proof (of the important settings and conclusions

which thermodynamics and other scientific fields can offer) has been avoided.

The complexity of an energy system depends on the number of fuels used, the number and

complexity of the energy transformations carried in it, the number of the energy subsystems,

control modes of the individual subsystems, and the whole system, and so on. A schematic of a

complex energy system is shown in Figure 4.1. Within the limits of a system, which should be

defined, there are N energy subsystems. Each subsystem can have several of its own subsystems.

Energy carriers used by an energy subsystem enter through an energy system border. It may be

natural gas, electricity, biofuel or some other types of energy carrier. Each subsystem is designed to

use some type of fuel with the purpose of energy transformation.

Energy exits the subsystem, but in a form that is a necessary for the production process (steam for

wood steam treatment, compressed air to power machines, hot water for heating, and others). Each

energy transformation is accompanied by the emergence of energy losses.

According to the law on energy conservation, the total amount of energy in an isolated system remains constant over time. So, energy can not be destroyed, nor created from nothing; it can only move from one form to another. So, for the complex energy system in Figure 4.1 , the following can be written:

∑ 𝐸𝑢𝑙(𝑖) =

𝐼

𝑖=1

∑ 𝐸𝑖𝑧(𝑗) +

𝐽

𝑗=1

∑ 𝐸𝑔𝑢𝑏(𝑘)

𝐾

𝑘=1

(3.1)

20

Figure 4.1 Schematic of a complex energy system

The efficiency of the energy system can be defined in the following way:

𝜂 =∑ 𝐸𝑖𝑧(𝑗)𝐽

𝑗=1

∑ 𝐸𝑢𝑙(𝑖)𝐼𝑖=1

= 1 −∑ 𝐸𝑔𝑢𝑏(𝑘)𝐾

𝑘=1

∑ 𝐸𝑢𝑙(𝑖)𝐼𝑖=1

(3.2)

From this equation it can be seen that the problem of efficiency is aimed at the reduction of losses.

It can be defined, in the same way as was done for the entire energy system, for each subsystem or

device within it.

Therefore, the quality of the very complex processes of energy transformation is reduced to a

number in the interval 0 to 1. Determination of this number implies complete knowledge of the

process to be performed, and performing the test that would experimentally determine the value

or by taking the efficiency value from the literature or by assessment based on practical experience.

The concept of the calculation will be explained using the example of the complex energy system of

one paper mill. The goal is to determine the real energy consumption of fuel in the energy

transformation in order to assess the technical and economic efficiency of the individual processes

and the work of the entire plant. In so doing, complex technical calculations are avoided; but the

accuracy of the calculation is sometimes reduced, which at this stage is not necessary anyway.

21

4.1 Annual or seasonal efficiency of energy systems

The manufacturers of energy equipment state, as a rule, the nominal energy efficiency of their

products, which is measured when tested under the conditions and parameters required by the

applicable standard that provides the rules for analysis of the measurement result. The testing is

usually carried out under full load and stationary conditions of the plant.

In actual production, the conditions in which the plant or equipment works may significantly differ

from the standard prescribed conditions, and the number of starts and stops of the energy system

may be very high. This means that the operation of the plant is very nonstationary and that it can

operate under a reduced load.

For the calculation purposes that we propose here, it is necessary to be familiar with degrees of

efficiency of the analyzed energy system that reflect operational conditions throughout the year-

round or seasonal period, if the plant does not operate all year round. Such degree of efficiency is

lower than the nominal level of efficiency stated by the manufacturer of equipment.

For example, the nominal efficiency of modern conventional boilers for heating in the system

70/90°C is about 90%, but the common value of the seasonal efficiency is only about 65%, which is

a big difference. This indicates the need for a careful analysis of the efficiency of the relevant system

in the context of the conditions in which the system works over a longer period of time.

4.2 Energy system of the Medium Density Fiberboard (MDF) factory

In wood processing plants, large amounts of heat energy are needed for drying and/or steam heat

treatment of wood. In addition, wood processing plants are also large consumers of electric energy,

making them suitable for the application of CHP technologies. In this chapter, we will briefly discuss

the application of an ORC turbine at a Medium-Density Fiberboard (MDF) factory [32].

The MDF factory requires 20MWth for drying and 20 MWth for other production processes. The

required heat energy is provided by a boiler fueled by wood residues from the production process.

Electricity is supplied by the grid. If an ORC system is installed, the factory can fully utilize all the

heat from the ORC system and additionally generate 1.45 MW of electric energy. Generating

electricity in this way is much more efficient than in typical power plants and additionally, there are

no transmission losses as the electricity is consumed at the plant itself.

The efficiency of the biomass boiler is not shown in Figure 4.2, but one should consider calculating

the overall efficiency of the system. If we assume that the efficiency of the biomass boiler is 80%

and to produce thermal energy of 48.3MWth, the total of 60.40MW biomass is necessary

(48.3MWth / 0.8 = 60.4MW). If the equation 3.2 is used, the overall efficiency of the system is:

𝜂 =∑ 𝐸𝑜𝑢𝑡(𝑗)𝐽

𝑗=1

∑ 𝐸𝑖𝑛(𝑖)𝐼𝑖=1

=20 + 20 + 1.45

60.4=

40.45

60.6= 66.7% (3.3)

22

Figure 4.2 Schematic of a energy system at a wood processing plant [31]

5 PROJECT ECONOMIC FEASIBILITY ANALYSIS

An important part of the preparation of each project is to calculate its economic feasibility. The aim

of calculating the viability of the project is to determine the economic profitability of the project.

5.1 Economic parameters

Profitability analysis requires that the following economic parameters are quantified as precisely as

possible:

Investment I0 [KM]

Annual net income (savings) B [KM/year]

Technical/Economic lifetime n [year]

Nominal interest3 rate rN × 100 [%]

Effective interest rate rE × 100 [%]

Real interest rate rR × 100 [%]

The interest rate r × 100 [%]

The inflation rate b × 100 [%]

a. Investment, I0

3 Interest is the cost of borrowing money and compensation for the creditor (the bank) for the risks assumed when entrusting one's

own money to others.

23

The investment includes all expenses related to the overall investment project. Investments in the

project usually include all expenses such are designing, obtaining permits, component procurement

and procurement of equipment and devices, installation, inspection and testing, training and

unplanned expenses.

b. Annual net income or Net savings, B

The annual reported net income or realized net savings is the actual annual value of money

[KM/annual], which is the result of the investment (Io). For projects for energy production, the

annual net income can be expressed as:

B = (𝑆𝑒 ∙ 𝐸𝑒 + 𝑆𝑡 ∙ 𝐸𝑡) − 𝑃&𝑂 (4.1)

where:

B Annual net income, [EUR/annual]

Se Annual net electricity generation, [kWh/annual]

St Annual net thermal energy generation, [kWh/annual]

Ee Electriciy unit price, [EUR/kWh]

Et Thermal energy unit price, [EUR/kWh]

P&O Operation and maintenance costs (EUR/annual)

Annual net production of electricity is equal to the gross electricity production less the consumption

of the energy plant (pumps, fans, biomass conveyor system). If in addition to the net production of

energy there is other indirect income (savings), such as reduced fees for peak power [KM/kWe] or

reduction of fees for environmental pollution, then they should be included in the calculation of

income. The unit price of electricity (Ee) is the valid guaranteed purchase price of electricity (see

Section 2). The unit price of thermal energy (Et) is the valid market price that varies from project to

project and can not be higher than the price paid by the buyer of the moment or how much it costs

the buyer to produce that energy. The cost of the power plant operation includes the cost of labor,

fuel (biomass) and maintenance; this should be taken into account in order to get the annual net

revenue of the project (B). Therefore, the annual net income from the project (B) will be equal to

the revenues obtained from the sale of energy minus operating and maintenance costs, as indicated

in the equation 4.1.

c. Technical/economic lifetime, n

Economic lifetime: The practical life of the investment/equipment or the time after which it is

profitable to replace it with new equipment.

24

Technical lifetime is the physical life of the investment and how long the equipment can operate

effectively.

If components/products are replaced before they wear out as a result of the availability on the

market of the new and efficient components, then the economic lifetime is shorter than the

technical lifetime. Changes in standards and regulations, energy prices, the level of comfort, etc .

can also lead to the replacement of equipment before the end of its technical lifetime.

To calculate the economic profitability of investments in cogeneration biomass plants, the validity

period of the contract for purchase of electricity at a guaranteed purchase price is used. The

reason for this is that this is a period for which we know exactly what the price of electricity is and

that all electricity produced will be sold at that price. Then the income from electricity sale is

constant, which is the assumption used in the calculation.

Interest is another component of calculating economic profitability:

Nominal interest rate (rN) is the one written in the contract between the parties. This is a relative number (percentage) that specifies how many units of currency is to be paid per unit of credit in one year. A fixed rate was used in the calculation process.

Real interest rate (rR) is the nominal interest rate adjusted for estimated inflation. The real interest rate adjusted for inflation is:

𝑟𝑅 =𝑟𝑁−𝑏

𝑏+1 (4.2)

d. Savings in the bank (forward movement)

If a certain amount of money B0 (KM) is in the bank and if the nominal interest rate is rN , the question

is how much money will be in the bank after "n" years?

The basic parameters of such question are:

Bo The amount of money in the bank today;

Bn The amount of money after “n” years;

rN Nominal interest rate of the bank;

n Time (years) the money is in the bank.

The value of money in the bank after the expiry of the nth year is:

Bn = Bo ∙ (1 + rN)n (4.4)

25

e. Discounted value (backward movement)

All income from the cogeneration plant occur in the future, so it is necessary to calculate the present

value of the future income. If the income of the n-th year is Bn [EUR], then the present value of that

money, B0, using the same equation as in saving money (forward movement), equal to:

𝐵𝑜 =𝐵𝑛

(1+rN)n (Discounted value) (4.5)

where 1

(1+rN)n is the discount factor.

f. Calculating the economic profitability

There are several methods for calculating the economic profitability of the investment. Here, the

following will be considered:

- Pay Back period (PB) - Net Present Value (NPV) - Internal Rate of Return (IRR)

g. Payback period (PB)

Simple payback period is the ratio of the investment and the annual net income and represents the

time it takes to recover the investment on the basis of the equal annual net income prihoda (B1 =

B2 = ... = Bn), not counting the interest.

𝑃𝑎𝑦𝑏𝑎𝑐𝑘 𝑝𝑒𝑟𝑖𝑜𝑑 =𝐼𝑛𝑣𝑒𝑠𝑡𝑚𝑒𝑛𝑡

𝐴𝑛𝑛𝑢𝑎𝑙 𝑛𝑒𝑡 𝑖𝑛𝑐𝑜𝑚𝑒 =

𝐼𝑜

𝐵 [𝑔𝑜𝑑]

The payback period method is the simplest tool for quick calculation, but the limitations must be

recognized:

- It should be used only when the real interest rate is low,

- Must be used for a repayment period that is shorter than five years,

26

- The method does not take into account the value of annual income after the repayment.

h. Net Present Value (NPV)

In order to be able to compare the projects with different amounts of investments, but also the

different future annual revenues and a different economic lifetime, it is necessary that the future

value of the annual net income is discounted to the present value when making investments.

The NPV of the project is the present value of all future annual net income over the economic

lifetime (from the first to the nth year), reduced by the investment amount:

𝑁𝑒𝑡 𝑝𝑟𝑒𝑠𝑒𝑛𝑡 𝑣𝑎𝑙𝑢𝑒 (𝑁𝑃𝑉) = 𝐷𝑖𝑠𝑐𝑜𝑢𝑛𝑡𝑒𝑑 𝑣𝑎𝑙𝑢𝑒 𝑜𝑓 𝑡ℎ𝑒 𝑛𝑒𝑡 𝑖𝑛𝑐𝑜𝑚𝑒 − 𝐼𝑁𝑉𝐸𝑆𝑇𝑀𝐸𝑁𝑇

The profitability criteria is NPV > 0.

If the annual net income is different every year; B1 ≠ B2 ≠ B3 ≠ ...... ≠ Bn, the net present value is:

NPV = [B1

(1+r𝑅)1 +B2

(1+r𝑅)2 + ⋯ +Bn

(1+r𝑅)n] − Io (4.6)

In many projects, for net income it is usually assumed that it is the same for each year; B1 = B2 = ...

= Bn. Then, the equation for the net present value can be simplified:

NPV = B ∙1−(1+r𝑅)−n

r− Io (4.7)

i. Internal Rate of Return (IRR)

IRR is the discount rate for which the net present value equals zero, i.e., the discounted value of the

future income is equal to the investment. In the following equation, the IRR should be determined

taking into account the known parameters of the problem.

NPV = B ∙1−(1+IRR)−n

IRR− Io = 0 (4.8)

27

The Internal Rate of Return (IRR) is equal to the maximum interest rate of the loan that the project

can accept without creating a loss. The IRR is used to assess the validity of the financial investment

proposal.

6 COMMERCIAL TECHNOLOGIES FOR USING BIOMASS

The basis for the selection of commercial technologies applicable in BiH are the projects in the region (implemented or under implementation), primarily in Croatia and Serbia and the reports by the international agencies for energy, such as the EU Directorate-General for Energy, IRENA – International Renewable Energy Agency, IEA - International Energy Agency and REN 21 - Renewable Energy Policy Network for the 21st Century.

The nominal capacity of the plant is very important in the selection of technology. This section will examine the examples of power plants up to 2 MW capacity, but the focus is on plants with 100kW to 700kW capacity, for which the raw material can be provided by one company or farm in BiH. Most farms and wood-processing companies are small and do not have sufficient quantities of biomass available to make it worthwhile to invest in a biomass plant.

The type of biomass is of a great importance: its quality should be satisfactory and with no significant variations to ensure security of supply and price stability. These are conditions that in the longer term can ensure that the plant is profitable. In the wood-processing industry, it is clear that biomass is wood and in agriculture the residues from crop farming and animal farming are available.

Only the possibility of using the residue from animal farming for biogas production through the process of anaerobic digestion and biogas combustion in the gas engine will be examined in this section. Single stage and two-stage anaerobic digestion will be considered, since single stage digestion is often used for smaller capacities (up to 300 kWe) and two-stage digestion for larger capacities.

The possibility of direct combustion of the crop residue will not be considered because farms in BiH are too small to provide sufficient amounts of residue needed to build a cogeneration plant.

So, the cogeneration technologies for using biomass from wood industry and animal farming and which will be analyzed for implementation in BiH are:

1. Combustion with steam cycle 2. Gasification and gas engines 3. Combustion with Organic Rankin Cycle (ORC) 4. Generation of biogas and gas engines.

28

7 DIRECT COMBUSTION WITH STEAM CYCLE

Figure 7.1 shows two main schematics of cogeneration plants with a steam cycle and direct combustion of biomass in a steam boiler. In smaller facilities, which are of interest in this analysis, we include industrial condensing turbines with steam for heating outside the block of the power plant (a) and facilities with a back pressure turbine (b).

K

T1

T2

G

P1

GV

RV1

Kon

NPk

NP1

(a)

K

T1 G

P1

GV

NP1

(b)

(K – boiler, GV – main vent; T1 – high pressure part of the turbine; T2 – low pressure part of the

turbine; G – generator; RV- regulation valve; P – feeder; Kon – condenser; NP – feeder pump)

Figure 7.1 Schematic of a plant with the condensing turbine with one regulated extraction (a) and a plant with a back pressure turbine (b)

29

7.1 Plants with a condensing turbine with one regulated extraction

The steam produced in the steam boiler is fed into the high pressure part of the turbine. Part of the

steam flow is extracted through one or more ports for extraction. Extracted steam is discharged

mainly to heat the premises or for the purposes of a technological process. A smaller portion of the

extracted steam is typically supplied to the devices for regenerative heating of the condensate.

Regenerative heating of the condensate increases the efficiency of the steam cycle but is not part

of the useful heat of the cogeneration plant. It is not calculated directly in the efficiency or

effectiveness of the cogeneration cycle, but only indirectly through the increase of the efficiency of

the steam cycle. The remainder of the steam after all extractions is drained through the last stage

of the turbine condenser.

The total flow of steam in the boiler is passed through a turbine, and the resulting mechanical power

is used to generate electricity. After passing through the turbine, the entire flow goes to the needs

of the process. Steam pressure is pre-determined and depends on the thermal needs of the process.

Steam temperature at the end of the expansion depends on the turbine efficiency. It is clear that

the previous schematic (condensing turbine with one extraction) can work as a back pressure

turbine if in the extraction process the total steam flow is taken away.

Therefore, the schematic in Figure 7.1 a is far more flexible and more suitable for industrial needs where the operation mode changes of the numerous and independent processes are frequent. We will futher consider only condensing turbines with extraction, as it is the general case that encompasses the back pressure turbine.

When the steam reaches the pressure (and temperature), after partial expansion in the turbine,

which is necessary in any process, that same steam (with the required mass flow rate) is extracted

from the turbine. The remaining flow of steam in the turbine continues further expansion in the

coming stages of the turbine up to the condensing pressure. Here, the operation of the turbine with

one extraction is described, but there are turbines with more extractions. Such turbine is much more

elastic in operation than the back pressure turbine because it allows significantly greater changes in

steam consumption at the consumers end. If the steam consumption of consumers is zero, then the

turbine is working as a condensing turbine. All the steam is used for production of electricity only;

and in that case, there is no cogeneration. At the other extreme case, if the consumption of the heat

is high, the turbine will operate as a back pressure turbine and the low pressure part of the turbine

loses steam. In that case, the production of electricity will constitute cogeneration.

Figure 7.1a shows the steam turbine with one extraction, as addressed in this example. T1 is the high-pressure part of the turbine, and T2 is the low pressure part. Both parts can be in a common housing but also can be separate. The high pressure part of the turbine (T1) gets fresh steam from the boiler, and the regulator main valve (GV) adjusts the flow of steam by maintaining a constant speed. After passing through the high pressure part of the turbine and the conversion of thermal energy of steam into the mechanical energy handed over to the shaft of the turbine, a part of steam with the given pressure and temperature is fed to the consumer (P1). The rest of the steam is sent to the low pressure part of the turbine (T2). This flow of steam passes through the control valve

30

(RV1), which manages the set pressure of the extracted steam from the consumer P1. This means that the flow of steam in the low pressure part of the turbine is directly dependent on the pressure at the extraction point P1.

The shaft of the turbine is (through the redactor) connected to the generator, which generates

electricity.

The condenser is a classic heat exchanger through which steam is converted back into a liquid state,

after expanding in the turbine. The condensate is pumped back to the boiler. The pressure in the

classic condenser is very small (negative pressure from 0.04 to 0.08 bar). Since the condenser is also

the heat exchanger, it is necessary to provide a fluid that will deliver this heat, in order to condense

the steam. The temperatures of the condensing steam that correspond to the pressure in the

condenser are from 30 to 45°C, and the suitable fluids are those practically found in the environment

(water and air).

There are many losses that occur in cycles in which a steam turbine is used. In equation (7.1) only

two losses are explicitly shown, because the equation relates only to the turbine part of the

cogeneration plant. The cogeneration plant includes also the boiler as shown in Figure 7.2, which

represents the simplest schematic of a steam turbine cogeneration plant.

K TG

KonNP

h1

hv

Mgorivo

Q1

Q2

h2

p1

p2

Figure 7.2 Basic schematic of a steam turbine plant

The overall efficiency of the electricity production cycle of the steam turbine is the product of the

individual efficiency degrees. Thus, it can be written that:

31

(7.1)

where

NGen – generator power

h1 – enthalpy of the steam leaving the boiler (turbine inlet)

h2 – enthalpy of the steam at the turbine exit

hv – enthalpy of the feed water at the inlet of the boiler

Hu – lower thermal power of the fuel

F – fuel consumption for producing one kilogram of steam

Effective efficiency of the turbine from the equation (7.3) is the product of the following efficiencies:

(7.2)

The range of values of the certain levels of efficiency is very large. For example, the effective

efficiency (ηe) can reach 0.88 for very large turbines, but for a very small turbine, it can fall to 0.50.

32

Therefore, a careful and detailed analysis of the turbine parameters is required as a part of the plant

design.

7.2 Steam generator (boiler)

A large number of boiler types or steam generators can use biomass to produce steam of the

appropriate pressures and temperatures to drive steam turbines. Technological solutions are very

diverse and usually maximally adjusted to the type and condition of the biomass to be used as fuel.

While with conventional fuels there are precise standards that guarantee the quality parameters of

the fuel, with biomass that is not the case. It is very difficult to maintain and provide reliable quality

parameters of biomass, so it may cause a malfunction of the boiler and variable parameters of the

steam leaving the boiler.

Some biomass types, such as straw and residues from the processing of fruit, can be alkaline and

contain aggressive compounds, such as chlorine. To avoid or reduce the risk of ash slugging due to

fly ash of low melting temperature, the erosion of the abrasive fly ash and corrosion, the

manufacturers of boilers for biomass combustion traditionally avoid more pressure of the steam.

The advantages of biomass combustion are:

- Negligible CO2 emissions (i.e., zero emission4), - Very low emissions of sulfur dioxide, - Ash left over after burning can largely be used as fertilizer in the agricultural production.

Disadvantages of biomass combustion:

- Low energy density, - A large area for storage of biomass is required, and - Expensive transport.

4 This refers to the practice of growing biomass where carbon dioxide emission resulting from the biomass combustion is compensated

for by the used carbon dioxide in the process of biomass production.

33

8 GASIFICATION AND GAS TURBINES

Out of one kilogram of dry woody biomass it is possible to produce about 2 Nm3 of gas with a

heating value of 1.4 up to 2.4 kWh/ Nm3. Prepared woody biomass is injected into the reactor

where the process of drying, thermal decomposition, reduction, oxidation and gasification take

place. The result is a degradation of organic molecules and the creation of C, CO, CO2, H2 and CH4

atoms/molecules. After the process of cooling and elimination of condensate, tar and soot, the

resulting gases are transported to end users. Such gas can be used in many ways, just like the well-

known natural gas. Yet, this synthesis gas has much lower heating value than natural gas, which is

approximately equal to 10 kWh/Nm3.

8.1 Technical description of the facility and processes

The main components and processes of the woody biomass gasification plant are: - Storage, preparation and drying of biomass; - Gasification; - Cooling and purification of biogas; - Gas engine or turbine and electricity generator;

Storage, preparation and drying of biomass

Fresh forest woodchips are stored under a covered ventilated space. The moisture content of such

woodchips is usually from 45% to 50%, and the woodchips’ size is from 20 to 100mm of irregular

shape.

The manufacturer of a gasification reactor prescribes the conditions to be met for the wood chips

before being placed in the reactor. One of the important conditions, besides its size, is the 10%

moisture content.

Gasification

In terms of technology, the gasification process means the production of fuel gas and coke residue

by thermal destruction of fuel in the absence of oxygen. During the gasification process, organic

particles are transformed into gas and small amounts of liquid and solid residues containing carbon

and ash. Removal of solid particles is accomplished by appropriate equipment such as electrostatic

precipitators.

Figure 8.1 is a schematic illustration of a plant for biogas production from biomass and its use to

generate electricity. The three main parts of this plant are 1) a reactor (gasifier) or device used for

gasification, 2) a gas engine in which the generated gas is converted into mechanical energy, and 3)

a generator that converts mechanical energy into electricity. Instead of a gas engine, a gas turbine

may be used for larger capacities. The other parts of the plant shown in Figure 8.1 are auxiliary, but

34

very important, devices that enable the effective and efficient operation of a plant. Their function

will be explained later.

Figure 8.1 Wood biomass gasification plant

In the process of gasification, the solid biomass is transformed into fuel gases (volatiles), which

retain most of the initial fuel value. This syngas composition may vary depending on the

temperature, pressure and atmospheric conditions, or the type of process used. For comparison,

examples of the gas composition for coal or biomass gasification, as well as natural gas composition,

are included in Table 8.1. Calorific value of the gas produced by biomass gasification is 1.4-2.4

kWh/Nm3 (5.04 – 8.64 MJ/Nm3). Biogas contains numerous harmful substances at the outlet of the

reactor, such as nitrogen and sulfur oxides, heavy hydrocarbons (tar), ash and others. If the gas is to

be used in internal combustion engines, the gas must be cleaned to the extent required by internal

combustion engines. If the gas will be used in boilers, the level of purification needed is lower; but

if a gas turbine is used, then it must be additionally cleaned.

Table 8.1 Gas composition resulting from gasification of coal and biomass

Composition Coal gasification Syngas Natural gas

Hydrogen (H2) 14.0% 18.0% --

Carbon-monoxide (CO) 27.0% 24.0% --

Carbon-dioxide (CO2) 4.5% 6.0% --

35

Oxygen (O2) 0.6% 0.4% --

Methane (CH4) 3.0% 3.0% 90.0%

Nitrogen(N2) 50.9% 48.6% 5.0%

Ethane (C2H6) -- -- 5.0%

Mercury (MJ/Nm3) 6.07 5.03 37.33

8.1.1 Types of gasifiers

Fixed-bed gasifiers are classified based on the direction of fuel flow compared to the flow direction

of the gasifying agent (air, steam or O2): co-current, counter-current and cross-draft gasifiers.

Figure 8.2 Counter-current gasifier

During the co-current gasification (Figure 8.3), the syngases are drawn out through the cooler zone

towards the outlet. This is the reason why large molecules of hydrocarbons do not decompose, so

the gas must be additionally purified. This method is used very often, since it is more suitable for

biomass with a higher moisture content. Most of biomass gasifiers with the capacity less than 1MW

that are currently operational in Germany, are of this type [23]. Therefore, this type of gasifier is

the most appropriate for use in BiH.

The basic characteristics of the co-current gasifier in comparison to others are:

- More complex structure - High requirements in regard to fuel preparation: low flexibility in regard to size of

particulate matter (only wood chunks) and moisture (< 20 %) - Gas contains a low percentage of tar - Short ignition time and start up time - Fast response

36

- Used for long-term processes - Not suitable to use fuels with high ash content

Figure 8.3 Co-current gasifier

Cross-draft gasification is the simplest process (Figure 8.4). The fuel is fed through the opening on

the reactor wall into the layer that immediately comes in contact with hot air. Direct contact of the

hot content layer and the new fuel provides high efficiency of this process. Standard temperature

of the syngas is from 700 to 850oC.

Figure 8.4 Cross-draft gasifier

The quality of fuel being gasified is a function of its carbon content, granulation, uniformity, bulk

density, tar, ash and moisture content and combustion speed.

The process during the woody biomass transformation into electricity and description of inter-

process and operations is shown in Figure 8.5.

37

Figure 8.5 Schematic of the process

8.1.2 Gas cooling and cleaning

The syngas temperature at the outlet of the co-current gasifier (reactor) is about 750 oC. The gas is

cleaned and cooled down to 60 oC in several consecutive procedures, after which is filtrated. Thus,

prepared gas is cooled, without the presence of tar, ash and dust, and can be used in a gas engine

(or turbine).

The cleaning and cooling system is mostly closed, and all by-products are returned to the reactor

and subsequently subjected to decomposition.

38

8.1.3 Gas engines and electricity generator

The gas engine is a classic Otto engine, only adapted to the expected composition of the generator

gas. The level of efficiency of such engines in the production of mechanical power is 35-40%. Useful

thermal energy occurs from the engine coolant and combustion products. The liquid temperature

at the outlet of the engine is 75-90, and 60-80 °C at the entry. The temperature of the combustion

products is 500-550 °C.

A smaller capacity electricity generator used in these applications has low voltage and a frequency

of 50 Hz. The level of efficiency of these generators is usually 91-93%.

9 DIRECT COMBUSTION WITH ORGANIC RANKINE CYCLE (ORC)

Organic Rankine Cycle (ORC), instead of the steam cycle, does not use water (steam) as a working

fluid, but rather organic hydrocarbons. The term ORGANIC CYCLE is just a concept of marketing; it

does not require only organic substances in the Rankine Cycle, although they are used most often.

Unlike the steam Rankine cycle, an ORC plant uses indirect fluid-thermal oil (silicon oil), which is pre-

heated at a temperature of about 300 oC. This pre-heated oil is drawn to a two-stage evaporator,

where its heat is transferred to the second circuit where the working fluid evaporates. The resulting

vapor from the working fluid is then drawn to a turbine, which is directly attached to the electricity

generator. After cooling, the steam is transferred to the capacitor, where the heat of condensation

is transferred to water. This water can be used in numerous ways, like heating, domestic hot water

or other technological process.

9.1 Description of the facility

Figure 9.1 represents a schematic of one ORC plant. The ORC module is immediately seen as a

separate unit of the plant. Within this unit are an ORC turbine and a generator. A very distinctive

device of the ORC cycle is a regenerator that preheats the ORC fluid after condensation and before

entering the evaporator.

In the second circulation round there is the thermal oil, which can achieve temperatures of around

300oC. The heating of oil is done in the biomass boiler. To heat the air for biomass combustion the

products of combustion are used (air preheater). The combustion products in the economizer are

used for hot water preparation, which can be used for heating purposes. A special circulation circuit

of thermal oil is used for the preparation of hot water for the process. This thermal energy and hot

water from the condenser and economizer is useful heat which, in addition to electricity, is the

product of this ORC plant.

39

Figure 9.1 General schematic of an ORC plant

9.2 Benefits of ORC turbines

The following points are in favor of using ORC technology over a traditional steam–turbine plant.

- Most organic fluids used in ORC plants do not require overheating,

- Isentropic efficiency of the turbine is highly dependent on its capacity. In general, ORC turbines have higher efficiency at low power than steam turbines of the same capacity,

- No preparation and control of water in the boiler,

- Installation is less complex than steam installation, which is desirable in terms of "green field" investments, or when there is no steam distribution network,

- Maintenance costs are low and plant availability high,

40

- Simple handling,

- Plant efficiency at partial load is high,

- System pressure is much lower than in the steam system, so the safety regulation is less strict,

- A highly skilled workforce not required for plant management, and

- Turbines with small capacity are available.

The following arguments should be made in favor of steam cycles compared to ORC:

- Water as a working fluid is cheap, while the ORC fluid may be very expensive or its use is limited due to environmental reasons.

- The capacity/heat ratio, which is much diversified and changeable in the steam turbine plant, results in a great possibility of harmonizing the needs for electricity and thermal energy in cogeneration plants.

- The direct use of steam in the turbine and boiler eliminates the need for an indirect fluid such as thermal oil.

10 BIOGAS PRODUCTION AND GAS ENGINES

Biogas is a mixture of different gases caused by decay of organic matter in the absence of oxygen.

Biogas can be produced from the biodegradable fraction of products, waste and residues from

agriculture and the biodegradable proportion of the industrial and municipal waste. It is a renewable

source of energy, whose use reduces global warming by preventing the greenhouse emissions of

methane gas into the atmosphere.

10.1 Biogas production process

Biogas production is done in closed isolated reservoirs without the presence of oxygen. Such tanks

are called digesters. The lack of oxygen is one of the conditions for the desired process of anaerobic

digestion. In addition to that requirement, the appropriate temperature and good mixing of the

content digester must be provided.

Wood waste, despite being biodegradable, has a high lignin content, which slows down the

hydrolysis and therefore can not be used as a raw material in anaerobic digesters. By blending

different types of raw materials, for example organic manure and the industrial waste, a higher yield

of biogas can be obtained; and thus-formed easily degradable materials can further stabilize the

anaerobic digestion. Therefore, it is useful to add agricultural residue (straw, corn residue) in a state

of decay to increase the effect of the bacterial action.

41

Biogas production influential factors

A high degree of organic matter decomposition must be achieved in the technological process of

biogas production, with a satisfactory quality and yield. Factors that influence this are: the size and

type of feedstock, the pressure in the digester, pH value, temperature, holding time, filling level,

and the chemical composition of the substrate and toxicity. More information on these parameters

can be found in the Catalog.

10.2 Biogas yield of different organic materials

Various organic materials undergoing anaerobic decay have different biogas yields. The reason is

the difference in the structure of the materials. Table 10.1 shows data on the yield of biogas for

different types of animals. The quality and quantity of biogas largely depends on the microorganism

culture used in the process. Yields are higher when adapted microorganism cultures are used than

the use of native microorganism cultures, carried by the raw material itself into the digester.

Table 10.1 The characteristics and biogas yields from domestic animals manure

Type of domestic animal

The

aver

age

dai

ly f

low

of

liqu

id m

anu

re a

t an

aver

age

shar

e O

DM

*

aro

un

d 1

1%

,kg/

d p

er L

U

OD

M p

ort

ion

in

the

liqu

id m

anu

re

Ave

rage

N2

con

ten

t in

OD

M o

f m

anu

re, %

C a

nd

N2

rati

o in

OD

M o

f

man

ure

, %

Bio

gas

yiel

d in

rela

tio

n t

o t

he

qu

anti

ty o

f O

DM

,

m3 /(

kg d

)

Ave

rage

bio

gas

yie

ld,

m3 /d

per

LU

% kg/day per LU

min-max average

Cow (milking) 45 10.5 4.7 1.7-6.0 (17-25):1 0.18-0.33 0.255 0.846-1.551

Cattle fattening 29 11.0 3.2 1.7-6.0 (17-25):1 0.16-0.32 0.240 0.512-1.024

Breeding sows 30 12.0 3.6 3.8 (6-12):1 0.34-0.66 0.445 1.224-1.980

Pigs fattening 26 11.54 3.0 3.8 (6-12.5):1 0.30-0.55 0.425 0.900-3.968

Laying hens 58 11.03 6.4 6.0-6.5 (7-15):1 0.31-0.62 0.465 1.984-3.968

Broiler chickens 48 10.62 5.1 6.3 15:1 0.30-0.56 0.430 1.530-2.856

Sheep 28 11.07 3.1 3.8 33:1 0.09-0.31 0.200 0.279-0.961

Horses 32 10.94 3.5 2.3 25:1 0.20-0.30 0.250 0.700-1.050

* ODM – organic dry material

LU – livestock unit (as animals are of different weights, the unified measure is introduced, marked by LU)

The coefficient of livestock units (Table 10.2) is used in order to replace the actual number of animals

with a virtual number that is comparable for different types of animals. So, 100.000 broilers is 0.007

x 100.000 = 700 LU. It should be noted that for milking cows and male cattle aged two years and

over LU = 1. It should also be noted that the plant should be designed and constructed based on the

assessment of potential raw materials.

42

Table 10.2 Coefficient of livestock units*

Cattle

Younger than one year of age 0.400

1-2 years old 0.700

Mail cattle, two years old or more 1.000

Heifers, two years old or more 0.800

Milking cows 1.000

Other cows, two years old or more 0.800

Sheep and goats 0.100

Equidae 0.800

Pigs

Piglets under 20 kg of live weight 0.027

Breeding sows 50kg or more 0.500

Other pigs 0.300

Poultry

Broilers (fattening chickens) 0.007

Laying hens 0.014

Ostrich 0.350

Other poultry 0.030

Rabbits, breeding females 0.020

* Taken from the European Commission's Regulation (120/2009)

10.3 Biogas production plants

The digester is typically in the form of a horizontal or vertical cylinder. Both options are shown in

Figure 10.1. The more common structure vertical concrete or steel and has good insulation, vessels

with rotating blades or submerged pumps for homogenization. The raw material enters these

vertical vessels from one side, and the digestate is discharged on the other side. Vertical concrete

or steel digesters with rotating blades or submerged pumps for homogenization are still the most

common practice in Europe. The substrate is fed in the vertical cylindrical digesters from the top,

and the fermented substrate is removed from the bottom on the opposite side of the digester. The

substrate is fed in the horizontal digesters from one side and the mixing mechanism is constructed

so that it moves the mixture into the digester from the entrance to the exit. Thus the process can

be well managed and the retention time of the mixture in the digester can be controlled. Vertical

reservoirs are simpler and cheaper to manage, but their efficiency is less than the horizontal

reservoirs, which are more expensive.

43

Figure 10.1 Vertical and horizontal digester construction

If anaerobic digestion can be done in one digester, it is a single-stage plant. If the process of

digestion takes place in two regular sets of digesters, such plant is called two-stage plant. In the two-

stage plant it is possible to optimize the working conditions with the goal of obtaining a better yield

of biogas. In the single-stage plant the duration of the process is longer, but the investment costs

are lower compared to the two-stage plant. Usually the volume of the two digesters are identical,

as well as a reservoir for the fermented substrate.

One type of the biogas plant is shown in Figure 10.2. The basic substrate is delivered continuously

or in batches into the basic substrate storage area. Since its content varies greatly, it is logical that

the production of biogas is also different in quantity and quality. The data on the characteristics of

the possible substrates are given in Table 10.1. If the basic substrate is one of those in this table,

then, for example, an additional substrate can be corn, green residue from the fields. Storage areas

should not be taken literally as a place for gathering the raw materials but as a place where

preparation for transport is performed. The cleaning of the raw materials of the possible impurities

(glass, stones) is done before entering the reservoir, as well as thickening or diluting and heating.

Such prepared substrate is a dense mass that is transferred to the digester by pump. The digester is

thermally insulated, and the substrate is retained in it for several weeks.

44

Figure 10.2 Biogas production plant

Thermal energy, which can be used for various purposes, such as heating barns and buildings, drying

fruits and vegetables or heating hot water, can be obtained by cooling the gas engine, generator

and exhaust gasses.

Figure 10.3 Cogeneration plant schematics

45

Additional positive effects in the production of biogas by anaerobic fermentation technology are

hygienization of the natural cycle of human and animal food production and obtaining high quality

natural biofertilizers or animal feed, depending on the adjustment process and subsequent

processing of the fermentation residues after the processing in the digester. The illustration of the

whole cycle and the use of digestion products is shown below. 5

Figure 10.4 Schematics of the raw materials and products of the biogas plant

5 http://www.globalseed.info/

46

11 INSTRUCTIONS FOR USING THE COST-EFFECTIVENESS ANALYSIS SOFTWARE

Software for the analysis of the cost-effectiveness of investments in cogeneration biomass plants in

Bosnia and Herzegovina (hereinafter referred to as software) was developed using the process of

calculations presented in this document. Examples of the calculation with a detailed description can

be found in the "Catalog of energy technologies for electricity and thermal energy generation using

biomass", available on www.usaideia.ba.

11.1 Initial steps

The software home page is shown in the following figure (http://biomass-

feasibility.usaideia.ba/#!/home) :

Figure 11.1 Home page of the investment cost-effectiveness analysis software

From the previous Figure it can be seen that the software encompasses the four technologies

described in this document:

1. Direct combustion with steam cycle (STEAM TURBINE)

2. Gasification and gas turbines (GASIFICATION)

3. Direct combustion with Organic Rankine Cycle (ORC TURBINE)

4. Biogas production and gas engines (BIOGAS)

For every technology there is a separate software module that opens with the click on the OPEN,

located below the appropriate technology.

When using the software for the first time, it is necessary to register by a click on SIGN UP in the

upper right corner of the home page (Figure 11.1), displaying the window as shown in the following

47

Figure. It is necessary to fill in all data and click on CREATE (it is not enough just to click on Enter

button).

Figure 11.2 Registration of users

Once you become a registered user, in order to use the software you must sign in by clicking SIGN

IN at the upper right corner of the home page (Figure 11.1), and the display window shown in the

figure below will appear. It is necessary to fill in all the information and click on SIGN IN (it is not

enough to click the Enter button). When you finish working with the software, click on the SIGN OUT

that appears at the upper right corner of the home page instead of SIGN IN (Figure 11.1).

48

Figure 11.3 User sign in

11.2 Profile

After the user logs in, the window Profile opens, which contains information about the user and

saved calculations. Saved calculations are displayed in a Profile under the name of the software

module. In the shown profile on Figure 11.4, only one calculation is saved, under the name Biogas

300 SJ FBiH, made in the software module Biogas.

Figure 11.4 User profile

49

Clicking on the existing calculation opens it so it can be worked on again. If the user wants to start a new calculation, he or she should click on the Back button, at the top left corner to open the Home page of the investment cost-effectiveness analysis software (Figure 11.1). Clicking on the OPEN butten under the picture of the technology opens the software module for that technology.

11.3 Software module for technologies

If the user clicks on OPEN under the steam turbine picture, the software module STEAM TURBINE is

opened

Figure 11.5 Steam turbine module on the home page

11.3.1 General Data

At the beginning of each software module is General Data (Figure 11.6). The data/parameters are

the same for every module, which results in the term General Data. All data within a calculation in

one software module, including general information, is independent of the data from another

calculation. The same parameters may have different values in every calculation, for example, Feed-

in tariffs.

When a registered user starts to use the sofware for the first time, all parameters are already

assigned realistic default values. This represents an additional support for users, because the

software can be used immediately, without the user having to first fill in all parameter values.

50

Figure 11.6 General Data in the Steam Turbine Module

51

Values in the gray shaded fields must be FILLED IN. Parameter values in the non-shaded fields are

calculated based on input values or the value of the parameter is fixed and the user is not allowed

to change it.

If next to the parameter an this icon appears, then clicking on that icon will open a window

with an explanation (Help) for this parameter. So, by clicking on the question mark next to the first

parameter of the Feed-in-tariff (from the tariff system for renewable energy and cogeneration—

Figure 11.4) the following window will appear:

Figure 11.7 Help for parameter

The guaranteed purchase prices of electricity are shown (Feed-in tariff-FIT) for biomass and biogas

in FBIH and RS in KM (BAM) and Euros (EUR). The software uses EUR, but the table shows the KM

value as well, since the FIT in relevant Decisions of the competent authorities are given in KM

[18,19]. Clicking on CLOSE will close the Help window.

If help is not offered for the gray shaded fields, it is assumed that the value of the parameter is

known to the user or that its value can be determined from the parameter name, such as the Annual

operating and maintenance costs (O & M) (1-5% of investments) where the range for the parameter

value is given in the parameter name. For selected non-shaded fields in this section an explanation

of the parameter is given or can be found in other sections of this document or in the Catalog.

If the user wants to change the value of a parameter, he must click on the value, delete the existing

value, enter a new one and click SAVE at the bottom of the module. The software uses a decimal

point in values rather than a comma, for example 5.5 rather than 5,5. If the user does not click on

SAVE, when exiting the module the value of parameters will not change, all parameters returning

to the previous value/default.

52

If the value of a parameter that is outside of the normal range is entered, then a window will appear

to alert the user; to continue to work, click OK. Entering such parameter values can result in

completely misleading or illogical results but it is allowed in order to enable the user to estimate the

impact of that parameter on the cost-effectiveness of the investment, such as the price of biomass

or the Feed-in tariff. The software will allow the user to enter a parameter value outside the normal

range, but will mark it in red.

Figure 11.8 Input of parameter value that is outside the normal scope

By clicking on the BACK button at the top left corner, the user returns to the home page (Figure

11.1) and can select one of the four technologies by clicking on OPEN.

CO2 emissions

The General Data also contains data related to carbon dioxide (CO2) emissions. CO2 emissions have

been calculated because some projects, loans or grants require this information. The market value

of reduced CO2 emissions was not used in the revenue calculation.

CO2 emissions are calculated so that the generated net produced electricity is multiplied by the CO2

emission factor for electricity and the produced net thermal energy with the CO2 emission factor for

natural gas. Wood chips are the renewable energy source and its emission factor is zero.

The CO2 emission factor for electricity depends on the relation of the amount of electricity

generated from fossil fuels and renewable energy sources. In BiH, electricity is mostly generated by

coal power plants and large hydro power plants. On average, about 60% of electricity produced is

generated by the thermal power plants, and the CO2 emission factor for electricity is about 0.7.

The electricity correction factor is a factor that evaluates the primary energy to produce the final

unit of electricity. This coefficient depends on the national energy mix. In BiH, about 60% is produced

from coal in thermal power plants, with an average efficiency degree of 30%, so the electricity

correction factor is about two.

53

The software is designed to analyze the cost-effectiveness of investing in biomass cogeneration

plants, so that in addition to the technical parameters, the economic parameters are essential. The

key economic parameter is the amount of the investment.

It is difficult to obtain reliable data on the amount of investment, as suppliers of equipment mainly

offer bids for specific projects and are generally not willing to give budgetary quotes, claiming that

the cost of equipment is significantly influenced by project specifics. The investors who have

implemented projects are often unwilling to share the details of investment costs. There are studies

that deal with the estimated cost of the investment in biomass cogeneration plants, but the given

ranges of specific investment costs (EUR/kWe) are large so it is difficult to choose an appropriate

value.

The best data is data for projects implemented in the region, primarily in Croatia and Serbia. The

EIA project has collected a small amount of data for specific projects and bids. This orientational

data is provided in the software section Investment cost; it is also indicated below in the following

table. This data can be used as values for estimating investment until an offer for a specific project

is obtained.

Table 11.1 Approximate values of the specific investments

Technology Electrical capacity

(kWe)

Thermal capacity

(kWt)

Total investment

(EUR)

Specific investment (EUR/kWe)

Steam turbine

1,000 4,000 5,000,000 5,000

4,700 15,000 13,000.000 2,766

Gasification 250 540 1,200,000 4,800

ORC 729 3,146 4,795,301 6,578

300 1,505 1,795,301 5,984

Biogas 150 166 1,027,260 6,848

650 800 2,400,000 3,700

1,000 1,200 3,500,000 3,500

In order for the user to obtain technical data on plants and request offers, some manufacturers of

equipment are listed below.6

Table 11.2 Cogeneration plants manufacturers

Technology Manufacturers

Steam turbine Technopa 50-3000 kW www.technopa.eu G-Team 80-5000 kW http://www.g-team.cz/ Siemens

6 Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favor.

54

Gasification URBAS do 250kW www.urbas.at Spanner Re² 30kW i 45kW www.holz-kraft.de Wegscheid do 250kW http://www.holzenergie-wegscheid.de/

ORC Turboden 200-3000kW+ http://www.turboden.eu/ Adoratec 300-2400kW http://www.adoratec.com/ GMK 250-2000kW http://www.gmk.info/

Biogas Biogest 100-2000 kW http://www.biogest.at/ BTS biogas 25-1500 kW+ http://www.bts-biogas.com/ Envitec biogas 25-3000 kW+ http://www.envitec-biogas.com/

11.3.2 Steam turbine

The steam turbine is a module for analysis of the plants using direct combustion with a steam cycle.

This facility is described in Chapter 7; it is advisable that the user read this chapter before using the

software (more details and an example of the calculation is given in the Catalog).

The steam turbine software module contains parameters used for the calculation of a steam turbine

cogeneration plant. The parameters are divided into several groups, as shown in the following

figures. The first set of parameters relates to the steam turbine. The title of the parameter set is

“Steam turbine: condensing, with one extraction”; however, the back pressure turbine case may be

evaluated by setting the parametar value of Share of steam at the extraction point to a value of

100%. By clicking on the Help icon, additional information that that will facilitate the use

of the software are displayed.

55

Figure 11.9 Steam turbine parameters

56

In the parameters for the steam boiler below, there are shaded, non shaded and green fields (Figure

11.10 below). As stated in the Reminder in the top left corner (Figure 11.6), green fields are

transferred from the General Data software module.

Figure 11.10 Parameters of the steam boiler

57

Figure 11.11 Investment costs of a steam plant

The previous figure shows that the total investment is divided into individual items that the user

enters. Depending on the project, some costs will be lower or higher than usual, or there will be no

costs; in this way, the software allows the user to more precisely define and have a good overview

of the investment costs.

58

Parameter Specific investment is calculated based on the total investment costs and the installed

electric capacity and is highlighted in blue, because it is a parameter that is most commonly used in

the literature.

Figure 11.12 Operational costs of a steam plant

The operating costs, among other data, shows Total salaries and administration, which is calculated

as the product of the parameters Number of employees and Average gross salary that the user

enters. The green-shaded parameters are either directly transferred from the General Data or are

calculated based on the parameters of this module and the General Data. All parameters are known

to the user, so the help is given only for the unit price of biomass, since the value in EUR/ton should

be entered. This requires the user to calculate that value.

59

Figure 11.13 Energy and financial parameters of the steam plant

60

At the end of the software module are the calculated values of NPV (Net Present Value) and IRR

(Internal Rate of Return). These are the key economic parameters that determine the profitability

of the investments.

Figure 11.14 NPV and IRR of the steam plant

In order to save the calculation, in the top left corner at the start of the module (Figure 11.6), under

the Remark there is an area for input of the name and description of the calculation. After input of

data. the user must click on SAVE at the bottom of the module (Figure 11.14). The saved calculation

with the given name will be shown in the Profile in the Steam turbine window. The calculation

preserves all parameters used in the calculation, including those from the General Data.

The module Steam turbine is the only one with the button CALCULATION. When the user clicks on

the CALCULATION button, the steam enthalpies are calculated depending on the input temperature

and pressures.

Gasification, ORC Turbine and Biogas

The software modules Gasification, ORC turbine and Biogas are used in the same manner as the

software module Steam turbine, so it is not necessary to provide separate instructions for their use.

It is recommended that the chapters in this document relating to each technology be read, before

using any of the the software modules.

61

12 CONCLUSION

The four commercial technologies were selected (cogeneration plants with steam; gasification

reactors for the production of synthetic gas and gas engines; Organic Rankine Cycle and

cogeneration of electricity and thermal energy; and the production of biogas and cogeneration of

electricity and thermal energy). These are the most commonly used technologies of small and

medium-sized capacities using biomass to produce electricity and thermal energy.

There are manufacturers who offer complete plants and other manufacturers who offer only parts

of a plant, so the selection of the manufacturer depends on the investor. The specific investment,

expressed as the total investment per unit of electrical capacity, has a wide range, depending on the

technology applied. In addition, the specific investment for each technology varies a lot depending

on the manufacturer. When the costs of the investment are estimated, the associated costs are

often neglected, such as the lease of land and its preparation, various permits and preliminary

design. Many parameters have to be estimated, but the most important parameter is the annual

number of hours of operation of the plant. In order to enable the maximum number of operating

hours per year, continuous collection and storage of raw biomass must be well planned.

Only when all the relevant parameters are accurately and reliably determined, the optimal variants

and reliable assessment of the investment profitability can be determined.

In addition to potential investors, this software can be used by the relevant institutions to analyze various examples (projects) of selected technologies in order to determine whether the current incentives are sufficient to motivate the investors to invest in such projects and whether they will be able to achieve the planned share of biomass in electricity production expressed in action plans. With the help of this software, an assessment of the parameters of the current system of incentives and their impact on the profitability of projects can be made. As a result, the software enables the relevant institutions to determine if the current incentives are adequate to motivate investment in projects and fulfill action plan goals and how changes in incentives will affect the profitability of the projects (such as an increase or decrease in feed-in tariffs, introduction of incentives for generated heat and VAT exemption).

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LITERATURE

1. Akcioni plan Federacije BiH za korištenje obnovljivih izvora energije (APOEF), Službene novine FBiH 48/14, 2014. http://fmeri.gov.ba/akcioni-plan-za-koristenje-obnovljivih-izvora-energije-u-federaciji-bih.aspx

2. Akcioni plan Republike Srpske za korišćenje obnovljivih izvora energije, Službeni glasnik RS 45/14, 2014.

3. Biomass Combined Heat and Power Catalog of Technologies, U. S. Environmental Protection Agency, September 2007

4. Biomass for Heat and Power – Technology Brief, IRENA and IEA-ETSAP, 2015.

5. Biomass for Power Generation, RENEWABLE ENERGY TECHNOLOGIES: COST ANALYSIS SERIES, Volume 1: Power Sector Issue 5/5, International Renewable Energy Agency (IRENA), 2012

6. Decision D/2012/04/MC-EnC on the implementation of Directive 2009/28/EC and amending Article 20 of the Energy Community Treaty, Energy Community Ministerial Council, Vienna, 2012.

7. DIRECTIVE 2012/27/EU OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 25 October 2012 on energy efficiency, amending Directives 2009/125/EC and 2010/30/EU and repealing Directives 2004/8/EC and 2006/32/EC, Official Journal of the European Union L 315/1

8. DIREKTIVA 2009/28/EZ EUROPSKOG PARLAMENTA i VIJEĆA od 23. travnja 2009. o promicanju uporabe energije iz obnovljivih izvora te o izmjeni i kasnijem stavljanju izvan snage direktiva 2001/77/EZ i 2003/30/EZ, Službeni list Europske Unije, 5.6.2009.

9. DIREKTIVA 2012/27/EU EUROPSKOG PARLAMENTA i VIJEĆA od 25. listopada 2012. o energetskoj učinkovitosti, izmjeni direktiva 2009/125/EZ i 2010/30/EU i stavljanju izvan snage direktiva 2004/8/EZ i 2006/32/EZ, Službeni list Europske Unije, 14.11.2012.

10. Dodić J, Grahovac J, Studija o obnovljim izvorima energije, DAI, Agencija za konsalting, Leskovac, 2013

11. Gvozdenac D, Morvaj Z, Ekonomska i finansijska analiza projekata energijske efikasnosti, USAID 3E, UNDP BiH, GIZ, Sarajevo, 2011

12. Gvozdenac D et al., Obnovljivi izvori energije, FTN, Novi Sad, 2010

13. Izvještaj o radu FERK-a za 2014. godinu, FERK, 2015.

14. Izvještaj o radu za 2014. godinu, RERS, 2015.

15. Izvještaj o trenutnom stanju i potencijalu u BiH za izgradnju kogeneracijskih postrojenja i elektrana na biomasu, USAID EIA, www.usaideia.ba, 2016.

16. Kako napraviti sopstveno biogas postrojenje, Program za prekograničnu saradnju IPA Bugarska-Srbija, 2013, http://www.tf.ni.ac.rs/IPA_Bul_Ser

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17. Obnovljivi izvori energije, Labudović Boris (koordinator), Energetika marketing, Zagreb, 2002

18. Odluka Broj: 01-540-3/15/R-03-34 Odluka o visini garantovanih otkupnih cijena i premija za električnu energiju proizvedenu iz obnovljivih izvora i u efikasnoj kogeneraciji, Regulatorna komisija za energetiku RS, Trebinje, 29.01.2016.

19. Odluka Broj:01-07-1052-05/1 o garantovanim otkupnim cijenama, Regulatorna komisija za energiju u FBiH, Mostar, 18.12.2015.

20. Petrović P et al., Razvoj postrojenja za proizvodnju biogasa u malim poljoprivrednim seoskim farmama, http://www.mfkg.rs/sajt/Downloads/ostalo/biogas.pdf

21. Petrović S, Pregled zakonskih obaveza jedinica lokalne samouprave u oblasti upravljanja energijom, energetske efikasnosti, primjene obnovljivih izvora energije, lokalnih planova energetske efikasnosti i emisija CO2, koje proizilaze iz usvojenih zakona o energetskoj efikasnosti i pratećih propisa, GIZ, 2014, http://www.sustainable-energybih.org/wp-content/uploads/2014/12/Pregled-zakonskih-obaveza-jedinica-lokalne-samouprave-u-oblasti-EE-i-RES-Septembar-2014.pdf

22. Pravilnik o metodologiji za utvrđivanje referentne cijene električne energije, FERK, Mostar, http://www.ferk.ba/_ba/images/stories/2014/pravilnik_revidirani_referentna_cijena_bs.pdf

23. Priručnik o čvrstim biogorivima (prevod na srpski), Fachagentur Nachwachsende Rohstoffe, 2014.

24. Razvoj i finansiranje kapitalnih investicionih projekata (PRIRUČNIK), USAID, Beograd, 2009.

25. Samer M, Biogas Plant Constructions, InTech, http://cdn.intechopen.com/pdfs/31334.pdf

26. Technology Roadmap – Biomass for Heat and Power, International Energy Agency – IEA, 2012

27. UREDBA KOMISIJE (EZ) br. 1200/2009 od 30. studenoga 2009. o provedbi Uredbe (EZ) br. 1166/2008 Europskog parlamenta i Vijeća o istraživanjima o strukturi poljoprivrednih gospodarstava i o istraživanju o metodama poljoprivredne proizvodnje, a tiču se koeficijenata stočnih jedinica i definicija obilježja (Tekst značajan za EGP), SLUŽBENI LIST EUROPSKE UNIJE L 329/1, 15.12.2009.

28. Urosevic D., Gvozdenac D., Grkovic V., Calculation of the power loss coefficient of steam turbine as a part of the cogeneration plant, Energy, Vol. 59, pp. 642-651, 2013.

29. Wood fuels handbook, AIEL-Italian Agriforestry Energy Association, prevod na hrvatski - Priručnik o gorivima iz drvne biomase (proizvodnja - zahtjevi kvalitete – trgovina), Regionalna energetska agencija Sjeverozapadne Hrvatske, 2008.

30. Zakon o korištenju obnovljivih izvora energije i efikasne kogeneracije FBiH, Službene novine FBiH 70/13, 2013.

31. Bini R., Di Prima M., Guercio A., Organic Rankine Cycle (ORC) in biomass plant: an overview

on different applications, Turboden Company,

http://www.turboden.eu/en/public/downloads/10A02943_paper_marco.pdf