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IEE/09/933/SI2.558306

D2.5.4: Sector handbook of Working Group 4:

CHP (Combined Heat and Power) with solid biomass

WG Leader:

Austrian Biomass Association (ABA)

Christoph Pfemeter

Franz Josefs-Kai 13

A-1010 Wien

Tel.: +43-1-533 07 97-0

Fax: +43-1-533 07 97-90

E-Mail: office@biomasseverband.at

www.biomasseverband.at

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I. Introduction to market sector

Combined heat and power (CHP) or cogeneration is a technology used to improve energy efficiency

through the generation of heat and power in the same plant, generally using a gas turbine with heat

recovery. Heat delivered from CHP plants may be used for process or space-heating purposes in any

sector of economic activity including the residential sector. CHP thus reduces the need for additional

fuel combustion for the generation of heat and avoids the associated environmental impacts, such as

CO2 emissions. The project focus is on solid biomass CHP-plants with a minimum capacity of 500 kW

thermally (kWth).

In the past years the waste heat from electricity generation was very often not used, whereas the pure

electricity production was predominant. Meanwhile in many member states there is a minimum

utilization ratio for new plants. Plants without a thermal use are difficult to present economically due to

their overall energy yield. Another reason for the minimum efficiency criteria is the finite nature of the

resource biomass. CHP-plants should be operated mostly on a heat-controlled basis, only by that a

high overall efficiency can be reached and the biomass-fuel can be used in the best possible way.

Through the use of renewable energy sources, CHP plants show a higher CO2 saving potential and

they should be implanted mainly in a decentralized way due to their relatively low energy density of the

solid fuel.

The key technologies of the sector are combustion or gasification of solid biomass and generation of

power. For combustion there are several technologies available. In the power range of 0.5 until >100

MW mostly grate firing systems, fluidised bed combustion systems or jet blower firing systems are

used.

Grate firing systems

Grate firing systems are often offered in all power categories and dominate the market. Here the solid

fuel is transported to the grate via a mechanical device and it is transported further via forward and

backward movements of the grate elements. Apart from the travelling-, reciprocating- and stair-grates,

the advancing grate is the most used construction type for combustion of ligneous biomass. There are

no special requirements for the product pieces of solid fuel. At the beginning of the grate, the drying of

the fuel is taking place, in the middle part the gasification and in the end the complete combustion. At

the end of the grate follows the automatic ash removal. Based on these technologies, so-called cigar

burners and round baler firing for the combustion of straw-type biomass were developed.

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Fluidised bed combustion systems

This technology is suitable for very different fuel material and waste. Here it is highly necessary to

homogenize the fuel material before the combustion. The maximum size of pieces should be clearly

under 10 cm. Because of the elaborate pre-treatment of the fuel material compared to the grate firing

system, this technology is only used from a power class of 10 to 30 MW, which is then economically

applicable. With this technology, fuel material is whirled up through nozzles and is spread on the fluid-

bed. There is distinction between stationary and circulating fluidised bed combustion systems.

Jet blower firing

Jet blower firing is used for biomass where fuel material is available in very fine form. A classical field

of application is the timber processing industry, where fine chippings come up as residuals. The firings

are in principle also usable for straw-type biomass. However, this requires mostly a special processing

to dust. Jet blower firing for biomass are offered in a thermal power range from 500 kW th onwards to

up to 50 MWth. Jet blower firing for biomass combustion are mostly effected as cyclone- or muffle jet

blower furnaces.

Another key technology of CHP-plants is power generation. The two different technologies dominating

the market are on the one hand steam-process (from about 1 MW electric power) and on the other

hand the ORC-process (from about 0.2 MW electric power). The electrical efficiency is depending on

technology and capacity of the plant between 15 % and 35 %. The theoretical fuel efficiency of a

coupled generation of power and heat is however up to 90 %.

Steam process

The nowadays most spread technology of energy conversion is steam process. One of the big

disadvantages of steam process is the low electrical efficiency at low steam pressures or

temperatures. This means that high efficiency is normally only achieved in big and technically costly

plants. Precisely, small plants achieve electrical efficiency of 15 – 25 % (with pure power generation);

bigger plants (fuel thermal output of 20 MW) can reach efficiency of up to 35 %. The steam process

can either be used just for generating electricity or also for coupled power and heat generation. For

bigger plants and more variable demand of heat, mostly extraction-condensation turbines are used,

which allow the highest possible variation of relation of power and heat production. For smaller

systems or for a constant demand for heat, mostly steam backpressure turbines are used, where the

relation of power to heat generation remains constant. The steam turbine process can be operated

economically from up to an output of one MW of electrical efficiency.

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ORC (=Organic Rankine Cycle) process

For the ORC process an organic working fluid (e.g. silicon oil), which has a lower boiling point, is used

instead of water. The achievable steam parameter and with that the electrical efficiency are relatively

low (15 – 20 %). The ORC process is therefore mostly operated in a small power range at low

pressure and temperatures.

Wood gasification

For wood gasification biogenic solid fuel is transformed to flammable gas by using heat. The

advantages of gasification technology with downstream gas-motor are found in the high electrical

efficiency. Furthermore this technology can be combined with a downstream ORC process for energy

recovery, whereas unfavourable is the high plant complexity, also the costly gas cleaning, which is

necessary for the operation in gas motors and the bad partial load behaviour. High operating costs

and a low maturity of technology are also disadvantageous. In the past years some promising

demonstration facilities were build.

Technologies for biomass processing, heat exchanger and filter systems are further important plant

components of a CHP plant. Since every plant type demands different forms of components, they are

here not further described.

Working principle and integration in a biomass CHP plant

(source: BIOS BIOENERGIESYSTEME GmbH, Graz)

The working principle is according to the classical Clausius-Rankine-Process. High temperature, high

pressure steam is generated in the boiler and enters then the steam turbine. In the steam turbine, the

thermal energy of the steam is converted to mechanical work. Low-pressure steam exiting the turbine

enters the condenser shell and is condensed on the condenser tubes. As the steam is cooled to

condensate, the condensate is transported by the boiler feed-water system back to the boiler, where it

is used again.

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In Figure 1, a simplified flow sheet illustrating a typical biomass CHP plant based on an extraction condensing turbine process is shown

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The steam boiler consists of the evaporator unit, the super heater and the economiser, which are

usually arranged in a four-pass design. In addition, some manufacturers implement an additional

combustion air preheater in the flue gas downstream the economiser whereas others use steam or hot

water for combustion air preheating.

The feed water of the water steam cycle is heated in the feed water economiser which is installed

downstream the super heater, to a temperature close to the boiling point. The feed water economiser

is the first of three possible heat recovery units (the others are combustion air preheater and

condensate preheater) downstream the super heater.

In the combustion chamber, the chemically bounded energy of the fuel is released and transferred via

boiler and surface of the heat exchangers to the water steam cycle. The heated water is evaporated in

the boiler evaporator and collected in the steam drum. Usually the vertically arranged evaporator tubes

also constitute the upper part of the combustion chamber walls. The steam drum is located outside the

flue gas flow. From the steam drum the saturated steam is transferred to the super heater. The super

heater uses flue-gas at a high temperature level to produce superheated steam. Attention should be

paid to high temperature corrosion mechanisms, which may require the implementation of a protective

evaporator prior to the super heater in order to control the flue gas temperature.

After the boiler multi-cyclones and electrostatic precipitators or fabric filters are commonly used to

remove dust from the flue-gas. Superheated steam at high pressure and high temperature is ducted

via pipes to the steam turbine where it is consumed and depressurised. At the extraction condensing

turbine steam is extracted from the turbine at a pressure state, which is predetermined by the heat

consumers. The main part of this extracted pressure steam goes to the heating condenser and a

smaller part is used to transfer heat to the feed-water. The rest of the steam expands in the low-

pressure part of the turbine to the condenser pressure state and is then cooled at constant pressure.

Depending on the conditions on site, dry air-cooled condensers or water-cooled condensers are

installed.

In general the turbo generator unit includes the module

Steam turbine

Gearbox/generator unit

Lubricating oil system

Control oil system

Measuring and control system

De-ionised water is used for the water steam circuit in order to keep an undisturbed operation. In the

water treatment unit solved and dissolved impurities of the natural water must be removed. Losses in

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the water-steam circuit caused by blow down and sampling are replenished by de-ionised water from

the feed water treatment unit.

The technology addressed and definition of the scope of CHP with solid biomass

Not only grate firing systems and fluidised bed combustion but also jet blower firing are technically well

engineered and introduced to the market. The same applies to the steam- and ORC-process for power

generation. The wood gasification is technically the least perfected technology, however it will gain

importance in future.

Typical markets for our technology

Fig. 2 shows the aims of the EU member states of total contribution of RES (installed capacity

generation) expected in the electricity sector in 2020 (GWh):

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Taking a closer look to the national action plans for renewable energies, it is getting evident that in

whole Europe the expansion of power generation out of biomass is targeted. Bioelectricity is expected

to represent 19,5% of all renewable electricity in 2020 and it is expected to increase by 116 TWh

between 2010 and 2020. On average 70% of bioelectricity should be produced from solid biomass.

The generation of power from solid biomass should be raised from now 76,706 GWh in 2010 up to

159,556 GwH in 2020, which equals a doubling. The expansion should take place in all EU member

states.

Bioelectricity is expected to represent 19,5 % of all renewable electricity in 2020 and it is expected to

increase by 116 TWh between 2010 and 2020.

Fig. 3: Estimation of total contribution of RES (installed capacity, gross electricity generation) expected

in electricity sector in 2020 (GWh) (source: 2011 AEBIOM Annual Statistical Report)

Economic operators addressed and target group of CHP with solid biomass

With the implementation of a CHP-project various companies are involved. After the investment

decision the first step is the call for projects proposals. Financial investors, private companies, energy

supplier and municipalities usually commission the projects. For the call for project proposals usually

planning companies are responsible. The orders are normally assigned to general contractors. Usual

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practice is the division of the order of several lots (for example into a structural and technical part).

Some equipment manufacturers also act as general contractor and/ore planning companies. This

Working Group focuses on following target Groups:

1. Planning companies

2. General contractors

3. Installation companies

4. Financial service providers / investors

5. Technology suppliers

5.1 Manufacturers of boilers and combustions plants

5.2 Turbine producers

5.3 Raw material supplies and processing

II. Characterisation of market sector

Due to the high investment costs of biomass CHP plants in the efficiency range of over 500 kW-

electric, the plant operators are mostly energy utilities or industrial enterprises, that use residual wood,

arising during operation processes. Furthermore big forest enterprises are appearing as operators of

CHP plants. Due to the high financing requirements also some financial service providers, acting as

project developer and equity investors, have specialised on financing of bio energy projects in the

frame of biomass funds and have shareholdings for plants. Meanwhile there are a lot of companies

that have specialised on the generation of green power and are operating several plants.

Functioning of markets in general

Some significant required framework conditions for biomass CHP plants are reasonably defined feed-

in tariffs for electricity, which are ensuring an economic operation of such a plant, an ensured fuel

supply as well as a usage of the produced heat as complete as possible. In this context, the annual

utilisation rate (= sum of generated power + usable heat p.a. / used fuel energy p.a. with regard to Hu

of big biomass CHP plants) should be at least over 60 %; whereas with heat controlled operation, over

80 % is possible.

For biomass CHP large-scale plants a secured fuel supply is crucial. Because of the low energy

density in comparison to fossil fuels, the lengths of the transport ways are economically limited. And

that in turn requires a certain reasonable size of CHP plants for a certain region resp. for a business.

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There can be exceptions like plants that are operated on the basis of pellets and which are

implemented at logistically favourable places (along coastline or at waterways). It is further on

important to ensure the fuel material for the operation of the plant by contract, concerning both

quantities and price.

The basic requirements for a successful development of CHP technologies on the basis of renewable

energies in the future is the legislative guarantee for sufficiently high feed-in tariffs over an ensured

period of time (at least 10 years). These framework conditions should be ensured for an adequate

period of time. Only then developments, demonstrations and market introduction for new technologies

can be implemented.

Feedstock used for CHP with solid biomass

Pellets

Wood pellets are mostly produced from sawdust and wood shavings compressed under high pressure

using no glue or other additives. They are cylindrical in shape and usually 6-10 mm in diameter. The

average length is about 10-30 mm. Furthermore, due to their high energy content they have

convenient delivery and storage features. The following picture shows pellets with flames:

Picture Nr. 1: burning pellets (source: Austrian Biomass Association)

Wood Chips

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Wood chips are either produced as by-products from saw mills and other timber processing industries

or from logs coming directly from the forests; in the latter case their price is higher. Quality wood chips

can only be produced from optimal raw material with a minimum diameter of five centimetres. The

bigger the plant, the more insensitive they are in case of applying minor quality of wood chips with a

high part of bark or impurities.

The following picture shows wood chips in their raw form:

Picture Nr. 2: wood chips (source: Austrian Biomass Association)

Residues and waste products from the wood industry

Besides the processed wood products, pellets and wood chips, also side and waste products from the

timber processing industry can be used energetically without treating them beforehand. As an example

can be mentioned sawdust, wood dust, pressings, sawed-off wood and bark.

Other solid biomass

Depending on the plant systems engineering and the legislative framework, different solid biomass

can be used energetically. Here can be mentioned straw, olive pits, corncobs, pruning or such like.

III. Criteria and indicators for market attractiveness

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Overview on categories, criteria and indicators in form of a clear list

a) Institutional Framework conditions

b) Political ecological framework conditions

c) Feedstock markets and feedstock potentials

d) Production and environmental criteria

e) Energy markets

Ad a) Institutional Framework conditions

In the 27 EU member states the political intention for the expansion of renewable energy can be

distinctively different, which shows in the interpretation of the framework. The crucial question is how

much do the political decision makers support the examined market sector and if there is a correlation

of the political will and market opportunities. It is examined whether a declaration for renewable energy

helps to improve market conditions or whether a decreased political support reinforces the risk.

Ad b) Political ecological framework conditions

It is rather difficult to quantify certain typical risks, which are accompanied with investments in foreign

markets, e.g. risks connected with the situation of the current financial market or those risks, which are

connected with political decisions. In order to be able to assess the risk involved, certain political

information is required.

Ad c) Feedstock markets and feedstock potentials

In the bio energy sector the long-term availability of biomass as well as the associated costs are

crucial. This can be applied especially for the evaluation of the attractiveness of foreign markets.

Under this point it is necessary to indicate which kind of biomass is relevant for our sector and which

core size for the evaluation of the potentials are used. Another criteria here is to estimate the future

potential of biomass and to put this potential into numbers. The value for the EU 27 member states is

in total for 2006: 60,094 Ktoe; for 2015 an estimation of 65,088 Ktoe and for 2020 an estimated total of

72,692 Ktoe of biomass from forestry

Biomass supply

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By 2020 the biomass supply in Europe should increase to meet the demand of all sectors of heat,

electricity and transport bio fuels, rising from around 84 Mtoe in 2006 to around 129 Mtoe in 2020.

Forest and forest based industries are contributing the most to the biomass supply, and this should still

be the case in 2020 (more than 53 % of biomass supply), however the biggest increase should come

from agriculture. Both increases show that the potential for the further development of bio energy in

Europe is big.

Figure 3: Estimated biomass from forestry domestic supply in 2006, 2015 and 2020 [ktoe]

Ad d) Production and environmental criteria

Despite European legal framework and an internal market, the environmental requirements in the EU

member states can vary considerably and thus can influence the free movement of goods

considerably. This is shown, e.g. in higher emission regulations, which can’t be met with available

technology or be it the different speed of implementation in the EU member states of European

legislative framework. All this has to be considered in the environmental criteria and production.

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Ad e) Energy markets

The basic conditions in the energy market are a crucial factor to survive as a new energy producer.

Especially the access to energy networks, possible discriminations of new energy suppliers and the

structure of the energy sector are the factors to examine closer, rather than the market size or the

perspectives of expansion.

IV. Total list of considered criteria and indicators for CHP-technology with solid biomass

1. Institutional framework conditions

1.1. Criterion: Is the political intention to the extension of the according market sector visible?

1.1.1. Indicator: Growth according to the National Renewable Energy Action Plan (NREAP) in the

field of renewable energy: Percentage change of the energy demand in the target country of

renewable energy from 2010 to 2020?

1.1.2. Indicator: Growth according to the National Renewable Energy Action Plan (NREAP) in the

field of renewable total final energy consumption (tfec) on solid biomass in the sector of heating and

cooling from 2010 to 2020?

1.1.3. Indicator: Growth according to the National Renewable Energy Action Plan (NREAP) in the

field of renewable total final energy consumption (tfec) on solid biomass in the sector of electricity from

2010 to 2020?

1.1.4. Indicator: Percentage part of the power generation, according to the National Renewable

Energy Action Plan (NREAP), from CHP plants in relation to the total power generation on solid

biomass for the year 2020.

1.2. Criterion: Are the political framework conditions reliable and steady?

1.2.1. Indicator: How have the important framework conditions for investments in CHP projects

changed in the previous 2 years?

1.2.2. Indicator: Will the framework conditions for CHP projects be changed significantly in the near

future (next 2 years)?

1.3. Criterion: The licensing procedure is temporally appropriate?

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1.3.1. Indicator: How long does an average licensing procedure for CHP projects take in the target

country (Only the duration of the permission by the authority; finished plan of the plant and without

negotiations of feed-in tariffs)?

2. Political ecological framework conditions

2.1. Criterion: Regulatory tool were successfully integrated in the target country?

2.1.1. Indicator: Have the targets of the National Renewable Energy Action Plan (NREAP) in the field

of CHP of solid biomass been adopted in the national legislation?

2.2. Criterion: Financial subsidies can be retrieved in the target country.

2.2.1. Indicator: In what amount, investment subsidies for CHP projects based on solid biomass can

be retrieved?

2.2.2. Indicator: What is the maximum investment permit in €/kW bottleneck capacity for new CHP-

plants?

2.2.3. Indicator: In what amount may the legally guaranteed feed-in tariffs for electricity of CHP

projects based on solid biomass can be used?

2.2.4. Indicator: How long is the duration of subsidized feed-in tariffs?

2.2.5. Indicator: What is the maximum of the binding defined delivery systems for green power plants

in relation to the population (€/head)?

2.2.6. Indicator: For how many full-load hours is the maximum level of subsidies in CHP plants

based on solid biomass limited.

3. Feedstock markets and feedstock potentials

3.1. Criterion: The biomass potential is big enough to realize CHP projects?

3.1.1. Indicator: How big should be the increase (according to the National Renewable Energy Action

Plan - NREAPs) of the estimated availability (per capita) of wooden biomass of forestry from 2006 to

2020, in relation to the inhabitants?

3.1.2. Indicator: To what extent will the domestic availability of wooden biomass of forestry change of

the year 2006 to 2020 (in %)?

3.1.3. Indicator: How much is the average fuel proportional to the average feed-in tariff in percentage

in the year 2010?

3.1.4. Indicator: How much was the average fuel for solid biomass in €/MWh in 2010?

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3.1.5. Indicator: How much was the average feed-in tariffs in €/MWh for CHP plants in the year

2010?

4. Production and environmental criteria

4.1. Criterion: Required emission limits can be fulfilled with the technology.

4.1.1. Indicator: Required emission limits for heating systems based on solid biomass can be fulfilled

for dust (in mg/Nm3).

4.1.2. Indicator: Required emission limits for heating systems based on solid biomass can be fulfilled

for CO (in mg/Nm3).

4.1.3. Indicator: Required emission limits for heating systems based on solid biomass can be fulfilled

for NOX (in mg/Nm3).

4.1.4. Indicator: Required emission limits for heating systems based on solid biomass can be fulfilled

for Org. C (in mg/Nm3).

4.2. Criterion: Are criteria for efficiency required?

4.2.1. Indicator: What is the value of the fuel efficiency in CHP plants based on solid biomass to get

the subsidized feed-in tariffs?

4.3. Criterion: Costs of residue disposal

4.3.1. Indicator: How much is the disposal of the ash (pure landfill costs, excluding transportation,

excluding analysis costs for ash)?

5. Energy markets

5.1. Criterion: Is an access to the grid ensured?

5.1.1. Indicator: Are there priority rules for renewable energy in the electricity sector?

5.2. Criterion: Is an access to the heating grid ensured?

5.2.1. Indicator: Are there priority rules for renewable energy in the heating sector?

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List of references:

“2011 Annual Statistical Report on the contribution of Biomass to the Energy System in the EU27”,

AEBIOM – European Biomass Association

Biomass cogeneration plants, Umweltbundesamt, Austria

“Strom aus fester Biomasse – Stand der Technik und künftige Entwicklungen”, I. Obernberger et al.,

2005; BIOS BIOENERGIESYSTEME GmbH Graz, Austria

www.bios-bioenergy.at/en/electricity-from-biomass/steam-turbine.html

Figures and Graphical material

Fig. 1: Working principle and integration in a biomass CHP plant; source: BIOS

BIOENERGIESYSTEME GmbH, Graz

Fig. 2: “2011 Annual Statistical Report on the contribution of Biomass to the Energy System in the

EU27”, AEBIOM – European Biomass Association

Fig. 3: “2011 Annual Statistical Report on the contribution of Biomass to the Energy System in the

EU27”, AEBIOM – European Biomass Association

Picture Nr. 1: Burning Pellets; source: Austrian Biomass Association (ABA)

Picture Nr. 2: Wood Chips; source: Austrian Biomass Association (ABA)