Exergy as measure of sustainability of energykgh-kongres.rs/images/2016/doc/ppt/06-Novak.pdfExergy as measure of sustainability of energy system Prof.dr. Peter Novak Hon. Mb.: IIR,

Exergy as measure of sustainability of energy

systemProf.dr. Peter Novak Hon. Mb.: IIR, ASHRAE, REHVA, KGH, SITHOK, SLOSE, Profesor Emeritus FTSVice Chairmen of Scientific Council of EEA, 2012-2016Ljubljana, [email protected]

47. Međunarodni kongres i izložba o KGH, Beograd, 30.11–2.12.201647th International HVAC&R Congress and Exhibition, Belgrade, Nov.30–Dec.2 2016

1

mailto:[email protected]

EKSERGIJA KAO FIZIČKA MERA ODRŽIVOSTI ENERGETSKOG SISTEMA

Peter NOVAK, SlovenijaHon. Mb.: IIR, ASHRAE, REHVA, KGH, SITHOK, SLOSE, Profesor Emeritus FTSVice Chairmen of Scientific Council of EEA, 2012-2016Ljubljana, [email protected]


mailto:[email protected]

As Bertrand Piccard said upon the final landing in Abu Dhabi “If an airplane can fly around the world without a drop fuel, clean technologies can undoubtedly be implemented on the ground to make a cleaner, more efficient and richer world.”


Why exergy, why sustainable energy system?

47. Međunarodni kongres i izložba o KGH, Beograd, 30.11–2.12.2016 47th International HVAC&R Congress and Exhibition, Belgrade, Nov.30–Dec.2 2016

4

Is the world environment in danger?Is our population in danger?How big is the ecological footprint?Are the human development index (HDI) and ecological footprint (EFP) gut indicators for incoming problems, like: • uneven distribution of gods, • migrations, • globalisation, • liberalisation

World ecological footprint


5

Only contries in green to grey colors have lower ecological footprint as there biocapacity

Countries on the Planet in pink to red are owerusin the biocapacity of there land.

Ecological footprint in gha in world and some countries


6

1,7

2,8

2,8/1,7 = 1,65

2,7/1,3 = 2,1

Ecological footprint in some coutries after economic and social changes


7

3,9/2,8 = 1,39

5,8/2,4 = 2,0

HDI Index and EF: case Slovenia, Croatia and Serbia


8

On one side the some countries are using more than biocapacity of the country is, one the other side the global warming will have the most negative influence on the population in les developed world.

Great economic, social and changes in technologies are requested from all of us.

› Out of consumer society

› Introduction of „Circular economy“

› Sustainable energy system without GHG emission› More even distribution of good on the world

› ............................


9

Sustainable energy system - SES Sustainable energy system main characteristics:Nature friendly,User friendlyWithout harmful emissions, Based on renewable energy sources,Conversion technologies with a lowest possible

irreversibility's – exergy efficient


10

SES and Energy Union package in EUIn Energy Union document is one of most important statement:

“To reach our goal, we have to move away from an economy driven by fossil fuels, an economy where energy is based on a centralized, supply-side approach and which relies on old technologies and outdated business models.”

› Nuclear is „centralized“ .....? Is no future for nuclear !!!› Renewable energy sources: decentralized, new bussines

models, new technologies, no emmissions!


11

SES and „Circular economy“ in EU

Circular Economy (CE) basic statements (interalia): › “…is an essential contribution to the EU's efforts to develop

a sustainable, low carbon (?), resource efficient and competitive economy….“,

› „… ties in closely with key EU priorities, including jobs and growth, the investment agenda, climate and energy, the social agenda and industrial innovation, and with global efforts on sustainable development“


12

EU strategy on Heating and CoolingCOM(216)51 final 16.2.2016

› PE for heating and cooling: 75% fossil, 25% low carbon fuels

› Buldings must be decarbonized

› Industry waste heat shuold by used nerby for H&C of buildings

› Financing is the problem

› New BAT classes for space heater (A+++ only for RE)

› DHC, CHP, Smart buildings,

› Promoting RE – including HP with renewable electricity

› Inovation


13

Resource accounting and exergy

› Resource “consumption and/or depletion” can‘t be evaluated only according to mass and energy balance, because they not disappear.

› Even in scientific comunities is normal to use: consumption of energy, water, steel, aluminum, etc. This not in acordance with two basic law of physic: conservation of mas and energy.

› Using the exergy as measure of resource depletion we can evaluate quality of our processes taking into account the conservation of mass and energy and irreversibilities in energy conversion processe


14

Circular economy and exergy (reversibilities)

› Circular economy is a policy to minimize the use of resources, to minimize the thermodynamics irreversibility’s, this mean to promote higher exergy efficiency.

› To push the circular economy on the top of society development we need a serious exergy analysis of present technologies and economic patterns.

› Sustainable development means les exergy destruction or depletion in all circumstances.


15

More questions as answers!

› What kind of sustainable energy system should be in a circular economy?

› What should be a “sustainable development” in the case of energy supply, distribution and use?

› How we can measure the sustainability of energy system?

› Is exergy approach the best indicator for measure thesustainability of energy system?


16

Exergy

Definition (for memory):› “Exergy of a system in a certain environment is the amount of

mechanical work that can be maximally extracted from the system in this environment” (Rant, 1955 et all)

› Energy W is a sum of exergy E and anergy A (~ energy of environment)

W = E + A› Exergy is a measure of quality of energy. › Energy is always conserved and can neither be produced nor

consumed. › Exergy can be very easily destructed and converted in anergy

trough irreversibility’s in the conversion processes.


17

Energy conversion and exergy efficiency› In real energy conversion processes we always have a destruction

of exergy because of irreversibility‘s. › This mean that in closed system energy can be balanced but

exergy not. › Exergy destruction or „exergy vanishing“ is natural phenomena

which can be to some extent controlled by design of our energy conversion equipment.

› Exergy efficiency is therefore a measure of processes quality.› Quotient between output exergy Eout and input exergy Ein is

standard definition of exergy efficiency.ηex = Eout/Ein


18

Exergy efficiency and exergy analysis

› Exergy efficiency can be very easy calculate using standard data for exergy content in different energy carriers and embedded exergy in materials used.

› In general exergy efficiencies are always a measure of the approach to the ideal.

› Exergy analysis identifies the margin available to design more efficient energy systems by reducing inefficiencies (irreversibility's).

› Exergy analysis is a methodology that uses the conservation of energy principle (embodied in the first law of thermodynamics) together with non-conservation of entropy principle (embodied in the second law) for the analysis, design and improvement of energy and other systems.

› It is used to clearly indicate the locations of exergy degradation in a process that may lead to improved technology or operation.


19

Life Cycle Exergy Analysis

› LCEA (Life Cycle Exergy Analysis) can be used as a method to quantify depletion of natural resources and to assess the efficiency of natural resource used.

› It can be used for energy system with fossil and renewable sources of energy, for different materials and in broader sense for societies.

In our case LCEA will be used with EROI as sustainabilitiy indicator of SES, based on „organic carbon circulation“ in future circular economy.


20

Priciples of LCEA› Natural resources are classified as

– natural flows and – stocks.

› Stocks are then divided into – deposits (dead stocks) and – funds (living stocks).

› Natural flows and funds are renewable while deposits are non‐renewable.

› All in‐ and outflows during the life cycle of production, use and disposal or recycling, are then considered as exergy power over time.

› The direct exergy input (e.g. solar, water, wind) of renewable sources can be disregarded in LCEA since they represent a natural flow and are therefore renewable.

› If not used natural exergy flows will be wasted and lost.


21

Source: Davidsson, LCEA of Wind Generator, 2011

Natural exergy flows


22


LCEA


23

• The life cycle exergy analysis of a system usually consists of three separate stages with different exergy flows at:- construction phase,- operational phase and- clean up (decommissioning, recycling) phase.

• The exergy used for construction combined with the exergy used for maintenance and clean up make up the total input exergy.

• A fossil fuels power plant takes the exergy from the fuels used during the operational phase. The exergy of the output electricity will always be lower than the exergy of the fuels used during the production.

• A power plant using fossil fuels can therefore never be sustainablesince it uses more exergy than it generates.

Example of exergy flow diagram for LCEA of a power plant using non‐renewable fuels

The exergy of the output electricity will always be lower than the exergy of the fuels used during the production. A power plant using fossil fuels can therefore never besustainable since it uses more exergy than it generates.


24

A fossil fuels power plant takes the exergy from the fuels used during the operational phase.


Exergy flow diagram for LCEA of a renewable energy power plant


25

Power plant using the renewable energy sources for production of electricity, on the other hand, convert the renewable exergy of a natural flow to a useable form of energy. During the operational phase it will hopefully produce more exergy than the indirect exergy needed during the life cycle.


EPBT and EROI

› LCEA method enable us also to analyze the influence of intermittency of RES taking into account the power factor CP and capacity factor CF by producing heat and electricity.

› Conversion and use of the exergy in fuells and RES is usually presented either as exergy payback time (EPBT) or exergy return on exergy investet (EROI).

› It is also common in some analysis to present a CO2 payback time.


26

EPBT and EROI definition


27

Exergy balance


28

Exergy from solar radiation


29

Exergy from solar radiation

For South European region (latitude 37 to 47°) we can use the relation for exergy from solar energy on the surface level ηex developed from Neri:

ηex,S = 0,820 + 1,76.10-5. (Etot – 4500)Where:Etot = ED + Ed [MJ/m2/year] is sum of yearly direct (D) and diffuse (d)

radiation that reaches a horizontal surface on analyzed location. Equation is valid for Etot = 4500 to 7000 MJ/m2/year.Wind and water flow are the secondary and wave are tertiary exergy form of solar irradiation. The available exergy of them is time and location depended and calculation can be done only on the basis of measured data in given period of time, normal more than 2 typical meteorological years.


30

Sustainable energy conceptSustainable energy system (SES) as proposed consists of the three main renewable exergy (energy) carriers, needed in any settlement:

– renewable electricity,– gas (synthesized methane CH4; s-methane), – liquid (synthesized methanol CH3OH; s-methanol) and as fourth

– solid fuels from biomass (less important in developed countries). The methane and methanol will be used as chemical storage of RES and are the only exergy carriers in nature with one carbon chemically connected with four hydrogen’s. Necessary hydrogen and oxygen will be produced with solar electrolysis of water and the carbon in biomass will be used embeded in by photosyntesis.


31


32

2 main exergy sources:• solar irradiation and• planetary energy

4 secondary exergy carriers5 conversion technologies3 main final exergy carriers:

1. Electricity2. Methane CH4 (gaseous fuel)3. Methanol CH3(OH) (liquid

fuel)4. Solid fuel –wood(?)5. Dimethyl ether CH3OCH3

(liquid fuel)Dimethyl ether can be a transition fuel for diesel engines)Sources: For synthetic methane:

Hydrogen – water electrolysisCarbon: from waste biomassFor methanol: biomassoxygen – w. electro.; wasted

CO2

Sourse: (PN,1989,2002,2015)

SUSTAINABLE ENERGY SYSTEM CONSISTS ONLY FROM :

Storage and SES

› S-methane and s-methanol represent the chemical storage of solar exergy (like do the nature with photosysnthesis in biomass) with efficiency close to the storage of atmospheric carbon in biomass.

› Each country needs a mix of exergy carriers from fossil or RES.

› Sustainable energy system (SES) have to produce required sustainable exergy carriers in sufficient quantity with regard the time and location.


33

Natural CO2 cycle In this way, natural circle of carbon dioxide and water is closed and there is no additional emission of GHG. Proposed SES has no GHG emissions, because CO2 and water are recycled in natural photosynthesis process and vapor cycle.


34

(Source: Olah et al., J. ACS, jul 2011)

Characteristics of sustainable (renewable) energy system - SES

To fulfil the daily energy needs the sustainable energy system has to response to the following six main requirements:

1. Source of exergy must be inexhaustible, available everywhere on the planet;2. Zero emission of GHG by burning the new fuels;3. Available on any place and any time (in all present forms of energy: solid,

liquid, gaseous fuels and electricity);4. Must be compatible with existing infrastructure with minor adaptation;5. In transition period the present energy system and SES has to work in

parallel with no interference (coexistence of two system);6. Should be competitive with fossil fuels system if all external environmental

costs will be included in their exergy carriers’ price


35

How the proposed SES comply with the requirement?1. Primary exergy sources (solar energy, planetary energy);2. No emission of GHG;3. Proposed four energy carriers can be used any time in any place;4. For proposed system we don’t need a new infrastructure5. All energy carriers can coexist with the present energy system6. Should be competitive: According to IMF report (January 2013), the

world fossil fuel pre-taxsubsidies in 2013 have been $480 billion/y and post-tax subsidies $1.9 trillion/y. Including the $1.4 trillion/y environmental damages,total direct and indirect costs, not included in the price of fossil fuels used are $2.78 trillion/y.Including this subsidies in the final price of fossil fuels, competitiveness of RE will be out of question.


36

Carbon recycling society

› Proposed SES is not totally new, but enables smooth transition to a new sustainable “carbon recycling society”,

› “Low carbon society” is impossible in the nature, it can stay as political action.

› SES is sustainable part of promoted “circular economy”. › Costs of all form of exergy will be in begining of transition period

higher, but at the end of transformation of present energy system to SES will be small and stable for ever with a minor or no impact on the climate of the planet.


37

Exergy as measure of sustainability of SES

In the SES the technologies for production solar electricity and proposed energy carriers are:› Hydro power plant› Wind generator system› Biomass supply› PV systems› Hydrogen production› Synthesis of methane› Synthesis of methanolFor some of this technologies the EROI is presented in scientific literature, for some new technologies the data are not sufficientlly verified to be able to prepare final results (maintenance and dissemble or recycling data are missing).For most technologies the data for EPBT are available.


38

EPBT and new technlogies

› EPBT is changing with the time.

› For fossil fuels EPBT is growing with time because of growing cost od production,

› EPBT for RES conversions technologies is falling very fast: – wind generator, depend on rotor diameter the EPBT is 0,25 to 0,5 years.– PV system 0,2 to 1,4 years– Small Hydro: 0,5 to 1year (site depended)– Hydrogen production: High pressure electrolysis: 54 kWh/kg H2;– Power to gas efficiency : ~39% – Biomass → Syngas (CO, CO2, H2) → CH3OH efficiency depend of costs

of electrolysis


39

Resource in TW =TWh/8760 h/y

TWideal

TWTechnical possible

TWPresent delivery

as electricitySolar irradiation 11500 580 ÷ 1640 0,00176

Wind 1700 40 ÷ 170 0,02Water flows 1,9 1,6 ÷1,9 0,32

Waves 2,7 0,5 ÷ 2,7 0,000002Geothermal- shallow 45 0,07 ÷ 0,2 0,0065

Geothermal - deep 55 0,035 ÷ 2 0,0065

Tidal 3,7 0,02 ÷ 0,8 0,00006Biomass (dry) 33,4 5,8 ÷11,7 0,039

Total 13.341,7 628,025 ÷ 1829,3 0,387322

Present needs of TPES (2013)

17,79 2,59 (14,6%)


40

Renewable exergy (energy) resources on the Planet Earth with present conversiontechnologies in electricity

Energy and exergy efficiency for selected electrical devices

Device Energy efficiency % Exergy efficiency %GenerationCoal fired power plant 40 ÷ 64 38 ÷ 62Nuclear power plant 30 28Hydro power plant 90 90Wind turbine 0,475 ÷ 0,576 0,475 ÷ 0,576PV system 6 ÷ 25 6 ÷ 25Solar thermal 10 ÷ 30 8 ÷ 25Co –, trigeneration systemCogeneration 74 31Trigeneration 94 28Resistance space heater ~ 100 6Hot water heater 90 10Heat pump* 380 *COP = 3,8 19


41

Present available data for EROI of some technologies used in SES

Exergy conversion technology

EROI - LOW EROI - HIGH COMMENTS

PV 3 6 (28)* *EPBT 0,2

WIND 18 (offshore) 34÷ 18 (onshore) Cf ~ 0,35 ÷0,19

HYDRO RESERVOIR 205 280 Long life time

HYDRO RUN OF 170 267 Long life time

BIOMASS WASTE 27 27

Solar Hydrogen 1,5 5,0 estimated

S - Methane 1,5 5,0 estimated

S- Methanol 2,0 5,0 estimated


42

All propsed technologies used in SES have a EROI more than 1, therefore are all sustainable.

Conclusions› World is fassing with real climate treat!› Exergy efficiency and EROI are good indicators of energy conversion processes.› Proposed SES can replace the present system with further development of chemistry

for biomass conversion in methane and methanol.› Final EROI calculation for hydrogen, methane and methanol will be possible after the

technologies became mature.› Disadvantages of methanol fuel, can by replaced with further conversion in dimethyl

ether. › Gasification of the biomass and conversion in liquid fuels need further optimization,

to improve significantly the exergy efficiency of the process from land to fuel.› Present conversion efficiency from solar irradiation - sugarcane to bioethanol is under

0,032% in comparison to PV system efficiency of ~16%. Use of biomass for direct conversion in biofuel has to carrefully investigated.

› Time for transition is 35 years and is enough to achieve our final goals.


43

We have to return back to the sun.


44

With sunflower before Fukushima

Using circular economy with carbon recycling, but

Not with Sunflower after Fukushima

Thanks for attention, Questions are welcoming !

Documents

Exergy as measure of sustainability of energykgh-kongres.rs/images/2016/doc/ppt/06-Novak.pdfExergy as measure of sustainability of energy system Prof.dr. Peter Novak Hon. Mb.: IIR,