Energy Center Advanced integrated systems and design methods for improved energy efficiency World Future Energy Forum 2016, Beijing h"p://powersave1200.tumblr.com/ Prof Daniel Favrat Prof. emeritus daniel.favrat@epfl.ch 1
Energy, population, environment (historical evolution) CO 2 [ppm] 390 370 350 Pop. [billion hab.] 7 6 5 World population World primary energy 2013: 400 [ppm] https://www.google.ch/search?q=%c3%a9volution+population+%c3%a9nergie+co2&client=firefox-a&hs=aym&rls=org.mozilla:enconsumption US:official&channel=np&tbm=isch&imgil=YDNIUH-bNONiGM%253A%253Bhttps%253A%252F%252Fencrypted-tbn0.gstatic.com %252Fimages%253Fq%253Dtbn%253AANd9GcSti7OLA0pj7UXbkKnQdAvn2uivhQ2Nr5Gh5p8Z6IHNN5uGFeWk %253B580%253B376%253B1XM5pdun7gzYfM%253Bhttp%25253A%25252F%25252Fpoldev.revues.org %25252F687&source=iu&usg= ZhYPNoZ9BdEQ2HizhjOh3KnRa3Y Mean CO %3D&sa=X&ei=YEyGU9H7DaSd0AW-2IGAAg&ved=0CGEQ9QEwCQ#facrc=_&imgdii=_&imgrc=IfUT_IAR969EtM%253A%3BgDDb- 2 concentration in atmosphere FgjCqgIQM%3Bhttp%253A%252F%252Fstock.wikimini.org%252Fw%252Fimages%252F7%252F7b%252FR %2525C3%2525A9chauffement_climatique-temp%2525C3%2525A9rature-co2.png%3Bhttp%253A%252F%252Ffr.wikimini.org %252Fwiki%252FD%2525C3%2525A9veloppement_durable%3B1200%3B644 Energy [10 9 tep] 10 8 330 4 6 310 3 4 290 2 270 1 2 250 0 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 0 Years 2
Technological innovation objective: less degradation Physics: conservation of mass and energy But: driving forces result from unbalances (of exergy levels, of concentration in materials and fluids...) transformation Nature is a story of degradation: Input (mass / energy) Output (mass / energy) by degrading high exergy value from the Sun, Earth is able to The confusion about the meaning of «energy»: Greek word energeia generate vegetation and ultimately fuels, food for animals and humans (containing work) Degradation is part of life, but 3
Technological innovation objective: less degradation would be sustainable if the tremendous potential of the Sun- Earth exergy unbalance would be used properly to: satisfy energy services recycle materials and wastes clean or desalinate water h"p://chandra.harvard.edu/edu/formal/ems/ems_earthmoon.html 4
Energy efficiency: best way to reduce CO 2 emissions Gt CO 2 45 40 550 Policy scenario CCS 35 450 Policy scenario Nuclear Renewables Energy efficiency 30 25 20 2005 2010 2015 2020 2025 2030 From IEA outlook 2009 5
Energy services Heat (from high temperature energy Mechanical energy (pumping, compression, transport ) processes in industry to low temperature heating in building) Cold (from air conditioning to refrigeration, freezing and cryogenic processes) Electricity (previous services + cooking, lighting, computing, telecommunication, etc.) 6
World fuel shares of CO 2 emissions 1973 2012 Nat. gas 14.4% Other 0.0% Coal 35.0% Other Nat. gas 0.5% 20.3% Coal 43.9% Oil 50.6% Oil 25.3% 15 633 Mt CO 2 31 734 Mt CO 2 From IEA outlook 2014 7
Relative CO 2 emissions per unit of energy of main fuels 2.5 2.0 1.5 1.0 0.5 0.0 8
From primary energy to electricity Geotherm. Nuclear Fossil Biomass Wind Hydro Solar Primary energy Nuclear energy Radioactive decay Fission Chemical energy Kinetic energy Potent. energy Solar Irradiation Thermal Energy Reactor Heat Exch. Combust. Collectors Mechanical Energy Compressible flow turbine or engine Wind turbine Hydr. turbine Compress. flow turbine or engine Electricity Electrical generator Fuel PV cells Electrical generator PV cells Favrat D. et al. The information platform energyscope.ch on energy transition scenarios, Proceedings of ECOS 2016, Portoroz Slovenia. 9
Three main action paths towards energy efficiency Develop better indicators for ecoefficiency and sustainability (exergy efficiency, renewable energy ratio,...) Develop improved design and planning methods (holistic, able to optimize complex integrated systems towards increased efficiency, ) Develop advanced technologies for a more rational use of both non h"p://solex-un.ru/energo/formaty-energomarkirovok / h"p://www.purepropertycare.co.uk/commercial-services/insuladon/ renewable and renewable 10
Example: combustion and heating Use of open fire for heating and cooking discovered more than 400 000 years ago Use of fire: > 400 000 years ago Today s heating systems are still mostly boilers The energy efficiency of boilers is close to 100% (sometimes improperly claimed to be > 100% in the literature!) Can this however really be considered as a 21 st century technology? FAVRAT D., MARECHAL F., EPELLY O. The challenge of introducing an exergy indicator in a local law on energy. Energy,33, No2, pp130-136 (2008) 11
Better alternative for heating with the same types of fuel 1.0 Combined cycle 0.6x4.5=2,7 0.6x4.5+0.3=3.0 Oil or (bio-)gas 1.0 0.6 (electricity) 0.3 (heat) 0.6 2.1 Electrical heat pump (COP:4.5) Hybrid fuel cell SOFC + GT Exergy efficiency > 16% Environment h"p://www.ztekcorporadon.com/sofc_turbine.htm; h"p://www.britannica.com/science/geothermal-energy; h"p://www.power-technology.com/projects/uskmouth/ 12
Waste heat recovery with Organic Rankine Cycle (ORC) Power generation from waste heat Example: recovery from fluegas at Heat collector grid Check valve Pump Reservoir Condenser grid mean q = 120 o C Thermal efficiency : ε = E = 1 - Q T a T For q a = 20 o C, ε = 25%, but the true efficiency of a Carnot ideal engine Waste heat is100% Generator Power expander unit Exergy efficiency: η = E = 1 Q 1- T a / T Exergy efficiency is a better indicator! 13
Exergy efficiency, a better indicator than 1 st Law efficiency Indicates the true quality of energy COENERGY conversion technologies (Carnot TEMPERATURE engine: 100% exergy efficiency) Always 100% Coherent ranking of most technologies To be comple- mented by Coenergy=exergy of mass u+p a v-t a s renewable/non-renewable ratio BOREL L., FAVRAT D. Thermodynamics and energy systems analysis. EPFL Press (2010) 14
Electric efficiency of different technologies Electrical efficiency [%] 100 80 60 40 20 0 ORC Organic Rankine Cycle ECE External Combustion Engine ICE Iinternal Combustion Engine µgt Micro-gas turbine PEFC Polymer electrolyte FC SOFC Solid oxide fuel cell CC Combined cycle 15
Fuel cell technologies Fuel in (H 2, CH 4 ) Oxidant in (air) T operation H 2 O 2- H 2 O O 2 SOFC 650-1000 o C H 2 CO 3 2- O 2 H 2 O, CO 2 CO 2 O 2 MCFC 650 o C O H H + 2 2 PAFC 200 H 2 O o C H 2 H 2 O OH - AFC 50-100 o C H 2 H + O 2 H 2 O PEFC 50-100 o C Products and depleted fuel out e - Depleted oxidant out 16
Cogeneration with Solid Oxide Fuel Cell (SOFC) Air Operating N 2, O 2 regime : 700-800 o C O 2-1 bar (to 5 bar) H 2, CO H 2 O CO 2 Reformed Natural Gas Solid Oxide Fuel Cell stack Can potentially be inversed (High temperature electrolyser for storage) 17
Exergy efficiency in a Law (Geneva): System decomposition Electricity Power plant 1 Cogeneration District unit with or without heat pump 2 fuel Key messages from exergy analysis: Building plant 3 Room convector or radiator 4 Heat in the coolest way (heating temperature the closest to the need) Cool in the warmest way (cooling temperature the closest to the need) FAVRAT D., MARECHAL F., EPELLY O. The challenge of introducing an exergy indicator in a local law on energy. Energy,33, No2, pp130-136 (2008) 18
Managing the complexity of integrated systems: multi-objective optimisation Emissions (kgco2/kwh) Min Investment, max emission Min Emissions, max Investment Infeasible Investment ($/kw) 19
Advanced integrated systems and design methods for improved energy efficiency Ex: multi-objective optimisation of a trigeneration plant in a city From GIS to advanced integrated energy systems Alliance of Global Sustainability Tokyo half: A collaboration with MIT & University of Tokyo: [Bürer M., Tanaka K., Favrat D., Yamada K. in: Energy 2003] 20
Results from the optimisation of a trigeneration plant in a city 10000 CO2 Emissions [Tons/year] [tonco2/year] anode electrolyte cathode air -50% 4000 2.2 2.8 Annual Cost [m$/year] [million US$/year] 21
Advanced urban networks for increased synergy between users Cooling needs HeaDng needs Offer a Source /sink at intermediate temperature
District heating and cooling CO 2 network Winter Summer user user heat pump user user Central heat pump Central heat dissipater Henchoz S., Favrat D., et al. Key energy and technological aspects of three innovative concepts of district energy networks in Energy, June 2016
Mechanical vapor recompression in industrial processes (pinch technology representation) Temperature [ C] Before retrofit Temperature [ C] After retrofit STAINE F., FAVRAT D., Energy Integration of Industrial Processes Based on the Pinch Analysis Method Extended to Include Exergy Factors. Journal of Applied Thermal Eng., Vol.16, pp. 497 507, 1996 Heat rate [kw] Heat rate [kw] 24
Hierarchy of energy saving actions in industry Detailed simulation Advanced automation (e.g. adaptive control) Extensive use of optimization Change of process (e.g. batch con&nuous) Tarification (liberalization), smart grids, therm. & electr. storage Energy recovery with power components (heat pumps, expanders on compr. gases, ORC, heat transf.) Cogeneration, adapting utility network Energy integration with other processes Pinch technology Energy recovery, (heat exchangers ) Pump diameters adjustment Insulation. sealing Automatic stops (lighting, fans, ) Regulation (e.g. regrig-defrosting, thermostats) Maintenance (purge of condensate, filters, steam & air leaks) Reference consumption (indicators + regular checks) 25
Target of a 2000 W.year/(year.cap) Towards a 2000 watts society (average world consumption in year 2000) 1 t CO 2 /(year.cap) Controversial definition and objectives but intended to give a marketing impulse to the look for a better energy efficiency http://www.novatlantis.ch/fileadmin/downloads/2000watt/weissbuch.pdf Marechal F, Favrat D, Jochem E, Energy in the perspective of the sustainable development: The 2000 W society challenge Resources, Conservation and Recycling 44 (2005) 245 262 HALDI PA, FAVRAT D., Methodological aspects of the definition of a 2 kw society. Energy, vol 31, issue 15, Dec 2006., pp 3159-3170 26
Key energy saving approaches: a summary Better indicators (exergy efficiency) Better design methods: For energy integration (pinch analysis) Multi-objective optimization Better technologies: Heat pumps Fuel cells Co- and tri-generation Better integration between electric and gas grids with storage h"p://energycoalidon.eu/indicadve-nadonal-energy-efficiency-targets-fall-short 27
The stone age did not end because of lack of stones (attributed to sheik Yamani!) Let us not wait until the end of fossil fuels and an unbearable global warming to induce the necessary energy transition Thank you for your attention Also thanks to the contribution of Dr Pierre-André Haldi 28