System analysis of overall efficiencies of different routes for bioenergy. Content

Transcription

1 System analysis of overall efficiencies of different routes for bioenergy Thomas Nussbaumer University of Applied Sciences, Lucerne, Zürich Switzerland Content. Motivation 2. Methodology 3. Heating Systems 4. Power Production 5. Biofuels 6. Conclusions

2 Life Cycle Assessment (LCA) Valuation of green house effect 4000 Eco indicator 95 rf [ ] CO 2 high NO X SO 2 NO X PM... Öl Gas Stückholz Holzschnitzel Holzpellets Oil Gas Log w. W. chips W. pellets* F o s s i l W o o d f u e l s base low [Kessler&Frischknecht 2000] *[Nussbaumer 200] Neutral assessment by CED or CO 2 Cumulative Energy Demand ced NR [MJ primary non-ren. / MJ collectible] ced [MJ primary / MJ collectible] Greenhouse gas emissions [t CO 2 / TJ collectible] Natural Gas Light fuel oil Log wood ced Wood chips + district heat ced NR ced Data from [Hartmann & Kaltschmitt 2002]

3 Background Life Cycle Assessments (LCA) are useful, but... present aggregated data... are influenced by a valuation of CO 2 versus other environmental impacts, which is subjective The primary energy efficiency is only one aspect... but it is the most relevant one for energy systems... CO 2 is correlated to ced NR Aim Assessment of the primary energy efficiency of biomass based energy systems Sensitivity analysis for the main parameters: Plant efficiency Transport distance Fuel pretreatment

4 Content. Motivation 2. Methodology 3. Heating Systems 4. Power Production 5. Biofuels 6. Conclusions CED(t), EYC(t), t P [ TJ ] CED CEP E U CED(t) CED CEP(t) CEP Specific CED CED ced = > CEP Energy Yield Coefficient CEP EYC = < CED Nonrenewable ced ced NR = CED NR CEP CED NR (t) Nonrenewable EYC E0 E D E P 0 t P,NR 0 E U,NR Time t 20 t! CED NR [ a ] EYC NR = CEP CED NR

5 Content. Motivation 2. Methodology 3. Heating Systems 4. Power Production 5. Biofuels 6. Conclusions Primary energy Assumptions = lower heating value LHV of wood harvested without leaves Collectible energy = heat delivered to the building Annual plant efficiency = efficiency without district heat = 80% for reference case Electricity is rated with 2.5 corr. to the COP of a heat pump Diesel is accounted with.25 due to embodied energy Plant life time = 20 a

6 Scenario : Log wood boiler with Eta ref = 80% Scenario 2: Wood chips boiler with Eta ref = 80% + District heat

7 Scenario 3: Pellet boiler with Eta ref = 80% Energy Yield Coefficient for heating Lit EYC NR [TJ/TJ] Wood / Oil [ ] Log wood boiler Wood chips without district heat Wood chips with district heat with 3 MWh a m with.5 MWh a m with 0.6 MWh a m 7.9. Eco wood pellets with wood for drying Wood pellets with oil for drying of wet saw dust Light fuel oil boiler with flue gas condensation : [Nussbaumer 2004] 2: [Kessler et al. 2000]

8 ced [TJprim/TJcollecible] ced as function of annual plant efficiency 4.0! ex = Pellets, dh=.5 MWh (a*m)^-, TD=50 km Pellets w/o dh, TD=5000 km Pellets w/o dh, TD=500 km Pellets w/o dh, TD=50 km Pellets w/o dh, TD=5 km Eco-pellets w/o dh, TD=50 km Wood chips, dh=0.6 MWh (a*m)^- Wood chips, dh=.5 MWh (a*m)^- Wood chips, dh=3 MWh (a*m)^- Wood chips w/o dh, TD=5 km Log wood 70% Wood chips 72.5%... with district heat 8% Fossil dried wood pellets 82.5%! a [%] 4,6 8,0 Log wood w/o dh, heat storage tank Log wood w/o dh, w/o heat storage tank CED NR as function of plant life time 0.3 CEP* CEDNR* [a] 0.25! ex 0.3 = 2.5! a = 80%! ex = 2.5 Power 0.25! a = 80% Wood Pellets Log wood CEDNR* [a] t [a] t [a] Energy Payback Time << Plant life time Pellets, dh=.5 MWh (a*m)^-, TD=50 km Pellets w/o dh, TD=5000 km Pellets w/o dh, TD=500 km Pellets w/o dh, TD=50 km Pellets w/o dh, TD=5 km Eco-pellets w/o dh, TD=50 km Wood chips, dh=0.6 MWh (a*m)^- Wood chips, dh=.5 MWh (a*m)^- Wood chips, dh=3 MWh (a*m)^- Wood chips w/o dh, TD=5 km Log wood w/o dh, heat storage tank Log wood w/o dh, w/o heat storage tank Power plant, 25%el, hp: COP=2.5 Power plant, 50%el, hp: COP=2.5 Power plant, 25%el, hp: COP=5 Power plant, 50%el, hp: COP=5 Collectible Energy Production (CEP)

9 ced NR (TD) 850 km 200 km Wood chips with dh w/o dh km Log wood km Wood Pellets 0.8 cednr [-] (607) (529) (82) (90) 0.2 (7) (3) 82 km 607 km Pellets w/o dh 2 Wood chips w/o dh 3 Wood chips, dh=.5 MWh a-m- 4 Power plant, 25%el, hp: COP=2.5 5 Power plant, 50%el, hp: COP=2.5 Road transport with driving distance = 2 TD Transport TD [km] Distance TD [km] Content. Motivation 2. Methodology 3. Heating Systems 4. Power Production 5. Biofuels 6. Conclusions

10 Sources of Greenhouse Gas Emissions Electricity CO 2 -Sequestration or Renewables Transport Industry Agriculture Household Craft [International Energy Agency (IEA) 2006] Efficiency of power production from biomass Eta e [%] Gas engines IGCC Gasification Steam Steam CHP MW e

11 Scenario 4a: Power production with Eta = 25% Example: Steam plant with 0 20 MWe + Scenario 4b: Power production with Eta = 50% Example: Integrated Gasification Combined Cycle with Eta e > 40% for 00 MWe

12 Energy Yield Coefficient for heat and power Lit EYC NR [TJ/TJ] Log wood boiler 3.8 Wood chips without district heat 3.0 Wood chips with district heat with.5 MWh a m 9.0 Eco wood pellets with wood for drying 8.3 Power plant & heat pump with 25% el and COP = Power plant & heat pump with 50% el and COP = [Nussbaumer 2004], 3 [Hartmann&Kaltschmitt 2002] 4 [Studer et al. 99], 5 [Wörgetter et al. 999], 6 [Osteroth 992] Comparison Wood heating Wood IGCC Efficiency Eta Eta Eta * COP PM Emission [mg/m 3 % O 2 [mg/mj heat]

13 Content. Motivation 2. Methodology 3. Heating Systems 4. Power Production 5. Biofuels (Outlook) 6. Conclusions Energy Yield Coefficient for power and fuels Log wood boiler Wood chips without district heat Wood chips with district heat with.5 MWh a m Eco wood pellets with wood for drying Power plant & heat pump with 25% el and COP = 2.5 Power plant & heat pump with 50% el and COP = 5 Bio Diesel without / with side products Ethanol from sugar beets in Europe Ethanol from maize or potatoes / cereals in Europe 2nd Generation Biofuels (e.g. FT-Diesel) Lit 3,4, EYC NR [TJ/TJ] / /.3?? [Nussbaumer 2004], 3 [Hartmann&Kaltschmitt 2002] 4 [Studer et al. 99], 5 [Wörgetter et al. 999], 6 [Osteroth 992]

14 Content. Motivation 2. Methodology 3. Heating Systems 4. Power Production 5. Biofuels 6. Conclusions Conclusions. The method of Cumulative Energy Demand and Energy Yield is valuable to compare different bioenergy routes in one sector and to investigate the influence of parameters. 2. However, applications for heat, power, and transport cannot be compared directly and hence needs reference scenarios. 3. If nowadays energy systems are assumed as reference scenarios, the potential to substitute fossil fuels is likely to exhibit the following ranking:. highly efficient power production 2. efficient heating systems 3. Biofuels for transport

15 Conclusion Fossil fuel substitution and CO 2 reduction with biomass seem most efficient in the following order:. Highly efficient power production 2. Efficient heating systems 3. Biofuels Acknowledgements IEA Bioenergy Task 32 Biomass Combustion and Co-firing Swiss Federal Office of Energy

16 Downloads Nussbaumer T, Oser, M: Evaluation of Biomass Com-bustion based Energy Systems by Cumulative Energy Demand and Energy Yield Coefficient, IEA or Nussbaumer T: 9. Holzenergie-Symposium, Zürich or via link from The end

17 st Generation Biofuels: Plant methyl ester Oil plants only Low yield per hectare Energy Yield Coefficient =.5 without side products 2.5 with side products [Studer et al. 99] st Generation Biofuels: Plant methyl ester Erntefaktor =,5 2,5 MJ/MJ Nur Ölpflanzen Geringer Flächenertrag

18 st Generation Biofuels: Bioethanol EYC = 2.? [Hartmann&Kaltschmitt 2002] [Osteroth 992] 2nd Generation Biofuels from Synthesis Examples Biomass-to-Liquids, BtL via Fischer-Tropsch (FT-Diesel) CO + H 2 > C n H 2n/+/+2 + H 2 O CO + H 2 Hydrogen via CO-Shift CO + H 2 O > CO 2 + H 2 Methane via Methanisation CO + 2 H 2 > CH 4 LHV Biofuel / LHV Biomass < % EYC =?

19 Transformation CED in [TJ] to CED* in [a] EYC(t), t P E 2!000 TJ CEP TJ TJ a = a A CED NR 20 CEP* B a t P,NR t TJ E 3!000 CEP E* = E E C a t t P,NR t P,NR A B CED NR * CED NR * A B CED NR t B=A 0 t P,NR 0 t 20 a Content. Motivation 2. Methodology 3. Results for different Energy Systems 4. Influence of Transport Distance 5. Power Production 6. Conclusions

20 Transport Distance = 2 x Radius (due to empty return drice) Plant efficiency and Net efficiency including transport