BIOMASS FUELLED FUEL CELLS: No Hydrogen Required Brant A. Peppley Canada Research Chair in Fuel Cells and Director Queen’s-RMC Fuel Cell Research Centre
But First a Crash Course on Fuel Cells Brant A. Peppley Canada Research Chair in Fuel Cells Director Queen’s-RMC Fuel Cell Research Centre
A Sample of Types of Fuel Cells • Proton Exchange Membrane (PEM, SPE(TM), PEFC) • Hydrogen - Air • Direct Methanol - Air • Solid Oxide (SOFC) • Molten Carbonate (MCFC, Direct Fuel Cell, DFC) • Phosphoric Acid (PAFC) • Alkaline (AFC)
Polymeric (Acid) Electrolyte Membrane Fuel Cell Operation on Hydrogen and Air This is the PEM fuel cell that everyone thinks of when we talk about the fuel cell car It is the classic Ballard fuel cell It is one of many types of fuel cells
PEM Fuel Cells:Forklift Truck Battery Replacement Fuel cell powered material handling equipment for large warehouse operations have already shown a cost benefit Convenient hydrogenrefuelling WalMart successfully field tested General Hydrogen forklifts Two units field tested at GM and Fedex. GM have shown there is a real cost benefit of using Hydrogenics fuel cell forklift trucks instead of battery power forklift trucks.
PEM Fuel Cells:Backup Power Systems 12 kW Hydrogenics Awarded Supply Agreement From American Power Conversion to Deliver Up to 500 Fuel Cell Power Modules for Backup Power Applications Batteries 1 tank of H2 20 minutes For e-commerce systems in urban centres this is the only practical power backup option
Direct methanol fuel cells : Micro-electronics Power Probably first mass market fuel cell product.
Solid Oxide Fuel Cells: Stationay Power • Five kilowatt residential SOFC system • Five megawatt combined fuel cell / gas turbine power plant. Waste heat at 1000ºC Low cost ceramic and non-noble metal materialsNat. gas/methane fuelled
Molten Carbonate / Direct Fuel Cell: Stationary Power • Also well suited for distributed power market. • High fuel-to-electricity efficiencies. • Internal reforming = directly consume nat. gas / methane • 650ºC(1200ºF) and atmospheric pressure = good quality waste heat.
300 kW 1.5 MW Molten Carbonate
Phosphoric Acid: Small Stationary 200 kW palletized systems Nat. gas fuelled
Alkaline Three 30 kW fuel cells used on the orbiter. Pure hydrogen required. Poisoned by CO2
Ballard Power System Fuel Cell Stack Ser. No. 002 (1986) Why I became interested in biomass for fuel cells!
MotivationsScepticism of Hydrogen Economy • A hydrogen economy, using fuel cells for energy conversion, claims to address GHG emissions but currently the most economic methods of making hydrogen is from natural gas and produces significant GHG. • There are still significant technical barriers to overcome for both fuel cells and hydrogen • Nuclear energy is being proposed as the answer to global warming but no one seems to have examined the impact of building a large number of large power plants producing so much waste heat.
MotivationsNeed to address GHG emissions • We urgently need to address greenhouse gas (GHG) emissions. • Finally it appears to be generally accepted that global warming (or at least climate change) is real. • Since virtually all living things in the biosphere operate by using biomass as fuel, and generate power using fuel cells, this would appear to be the most environmentally sustainable method of producing energy.
A carbohydrate economy? • The most common energy currency on the planet, used by virtually every living thing, is the carbohydrate. • Carbon is constantly recycled and is kept in balance in the system Switchgrass Fast rotation willow trees
Sources of Biomass • Waste streams of carbohydrates • landfill • waste water treatment plants • wood waste • agricultural waste • other • Virgin biomass • wood • grasses • not corn!!
Landfill Gas • Approximately 55 million metric tons of carbon equivalent are released into the air each year by landfills • More than 340 landfill-gas-to-energy sites in the US • Typically use large reciprocating engines for combined heat and power systems • Low methane concentration landfill gas often cannot be used for combustion engines but can still be used with fuel cells
Waste Water Treatment Plants • Anaerobic Digestion generates high quality fuel (>50 vol% methane) • Easily accessible and collection costs prepaid • Methane is 23 times more powerful GHG than CO2 • WWTP gas fuel cells systems would only supply a small fraction of our energy needs but would stop a significant amount of GHG emissions
Average WWTP ADG Composition(from available data in Ontario) I.R. Wheeldon, C. Caners and K. Karan, Conference Proc BIOCAP, First National Conference, Ottawa, February 2005. www.biocap.ca/images/pdfs/conferencePosters/Wheeldon_I_P1.pdf.
Wood Waste • Relatively large gasifiers already in operation • Often located in remote locations where distributed power is needed Comparision of McNeil Gasifier Gas Composition to Battelle Pilot Data [Paisley et al., 2000] Burlington Electric Department, Vermont
Agricultural Waste • Farm-based anaerobic digesters • In 2002, 40 farm digester to energy projects in the US prevented 124,000 metric tonnes of CO2 emission • 9 swine, 29 dairy, 2 poultry farms • Commercial anaerobic digesters for farms are already available
Technical Feasibility of Biogas Fuelled Fuel Cells • Numerous demonstrations have already proven the technical feasibility • phosphoric acid fuel cell (PAFC) on landfill gas • PAFC on waste water treatment gas (WWTG) • molten carbonate fuel cell (MCFC) on WWTG • solid oxide fuel cell (SOFC) on AD gas • Most technical problems have been overcome • wide array of contaminants to clean up • high degree of variability in fuel quality
PAFC Demonstrations • UTC Fuel Cells PC-25 currently in operation • Eight PC-25 systems in New York City (first in 1997) • One PC-25 in Köln-Rodenkirchen, Germany - Portland, Oregon 200-kilowatt PC25 that converts anaerobic digester gas generated by the wastewater treatment facility into usable heat and electricity for the facility.
RWE Installation Rodenkirchen Stahl, Knut - Experiences from the PAFC Operation with Sewage Gas 3rd BFC Net Workshop Jan. 2005. http://www.bfcnet.info Downloads.
Performance Verification Report – PAFC Results of 30 day test program for a PC25C Operated by NY Power Authority May - June 2004 Greenhouse Gas Technology Center, EPA, Environmental Technology Verification Report, September 2004, www.sri-rtp.com/PC25_VR_final.pdf.
MCFC System on Wastewater Treatment Gas May 4, 2005News Release King County earns national environmental award for generating electricity from waste water treatment plant methane gas 1 Megawatt
SOFC Demonstrations • Limited number of installations • 1 kW experimental demonstration on fermentation gas Implementation of SOFC system into biogas plant CHABLOZ in Lully http://www.bfcnet.info/downloads/Jenne.pdf
Technical ChallengesBiomass to Biogas Conversion • Anaerobic digestion is suitable for wastewater treatment, landfill and agricultural waste but not for wood waste or virgin biomass. For agricultural wastes in cold climates the energy yield can be low due to the need for stirring and external heating • Gasification is a mature technology but the classic air-blown gasifiers generate very low heating value gases. Indirect gasifiers are better • Pyrolysis is appealing because of the production of pyrolysis oil but it is not economic and there are technical problems. Possibly a hybrid bio-oil and hydrogen system would be more economically attractive
Technical ChallengesBiomass to Biogas Conversion Anaerobic Digester
Technical ChallengesBiomass to Biogas Conversion Gasifier 50 MW Biomass gasifier power system
Technical ChallengesGas Clean Up • Contaminant removal requirements are highly dependent on type of fuel cell used and the type of biomass. H2S, organic acids, siloxanes, alkali metals, halogens. • PAFC clean up system has been successfully demonstrated and a performance verification report published. • PAFC more sensitive to poisons than SOFC and MCFC Greenhouse Gas Technology Center, EPA, Environmental Technology Verification Report, UTC Fuel Cells PC25C Power Plant – Gas Processing Unit Performance for Anaerobic Digester Gas, September 2004, www.sri-rtp.com/GPU-VR-final.pdf
Technical ChallengesGas Clean Up • H2S clean up achievable with activated carbon. Can be made regenerable • Frequency of carbon replacement is acceptable for low H2S concentrations (<100 ppm) • For higher concentrations a regenerable system with trapping is required (needs work!) • Siloxanes are a more serious problem! • In high temperature fuel cells siloxanes form glassy deposits
Technical ChallengesGas Clean Up – Siloxane Removal • Siloxane removal is one of the more challenging aspects of using landfill or WWTP AD biogas • Agricultural waste ADG does not contain siloxanes • cows don’t use cosmetics and conditioner!!
Biogas Fuel Processing • A fuel processor changes the composition of the biogas so that it can be fed to a fuel cell system to a hydrogen-rich mixture that can be fed to a fuel cell • The process adds complexity to the system but usually is necessary in order to obtain acceptable fuel cell performance and lifetime.
Biogas Reforming – Technical Challenges • Diluent and contaminant issues • in landfill site methane capture, problems can arise from excessive Nitrogen dilution • oxygen contamination can also result in poor reformer performance • CO2 Dilution • high CO2 concentrations result in some dry reforming occurring in reformer • this can lead to carbon deposition (coking) • better catalysts that avoid coking are required
Economics of Biomass Fuelled Fuel Cell Systems: Issues • Difficult to the predict cost of most fuel cells • Valuation of carbon credits and assessment of GHG reduction? $2 - 50 per ton • recently valued at $20-25 per ton • Duty cycles with large peak demands can dramatically increase cost and reduce efficiency. This has a negative effect the economics.
Valuation of Carbon Credit • Even if we do know the value of a carbon credit how do we evaluate the actual GHG reduction Relative GHG Emissions for Natural Gas and Various Biomethane Fuelled Fuel Cell Power Systems Nilsson, L.J., and K. Ericsson http://www.bfcnet.info/downloads
Limited Cost Data • Portland OR reports having spent $1.3 million for their 200 kW PAFC system • The mayor of New York City reports that eight 200 kW PAFC systems were installed at a cost of $13 million. Based on these numbers the average cost per unit is $1.6 million or $8000 per kW • The initial cost of a landfill gas fuelled MCFC system was estimated to be US$1950-2350 per kW compared to US$1370 per kW for the gas engine.
Economic Feasibility • The economics of biomass fuelled fuel-cell systems are still very difficult to assess. Even for PAFC systems that have had a long operating history the predicted cost per kW and the actual cost per kW can differ by a factor of two or three. • The cost of the fuel cell is also very vague. • Based on material costs SOFC stacks look very competitive • near term projected cost = US$400 per kW • the potential cost reduction with large-volume manufacturing methods is as low as US$180 per kW.
Conclusions • Biomass-fuelled fuel cell systems are technically feasible and have been operated for extended periods with good reliability and performance • Economic feasibility is much more difficult to assess but it appears that costs are too high • The impact of carbon credits on the economics of biomass fuelled fuel cell systems may be a significant factor in the near future. • Utilising waste biomass for power generation will not solve our energy and GHG problems but it can significantly reduce GHG emissions
www.fcrc.ca Brant Peppley Director Brant.Peppley@queensu.ca