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Research Papers

Cost Requirements for a Small-Scale SOFC Fed From Agricultural-Derived Biogas

[+] Author and Article Information
Samuel Majerus

GEM Group,
Swiss Federal Institute of Technology Lausanne,
Sion,
Wallis 1951, Switzerland
e-mail: samuel.majerus@alumni.epfl.ch

Dirk Lauinger, Jan Van herle

GEM Group,
Swiss Federal Institute of Technology Lausanne,
Sion,
Wallis 1951, Switzerland

1Corresponding author.

Manuscript received September 8, 2016; final manuscript received January 25, 2017; published online February 28, 2017. Assoc. Editor: Jacob Bowen.

J. Electrochem. En. Conv. Stor. 14(1), 011002 (Feb 28, 2017) (7 pages) Paper No: JEECS-16-1123; doi: 10.1115/1.4035891 History: Received September 08, 2016; Revised January 25, 2017

In this work, the use of fuel cells for valorizing agricultural-derived biogas in Switzerland is studied. The Swiss agricultural case is characterized by farms with small numbers of animals (20 cows) and high feed-in tariffs (FIT) for biogas-derived electricity (0.49 CHF/kWhel). Thus, small-scale biogas installations are reviewed and the possibility to couple them with solid oxide fuel cells (SOFCs) and photovoltaic (PV) panels is analyzed. To date, less than 5% of the Swiss agricultural biogas potential is used. It is possible to increase this value significantly up to 86% through the deployment of 2 kWel engines. The small size of the Swiss farm requires biogas installations in the kW-range. Small-scale biogas facilities are not profitable yet: the main challenge is to bring down the lifetime cost of the fuel cells to 11,000 CHF/kWel (considering a lifetime of ten years) and to reduce the investment cost (IC) of small-scale biogas facilities to around 9500 CHF/kWch. In the kW-range, solid oxide fuel cells (SOFCs) have higher electrical conversion efficiencies than internal combustion engines (ICEs). It is shown that SOFCs become competitive over combustion engines if the investment cost of the former decreases below 13,000 CHF/kWel for a lifetime of 11 years. Combining the biogas facility with a PV-battery system, which covers the digester's electricity needs, is found to be beneficial. A considerable reduction in the feed-in tariffs would make small- to medium-scale biogas installations unprofitable, at current cost. In order to reach a break-even under these conditions, the investment cost of the biogas plant needs to drop below 4000 CHF/kWch, whereas the investment cost of the SOFC needs to drop below 3400 CHF/kWel.

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Figures

Grahic Jump Location
Fig. 1

Schema of the studied biogas installations and different scenarios

Grahic Jump Location
Fig. 2

Break-even of the first scenario for different farm sizes (ICE)—eff. 25% (elec.) and 53% (therm.), digester needs 10% (therm.) and 2% (elec.) of the biogas chemical energy

Grahic Jump Location
Fig. 3

Break-even of the second scenario for different farm sizes (SOFC)—eff. 50% (elec.) and 40% (therm.), digester needs 10% (therm.) and 2% (elec.) of the biogas chemical energy

Grahic Jump Location
Fig. 4

Break-even of the fourth scenario (low FIT) for different farm sizes (SOFC)—eff. 50% (elec.) and 40% (therm.), digester needs 10% (therm.) and 2% (elec.) of the biogas chemical energy

Grahic Jump Location
Fig. 5

Comparison of the break-even of the three first scenarios for the smallest farm size (20 cows and 15 ha)—digester needs 10% (therm.) and 2% (elec.) of the biogas chemical energy

Grahic Jump Location
Fig. 6

Comparison of the break-even for a medium farm size (80 cows and 60 ha)—digester needs 10% (therm.) and 2% (elec.) of the biogas chemical energy

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