UC Irvine

A methodology for assessing the efficiency and economic viability of renewable gas generation and energy conversion to compliment residential PV is proposed and demonstrated for a 10,000 resident example community in Huntington Beach, California. Dynamic solid oxide fuel cell (SOFC) performance on two fuels was explored to inform electricity production assumptions. These efforts included operating an SOFC on natural gas, using experimental data to verify an SOFC model, and simulating SOFC operation on clean biogas. Renewable fuel production processes included in the community zero-net-energy assessment are 1) through the processing of community-produced organic fraction of municipal solid waste (OFMSW) in an anaerobic digester and 2) using solar generation paired with power-to-gas technologies. Six pathways – ending in natural gas pipeline injection or SOFC electricity production – were evaluated for two PV capacity scenarios. The renewable fuel production potential of community-produced OFMSW was determined to be 0.24 MMBTU/y of renewable natural gas (RNG) from anaerobic digestion and up to 2.85 MMBTU/y of hydrogen from electrolysis using excess solar PV electricity. A payback period of 7 years, equal to that of a modern natural-gas power plant, requires the renewable fuel sale price to be 5.2-15 times larger than the 2017 California residential average natural gas price and the renewable electricity sale price to be 3.0-6.8 times larger than the 2017 local average residential electricity price. Results show >80% of the community electrical demand can be met through a combination of solar PV, anaerobic digestion, and SOFC operation. In this scenario, solar PV meets 52% of the community electrical load, while excess solar production produces hydrogen that is passed through a fuel cell to meet 26% of the electrical load. The remaining 3% is met using RNG produced through anaerobic digestion using only organic waste from the studied community.