Operating a 250 kW landfill gas fired microturbine at a 0.4 hectare research and demonstration greenhouse

A 250 kW landfill gas-fired microturbine system was installed at a 0.4 ha research and demonstration greenhouse located at the Burlington County Resource Recovery Complex in Columbus, NJ. The landfill gas is scrubbed of sulfur (H2S), compressed, and chilled (to remove moisture and siloxanes) prior to combustion in the turbine. Waste heat contained in the exhaust gasses is reclaimed using a gas-to-liquid heat exchanger. The captured waste heat is used to help heat the greenhouse and is distributed through the hot water heating system. The electricity generated by the turbine is used to power electrical equipment (including the supplemental lighting system) in the greenhouse facility. Excess electricity is exported to the local utility grid. The exported electricity provides a separate revenue stream in addition to the crops produced in the greenhouse. Furthermore, every 1000 kWh of electricity produced generates a renewable energy credit that can be sold to third parties to satisfy requirements for renewable energy portfolios. The microturbine uses the relatively low energy content landfill gas (~17.1 MJ m-3) at a rate of approximately 51.9 L s-1 and converts it into 220 kW of electricity (yearly average). Approximately 30 kW of electricity is required to operate the equipment, primarily the compressor and chiller (parasitic losses). In addition, approximately 1.16 GJ h-1 of heat energy is recovered. The estimated annual run-time percentage is 80% or higher. This paper includes operational data as well as a discussion of potential management strategies for operating the equipment as economically as possible. Since grid electricity prices fluctuate rapidly depending on demand, time-of-day, season, etc., and crop requirements change depending on weather conditions, crop stage, harvesting schedule, etc., the operational management of the combined heat and power equipment and greenhouse equipment can be quite challenging. Consequently, decision support tools for growers and operators were developed.