Metis Design Corporation (MDC)

In 2013, centralized U.S. power plants had an average electricity generation efficiency of only 33%, wasting 67% of primary energy as heat and emitting 2 billion tons of CO2, about 38% of U.S. total emissions. Further, 6% of electricity is generally lost during transmission and distribution from the power plant to the customer. An alternative to centrally produced power is distributed generation, in which electricity is generated at the point of use. Residential combined heat and power (CHP) systems can burn natural gas to produce electricity for a home while also using the waste heat for space and water heating. The potential energy efficiency for CHP systems is more than 80% and significant adoption of such systems would enable dramatic reductions in primary energy use and concurrent CO2 emissions. However, usage of small CHP systems is not widespread because systems currently on the market are limited by high price, low efficiency, and short lifetime. The GENSETS program seeks to develop 1 kW (electric) CHP generators that have high fuel-to-electricity generation efficiency, long life, low cost, and low emissions.

Metis Design Corporation (MDC) with Lawrence Berkley National Laboratory will develop a Brayton cycle engine for residential use to produce heat and electricity. To begin the cycle, air is drawn into the system where it is compressed and pressurized. This compressed air is then heated in a recuperator and introduced in to the combustion chamber. Fuel is injected in to the combustion chamber and subsequently the air-fuel mixture is ignited. The high temperature exhaust gases then expand through a turbine, providing some of the work that drives the original compressor and the remainder produces electricity in a generator. Other innovations include adding a rotating vaneless diffuser to the compression process to reduce viscous losses that would normally reduce the efficiency of small compressors. The design also includes a high-efficiency recuperator to capture waste heat from the turbine exhaust and a low swirl burner to reduce emissions.

If successful, MDC’s project will facilitate development and commercialization of economical, efficient, and durable CHP systems for residential use. These advancements support progress toward ARPA-E’s overall goals as follows: