NIST has developed a test facility for residential fuel cell systems to determine the performance of these systems on a seasonal basis. The facility was designed to test grid independent, grid interconnected, and stand alone systems with an AC electrical output less than 6 kW. Currently, the test facility is setup to deliver natural gas as the fuel, but only slight modifications would be required to use propane or hydrogen as a fuel. A domestic hot water system has also been developed to determine the amount of useful thermal energy output of the fuel cell system. The test facility encompasses three rooms: an environmental chamber to simulate outdoor ambient conditions, an environmental chamber to simulate indoor ambient conditions, and a control room that houses the data acquisition and control system.
Specifications / Capabilities:
The outdoor environmental chamber houses the main residential fuel cell system, and it can vary the ambient temperature from -18°C to 40°C (0°F to 104°F) and the relative humidity from 20% to 100%. Any equipment that would typically be installed indoors, which would include the domestic hot water storage, pumps, etc., is placed in the indoor chamber. The indoor environmental chamber has the full range of ambient temperatures and relative humidity as the outdoor chamber, but the conditions will be maintained at more typical indoor conditions. For electrical output to the existing grid, a power analyzer measures the true power, RMS voltage and current, and power factor. To simulate a system that is not connected to the electrical grid, an AC load draws and measures electrical power from the residential fuel cell system. A calorimeter continually monitors the heating value of the fuel entering the system. Thermocouples and platinum resistance thermometers measure the temperature rise of the water used for domestic hot water heating. A turbine and magnetic flow meter measure the flow of water for the domestic hot water system. With these values, all of the energy produced and consumed by the fuel cell can be determined. The thermal output can be measured using two methods. First, the temperature rise of a stream of water with a constant inlet temperature and flow rate will be used to create a performance map of the steady state thermal output of a system. Also, the facility is able to simulate a typical installation setup that includes a preheat tank warmed by the thermal energy from the fuel cell and an auxiliary tank heated with electricity from the residence. This capability provides a more realistic measurement of the fuel cell system's capability to heat domestic hot water.