Thermal Performance of Residential Electric Water Heaters Subjected to Various Off-Peak Schedules.
Thermal Performance of Residential Electric Water
Heaters Subjected to Various Off-Peak Schedules.
(859 K)
Fanney, A. H.; Dougherty, B. P.
American Society of Mechanical Engineers (ASME); Japan
Solar Energy Society (JSES); and Korean Solar Energy
Society (KSES). International Solar Energy Conference,
1992. Volume 2. April 5-9, 1992, Maui, HI, American
Society of Mechanical Engineers, New York, NY, Stine,
W.; Kreider, J.; Watanabe, K., Editor(s)(s), 1221-1230
pp, 1992.
Journal of Solar Energy Engineering, Vol. 118, 73-80,
May 1996.
Sponsor:
Department of Energy, Washington, DC
Keywords:
electric heaters; water heaters; tests; computer models;
thermal efficiency
Abstract:
A number of electric utilities use residential water
heaters for reducing electrical demand. A water heater
used in this manner is typically called an off-peak
water heater because resistive heating is unrestricted
during utility off-peak periods. During on-peak
periods, by comparison, the utility seeks to limit and
delay resistive water heating. Laboratory tests, where
the off-peak period and hot water draw schedule were
varied, were conducted on two residential storage water
heaters. A computer model of an electric water heater
was developed and validated. The laboratory tests and
the model were used to quantify the effect that various
off-peak and hot water draw schedules have on water
heater thermal efficiency. Thermal efficiency was found
to vary up to 7% for water heaters which meet the 1991
minimum efficiency standards as specified within the
National Appliance Energy Conservation Act. The energy
factor, as measured using the Department of Energy Test
Procedure for Water Heaters, was found to be independent
of the off-peak schedule because of a "normalizing" that
occurs as part of the calculation procedure.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899