Photovoltaic Solar Water Heating System.
Photovoltaic Solar Water Heating System.
(836 K)
Fanney, A. H.; Dougherty, B. P.
International Solar Energy Conference. Proceedings.
American Society of Mechanical Engineers. March
31-April 3, 1996, San Antonio, TX, 1-10 pp, 1996.
ASME Journal of Solar Energy Engineering, Vol. 119,
126-133, May 1997.
Keywords:
building technology; photovoltaic; solar; water heaters
Abstract:
A novel solar water heating system was patented in 1994.
This system used photovoltaic cells to generate
electrical energy that is subsequently dissipated in
multiple electric resistive heating elements. A
microprocessor controller continually selects the
appropriate heating elements such that the resistive
load causes the photovoltaic array to operate at or near
maximum power. Unlike other residential photovoltaic
systems, the photovoltaic solar water heating system
does not require an inverter to convert the direct
current supplied by the photovoltaic array to an
alternating current or a battery system for storage. It
uses the direct current supplied by the photovoltaic
array and the inherent storage capabilities of a
residential water heater. A photovoltaic solar hot
water system eliminates the components most often
associated with the failures of solar thermal hot water
systems. Although currently more expensive than a solar
thermal hot water system, the continued decline of
photovoltaic cell prices is likely to make this system
competitive with solar thermal hot water systems within
the next decade. This paper describes the system,
discusses the advantages and disadvantages relative to
solar thermal water heating systems, reviews the various
control strategies which have been considered, and
presents experimental results for two full-scale
prototype systems.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899