Experiences With Using Solar Photovoltaics to Heat Domestic Water.
Experiences With Using Solar Photovoltaics to Heat
Domestic Water.
(631 K)
Dougherty, B. P.; Fanney, A. H.
Solar Energy: The Power to Choose. International Solar
Energy Conference. Forum 2001. Proceedings. April
21-25, 2001, Washington, DC, 2001.
Keywords:
water; solar photovoltaics; solar; water heating
Abstract:
The solar photovoltaic (PV) industry continues to make
progress in increasing the efficiency while reducing the
manufacturing costs of PV cells. Exonomies of scale are
being realized as manufacturers expand their production
capabilities. Products are commercially available that
integrate photovoltaic cells within building facade,
fenestration, and roofing components. Legislation and
incentive programs by government and commercial entities
are supporting both reduced first costs and greater
rates of return. The combination of factors support
improved cost-effectiveness. As this trend continues,
more options for using PV become possible. One such
application is a standard-alone, PV-direct, solar water
heating application. Solar water heating can be
effectively accomplished by directly using the DC power
production from solar photovoltion Modules. A simple
controller having multiple power relays connects the PV
modules with different combinations of in-tank resistive
elements. The controller actively changes the resistive
combination so that the photovoltaic modules generate
power at or near their maximum output. The technology,
which has been patented, is applicable to configurations
that use a single water heater and to two water heaters
that are piped in series. Prototypes using both tank
configurations were monitored at four field sites. This
paper emphasizes the single-tank application and the
field results from installations in Maryland and
Florida.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899