Page 218 - Solar Power in Building Design The Engineer's Complete Design Resource

188 LEED—LEADERSHIP IN ENERGY AND ENVIRONMENTAL DESIGN

Figure 7.2 Los Angeles Audubon Center grid-independent solar
power generation, system. Photograph courtesy of LA Audubon Society.

The thermal solar air-conditioning system, which is used only in a few countries,
2
such as Germany, China, and Japan, utilizes an 800-ft array of 408 Chinese-
manufactured Sunda vacuum tube solar collectors. Each tube measures 78-in long and
has a 4-in diameter, and each encloses a copper heat pipe and aluminum nitride plates
that absorb solar radiation. Energy trapped from the sun’s rays heats the low-pressure
water that circulates within and is converted into a vapor that flows to a condenser sec-
tion. A heat exchanger compartment heats up an incoming circulating water pipe
through the manifold which allows for the transfer of thermal energy from the solar
collector to a 1200-gal insulated high-temperature hot-water storage tank. When the
water temperature reaches 180°F, the water is pumped to a 10-ton Yamazaki single-
effect absorption chiller. A lithium bromide salt solution in the chiller boils and pro-
duces water vapor that is used as a refrigerant, which is subsequently condensed; its
evaporation at a low pressure produces the cooling effect in the chiller. Figure 7.3
depicts the solar thermal heating and air-conditioning system diagram.
This system also provides space heating in winter and hot water throughout the
year. Small circulating pumps used in the chiller are completely energized by the solar
photovoltaic system. It is estimated that the solar thermal air-conditioning and heating
system relieves the electric energy burden by as much as 15 kW. The cost of energy
production at the Audubon Center is estimated to be $0.04/kW, which is substantially
lower than the rates charged by the city of Los Angeles Department of Water and
Power. Note that the only expense in solar energy cost is the minimal maintenance and