Page 138 - Sustainable Cities and Communities Design Handbook

Renewable Energies Technology and Smart Grid in China Chapter j 6 115

unit is an electronic device that turns direct current (DC) from the solar
electricity into an alternating current (AC) that is matched to the incoming
main electric utilities standard and that is used by almost all home appliances
and electrical devices. The concern for safety also requires the solar electric
system to be enabled by circuit breakers for safe maintenance, etc. Circuit
breakers are typically connected in both the DC and AC sides of circuitry path.
STPP employs utility-scale steam turbine technology. As shown in Fig. 6.3,
STPP collects the solar energy in a large real estate footprint for thermal energy
to produce electricity. A circular array of solar light reflectors is used to
concentrate the light on a receiver located at the top of a tower. The light is
absorbed as heat energy, which heats up the steam gas or air to very high tem-
peratures, which produces pressurized hot gas or air to drive the turbine. STPP
has a typical footprint equivalent to the scale of a coal-fired utility power plant.
STPP employs direct sunlight and hence requires its plant site to be in the
regions of high solar radiation. The thermal energy storage may be typically

FIGURE 6.2 Schematic of a solar PV cell that converts sunlight to electricity; see text for details.

FIGURE 6.3 Solar thermal generator receives highly concentrated sunlight beam, heats up
pressurized gas in the receiver till it is very hot, and drives hot gas through a turbine that makes use
of the excellent cycle to produce electricity with combined hot gas and turbine operation.