Page 14 - Design of Solar Thermal Power Plants

1.2 BRIEF INTRODUCTION TO SOLAR THERMAL POWER GENERATION 7

1.1.7 Principles of Concentration Field Design
The determination of the concentration field area serves as the key to
CSP plant design and is normally calculated by applying the design point
method.
Design point is a very important concept for CSP generation design
and can be used to determine the parameters of various segments of solar
concentration field, the receiver, thermal storage, and power generation.
Factors of a design point include time, solar DNI, ambient air tempera-
ture, and wind speed, etc. The time selection is normally midday during
the spring or autumn equinox; annual mean temperature can be used
as the ambient air temperature and annual mean wind speed can be used
as the respective wind speed.
In determining unit capacity, two methods can be used for selecting the
solar direct normal irradiance that corresponds to the design point:

1. Apply solar direct normal irradiance ¼ 1 kW/m 2 when the
designed area of the concentration field is small; if the calculated
2
concentration field area has an irradiance of less than 1 kW/m ,itis
impossible for the needs of the power generation and thermal
storage systems to be directly satisfied by field output.
2. Apply the annual mean solar direct normal irradiance of the locality
when the designed area of the concentration field is large. The
output of the concentration field is normally sufficient to satisfy the
energy needs for thermal storage and the steam turbine. In cases
where solar irradiance exceeds the annual mean level, a portion of
the concentration field shall be closed.

To exert maximum functionality of the concentrator relative to a large
one-time investment, the first method is normally adopted for concen-
tration field design.
The annual capacity factor of the CSP plant is determined by the design
point and operational mode of the power plant.
Thermal storage capacity is determined by generator unit capacity, the
annual capacity factor, and the operational mode of the power plant.

1.2 BRIEF INTRODUCTION TO SOLAR THERMAL
POWER GENERATION

1.2.1 Basic Concepts of Solar Thermal Power Plants

With the gradual exploration and consumption of conventional energy
resources such as coal, petroleum, and natural gas, the fossil energy
sources used by humans and maintained for thousands of years are now