Page 126 - Design of Solar Thermal Power Plants

112 2. THE SOLAR RESOURCE AND METEOROLOGICAL PARAMETERS

(such as mist and raindrops) on optical waves. The visible light band
(0.38e0.77 mm) is influenced by the atmospheric window in which at-
mospheric absorption is insignificant. Radiation attenuation within this
band is mainly caused by the scattering effect of atmospheric molecules
and aerosol particles.
1. The structure and constitution of the instrument consists of the
optical transmitter-receiver-integrated machine, electrical box, and
software. It is used to measure the transmittance of light under
various circumstances, road visibility under different climatic
conditions, and the tunnel smoke concentration inspection index.
2. Installation and maintenance of the instrument is quite simple; it
only needs to be placed at the location to be measured.
Considering that the testing environment might be adverse, some
instruments have been equipped with internal memories and some
even with a data-processing function for indicating either measured
values at different time points or mean value within a certain period.
Data display: Light transmission rate (%), smoke concentration (L/m),
visibility (m).
Testing error: 2%, light transmission rate.
Ambient air temperature: 50 to 65 C; ambient humidity: 0%e100%

(relative humidity); whole-machine mass: about 10 kg.

2.10 GLOBAL DIRECT NORMAL IRRADIANCE
DISTRIBUTIONS

2.10.1 Site Adaptation of Satellite-Based Direct Normal
Irradiance
Satellite-derived solar radiation data can be used where ground-based
measurements are not available. Satellites measure reflected radiation
from Earth’s surface in several wavelength bands. Known albedo values
by location, complex model, and algorithm can be used to determine
global, diffuse, and direct-beam irradiance components. Site adaptation of
satellite-based DNI is necessary for bankable DNI data in CSP projects.
One of the best–known data sets is provided by NASA (http://eosweb.
larc.nasa.gov/sse/). Another popular satellite-based DNI provider is
Solargis (http://solargis.com). Some introductions of Solargis is dis-
cussed in the webpage (https://doi.org/10.1063/1.4949234).

2.10.2 Global and District Direct Normal Solar Irradiation
Distributions
Many Sunbelt countries within 40 degrees of the equator are rich in
solar resources, and the long-term average annual total direct normal