Unformatted text preview: lopment of low cost heliostats.
Dish/engine systems require the development of at least
one commercial engine and the development of a low cost
concentrator . Table 5.1 highlights the key features of the three solar technologies.
Parabolic Dish/Engine Power Tower Size 30-320 MW 5-25 kW 10-200 MW Operating Temperature
750/1382 565/1049 Annual Capacity Factor
Annual 23-50 %
23-50 25 % 20-77 % Peak Efficiency 20%(d)
29.4%(d) 23%(p) Net Annual Efficiency
11(d)-16% 12-25%(p) 7(d)-20% Commercial Status Commercially Scale-up
Prototype Demonstration AvailableDemonstration
Development Low High Medium Storage Available Limited Battery Yes Hybrid Designs Yes Yes Yes Cost USD/W 2,7-4,0 1,3-12,6 2,5-4,4 (p) = predicted; (d) = demonstrated; Table 5.1 Key features of the three solar technologies . 6. Calculations
Heat from a solar collector may be used to drive a heat
engine operating in a cycle to produce work. A heat
engine may be used for such applications as water
pumping and generating electricity.
The thermal output Qout of a concentrating collector
operating at temperature T is given by
Qout = F'[gamma.Ainqin - U.Arec(T - Ta)],
Ain : the area of the incident solar radiation (m2). Arec : the area of the receiver (m2)
qin : the incident solar irradiation (W/m2)
Ta :the ambient temperature (°C)
U :the heat loss coefficient (W/m2K)
F’ :collector efficiency factor
The quantity Ain/Arec is called the concentration ratio.
concentration High concentration ratios are obtained by making Ain the
area of a system of mirrors designed to concentrate the
solar radiation received onto a small receiver of area Arec.
Heat losses from the receiver are reduced by the smaller
size of the receiver. Consequently, high concentration
ratios give high collector temperatures. The...
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- Spring '14
- ........., Concentrating solar power, power tower