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Image of a square parabola. (a) Image from caustics with 3600 rays. (b) Image from SolTRACE with 10000 rays. (c) Superposition of (a) and (b).
Source publication
Solar thermal power generation is based on the concept of concentrating solar radiation to provide high temperature heat for electricity generation via conventional power cycles. The high relative cost of optical subsystems necessitates a careful study of their components. The capital cost of the heliostat field in central receiver power plants is...
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Citations
... These codes aid in the optical characterization but are not suitable for field layout optimization. The second category uses an analytical approach, where rays carry error cone information and the flux distribution is estimated using convolution of the Gaussian distribution functions [9]. The codes, UHC [10], DELSOL3 [11] and HFLCAL [12] are examples of this category. ...
South Africa has implemented a ‘time of day’ tariff structure for concentrating solar power plants in the Renewable Energy Independent Power Producer Procurement Programme. It is hypothesised that payment allocation factors for the ‘time of day’ and the ‘time of use’ dispatch schedule influence the optimal heliostat field layout. SolarPILOT software is used to generate and optimize the heliostat field layout of a 100 MWe power tower plant in Upington, South Africa with 8 hours of thermal energy storage in the SunShot scenario with a high receiver thermal efficiency of 90%. A large size heliostat with a total area of 115.56 m² and an external cylindrical receiver are considered for the heliostat field layout. A subset of 12 days is simulated on an hourly basis to achieve convergence and to take seasonal, daily and hourly weather variability into account. During the optimization of a heliostat field layout, the heliostats are ranked and selected according to a performance metric. In this study, two field layouts are compared based on two different performance metrics, namely: power delivered to the receiver and the time of use weighted power. The optical performance is simulated using both the Hermite (analytical) and the Monte-Carlo Ray-Tracing methods. By accounting for the TOU weighted power, it is found that the LCOE increases from 0.1831 $/kWh to 0.1870 $/kWh using the Hermite (analytical) method. Similarly, when MCRT techniques are used for the optical characterization, the LCOE value increases from 0.1781 $/kWh to 0.1832 $/kWh. It is recommended that payment allocation factors and the tariff structure for the time of day be included when comparing field layouts with other layout generation and optimization strategies. This study will be useful for power tower developers in identifying practices to be included in the optical characterization of their heliostat field layouts for better simulation results.
... These codes aid in the optical characterization but are not suitable to quickly generate and then optimize the field layout. The second category uses an analytical approach, where rays carry error cone information and the flux distribution is estimated using convolution of the Gaussian distribution functions (Georgiou et al., 2013). ...
Heliostats typically contribute to about 40 % of the total installed costs in a concentrated solar power (CSP) tower plant. The objective of this study is to investigate the effects of heliostat size on the levelized cost of electricity (LCOE). These effects are analysed in a power tower with a net capacity of 100 MWe with 8 hours of thermal energy storage in Upington, South Africa. A large, medium and a small sized heliostat with a total area of 115.56 m2, 43.33 m2 and 16.69 m2 respectively are considered for comparison. The heliostat cost per unit is calculated separately for the three different heliostat sizes and the effects due to size scaling, learning curve benefits and the price index is considered. The annual operation and maintenance (O&M) costs are estimated separately for the three heliostat fields, where the number of personnel required in the field is determined by the number of heliostats in the field. The LCOE values are used as a figure of merit to compare the different heliostat sizes. The lowest theoretical LCOE value of 0.1960 $/kWhe is achieved using the medium size heliostat with an area of 43.33 m2 for this power tower configuration.
