5.3 Summary

The variability of CST plants was discussed in this chapter and compared with variations observed in PV plants. CST plants can essentially be considered to have better capability of riding through cloud transients. This is evident when looking at partly cloudy day output profiles: the variability of PV plants is seen to be far greater than for CST plants. The reason is that some storage is inherent in all CST systems, simply through the thermal mass of the working fluid and broader system, even if there is no major storage element included. Some advantages of CST systems over PV systems, and vice versa, are listed in Table 8.

Table 8 Features of CST plants versus PV plants

Advantages of CST plants Advantages of PV plants
CST projects are inherently capable of more accurate forecasts than PV plants as they are more independent of the variability of weather conditions. PV systems do not necessarily require new land for their installation and can utilise building rooft ops.
CST plants are able to utilise backup fossil fuel generation and thermal energy storage (TES) to increase their capacity factor. Distributed PV can be located close to loads, resulting in reduced line losses. Installations of PV systems may help defer required upgrades to existing electrical infrastructure.
CST plants are able to respond to system operator instructions in a similar manner to conventional units and are more capable than PV to provide ancillary services. Installing a small-scale PV system does not need large amounts of capital or extensive studies to determine its feasibility as a CST system does. This makes it more likely that the installation will go ahead.