What is concentrating solar thermal power generation?
Concentrating solar-thermal power (CSP) technologies can be used to generate electricity by converting energy from sunlight to power a turbine, but the same basic technologies can also be used to deliver heat to a variety of industrial applications, like water desalination, enhanced oil recovery, food processing, chemical production, and mineral processing.
CSP uses mirrors to focus and concentrate sunlight onto a receiver, from which a heat transfer fluid carries the intense thermal energy to a power block to generate electricity. CSP systems can store solar energy to be used when the sun is not shining.
CSP technologies use mirrors to reflect and concentrate sunlight onto a receiver. The energy from the concentrated sunlight is used to heats high temperature fluid in the receiver.
How solar thermal power generation works – Watch the short video
Concentrating solar-thermal plants are generally large scale, in excess of 5MW (Mega Watts) of generation per plant. The plants are either power tower systems, where the solar reflector mirrors direct solar irradiation to a central tower that acts as the receiver, or linear systems, known as parabolic troughs that concentrate solar irradiation and direct energy to parallel tube receivers positioned above them containing the fluid.
The concentrating solar power tower
In power tower concentrating solar power systems, a large number of flat, sun-tracking mirrors, known as heliostats, focus sunlight onto a receiver at the top of a tall tower.
A heat-transfer fluid heated in the receiver is used to heat a working fluid, which, in turn, is used in a conventional turbine generator to produce electricity. Some power towers use water/steam as the heat-transfer fluid. Other advanced designs are experimenting with high temperature molten salts or sand-like particles to maximize the power cycle temperature.
The Ivanpah Solar Electric Generating System is the largest concentrated solar thermal plant in the U.S. Located in California’s Mojave Desert, the plant is capable of producing 392 megawatts of electricity using 173,500 heliostats, each with two mirrors that focus sunlight onto three solar power towers.
Linear concentrating solar power generation
Linear concentrating collector fields consist of a large number of collectors in parallel rows that are typically aligned in a north-south orientation to maximize annual and summer energy collection. With a single-axis sun-tracking system, this configuration enables the mirrors to track the sun from east to west during the day, which ensures that the sun reflects continuously onto the receiver tubes.
Linear systems may incorporate thermal storage. In these systems, the collector field is oversized to heat a storage system during the day so the additional steam it generates can be used to produce electricity in the evening or during cloudy weather. These plants can also be designed as hybrids, meaning that they use fossil fuel to supplement the solar output during periods of low solar radiation. In such a design, a natural gas-fired heater or gas-steam boiler/reheater is used.
The diagram below shows how the linear solar thermal power plant works, based on the same principle as the power tower, conducting fluid, or molten salt is used to produce steam that in turn drive steam driven power generators that convert the steam energy to electricity which is then exported back to the grid.
To learn more about concentrating solar thermal power generation and the interesting research being carried out to develop the technologies check out the US Government Office of Energy Efficiency and Solar Energy.