How LPT Works

BrightSource’s LPT solar thermal technology generates power the same way as traditional power plants – by creating high temperature steam to turn a turbine. However, instead of using fossil fuels or nuclear power to create the steam, BrightSource uses the sun’s energy.

BrightSource’s LPT solar thermal system uses proprietary software to control thousands of tracking mirrors, known as heliostats, to directly concentrate sunlight onto a boiler filled with water that sits atop a tower. When the sunlight hits the boiler, the water inside is heated and creates high temperature steam. Once produced, the steam is used either in a conventional turbine to produce electricity or in industrial process applications, such as enhanced oil recovery (EOR). In order to conserve precious desert water, the steam is air-cooled and piped back into the system in a closed-loop process.

Heliostats

Our tracking mirrors, known as heliostats, are highly engineered and designed for accuracy, durability and longevity with minimal maintenance. The heliostat consists of two flat glass mirrors (supported by a lightweight steel support structure) that are mounted on a single pylon equipped with a computer-controlled drive system. This control system enables the heliostats to track the sun in two-directions, maximizing the collection of the sunlight while accurately aiming at the solar receiver. In the current system design, a 130 MW plant will utilize up to 60,000 heliostats, depending on land area and shape, and site-specific considerations. The low-impact design of the heliostat allows our solar plant sites to accommodate a slope of up to 10%, avoid areas of sensitive habitat and eliminate the need for the concrete pads used with other solar thermal technologies, reducing the system’s environmental impact.

Solar Field Optimization Software and Control System (SFINCS)

BrightSource’s proprietary solar field optimization software is used during the system design phase to determine the optimal position of each heliostat to maximize output and meet the customer’s power production profile. The technology also provides considerable design flexibility, allowing projects to be built on sites with irregular topographies and shape. Using actual site conditions and custom-built meteorological datasets, the software produces precise GPS-ready mappings ready for download to solar field installation crews.

Our proprietary heliostat control software system, the Solar Field Integrated Control System (SFINCS), controls the heliostats arrayed in the solar field to track the sun and aim the sunlight onto the receiver. SFINCS performs a number of functions including:

  • Solar energy management, to focus the ideal amount of solar energy on the receiver at various times of the day to maximize electricity production while ensuring that the solar receiver’s flux and temperature limits are not exceeded.
  • Solar field control, to provide aiming points on the solar receiver surface for each individual heliostat, as well as facilitating start-up and shutdown.
  • Heliostat tracking maintenance, to calibrate the heliostats based on three-dimensional laser scanning and other photogrammetric methods.

At the core of the SFINCS are our proprietary algorithms that perform real-time optimization of the distribution of energy across our solar receiver using real-time, heliostat-aiming and closed-loop feedback systems. In addition, SFINCS can automatically configure the heliostats to protect them from inclement weather.

Solar Receiver (Boiler)

The solar receiver is a standard utility-scale industrial boiler designed to be heated from the outside using concentrated solar radiation reflected onto the boiler by the heliostats. The boiler is designed to withstand the rigors of the daily cycling required in a solar power plant over the course of its lifetime, and is treated with a proprietary solar-absorptive coating to ensure that maximum solar energy is absorbed in the steam.

In electricity generation applications, the high-temperature, pressurized steam generated in the solar receiver is piped to a conventional steam turbine generator. The electricity generated is then delivered to the transmission grid for consumption.

In a solar-to-steam application, such as thermal enhanced oil recovery, the process is similar to generating electricity. However, for solar-to-steam applications, saturated steam is piped from the receiver to a heat exchanger to generate the process steam.

Storage

BrightSource’s SolarPLUSTM combines the company’s high-efficiency LPT solar thermal technology with proven two-tank molten-salt storage.

In BrightSource’s SolarPLUSTM plants, a portion of the steam produced in the boiler is directed to a heat exchanger, where molten salts are further heated to a higher temperature, thus efficiently storing the heat energy for future use. Later, when the energy in storage is needed, the heat stored in the molten salts is used to generate steam to run the steam turbine.

The benefits of BrightSource’s SolarPLUSTM plants include:

  • Extending the production of electricity into later parts of the day and after the sun sets when it is most valued by utilities.
  • Reducing the cost of renewable power for utilities’ customers by increasing a plant’s capacity factor and offering higher efficiencies than competing solar thermal power plants.
  • Providing utilities with greater operational flexibility to shape production to meet changing utility customer demand.
  • Offering utilities and grid operators additional operational and market value, by providing balancing and shaping capabilities, as well as ancillary services to support a reliable grid.