SUNSPOT solar thermal technology package
SUNSPOT is a solar thermal power plant with rock-bed storage, containing a unique set of patented and individually licensable Stellenbosch University technologies. The SUNSPOT cycle is appropriate and efficient for generating, storing and deploying solar power in arid regions.
Most countries today have renewable energy incentive programmes and energy roadmaps to promote the use of renewable energy. Within this context, Concentrated Solar Power (CSP) is an important renewable energy source. For example, China's 13th 5 year plan (March 2016) indicates that they will provide "strong support" for solar thermal energy.
According to Grand View Research, the CSP market size was valued at over USD 3.03 billion in 2016 and is anticipated to grow by 12.7% by 2025.
The SUNSPOT technology package offer various unique characteristics when compared to other CSP solutions - these include cost-effective, simple, easily transportable, and easily deployed heliostats, reducing initial capital costs associated with CSP plants, and low-cost thermal energy storage capacity in the form of rock-bed storage.
The target market for the technologies are Power utility companies and large campus solar thermal developments.
The technology offers the following benefits:
With suitable gas burners or combustors located upstream of the turbine, changes in electrical output due to fluctuations in solar radiation during cloudy or rainy periods lasting hours or even days may be eliminated. By burning additional fuel, turbine temperature and efficiency can be increased to maximize plant output during daily peak power demand periods. Together with a large thermal storage facility the resultant flexibility in the control of power generation that satisfies the demand pattern will essentially eliminate the need to manage sophisticated and costly national power grid or transmission system issues.
By employing local natural rock (e.g. granite) a large low-cost thermal energy storage capacity is made available to act as thermal storage for the hot turbine exhaust gas. Although other storage options employing e.g. molten salts are available, they tend to be relatively expensive and are usually limited to only a few hours of operation. The large rock bed is effective for the entire period from sunset to sunrise. The steam cycle also generates power during the day if some hot turbine exhaust gas is fed directly to the boiler.
Most solar power generating plants will be located in relatively arid regions of the world where an adequate supply of cooling water may not be available. Dry-cooled (air) or hybrid (dry/wet) cooling systems will, therefore, be naturally considered. A novelty of the SUNSPOT cycle is the fact that most of its cooling (condensing steam) is required during the night when ambient air temperatures may be 10°C to 20°C lower than during the day and dry-cooling will be correspondingly more effective. If limited amounts of brackish or wastewater are available, cycle efficiency can be enhanced during the hottest hours by installing a hybrid (dry/wet) cooling system.
1) Patented intelligent heliostat array which is cost-effective, simple, easily transportable, and easily deployed in a wide variety of environments.
2) Patented solar receivers, with combined or separate high & low-pressure options.
3) Patented rock-bed energy storage unit.
4) Optimized plant design with dry/wet cooling.
The technology was developed by the Solar Thermal Energy Research Group at Stellenbosch University. The research group is affiliated with the Centre for Renewable and Sustainable Energy Studies, the national academic hub for renewable and sustainable energy. STERG was one of the first university research groups in South Africa dedicated to solar thermal energy research. Solart Thermal Research at Stellenbosch University dates backs approximately 30 years, when parabolic throughs and collectors were first researched.
STERG is currently managed by Prof Johann van der Spuy and the group coordinator is Dr Matti Lubkoll.