Available Technology

Improved Concentrating Solar Power Systems

Concentrating Solar Power (CSP) systems utilize solar energy to drive a thermal power cycle for the generation of electricity. CSP technologies include parabolic trough, linear Fresnel, central receiver or “power tower”, and dish/engine systems. Considerable interest in CSP has been driven by renewable energy portfolio standards applicable to energy providers in the southwestern United States and renewable energy feed-in tariffs in Spain. CSP systems are typically deployed as large, centralized power plants to take advantage of economies of scale. A key advantage of certain CSP systems, in particular parabolic troughs and power towers, is the ability to incorporate thermal energy storage. Thermal energy storage (TES) is often less expensive and more efficient than electric storage and allows CSP plants to increase capacity factor and dispatch power as needed – for example, to cover evening or other demand peaks. Current CSP plants typically utilize oil, molten salt or steam to transfer solar energy from a solar energy collection field, tower or other apparatus to the power generation block. These fluids are generally referred to as a “heat transfer fluid” and are typically flowed through a heat exchanger to heat water to steam or to heat an alternative “working fluid” which is then used to drive a turbine and generate electrical power. Commonly utilized heat transfer fluids have properties that in certain instances limit plant performance; for example, synthetic oil heat transfer fluid has an upper temperature limit of 390°C, molten salt has an upper temperature limit of about 565°C while direct steam generation requires complex controls and allows for limited thermal storage capacity. Current state-of-the-art two-tank molten salt storage costs are relatively high, and impose temperature limitations upon a practical system. For example, a typical two-tank molten salt storage system will freeze at temperatures under 200°C and become unstable above 600°C. Proposed single-tank thermocline TES systems have the potential to displace 75% of the expensive molten salt with low cost rocks or pebbles. Even so, the cost of a thermocline TES system will still be high due to the cost of the remaining 25% salt or other required elements such as a stainless steel tank. In addition, molten salt may still limit the highest operating temperature of the overall CSP system for the power generation and thereby limit system efficiency. In addition, TES salt transportation and conditioning can take several months, which negatively impacts capital investment. In contrast to a molten-salt CSP system, highly stable solid particles can be stable at temperatures beyond 1000 °C, thus able to drive high efficiency thermal power cycles for high solar-to-electricity conversion efficiency. The particle-thermal system can support one of the promising high-efficiency s-CO2power cycles. Sand-like solid particles are ordinary materials that are vastly available and can be processed inexpensively to be used in the particle-CSP system. Our patented designs are able to achieve high thermal performance, and lead to a low-cost, high-performance CSP system with the large-scale energy storage to serve for dispatchable power generation.
Patent Abstract: 
Concentrating Solar Power (CSP) systems utilize solar energy to drive a thermal power cycle for the generation of electricity. CSP technologies include parabolic trough, linear Fresnel, central receiver or “power tower”, and dish/engine systems. Considerable interest in CSP has been driven by renewable energy portfolio standards applicable to energy providers in the southwestern United States and renewable energy feed-in tariffs in Spain. CSP systems are typically deployed as...
Benefits 
Simplified systems -Low system cost by using inexpensive, stable solid particles -Reduced installation, maintenance and operation costs -Increased efficiency with the high-temperature ability to drive advanced power cycles
applications 
Internal Laboratory Ref #: 
NREL ROI 11-92, 12-40, 14-72 -Proposed -Available -02/17/2016 -02/17/2016
Lab Representatives
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