High Efficiency Concentrated Solar Power System

Technology #16037

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hillside-mounted heliostats and receiver at the base of the hill
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Inventors
Professor Alexander Slocum
Department of Mechanical Engineering, MIT
External Link (pergatory.mit.edu)
Professor Jacopo Buongiorno
Department of Nuclear Science and Engineering, MIT
External Link (web.mit.edu)
Charles Forsberg
Department of Nuclear Science and Engineering, MIT
Daniel Codd
Department of Mechanical Engineering, MIT
Managed By
Christopher Noble
MIT Technology Licensing Officer - Clean and Renewable Energy
Patent Protection

Concentrated Solar Power System

US Patent 9,273,883
Publications
Preliminary Optical, Thermal and Structural Design of a 100 kWth CSPonD Beam-down On-sun Demonstration Plant
Energy Procedia, Volume 75, August 2015, Pages 2163-2168
Design of a 100 kW Concentrated Solar Power on Demand Volumetric Receiver With Integral Thermal Energy Storage Prototype
ASME 2015 Power Conference collocated with the ASME 2015 9th International Conference on Energy Sustainability, the ASME 2015 13th International Conference on Fuel Cell Science, Engineering and Technology, and the ASME 2015 Nuclear Forum, July 2015
Experimental Investigation of Divider Plate Assisted Thermocline Storage
ASME 2015 9th International Conference on Energy Sustainability collocated with the ASME 2015 Power Conference, the ASME 2015 13th International Conference on Fuel Cell Science, Engineering and Technology, and the ASME 2015 Nuclear Forum, June 2015
Optimal Design and Operation of a Solar Energy Receiver and Storage
Journal of Solar Energy Engineering, Volume 134, Issue 3, April 2012
Concentrated solar power on demand
Solar Energy, Volume 85, Issue 7, July 2011, Pages 1519–1529

Applications

Concentrated Solar Power (CSP) refers to a method of harvesting solar energy, using an array of mirrors (heliostats) to reflect sunlight onto a heat engine in a central receiver. The heat engine converts the reflected thermal energy into mechanical energy, typically by heating a fluid to power a steam turbine. The technology here proposes a system of heliostats and a ground-based receiver that improves on the overall efficiency of existing CSP systems. 

Problems Addressed

Current CSP systems are highly inefficient for several reasons. Firstly, in order to maximize the amount of sunlight reflected onto the receiver, the receiver must be placed as high off the ground as possible. However this incurs additional construction costs; requires additional energy to pump the fluid to such a height; and incurs additional heat loss as the fluid travels the greater distance. Secondly, CSP systems cannot distribute energy at night. Unfortunately, the current cost of batteries do not make it cost effective for the extra energy harvested during the day to be distributed once the sun has set. Thirdly, the fluids used to store heat can typically only store energy to a certain temperature, wasting the remaining thermal energy.

All of these inefficiencies mean that CSP systems must typically be supplemented by fossil-based energy sources, in order to provide a consistent and sufficient energy supply.

Technology

The current technology addresses these challenges by proposing a system configuration where the array of heliostats is placed on a hillside — the arrangement of which can be determined by this complementary technology (MIT Case 14620) — and sunlight is reflected towards a receiver that is buried in the ground. Elevating the heliostats in such a manner allows the angle between the sun and receiver to be optimized without having to raise the receiver off the ground. 

With the receiver placed in the ground, the system no longer needs to incur additional energy and costs to pump the heat storage medium around — instead, it is fixed in place in a tank, where the ground can serve as an added natural insulator. Additional features of this receiver can also allow it to store thermal energy much more effectively than existing solutions, as detailed in this complementary technology (MIT Case 16038)Instead of a fluid, this receiver can also contain molten salt, the composition of which can be designed to store a greater amount of thermal energy, as detailed in this complementary technology (MIT Case 13251)

Advantages

  • Leverages natural landscape to increase efficiency
  • Allows storage of excess thermal energy
  • Reduces financial and energy cost of circulating a heat storage medium 
  • The overall system is lower cost and more efficient as a result