In Concentrated Solar Power (CSP) systems, thermal energy from the sun is reflected onto a central receiver, which stores the energy in a heat storage medium. The technology described here proposes a more efficient design for such a receiver. Specifically, this receiver can be used as a ground-based receiver in conjunction with this technology for a High Efficiency Concentrated Solar Power System (MIT Case 16037) — but it can also be used in other CSP systems in general.
CSP systems are currently designed to concentrate thermal energy onto a small area, which is termed as the receiver. A heat storage fluid is then pumped through this area — absorbing the thermal energy as it passes through — then the heated liquid is pumped to a heat engine (such as a steam turbine) which converts the thermal energy into mechanical energy. In such a design, much of the thermal energy is lost as the fluid moves through the system. Additional energy is also required to pump this fluid around. Furthermore, the fluid can typically only store energy up to a certain temperature, wasting the rest of the thermal energy directed to it. The current technology reduces these inefficiencies by modifying the design of the receiver.
A receiver is proposed that contains the heat storage medium in a large tank. The concentrated thermal energy impinges on this medium through an aperture in the receiver — either by shining directly onto the surface, or by being reflected onto it via a reflective interior of the container. This aperture can be closed (either by using a physical cover or an air curtain) to reduce heat loss during periods where the sun is not shining, or to protect the medium from contamination during dust storms. The heat storage medium would only be pumped away to a heat engine when necessary for energy production, thus reducing the thermal energy loss. This complementary technology (MIT Case 13251) proposes a type of molten salt which can be an effective heat storage medium.
When the hot medium from the surface is pumped away to the heat engine, the layer below is exposed to store additional thermal energy. After being relayed to a heat engine, the cooled medium is then pumped back to the bottom of the container to replenish it. A divider plate is used to separate these regions of hot and cold medium (the position of which can be controlled using actuators or buoyancy), so as to preserve the thermal energy in the hot region. The respective hot and cold mediums can also be mixed to improve their heat storage capacity, which can be achieved by adding a convection actuator to the container, or designing a gap into the divider plate to promote mixing as it is moved.
- Reduce energy loss from the heat storage medium, improving the efficiency of a CSP system
- Reduce the cost of pumping the heat storage medium around