Solar thermal energy has the potential to supply a significant fraction of the world’s energy needs if we learn to harness it effectively and to store its energy for use when we have times of high demand. An Australian company has been working on a technology that may be able to do just that. Solar Fusion Power has designed a complete system which can absorb the sunlight during the day and produce continuous, cost competitive, electricity. Its novel design allows for modular configuration for large scale solar power production, in GWatt quantities.
According to the company accomplishing these goals requires the integration of a new solar thermal storage technology which has an energy density factor of 12 times the potassium nitrate/sodium nitrate salt system per kg. The design utilises the heat of formation in Calcium Hydride as a storage medium. Calcium hydride is chosen due to its ability to be broken apart using a thermal heat source, such as the sun. Calcium hydride provides up to 0.90 kW-hr/kg of heat when it converts to calcium and hydrogen.
Hydrogen is stored in a separate low temperature hydride tank. Two heat exchangers are used to extract the thermal energy from the hydrogen before storage in the low temperature hydride. The heat exchangers are required to extract the remaining 20% of the total system energy still in the 1100 C hydrogen before it is cooled to near room temperature.
A central triple walled reaction chamber holds both Calcium and Calcium hydride as liquids between 1000 C and 1100 C. Heat is extracted from the reaction chamber to drive one or multiple 100 kW high temperature Dual Shell Stirling engines operating at 50% conversion efficiency.
The thermal storage costs are substantially lower than a nitrate salt system and reflect both the simplicity of the calcium hydride system and the significant increase in power density. In the calcium hydride system the two liquids, calcium and calcium hydride, remain in the central reaction chamber. Only the hydrogen is pumped between tanks.
The system uses a new low cost wire braced heliostat field with 50 square metres per panel at $100/metre squared in production. The new heliostat configuration eliminates the cosine effect, common with power tower designs, by utilising a parabolic mirror aligned with the sun throughout the day. The parabolic mirror is integrated with a quartz lens and side mirror which provides a 0.1 metre constant diameter focused light beam. The heliostat design has the added advantage of eliminating the power tower and replacing it with a small down mirror located directly above the reaction chamber.
Sunlight is focused through a quartz window, into the reaction chamber, onto an inverted molybdenum cone submerged in the liquid calcium which absorbs the solar energy. Major cost reductions occur due to the use of a down mirror system which allows the power head to be immersed within the reaction chamber inside the liquid calcium. This allows a significant increase in heat transfer capability. An insulated cover is placed between the quartz window and power head at night minimizing thermal losses.
The advantage of this system is that it is a completely reversible closed cycle. The intermittent sunlight can be chemically stored and released at a controlled rate for electric power production. The system uses materials which are low cost and provide a competitive electrical production facility for very large scale application.
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100 kW solar system:
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Tags: power, renewable, solar fusion, solar thermal, Solar Thermal Energy Technology Type, Sun
The energy is stored as electricity or as heat ?
[...] Constant elect night & night from Solar Thermal Solar thermal energy has the potential to supply a significant fraction of the world’s energy needs if we learn to harness it effectively and to store its energy for use when we have times of high demand. An Australian company has been working on a technology that may be able to do just that. Constant Large Scale Electricity from Solar Thermal Energy | Solar Thermal Magazine [...]
[...] Constant Large Scale Electricity from Solar Thermal Energy « Solar … [...]
Great information! I’ve been looking for something like this for a while now. Thanks!