Concentrating solar power (CSP) has experienced less growth than Solar Photovoltaics. Globally, just 1.5 GW of new CSP capacity became operational from 2015-2017. The United States hasn’t installed any new CSP capacity since September 2015.
Conventional CSP designs use very large plant sizes, with large amounts of thermal energy storage, to leverage economies of scale. This makes eminent sense as a strategy to minimize the cost of generating electricity on a per-kWh basis, but large plant sizes require huge capital investments (>$1B). This limits conventional CSP to only utility-scale markets increases financial risk.
So with CSP falling behind, recently reported work from the National Renewable Energy Laboratory (NREL) and the Colorado School of Mines (CSM) proposes a new kind of approach that radically differs from conventional CSP designs.
Their idea is to shrink down the typical CSP plant size by 1000 times – from 100 MW to 100 kW and use inexpensive materials and passive heat transfer mechanisms to reduce cost. At this smaller scale, they have designed a solar power tower with the entire system, including thermal energy storage and a power block, held on top of the tower.
In their paper, the NREL-CSM team predicts that STEALS would have an annual efficiency of 24%. This includes a higher than usual heliostat field optical efficiency because of its small size (71% on an annual basis), but a lower power block conversion efficiency (30%) because a small scale Stirling engine is lower efficiency than large Rankine cycles.
For more info, go here.
The next step in this new concept development is the construction of a pilot plant to validate the predicted efficiency and operating costs. Is this a paradigm changer? Not yet, but has big potential.
What do you think?