High-Temperature Direct Absorption Research

The Solar Energy Research Institute (SERI) is conducting research for high-temperature solar thermal receivers. A molten salt can serve as both the receiver heat transport and the thermal storage medium. Molten carbonates are the primary candidate salts for applications requiring temperatures of 850 degrees C (1562 degrees F) or higher. The receiver absorbs concentrated solar radiation directlyon a salt film flowing down a wall in a cavity. This research has shown that depending on the receiver design, laminar, transition, or turbulent flow may be present. The heat transfer characteristics depend on both the optical properties and the film thickness. Predictions of molten-salt film thickness indicate a substantial variation in film thickness between flow regimes. A device has beenconstructed that can be used to verify the predictions and to provide data at low temperatures where none currently exist. Mathematical models of the heat transfer process in clear and blackened salts have been developed for both laminar and turbulent flow regimes. Blackened salts are preferred, but clear salts can also be employed.