Harvesting solar energy for heating/phase change of water.
Localization of solar energy is a promising approach for harvesting solar energy for the heating/phase change of water. However, one of the biggest challenges for further development of this approach is low efficiency of localization. This invention relates to three novel structures that increase efficiency of localization of solar energy.
This invention relates to the development of three novel structures to harvest solar energy for heating/phase change of water. These structures concentrate the solar energy where it is needed and consequently minimize the dissipated thermal energy.
One of these structures is the double layer structure (DLS), which consists of an insulating carbon foam supporting a layer of expanded graphite. The insulating nature of DLS provide a hot spot inside the structure and the hydrophilic nature of the DLS promotes water flow through the capillaries into the hot spot for evaporation.
The second set of structures localizes the solar energy internally for solar heating. This structure consists of a layer of expanded graphite sandwiched between two layers of silica aerogel. The hot region induced in the expanded graphite layer is intended for solar heating. The low surface temperature of the top silica aerogel layer minimizes the energy dissipation by convection and radiation. The thermal efficiency of this system can reach close to 100% by proper design of aerogel layers.
The third set of structures, a hydrophobic absorbing structure, promotes the nucleation of the vapor phase throughout the liquid volume, which significantly enhances the rate of boiling. The threshold concentration of solar energy required for local phase-change is reduced drastically.
- Increased localization efficiency of heat capture