A hybrid photovoltaic-thermal system provides co-generation of electrical energy and thermal energy. Electrical energy is efficiently generated by photovoltaic panels that are cooled by heat exchangers attached thereto, and the cooling of the photovoltaic panels improves the energy output efficiency of the photovoltaic panels. The heat exchangers flow fluid through its channels, and the fluid collects heat from the photovoltaic panels to which the heat exchangers are attached. The heated fluid is then received at and stored in a thermal battery. The thermal battery can be a fluid tank that encourages the fluid to retain the heat collected from the photovoltaic panels. The thermal battery can then supply the heated fluid to thermal loads as thermal energy.

A localized heating structure includes a spectrally-selective solar absorber, that absorbs incident solar radiation and reflects at wavelengths longer than 2 m, with an underlying heat-spreading layer having a thermal conductivity equal to or greater than 50 W/(mK), a thermally insulating layer, adjacent to the spectrally-selective solar absorber, having a thermal conductivity of less than 0.1 W/(mK), one or more evaporation openings through the spectrally-selective solar absorber and the thermally insulating layer, and an evaporation wick, disposed in one or more of the evaporation openings in the thermally insulating layer, that contacts liquid and allows the liquid to be transported from a location beneath the thermally insulating layer through to the spectrally-selective solar absorber in order to generate vapor from the liquid. The thermally insulating layer is configured to have a density less than the liquid so that the localized heating structure is able to float on the liquid.