Localized solar collectors

A localized heating structure for use in solar thermal systems, the structure comprising:

• a spectrally-selective solar absorber configured to absorb incident solar radiation and to reflect at wavelengths longer than about 2μm, with an underlying heat-spreading layer having a thermal conductivity equal to or greater than about 50W/(mK);
• a thermally insulating layer adjacent to the underlying heat-spreading layer in the spectrally-selective solar absorber, such that the heat-spreading layer is between the thermally insulating layer and the spectrally-selective solar absorber, the thermally insulating layer having a thermal conductivity of less than about 0.1W/(mK);
• at least one or more evaporation openings extending through both the spectrally-selective solar absorber and through the thermally insulating layer;
• and
• an evaporation wick disposed in one or more of the evaporation openings in the thermally insulating layer, the evaporation wick configured to contact liquid and to allow 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 localized heating structure configured to allow the vapor to escape through the at least one or more evaporation openings in the spectrally-selective solar absorber, the thermally insulating layer configured to have a density less than the liquid so that the localized heating structure is able to float on the liquid.