Conducting ink can boost solar thermal by 70% for a few dollars

A nanoparticle ink has been used to coat pipes of solar water heaters to increase their efficiency by up to 70 percent. The new coating was recently proven on the solar heating of a Mexican city sports complex swimming pool, where 2 million cubic meters of water were heated from 26 °C to 37 °C.
Classed as an ink because of its solvent-driven rapid drying time, the material is really a fast-setting paint that is built up in several layers. The internal layer is one of magnetic titanium nanoparticles that trap the heat, the layer above that consists of tungsten nano salt adhered with polyvinyl alcohol, and the whole ensemble finishes with a layer of copper.
"A pipe exposed to the sun reaches a temperature of 40 °C, if we add the superconducting ink the temperature increases 70 percent and reaches 68 °C (154 °F)," says Sandra Casillas Bolaños, master at ITL, and head of the project.
To aid the heating, the outer layer of copper is also burnished to blacken it, so that it heats more rapidly and efficiently in order to trap and hold heat inside the inner particles. "Thus the center is heated more intensely: first the titanium, then tungsten and finally the copper," says Bolaños.
Currently being patented, the conducting ink is slated for market at a price of around 600 pesos (about $US40) a liter. According to Bolaños, however, painting all of the solar water piping in a standard house should cost only around 150 pesos ($10) as the coating goes a long way using very little.