Researchers at the Technological Institute of the Lagoon (ITL), Mexico, have created a nanoparticle-rich, superconducting ink that they have 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 (70.6 million cubic feet) of water were heated from 26 °C to 37 °C (79 °F to 98°F).

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 (104 °F), 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.

This technique is so efficient, the researchers claim that where the material has been applied in some houses, water flowing for just five meters (16 ft) through the ink-treated pipe reaches 68 °C (154 °F) almost instantly. Even in overcast weather, the ink is also asserted to capture heat much more efficiently than un-treated systems.

Currently being patented, the superconducting 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.

Bolaños says that the point of difference between her team’s material and other coatings coming to market, is that the others use much more expensive metals than the tungsten the ITL team uses, meaning that theirs will come in around 40 percent cheaper.

The final hurdle is to replace the current step-by-step process of fine-tuning the nanoparticle layer and optimize its creation to allow production in greater volumes.