Romanian startup Photovoltaic Windows has developed an off-grid hot water system that uses cadmium telluride (CdTe) photovoltaic semi-transparent glasses. It claims a 0.7 kW pilot installation on an apartment balcony in Bucharest yielded annual savings of €1,100 ($1,202).
CdTe thin film PV glass is manufactured by China’s Advanced Solar Power (ASP) and is available in 10% to 90% films. A 90% transparent glass has a nominal power of 8 W, while a glass with 10% transparency has a nominal power of 76 W. The dimensions of the PV glass are 1200 mm x 600 mm x 7 mm, an area of 0.72 square meters and a weight of 12 kg. The temperature coefficient is -0.214% per degree Celsius and the operating temperature is -40 C to 85 C.
“Depending on the available surface area, direction, location and the chosen degree of transparency, these systems can produce more than half of the warm domestic water needed for a year by a family of 3-4,” PVW administrator Adrian Baisan said. pv magazine. “The operating principle of such systems is based on the fact that the resistors (heaters) work equally well with direct current (from the solar electric windows) or alternating current (from the grid), he explained. “This eliminates the need to change the current produced by the solar electric windows into alternating current, as long as the solar electric system does not cover the need for hot domestic water.”
The company completed a pilot installation on the balcony of a high-rise apartment building in Bucharest last December. The project was developed in two phases. The first stage included 3 different colored and transparent PV glasses and one small 15 liter/1.2 kW water heater. In the second phase, 11 PV glasses were added, of which nine with 30% transparency and two with 10% transparency, as well as one hot water heater with an output of 80 liters/3 kW.
“A system with an installed power of 0.7 kW would provide a total annual economy of around 1,100 euros per apartment (for Bucharest), equivalent to the economy generated by a 3 kW to 4 kW system installed (in a rooftop installation of an apartment),” said Fuck it. “This is due to preventing the waste of hot water that is natural for those living on the upper floors (of the apartments), as well as reduced electricity consumption thanks to the use of solar windows.”
The integrated automatic regulator opens up the possibility of heating water with electricity from the grid when solar electricity is not available, even if the system would then have to be connected to the grid.
According to Baisan, the pilot installation has gone as expected. He found that south-facing windows are the most efficient, while east- or west-facing windows produce about 70% of the energy of south-facing windows. Systems installed in the far north of Romania would produce about 5% less energy than in the southern part of the country.