Solar Balcony Windows Cover Nearly Half a Bucharest Family’s Hot Water for Two Years

Semi-transparent photovoltaic glazing on a south-facing balcony in a Romanian apartment block has supplied a significant share of a four-person family’s hot water across two full years, pointing to a low-complexity alternative to chemical battery storage.

The 12.9-square-metre balcony carries panels with a combined rated capacity of 845 W. Instead of routing electricity through an inverter, the system feeds direct current straight to an ordinary electric water heater. No surplus is exported to the building grid; when solar output drops after sunset, a controller automatically switches the appliance to the AC mains.

Over the first year the panels produced 446 kWh, meeting 46.7 percent of the household’s hot-water demand. Output edged up to 462 kWh in the second year, covering 43.7 percent.

A central technical argument for PV glazing over standard balcony modules is voltage compatibility. Two conventional balcony panels totalling 800 W, connected directly to a 3 kW heating element, transfer only around 300 W because their current characteristics do not match the load. PV window cells are smaller and more numerous, achieving a DC voltage better suited to direct resistive heating; peak power measured at the Bucharest heater reached 499 W. The glazing also reduces summer solar heat gain through the balcony by 40 percent.

On-site water heating eliminates a hidden water loss: the family previously had to run the building’s central supply for roughly five minutes before hot water arrived, draining an estimated 62 cubic metres annually. Storing heated water inside the apartment removes that wait and the associated waste.

Source: CleanTechnica