Solar windows could cut building energy use by half

Ideas for generating electricity from the massive curtains of windows that adorn modern buildings are coming thick and fast. Justin Norrie from The Conversation wrote about one idea last week that we published, Dyesol is continuing its developments with Pilkington in the US, and industry researcher NanoMarkets recently identified 20 firms pursuing similar technologies.

Another one to watch is the development at Edit Cowan University in Western Australia of solar windows that are apparently cheap to make and could reduce a building’s energy needs by nearly 50 per cent. And, while most Building Integrated Photovoltaic solutions offer less than 50 per cent transparency, this technology lets all the light through.

The technology has been developed by a team led by Professor Kamal Alameh, the director of the Electron Science Research Institute (ESRI) at ECU, who claims to have harnessed the optical properties of nano-particles to develop a breakthrough in electricity- generating window panes.

Rather than using tinted film on the surface of the glass, or sandwiched between two layers, Alameh’s team has placed a continuous layer of nano-particles between two sheets of glass. These nano-particles allow visible light waves through but prevents the entry of both ultra violet and infrared light, which is instead re-directed to the edge of the window pane, where it is collected by photovoltaic cells built into the window frame and converted into electricity.

Alameh’s team says the costs of the materials are quite minor, and the sheets of glass (6mm) are standard. According to Victor Rosenberg, the CEO and chiamran of Tropiglass, which is seeking to commercialise the technology, the conversion rate from infrared light to electricity is more than 10 per cent, so each square metre of glass will be able to generate 50 watts of electricity, or a total of $16 a year. This translates into around 500MWh a year for a 30 storey building.

Rosenberg says the fact that the technology does not reduce the amount of visible light that enters the building, and absorbs some of  the heat while at the same time generating electricity, means that air conditioning and lighting costs of the building could be reduce by at least 40 per cent, possibly as much as half.

‘This technology is probably a world first,” Rosenberg told RenewEconomy. “Almost all buildings now are made of curtains of glass. This allows us to squeeze more electricity out of it.”

Rosenberg says the technology has already sparked the interest of Viridian, the glass-making subsidiary of building materials group CSR, and French construction giant St Gobain. Both companies will inspect the technology at ECU this month, where a 20cm by 20cm pane is operating.

Solar window technologies are a key-part of BIPV, which is expected to be the hot new market for solar technologies. It is estimated that the BIPV glass market will rise five-fold to more than $6 billion over the next five years. Building account for around 40 per cent of global emissions, according to estimates, much of it from air conditioning, elevators, lighting and the like.

“We see a growing role for BIPV to satisfy building codes that call for zero-energy buildings,” a report by NanoMarkets said. “By spreading costs across both the building energy system (or part of it anyway) and the building fabric, it becomes possible to create a new economics for PV that – at the very least – will increase the size of its addressable market.”

The International Energy Agency went further in a report last year. It BIPV offers the possibility that a thin layer of PV-active material will become almost a standard feature of building elements such as roof tiles, façade materials, glasses and windows, just as double glazed windows have become standard in most countries.

“With very large scale mass production, and support elements having a primary role in building support or closure, the cost of PV would almost vanish in the market segment where it currently costs the most.” That’s an attractive proposition for companies such as and researchers at ECU and elsewhere.