Expect to see a solar PV panel on the north-facing surface of every building in the future.

The rapidly falling cost of converting sunlight into electricity means it's just a matter of time before solar power generation is part of the structure of new buildings.

At the same time, the development of new photovoltaic materials for turning photons into electrons is increasing the range of ways the sun's energy can be harnessed.

Justin Hodgkiss, a solar energy researcher who divides his time between Victoria University and Wellington's MacDiarmid Institute for Advanced Materials and Nanotechnology, says in some parts of the world solar power is as cheap, or cheaper, than coal and gas generation.

"That's not the case in New Zealand yet but in some sunnier places it has already achieved parity or better," Hodgkiss says.


"If you look at a graph of prices over the past 20 years, they've been tumbling year after year, and the drop in the past two or three years has been incredible."

From 2009 to 2012, the cost of photovoltaic generation went from US$4 a watt to US$1. He estimates the price has halved again since then.

That's a consequence of improved manufacturing processes and materials and production that has been stimulated by government subsidies.

"China has jumped into green tech and is outpacing the rest of the world in manufacturing. That's been a huge contributor to lower prices."

And there's no sign of any let up. Hodgkiss says work taking place in development labs such as the MacDiarmid Institute promises big advances to come.

In particular, UK researcher Henry Snaith of Oxford Photovoltaics is reportedly close to achieving efficiency similar to that of orthodox silicon solar cells using a thin-film material called perovskite.

Perovskite is an abundant mineral (calcium titanium oxide) which is less expensive than silicon (the most common material used in PV panels). Whereas conventional silicon cells require silicon layers of approximately 180 microns, perovskite is capable of absorbing the same amount of light in just a few microns.

A report in the MIT Technology Review says: "Researchers developing the technology say that it could lead to solar panels that cost just 10 to 20 cents [US] per watt."


The upper end of silicon solar cell efficiency is about 20 per cent, meaning about a fifth of the sun's energy is converted to electricity.

The perovskite solar panels, about three microns thick, is a see-through, coloured glass film which can be printed onto windows and raises the cost of installation just 10 per cent.

Hodgkiss says the benefit of perovskite photovoltaics is that it is high performance and simple to make.

"It has great absorption, great conduction and is easy to manufacture," he says.

"That means in areas of the world where solar photovoltaic generation is marginally affordable it will become really affordable and displace other sources of electricity."

Perovskite photovoltaics also has the potential to be applied to flexible materials.

Hodgkiss says solar power is already making inroads in parts of Africa that the electricity grid doesn't cover, in a way similar to the spread of cellular phone services to areas that never had landlines.

With a supplier distributing panels at no cost, villagers are tapping into the solar power with prepay cards, in a further parallel with mobile phones.

"It's cheaper than buying kerosene for lighting, which they traditionally have done."

In the developed world, Germany demonstrated its lead in adoption of solar power by reaching the milestone on May 11 of generating three-quarters of its electricity from renewable sources.

Thanks in part to Germany's heavily-subsidised photovoltaics uptake, China has built a substantial solar panel manufacturing industry. It is also installing solar generation at a rapid rate.

According to Businessweek, China aims to triple solar generation by 2017 to 70 gigawatts - about eight times New Zealand's total generating capacity.

A US initiative to pave roads with solar panels, meanwhile, has captured the public imagination raising roughly double its funding target of US$1 million on crowdsourcing website Indiegogo.

Scott and Julie Brusaw's Solar Roadways scheme will not just generate electricity, but also provide lighting and heat to keep roads clear of ice and snow.

Hodgkiss says satellite maps show roads and roof tops make up about the same area of a typical city, giving Solar Roadways' idea significant potential.

"I think photovoltaics will be very widespread around the world in the next three to five years. It won't be considered a novelty in new buildings - it will be a no-brainer in terms of building cost-effectiveness."

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