By Richard Black

Environment Correspondent, BBC News website



"It feels very good," says Lynn Stevenson. "We like it; it's like we're in control and managing something."

Solar and wind rooftop generation plant at the Stevenson house

I am standing with Lynn and husband Chris in the shed outside their newly built house in Robertson, New South Wales, 150km (100 miles) from the hustle and bustle of Sydney.

The "something" they are in control of sits on the roof above our heads; a swathe of solar panels, book-ended by two small wind turbines on six- metre (yard) poles.

"All our power is run by solar and wind energy," says Lynn, "and we're learning how to manage that and how it works in our house.

"You do learn to manage just how much power you're using in the house," adds Chris. "You probably can't turn on an electric jug and a toaster at the same time.

"We do find if we have a long run of dull weather we do have to start the generator and top up the batteries; but most of the time it powers the house."

Bottom line

All our power is run by solar and wind energy; it feels very good

Lynn Stevenson

Yet according to the International Energy Agency, if you take large-scale hydro projects out of the equation, only about 2% of the world's electricity is generated through solar, wind and other renewable technologies.

The reason is simple: cost. If there is a grid connection available, it is almost always going to be cheaper to connect; and with few exceptions, such as Iceland with its generous provision of geothermal energy, the cheapest source of electricity going into the grid is likely to come through burning fossil fuels.

But when you go into the isolated communities and individual homesteads which Australians have sprinkled across their giant landmass, the cost equation becomes radically different.

"If you are connected to the grid in Australia you pay 14 cents (10 US cents) per kilowatt hour (kWh)," says Bruce Hanton, an energy consultant working for the installation company Delta Electrics in Darwin, capital of Australia's most sparsely populated region, the Northern Territory.

A stand-alone community solar system can cost A$500,000

"A stand-alone solar system is closer to a dollar (74 US cents) per kWh. But people in remote areas have to weigh up the costs of having a diesel generator, supplying diesel fuel, maintaining the generator; plus the wet season cuts you off for up to six months of the year."

Some of the large systems Mr Hanton has installed carry a capital cost of A$500,000 (US$375,000); but, he says, against the diesel alternative, they can pay for themselves in 4-6 years.

Slow march

A typical stand-alone system in remote Australia contains five main components:

something to generate the electricity, usually solar panels but possibly a wind turbine or a small hydro unit

with solar panels come a solar regulator to prevent overload

batteries to store electricity

an inverter to convert the direct current, low-voltage output into an alternating current, mains-voltage supply which ordinary appliances can use

typically, a diesel generator as back-up

If engineers from several decades ago visited the present, says Bruce Hanton, they would find little different about today's systems.

"Certainly your solar modules are getting slightly more efficient, batteries are getting slightly better, but the basic technology is still exactly the same."

You could supply all of the world's energy needs by covering 4% of the world's desert area with photo-voltaic panels

Martin Green

"Technically you could supply all of the world's energy needs by covering 4% of the world's desert area with photo-voltaic panels," says Martin Green from the Advanced Silicon Photo-voltaics and Photonics research centre at the University of New South Wales in Sydney.

"So there's plenty of land available, and plenty of sunlight available."

Yet according to International Energy Agency forecasts, renewables (once again excluding large-scale hydro) will make up only 6% of the world's energy economy in 2030, with solar cells contributing a small fraction.

It is an improvement on today's 2%, but hardly a ringing endorsement of their potential.

The problem is that solar cells convert only about 15% of the sunlight they receive into electricity; at these rates, it is not generally an economic technology.

Martin Green's research unit is in the vanguard of those trying to improve performance and bring down prices.

In the lab, his team can achieve sunlight-to-electricity efficiencies of 25% and intends to go higher, through using materials other than the conventional silicon wafer, or by stacking cells in layers which each absorb different components of the Sun's radiation.

Costs are tackled through investigating cheaper forms of silicon or cheaper ways of processing it; while on the horizon are organic cells, not very efficient, but cheap and easy to make.

One day, perhaps, entire buildings could be swaddled in layers of organic photo-voltaic wrap.

Scaling up

Next-generation solar cells could cover windows and entire buildings

"There's a well-demonstrated history of cost reductions in photo-voltaics; every doubling of the amount produced brings the cost down to about 80% of what it was before that doubling," he says, "and that's gone on for about 30 years.

"So if you can maintain that trend, you can work out how many systems you need to install to get them to a price where they'll be competitive with what else is there, and it's perhaps just a 100 times more we need to manufacture than what's been manufactured up to the present."

The German government certainly believes in this theory. It has instituted a whole raft of financial incentives designed to boost solar installation; more than 10% of the nation's electricity now comes from renewable sources, and the government believes that ramping-up production will bring costs down.

Back in Robertson, New South Wales, the Stevensons are happy to be pioneers for a carbon-free solar future.

"We're not contributing to the effects of thermal power and the greenhouse effect," says Chris.

Just one more reason, then, why life under the Australian sun feels so good.

Richard.Black-INTERNET@bbc.co.uk