In the last of our series on Changing Climates, Hands On takes a look at some of the new technologies that generate power from clean and renewable sources.

Ray of light: solar energy

Europe's Centre for Solar Energy Research and Development in Altimara, Southern Spain, is the cutting edge of solar research, pioneering new technologies that could ultimately power large towns or industrial complexes.

Here, scientists are finding new ways to harness the sun's energy. In one system, a huge array of mirrors concentrates light onto a single receiver. The energy produced converts water to superheated steam that powers a high output generator. In another system, heated gas replaces water to drive a generator.

Away from the drawing board, solar power is already having considerable success as the primary energy source in one German town.

Freiburg may not have the sunniest skies but it does have the sunniest power. The town's chief architect, Rolf Disch, has designed a low-energy solar-powered town where even the swimming pool is solar-heated.

In another part of the world a solar lantern, developed by the Intermediate Technology Development Group (ITDG), is bringing light to a remote village in Kenya. Easily recharged by Africa's strong sunshine, the lantern gives up to four hours of light each day. What's more, it cuts out dependency on kerosene, is portable and, after an initial cost of US$100, the light is free.

In South Africa, the largest commercial rural solar electrification project aims to bring power to 50,000 homes. Developed by Shell, Eskom and Conlog, South Africa's national electricity company, the system provides enough energy to power a TV, radio and four lights for up to four hours each day. So far 1,400 homes have seen the light with this affordable system which costs just US$30 for installation and US$8 per month thereafter.

A breath of fresh air: wind power

In the Netherlands, wind power is already providing 325 megawatts of power to the national electricity grid - enough to supply a million homes.

On a smaller scale, windmills are having a comeback. In Sri Lanka, small windmills erected with local labour are a cost-effective way for communities with no access to the national electricity grid to receive power.

A river runs through it: hydropower

Deep in the Amazon, villages rely on batteries to provide energy. But batteries need charging regularly and people often travel miles to a recharging center. Now, ITDG have come up with an easy to use and cheap river turbine, which can recharge batteries. For the villagers of El Paraiso this means they can cut out their long trek and offer a profitable service for neighbouring communities.

But even if the Amazon isn't on your doorstep, small mountain streams can still provide a source of hydropower.

In Peru, only four percent of the country's population has access to electricity. Here, innovative micro-hydro systems are providing power to even the remotest towns. In Atahualpa, water channeled from a stream is forced down a pipe and through a turbine - producing enough power for 120 families. At a cost of US$1,500 per kilowatt the system isn't cheap but running costs are low, maintenance simple and one micro-hydro unit should last 20 years.

Water, water everywhere: sea power

The sea provides an enormous untapped resource. Oceans cover 60 per cent of the planet and wave power offers a source of energy that's still virtually untapped. If you took 0.1% of the available energy you could power the world for five years.

Islay, an island off the Scottish coast, is the testing ground for a wave power system called the 'limpet'. Using waves to generate an oscillating water column, air is forced out of a chamber into a turbine, which can produce up to half a megawatt of energy - enough to power 300 homes. It's still in development but this system could provide energy to remote coastal towns.

Fuelling the future: clean cars

Vehicles are one of the greatest polluters of our atmosphere but scientists are working on new ways to provide 'clean cars'.

In La Rochelle, France, they're experimenting with battery powered electric cars. In Nepal, electric taxis are providing an affordable alternative to 'dirty' diesel.

Although electric vehicles are a solution for today, they depend on batteries to store and release energy as needed. A longer-term solution may well be fuel cells that are powered by hydrogen gas and are far more efficient, lighter and less bulky. BMW has experimented with a working prototype in their Munich airport bus.

With a range of 150 kilometers on a full tank that takes only ten minutes to fill, the fuel cell car is CO₂ emission-free making it a very clean alternative to petrol and diesel. But there's only one problem. Fossil fuels are used to extract the hydrogen from water. But if scientists could extract hydrogen using the sun's energy it could well be the fuel of the future.