When it comes to solar panels, readers in the UK are likely to think only of great grey-black slabs perched atop Mediterranean houses seen from trains or descending aircraft, but changes are afoot that look set to alter that misleading impression.

In the wake of the recent G8 summit in Japan and the reams of environmental reports and recommendations made there, one thing stood out – renewable energy is not just essential for the health of our planet; it's also one of the keys to economic sustainability.

Photovoltaic possibilities

Of the options available to us for replacing fossil fuels, one of the prime candidates for success is solar power generated by photovoltaic, or PV, cells.

According to the European Renewable Energy Council, by 2040 solar power will likely meet fully one quarter of worldwide energy demand, but where will that huge amount of energy – around 9 terawatt hours (TWh) – come from?

To find out, we spoke to two of the world's leading supplier of solar-cell equipment, Osaka-based Sharp and Sanyo.

Long history

We'll start with Sharp, an electronics giant that's far better known for its television sets and domestic appliances. But its most recent annual financial results show that ¥150 billion (£700 million), or 4.5 per cent of its business, came from solar cells and associated PV technology.

That shouldn't be too surprising to anyone familiar with the PV business. Based on International Energy Agency figures, Sharp has been responsible for 2 gigawatts (GW) of the 8GW-worth of solar equipment shipped worldwide to 2007 since the technology was invented in 1953.

While domestic solar panels account for a relatively small proportion of total sales, Sharp has kitted out almost 2,000 lighthouses and over 160 satellites with its various flavours of solar cell.

Complex technology

Given such diverse uses, it's obvious that the technology that goes into the PV business is complex, but for our purposes we can focus on the two main kinds of silicon-based solar cells.

Sharp's two 'PV pillars' are the currently dominant crystalline-type cells and the up-and-coming thin-film type. The former are suitable for use even in moderate climates, such as the UK, but use more of the increasingly precious silicon.

Conversely, thin-film cells use only 1 per cent as much silicon, but are only practical in countries where the Sun can be relied on to shine for much of the year.

Currently, crystalline PV accounts for 80 to 90 per cent of the world's output, but this is changing as silicon prices rise due to heavy demand from computer chip makers.

Huge increase

Sharp's existing plant in Nara churns out crystalline cells that can generate just over 700 megawatts (MW) of power per year. Come 2010, however, production will begin at a new thin-film plants that will ultimately deliver 1GW of power per annum.

One of these immense complexes, at Sakai in western Japan, will actually by partly powered by solar panels fixed to its own roof and walls.

Working with a local electricity company, the cells will deliver 18MW of power to the plant, meeting 5 per cent of its energy needs and underlining how important thin-film PV cells are to Sharp.

Throw in increasing government commitment to solar energy around the world and it's clear that change is afoot.

For example, the Japanese leadership has set a target usage capacity of 4.8GW of solar power by 2010. That's equivalent to five nuclear power plants.

Who cares anyway?

The numbers are clearly compelling, but what do they add up to for the end user – should the average person in then street really give a hoot?

Sharp's Miyuki Nakayama explains that the company hopes to increase PV production with a very specific end-cost goal in mind – electricity coming out of wall sockets that costs no more than it does now: