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.