By 2050, half the world's energy is going to come from renewable sources such as sunshine, wind, running water and green plants rather than from oil, gas, coal and nuclear, according to a scenario Shell is working to.
The Anglo-Dutch group said it would be investing pounds 300m over the next five years in expanding its capacity to make solar cells and in growing trees to be burnt in electricity-generation power stations. It is a shift environmentalists have long been demanding.
Jim Dawson, president of the newly created Shell International Renewables, said no other company was investing as much. His aim is to win at least 10 per cent of the world market for solar or photovoltaic cells by 2005.
Shell had made its decision mainly because of how it expected the energy world to change over the next 50 years. ''We have not reacted in a knee- jerk way to environmental pressure, but we do listen to what the environmental groups and others say. We'd be stupid if we didn't.''
The new strategy compares with that of the other UK-based oil giant, BP, which has taken an earlier and larger, interest in photovoltaics. BP already has 10 per cent of the market, currently worth over pounds 600m a year and growing at some 14 per cent every 12 months.
Growing trees to burn them in power stations may seem a strange way of providing green, renewable energy. But if the trees chopped down are replaced by young, growing trees in plantations it is. These growing trees absorb carbon dioxide, the main global warming gas, which is produced when coal, oil, gas and also wood are burnt.
If wood replaces fossil fuels in power stations, and new wood is constantly being grown to replace it, then no extra carbon dioxide is released into the air.
Shell already has plantations of fast growing trees in South America, Africa and New Zealand, covering an area larger than Greater London. It promises that it will not take wood from virgin forests and where there are stands of natural trees near or among its plantations these will be protected.
Shell believes the big market for renewables is in rural areas of developing countries where many homes and businesses are not on the electricity grid. It envisages buildings covered with photovoltaic cells, and small power stations using locally grown wood. It plans to build several in the next few years.
Yesterday, Greenpeace UK welcomed the strategy. ''It is significant that they are trying to catch up with BP, but we won't be able to judge how serious they are for several years,'' said solar campaigner Marcus Rand.
''Hopefully 1997 will come to be seen as a turning point,'' he said.
In terms of Shell's total investment each year, which goes mostly into oil and gas exploration and oil products like plastics and chemicals, the new money for renewables is tiny - about one per cent.
But the planned investment in its new division is only a little less than what has been invested each year in Britain through the 1990s by the entire private sector on installing renewable energy sources.
Rupert Fraser of the UK Renewable Generators Consortium, which represents this young industry, said: ''I think Shell is a serious player. They're cautious people, and they wouldn't want to make a fuss about getting into renewables if they had to get out again a few years later.''
Shell is also working on genetic engineering of trees, to make them more resistant to frost and easier to turn into paper, at its forestry research division in Kent. That will not please Greenpeace, which is strongly opposed to the new technology of switching genes between species.