THERE’S much talk these days about how everything from solar energy to wave energy and giant offshore wind farms are “the future”. And maybe they are.

The problem is just that if you are over 40 they aren’t very likely to play a particularly big part of your future.

Onshore wind power is limited in that there are only a few sites where the wind is such that turbines work at a cost-effective capacity level (after you’ve subtracted the subsidies – which clearly can’t be paid for ever).

Sea-based wind farms are still in their infancy, as well as being expensive to build. Solar power is also expensive and difficult to site (although the technology is constantly improving here, so fingers crossed).

Geothermal power has not managed to grab any main-stream attention. And biofuels, while a fabulous idea in theory, clearly come with nasty side-effects (the rising price of soft commodities as food fights fuel for land, and the consequent impact on world hunger).

So for the foreseeable future at least, cutting carbon emissions and creating energy security in the West really means going nuclear. This – despite the various misgivings many have about its security – is an amazingly efficient way of generating energy.

Building reactors is expensive, but in terms of the important thing – cost per kilowatt per hour over their lifetimes – they easily beat all other forms of alternative energy.

They also offer a consistent and controllable supply of power to a national grid (not so with the likes of wind power) and can be sited where needed rather than where the weather suits.

In Britain, we are just coming round to the truth of all this. We get about 20% of our electricity needs from nuclear power stations, but the government has, until recently, been very reluctant to commission new reactors.

Now it appears to have bowed to the inevitable: late last year Gordon Brown said that five more plants were to be built as our old ones run down and more recently John Hutton, the business secretary, has said we must fast-track the replacement programme.

While we have been dithering, though, the rest of the world has been with the nuclear programme for some time. Resource Capital Research, a commodities forecaster, estimates that the number of proposed power stations rose more than 60% last year – the Chinese, in particular, can’t get enough of the idea.

Beijing is planning for China’s future as the largest consumer of energy in the world with 30 nuclear reactors due to be built in the next 12 years.

In France, 80% of the total energy supply comes from nuclear power (it has 59 nuclear power stations) and the world total is already more than 16%: in 2007, there were 435 nuclear power stations across 31 different countries.

Which brings us to the main thing you need to make nuclear energy: uranium. France alone uses up about 10,000 tonnes yet global production is a mere 50,000 a year – enough to meet about 60% of global demand.

So far the other 40% or so has come from stockpiles and odds and ends lying around in decommissioned postCold War weaponry. Today these stockpiles are not as big as they were. It is possible to recycle some uranium from spent fuel rods but the upshot is that the long-term supply simply isn’t there to meet the demand.

Given this it should be no surprise that the uranium price has already risen roughly fourteen-fold in the past six years, making fortunes for the entrepreneurs and investors who got into the story early along the way (I did write about this back in July 2006, so I hope that includes some readers).

That said, the price did rise rather too fast – reactors take a long time to build, so while there is a lot of demand it isn’t all with us yet. And while stockpiles are being run down, they aren’t gone yet.

It is an exciting market, but maybe not yet one that justifies uranium at the $138 a pound level it hit last June. In the past nine months or so the market has begun to recognise this and the price of a pound of uranium has come off sharply.

By January a pound would have cost you $90 and by the end of the month just $78. Today it’s more like $73. So is it a buy now?

With the long-term fundamentals as sound as ever, the oil price likely to remain around $90-$100 (something that concentrates the minds of governments) and the drive to find a replacement for the Kyoto protocol on climate change – which expires in 2012 – well under way (Tony Blair has added it to his portfolio of world-saving initiatives) I suspect it might be.

The biggest miners of uranium are Cameco and Rio Tinto. I’d be wary of buying into the latter right now – these big miners have moved very far, very fast and, given the global environment, it is not unreasonable to expect them to pull back at some point.

While I like Cameco and the fact that it provides 20% of global supply, I still think I’d hold off on buying it for a while – on a price/earnings ratio of 34 times for this year and just over 20 times for next, it still isn’t cheap, even though the price has come down a lot since last year.

It is also worth looking to Geiger Counter, a fund that invests mainly in companies either exploring for or producing uranium. Last year, the shares nearly doubled. This year they are down 19.5% – which is good news for anyone wanting to get in now – but the irritating thing about them is that they trade ata premium to their net asset value.

I hate buying things at a premium so I’m tempted to suggest that you wait a bit to buy them– see if the bear market brings them down nearer to their net asset value and buy them when it does. The same goes for Cameco.

Merryn Somerset Webb is a former stockbroker and now editor of Money Week. Her views are personal and investors should always seek professional advice

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