(This is the text of a talk given at the Science Museum's Dana Centre on September 23rd 2010) I’ve spend most of today at a prospective site for a large solar farm in Cornwall. My colleagues and I think we can find space for 2 megawatts of capacity here, costing about £7m. Cornwall has the best solar radiation in the UK but we would need 150,000 of these farms, covering over 5% of the UK, to meet current annual electricity needs.

Last week I did some work on a very small wind farm in Norfolk, helping a parish council assess its impact on the community. The farm will provide about 3.5 megawatts at peak and probably cost around £5m. We’d need something like 50,000 installations of this size to replace annual electricity consumption. David MacKay says we’d have to devote all of Wales to wind farms to get to this amount.

The Committee on Climate Change indicates that we must almost completely decarbonise electricity production by 2030. So here’s some numbers for the cost of decarbonising current levels of electricity production using the most viable current technologies. Solar PV – around £1,000 billion. Onshore wind – about £250 billion. By contrast, just adding more gas power stations to replace closing coal, oil (and nuclear) would cost the country about £50bn.

Herein lies problem number one. Renewables remain expensive. Decades of underinvestment in R+D have left us without a significant UK renewables industry. We are now investing less than a sixth of the level in the mid 70’s in energy research. If we’d put a billion a year into marine energy, rather than a very sporadic few tens of millions, we might now be in a different position and able to exploit the tides and the waves at a reasonable price. We’d have a built an industry capable of serving the world.

But money isn’t the only problem. To get decarbonisation by 2030 we need not only

a) Large resources of private and public capital

b) Continued expensive R+D, often of dubious immediate productivity

But also

c) Huge political support, including a tolerance for expensive failure of new technologies

d) A high and reliable carbon price

e) An willingness to spend billions building stronger transmission links to Norway, Iceland, Netherlands, Ireland and France to deal with intermittency, and to meet the need to export electricity surpluses when the winds are blowing hard

f) A ruthless programme of peak shaving, introducing schemes to ensure that demand will never rise above pre-determined levels

g) active demand management, meaning, for example that our fridges turn off when wind speeds fall unexpectedly in Scotland

h) Huge investment in energy storage, probably including massive subsidy of electric cars and electric charging points

As a digression, my eco-friends tell me we can achieve most of what we want by ‘energy efficiency’. Well, it is true that heating and transport are highly wasteful users of energy in the UK. A petrol car is only about 25% efficient and the UK’s heat losses through buildings are a national disgrace. But the efficiency with which we use electricity cannot be increased dramatically, particularly in the home. Anything that uses electrical resistance to generate heat – an iron, a toaster, a washing machine, a heater or a kettle is already close to 100% efficient. We can improve efficiency somewhat on our heat pumps in the form of fridges and freezers. And consumer electronics have some space for efficiency gains, but these are tending to be wiped out by increases in the number of these devices in the home. Yes, we can move from fluorescent to solid state lighting but lights are only 15% of our home power consumption. It may be important to note that domestic electricity consumption has barely fallen in the recession.

And any future efficiency gains are going to be outweighed by the need to move transport and home heating towards using electricity. Electric cars and heat pumps for our homes are vital ingredients in national plans but will eventually add at least 50% to our electricity needs.

So my conclusion is that achieving our low carbon ends by 2030 is virtually impossible using renewables. Although offshore wind is speeding up - congratulations today to the new Thanet wind farm – we simply aren’t moving at the rate we have to. For example, we now have about 3,000 wind turbines compared to almost 20,000 in Spain. Britain – the Saudi Arabia of renewable energy sources – has made nothing like the commitment it needs.

The result is we will get more gas and, even worse, coal. Just today I got a PR release from the energy practice at Ernst and Young, banging a drum to the effect that the UK needs to let its large existing coal plants escape EU pollution rules and continue operating after 2015. Similarly, the owners of Didcot, just down the road from where I live, are beginning to soften up the local press for a campaign to keep this coal-burning dinosaur open.

This is why nuclear may be necessary. It is expensive, probably hugely expensive, and highly problematic in other ways. But is backed by the big 6 suppliers and it seems that if we guarantee a carbon price we can probably persuade them to provide the capital and organisational resources to make nuclear happen. Make no mistake, we need these companies and their access to the banks and bond markets to enable us to meet our decarbonisation objectives. Microgeneration, expensive renewables and other small initiatives simply aren’t enough.

But what about Olkiluto?, I hear you say. The new Finnish nuclear plant is years behind schedule and will almost certainly cost more than twice the contracted cost. Remember, though, that China is now constructing 25 nuclear power stations, mostly using an Areva design and expects to have more nuclear by 2020 than the UK’s entire current generating capacity. China is going to iron out the design defects of the EPR for us.

We are left with no alternative but to go, perhaps slightly shamefacedly, to RWE, EON and EDF and ask them just how high electricity prices need to go to get them to start a crash programme building new nuclear. It goes without saying that the national negotiating position is not strong. We might have wished for another route, but all other options have disappeared.