Saturday 2 February 2008

Solar energy for the UK and Northern areas

What can solar energy contribute towards the UK's needs? What can it contribute more generally in Northern areas where peak use is during the winter?

What can it contribute in areas where peak use is for cooling in the summer?

What will it cost?

Whilst my analysis will allow for technological improvements, I will not budget for breakthrough technology - by definition, you can't, and would be a fool to bet your house on it.

Even in areas as far south and hot as the Mohave, you only get around 0.25 of the maximum amount of summer power in the winter, due to the greater angle of the sun and longer hours of darkness. I will therefore use this factor of 4 in my arguments, although it should be noted that areas like the UK only actually get around a sixth of the summer power, mostly due to cloud cover, so a nominal 1kw installed in June might give around 150w of power on average through all the hours of the day and night, but in December gives a flow of around 30watts - so an expensive 5kw installation during Dec, Jan and Feb will only average around 150watts energy flow, which is why they need supplementing from the grid.


What makes things worse for cool climates is that peak use is in winter - for the UK at the lowest point on a summers day we might only need 20GW of power - we don't use air conditioning much.


At peak in the winter we use around 75GW.
That's roughly a four-fold increase in use.


This means that if we were to provide for all our needs with solar, we would need an installed capacity 4*6 of what we would actually use in the summer - as I said, not all areas are as cloudy, so to make our case for less cloudy areas in the north as well lets use four times as the generating difference.


So you install name plate of 16 times minimum usage.
Even with the most generous estimates of cost declines, it would cost a fortune.
It should be noted that although costs have declined very rapidly in PV manufacture, most of the that fall is in production costs, and that future falls are likely to be less as installation and maintenance cost falls are not of the same order, and will represent an increasing proportion of future reduced costs.


Which is a fancy way of saying that the very fast decreases we have had won't go on forever.


If we use nuclear OTOH it is just as efficient in winter as summer, so you 'only' would have to build a factor of 4 over the minimum summer load, which it is a lot more reasonable to think could be partly absorbed by the production of hydrogen and so on when you had too much power.


More sensibly, you could top up with coal for the peak power requirements, but the difference again is a factor of four less topping up is needed for the nuclear as compared to the solar option.

For the much lower needs of the nuclear option then topping up with biomass is also much more practical.

Would it be a good idea to install solar thermal panels in climates like the UK?

They are far cheaper than PV and give a fair proportion of the power needs over the year for hot water.

The problem with this is that just as for PV most of the power comes in the summer.

This means that you are generating the power when you least need it, and can't cover in the winter when it is most wanted.

You reduce base-load and so make the nuclear option less viable, as the lower initial costs of coal and gas make them a lot cheaper for peaking needs.

So once again you have locked-in coal, gas and CO2.

It's a different ball-game when maximum use is when most of the solar power is generated, in hot climates like the South-West of the US, and residential solar thermal panels can play their part there.

As can other solar technologies, utility scale thermal and PV and in my view solar can certainly take care of peak use, and may with modest improvements in storage, mostly overnight, take care of base load in the Mohave, for instance, if you assume that winter needs are half that in summer, using a figure of 25% of average daily insolation for the winter months compared to the summer, you would 'only' have to provide twice the requirement for the summer to take care of all needs in the winter.

It is more realistic though for the present to plan for winter needs to be covered by nuclear power, and peak load to be provided for by solar - if costs in solar drop by enough to provide for the winter, fine, but if not we have a good low-carbon game-plan at reasonable cost.


That is very hopeful for a lot of hot countries, which is where most people in the world live, as I can certainly see solar playing a big role there.


As for the UK vs the US, even in the north of the US you have better sunshine than in the UK, mainly due to less cloud cover most places except the Great Lakes.
However, I based my case on an optimistic factor of four difference in diurnal sunshine, winter to summer, not the gloomy UK's factor of sixth, so my remarks should apply to northern areas of the US too.

I'd just like to briefly comment on a couple of recent scenarios which were very optimistic on the future of solar power, planning to transport it from sunny climes to colder areas, with a US grid in the case of the proposals in the Scientific American:
A Solar Grand Plan: Scientific American

with discussion on these proposals here:
A Solar Grand Plan Article Comments Scientific American Community

And a proposal for a world-wide grid by the redoubtable Stuart Staniford here:
http://www.theoildrum.com/node/3540#more

Both postulate that the present rate of cost decrease in PV power will continue as far as the eye can see, and even then the costs the authors give are staggering.

The Scientific American's proposals give an initial subsidy of $420 billion to get things going, and still end up with fairly expensive power, on their own figures.

They also lock in a vast use of natural gas, as their chosen means of storage is compressed air, which needs heating to expand.

They do not say where they are going to get it from, what it's implications are for Global warming, or what costs they are presuming for this increasingly scarce resource.

They are also stuck with the problem of having to vastly over-install solar panels, as the old problem of maximum needs in the colder north happening in the winter, just when insolation even is the sunny Mohave is around 25% of it's summer maximum, as storage for a whole winter is entirely impractical.

Stuart's idea avoids storage, which he admits is problematic, and goes instead for a world -wide grid!

In the discussion, K Levin estimated that the costs of his proposals was around $1000 trillion! - and Stuart did not dispute this. - some 20 times to a close order of magnitude of the cost of using nuclear! - and that is with truly heroic cost reduction assumptions for the PV panels.

In my view both provide conclusive proof that their ideas are wholly impractical.

In contrast I would suggest using different resources where they are most practical.

In the cold and dark north you use nuclear - I will discuss in another post what proportion of total energy needs there it could cover, whilst solar takes care of all but baseload in the South-West, as I am perfectly happy to postulate further cost reductions in solar power, perhaps even to the point where even base load could be taken care of in sunny areas by solar, but lets keep our feet on the ground.

We can plan for using solar for peak use, even overnight if storage ideas by, for instance, Ausra work out, but not bank on solar costs decreasing for the forseeable future at the same hectic pace have they have done recently - at some stage progress is going to slow past the peak of the price reduction curve, and as a lot of total cost is sticky maintenance and installation costs, that point it seems to me is not that far off.

Solar will make, in my view, a massive contribution to power needs where most people live, in areas fairly close to the equator, but attempts to make this a universal solution do not work, and nuclear energy also has a major role to play in a low-carbon future.

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