Monday, January 12, 2009

Is Solar Energy a Bright Idea?

There's plenty of talk about the environmental benefits of solar power. Some politicians love it because it makes them seem more environmentally friendly, but what are the pros and the cons of solar power? Is it affordable and is it practical?

The pros are obvious, the sun is a perfectly renewable source of energy, it produces no pollution directly although indirectly there is pollution through the production. Some of the drawbacks are obvious, it only really works when the sun is shining so to provide constant power all the time would require a storage system or more conventional power sources to balance things out. The storage requirements are such that some scientists feel that it is impractical to view solar as a true replacement for conventional power sources.[1]

So what else is holding solar back? The low energy conversion efficiency and the cost.

A higher energy conversion efficiency would mean that we can use fewer panels to achieve the same power output. As a sample calculation, consider a 1 square meter solar panel that has a conversion efficiency of about 20%. The sun delivers 1000W/square meter at peak value so ideally the solar panel could provide 1kW of power when the sun is shining brightest, but in reality it can only provide 0.2kW. In a place like San Diego, there are roughly 5 hours of peak sunshine per day. Which means it would then provide 1kWh per day.[2]

Supposing that we replace the entire 2001 US power supply of 3386 billion kWh with solar power. That means each day there would be a requirement on average of roughly 10 billion kWh. This means that if we assume that 1 square meter of solar panels generates roughly 1kWh per day then there would be a requirement of 10 billion square meters to generate the required power. This is 10 000 square km, roughly the size of Connecticut, which actually, is only 0.1% of the US total land area.

And what about the cost? As you can see from the table, solar power can cost over 5 times the cost of a conventional power source and over 3 times the cost of nuclear power.[3]

Which brings me back to the question I pose in my title. Solar energy as it currently stands can reduce the dependence of nations on fossil fuels but is not a feasible option to replace fossil fuels altogether. In its favour, it is a relatively clean source of energy. Against it, the high cost of solar energy would destabilize the US (and by extension - world) economy, increasing energy costs by more than 4 times. The technology to 'smooth' the supply of electricity out to provide a consistent supply of energy does not exist yet and the conversion efficiency ratings of solar cells are still insufficient still to reduce the land requirements to a sufficiently reasonable level.

But this should not discourage us. There is no cure-all, there is no silver bullet. Even if solar energy only reduces the total energy requirements from other traditional sources by 1%, it means we are 1% closer to breaking our oil addiction than we were without it. But we must look realistically at other options to move further.

[1] G. W. Crabtree and N.S. Lewis, "Solar Energy Conversion" Physics Today, 37-42, March 2007.

[2] T. W. Murphy Jr, "Home Photovoltaic Systems for Physicists" Physics Today, 42-47, July 2008.

[3] L. R. Glicksman, "Energy Efficiency in the Built Environment" Physics Today, 35-40, July 2008.


BeyondGreen said...

It would cost the equivalent of 60 cents a gallon to charge and drive an electric car.The electricity to charge the car could come from solar or wind generated electricity.If all gasoline cars,trucks,and suv’s instead had plug-in electric drive trains, the amount of electricity needed to replace gasoline is about equal to the estimated wind energy potential of the state of N.D.This past year the high cost of fuel so seriously damaged our economy and society that the ripple effects will be felt for years to come.Why not invest in setting up some alternative energy projects on a national basis, create clean cheap electricity,create millions of badly needed new green collar jobs, and get out from under our dependence on foreign oil.What a win-win situation that would be. There is a great new book out called The Manhattan Project of 2009 Energy Independence NOW by Jeff Wilson. I highly recommend this book for anyone interested in alternative energy.

Eric said...

Interesting fact BeyondGreen. The problem is that a conversion from fossil fuels for cars to all-electric cars would put a strain on the current electrical grid which is not ready for such demand.

Moreover, the price per gallon would greatly depend on the form of electricity used as I pointed out.

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