Saturday, May 10, 2008

More problems with alternative energy

It's certainly not encouraging to find research that casts doubt on the economic or technological viability of energy sources other than fossil fuels. There are two compelling reasons the whole world needs to transition away from fossil fuels: (1) To derive energy from fossil fuels requires combustion, which releases large amounts of the greenhouse gas CO2, and other pollutants, into the atmosphere. (2) Resources of the most convenient (for use in land vehicles and aircraft) fossil fuel – petroleum – are rapidly dwindling, especially in easily accessible locations, so the price will necessarily increase over time, as will the risk of armed conflict between countries to protect access.

On the other hand, it's necessary to be as realistic as possible about the alternatives, in order to avoid heading down a path that could be (quite expensively) wrong.

So in a couple of recent posts here and here I discussed various studies that raised cautions about the potential for solar energy, nuclear energy, hydrogen (for fuel cells), and biofuels. New cautionary reports about these various alternatives keep appearing.

Let's begin with solar. There's more than one way to take advantage of energy from the Sun. Photovoltaic production of electricity directly from sunlight receives the most attention. But there are other approaches, such as solar thermal energy and perhaps (some day) even the use of artificial photosynthesis:

Artificial Photosynthesis Moves A Step Closer (4/28/08)
Imagine a technology that would not only provide a green and renewable source of electrical energy, but could also help scrub the atmosphere of excessive carbon dioxide resulting from the burning of fossil fuels. That’s the promise of artificial versions of photosynthesis, the process by which green plants have been converting solar energy into electrochemical energy for millions of years. To get there, however, scientists need a far better understanding of how Nature does it, starting with the harvesting of sunlight and the transporting of this energy to electrochemical reaction centers.

But most commonly when "solar energy" is discussed, photovoltaic technology is what's actually meant. The technology has existed for many years. The problem has always been cost. Even today it's estimated to be almost ten times as expensive per kilowatt-hour to generate electricity with photovoltaics as it is from fossil fuel:

Expert Foresees 10 More Years Of Research & Development To Make Solar Energy Competitive
(4/7/08)
The single biggest challenge, Gray said, is reducing costs so that a large-scale shift away from coal, natural gas and other non-renewable sources of electricity makes economic sense. Gray estimated the average cost of photovoltaic energy at 35 to 50 cents per kilowatt-hour. By comparison, other sources are considerably less expensive, with coal and natural gas hovering around 5-6 cents per kilowatt-hour.

Because of its other advantages -- being clean and renewable, for instance -- solar energy need not match the cost of conventional energy sources, Gray indicated. The breakthrough for solar energy probably will come when scientists reduce the costs of photovoltaic energy to about 10 cents per kilowatt-hour, he added. "Once it reaches that level, large numbers of consumers will start to buy in, driving the per-kilowatt price down even further. I believe we are at least ten years away from photovoltaics being competitive with more traditional forms of energy."

Major challenges include developing cheap solar cells that work without deterioration and reducing the amounts of toxic materials used in the manufacture of these cells. But producing low cost photovoltaics is only a step in the right direction. Chemists also need to focus on the generation of clean fuels at costs that can compete with oil and coal.

Nuclear power continues to be quite problematical too. Many of its problems have been known for a long time, such as the difficulty of safely disposing of spent fuel and the dangers of diversion of nuclear fuel to weapons. But more recently attention has begun to focus on the increasing cost of extracting and processing uranium, and the greenhouse gases generated in that process:

Questioning Nuclear Power's Ability To Forestall Global Warming (4/30/08)
Rising energy and environmental costs may prevent nuclear power from being a sustainable alternative energy source in the fight against global warming, according to a new study.

In the article, Gavin M. Mudd and Mark Diesendorf investigate the "eco-efficiency" of mining and milling uranium for use as fuel in nuclear power plants. ...

The study points out that supplies of high-grade uranium ore are declining, which may boost nuclear fuel's environmental and economic costs, including increases in energy use, water consumption and greenhouse gas emissions. In addition, newly discovered uranium deposits may be more difficult to extract in the future -- a further drain on economic and environmental resources.

Here are two somewhat longer articles about this report, with some rebuttal from the uranium mining industry: Nuclear may lose green tag if fuel costs rise and Nuclear energy becoming less sustainable.

Finally, it's often overlooked that there's one additional increasingly scarce resource that's usually needed to produce energy by many different technologies: fresh water.

Water Needed To Produce Various Types Of Energy (4/17/08)
It is easy to overlook that most of the energy we consume daily, such as electricity or natural gas, is produced with the help of a dwindling resource – fresh water. Virginia Tech professor Tamim Younos and undergraduate student Rachelle Hill are researching the water-efficiency of some of the most common energy sources and power generating methods.

When the requirements for fresh water are considered, new disadvantages appear for many alternative energy sources, especially biofuels and nuclear energy:
According to the study, the most water-efficient energy sources are natural gas and synthetic fuels produced by coal gasification. The least water-efficient energy sources are fuel ethanol and biodiesel.

In terms of power generation, Younos and Hill have found that geothermal and hydroelectric energy types use the least amount of water, while nuclear plants use the most.


Update, 5/14/08:

More headaches of nuclear energy. There's a new, longish Scientific American article on the problem of nuclear fuel recycling: Nuclear Fuel Recycling: More Trouble Than It's Worth


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1 Comments:

OpenID quantummoxie said...

I'm toying with going solar myself and, while I am an environmentalist of sorts, my main motivation is economic and I will be crunching the numbers this week. I'll also point out a friend of mine has been 100% solar for years and made his money back a decade ago (see his website: http://www.solarhouse.com).

5/17/2008 04:54:00 PM  

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