opinion@dailylobo.com
Sun: it’s everywhere. Get used it.
That might as well be the motto of the entire American southwest, especially New Mexico and Arizona. The entire region is blessed by the perfect intersection of several climatological and meteorological factors that all make sure the sun shines strong, nearly without fail, for more than 300 days each year.
However, at least at the commercial-industrial level, we’re beginning to move away from cursing such strong, ever-present sun, as our custom has been for centuries. Lately we’ve been exploring the possibilities of harnessing it for clean, cheap electrical power.
The first step in that harnessing process was the use of photovoltaic cells in solar panels. These panels simply soak up sunlight and transform it into electricity, which is then sent through electrical lines to power whatever we desire.
But solar panels tend to have drawbacks. For one thing, they’re most practical for personal, home or small business energy generation, because they require a great deal of space to generate significant amounts of electricity. They can be used for larger-scale applications too, but the amount of land required skyrockets.
This is a good start to using sunlight for electricity, but we can do better.
There are several alternatives to solar panels, two of which I’ll discuss here. The first of these is parabolic trough solar thermal power, used in Spain, Germany and here in the U.S. state of Nevada.
Parabolic trough solar thermal power is a bit more involved than solar panel electricity generation. In this setup, metal tubes filled with heat-conducting thermal oil are sandwiched in between solar panels. The collected sunlight heats the oil in the tubes, which in turn is used to heat a small amount of water to produce steam which is then used to turn a turbine to create electricity.
Such an approach combines the tried-and-true approach of solar panels with the more efficient electricity generating method of steam turbines. It also solidly deals with water shortage problems in sun-rich deserts by using a minimal amount of water to create the steam needed to drive the turbine, though water use is unavoidable. This method still takes up a large amount of land to fit all the solar panels.
Another variation on this approach is heliostat power. This design is being developed right here at Sandia National Laboratories as part of the Department of Energy’s Solar Thermal Electric Program.
It’s also being developed privately in California, as well as in other countries such as South Africa, Morocco and Israel.
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Also known as the ‘power tower’ approach, this design uses hundreds of moving, solar-tracking mirrors to focus sunlight onto a receiver mounted on a central tower. The aggregate sunlight then heats molten salts to over 1000 degrees Fahrenheit. These salts are stored at that high temperature until needed to heat a pool of water to produce steam to drive an electricity-producing turbine.
While still suffering from the large-land-usage problem of the previous two approaches, plants of this design can be built on hills due to the solar-tracking mirrors approach. Also, because the molten salts lose heat much more slowly than thermal oil does, the salts can easily be stored to produce steam for electricity when the sun isn’t shining. The two previous designs mostly produce electricity only during sunshine hours.
So, let’s quickly review here. With solar panels you can generate electricity without using any water at the cost of the total electricity output and generation efficiency compared to fossil fuel sources, but for large-scale deployment you’ll be using up several hundred acres of land. There’s a reason why they’re called “solar farms.”
Or you can increase generation efficiency and electricity output into the fossil fuel range with the parabolic troughs approach.
You’re still using up lots of land with fields of solar panels, however, and you’ll lose a lot of that stored heat when not immediately using the thermal oil to heat water.
Finally, with power towers you can greatly increase heat storage efficiency and gain the ability to generate electricity efficiently when it’s not sunny out, but then you have to deal with the relatively large mechanical maintenance cost of the moving mirrors. There’s also the ever-present land use problem, though it’s offset here by the ability to build on hills.
The upshot is that, as is true with all power sources, solar power isn’t perfect and has its various downsides. However, it is of more use in the southwest compared to any other region in the U.S., and should be used here to its fullest practical capacity, by mixing and matching various approaches that suit various commercial, residential and geographic needs.
