[imgcontainer] [img:solarTroughs530.jpg] [source]Julianne Couch[/source] Mirrors at Nevada Solar One’s concentrating solar power plant in the Mohave Desert tilt for light on a cloudy winter day. [/imgcontainer]
It’s sometimes said that to run the country on solar power we’d have to pave the whole landscape with collectors. It’s not nearly that bad. According to one estimate, photovoltaic plants that could meet the electricity needs of the United States would occupy a little less than 12,000 square miles. That’s a lot of land, but it’s only about one-third of one percent of the total land area of the nation. So there’s no need to pave over the whole country, just the state of Maryland.
–Brian Hayes, author of Infrastructure: A Field Guide to the Industrial Landscape
Maryland is safe from being armored in photovoltaic panels because it doesn’t have much solar energy potential. But the desert landscapes of Nevada and other states in the southwestern U.S. are ripe for industrial-scale solar development.
Industrial solar thermal power is not to be confused with the black panels perched on rooftops in sunny areas of the country. This is commercial-scale power, and it is partly what makes Las Vegas the brightest city on earth, as seen from outer space. Nevada is the number one state in the nation in solar energy generation per capita. Solar energy developers estimate that less than one-tenth of one percent of Nevada’s land could generate all of that state’s electricity needs. I wanted to see for myself the size and scale of what it would take to power the state using rays from the sun. So I contacted Nevada Solar One (NSO), operated by Acciona Solar Power. The NSO concentrating solar plant is located approximately 32 miles southeast of Las Vegas in the Eldorado Valley.
I spent the night at the Hacienda Casino, just outside of Boulder City, the only town in Nevada that doesn’t allow gaming. My tour guide, Acciona Solar Power’s marketing and communications manager Michele Rihlmann-Burke, said that Nevada Solar One would be easy to spot: there’s nothing else out there in the desert along Highway 95.
Actually, I noticed many things en route to Nevada Solar One. Chief among them were the high power-transmission towers taking the electrical load from nearby Hoover Dam into the power grid. The towers were so large that I imagined the solar plant to be to that scale. I’ve lived much of my life in places where the landscape is dominated by buildings, mountains, crops, or livestock, things one easily notices from the road. But scanning through the windshield across the Mojave Desert on this overcast winter morning, I started to wonder where the creosote bushes and sand ended and the power plant began. I expected to see glittering mirrors on tall frames, but instead only spotted a low area off to the west where it looked like the desert had been whitewashed. Because of the gray sky, the mirrors didn’t look like mirrors, at all, but just more arid landscape.
[imgcontainer left] [img:solarMichele-Rilhmann-Burke320.jpg] [source]Julianne Couch[/source] Michele Rihlmann-Burke of Acciona Power, at the company’s Nevada Solar One plant near Boulder City, NV. [/imgcontainer]
Fortunately, a well-marked turnoff to Eldorado Valley Drive signaled my way in. I located the building where I was to meet Rihlmann-Burke, an athletic-looking young blonde, a transplant from California adapting to life in the western suburbs of Las Vegas. As we rummaged for hard hats and protective eyewear, she explained how the power plant came to be. Because the land is owned by Boulder City, Acciona faced fewer regulatory hurdles to build here than they would have building on federal land. As it is, the plant represents a $266 million investment. That’s twice what it would cost to build a new coal-fired power plant, but then again, there is no fuel to buy.
Rihlmann-Burke took me into the control room where we met operator Aaron Boucher and technician Matt Haines. They sat among various computer monitors that displayed mirror positions and fluid temperatures. Concentrating solar power uses the sun’s rays to heat a transfer fluid, Boucher explained. That transfer fluid is encased in a pipe called a solar receiver. The beaming sun hits the solar receiver and heats the transfer fluid to several hundred degrees. The fluid then passes through a natural gas heat exchanger inside the power block. There the fluid gets even hotter and turns into steam. The steam drives a turbine connected to a generator that produces electricity. This is basically how generating electricity works, whether the steam is created by burning coal or biomass, exciting uranium atoms, or drawing hot water up from an underground geothermal field.
After this introduction, Rihlmann-Burke and I left the control room, the fellows still gazing out the window at mirrors glowing dully in the unhelpful sky. They could control the direction of the mirrors to track the daily progression of the sun, but they couldn’t do much about the clouds.
We stepped out onto a balcony and took in a panoramic view of this section of the Mojave. The sandy soil here really is lifeless, with thousands of mirrors garrisoned between earth and sun. Rihlmann-Burke pointed out where the desert sand beneath and around the mirrors appeared to be wet and shimmering. That’s because it’s been sprayed with an oily substance to keep down dust and dirt, the major inhibitors of the mirrors’ reflective power. This oily substance also keeps anything from growing or otherwise living under the mirrors.
[imgcontainer] [img:solarTroughRows530.jpg] [source]Julianne Couch[/source] Troughs of solar-mirrors cover about 350 acres at Nevada Solar One’s plant near Boulder City. [/imgcontainer]
We left the balcony and wandered among the temporarily under-achieving mirrors. Sandy soil crunched underneath our shoes, and the solar mirrors creaked like old bed springs: otherwise there was no sound, not even from distant Highway 95. We strolled under cloudy skies between mirrored rows about a quarter mile to the power block. We got a close look at the mirrors, arranged on aluminum frames, forming rows of troughs. These troughs take up about 300 of the 400 acres of the Nevada Solar One facility.
NSO has a maximum generating capacity of 75 megawatts. Even on cloudy days like this one, the plant can still operate, for a time. If a cloud comes and covers the sun, the heated fluid that has already entered the plant can still do its job, for awhile. Nighttime is another matter, especially during the short days of winter. The technology that would allow solar power plants to store electricity is still under development. Material called molten salt is being tested because it can retain heat; theoretically it could retain heat made by the solar plant during the sunny day and release it at night, allowing the plant to continue making steam.
[imgcontainer] [img:solarDesert_tortise530.jpg] [source]wiki[/source] Desert tortoise (Gopherus agassizii) live in burrows throughout the Mohave Desert. Development, both residential and industrial, is destroying the tortoise’s habitat. [/imgcontainer]
Acciona Solar Power estimates that the U.S. offers several hundred gigawatts of concentrating solar power potential; however, only about seven percent of power is provided by various renewables each year. Of that percentage, solar power contributes about one percent. One concern about these industrial-scale solar power plants is the amount of space they cover. But solar advocates argue that this is a good use of space, creating energy that produces little pollution. Another concern is the harm development of any kind in the desert has on the environment. For example, one of the most iconic species of the area, the desert tortoise, digs its burrows underground, where it spends the majority of its time out of the hot desert sun. As development in the desert has displaced tortoise habitat, efforts have been made to relocate the creature to other spots in the desert. As it turns out, the desert tortoise doesn’t want just any old burrowed tunnel. It wants its own and will die trying to get back to it. Yet, solar advocates point out that other forms of energy development in this landscape could do even more environmental damage, pointing to the damming of the Colorado River as an example.
By now most people understand that the earth is warming and greenhouses gasses from burning fossil fuels are part of the cause. The question is, what to do about it. The Union of Concerned Scientists reminds us that the sun supports all life on earth and is responsible for most of the energy we use. “The sun makes plants grow, which can be burned as ‘biomass’ fuel or, if left to rot in swamps and compressed underground for millions of years, in the form of coal and oil. Heat from the sun causes temperature differences between areas, producing wind that can power turbines. Water evaporates because of the sun, falls on high elevations, and rushes down to the sea, spinning hydroelectric turbines as it passes.”
They point out that all of the energy stored in the earth’s reserves of coal, oil, and natural gas is matched by the energy from just 20 days of sunshine.
I think I’m underutilizing the power of the sun.
I contemplate the ways I use the sun without even thinking about it. I put my houseplants in the window and open the blinds to the morning light. I use the sun to power my tiny solar calculator, used for monthly bill-paying sessions. I get outside and ski, or hike, or cut down my annual Christmas tree, grown from the power of the sun. I wait for the sun to grow the food I eat, sustain the animals I eat, and make the world turn. I acknowledge that everything comes from the sun. Coal, gas, and all those other fuel are just the middlemen. Like in most other matters, it makes sense to go straight to the source.
Julianne Couch’s research is supported by the University of Wyoming School of Energy Resources through its Matching Grant Fund Program