In the rocky, flat Nevada desert, roughly halfway between Reno and Las Vegas, sits the small town of Tonopah, long ago home to the second richest silver strike in Nevada history. In the next few years, this historical site may be the gateway to our future—as host to the very first commercial solar power plant.
This plant will not be composed of those familiar panels you’ve seen on rooftops, called photovoltaic, or PV, panels. PV panels directly convert sunlight into energy, and therein lies the problem science has had to overcome in order to fully utilize solar power: the sun is not always present, but a power plant must consistently be providing power.
The plant, to be built on federal land near Tonopah, utilizes another type of technology known as Concentrated Solar Power, or CSP. Once funding is obtained, it will be constructed by a California-based company called SolarReserve, with technology licensed from Pratt & Whitney Rocketdyne. SolarReserve claims they can now utilize solar power in ways comparable to traditional power plants.
“Most of the big power plants out there use some sort of a heat source to generate steam,” SolarReserve Director of Development Andrew Wang explained to Organic Connections. “That steam spins a turbine, and the turbine spins a generator. You then have a huge amount of megawatts that flow out of the grid. That heat would normally come from natural gas, oil, coal or nuclear energy. We operate much the same way—we boil water, generate steam and spin a turbine. It’s just that our heat source is not a conventional source—it’s the sun.”
The technological trick was to harness the power in such a way that it can be saved and then used as a heat source whether or not the sun is there. This is what CSP technology does and the hurdle it overcomes.
“The way this power plant looks is that there is a large circular field of sun-tracking mirrors, called heliostats,” Wang continued. “These mirrors track the sun across the sky and are all coordinated in directing sunlight to a single central point on top of a tower. That point is called a receiver, and there’s a fluid flowing through the receiver.”
The fluid is molten salt, a mixture of sodium nitrate and potassium nitrate. The concentrated sunlight from the mirrors, when sunlight is present, heats the molten salt, which is then stored in a large tank. The molten salt loses very little heat and is a constant heat source for generating steam in the power plant.
The technology is the result of two different test projects, Solar One and Solar Two, which were conducted several years ago by Rocketdyne. The initial concept was to simply boil water utilizing sunlight. “You would think that since you’re trying to generate steam, you could just boil water directly,” Wang said. “Well, that was what Solar One was. But we found all sorts of technical and operational challenges with trying to do a water-to-steam system. The Department of Energy, which sponsored the project, said that we needed to find a way to basically decouple the availability of sunlight from the ability to generate electricity—to have renewable solar energy without having to rely on the sun being there all the time. That’s really the problem in our industry and with the technologies out there; they rely on the wind blowing or the sun shining in order to generate electricity. Otherwise you get nothing.” The introduction of molten salt as a heat medium solved that issue.
Because of the way the plant is laid out, it must be utilized in specific terrains. “The field is roughly 1.8 miles in diameter in order to accommodate all the mirrors,” Wang described. “Each mirror is individually controlled and individually coordinated, regardless of wherever it is in the field, to direct that sunlight to the top of a 656-foot tower. So our power plants are economically competitive when you have intense sunlight. If you’re in New York, it might get hot sometimes, but the intensity of the sunlight is nowhere near what we have in Southern California, Arizona and New Mexico. You also need the kind of flat land in order to put this sort of thing out there.”
This type of power plant would certainly be a great start for solar energy on a commercial scale, given that there are numerous large metropolitan areas that could be supported. SolarReserve has also established offices in London and Madrid, seeking to build CSP plants in appropriate locations in Europe and the Middle East.
“We are pursuing business in Spain, the Middle East, North Africa and South Africa,” Wang said. “We’re also starting to look at China and Australia.
“The United States is really the big market, long term, however. I myself spend quite a bit of time in Arizona, Colorado and New Mexico working on the next level of projects that we think will be going to market. And of course the near-term business is focused on our Nevada project. At this point we’ve got the power purchase contract; we’ve got the technology ready to go. We’re out there hunting down the financing right now, so in Q2 we think we’re going to put some shovels in the ground.”
Organic Connections will follow SolarReserve’s progress and report the results.
For more information on SolarReserve, visit their website at www.solarreserve.com.