Over the years, the solar industry has been growing at a fast pace. Solar power generation is a very interesting solution to the world’s energy problems. Solar energy is clean and renewable. There will soon be no reason to burn fossil fuels and damage our atmosphere and our oceans. Solar power generation is slowly gaining terrain in the energy market. However, there has always been a problem with using solar energy. How does one store it and use it when the Sun is not shining? Up to now, various types of batteries were storing a part of the solar energy for hours – perhaps even days. Now, a company in Nevada has found an innovative solution to the solar energy storage problem. They are using salt to store solar energy so they can use it at night or at any time the Sun does not provide enough energy.
SolarReserves: Innovation at its Best
The company is called SolarReserves and it runs a CSP plant (short for Concentrated Solar Power) in Nevada. The plant is known as Crescent Dunes and has a capacity of 110 megawatts. Unlike other solar installation, the CSP plant uses huge mirrors to reflect sunlight and concentrate it on a tower that is 650 feet tall. So, what’s in that tower that it requires so much energy from sunlight? The answer is fairly simple actually: it’s salt. Well, not your ordinary table salt (which is made of sodium chloride). The salt in the 650-foot tower is composed of 60% sodium nitrate and 40% potassium nitrate, which makes it perfect for storing solar energy.
As Rob Dieterich, a reporter covering various solar projects in Nevada explains it plainly, “Basically, the reflected sunlight from the mirrors, from the heliostats, is heating molten salt that’s circulating up and down through that tower.” The sunlight reflected by the mirrors below is enough to heat the salt in the solar tower to around 538 degrees Celsius (or 1,000 Fahrenheit). The heated salt then gets sent to a special tank that is very well insulated. The interesting part is that the heated salt can sit in that special tank for days without losing almost any heat to the outside world. To put it simply, the scientists at SolarReserves found a way to preserve solar energy for days with minimal loss.
When the solar energy needs to be transformed into electricity, the salt is simply transferred to a heat exchanges which extracts the solar energy and transforms it into steam. As you would expect, the steam is then swiftly used to generate electricity with the help of a simple yet effective steam power turbine. According to Dietrich, the company can use the steam turbine all night long with the energy stored in the salt during the day. Basically, the company has a solar installation that is able to generate electricity day and night. And the project can quickly be scaled up. It’s really just a matter of the number of mirrors available and the amount of sand one can heat and store in insulated tanks.
Mirrors, Salt & Solar
More mirrors, more salt, more solar power, and more tanks equal much more energy stored for days. Of course, to scale up the project, a bigger steam turbine is needed, but that shouldn’t be a problem given today’s technology. At the time of writing, the Crescent Dunes plant is able to heat, store and use salt to produce electricity for up to 10 hours without help from the Sun. According to the designers of the solar plant, they could have had the system store a lot more energy if they wanted to. However, Crescent Dunes is the only one of its kind. Think of it as a trial project to see if salt can really store solar energy adequately.
What SolarReserves has done is remarkable. At present time, solar and wind facilities are able to produce electricity only under very specific conditions. And these conditions (such as how much the Sun is shining per day) are out of the control of the operators. An installation like Crescent Dunes is able to store energy when the Sun is shining and release it into the grid as electricity when it is needed. When the solar panels are not able to produce enough electricity, the CSP system immediately intervenes and provides the needed electricity during peak demand times. The CSP solar installation is also able to supply electricity stored over the day throughout the night. There would be no need to depend on other sources of energy.
While solar battery technology has significantly improved over the last couple of years, it is still in its infancy. Companies like Tesla are investing heavily in battery technology (not just for solar purposes), but it takes time to develop efficient batteries that can store large amounts of energy. Thermal storage is a lot more efficient than traditional battery storage it seems. This is why molten salt can preserve the solar energy for a lot more time than a battery could. According to Dietrich, unless the battery industry makes a huge breakthrough, “you’re not really going to get to the level where you’ve got storage on the scale and efficiency of the sort of plant that we’re talking about.”
And it looks like electricity produced from solar energy can become cheaper than electricity obtained from fossil fuels. Currently, Crescent Dunes produces electricity at 13.5 cents for every kilowatt-hour. However, the company SolarReserves stated that its next installations will be able to produce electricity at half this price. And according to the Las Vegas Review Journal, the company is planning to build up to 10 more CSP installations in Nevada. The $5 billion solar project will use more than 100,000 mirrors to concentrate sunlight on 10 towers that will store the solar energy using molten salt. The installations are expected to produce between 1,500 and 2,000 megawatts of energy. This is enough to power one million regular US homes.
It is a very ambitious project, but one that will create likely more than 3,000 new jobs in the solar industry. Any project that can power one million US homes with clean solar energy is an exemplary project! Follow solar news updates to stay tuned when it comes to this ambitious project and ones like it.