This may or may not have its uses, but any idea that the whole world could get electricity mainly from the sun and the wind is not credible, with today’s technology at least.
MIT engineers have come up with a conceptual design for a system to store renewable energy, such as solar and wind power, and deliver that energy back into an electric grid on demand, says TechExplore.
The system may be designed to power a small city not just when the sun is up or the wind is high, but around the clock.
The new design stores heat generated by excess electricity from solar or wind power in large tanks of white-hot molten silicon, and then converts the light from the glowing metal back into electricity when it’s needed.
The researchers estimate that such a system would be vastly more affordable than lithium-ion batteries, which have been proposed as a viable, though expensive, method to store renewable energy. They also estimate that the system would cost about half as much as pumped hydroelectric storage—the cheapest form of grid-scale energy storage to date.
“Even if we wanted to run the grid on renewables right now we couldn’t, because you’d need fossil-fueled turbines to make up for the fact that the renewable supply cannot be dispatched on demand,” says Asegun Henry, the Robert N. Noyce Career Development Associate Professor in the Department of Mechanical Engineering. “We’re developing a new technology that, if successful, would solve this most important and critical problem in energy and climate change, namely, the storage problem.”
Henry and his colleagues have published their design today in the journal Energy and Environmental Science.
Record temps
The new storage system stems from a project in which the researchers looked for ways to increase the efficiency of a form of renewable energy known as concentrated solar power.
Unlike conventional solar plants that use solar panels to convert light directly into electricity, concentrated solar power requires vast fields of huge mirrors that concentrate sunlight onto a central tower, where the light is converted into heat that is eventually turned into electricity.
“The reason that technology is interesting is, once you do this process of focusing the light to get heat, you can store heat much more cheaply than you can store electricity,” Henry notes.
Concentrated solar plants store solar heat in large tanks filled with molten salt, which is heated to high temperatures of about 1,000 degrees Fahrenheit. When electricity is needed, the hot salt is pumped through a heat exchanger, which transfers the salt’s heat into steam. A turbine then turns that steam into electricity.
“This technology has been around for a while, but the thinking has been that its cost will never get low enough to compete with natural gas,” Henry says. “So there was a push to operate at much higher temperatures, so you could use a more efficient heat engine and get the cost down.”
However, if operators were to heat the salt much beyond current temperatures, the salt would corrode the stainless steel tanks in which it’s stored. So Henry’s team looked for a medium other than salt that might store heat at much higher temperatures.
They initially proposed a liquid metal and eventually settled on silicon—the most abundant metal on Earth, which can withstand incredibly high temperatures of over 4,000 degrees Fahrenheit.
Last year, the team developed a pump that could withstand such blistering heat, and could conceivably pump liquid silicon through a renewable storage system. The pump has the highest heat tolerance on record—a feat that is noted in “The Guiness Book of World Records.”
Since that development, the team has been designing an energy storage system that could incorporate such a high-temperature pump.
Continued here.
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December 6, 2018 at 04:58AM
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