Is it going to be concentrated solar power systems using molten salt or photovoltaic panels that are best suited to send wattage to the grid?
Even though researchers at the Massachusetts Institute of Technology (MIT) might have solved some of the technological issues associated with molten salt storage, solar entities operating in the Mojave Desert now seem more willing to use PV panels to deliver affordable solar-powered electricity.
Earlier this month, though, solar energy writer Jason Deign wrote that the MIT team had flipped the solar tower concept on its head. He cited a paper published in Solar Energy, in which MIT Pappalardo Professor of Mechanical Engineering Alexander Slocum and co-workers proposed building a heliostat field on a hillside and focusing sunlight onto a combined heating and storage tank below it. Said tank, filled with molten sodium-potassium nitrate salt, would admit concentrated sunlight through a narrow opening on its top and would contain a movable plate to separate the hot liquid at the surface from colder layers below.
The top layer of hot molten salt, which the researchers say could reach more than 500 degrees Celsius, would be used to drive a turbine and then returned to the bottom of the tank. In daytime operation the plate would move down the tank as the volume of hot salt on top increased.
How to best store electricity without sunshine remains cemented as a central question to any solar electricity infrastructure. In their vision, the MIT team believes that a CSP on-demand (CSPoD) tank measuring 25 meters across by five deep could provide 20 MW of electric power 24 hours a day, while storing enough heat over 10 days of sunshine to continue electricity generation for a full day without any sunlight.
Deign points out: “At the same time, though, CSPoD removes much of the complexity, and cost, associated with tower configurations; since the heat receptor and storage medium are the same, there is less need for plumbing, which simplifies construction and maintenance.”
Another potential stumbling block for CSPoD, which so far has only been tested conceptually in the MIT basement, is that it may lose out to a growing number of other storage options that are available.
To this end, it should be added: the more the merrier, and the sooner the better.
Photo: Nevada Solar One ldrose