Solar energy is everywhere. From dawn until dusk, the sun’s rays beat down on Earth, providing warmth and light.
The solar energy hitting Earth each year exceeds the total energy consumed by humanity by more than 20,000 times.
But once the sun sets, or clouds fill the sky, our supply of solar energy is cut off.
So how do we store solar energy to provide electricity at night?
The obvious solution of storing the energy in batteries is presently not economical at the massive solar power plant scale.
Other options, of compressing and uncompressing air, or pumping water up a slope to use the energy it generates when it flows downhill, are all energy intensive themselves and require large storage areas or riverbeds.
The best answer today lies in thermal energy storage (TES) and heat transfer – using the sun’s energy to heat a material up and then using that heat to create steam on demand that can power a turbine and so generate electricity.
In concentrated solar power (CSP) plants, molten salts have been the material of choice to store solar energy since the 1980s.
The molten salt system uses concentrated solar energy to heat up nitrate salts and then, when solar energy is not available, using that heat to create steam to generate electricity from a turbine.
The material we need to store the thermal energy is one that is in plentiful supply in the UAE – sand and the deserts in Saudi and the gulf region.Special sand crystal that act as thermal storage units.
Sand has many promising properties – it is cheap and it can store thermal energy at a higher temperature of 1000°C against molten salts’ 600°C. That means hotter steam for the turbine and more efficient electricity production.
The sand-based energy storage system the Masdar Institute is developing will do away with heat transfer fluids, pumps and pipes, resulting in a significant reduction in operation cost.
The technology that Masdar Institute’s thermal energy storage research team is designing would use two tanks of sand, using gravity to transfer it from one tank to the other, as in an hourglass.
The upper tank will hold the “cold” (but still 250°C) sand, with the heated (800°C) sand in the lower tank.
This cold tank will be in the shape of a hollow cylinder, with the beam of energy from the solar reflectors down the middle. When a valve is opened, the sand will flow into the path of this beam, and the concentrated solar energy will heat it up. Then the hot sand is recovered and stored in the lower tank until energy is needed.
To discharge the system, a heat exchanger is immersed in the heated moving sand, producing superheated steam that runs the turbine.
The cooled sand is then sent back to the top of the cold tank by a conveyer belt to close the loop of this continuous process.
This technology, once perfected, should provide the UAE’s solar ambitions with an efficient, cost-effective and environmentally friendly way to store energy for CSP plants 24 hours a day, seven days a week.
It can also later be adapted to other industrial processes, such as steel making, that produce waste heat that could be used to heat the sand – and thus reduce the net energy use of these facilities.
With this research, UAE will reach its targets for renewable energy integration and carbon footprint reduction while providing its economy with a lucrative and high-demand innovation. USA can do that in their desert same thing can be done in Africa, Iraq, and every country has a desert.
using sand will reduce significantly the cost of the storage system.
The transport of sand is not a problem in a desert countries but it will be a problem with countries that do not have desert sands, for transport logistic problem.
What goes up must come down. Again the technologies is adding another item that makes solar energy too expensive … why moving the sand or the molten salt , it will be more economical not to do so , fix them and just keep moving the concentrated sun rays to heat the sand bed from many directions or the salt . It is well known in European housing to store heat from burning gas into brick walls when gas prices is low in the day and use in the time when gas price is high. The same can be done. Just make a pool of molten salt and impress the heat exchanger inside .
We must teach the engineers of the future to build a house that use the heat from a sand bed , that heat storage with a sand bed under the house , that could collect heat starting in late summer and release it slowly during the winter. It seemed like an intrinsically good idea to store up heat ahead of time and use it like a battery to provide it later on when needed.
Climate the solar energy system begins to heat the sand bed in early to mid-August….It takes about a month to get the sand bed saturated with heat, and then the temperature inside the building is regulated by judicious opening and closing of windows.
Anyone who considers this should be aware of is that if this is the only form of in-floor heat you will be able to use for that part of your house, This is a good news/bad news scenario. Sand beds are slow to collect their heat charge and give it off slowly and as the winter progresses, it will gradually loose its heat. Then there is a cool mass under your floor.
Some people attempt to get around this with 2 loops of tubing. One right under the floor to provide quicker heat, and one further down. This is not a perfect solution because even the upper loop will radiate its heat both up and down. It’s not like air convection where heat rises and cold air falls.
A sand bed is exceptionally unresponsive. You can’t crank up the thermostat and get more heat later today. There will be a lag time of many days before the heat soaked up on a sunny day is available for use in the house. It might take most of a week – or longer. After all, it took a month or more to fully heat the sand bed during the time of year when days are long and sun is strong.
We can use this method also in other planet? who knows.
If you want to try to keep a deep sand bed warm with solar panels, you will need a LOT of them. Everything has its environmental cost, and building and transporting more panels than needed is part of the big picture. You can’t use solar for the coldest, darkest part of the winter without a lot of waste in the system the rest of the year.
Several experienced installers can fix the problem by keeping the heat in the hot water tank and deploy it to a relatively thin (2” – 5”), well insulated floor as needed.
Heat is the fact of life in the future as our earth is heating up year after year. the war of the future will be the war for water and not for oil and gas. Water will be like gold. heat energy from the sun and sand will cut the price of electricity. The future human in earth will have to adopt to the new wave of heat and the sun solar radiation flair . human skin will change , human eyes and night will change, human will be able to work at night most of the time to avoid the sun radiation and human will have eyes with infra red ability .
Thank you for reading
Steve Ramsey, PhD. Calgary, Canada.