Energy

Abundant silicon at the heart of cheaper renewable energy storage system

As one of the Earth's crust's most abundant elements, silicon could form the basis of a cheaper  storage system for renewable energy
As one of the Earth's crust's most abundant elements, silicon could form the basis of a cheaper  storage system for renewable energy
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The new energy storage system uses heat from sunlight, or electricity from other renewables, to heat the molten silicon then draw back the electricity later using thermophotovoltaic cells
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The new energy storage system uses heat from sunlight, or electricity from other renewables, to heat the molten silicon then draw back the electricity later using thermophotovoltaic cells
Silicon before and after melting
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Silicon before and after melting
As one of the Earth's crust's most abundant elements, silicon could form the basis of a cheaper  storage system for renewable energy
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As one of the Earth's crust's most abundant elements, silicon could form the basis of a cheaper  storage system for renewable energy

A team of researchers from Madrid is developing a thermal energy storage system that uses molten silicon to store up to 10 times more energy than existing thermal storage options. The hope is to develop the technology into a new generation of low-cost solar thermal stations to store solar energy in urban centers.

Storage is the current major challenge faced by renewable energy sources like wind and solar – so if these are to become viable alternatives, drastic improvements to our ability to store surplus energy are required so that cities can draw on that energy at night, and at other times when the sun isn't shining or the wind isn't blowing.

Current battery technology just isn't developed enough yet, so researchers across the industry have been exploring a range of new ideas to improve energy storage, including a commercialized solar thermal energy system that stores concentrated heat from the sun in the form of molten salts (potassium/calcium/sodium nitrates etc.), and converts the heat back to electricity via a thermal generator.

Salt-based systems work quite well, but they require complex pumps, pipelines and heat transfer fluids to generate electricity, making them expensive and vulnerable to safety issues. They're also not based on particularly abundant materials – if we scale up the use of these plants, we could find ourselves running low on the elements needed to make these salts within a few decades. That's why researchers worldwide are looking for safer alternatives that use cheaper and more abundant materials.

The silicon-based solution proposed by the team from the Universidad Polytechnic de Madrid (UPM) could be a winner because silicon is one of the world's cheapest and most abundant elements – second only to oxygen.

The proposed new thermal energy storage system involves heating the silicon in a container using either concentrated sunlight on surplus electricity generated by renewable power. The molten silicon – which can reach temperatures of around 1,400° C (2,552° F) – can be isolated from its environment until energy is needed, at which point the heat is converted to electricity. Silicon's unique properties allow it to store more than 1 MWh of energy in a cubic meter – ten times more energy than salts.

The key to making the new system work, according to research leader Alejandro Datas, is the use of thermophotovoltaic cells – a fairly new technology that sees solar panels generating electricity from heat as well as light.

"At such high temperatures, silicon intensely shines in the same way that the Sun does," says Datas. "Thus thermophotovoltaics can be used to convert this incandescent radiation into electricity."

Thermophotovoltaic cells can reach conversion efficiencies of over 50 percent and can produce 100 times more electrical power per unit area than conventional solar cells. Datas says they are key to the system – not least because they can work at extreme temperatures, unlike other generators.

The system certainly sounds like it ticks a lot of boxes: it uses abundant, inexpensive materials, is able to store up to 10 times more energy than existing solutions and is extremely compact and quiet, with no moving parts.

The researchers believe their invention could dramatically reduce the cost of storing and producing energy in the thermal energy sector. It could also offer a safe, cost-effective answer to the renewable sector's energy storage woes, and could be used for heating as well is electricity.

The UPM team is now looking to commercialize the system. Towards that end, they have founded a business project called SILSTORE and have started building a laboratory-scale prototype.

You can read a paper about the system in the journal Energy.

Source: UPM

11 comments
Peter Kelly
Given that the energy from the sun far exceeds what we use (we just don't have the capability to utilise it) then any method to efficiently gather and store it is very welcome indeed. Sadly, though, I expect that for the world to really profit from such technology would require extraordinary cooperation, making use of those areas of the planet which have the most intense and constant sun to be used to provide universal power. Given the state we are in now, I can't see that happening!
VincentWolf
I disagree with Kelly. There is so much desert out there for the taking unused, unappreciated. It will happen when the technology is there. And this is a good news for the entire planet.
mike65401
Isn't glass mostly molten silica? Peter Kelly. 25% of all power generated is lost in transmission. It is not efficient to concentrate solar collectors in dry climates and then transmit to more cloudy regions. BTW, just think of how much more solar development could be implemented in the US if the money wasted on corn alcohol was spent on solar.
D_trigger2113
pretty sure silicon and oxygen aren't elements last time I checked.
EZ
This is good example of how the "energy-industrial complex" works. I knew a man, who had a better option than salt about 30 years ago. It was called sand. The government didn't want it but never explained why not. Maybe it was too cheap.
Douglas Bennett Rogers
Silicon and oxygen are elements. Look at the periodic table. When desert solar becomes cost competitive it will attract population, as with past energy revolutions.
Don Duncan
Geothermal requires no storage, is viable in the entire state of Nevada, and ticks every box. Given no politics, it would be our main source of energy. Fix the tax & regulate problem that is transferring wealth from the 99.9%, and killing innovation, then all our other problems will be solved by a "freed up market".
StWils
Great step forward! Like many ideas deploying it successfully is location dependent. This is an example of a technology that should work out well in many hot dry climates. Few people know that in Niagara Falls NY, there is a huge man made pond that is filled up slowly at night by diverting some of the water flow overnight. During the day the stored water is shunted to turbines so that the falls can flow at full force while tourists are around. While the Falls are never really "turned off" to store water enough is diverted to enable stable high quality energy generation to support daytime demands. This molten salt approach and others are similarly capable of matching demand to an otherwise irregular source. I hope this succeeds and that the Kochs & other Oligopolists do not get a dime. Now, that would really require a suspension of disbelief.
Daniel Gregory
Once it reaches molten temperatures of 2550 F, what is used to contain such heat? What keeps it from cooling down? Why is no one talking about the super-capacitor like capabilities of graphene?
JasonDavidSteel
" Silicon's unique properties allow it to store more than 1 MWh of energy in a cubic meter – ten times more energy than salts." 4 questions that this non-physicist wants to make- [1]-Is that higher energy density than lithium based battery storage? It's definitely easier to mine/refine than lithium, and way more abundant. [2]-Could this tech solve the issues of cabin heating in an EV? [3] Are thermophotovoltaics more efficient than a steam turbine? [4]- How do super capacitors fit into this mix??