This energy storage technology won the 2022 EU Best Innovation Award, 40 times cheaper than lithium-ion battery

Thermal energy storage using silicon and ferrosilicon as the medium can store energy at a cost of less than 4 euros per kilowatt-hour, which is 100 times

cheaper than the current fixed lithium-ion battery. After adding the container and insulation layer, the total cost may be about 10 euros per kilowatt-hour,

which is much cheaper than the lithium battery of 400 euros per kilowatt-hour.

Developing renewable energy, building new power systems and supporting energy storage are a barrier that must be overcome.

The out-of-the-box nature of electricity and the volatility of renewable energy generation such as photovoltaic and wind power make the supply and demand

of electricity sometimes mismatched. At present, such regulation can be adjusted by coal and natural gas power generation or hydropower to achieve stability

and flexibility of power. But in the future, with the withdrawal of fossil energy and the increase of renewable energy, cheap and efficient energy storage

configuration is the key.

Energy storage technology is mainly divided into physical energy storage, electrochemical energy storage, thermal energy storage and chemical energy storage.

Such as mechanical energy storage and pumped storage belong to physical energy storage technology. This energy storage method has relatively low price and

high conversion efficiency, but the project is relatively large, constrained by geographical location, and the construction period is also very long. It is difficult to

adapt to the peak shaving demand of renewable energy power only by pumped storage.

At present, electrochemical energy storage is popular, and it is also the fastest growing new energy storage technology in the world. Electrochemical energy

storage is mainly based on lithium-ion batteries. By the end of 2021, the cumulative installed capacity of new energy storage in the world has exceeded 25 million

kilowatts, of which the market share of lithium-ion batteries has reached 90%. This is due to the large-scale development of electric vehicles, which provides a

large-scale commercial application scenario for electrochemical energy storage based on lithium-ion batteries.

However, lithium-ion battery energy storage technology, as a kind of automobile battery, is not a big problem, but there will be many problems when it comes to

supporting grid-level long-term energy storage. One is the problem of safety and cost. If lithium ion batteries are stacked on a large scale, the cost will multiply,

and the safety caused by heat accumulation is also a huge hidden danger. The other is that lithium resources are very limited, and electric vehicles are not enough,

and the need for long-term energy storage cannot be met.

How to solve these realistic and urgent problems? Now many scientists have focused on thermal energy storage technology. Breakthroughs have been made in

relevant technologies and research.

In November 2022, the European Commission announced the award-winning project of the “EU 2022 Innovation Radar Award”, in which the “AMADEUS”

battery project developed by the team of the Madrid Institute of Technology in Spain won the EU Best Innovation Award in 2022.

“Amadeus” is a revolutionary battery model. This project, which aims to store a large amount of energy from renewable energy, was selected by the European

Commission as one of the best inventions in 2022.

This kind of battery designed by the Spanish scientist team stores the excess energy generated when solar or wind energy is high in the form of thermal energy.

This heat is used to heat a material (silicon alloy is studied in this project) to more than 1000 degrees Celsius. The system contains a special container with the

thermal photovoltaic plate facing inward, which can release part of the stored energy when the power demand is high.

The researchers used an analogy to explain the process: “It’s like putting the sun in a box.” Their plan may revolutionize energy storage. It has great potential to

achieve this goal and has become a key factor in tackling climate change, which makes the “Amadeus” project stand out from more than 300 projects submitted

and won the EU Best Innovation Award.

The organizer of the EU Innovation Radar Award explained: “The valuable point is that it provides a cheap system that can store a large amount of energy for a

long time. It has high energy density, high overall efficiency, and uses sufficient and low-cost materials. It is a modular system, widely used, and can provide

clean heat and electricity on demand.”

So, how does this technology work? What are the future application scenarios and commercialization prospects?

To put it simply, this system uses the excess power generated by intermittent renewable energy (such as solar energy or wind energy) to melt cheap metals,

such as silicon or ferrosilicon, and the temperature is higher than 1000 ℃. Silicon alloy can store a large amount of energy in its fusion process.

This type of energy is called “latent heat”. For example, a liter of silicon (about 2.5 kg) stores more than 1 kilowatt-hour (1 kilowatt-hour) of energy in the form

of latent heat, which is exactly the energy contained in a liter of hydrogen at 500 bar pressure. However, unlike hydrogen, silicon can be stored under atmospheric

pressure, which makes the system cheaper and safer.

The key of the system is how to convert the stored heat into electric energy. When silicon melts at a temperature of more than 1000 º C, it shines like the sun.

Therefore, photovoltaic cells can be used to convert the radiant heat into electrical energy.

The so-called thermal photovoltaic generator is like a miniature photovoltaic device, which can generate 100 times more energy than traditional solar power plants.

In other words, if one square meter of solar panels produces 200 watts, one square meter of thermal photovoltaic panels will produce 20 kilowatts. And not only

the power, but also the conversion efficiency is higher. The efficiency of thermal photovoltaic cells is between 30% and 40%, which depends on the temperature

of the heat source. In contrast, the efficiency of commercial photovoltaic solar panels is between 15% and 20%.

The use of thermal photovoltaic generators instead of traditional thermal engines avoids the use of moving parts, fluids and complex heat exchangers. In this way,

the whole system can be economical, compact and noiseless.

According to the research, latent thermal photovoltaic cells can store a large amount of residual renewable power.

Alejandro Data, a researcher who led the project, said: “A large part of these electricity will be generated when there is surplus in wind and wind power generation,

so it will be sold at a very low price in the electricity market. It is very important to store these surplus electricity in a very cheap system. It is very meaningful to

store the surplus electricity in the form of heat, because it is one of the cheapest ways to store energy.”

2. It is 40 times cheaper than lithium-ion battery

In particular, silicon and ferrosilicon can store energy at a cost of less than 4 euros per kilowatt-hour, which is 100 times cheaper than the current fixed lithium-ion

battery. After adding the container and insulation layer, the total cost will be higher. However, according to the study, if the system is large enough, usually more

than 10 megawatt hours, it will probably reach the cost of about 10 euros per kilowatt hour, because the cost of thermal insulation will be a small part of the total

cost of the system. However, the cost of lithium battery is about 400 euros per kilowatt-hour.

One problem this system faces is that only a small part of the stored heat is converted back to electricity. What is the conversion efficiency in this process? How to

use the remaining heat energy is the key problem.

However, the team’s researchers believe that these are not problems. If the system is cheap enough, only 30-40% of the energy needs to be recovered in the form of

electricity, which will make them superior to other more expensive technologies, such as lithium-ion batteries.

In addition, the remaining 60-70% of the heat not converted into electricity can be directly transferred to buildings, factories or cities to reduce coal and natural

gas consumption.

Heat accounts for more than 50% of global energy demand and 40% of global carbon dioxide emissions. In this way, storing wind or photovoltaic energy in latent

thermal photovoltaic cells can not only save a lot of costs, but also meet the huge heat demand of the market through renewable resources.

3. Challenges and future prospects

The new thermal photovoltaic thermal storage technology designed by the team of Madrid University of Technology, which uses silicon alloy materials, has

advantages in material cost, thermal storage temperature and energy storage time. Silicon is the second most abundant element in the earth’s crust. The cost

per ton of silica sand is only 30-50 dollars, which is 1/10 of the molten salt material. In addition, the thermal storage temperature difference of silica sand

particles is much higher than that of molten salt, and the maximum operating temperature can reach more than 1000 ℃. Higher operating temperature also

helps to improve the overall energy efficiency of the photothermal power generation system.

Datus’s team is not the only one who sees the potential of thermal photovoltaic cells. They have two powerful rivals: the prestigious Massachusetts Institute of

Technology and the California start-up Antola Energy. The latter focuses on the research and development of large batteries used in heavy industry (a large

fossil fuel consumer), and obtained US $50 million to complete the research in February this year. Bill Gates’ Breakthrough Energy Fund provided some

investment funds.

Researchers at the Massachusetts Institute of Technology said that their thermal photovoltaic cell model has been able to reuse 40% of the energy used to heat

the internal materials of the prototype battery. They explained: “This creates a path for maximum efficiency and cost reduction of thermal energy storage,

making it possible to decarbonize the power grid.”

The project of the Madrid Institute of Technology has not been able to measure the percentage of energy it can recover, but it is superior to the American model

in one aspect. Alejandro Data, the researcher who led the project, explained: “In order to achieve this efficiency, the MIT project must raise the temperature to

2400 degrees. Our battery works at 1200 degrees. At this temperature, the efficiency will be lower than theirs, but we have much less heat insulation problems.

After all, it is very difficult to store materials at 2400 degrees without causing heat loss.”

Of course, this technology still needs a lot of investment before entering the market. The current laboratory prototype has less than 1 kWh of energy storage

capacity, but to make this technology profitable, it needs more than 10 MWh of energy storage capacity. Therefore, the next challenge is to expand the scale of

the technology and test its feasibility on a large scale. In order to achieve this, researchers from the Madrid Institute of Technology have been building teams

to make it possible.