This is the Spanish invention that could end the dependence on fossil fuels.

However, there is a technological problem: There is no system that can economically store and produce this energy on demand. A group of Spanish researchers seem to have found the solution by discovering a photovoltaic battery system with enormous storage potential at low cost over long periods of time. and optionally providing heat and electricity.

The finding is the work of researchers from the Institute of Solar Energy at the Polytechnic University of Madrid (IES-UPM). Described in an article titled ‘Hidden Heat Thermophotovoltaic Batteries’ published in the scientific journal ‘Joule’, system uses surplus generation from intermittent renewable energy such as solar or wind to melt cheap metalsSuch as silicon or ferrosilicon alloys at temperatures above 1,000ºC.

Silicon alloys can store large amounts of energy during fusion processes.. This type of energy is calledlatent heat”.

For example, one liter of silicon stores more than one kWh of energy in the form of latent heat; this is exactly the amount of energy contained in one liter of hydrogen pressurized at 500 bar. Again, unlike hydrogen, silicon can be stored at atmospheric pressurewhich makes the system potentially cheaper and safer.

Miniature photovoltaic plants

The system, already patented by UPM researchers, combines thermionic and photovoltaic effects, direct conversion of heat to electricity.

Unlike traditional thermal machines, this system does not require physical contact with the thermal sourcesince it is based on the direct emission of electrons (thermionic effect) and photons (thermophotovoltaic effect).

One key to the system refers to the way stored heat is converted into electricity. Silicon shines like the sun when it melts above 1,000ºC. Therefore, it is possible to convert the radiated heat back into electricity using photovoltaic cells..

The so-called thermophotovoltaic generators are like miniature photovoltaic plants What can generate up to 100 times more power than a conventional solar power plant. In other words: if one square meter of solar panel produces 200 W, one square meter of thermophotovoltaic panel produces 20 kW. And not only is the power greater; efficiency as well.

Because the efficiency of thermophotovoltaic cells varies between 30% and 40% depending on the temperature of the heat source, while the efficiency of commercial photovoltaic solar panels varies between 15% and 20%. My love.

Use of thermophotovoltaic generators instead of conventional heat engines (such as Stirling, Brayton or Rankine cycles), avoids the use of moving parts, fluids or complex heat exchangers. Like this, the whole system can be made economical, compact and quiet. All are advantages.

A hundred times cheaper than lithium batteries

According to research, latent heat thermophotovoltaic batteries can store large amounts of excess renewable electricity. “Most of this electricity will be produced when there is no demand, so it will be sold. very cheap Says Alejandro Datas, researcher and project leader at IES-UPM.

“Storing this electricity in a very cheap system is essential, as it wouldn’t make sense to store something this cheap in a very expensive box. Like this, Storing excess electricity as heat makes a lot of sense because it’s one of the cheapest ways to store energy.”, the researcher continues.

Especially, silicon and ferrosilicon alloys can store energy at less than 4 euros per kWh, which is 100 times cheaper than current stationary lithium-ion batteries..

It is true that the total cost will be higher after the container and thermal insulation are included, but also as detailed in the study, If the system is large enough, it will be possible to reach costs of around 10 euros per kWh.typically more than 10 MWh, because the cost of thermal insulation will be a small fraction of the total cost of the system”.

It is not a problem to convert only some of the heat stored in these latent heat batteries back into electricity. “If the system is cheap enough, they would only need to recover 30% or 40% of their energy as electricity to make them preferable to other more expensive technologies.It’s like lithium-ion batteries,” the researchers say.

First prototype ready

60% or 70% of the heat that cannot be converted to electricity can be given directly to buildings, factories or cities, reducing natural gas consumption.

Heat accounts for more than 50% of global energy demand and 40% of global CO2 emissions. In this way, storing wind or photovoltaic energy in thermophotovoltaic latent heat cells will not only provide significant cost savings, but will also meet some of this huge heat demand through renewable sources.

So, “Developing such a system could be the key to reducing our dependence on fossil fuelsNot only in the electricity sector, but also in the thermal sector,” Datas concludes.

This first prototype Built within the framework of a laboratory-scale European project (AMADEUS), the system is now available at IES-UPM and the first experimental results are published in the study.

This is the pinnacle More than 10 years of research at IES-UPM. Again, technology still needs a lot of investment to reach marketpoints out the University of Madrid. For example, the current laboratory prototype has less than 1 kWh of storage capacity, but energy storage capacities of more than 10 MWh are needed for this technology to be profitable.

The next challenge is to scale the technology and test its feasibility at scale.. To do this, IES-UPM researchers are already putting together the team that will make this possible.

Reference report: https://www.sciencedirect.com/science/article/abs/pii/S2542435122000423?via%3Dihub