A new type of efficient battery

Researchers from Harvard report a metal-free flow battery based on the electrochemistry of small, cheap and common organic molecules called quinones, which are similar to those molecules that store energy in plants and plants.

A team of researchers and engineers from Harvard University demonstrated a new type of battery that could fundamentally change the way electricity is stored in the electrical grid, a result that could make the production of electricity from renewable energy sources, such as the wind or the sun, cheaper and more reliable.

A new article reports on a metal-free flow battery based on the electrochemistry of small, cheap and common organic molecules called quinones, which are similar to those molecules that store energy in plants and plants.

The lack of coordination between the temporary availability of wind or sunlight and the variability of electricity demand is the biggest obstacle to supplying a significant share of the electricity consumed by humans from renewable sources. Economical means of storing significant amounts of electrical energy could solve this problem.

The new battery was driven, built and tested in the laboratory of Professor Tracy Sykes from the Department of Materials and Energy Technologies at Harvard University. Professor of Chemistry and Chemical Biology Alán Aspuru-Guzik used his sophisticated molecular screening methods to calculate the properties of more than ten thousand quinone molecules in search of the most suitable candidates for this battery.

Flow batteries store energy content in the form of chemical liquids that are in external tanks - similar to fuel cells - instead of inside the battery tank itself. The two main components - the device responsible for converting the electrochemical energy and the containers that store the chemicals, can be separated. However, the amount of energy that can be stored is limited only by the size of the containers. The new design of the team of researchers allows the storage of a larger amount of energy at a lower cost than in common batteries.

In contrast, in solid electrode type batteries, which are commonly found in car batteries and portable devices, the two different components (the conversion device and the chemical container) are packed together in one unit and cannot be separated. As a result, they are able to store only transient energy that comes from renewable sources.

"Our studies show that an amount of energy storage of between one and two days is required in order to flow the energy that comes from the sun or the wind through the existing electricity grid," explains the researcher. In order to store 50 hours of energy from a wind turbine with a capacity of one megawatt (50 megawatt hours), for example, you can use the solution of buying ordinary batteries with a capacity of 50 megawatt hours, but they will require the purchase of 50 megawatts of capacity . Paying for 50 megawatts of capacity when we only need 1 megawatt is not a very economical solution."

Due to this reason, an increasing number of engineers are beginning to focus their research attention on flow battery technologies. However, to date, flow batteries have been based on chemicals that were expensive or complex to store, increasing energy storage costs. The active components in the electrolytes in most of the flow batteries have been metals until now. Vandium metal is used in most of the commercial advanced technologies in the field of flow batteries that are under development today, but its relatively high price makes it difficult to produce cheap batteries. Other flow batteries include expensive metallic electrolytes such as the platinum metal used in fuel cells. The new flow battery developed by the Harvard research team already operates at the same level of efficiency as flow batteries based on the metal vanadium, with the help of much less expensive chemicals, and without any use of electrolytes containing expensive metals.

"In the field of energy storage, everyone uses metal ions in various configurations, but there are a limited number of them that you can put into a solution used for energy storage, and none of them can cost-effectively store huge amounts of renewable energy," explains the lead researcher. "By using organic molecules, we present a completely new set of possibilities. Some will be bad and some will be very successful. The quinones we found are the first that seem really successful for this use." "This project demonstrates the power of the collaboration between sophisticated quantum chemistry and experimental chemistry in the laboratory," he adds. "Within a very short period of time, our team was able to reach the right molecule. Computer screening, together with laboratory experiments, can lead to the discovery of new materials for many applications."

Quinone molecules are abundant in crude oil as well as in green plants. The molecule used by the research team in the first ever quinone-based flow battery is almost identical to the one found in the rhubarb plant. These molecules dissolve in water, which prevents them from being flammable.

In order to back up a commercial turbine, a large storage tank will be needed, one that can be placed in an underground basement, explains one of the researchers. If you have a whole field of turbines or a large solar farm, you can imagine several very large storage tanks.

The same technology could also be applicable at the consumer level, explains the researcher. "Imagine a tank the size of a kerosene stove in your basement. Such a tank could store the amount of energy that comes from a full day of sunlight while utilizing solar panels on the roof of the house, and provide enough energy for domestic consumption during the evening and the whole night, without burning any fuel ."

In the next steps, the researchers plan to further test and further improve the initial system and advance it to a commercial level. "Until now, we have not seen any wear after more than a hundred cycles, but commercial applications require the utilization of thousands of cycles," explains the lead researcher. In addition, they are particularly optimistic about finding even more effective molecules.

The researchers anticipate that at the end of the three years of initial research, they will be able to present demonstration versions of an organic flow battery housed within a unit the size of a horse trailer. Such a portable storage system could be connected to solar panels located on the roofs of commercial buildings and directly supply the energy consumption of the building or store the energy that is not used for periods of demand at a later date.

"In principle, when the system is proven to be efficient and economical, it will be possible to connect it to any of the power poles that conduct electricity within the existing power grid," explains the chief researcher. "In addition, the system is useful for storing energy in times when the price of electricity is high and selling it back at the higher price. Moreover, these units will avoid the need to build power plants that run on gas or coal that pollute the environment. This kind of system could also be especially useful in those areas where the electricity network is limited or does not exist at all.

"In conclusion, the problem of temporary storage of energy from renewable sources is the biggest obstacle to getting most of our energy from the sun and the wind," notes the lead researcher. "A safe and cheap flow battery could take an important step in humanity's transition from using fossil fuels to using fuels from renewable sources. I'm glad we have a good chance of that."

The news about the study