This is how solar energy can be stored in “batteries” made from food waste

This is how solar energy can be stored in “batteries” made from food waste

Soon you may be keeping the temperature in your house high in the winter with the help of the heat that leftover food particles borrowed from yesterday’s bright sun.

Everyone knows that the ice on the lakes melts in the spring. The surface of the ice absorbs solar heat, which is enough to melt the ice crystals. Next, the water stores heat. Not many people know that water returns heat to the surroundings again in the fall. Specifically, when it freezes to ice.

Many other substances melt and solidify in the same way.

With the help of the properties of this material, we – a group of researchers in Norway – have come a long way in our work to create a store of green energy for heating homes and cabins. A small tank that stores solar energy and looks like a water heater.

Gets “under the sink” space

One notable feature is that our tank takes up so little space that it fits “under the sink”. The substance in this tank is called “estersParticles are found in abundance in fatty residues, such as leftovers. They can be recovered from used frying oil.

As ice melts, these molecules also absorb heat when the temperature around them rises. Then they mask the heat – and release it again when it gets cold. like the evening.

If the researchers are successful, homes and cabins could be heated this way on cold nights — with the help of solar energy and fatty waste ingredients, such as leftovers. Illustration: Knut Gangåssæter / SINTEF

Many people before us have tried to create these heating systems for the residential sector. without that happening. Nobody has reached our limit. We’ve come so far that we now want to invite the industry into the remaining R&D work.

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Green heat without electric batteries

If we succeed, you can have green heat without relying on large centralized power plants or electric batteries. On freezing days, you should of course have a wood or plank stove as a backup.

In turn, our system can cool rooms on hot days.

The ester molecules that are key to all of this belong to the family of “phase change substances”. These materials melt (and absorb heat) when the temperature rises above a certain range. Then it hardens (and releases heat) when the temperature drops below the same line.

Perfect fabric for temperature regulation in homes

Thousands of such materials exist. The temperature at which the change takes place varies from one substance to another. If bio-based, the “magic point” can lie between minus 50 and plus 275 degrees. “Our” esters give off heat at 30 degrees. It is ideal for regulating the temperature in homes.

The ability of many materials to store and then release heat has been used in many inventions. Including me Smart helicopter suits For use abroad. When the passengers in the suit sweat, they are cooled. This is because a phase change material in the suit steals body heat until it melts.

If the helicopter crashes and ends up in the sea, the opposite happens. The “interiors” of the suit then harden and return heat to the cold bodies.

At Sintef, we take this a step further – to your home and cottage.

Two victories at once

The goal is twofold:

Stores energy from the sun

In our solution, we allow the solar cells, on the roof of the house or elsewhere, to generate the electricity that heats the water. The water is allowed to flow through the small tank in the house. It also contains a block of hardened esters.

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When the solar energy heats the water, the esters dissolve and store the solar energy.

In the evening, when heating is needed, we leave it cold Water flows through the tank. In a closed tube loop, the water carries the heat from the esters onwards. In cold rooms at night, the water radiates its heat through heating fans and radiators, until all the ester in the tank has solidified.

“Overcurrent” can be used from wind turbines as well

In the same way, we can use wind energy when energy demand is low: let the “excess energy” from wind turbines melt the esters. If we succeed, then so be it everyone Cheap electricity can be used in this way when the price of electricity is different.

In a tank like ours, the usual thing would be to use heat exchangers. So let the water flow into the tank, separated from the ester by thin metal walls. And then the heat carried by the water is transferred to the esters through these walls.

But these parts are expensive, take up space, and weigh a lot. This would increase the volume and price of utilities.

Instead, we chose to exchange heat by allowing the water flow to come into direct contact with the esters. Therefore, our tank takes up only a fifth of the space needed by the water heater.

Uses knowledge from oil research

The effect depends on how well the two liquids are mixed. Chemistry is difficult to control in such systems. This also applies to the flow process. But we know such droplets in Syntv from research into technology that allows oil to be sent long distances along with water from oil wells, in the same pipeline.

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We are one of the few solutions-driven environments without Heat exchangers – among the first to achieve this. The result is thus an energy store suitable for use in homes and cabins, especially where space is limited.

In addition, the system can be used in industrial facilities to store and use waste heat.

What if the sun didn’t shine day in and day out during the heating season? We’ve thought about that too. Use a small electric oven to melt esters when electricity is cheap and there isn’t much to use electricity for. It’s the simple backup solution you need.

The post was first published on Tu la June 20, 2023 and reproduced here with permission from TU.

Dalila Awolowo

Dalila Awolowo

"Explorer. Unapologetic entrepreneur. Alcohol fanatic. Certified writer. Wannabe tv evangelist. Twitter fanatic. Student. Web scholar. Travel buff."

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