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One of the major downsides to renewable energy sources is the reliability of power generation. Solar Power is only giving us power when the sun is shining and Wind Power is productive while the wind is blowing.

The demand for power is often highest at night when there is no sun and possibly no wind.

And renewable energy is wasted when there is more produced than is needed at that moment.

So the solution is to pair renewable energy sources with an energy storage system (aka a battery).

If you have a storage mechanism then you can store the energy when it is readily available from the sun or wind and save it for later when you really need it.

The issue is that the current battery technology, Lithium Ion cells, is expensive to produce and involves mining lithium which is rare and in high demand already due to the popularity of electric cars. And as governments around the world mandate the end of gas-guzzling vehicles the demand for lithium is increasing.

There have been a lot of alternatives proposed including Molten Salt Batteries, Gravity Batteries, and Compressed Air Batteries.

But the one that recently caught my eye is the Sand Battery!

What are Sand Batteries?

Sand batteries are a type of energy storage technology that uses sand as a medium for storing energy in the form of heat. Sand batteries work by converting renewable energy such as wind or solar power into heat, which is then stored in the sand.

Developed by Finnish researchers Markku Ylonen and Tommi Eronen, these low-cost and low-impact batteries have the potential to revolutionize the way we produce, store, and use energy.

This stored heat can then be used weeks or even months later to distribute heat through district heating systems. A sand battery can also generate electricity when needed by using the heat to drive a turbine but this is not as efficient.

How do Sand Batteries Work?

The process works by using renewable energy to heat coil elements inside steel containers filled with hundreds of tons of sand to temperatures of up to 1000°C. The heat generated is stored in the sand until it’s needed.

Polar Night Energy Sand Battery
Polar Night Energy’s Sand Battery

Benefits of Using Sand Batteries

  • Sand batteries can store low-cost excess renewable energy
  • Sand batteries can store excess heat from industrial processes
  • Stored heat can be held in the sand for weeks or even months
  • The materials to build a sand battery are abundant and low-cost.
    • Sand is abundant and low cost
    • The metal containers and heating elements and pipes are easily manufactured.
    • The cost to construct is relatively inexpensive.
  • Sand batteries have a decades-long lifespan
  • Sand batteries require little to no maintenance
  • The environmental impact of acquiring sand is low compared to Lithium and rare earth minerals required for traditional batteries.
  • Heat transferred to a district heat system is 95% efficient.

Sand batteries are an innovative way to store renewable energy and provide balance to national grids.

They offer a number of advantages over other types of energy storage.

The most important benefit is their ability to store heat for extended periods of time, even in temperatures as high as 1000°C. Compared to water, which can only reach up to 100°C sand allows us to go hotter and store thermal energy for longer.

Another advantage is the price. Sand batteries “charge” low-cost sand with heat generated from relatively inexpensive solar or wind-generated electricity. This makes them an ideal choice for large-scale applications where long-term heat storage and distribution are needed.

The cost to produce a Sand Battery is just the price of the steel for the container, valves, pipes, heating elements, and insulation materials. So this type of energy storage is competitive with most other ‘batteries’.

Sand batteries are 95% efficient if the heat is discharged into a district heat system. If the heat from a sand battery is used to drive a turbine to produce electricity on demand then a lot of the heat is lost during this process. This makes the sand battery an inefficient storage medium for electricity.

What is District heating?

District heating (also known as heat networks or teleheating) is a system for distributing heat generated in a centralized location through a system of insulated pipes for residential and commercial heating requirements such as space heating and water heating. The heat is often obtained from a cogeneration plant burning fossil fuels or biomass, but heat-only boiler stations, geothermal heating, heat pumps and central solar heating are also used, as well as heat waste from factories and nuclear power electricity generation

https://en.wikipedia.org/wiki/District_heating

District heating is better for the environment because it allows for economies of scale as the district has one source of heat instead of each building generating its own heat with a boiler. District heating can use otherwise wasted heat from factories and industrial processes thereby saving energy and reducing the need for electricity and coal or natural gas. And as mentione already in this article, district heating and a storage medium like a sand battery can store excess renewable energy for later use.

Sand Battery Technology

Are Sand Batteries already in use?

Sand batteries are in use in Finland and offer an efficient, low-cost solution for storing renewable energy, making them an ideal choice for any jurisdiction looking to increase their use of green energy sources and comply with climate goals.

Polar Night Energy’s sand battery is already being used in a steel silo at the Vatajankoski power plant on the outskirts of Kankaanpaa, Finland.

It’s just one example of how this technology can be used to help reduce reliance on topping up national grids by burning coal or natural gas.

Challenges in the Use of Sand Batteries

Sand batteries are not very efficient if used to generate electricity. Because the energy is in the form of heat (thermal energy) and is not stored as electricity (like in a lithium-ion battery), the heat has to be converted into electricity by generating steam to run a turbine.

There is a significant amount of heat loss during this process which makes using Sand Batteries as a source of electricity a poor choice. They are approximately 20% energy efficient at providing electricity to the grid.

Providing heat directly to a district heat system, on the other hand, is 95% energy efficient.

This unfortunately means that Sand Batteries are only a viable option in cities that utilize a district heating system.

Fortunately, there are a lot of cities around the world that already use district heating. In the United States alone there are 480 cities that have district heating in place. District Heating is common place in the UK and Europe as well.

Comparing Costs with Other Technologies

Sand batteries are a cost-effective and low-impact energy storage technology that has the potential to reduce our carbon footprint when it comes to heating requirements.

Compared to other advanced battery technologies such as lithium-ion, cobalt, and nickel batteries, sand batteries offer a much more affordable option. In addition, they are much less technically complicated and can be implemented with the same efficiency and cost-effectiveness as hydroelectric systems.

Sand is abundant and cheap. Silica sand costs between $30 – $50 per ton and has a limited environmental impact in extraction and disposal. Sand is less energy dense than lithium-ion batteries but is dramatically less expensive. In applications like transportation where size and weight is a major factor sand is not feasible. But for thermal energy storage for district heating sand is a well suited medium of storage.

Future Potential Uses of Sand Batteries

Because they are an inexpensive alternative to traditional energy storage technologies like lithium-ion batteries, they have the potential to store large amounts of thermal energy for months at a time.

Because Sand Batteries are more efficient when attached to a district heating system it only makes sense to utilize a Sand Battery in cities that have a district heating system in place.

In Helsinki, Finland, 30% of the power from the electric grid goes to heating homes and other buildings. So by implementing Sand Batteries in conjunction with existing district heating systems they can save 30% of the electricity load by pumping heat directly into the district heat system.

If Sand Batteries are implemented globally in all communities with a district heating system it would significantly reduce our reliance on fossil fuels and help achieve climate mandates. It would also help reduce the number of illnesses caused by air pollution in cities that burn fossil fuels to generate heat.

This new technology is currently being tested by the National Renewable Energy Laboratory (NREL).

The National Renewable Energy Laboratory (NREL) in the US specializes in the research and development of renewable energy, energy efficiency, energy systems integration, and sustainable transportation.[2] NREL is a federally funded research and development center sponsored by the Department of Energy and operated by the Alliance for Sustainable Energy, a joint venture between MRIGlobal and Battelle.[3] Located in Golden, Colorado, NREL is home to the National Center for Photovoltaics, the National Bioenergy Center, and the National Wind Technology Center.

https://en.wikipedia.org/wiki/National_Renewable_Energy_Laboratory

The NREL has optioned a Modular, Cost-Effective, Build-Anywhere Particle Thermal Energy Storage Technology that utilizes sand in a closed system designed to generate heat when excess and inexpensive renewable energy is available. And to discharge the heat back into electricity when demand is high but renewable sources are not available.

The ENDURING Mechanism: Storable, Electrically Heated Sand Delivers On-Demand Electricity

This is a different take on the traditional sand battery that can be used to generate electricity on demand instead of feeding thermal energy (heat) into a district heating system.

Bottom line – there are lot of smart people and innovative companies working on some viable solutions to climate change and other problems that we have to deal with.

The Future looks bright – and carbon free.

The potential of sand batteries as an energy storage solution is quickly becoming clear. Sand batteries are capable of storing excess renewable energy such as wind or solar power for long periods of time.

Sand batteries are a promising new form of thermal energy storage that can provide large-scale, low-cost, and sustainable heating and power. By using heat generated from clean, renewable sources, sand batteries can balance energy demands and reduce reliance on topping up electricity supplies by burning coal or natural gas. This technology has the potential to help us live cleaner, healthier lives.

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