27-04-2021 | | By Robin Mitchell
Recently, an energy storage solution in Canada has received $3.2m in government funding. What challenges do renewable energies present, the technology being used, and what other technologies exist for energy storage?
95% of scientists agree that the climate is changing, many are worried about the rising sea level, and the Amazon rainforest is being destroyed at an alarming rate. However, even if some disagree that climate change is a cause for concern, or if humans are responsible for the change, it is hard for anyone to deny that the burning of fossil fuels is generally a bad idea.
First, fossil fuels are finite resources, and being dependent on a finite resource means that the dependency must be broken as early as possible otherwise major economic and social issues can arise (i.e. lack of power, broken economy etc.). Secondly, fossil fuels are generally very unpleasant and bad for the environment; oil is carcinogenic, coal is dangerous to breathe in, and the emissions from burning fossil fuels are pretty nasty overall.
The obvious answer to replacing fossil fuels is the use of infinite energy sources (take that with a pinch of salt), such as solar, wind, hydro, and geothermal. These energy sources produce no CO2 when in operation, use readily available energy, and can help to protect the environment. Except for geothermal and hydro, most renewable energy sources are intermittent, meaning they are not always around. The sun doesn’t always shine, the wind doesn’t always blow, and not everywhere has access to a river or geothermal activity.
To complicate the matter, energy consumption varies throughout the day, and renewable energies are often at their lowest output when energy is at its highest demand (before and after the workday). This can be solved if excess energy can be stored throughout the day, but different energy storage technologies have their own advantages and disadvantages. For example, Lithium-ion batteries have large energy densities, but their price and gradual deterioration makes them far from ideal for storing power.
Recently, the Canadian government announced that it would be awarding a storage technology solution $3.2m. Hydrostor has developed an energy storage solution that utilises compressed air, and their test facility has a peak power output of 1.75MW, 2.2MW charge rating, and 15MWh of storage. However, the new facility, which will be funded by the $3.2m, will have a rating of up to 500MW, and the new facility will be based on the previous 1.75MW facility.
The operation behind the storage solution is incredibly trivial; during times of excess energy, the facility compresses air and feeds this compressed air into a water-filled cavern. The water-filled cavern (which is deep underground), is also connected to a ground-level water pool. As air is pumped into the cavern, the water is displaced, and the water level on the pool rises. During the compression of air, the air heats up, and this heat is removed and stored.
When the facility needs to provide power back to the grid, the water displaces the compressed air in the cavern, and this compressed air is then reheated using the previously trapped heat. This increases the energy of the compressed air, and when fed into a turbine, generates electricity.
There are many different energy storage solutions, all with their own advantages and disadvantages. Some of these utilise potential energy of mass in gravitational fields, in other words, moving something heavy high up and then letting it fall back to earth. For example, one design utilises cranes that lift heavy concrete blocks and stack them, and the energy used to stack the concrete is excess energy. When it is time to put energy back into the system, the cranes lower the blocks, and in doing so, generate electricity.
Some energy storage solutions utilise flywheels which store energy in the form of angular momentum. During a charging stage, a wheel is spun up using excess energy. When energy is needed, the wheel is slowed down using a coil (specifically, the flywheel is magnetised, and the spinning of the flywheel in the presence of a coil will generate electricity turn slow the wheel down).