The Sun is an infinite source of energy. However, in order to fully harness its power, we must find a way to store solar energy to use even when the sun isnt shining. Without storage, some generation by solar may be taken offline to avoid over-generation, essentially throwing away valuable energy. With storage, this energy can be collected and utilized on cloudy days, at night, or in the event of an electrical disruption, when solar production is low. How do we store this valuable energy? Some rely on batteries, but mechanical storage's popularity is rising as it has begun to be recognized as a more sustainable option.

Currently, the most popular way to store energy produced by solar power plants is in batteries, which store chemical energy and convert it into electrical energy. Though popular, batteries come with their drawbacks, as they can sometimes produce unsustainable byproducts. For example, the most popular batteries used to store excess solar energy today are lithium ion batteries, which require environmentally strenuous mining operations in order to source sufficient amounts of lithium.

An alternative way to bank solar energy is with a method called mechanical storage. There are a number of different types of mechanical storage, the three most popular being pumped storage hydropower, compressed air energy storage, and flywheel energy storage.

Pumped storage hydropower harnesses the potential energy of water by utilizing solar energy to pump water from a lower elevation to a higher elevation. The water is stored at this high elevation until energy is needed and it flows down, spinning a turbine to produce power.

Another method, compressed air energy storage, compresses and stores air in an underground cavern when solar production is high. Then, when power is needed, the air is heated and expanded in a turbine to drive power generation.

Flywheel energy storage is a storage method in which a rotor is levitated and spun in a chamber through the use of magnets. In this way, the flywheel is able to spin continuously with the use of very little energy. Energy can then be drawn from the system by using the spinning flywheel as a generator. Currently, the worlds largest flywheel energy storage system is in Stephentown New York, which can harness and eventually release up to 20 megawatts of electricity.

As a nation that is projected to use solar to supply 20% of its energy by the year 2050, it is becoming increasingly important to find sustainable ways to store the massive amounts of energy required to guarantee reliable energy supplies.