In a previous blog post, we introduced how batteries can supplement solar and wind energy to provide power even when the sun isn’t shining, or the wind isn’t blowing. There are several types of batteries available; in this blog, we will delve into some of the different options for both small-scale and large-scale battery systems.
Lead-acid batteries have been the standard for energy storage for decades. These are batteries used in cars, boats, golf carts, etc. If you string together multiple lead-acid batteries, you can obtain enough energy storage to power your home. The advantages for lead-acid batteries is that they are relatively low-cost (around 18 watt-hours/dollar) and are easily obtainable. The drawbacks are that you need many batteries to power a home, can only be discharged to 50%, and they only last around 300 cycles (one charge and discharge equals one cycle) before needing replacement.
Lithium-ion batteries have burst on the market in the last decade, powering laptops, cell phones, cameras, and electric tools. Electric car manufacturers started using lithium-ion batteries for their cars and battery manufacturers adapted them to use for home and business use. Utilities have also started using Li-Ion batteries to store large amounts of electricity to increase the profitability of solar and wind power plants, or as back-up power in-case of power disruptions, like California has done. The advantages to Li-Ion batteries are that they have a high energy density, last around 800 cycles, and can be discharged to 90%. The cons are the price (around 2 watt-hours/dollar) and Li-Ion batteries have a risk of overheating, exploding, or catching fire.
Pumped hydro storage is an energy storage system that utilities use to meet peak electric demands. When electric demand is low, or intermittent energy production, such as solar or wind, is high, water is pumped from a lower reservoir to a reservoir at a higher elevation. Later, when additional power is needed, the water flows down to the lower reservoir through a turbine, generating electricity. Although pumped hydro plants use more electricity than they produce, they produce energy at the time it is most needed and electric prices are higher, making them profitable.
Thermal energy storage, most recently molten-salt energy storage, is another utility-scale energy storage system. In this process, materials are heated to super-high temperatures when power is low or intermittent energy production is high, much like pumped hydro storage, and the super-heated materials are then used to heat water into steam and turn a turbine when electric demand is higher. A common trend is to have concentrated solar panels, using mirrors focused on a single point, heating the material.