The Current State of Energy Storage

Originally published in The Environmental Magazine

As the world begins to derive more and more of its energy from renewable sources, the topic of energy storage will become increasingly important. Though wind and solar are significantly more environmentally friendly than coal, oil, and natural gas, they do not generate energy with the same degree of consistency. The intermittent nature of these greener sources necessitates the creation of technology to hold the energy they generate; technology that allows this energy to be used at times when the sun isn’t shining and the wind isn’t blowing.

At the moment, pumped hydro storage is the most commonly employed technique for storing renewably generated energy. In pumped hydro installations, pumps use excess energy generated by renewable (or nonrenewable) sources to move water from a low point to a higher point. In more technical terms, pumps convert electrical energy into gravitational potential energy. When users demand large amounts of electricity from the grid, operators allow water to fall back down to its starting point and run through turbines in the process. As it does so, turbines convert gravitational potential energy back into electricity.

Pumped hydro plants last for a long time, and have a roundtrip efficiency (https://energymag.net/round-trip-efficiency/) of around 80% (which energy experts consider to be quite good.) The aforementioned positive attributes, coupled with several others, have led to pumped hydro accounting for over 90% of utility scale energy storage technology in the U.S, and a majority of energy storage technology in the world. While this dominance will no doubt continue into the future, we must pursue storage other options for several reasons. One of the most important, is that there are many locations where the topology makes it impossible to create pumped hydro facilities. In much of the midwest for example, there is not enough difference in elevation to create a storage plant that relies on the movement of water. Additionally, pumped hydro plants are very expensive to both construct and maintain.

The second most popular form of energy storage is thermal storage. In this method, technologies use excess energy to heat a substance, such as a salt. The heat stored in this salt is then used to generate electricity when electricity demand is high.

The third most popular energy storage strategy, and also one of the most promising, is lithium ion batteries. When compared to other similar technologies, lithium ion batteries either perform competitively, or are rapidly improving in the following important areas:

1. Calendar Life (The number of years the technology generally lasts)
2. Cycle Life (The number of times the technology can be charged and discharged)
3. Cost (The cost of storing and or releasing a unit of energy)
4. Gravimetric and Volumetric Energy Density (How much energy the technology can store per unit of weight and volume, respectively)
5. Round Trip Efficiency (The percentage of energy transferred into the storage technology that can be discharged back into the grid)
6. Safety

Out of all these metrics, cost is the most important in regards to the future of lithium ion batteries.

At the moment, it is currently cheaper to meet excess grid demand with auxiliary natural gas power plants. However, projections indicate that by 2030, lithium ion batteries will be a more economical technology for filling this role. Analysts primarily base this prediction on the fact that lithium batteries’ price per kilowatt fell 85% from 2010 to 2018.

If you would like to help increase the rate at which the cost of lithium ion energy storage falls and you already have solar panels on your roof, you might want to consider installing a battery storage system such as the Tesla Powerwall. In some states, tax incentives can offset the cost of this installation. California, for example, offers the Self Generation Incentive Program, which encourages homeowners to install clean energy technology.

If you know of any other energy storage systems that you’d like to recommend, or energy related tax incentive programs that you would like to draw attention to, please do so in the comments.

Additional energy storage facts and information:

• If you would like to get a better idea of the world’s currently installed energy storage infrastructure, this map created by the Department of Energy (https://www.energystorageexchange.org/projects) will be very helpful.
• If you would like to learn more about how the price of a technology falls as we produce more of it (a process that is rapidly taking place with lithium ion batteries), check out this Forbes article: https://www.forbes.com/sites/jimhandy/2013/03/25/moores-law-vs-wrights-law/#1d5e45ba77d2
• It likely that we will eventually repurpose the batteries from electric cars for home and industrial energy storage, once they have derated to the point that they are unsuitable for powering a moving vehicle.
• Experts predict that electric cars will eventually be able to help regulate the electrical grid by sending current into it while they are plugged into charging ports.