Making Sense of Energy Storage

(3BL Media/Justmeans) - There’s no question that a wave of renewable power generation is sweeping this country, and just about every other country around the world. But there are a number of questions surrounding it. Will there be enough power to meet our needs? Can we afford to eliminate nuclear power? How can a transient power source take the place of steady “baseline” power that is being served today be conventional sources? At the center of all these questions lies the promise of energy storage. Storage can certainly transform the erratic contributions of wind and solar into an unflagging, continuous stream. But what kind of storage should we use? How much do we need? And perhaps most commonly, how much will it cost and how long will it take?

The storage question is certainly a dynamic one, as new analyses and new technologies become available. There are, and will likely continue to be differences of opinion about a lot of this, in part because of lot of it depends on things that are still unknown.

That being said, let’s see if make some sense of things. It’s kind of like a really messy room. We may not be able to fully clean it up right now. But if we can at least start putting things into piles, it will start to look less messy.

First question, how badly do we need storage?

It depends who you listen to. If you rely on simple calculations, it would seem that storage is a given if you’re going to rely on renewables for a significant portion of your power. But proponents of an updated 21st century smart electric grid say, not so fast. The wind is always blowing somewhere. If we connected wind farms across vast geographical areas, and factor in the fact that solar is peaking during peak air conditioning demand periods, perhaps we might be able to emulate a steady power source a lot more closely than you’d think, letting sophisticated computers algorithms do the juggling. One very detailed joint study by the University of Colorado and NOAA, found that up to 80% of CO2 emissions could be provided without storage, which could be available in as little as 15 years. The key behind it is a nationally connected grid. Given the level of cooperation and cost required to build this, the biggest obstacles might not be technical. However, with such as grid in place the need for both storage and fossil fuels would be relatively small.

In the meantime, people are pursuing countless varieties of both, as well as continuing to develop new, ever-more-efficient forms of renewable power. The DOE’s energy storage exchange is an excellent resource that showcases close to 1600 energy storage projects around the world. There you will find them sorted into piles including: electro-mechanical, electro-chemical, hydrogen, pumped hydro, and thermal energy storage.

The electrochemical category consists primarily of various forms of batteries. The largest of these are the AES Alamitos Energy Storage Array in Long Beach, California and the recently announced Solar Energy Corporation of India (SECI) in Andra Pradesh, both of which are rated for 100 MW.

In the electromechanical category you will find primarily flywheels and compressed air storage systems. The largest of these are the EFDA Jet Fusion Flywheel, in Abingdon, England, which is rated at 400 MW. And in Germany, the Max Planck Institute’s ASDEX-Upgrade Pulsed Power Supply System, which provides 387 MW of storage. Both systems are flywheels. Not far behind, however is the 330MW Galectric Compressed Air Energy Storage (CAES) system in Larne, in Northern Ireland.

Hydrogen systems tend to be smaller. The German Energiepark Mainz can supply 4 MW of storage. Produced hydrogen is injected into the natural gas grid.

Pumped storage is the oldest and largest utility scale storage system. It requires site with a sunbstantial elevation change. Water is pumped uphill when excess power is available, and then released downhill to run through a turbine when additional power is needed. The proposed Revelstoke Hydro Battery in British Columbia will store up to 4,000 MW of power. Meanwhile the Bath County Pumped Storage Station has been pumping water to store up to 3,003 MW in Virginia since 1985.

Finally, there are the thermal storage systems, which are primarily concentrating solar power plants that store the heated fluid to be used at a later time. The largest are the Pedro de Valdivia CSP Solar Plant with a capacity upon completion of 360 MW, and the 280 MW Solana Solar plant in Gila, Arizona..

Most of these are what is called “in front of the meter systems.” These are used by utilities to stabilize the grid and reduce fluctuations. “Behind the meter” systems, like those being by built by Tesla are used within a residential or commercial environment are starting to grow in popularity as well. Most of these are used in conjunction with solar, though some commercial systems are used for load shifting, meaning they buy the power at night, when it’s cheaper, to use the following day.

Other characteristics, such as the amount of “burst power” each can provide to respond to sudden spikes determines how they will be utilized. For example, flywheels systems like the EFDA Jet Fusion flywheel, can provide 400 MW, but that can only be sustained for 30 seconds. These can be very useful to avoid blackouts. Other systems like pumped storage are designed to produce a steady level of power for a longer period of time.

The battery market is estimated to reach a cumulative 2.5 GW by 2020. Utilities are investing heavily because it helps them integrate renewables into their grid. All this activity is driven by several factors, not least of which are state incentive programs. California’s Public Utilities Commission has mandated 1.325 GW by 2024. Oregon has a more modest goal of 5MWh by 2020. The Massachusetts legislature has just passed an energy storage target bill that is expected to require 3-400MW of storage capacity by 2020.

Image credit: Denis Moynihan: Flickr Creative Commons