Energy Storage: The More the Better

by James Kruszynski

 

Last year, globally averaged CO2 levels reached 400 parts per million[1] a level not seen in over four million years[2]. As we inch closer to the precipice, governments around the world are searching for ways to reduce their carbon dioxide emissions leading to explosive growth[3] in renewable sources of energy. One of the major challenges of integrating renewable energy into existing electric grids however, is that they are inherently intermittent. There the sun does not always shine. The wind does not always blow. This intermittency along with the additional voltage stresses existing grids, grids not designed for this sort of intermittent power, threatening their stability. The two areas where energy storage where energy storage has the most impact are at opposite ends of the spectrum: locations unable to connect to a larger grid and the very heart of national grids where congestion is high.

Areas that are unable to connect to a larger national (or international) grid are particularly at risk of grid instability as renewable energy becomes a larger share of the energy mix. Due to their intermittency, renewables need to be balanced with other energy sources. These sources can take the form of other renewables, fossil fuel generation, or energy storage. Increasing concerns around climate change forces us to consider the options that are not fossil fuel dependent, leaving us two options: more renewables or energy storage. The International Renewable Energy Agency reports that a wide geographic spacing[4] of renewable sources evens out fluctuations in input. Even when the wind is not blowing in New York, the sun is still probably shining in Florida. Connect more and more far flung locations and you have reasonably smooth power input. Unfortunately for remote locations and small island nations, this kind of wide spacing and high levels of interconnection are impossible, leaving only one option: energy storage.

Hawaii is a great example of this fact. With second highest level of solar energy generation per capita[5] in the USA covering a series of relatively small unconnected islands, Hawaii is struggling to integrate further solar energy. A series of unconnected micro-grids designed for the electric system of the mid-20th century[6], Hawaii’s grid is receiving too much energy from rooftop solar panels during off peak hours leading to instability. Small scale energy storage devices at customer homes or larger grid scale storage owned by Hawaiian Electric Industries would greatly smooth power fluctuations and improve grid performance.

At the other end of the spectrum is the heart (or lungs) of large national grids. Imagine doing some strenuous activity, stressing your body. As you stress your system, you start breathing harder and harder until you’re “out of breath”. You just can’t seem to get air in and out of your lungs fast enough. Something similar is happening to electric systems on the global scale. Loads are growing in cities as populations are growing and energy usage is increasing. Cities are demanding that more and more electricity flow into them stressing the electric system. On the other hand, as renewables are added to the energy mix, electricity is also increasingly needing to flow out of cities further stressing the system. Where high voltage transmission lines are insufficient, we are seeing increased electricity congestion[7] and grid instability.

This is where energy storage can swoop in and save the day. Building new transmission lines and upgrading other aging infrastructure is expensive, so expensive that it can make sense to invest in energy storage near load centers. Batteries can store excess renewable energy generated off peak on site and discharge as needed on peak. This reduces the need for high electricity flow in and out of an area, delaying the need for increased transmission lines. There are other financial benefits to costumers and utilities as well. By reducing on peak demand, batteries allow power generators to reduce their use of “peaking plants”. These are usually natural gas or diesel generators and are typically the most inefficient generating option for utilities (which is part of why they are saved for last). This saves on fuel and maintenance for utilities. At the same time, since batteries are charged off peak, the electricity they are buying is cheaper[8] and can therefore be sold to customers at a lower price.

At the end of the day it is clear that there is enormous potential for energy storage, both in remote locations unconnected to a national grid and also at city centers in the hearts of national grids. There are a number of energy storage options blossoming in the market such as Tesla’s Powerwall, Panasonic’s home battery system, and LG Chem among others.

Do you have experience with home batteries or other energy storage devices? How much should utilities invest in energy storage compared to new transmission lines? Share your thoughts and experience by leaving a comment below.

[1] World Meteorological Organization. (2016, October 24). Globally Averaged CO2 Levels Reach 400 parts per million in 2015. Retrieved from http://public.wmo.int/en/media/press-release/globally-averaged-co2-levels-reach-400-parts-million-2015

[2] South Pole is the last place on Earth to pass a global warming milestone. (2016, June 15). Retrieved from National Oceanic and Atmospheric Administration: http://research.noaa.gov/News/NewsArchive/LatestNews/TabId/684/ArtMID/1768/ArticleID/11760/South-Pole-is-the-last-place-on-Earth-to-pass-a-global-warming-milestone.aspx

[3] World Energy Council. (n.d.). Retrieved 11 10, 2016, from New report on variable renewables: Answers to the integration challenge: https://www.worldenergy.org/news-and-media/press-releases/answers-to-the-variable-renewables-integration-challenge/

[4] Roesch, R. (2013). Planning for Island Grids with a High Share of Renewable Power. International Renewable Energy Agency. Retrieved from http://www.irena.org/DocumentDownloads/events/2013/June/03%20WWEA%20Havanna%20Grid%20Stability%2020130603.pdf

[5] Top 10 Solar States. (2016). Retrieved 11 10, 2016, from Solar Energy industries Association: http://www.seia.org/research-resources/top-10-solar-states

[6] Hawaiian Electric Industries. (n.d.). Retrieved from Wikipedia: https://en.wikipedia.org/wiki/Hawaiian_Electric_Industries#History

[7] Power Grid Congestion. (n.d.). Retrieved 11 10, 2016, from Electricity Today: http://www.electricity-today.com/overhead-td/power-grid-congestion

[8] Sioshansi, R., Denholm, P., Jenkin, T., & Weiss, J. (2009, March). Estimating the value of electricity storage in PJM: Arbitrage and some welfare effects. Elsevier Ltd. Retrieved from Science Direct: http://www.sciencedirect.com/science/article/pii/S0140988308001631

 

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