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“The worldwide transition from fossil fuels to renewable sources of energy is under way …” according to the Earth Policy Institute’s new book, The Great Transition.

Between 2006 and 2012, global solar photovoltaic’s (PV) annual capacity grew 190 percent, while wind energy’s annual capacity grew 40 percent, reported the International Renewable Energy Agency. The agency projects that by 2030, solar PV capacity will be nine times what it was in 2013; wind power could increase five-fold.

Tesla’s utility scale Powerpack batteries.
Tesla’s utility scale Powerpack batteries.

Electric vehicle (EV) sales have risen 128 percent since 2012, though they made up less than 1 percent of total U.S. vehicle sales in 2014. Although today’s most affordable EVs still travel less than 100 miles on a full battery charge (the Tesla Model S 70D, priced starting at $75,000, has a 240-mile range), the plug-in market is projected to grow between 14.7 and 18.6 percent annually through 2024.

Ford C-Max Energi and Honda Fit EV at a public charging station in front of San Francisco City Hall.
Ford C-Max Energi and Honda Fit EV at a public charging station in front of San Francisco City Hall.

The upward trend for renewables is being driven by concerns about climate change and energy security, decreasing solar PV and wind prices, rising retail electricity prices, favorable governmental incentives for renewable energy, the desire for energy self-sufficiency and the declining cost of batteries. Growing EV sales, also benefitting from incentives, are affecting economies of scale in battery manufacturing, helping to drive down prices.

Sun and wind energy are free, but because they are not constant sources of power, renewable energy is considered “variable”—it is affected by location, weather and time of day. Utilities need to deliver reliable and steady energy by balancing supply and demand. While today they can usually handle the fluctuations that solar and wind power present to the grid by adjusting their operations, as the amount of energy supplied by renewables grows, better battery storage is crucial.

Solar plant in the Mojave. Photo credit: Akradecki
Solar plant in the Mojave. Photo credit: Akradecki

Batteries convert electricity into chemical potential energy for storage and back into electrical energy as needed. They can perform different functions at various points along the electric grid. At the site of solar PV or wind turbines, batteries can smooth out the variability of flow and store excess energy when demand is low to release it when demand is high. Currently, fluctuations are handled by drawing power from natural gas, nuclear or coal-fired power plants; but whereas fossil-fuel plants can take many hours to ramp up, batteries respond quickly and when used to replace fossil-fuel power plants, they cut CO2 emissions. Batteries can store output from renewables when it exceeds a local substation’s capacity and release the power when the flow is less or store energy when prices are low so it can be sold back to the grid when prices rise. For households, batteries can store energy for use anytime and provide back-up power in case of blackouts.

Batteries have not been fully integrated into the mainstream power system because of performance and safety issues, regulatory barriers, the resistance of utilities and cost. But researchers around the world are working on developing better and cheaper batteries.

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