Renewable energy (RE) promises much, but it has yet to make a significant impact on world demand. In 1973, the world’s total primary energy supply (TPES) amounted to 6,101 million tonnes of oil equivalent (Mtoe), of which just 0.1 percent was made up of “other” sources—primarily geothermal, solar, wind, tide/wave/ocean, and heat. Fossil fuels (oil, gas, and coal) made up 86.7 percent. Forty-two years later (2015, the latest year for which figures from the International Energy Agency are available) TPES had more than doubled to 13,647Mtoe, but renewables still made up only 1.5 percent of demand (with fossil fuels making up over 81 percent). The positive spin on these figures is that renewables have risen from 6.1Mtoe to 205Mtoe in a little over four decades, but the slow rise shows there is still much to do.
Political and regulatory hurdles aside, the key technical hurdles for greater adoption of renewables are
Both make it impossible to guarantee RE resources will be available when peak demand occurs.
However, pilot operations have demonstrated that energy storage using Li-ion batteries could provide a solution to RE variability and uncertainty by smoothing the differences between supply and demand. For example, since 2012 the Hawaii Electric Light Company has been relying on two containerized Li-ion battery systems from Saft to smooth wind power variability on the Big Island. The systems store 496kWH, feature a two-hour runtime, and can be charged during lulls in demand from RE sources. These developments point to 2018 as the year this technology takes off on a commercial scale.
Unreliable supply spooks utility managers because of harsh financial penalties if the lights go out. While virtually all utilities understand the merits of green energy, investment in the technology is often accompanied by back-up investment in highly reliable conventional sources. For example, in recent years the U.S. increased conventional reserves by nine percent to back-up its investment in wind power. While the utilities can hardly be blamed for protecting their bottom lines, this conservative approach isn’t going to reduce overwhelming reliance on fossil fuels any time soon.
The solution to the technical challenge is to store any excess energy from RE sources when the sun shines and the wind blows for release when the elements don’t cooperate. The electricity generation industry is well-versed in energy storage to smooth peaks and demands. For example, hydroelectric schemes typically use excess energy at times of low demand to pump water uphill. The potential energy in the upper reservoir is then released exactly when it’s needed.
Some utilities have taken this a step further by teaming wind turbines with hydroelectric schemes. The wind turbines fill the upper reservoir whenever there’s a breeze, enabling energy storage even if all the main plant’s electricity is being used to meet consumer demand. The technology is popular: Oak Ridge National Laboratory research revealed that in 2014, 97 percent of utility-scale storage was in the form of pumped water.
The disadvantage of hydroelectric schemes is that they rely on favorable topology, and suitable sites—especially those close to population centers—which are thin on the ground. And even if a site is identified, there’s no guarantee that construction on what is often a sensitive site will be given the go ahead.
Batteries are purpose-designed for electricity storage and overcome the geographical restrictions of hydroelectric installations because they can be placed virtually anywhere.
While other battery technologies exist, few can compete with Li-ion technology’s energy density, number of recharge cycles, and reliability. In addition, continuity of supply and a robust distribution chain are assured, in part due to Li-ion technology’s widespread adoption in consumer electronics products and electric vehicles (EVs). Such advantages have seen Li-ion technology adopted for pilot energy storage schemes; the Hawaiian example is just one of many pilot plants around the world. Smart grid technologies are easing the on and off switching of stored energy by making it simpler and more efficient.
According to Scientific American, Li-ion storage technology is set to expand from pilot plants after 2018 because solar and wind power are becoming more abundant and cheaper—accelerating the shutdown of older coal- and gas-fired power plants that can no longer compete. Because this transitional period is haphazard, Li-ion storage is filling the inevitable gaps in generation capacity that occur.
A perfect case study is South Australia (SA). The region turns to wind power for around 40 percent of its power generation, but the rush to RE has been made at the expense of reliability. Now that old coal-fired power stations have been removed from the generational mix, the Australian state suffers widespread power outages when the weather calms. EV maker Tesla has offered a solution in the shape of the world’s largest Li-ion battery—situated in Jamestown and to be employed when SA’s wind turbines can’t cope. The unit is rated at 129MWh, enough to supply 30,000 Australian homes for just over an hour in the event of other sources going offline. Power to charge the batteries comes from the next door Hornsdale Wind Farm.
More ambitious plans are afoot. Scientific American reports that by 2021, a Long Beach gas-fired “peaker” power station—so-called because it comes online in the afternoons to help baseload stations meet peak demand—will be replaced by a 400MWh Li-ion electricity storage system. The installation is big enough to supply nearly 50,000 homes for two hours and will comprise 18,000 modules, each the same size as a Nissan Leaf EV’s power pack. In a novel twist, the battery will be charged by solar energy in the mornings to cater for the afternoon peak and by wind power during the night for the early morning peak.
Although 2018 will see much greater use of Li-ion storage, the technology will take time to become ubiquitous. Recently, Citibank estimated that the cost of power from pumped hydroelectric sources was about five percent of the cost of grid-scale battery-stored electricity. Others say that a shortage of lithium (and cobalt, which is used for Li-ion battery electrodes) will limit future battery supply.
But as additional sources of manufactured Li-ion cells come to exist, prices for the batteries will drop and other market sources will come into play. For example, cheaper RE will push out fossil fuel capacity, encouraging greater investment in storage technology. Long-term material shortages are likely to disappear as Li-ion technology succumbs to battery technologies with greater promise built from less exotic materials and with much higher energy densities.
Steven Keeping gained a BEng (Hons.) degree at Brighton University, U.K., before working in the electronics divisions of Eurotherm and BOC for seven years. He then joined Electronic Production magazine and subsequently spent 13 years in senior editorial and publishing roles on electronics manufacturing, test, and design titles including What’s New in Electronics and Australian Electronics Engineering for Trinity Mirror, CMP and RBI in the U.K. and Australia. In 2006, Steven became a freelance journalist specializing in electronics. He is based in Sydney.
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