By Craig Evans, Renewable Energy Consulting Services, www.renewable-energy.consulting
Three new types of batteries could change the renewable energy world. These include:
- Aquion’s low-cost sodium-ion battery, for which Aquion recently raised $55 million of venture capital funding from investors including Bill Gates and has just finished installing its first commercial-scale production line in a former Sony TV factory near Pittsburgh.
- The inexpensive, high capacity “Organic Battery” recently developed at the Harvard School of Engineering and Applied Sciences; and
- Sugar batteries being developed by Virginia Tech, the Tokyo University of Science and CFD Research Corporation in Huntsville, Alabama.
Energy storage also is poised to get a big push:
- The U.S. Department of Energy (DOE) is actively working to promote grid energy storage; and
- Two bills promoting energy storage are pending in Congress, H.R. 1465 and S. 1030 which offer tax credits for three categories of energy storage facilities.
The need for energy storage in the electric grid is increasing as a result of the growing use of renewable power generation, which varies with wind and solar conditions. The proliferation of electric vehicles and plug-in hybrids also contributes to the growing interest in grid storage, and the need for cheaper, more efficient, more environmentally friendly batteries.
DOE released a report to Congress in December that identifies the benefits of grid energy storage, the challenges that must be addressed to enable broader use, and the efforts of DOE, in conjunction with industry and other government organizations, to meet those challenges.
The challenges are: (1) a limited portfolio of cost competitive energy storage technologies; (2) the lack of processes for evaluating and reporting the performance of existing storage systems on a unified basis; (3) inequities in the regulatory environment, which tend to mute the case for investment in energy storage; and (4) the lack of industry acceptance due to uncertainty about how storage technologies will perform over time.
The new batteries have the potential to not only meet the grid’s energy storage challenge, but to provide business, industry, homeowners and consumers with affordable energy storage options.
Here’s a brief overview of the new battery technologies:
Aquion’s sodium-ion battery: This battery will compete in price with a lead-acid battery—one of the cheapest types of battery available—yet will last more than twice as long. While lead is toxic and the sulfuric-acid electrolyte in lead-acid batteries is potentially dangerous, Aquion’s battery is made of inexpensive materials including manganese oxide and water, which the inventor, Carnegie Mellon professor of materials science and engineering Jay Whittaker, says are safe enough to eat—adding however that they taste terrible.
The battery operates much like a lithium-ion battery, in which lithium ions shuttle between electrodes to create electrical current. But the new battery uses sodium ions instead of lithium ones, which makes it possible to use a salt water electrolyte instead of the more expensive—and flammable—electrolytes used in lithium-ion batteries.
The trade-off is that the batteries store less energy by weight and volume than lithium-ion batteries do, so they’re not practical for cars or portable electronics. But space isn’t an issue for stationary applications, where batteries can be stacked in warehouses or shipping containers.
By providing an affordable way to store solar power for use at night or during cloudy weather, the technology will provide a workable a solution to grid energy storage. It also will allow isolated populations to get electricity from renewable energy.
Harvard’s Organic Flow Battery: Harvard University researchers also have developed a new type of battery that could make it economical to store as much as two or three days of electricity from wind, solar and other intermittent sources of power. The battery is based on an organic molecule—called a quinone—that’s found in plants such as rhubarb and can be cheaply synthesized from crude oil. The molecules could significantly reduce the cost of energy storage materials in a type of battery called a flow battery, which is particularly well suited to storing large amounts of energy.
Flow batteries store energy in liquid form in large tanks. Such batteries have been in use for decades to help manage the power grid. But they’re expensive, about $700 per kilowatt-hour (kWh) of storage capacity. Harvard’s organic flow battery is projected to cost only $27 per kWh, well below the $100 per kWh threshold at which DOE says it becomes economical to store hours of energy from wind and solar farms.
For a homeowner, a day’s worth of energy generated from wind or solar panels could be stored in a flow battery the size of a typical propane or heating oil tank.
The Harvard work is the first time that researchers have demonstrated high-performance flow batteries that use organic molecules instead of metal ions. The technology now faces grueling tests to assess its degradation rate over thousands of cycles (to address DOE’s challenge #4), with early tests indicating no signs of degradation.
Sugar batteries: Virginia Tech’s Prof. Y.H. Percival Zhang is leading research into batteries that run on sugar, which will make them both refillable and biodegradable. The sugar batteries will have a higher energy density and cost less than rechargeable lithium batteries, which lose their ability to hold a charge after a while, and are considered toxic waste once discarded. Researchers at the Tokyo University of Science also are working on sugar batteries.
Zhang envisions users refilling the batteries with sugar when they need refueling, “much like filling a printer cartridge with ink.” He hopes they may be powering electronic devices in as little as three years.
The CFD Research Corporation in Huntsville, Alabama, has developed and patented a novel Bio-Battery that can convert a single packet of sugar into the enery equivalent to that found in a six-pack of AA batteries. CFDRC was awarded a $750,000 contract in September 2013 from the U.S. Air Force to further advance the Bio-Battery by extending the platform to more fuel choices and developing a novel paper-based passive fuel pumping system. The batteries can be recharged using a sugar solution or even a can of soda.
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