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Energy from renewables is one of the biggest challenges faci

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Preet Gujral

on 7 April 2014

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Transcript of Energy from renewables is one of the biggest challenges faci

Organic Quinone Flow Battery
The most advanced commercial flow batteries rely on vanadium ions. A handful of vanadium flow batteries are in operation around the world, and last year in Japan, the Hokkaido Electric Power Company ordered the world's largest vanadium flow battery. The battery should be ready in 2015. The most advanced flow battery uses vanadium, an expensive metal; the team at Harvard, led by senior author Michael Aziz, eliminated metals entirely from their version of a flow battery.

--Energy from renewable resources is one of the biggest challenges facing our society. Despite the advances in technology for forecasting weather, there are still times when solar or wind output do not match demand.
--Storing enough energy to supply needs on calm or cloudy days cost too much using today's batteries. A discovery by a team at the Harvard School promises new progress in cutting our link to coal and oil.
Power harvested from the Sun and wind is pouring into electricity grids. That makes it ever more important to find an efficient and convenient way to store renewable energy for those times when the breeze dies or the skies cloud over.
The team used a quinone known as 9,10-anthraquinone-2, 7-disulfonic acid or AQDS. Using cheap carbon electrodes rather than vanadium, they created a flow battery that matches the performance of existing vanadium flow batteries. Michael Aziz’s battery’s anode uses a solution of sulphuric acid containing the organic compound, quinone. The quinone is cheap and needs no catalyst to react with protons to form a higher-energy hydroquinone, which causes it to charge the battery. Aziz paired this half of the flow battery with a cathode that alternates between bromine and hydrobromic acid. The big advantage of flow batteries is that the chemicals can be stored in tanks outside the battery assembly. Increasing capacity is simply a matter of building larger tanks, making flow batteries particularly suitable for large-scale energy storage.
Flow batteries, which date back more than three decades, replace the solid electrodes of standard batteries with two liquid electrolytes. The liquids, contained in separated tanks, flow through a cell stack, letting ions and electrons move through a membrane in order to discharge and recharge the battery. They are considered good candidates for large-scale renewable energy storage because you can scale up the tank size of a flow battery in order to increase the megawatt-hours of storage available without being forced to also scale up the power capacity; with more traditional batteries like lithium-ion, the components come as a package deal, meaning to achieve 50 megawatt-hours of energy storage you also need to pay for 50 megawatts capacity.
The quinone–hydroquinone reaction is about 1,000 times faster than its rival, the vanadium reaction. This allows the battery to charge and discharge rapidly. This new flow battery has completed 100 charge–discharge cycles with no sign of degradation. Cycling of this quinone–bromide flow battery showed 99 per cent storage capacity retention per cycle. However, this system has a disadvantage. Bromine and hydrobromic acid are corrosive, and could cause serious pollution if they are leaked. To solve this problem, Aziz and his team are working on replacing the bromine with a different quinone.
Impacts on our Society
The creation of this organic flow battery impacts society in various ways. This technology could provide useful backup for off-grid rooftop solar panels. This is a significant advantage since about 20 percent of the world’s population does not have access to a power distribution network. The quinone flow battery could play a huge role in transition of fossil fuels to storage of renewable electricity at very low costs. As well, there is a backup for when the sun or wind cannot be a source of power.
This organic quinone flow battery can store one-kilowatt hour of energy in chemicals costing $27 while other metal batteries cost $700 to store one-kilowatt hour of energy. Therefore the quinone flow battery ensures nearly a 97% saving. Not only energy companies, but also industries are interested in the organic flow battery. They want to lower their electricity bills by buying cheaper power at night and using it for manufacturing during the day.
The group at Harvard University has created an aqueous flow battery that uses a quinone, a type of organic molecule similar to the chemicals used by plants and animals to store energy in biological systems.
The quinones remain dissolved in water, which reduces the flammability risk. Quinones are abundant in crude oil as well as in green plants. Over the past few decades, researchers have investigated many other chemical systems, and ruled all but a handful out. All the elements from the periodic table were ruled out. Therefore, the researches decided to introduce the world of organic chemistry as a solution.
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