Transcript
As explained in our sister-publication Trends, wind and solar power are limited by the need to generate or store energy for periods when the wind doesn’t blow and the sun doesn’t shine. One alternative is to use natural gas generators during these periods. Other solutions involve using today’s batteries, pumped water and thermal storage. However, natural gas produces CO2, batteries are too expensive, pumped water only works in few locations and thermal is still unproven.
However, a new low-cost, high-performance battery chemistry developed by University of Colorado Boulder researchers could one day lead to scalable grid-level storage for wind and solar energy that could help electrical utilities reduce their dependency on fossil fuels.
The new innovation, described in the journal Joule, outlines two aqueous flow batteries, also known as redox flow batteries, which use chromium and organic binding agents to achieve exceptional voltage and high efficiencies. The components are abundant in nature, offering the promise for cost-effective manufacturing. The materials are low-cost, non-toxic and readily available.
Today’s industry-standard lithium ion technology can provide power for smaller scale applications. However, you would need millions of batteries to backup even a small fossil fuel power plant for an hour. And while the lithium ion chemistry is effective, it’s ill-suited to meet the capacity requirements of an entire wind turbine field or solar panel array.
The basic problem with lithium ion batteries is that they don’t scale very well. The more solid material you add, the more resistance you add and then all of the other components need to increase in tandem. So, in essence, if you want twice the energy, you need to build twice the batteries and that’s just not cost-effective when you’re talking about this many megawatt hours.”
Flow batteries are a more promising avenue. Aqueous batteries keep their active ingredients separated in liquid form in large tanks, allowing the system to distribute energy in a managed fashion, similar to the way a gas tank provides steady fuel combustion to a car’s engine when you push the pedal.
While there are some examples of flow batteries operating consistently for decades, what matters is cost, and that’s what the Colorado team wanted to improve on.
The researchers went back to basics, re-examining flow-battery chemistries that had been studied years ago but abandoned. The key turned out to be combining organic binding agents, or chelates, with chromium ions in order to stabilize a potent electrolyte.
Some people have taken this approach before but hadn’t paid enough attention to the binding agents. The customized chelate known as PDTA creates a “shield” around the chromium electron, preventing water from hampering the reactant and allowing one of the battery cells to disperse 2.13 volts — nearly double the operational average for a conventional flow battery.
PDTA is a derivative of EDTA, an agent already used in some hand soap, food preservatives and municipal water treatments due to its bacteria-stymying properties. EDTA is considered non-toxic. The chemistry also uses a benign form of chromium, the same type used in stainless steel surgical instruments. And, they got the chemistry to work at the relatively neutral pH of 9, unlike other batteries which use highly corrosive acid that’s difficult to work with and difficult to dispose of responsibly.
Even better everything is already available in commercial quantities from existing factories.
The team filed a patent on the innovation, and they plan to continue optimizing their system, including scaling it up in the lab in order to cycle the batteries for even longer periods of time.
|
