Everywhere you look you see more and more energy being generated by solar and wind. The cost of such renewables technology continues to plummet, and renewables now are giving traditional carbon-based energy sources such as coal a real run for the money.
But even if solar and wind became the lowest cost sources of energy, critics point out that the wind doesn't blow all the time, and unless you're in a polar region in the summer, the sun has a habit of setting each day with darkness not far behind. So how do you generate power when the wind doesn't blow hard and the sun is shining on the other side of the Earth?
The traditional answer is hydropower. Rivers with dams can be relied upon to supply a steady flow of water even in the middle of the night. At the same time, water is often diverted into a holding pond for use as a backup. If extra power is needed, the water in the holding reservoir is released and extra electricity is generated.
But there are only so many dams in the world, and only so many more good sites on which to site such dams. Not only that, but virtually every new major dam project raises huge environmental concerns.
While hydropower may be limited, another technology is emerging as the solution: batteries. Two battery technologies – lithium ion and molten salt – have been under development for some time.
This past week, a potential game-changer battery technology was announced in Nature Energy. It was developed by materials scientists at Stanford University. The Stanford researchers have built a prototype battery using manganese. What makes this particularly interesting is that manganese is a low cost, widely available material.
All batteries have a cathode (positive charge) and an anode (negative charge). In the case of the prototype manganese battery developed at Stanford, the cathode cycles between soluble manganese and solid manganese oxide. The anode cycles between hydrogen gas and water. The latter cycle is already well known and well understood.
The manganese battery works, but it's still just a prototype. What was built in the lab at Stanford is only 3 inches tall and capable of generating a whopping 20 milliwatt hours of electricity. To put that in perspective, that's enough to power an LED light on the end of key ring. So it isn't much of a battery – at least not yet – but certainly very promising when one considers than manganese sulfate is a cheap, abundant industrial salt that is already used to make dry cell batteries, fertilizers, paper and another of other products. When you're talking about a new technology, it's always somewhat reassuring when one hears the words "cheap, abundant, and familiar".
Yi Cui, a professor of materials science at Stanford, and the lead author of the new paper, estimates that, given the water-based battery's expected lifespan, it would cost a penny to store enough electricity to power a 100 watt lightbulb for twelve hours.
So the manganese prototype battery can power a pen light. How much does the technology have to improve for it to be considered as a storage device on the electric grid? The US Department of Energy recommends grid storage batteries should be capable of: 1) discharge at least 20 kilowatts of power over an hour; 2) at least 5,000 recharges ; and 3) have a useful lifespan of 10 years or more. The Stanford battery already has more than met the second criterion, and the researchers feel confident of the third.
Now the challenge is to build a battery that is both powerful and cost-effective. The Department of Energy thinks the proposed 20 kilowatt/hour battery above should cost under $ 2,000, meaning less than $ 100/kilowatt hour. While the key material – manganese sulfate – is inexpensive and widely available, the prototype battery uses platinum as a catalyst to spur the crucial manganese/manganese oxide reaction. The cost of platinum would make a commercial scale manganese battery uneconomic. The Stanford researchers think they've found a catalyst that will get the cost of the battery down below the Department of Energy target.
So just how confident are the Stanford researchers? Well, Yi Cui, the lead researcher, is seeking a patent. He's also formed a company to license the technology from Stanford University and commercialize it.
Assuming the Stanford researchers can commercialize the new battery, then besides hydropower storage, there will then be three different technologies available to store electricity on the grid.
You're likely familiar with lithium ion battery storage. Your computer and mobile phone likely use lithium ion batteries. You also know how expensive those batteries are.
Besides those lithium ion batteries in your computer and mobile phone, you're starting to see them as storage devices for electricity in homes and businesses. Not only that, Tesla has begun building large scale batteries for storage. Perhaps the most famous one is the one Tesla built within 100 days in South Australia. We'll likely see lots more of these installations – and Tesla will likely get the cost reduced significantly over time.
There's another battery storage technology, however, that you've probably not heard about. That's the technology to store solar energy in molten salt, sometimes referred to as concentrated solar power (CSP).
The technology works as follows. A series of mirrors are laid out in concentric circles, each mirror aiming sunlight at a single tower at the center of the innermost circle. The focused energy then heats molten salt in the tower. The molten salt acts as a giant battery. When the energy is needed, it is converted into electricity by a turbine. There are several commercial installations in California and Nevada with more planned.
Molten salt storage could be a great solution, but it only works if you have a lot of land and a lot of capital. It's a commercial/industrial solution of a utility, not a homeowner or small business.
So the manganese battery technology being developed at Stanford could conceivably work in both a small scale/home setting as well as a commercial/industrial setting. In the latter case, it could become a viable alternative to lithium ion technology in the home and small business. In the latter case, it could scale to address industrial-sized requirements.
If all three of these technologies can scale, the key impediment to widespread adoption of renewable energy – the problem of storage – will disappear. People in the coal industry have been worried about new solar and wind technology. What they should really be worried about are the people developing scalable battery technologies that will make widespread solar and wind power a realistic possibility.
