New solar battery technology offers household power at 2.5c per kWh
By Jeff Salton
September 2, 2009
As part of man's ongoing quest to extract the greatest benefits from solar power, Salt Lake City-based company Ceramatec, the R&D; arm of CoorsTek, has made what it believes to be a massive breakthrough in batteries for storing energy harnessed from the sun. The company is making impressive inroads on the prototype of a deep storage battery, the size of a small refrigerator, that safely operates at room temperature, consists of everyday materials, and can output household power at 2.5c per kWh. What’s more, Ceramatec says it will be cheap to purchase.
As solar energy capture gets better and cheaper, safety has remained an issue when discussing battery storage. Currently, great performing energy-dense batteries are nothing more than man-made volcanoes - huge containers of super-hot molten sodium that hover around 600°C. At that temperature the material is highly conductive of electricity, however, it is also toxic and corrosive. Would you want one in your basement?
Instead, Ceramatec's battery comprises a large piece of solid sodium metal mated to a sulfur compound by a paper-thin ceramic membrane. The membrane conducts ions - electrically-charged particles - back and forth to generate a current. The company calculates that the battery will be able to sustain 20-40kWh of energy into a refrigerator-size housing that operates at around or below 90°C. This is possibly the only way that this type of dense battery technology will ever be approved for household use – safe, small (relatively) and cheap to purchase.
Ceramatec says its new generation of battery would deliver a continuous flow of 5kW of electricity over four hours. If that doesn’t power your whole house it will certainly supplement it. And these batteries are expected to withstand daily discharge/recharge cycles over 10 years (3,650 times). The batteries would hopefully sell for around USD$2,000, which is less than 3c per kWh over the battery's life. Conventional power from the grid typically costs around 8c per kWh – and continues to rise.
Presently, most deep cycle batteries don’t have a lifespan anywhere near that long. Daily usage usually results in a permanently dead battery in around 12 months.
It’s no wonder that, as America’s electricity grid, and other electrical infrastructure around the world, nears breaking point, the ability for households to generate, store and time-shift their own power has governments and corporations taking a keen interest in developments.
Ceramatec had its roots in battery technology in the 1980s when it pioneered the development of sodium beta-alumina for Na/S batteries for Ford. This is a technology that has re-emerged in the past few years through Japanese company NGK. But since then Ceramtec has been conducting almost no battery R&D.; “Virtually all of the R&D; effort over the past ten years in the U.S. has been focused on Li-ion batteries for traction applications,” Grover Coors, the principle scientist for battery development and one of the owners of Ceramatec, told Gizmag.
He said interest in engineering solutions for photovoltaics (PVs) in the U.S. has only really spiked in the past two to three years as PV manufacturers and utilities began to realize that they could not dispatch an arbitrary amount of power in real time from solar panels and wind farms without the ability to ‘time-shift’.
“We have been working on several sodium-based batteries for primary applications (non-rechargeable), but the deep-cycle secondary battery is relatively new,” Coors said.
“Since then Ceramatec has been focusing on a different ceramic sodium-ion conductor called NaSICON, which has unique properties that make it possible to construct a low cost, room temperature sodium battery.”
He stated that Ceramatec does not yet have working prototype, but the battery is currently in early stage R&D; and the first prototype will be tested over the next couple of years.
Coors said Ceramatec’s invention won’t replace the ailing electricity grid altogether, but it will be able to supplement it substantially.
“All of the best scenarios involve some sort of grid-connected distributed power. Imagine 100,000 20kWh electrical energy storage (EES) systems sprinkled around Los Angeles. The ‘smart grid’ technologies make this possible, but again, without some form of reliable, distributed storage to time-shift PV to later in the day, PV by itself cannot usher in the necessary paradigm shift.”
At the heart …
What makes the Ceramatec battery plausible for domestic applications is the material at its heart, NaSICON, which stands for Na (Sodium) Super Ionic Conductor. Coors says: “it is a dense, sintered ceramic material with 100 percent selectivity to sodium-ion transport. If you are familiar with solid oxide fuel cell (SOFC) technology, it is the analog to zirconia oxygen ion conductors, except it has the conductivity at room temperature that zirconia has at about 600°C. Ceramatec now has a great deal of experience making this material in large quantities for a number of other applications where sodium ion transport is useful.
For those not familiar with SOFC technology, these are ceramic devices that operate on hydrocarbon fuels (as opposed to hydrogen) like natural gas and coal gas. The operating temperature is high, about 800°C. Coors says design for safety is the company’s highest priority. He believes his batteries are safe to keep at home. “However, my view is that public and private utilities will own and maintain storage assets. Efficient deployment of distributed storage requires that utilities always know what the state of charge on each batteries is, and then have the ability to dispatch power to the grid remotely as necessary. This is one of the concepts behind the smart grid. This is by no means a universally-held view. However, off-grid and grid-parallel scenarios generally don't make economic sense in urban settings.”
When Coors was asked why not ‘skip the middle man’ and have the storage in the solar panels that sit on the roofs, he said: “PV cells have a form factor that favors large, flat areas. This form factor is difficult to optimize with batteries. The battery we are building will be shaped like a small refrigerator. Also, as I explained above, the best deployment strategy, in my opinion, is on the utility side of the meter. Generally, solar panels will be owned by the homeowner and connected on the other side of the meter. So it doesn't make sense to co-locate PV and storage. In the event that storage could be made so inexpensive that the cost of ownership were to favor the homeowner, then this could turn out differently than I envision at this time.”
Coors says Ceramatec is aiming to create batteries that can last 15-20 years. “Unlike lead acid, NiCad, and other battery variants, our battery uses common, low cost materials and contains nothing that will require unusual disposal practices. There will be some components, such as sodium metal and nickel that may warrant recovery for commercial, not environmental, reasons.”
While Coors was excited about the publicity Ceramatec had generated with its announcement, the finer points of the discovery are still shrouded in secrecy.
“There is nothing in the public domain other than some patents and what can be gleaned from our website. Our work is highly proprietary and has been conducted in ultimate stealth,” he says.
Coors believes in the past energy storage has been too expensive to offer a reasonable return on investment. “The long pole of this tent is cost per kWh. In general, storage is expensive and adds to what is called the ‘levelized cost of ownership’ (LCOE). The battery we are constructing will be able to dispatch 40,000kWh per kilowatt, which means the cost of storage over the life of the battery will be 2.5c per kWh. Most battery developers for the EES market either don't understand this metric or have chosen to disregard it because their batteries are either too expensive to purchase or too expensive to operate.”
Whether the technology will see fridge-size batteries that you own and allow you to time-shift your investment in solar power to when you want or need it, or if the utilities will own the batteries and dish it out in peak times to save their weakening power grids, only time will tell. The major energy providers will likely be watching this battery development closely as purchasing a few hundred thousand batteries might be a lot cheaper than building a new powerplant and the associated infrastructure to goes with it.
But let's not put the cart before the horse. First we need battery storage to achieve the three-pronged objective of safe, small and cheap - something that Ceramatec is hopeful it will be able to provide.