Currently only 2.5% of the capacity of the U.S. grid is able to be stored, compared with 10% in Europe and 15% in Japan, which in the event of a grid failure could mean trouble for the U.S. This is why Professor Donald Sadoway at MIT received US $7 million from U.S. Energy Agency ARPA-E), $4 million from French oil company Total and support from the U.S. Defense Agency DARPA.
The goal of Sadoway’s research is to bring the cost of large scale energy storage facilities in line with the cost of natural gas plants. He said that in order to do this, incredibly large liquid metal batteries will need to be built and the facilities will need to be used in much the same way that flywheel storage plants are expected to be used, as frequency regulators that are capable of dispatching energy quickly in the event of an emergency. The basic principle behind the technology is to place three layers of liquid inside a container: Two different metal alloys, and one layer of a salt. The three materials are chosen so that they have different densities that allow them to separate naturally into three distinct layers, with the salt in the middle separating the two metal layers — like novelty drinks with different layers. The energy is stored in the liquid metals that want to react with one another but can do so only by transferring ions — electrically charged atoms of one of the metals — across the electrolyte, which results in the flow of electric current out of the battery. When the battery is being charged, some ions migrate through the insulating salt layer to collect at one of the terminals. Then, when the power is being drained from the battery, those ions migrate back through the salt and collect at the opposite terminal. The whole device is kept at a high temperature, around 700°C, so that the layers remain molten. While each of these technologies has a lot of lab work left before it’s ready for field testing on a large scale, chemistry professor Dr. Dan Nocera and the company he helped found Sun Catalytix are working to commercialize a catalyst that can be used to split water.
The basis of Sun Catalytix’s technology is a cobalt phosphate catalyst that Nocera said is more efficient at splitting water into hydrogen and oxygen than other materials. He said that the catalyst can work within normal ambient temperatures and with water sources as diverse as tap water and water straight out of the Charles River in Boston. While commercial electrolyzers that split water to make hydrogen already exist, Nocera said that they’re far too expensive and require a significant amount of energy to run. Sun Catalytix is in the process of testing an electroylzer that is built with its proprietary catalyst that can be manufactured using PVC plastic. A completed 100-watt system would work like this: solar PV panels would power an electrolyzer, which would then produce hydrogen that would be stored in tanks and then used as fuel for a fuel cell for electricity or to power a hydrogen vehicle. Nocera said that three liters of water a day could power a home. He said the ultimate goal of the Sun Catalytix system is use cheaper solar panels and fuel cells (still a stumbling block) to implement systems like this in the developing world where there is little-to-no electricity generating infrastructure in place and where three liters of even low-quality water per day could dramatically increase the quality of life of the people living there. Development of the technology is being financed by more than $1 million from Polaris Venture Partners. Nocera said that he expects a working prototype to be completed in the next 5-8 years and that the company has already been approached by solar companies interested in having their panels used in the system.
Source: Renewable Energy World
