Energy storage is a tricky subject, and yet immensely valuable in the long term, but only a few scientists are working on the topic in India. One of them is AK Shukla, distinguished professor at the Indian Institute of Science (IISc) in Bangalore. He is now developing a hybrid supercapacitor, a device that can store electrical energy and has some advantages over the lead acid battery. His first exhibit is a small prototype, slightly bigger than a large matchbox, weighing about two kilos. It can hold enough charge to light a lamp for five hours. The market is thirsting for more. The lead acid battery was invented long ago, as far back as the year 1859. It is still going strong, being the primary means of electricity storage in India, and sustains a growing market of Rs 25,000 crore. But it is not good enough for two of the biggest future applications: electric cars and grid storage. For those we need big breakthroughs in electricity storage, and the supercapacitor, hybrid or otherwise, is just one of the options being tried. “We can charge the supercapacitor much faster than the lead acid battery,” says Shukla.Batteries hold energy through a chemical change in a liquid, and this change is reversed while drawing current from it. Capacitors use physics and not chemistry. These store energy by keeping two mutually isolated metal plates with equal but opposite charges, and discharges it when the plates are connected.Supercapacitors also work the same way, except that they hold a tremendous amount of charge. Capacitors charge quickly and discharge quickly, and are used when high power is needed. Batteries charge slowly and discharge slowly, and are used when you need steady supply of energy over long periods. By combining the two, scientists hope to have the best of both worlds, and provide energy as well as power, but it is not so simple in practice. Capacitors themselves are widely being tried as an alternative to battery, but are not good enough at the moment.So, while we wait for the supercapacitor to improve, scientists are looking at other options. The world needs new storage devices because renewable energy requires them. At the moment, solar and wind energies only supplement thermal and hydroelectric power. So it does not matter too much if the sun does not shine or the wind does not blow. But if they are major suppliers of energy, as expected in a decade, we have to store their energy somewhere to use when the source shuts down.Good energy storage is thus necessary for renewable energy to take off in a big way. What we have are the good old lead acid battery and a range of emerging technologies with no clear winners yet. “Demonstrations have started happening now,” says Rahul Walawalkar, executive director of the Indian Storage Alliance. “I expect grid storage to ramp up by 2020.”The supercapacitor would be a good option one day, especially when you need short bursts of power. Batteries might be good too, especially some of the new varieties under development. Pumping water up a hill is another option being tried, although it would work only near mountains at the moment. Heating – or cooling – something and then taking out the heat when needed might work too. A serious alternative to all this could be compressing air and releasing the pressure when needed. One could split water using the sun’s energy and store the hydrogen for burning later. And so on.All of these technologies are being developed for grid storage, and all of them have problems of some sort, not the least of which is high cost. Energy policies have a tint of legacy, as they have not been framed considering renewable energy and storage in mind. “Technology and regulatory policies have to feed off each other,” says Pramod Kulkarni, an energy consultant in the US who has worked with the California Energy Commission for over two decades. “When policy takes the lead, it pushes technology.”One of the reasons why this has not happened is that power companies have a greater say in policies than the consumers. “While consumers favour introducing energy storage to the grid the generators will oppose it,” says Jay Apt, professor of technology at the Tepper School of Business at Carnegie Mellon University. Introducing storage might reduce profits of the generating companies in large scale, while profits are possible in small scale.Energy storage will thus make its way first to micro-grids. At IISc, AK Shukla is contemplating building microgrids with storage, if the government agrees to a proposal. To use storage in larger grids, and to keep the costs down, technology has to improve. Indian lead acid battery manufacturers are pushing their products for the grid, but low costs can be achieved only if technology breakthroughs are made.Apt, a former physicist and astronaut who is now an energy researcher, picks out some technologies to watch in the near future. One is a startup from Carnegie Mellon itself, called Aquion, which uses non-toxic materials to make a battery that somewhat resembles the lithium ion battery but is as cheap as lead acid. It also lasts twice as long as the lead acid battery. Apt’s second pick is an ‘organic mega flow battery’, also made from earthabundant and non-toxic materials. It has been developed by Harvard professor Michael Aziz.In recent times, flow batteries have become extremely promising. They are so named because a liquid flows inside the cell and reacts with the electrodes.There are several kinds of flow batteries, most of which are bulky but some use relatively cheap materials. Scientists expect advances in this technology, therby making it suitable for grid applications. It might have competition from the lithium ion battery, which has advanced significantly in recent times, and become cheaper and safer.The other emerging batteries include those made of sodium or magnesium. “New technology is now beginning to see commercial deployment,” says Landis Kannberg, who leads the energy storage programme at the Pacific Northwest National Laboratory (PNNL), “but they need to be proven in large numbers.” The next few years would be exciting to watch, as these new technologies make their way into the market.