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Energy storage, a smarter way to go green

According to reports, going green is a buzzword being used now-a-days by almost everyone. It is a word quite frequently heard in corporate offices, factories, meetings and at almost every possible corner. But the first set of thoughts that come to mind when the word ‘green’ is spoken out loud, range from recycling plastics and paper to planting trees. Although these are absolutely necessary environment friendly practices, the control over these practices at an individual level is limited. These are more direct ways of going green but at the same time they need to be implemented on a large scale and effectively monitored to be efficient. A lot is being written and done on these. This article would focus on other subtle and indirect yet effective ways of contributing to the environment.

Our country is severely deficit in terms of energy and if the generated energy could be stored in any form then it not just helps meet the ever growing demands but can also contribute heavily to reducing greenhouse gas (GHG) emissions which is after all the whole point behind ‘going green’.

About 70% of India’s energy generation capacity is from fossil fuels, with coal accounting for 40% of the country’s total energy consumption followed by crude oil and natural gas at 24% and 6% respectively. India is largely dependent on fossil fuel imports to meet its energy demands – by 2030, India’s dependence on energy imports is expected to exceed 53% of the country’s total energy consumption. Every kWh of electricity generated from these sources leads to some amount of greenhouse gas emission. A lot of the generated electricity is wasted in various different forms ranging from process constraints to sheer ignorance. So, any contribution towards storing even a little amount of energy can prove to be very impactful.

Fortunately, there are some efficient methods available for energy storage. By energy, we mean electricity as well as thermal energy. A very simple example of an energy storage device is a battery. Battery stores electricity by converting it into chemical energy by means of the electrochemical reactions taking place within. A simple battery-inverter setup for a typical Indian household is considered greener compared to a diesel generator (DG) backup because while the inverter simply stores the electricity that has already been generated, a running DG set would mean additional emissions apart from the existing emissions already made from generating the power fed to the Grid.

Effective storage of electrical energy is a topic aggressively being researched across the globe because combined together with clean technologies like wind and solar, which are intermittent sources of energy, an effective electrical energy storage can result in the cleanest and greenest possible method of generating and using electricity.

Similarly, heat and cold can also be stored by various techniques. Most of them primarily involve a process that utilises the heat/cold, intended for storing, in a somewhat reversible yet stable process. Such processes when reversed, emit the heat/cold stored. A lot of research has been done on using salts for thermal energy storage. In this case, heat is applied to the salt mixture and it is allowed to melt. The molten salt mixture is stored in a molten state until the required heat is extracted from it by a suitable process and it goes back to being a solid salt mixture. There are many other such materials across a wide range of temperatures. These are commonly termed as phase change materials (PCMs) because they store the thermal energy by switching between phases (solid, liquid, gas). These can be used for heating as well as cooling applications.

Ice is one of the most basic type of phase change material. To give an indicative example, imagine a process where you need to run a cooling system during the night. One could always use the grid power or a diesel generator to run the system during the night. But that would certainly mean that there is a considerable emission of greenhouse gases. However, if one desires to go the extra step to be green, they can setup a solar electrical power plant to generate electricity during the day and use it to freeze water to make ice and maintain it in that state. This ice can then be used by a suitable process for the required cooling application during the night. In this case, the GHG emission is zero because no fuel is being burnt here. This process would be ‘green’. This is just an indicative example and for all practical purposes, efficiency and cost parameters will have an impact.

Phase change materials have a wide range of applications with almost every sector finding an application where it can be used. Manufacturing industries can store and use a considerable portion of the energy wasted in the form of hot exhaust gases from furnaces, foundries, DGs and ovens using phase change materials thereby reducing their GHG emissions as well as a considerable reduction in their fuel bills.

Food and dairy industries that use refrigerated trucks can use phase change materials in their transport vehicles. They will just have to freeze these PCMs in their already existing cold storages and then line them up on the walls of their trucks. This will help them reduce the amount of GHG emissions from the truck which would consume larger amount of fuel to run the on board compressor based refrigeration system along with financial savings. Similarly, hospitals can use these PCMs to store medicines. Individuals can use phase change materials to keep their food warm and hence avoid using the microwave. The list goes on and it is evident that it can be adopted even at the most basic level, at an individual level. Whereas, recycling paper and plastics do not have the same privilege. Once it is out of the house, no one knows where it goes.

Thus, it is safe to say that adopting energy storage techniques by using batteries for power backup and PCMs for thermal energy storage have lower environmental impacts and can lead to financial savings also. Energy storage is the smarter option in the ‘green’ pursuit.

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