Efficient energy storage forms an important aspect in the implementation of renewable energy at an affordable rate for all. Given the natural fluctuations in solar and wind energy because of seasonal cycles, it becomes crucial to store the generated energy for later use. Technological advancements have made renewable energy sources such as sun, wind, and tide much cheaper but what about the storage of this generated energy? Storage of energy obtained from renewable sources require specific infrastructural facilities at present. These facilities are expensive to make and have a high maintenance cost. Moreover, the facilities require specially trained, skilled technicians for operational processes. As a result, it becomes difficult to use these energy sources in the regions which lack the said facilities, especially in third-world countries.
Conventional energy storage systems
Batteries and pumped hydropower are the two most commonly used storage systems available in the market at present.
- Battery stores energy in chemical form and later converts it to electrical form when plugged into a device. The first ever battery was built by an Italian physicist Alessandro Volt in the 1800. The battery was called a voltaic pile as it had zinc and copper stacked like a pile. In the coming years, batteries were made using different compositions such as nickel-cadmium, nickel-iron, lead-acid, nickel-hydrogen, lithium, etc. The batteries that we use today are sophisticated and efficient versions of the crude batteries available back in the day. There are non-rechargeable and rechargeable types of batteries. The most popular batteries these days are lithium batteries on account of their several advantages such as being long-lasting, quick to get charged, energy efficient, and so on. Despite all these advances, battery technologies do not provide a sustainable energy storage system given its limited life span, higher costs, waste generation, and recycling issues.
- Pumped hydropower storage stores electric energy in the form of the gravitational potential energy of water. The system has water reservoirs at two different elevations and it generates electricity with the movement of water along the elevation gradient. Pumped hydropower is one of the most common and established systems for energy storage across the world. It is also used for the storage of energy generated by renewable sources. However, the system too has some drawbacks such as high installation costs, large land space requirements, specific topographic requirements, etc.
A lot of research is thus being conducted to find a cost-effective, simple, and sustainable energy storage system.
Non-conventional energy storage systems
- Molten salt storage – Molten salt storage is based on the principle of thermal energy storage. The technique uses molten salt at a very high temperature (app. 575℃) to store energy. Electricity is generated by the turbine movement triggered by the steam released by molten salt. The system provides many advantages such as low-cost, non-toxic, etc. However, the system has certain disadvantages when it comes to thermal stability, energy efficiency, and specific infrastructural requirements.
- Compressed Air storage – Compressed air energy storage involves storing electrical energy in the form of compressed air at very high pressure. It is an excellent solution for small-scale, on-site energy storage systems. The system offers a long-term energy storage solution and has high capacity. However, there are certain disadvantages like low power density, high transportation losses, and the requirement of specific geological locations.
- Ice energy – The technique uses ice to store thermal energy. It uses generators to make ice during the off-peak periods. The ice is later melted to provide cooling solutions during the hour of requirements. It serves as a battery for a building’s air conditioning system. The system is quite efficient with low maintenance and is environment friendly.
The energy storage systems described above provide alternatives to conventional storage systems and can be used suitably as per the need and facilities available.
Can we make energy storage more sustainable and cheaper?
In August 2020, a team of researchers at Washington University, St. Louis, published a paper in Nature Communications stating to have developed smart bricks that can store energy. Red bricks are the most commonly used materials for construction across the world. These smart red bricks are iron oxide rich and have a layer of conductive polymer coating called PEDOT. This facilitates electricity storage in the bricks. The team demonstrated that the brick can power a LED bulb. The brick has the potential to store renewable energy and power the building using the same. The invention has opened a new channel in the area of sustainable buildings. The research is still in its budding stage and has lots of scope for future development and applications.
Rondo Energy, Bill Gates-backed company from California, has developed a ‘brick toaster’, which is based on a similar concept. The company has started a plant of a brick toaster, a collection of bricks that store renewable energy and delivers the stored energy on demand as high-temperature heat and/or electricity to the cement, steel, and chemical industries. The technique is believed to significantly reduce the carbon footprints of the said industrial sectors. These bricks are called Rondo Heat Batteries (RHB). The RHB is made up of commonly available materials such as clay mixture, sand, and iron. The RHB is equipped to store almost 1 MWh per square meter of energy. The RHB system provides affordable and sustainable energy storage systems with no need for sophisticated infrastructural facilities.
The non-conventional energy storage systems, especially brick batteries are likely to change the face of the energy storage sector making it less carbon-intensive while keeping the costs down. Implementation of these techniques will be a great leap toward our climate action goals.