Energy storage makes the power network more reliable, secure and cost-effective. Batteries are the most effective storage devices for harnessing renewable energy, and a lot is happening globally to make them more powerful and reliable.
By Potshangbam July
Electricity from renewable and non-carbon sources is the need of the hour to tackle the rising carbon emissions that lead to environmental degradation. However, the concern with regard to renewable energy is its unreliability, or rather, the inability to generate seamless power. The generation of renewable energy is largely dependent on the weather and the climate, both of which keep fluctuating, leading to inconsistent or insufficient supply of energy. Batteries play a key role in bridging the gap between power generation and consumption, as they can store any excess energy produced and supply uninterrupted power when the energy source is not available. Thus, energy storage technology can help to supply sustainable clean energy.
In India, the energy storage industry is at a nascent stage. However, the sector is expected to record robust growth in the coming years because of the government’s initiatives, the rising awareness about the damage caused by carbon emissions, falling prices, and so on.
Benefits of energy storage
The need for energy storage has increased dramatically with the extensive use of renewable energy. Batteries play a key role in preventing energy losses, storing all the excess energy generated and using it during the night or in unfavorable climatic conditions—for instance, when energy generation from the sun stops entirely due to extended periods of cloud cover. The biggest advantage of batteries is that the saved energy can be used when demand peaks in the evening. What’s more, since energy from these sources is very unstable, and tends to fluctuate very often causing massive balancing problems for the grid, batteries play the role of a stabiliser.
In addition, energy storage enables more flexibility and ensures uninterrupted power, whenever it is needed. This increases the reliability of power. Besides, consumers can reduce their electricity bills by using the option to sell the saved power back to the grid when energy prices are high. Energy storage is indispensable for tapping renewable energy sources, and is the best solution for creating a carbon-free energy ecosystem.
Life expectancy of a battery
A solar battery’s useful life span ranges between five and 15 years. To accurately estimate the life span of a battery is not an easy task as there are many factors that impact this, such as the number of charging/recharging cycles, excessive overcharge/over discharge rates, operating conditions like temperature, extreme environmental conditions, etc. Even the life span of a battery that is properly maintained cannot be predicted. One factor is that batteries corrode over time, which accelerates their deterioration.
However, the life span of a battery can be extended with good maintenance practices. First, using a large number of batteries in one bank should be avoided. Ideally, this number should not go beyond four, otherwise it may increase resistance which can lead to unequal charging. Next, overcharging can reduce the effectiveness of the batteries. It is important to enhance equalisation on solar batteries. A solar charge controller can be used to suppress overcharging and control the reverse power flow. At the same time, batteries should not remain inactive and uncharged for a long time. They are very prone to damage and rust when not in use. Also, the size of the battery should be appropriate for a given application. It is essential to identify the most appropriate size and type of battery for a particular application, to ensure a long life span.
The battery installation process
It is always safer to install the battery in well ventilated enclosures, preferably at a little distance from the house —not inside or just outside the house. This is because batteries release a corrosive mix of hydrogen and oxygen gases which are harmful and could be explosive. These gases are emitted during the last stage of charging and could cause a major fire when the batteries are left exposed. It is important to note that batteries should not be installed in areas exposed to the sun and should be protected from excessive heat. High temperatures are not suitable as that can cause electrodes to buckle or erode very quickly, well before it would normally occur.
One must ensure the batteries are not in direct contact with the ground or installed directly onto a concrete floor. Rather, mount the batteries on stands or thermally insulate them from the floor, as they are susceptible to fluctuations in ground temperature. The resultant electrolyte stratification can hamper the performance and life span of a battery. And low electrolyte temperatures also bring down the capacity of a battery. Besides, the installation must include a switch or quick-disconnect fuse near the batteries, so that these can be electrically isolated from the rest of the system.
The cost factor
The costs involved with energy storage are arguably one of the main hurdles to overcome. The value of battery systems varies depending on the number and the types of batteries used, and their applications, such as residential, industrial, utilities, etc. What increases the cost more is the integration methods of various batteries, which can be in the form of modules, packs and racks. The integration of battery management systems with the wiring adds to the costs. Among the various battery technologies, lithium-ion batteries, lead-acid batteries and flow batteries require high capital investments due to their energy density, high discharge power and enhanced performance.
Lithium-ion batteries are relatively more expensive than other options. Despite the high cost, they are widely used due to their favourable characteristics, such as high energy density, relatively low self-discharge and minimum maintenance requirements. A study by research company BloombergNEF (BNEF) indicates that energy storage installations around the world will multiply exponentially, from a modest 9GW/17GWh deployed as of 2018 to 1,095GW/2,850GWh by 2040. This 122-fold increase in stationary energy storage capacity over the next two decades will require US$ 662 billion in investments, and indicates a potential decline in the price of lithium-ion batteries, on top of an 85 per cent reduction between 2010 and 2018. The study says India may emerge as the country with the third highest energy storage installations by 2040.
The Indian energy storage market
With the objective of reducing carbon emissions, the government of India has set an ambitious target of reaching a renewable energy capacity of 175GW by 2022. Towards this end, it is offering several incentives and monetary subsidies to boost the adoption of battery energy storage systems. According to the India Energy Storage Alliance (IESA), the energy storage market in India was worth US$ 2.8 billion in 2018 and is forecasted to grow at a CAGR of 6.1 per cent till 2026. Currently, the Indian battery market is dominated by lead-acid batteries for power backup applications. This sub-segment has reported annual sales of over US$ 6 billion. Indian manufacturers aim to come up with upgraded versions of lead acid batteries, such as lead carbon versions and the UltraBattery, a hybrid, long-life lead-acid battery. At the same time, Li-ion batteries are also popular in the Indian market due to their efficiency, low self-discharge and declining prices. To sum up, energy storage is the answer to India’s quest for clean and renewable energy in the next few years.
EB: Evaluating batteries for renewable energy systems
The first and foremost consideration while weighing one’s battery options for renewable energy systems should be a thorough cost-benefit analysis. The affordability and other associated benefits of a particular type of battery will determine whether or not you should go for it. The other product specifications that merit attention are the battery capacity, power ratings, depth of discharge, round-trip efficiency, battery life and the warranty period.
The battery capacity and its power ratings would depend more on your specific needs and usage pattern. If you plan to run your entire premises on solar energy, you will need a bigger battery with higher power ratings.
The depth of discharge refers to the maximum battery capacity that should ideally be used for optimal performance before the next recharge. So, a higher depth of discharge is worth considering as it enables you to use more of the battery’s capacity. Likewise, you should opt for a battery with higher round-trip efficiency as it allows you to derive maximum electricity from the power you have fed into the storage device, and thus get more value for money.
EB: The best battery for renewable energy systems
While upcoming solar parks are increasingly employing new energy storage technologies, lithium-ion batteries are still the most preferred due to their efficiency, versatility, affordability and longer life span. Backed by constant technological upgrades, mass production and declining prices, these batteries will continue to drive the renewable energy storage solutions market, at least for the next one decade.
The cost of Li-ion batteries has dropped by more than 85 per cent in the past ten years, and this trend will continue. Making room for major improvements, Li-ion batteries are fast evolving with the times. For instance, experimenting with different materials for the cathode, like cobalt, nickel and manganese, has increased the energy-holding capacity of these batteries, which are being used in electric cars and being connected to the power grid, like never before. There has been another notable technological breakthrough that has enhanced the energy storage capacity of Li-ion batteries by 20 per cent. This was achieved by fashioning a silicon based powder into an anode. With silicon able to hold more lithium than the carbon in graphite, the most common anode material, the new development helps store more energy.
EB: Technological advances in renewable energy batteries
Rapid advances are taking place in energy storage technologies. Billed as the likely successor to Li-ion batteries, solid-state batteries, which have a higher energy density and fewer safety concerns than lithium, are getting better and better. Several companies are working on improving their performance and lowering their costs. Unlike lithium batteries, solid-state batteries do not have any flammable liquid that can cause laptops or cars to catch fire. Toyota Motor Corp. is working on solid-state batteries to drive its long-range electric vehicles which can travel up to 500 miles on a single charge. Incidentally, the company has the highest number of patents for solid-state batteries. In order to meet the growing requirement for storing renewable energy on a larger scale, CCT Energy Storage, a company based in South Australia has developed the world’s first operational thermal energy device which can store six times more energy than Li-ion batteries. Completely recyclable, cheaper and longer-lasting, these batteries can take any form of electrical input to convert it to thermal energy.
In yet another notable advancement, Saurea, a France-based start-up, has developed the world’s first autonomous photovoltaic motor, an energy storage device that can convert solar power directly into mechanical motion without relying on power electronics or batteries. The device can operate water pumps and ventilation systems for more than 20 years, and that too without maintenance. Another promising technological breakthrough that scientists at the University of Illinois, Chicago, claimed to have achieved is the development of lithium-CO2 storage devices which have seven times higher performance and energy density than lithium-ion devices. Overcoming the stability problems associated with the lithium-CO2 device, scientists now claim that it remains stable over 500 cycles. Next on the cards are hydrogen-based energy storage technologies with solid-oxide fuel cells and reflow batteries, which are expected to revolutionise the market.
EB: Challenges faced in the deployment of battery systems
Apart from the challenge of keeping up with the rapid pace at which energy storage technologies are advancing, the large scale deployment and application of these technologies faces multiple challenges. To begin with, advances in energy storage technologies require innovations and breakthroughs in capacity, longer life span, lower costs and safety (applicable for electrochemical energy storage). Developing storage technologies with higher efficiency and lower costs is a formidable task in view of the high R&D expenses. Second, research in this area should focus on energy storage simulation and operation optimisation in multiple applications, which can help develop demonstration projects so as to promote the industrialisation and commercialisation of energy storage.
The other challenges facing the energy storage industry include lack of policy support in the form of incentives and subsidies, lack of standardisation, high costs, lack of clarity about applications and the unregulated market. The government should take effective steps to promote R&D in energy storage, expand the scope of its applications, establish a sustainable development model, and create a conducive environment that encourages the adoption and operation of energy storage on a commercial scale.