These innovative battery technologies play a key role in reducing energy storage costs and creating new energy sector opportunities.
FERMONT, CA: The world produces and uses more renewable electricity than ever before, but it is produced by intermittent, weather-dependent sources such as solar and wind in many cases. While these are imperative for a decarbonized future, they cannot generate power all the time, and this can lead to power supply gaps. If the batteries can store renewable electricity from intermittent sources when it can be generated, it could be used at times when it is not. The problem, however, is the technology that can store electricity on a scale that is sufficiently large to power a city that does not yet exist. The race is well underway, and several companies are working to build ever larger, more efficient methods of storing electricity. Here are a few storage technologies that shape the landscape of storage.
Because of their high-energy density and low self-discharge speeds, lithium-ion batteries are already the go-to power source for most home electronics. Yet, companies are looking to expand their use by rapidly advancing the technology to take on larger and better applications, most importantly, Electric Vehicles (EVs) and providing supply protection to national and regional electricity networks. The world's largest 100 megawatts lithium-ion battery plant supplies 30,000 homes for an hour, such as when the wind drops and the wind farm turbines it is attached to do not produce a lot of electricity. Lithium-ion batteries are the most widely used in EVs, but manufacturers still face the challenge of reducing their production costs to a point where EVs are widely available.
Flywheels and Supercapacitors
Some of the most responsive forms of storage of energy, flywheel, and supercapacitor storage can both discharge and recharge faster than most conventional forms of batteries. The first works by using electrical energy to spin a rotor (or flywheel) to very high speeds. This process creates kinetic energy that is effectively stored until it is needed within the spinning rotor, at which point the kinetic energy is converted back into electricity. Supercapacitors are taking a similar approach but electrically store energy. These store energy as a static charge with the combined properties of a battery and a capacitor, but there is no chemical reaction during loading or discharge, unlike traditional batteries.
For most domestic batteries today, be it on smartphones or EVs, the primary complaint is that they just don't last long enough. This is where batteries from the solid-state have a major advantage. Solid-state versions are smaller, simpler and have a higher energy density than lithium-ion batteries using solid electrodes and electrolytes instead of liquid electrolytes (used in most commercial batteries). These can also be charged much more quickly and emit less energy. This can result in improved efficiency, lower costs, and safer operation in an EV.
Hydrogen Fuel Cells
Hydrogen is one of the most common elements on earth, so for any power generation technology, it is a desirable gas. The latest to appear is hydrogen fuel cells, which in the automotive space are increasing in popularity. The fuel cells work in the same way as two electrodes separated by an electrolyte battery. Nevertheless, as long as a constant supply of hydrogen and an oxidizer are pumped through it, hydrogen fuel cells will continue to produce energy rather than run-down and need recharging. This means that a daily hydrogen supply needs to be fed in to keep generating power–prompting the proliferation of fueling stations where hydrogen-powered cars can 'fill-up' with hydrogen when their batteries run out. Hydrogen fuel cells were also used to power buildings and NASA satellites in addition to powering cars.
But what if EVs can function as energy storage systems beyond just using electricity? Both vehicles spend long static periods of time between journeys. Vehicle-to-grid (V2G) systems will take advantage of this and allow EVs to discharge their stored electricity for grid-wide distribution, helping to meet demand during peak times. Cars can actually turn into mini-power plants. Several businesses have already created plans for this type of system and are planning to install about a hundred 'car-to-grid' charging points throughout the UK. When needed, EVs plugged into these sites will be able to charge their batteries as well as feed stored energy back to the National Grid. Smart charging systems will help further automate this electricity supply and enable EVs to further contribute to reducing overall carbon emissions.
Compressed Air Energy
Compressed air energy storage functions like pumped hydropower, but excess electricity is used to compress and store underground energy instead of moving water uphill. The pressurized air (which allows it to expand) is heated and released when energy is required, driving a turbine. Compressed air is the second largest form of energy storage behind pumped hydro-energy. It is continuously developed to become more efficient and less dependent on fossil fuels for heating air. And like pumped hydro, it is a site-specific storage device. Within natural geological formations, such as disused hard rock or old salt mines, compressed air is usually best stored.
Redox Flow Batteries
Flow batteries are inexpensive than lithium-ion grid-scale storage, with a particular focus on renewable energy storage, and provide a longer lifecycle. Flow batteries consist of two liquid tanks that are pumped into a reactor where a charge is produced. Therefore, the capacity of the storage facility is determined by the size of the tanks holding their respective liquids, which may mean that they are voluminous and space-intensive. However, compared to other grid-scale storage systems, flow batteries are more economical, suffer from lower vulnerabilities, and may hold potential for long-term storage of large amounts of energy.
What more energy storage resource to use than the air around? It is converted into a compressed liquid by cooling air down to -196oC, which can be processed. When this fluid is exposed to ambient air, it quickly re-gasifies and expands in volume, spinning a turbine in the process. One of the main advantages of such storage type is its potentially high strength–it is possible to reduce an incredible 700 liters of ambient air to just one liter of liquid air. Moreover, by using waste heat and cold from industrial processes such as thermal generation plants, steel milling, or the creation of Liquefied Natural Gas (LNG), it can become even more efficient.
An energy storage system is the solution to meet increasing demands for electricity. Storage will reduce energy dependence on imports and provide fewer emissions than ever before with electricity. The ability of the nation to implement the future's advanced and efficient grid depends on cost-effective, widespread energy storage technologies being developed and deployed.