Power Storage: Focus on Trends

In December 2017, news went viral about another record-setting energy storage project as Tesla installed and switched on the world’s largest battery in South Australia.

Tesla’s CEO Elon Musk promised to build the battery in Hornsdale in 100 days or give it to the customer for free. Tesla delivered on the promise, and its 100 MW/129 MWh battery facility joined the list of records that have been broken every several months over recent years. Power storage projects are mushrooming. According to the U.S. Department of Energy, there are more than 1,300 operating power storage facilities in the world, with their total capacity reaching almost 180 GW. So, what is happening in this energy sector? As you probably know, renewable sources of power are unstable in operation and therefore require compensators to be included in energy systems. Other power generating sources were usually used for this purpose, but they cannot keep pace with the swift growth of green energy. Besides, using coal-fired, nuclear of hydro power capacities to mitigate voltage fluctuations in renewable energy systems becomes increasingly less efficient. This has created a new market niche for power storage systems that are capable of replacing conventional generators in fighting the side effects of renewable energy sources. The growing number of electric cars and a pursuit of energy efficiency have also necessitated the use of power storage systems.

People have long been familiar with technologies to store and convert electricity into other forms of energy and back, and some of them have been used commercially for about a century. A distinctive feature of the current boom in power batteries is rapid development of various storage solutions enabling fast delivery of standardized, modular, yet flexible systems of almost any storage capacity to any customer at any geographic point at increasingly more affordable prices. In other words, we are witnessing a revolution in the power storage industry, which looks very much similar to the boom in digital electronics in the 1980s. It was a time when neither personal computers, nor mobile communications were new inventions. The new thing about them was that they became mass, wide-spread products and found new applications. The same is happening now in the power storage industry.

Energy storage systems can be categorized by the mode of action (physical principles applied to electricity conversion) into mechanical (including gravitational, kinetic and pneumatic), thermal, electrochemical and condensing. Certain systems either combine several modes of action or are quite exotic, and they have not gained widespread use. These include solutions that use super conductors, hydrogen energy, etc. as a component of storage systems.

The most widespread are gravity batteries that store energy by lifting a physical body to a certain height with electricity and release the accumulated energy when the body returns to the original level. They include pumped-storage plants (PSP), which are a modification of the well-known small hydro power plants with a water reservoir. The first pumped-storage plants were built in the early 20th century and now account for nearly 95% of all power storage systems in operation globally. PSPs are however large or very large facilities with a capacity of up to several gigawatts, as a rule. They require a large altitude difference and can only be built on very specific site. Resent PSP modifications can remove these limitations to a certain degree only.

Pneumatic accumulators use energy of compressed air (or, seldom, another gas) that passes through a turbine and increases its performance. Kinetic (flywheel) systems accumulate energy by moving a heavy rotor, usually a number of relatively small flywheels. Thermal storage systems accumulate heat to be later used to generate electricity. Certain models accumulate cold, not heat, to be used in refrigerators and therefore decrease electricity consumption by refrigerating facility. Electrochemical batteries store energy via ionization (energy is released when the process is reversed). Their hybrid modifications may also use other physical principles. Electrochemical batteries usually consist of several parallel low-voltage accumulators (1 to 4 volts, depending on the technology). Batteries used in electrochemical storage systems are divided into lithium-ion, lead-acid, sodium-sulfur, redox-flow, vanadium-redox, zinc-bromine and other types. The first three modifications are the most widespread.

Explosive growth is shown mostly by energy storage systems alternative to PSP. A real boom in ‘new’ batteries began early in the current decade and has been gathering pace since then. Over recent years, storage capacity in certain sectors has been growing 40–50% annually. The research and development frenzy in this industry segment is attributable to several converging trends: global greenhouse gas reduction efforts have stimulated an explosive growth of renewables, contributed to energy efficiency improvements, and created a market for electric cars.

These developments have made producers modernize and optimize their storage solutions. Electrochemical systems are simultaneously in demand on three different markets (electric cars, power generation, and energy saving solutions). This is why this technology demonstrates the fastest growth. There are over 700 electrochemical storage systems in operation globally. Their aggregate installed capacity is about 2 GW, with 1 GW more in the construction phase. Investments in the segment exceed 1 billion US dollars annually. Electrochemical storage systems are also growing in scale and capacity. Individual batteries are connected together to form extra large storage systems comparable to medium-capacity power units or water turbines. As such, they can be used by small retail consumers as stationary power sources over a relatively long time period.

Market demand also pushed forward the development of some other storage solutions, which are not used in electric cars or households. These are flywheel, pneumatic and other accumulators, and their use is growing. Since each type of storage system has its strengths and weaknesses, a specific, emerging market trend is to combine different technologies into hybrid storage systems.

The storage market development produces a reverse effect and brings about substantial changes in the power generation segment. First, storage systems are often made part of renewable power generation facilities to damp output fluctuations, thus improving their overall performance. Second, as power batteries gain popularity with end consumers, they (in combination with other solutions) secure massive participation of consumers in controlling power supply, which is seen by many countries as an important contribution to the power market development.

Authored by the Nuclear Asia expert platform