Renewable energy production, particularly from sources such as solar and wind has increased like never before, but unfortunately it is intermittent because of its weather dependence. This can cause serious gaps in electricity supply. One possible solution is storage. If renewable electricity generated from intermittent sources can be stored, it could then be utilized at times when there is no generation. Unfortunately, technology capable of storing large amount of electricity is still being developed.
High capacity storage facilities will improve the reliability of power supply during the course of natural disasters. It will maintain and improve power quality, frequency and voltage which is now required for almost every segment like smart homes, electric vehicles, stationary and grid applications, etc.
Infrastructure needed for electricity storage is in the range of Giga Watts but it is available in Kilo Watts range, which means only ~2% of generated power can be stored. Electricity generation facilities are abundantly available as compared to electricity storage infrastructure which is still a subject of research. Electricity storage facilities were never considered an important factor earlier but now, as the demand for smart cities, intelligent infrastructure, green environment and electric vehicles has increased, this requirement too has become very critical. Such an infrastructure will provide a continuous and flexible power supply for consumers while continuing to be more of renewable energy and less of fossil fuels with reduced carbon-dioxide emissions.
Storage technologies are of two types:
This paper will deal with technologies for storing the produced electricity which comes under electro-chemical storage system such as electro-chemical capacitors, lithium ion batteries, nickel cadmium batteries, nickel metal hydride batteries, solid state batteries, lead-acid batteries, flow batteries, metal air battery, sodium sulphur battery, sodium nickel chloride battery, flywheels, supercapacitors, etc.
Electricity storage can directly drive rapid decarbonisation in key segments of energy usage. In transport, the viability of using battery in electric vehicles for storing electricity is improving rapidly. Stationary electricity storage can provide a range of energy services in an affordable manner. As the cost of emerging technologies falls further, storage will become increasingly competitive, and the range of economical services that it can provide is only set to increase.
In future, energy systems will rely on a large array of services based on effective and economical electricity storage. This plethora of service needs, with varying performance requirements, implies an important opportunity for different storage technologies.
Total electricity storage capacity is set to triple in energy terms by 2030, in case countries proceed to double the share of renewables in the world’s energy system.
Kagra Inc., a Japan based battery manufacturer and a pioneer in capacitor management system and battery sustainment system, recently filed a patent application US20170201102, discloses a two-terminal circuit to provide electricity storage element charging in a short time while voltages are balanced among the electricity storage elements. It consists of voltage applier which applies a constant voltage to the electricity storage elements in a state that all of the electricity storage elements are connected in parallel.
Kyocera Corp., a Japanese ceramics and electronics manufacturer and leading provider of solar power systems, has filed a patent application US20180287217 that discloses electricity storage apparatus, and an electricity storage system control method. It comprises of multiple electricity storage apparatus and power controllers configured to be charged using electric power and also control the charging and discharging of respective storage cells.
Nippon Chemi-Con Corp., a Japanese producer of capacitors and other discrete electronic components, has filed a patent application, US20180047961A1, disclosing a separator for an electrical storage device such as an electrical double layer capacitor, lithium ion capacitor, and lithium ion secondary battery. The separator for electrical storage devices are excellent in tearing strength while providing compactness and resistance performance. The electrical storage device improves the yield at the time of preparation, while reducing the internal resistance value, shorten the defect rate, and reduce the leakage current value by using the separator.
Toshiba Corp., filed a patent application, US20180067167A1, disclosing a storage system that includes:
The storage battery performs charging and discharging of electricity. The first deriver derives a first state of charge (SOC) based on the voltage of the storage battery when a current is not flowing to the storage battery. The second deriver derives a second SOC based on the battery capacity of the storage battery and an integrated value of the current flowing to the storage battery. The corrector corrects the capacity of the storage battery which is used by the second deriver based on a difference between the second SOC and the first SOC. Furthermore, the corrector changes the quantity of correction in accordance with a state of the storage battery.
According to DOE’s Global Energy Storage Database, the following is a list of featured projects in electricity storage area.
Niedersachsen Demonstration Project (sodium sulfur batteries)This project aims to build a large-scale hybrid battery system using lithium-ion batteries and NAS® batteries (sodium-sulfur batteries) used to stabilize the distribution grid and control the balance between electric power supply and demand, by charging and discharging storage batteries. Another aim is to establish a new business model for electricity trading using the battery system.
Tesla announced a partnership with Infigen Energy revealing plans to add a 25MW/52MWh energy storage system at its Lake Bonney wind farm in South Australia. The Power pack battery energy storage system (BESS) will be located adjacent to the 278.5MW Lake Bonney wind farm and connected to the grid via the existing Mayurra substation owned by ElectraNet.
Dubai Electricity and Water Authority (DEWA) has launched a pilot project to install and test a 1.2MW/7.2MWh Sodium Sulfur Battery Energy Storage System (NaS BESS), at the Mohammed bin Rashid Al Maktoum Solar Park, which is the largest single-site solar park in the world. DEWA will connect the storage systems to its grid. The project in cooperation with Amplex Emirates supports DEWA’s efforts to promote clean-energy production and storage technologies.
Vanadium Redox Flow Battery installed at Mirae Paper, a paper making company located in Jeonju. It is modular two-story flow battery system, reduces electric consumption through energy time shifting.
Electricity storage is needed to smooth out the variable loads and maintain reliability. The ideal storage technology depends on the need and application. Large-scale storage will require deployment of billions of dollars to accommodate a grid characterized by renewable energy. Many storage technologies are available but are limited in number on an economic scale. Battery costs, although falling rapidly, continue to remain high at present with applications mainly found in off-grid markets, transport and behind-the-meter uses. As costs fall further, batteries will provide more grid services. Many startups and corporate companies are partnering to explore the area and create a strong hold in this market segment. As the world is looking at smart technologies, electro-chemical based electricity storage technologies are the best available alternatives.