Energy storage systems (ESS). Overview

The efficiency of the use of global energy resources depends not only on the ways of their use, but also on the methods of the generated energy storage. According to the projection of the analysts of GMT Research, the energy storage market size grows rapidly and already in 2020 will be twenty-six times larger than it was in 2014. In 2015, the home energy storage systems comprised about 16% of total market size. This is due to the fact that it is desirable to install the energy storage systems in addition to wind or solar power plants, because the energy is unevenly generated by renewable sources during the day. For example, the solar energy is generated only during the daylight, but it is consumed all day long, or a cloudy day takes place and total volume of the generated energy is less than the volume of daily power consumption of your household. The energy storage systems are designed for use in such cases.

Energy storage technologies

The lithium-ion energy storage technologies are the most widespread on the market of energy storage systems today. For example, lithium-ion batteries were used in 95% of all cases in 2015. They are also widely used in the consumer market and on the car market, where they are set into electric or hybrid propulsion systems. The prices of lithium-ion batteries become lower, their reliability increases, they prove their worth in the systems (propulsion systems) needed to consume much power during a short period and in the systems needed to consume less power during a longer period. Lithium-ion batteries therefore are used by all kinds of consumers: from large utilities specialising in power distribution and supply to individual business entities and accommodation facilities for the storage of energy.

Nevertheless, it is necessary to specify the usability of lithium-ion energy storage systems. Firstly, it is very important that the performance characteristics of different types of lithium-ion batteries shall be appropriate for the specific purposes. For example, the use of a certain type of lithium-ion batteries can be 80% more efficient for big power plants than the application of other types because of rapid charging and discharging. Secondly, other technologies of energy storage can be more applicable in some particular cases. For example, lead-acid batteries can be more suitable for the management of the energy storage in order to satisfy the needs of residential areas. Alkaline batteries are more economical for large-scale power plants, but only in the cases of short charging and discharging periods (less than one hour).

Main characteristics of the energy storage systems

One of the main characteristics of any system of energy storage is effective capacity. The value of this characteristic of the energy storage system depends on nominal capacitance, allowed rate of depth of discharge and the decrease of the battery capacitance over time. For example, Adara Power offers the energy storage system for households with the battery nominal capacitance 8.6 kWh. Besides, specified allowed rate of depth of discharge equals to 75%. It follows that the value of the effective capacity of Adara batteries is equal to 6.45 kWh. At the same time, Tesla, a direct competitor of Adara Power produces the energy storage systems “Powerwall” and their allowed rate of depth of discharge is 100%. The value of effective capacity of these energy storage systems is equal to their nominal capacitance (7 or 10 kWh).

However, the value of nominal capacitance of the batteries is actual only for the first day of their cycle life. Their effective capacity will slowly decrease in the course of time because of battery wear. The cycle life of the energy storage system is the characteristic, which determines the durability of the battery. The service life of the battery depends strongly on the conditions of use. For example, the producer calculates that the lifetime of one and the same battery shall comprise 400 battery cycles under the condition that the rate of the depth of discharge is 70%, or 300 battery cycles under the condition that the rate of the depth of discharge is 85%. These calculations shall be accessible to the clients, but it is almost impossible to find them put into practice.

It is important for the client to know the changes in the battery cycle life under different conditions of use in order to ensure the maximum efficiency of the batteries. For example, Sonnen guarantees that the lifetime of all energy storage systems “SonnenBatterie” is calculated as 10000 battery cycles or 10 years. When such a system is used under standard operating conditions, you get only near 3650 battery cycles per 10 years. That is why you shall realise about 3 battery cycles per day to accomplish near 10000 battery cycles during the guarantee period. The special conditions of use are necessary for this purpose. The energy storage system can be used not only for own consumption, but also for the power supply to the grid.

Business models of energy storage systems

There are some economic scenarios for the owners of energy storage systems. They are described below.

• Stand-alone home power stations. In this case, you use your energy storage system to store the generated power for your own needs and ensuring energy independence of your household. The excess of the generated power is stored in the battery system during the day in order to be consumed at night-time. However, these systems need additional control over the amount of the generated power; the presence of a standby power supply is also desirable. As a matter of fact, this energy storage system shall calculate the power consumption by households in real time for the optimisation of power generation. Besides, the system shall reduce power generation, when the amount of the generated power exceeds the capacity of energy storage system. This way of the solar power plant installation is profitable when the client strives for a full energy independence or in the regions with the high cost of power.
• Backup home power stations. This type of energy storage systems is beneficial to the households, which are situated in the regions of power supply problems. The plants generate power until the energy storage system is completely filled. Then it stops. Your battery system, subsequently, is always charged up to the moment of power supply shutdown. By necessity, you can also generate electricity individually. In this case, you shall calculate the amount of power that is necessary for the supply of the household during blackout periods and install the energy system storage of the appropriate dimensions.
• Grid-connected home power stations. In this case, you aim to sell the generated power for a higher price, than the price for which you purchase power from the government. Taking into considerations the conditions in Ukraine, it is a highly lucrative enterprise, as the government is obliged to buy the power from you at the rate of green tariff correlated with the euro. You do not need to install the energy storage system to sell the generated power directly to the government. It allows you to get considerable cost savings.

Phenomenon of negative electricity price

Negative price of electricity is a relatively new feature of wholesale electricity markets. Negative prices of daily electricity were noticed for the first time in Germany in 2007 and they occur enough rarely at present, but in 2012, within 56 hours per 15 different days, the prices of power decreased to negative values in the process of the determination of power price for the next day. It means that the electricity suppliers should pay for the supplied power consumption by the customers. This phenomenon appears when there is exclusively a low demand for power supply and the supplier decides that the expenses related to the shutdown and reset of a whole power supply system are higher than the costs paid for the generated power consumption by external parties. Negative prices of electricity prove the inflexibility of existing conditions and their appearance conditions the necessity of the use of energy storage systems. The presence of negative prices of electricity stimulates the market of energy storage: instead of purchasing power from the suppliers and selling it later, the owner of the energy storage system can be paid by the suppliers for the consumption of power and sell the power later, getting double profit in this way. Besides, the installation of energy storage systems will cause the increase of the electricity price and a large market of energy storage, on its own, will make negative electricity prices disappear.

Energy storage systems: domestic and industrial standards, actual and perspective developments

The review of global market of the electric power accumulation systems is provided below, we selected the most innovative companies and technologies to present potential solutions variety and diversity of actual technical basis. Thus the estimation possibly intercepted some wonderful and even revolutionary ideas that either are simply impossible to implement due to technical reasons or such implementation will not bring some positive economic effect. Our review list based on companies that already have large resources and able to present the completed innovative decisions, and their reliability and perspectives are confirmed by finished project lists.

Powerwall and Powerpack technology

Tesla is gradually becoming one of global leaders in the area of energy storage systems creation. Novadays Tesla presents two versions of such systems: Powerwall and Powerpack. First can be used in private households and small office apartments, second is intended for enterprises, able to work with high currents and for large number of consumers.

Household version of Powerwall has several models: 7 kW battery costs approximately 3 thousand US dollars, 10 kW option with 3,5 thousand US dollars price and most powerful 14 kW model (5,5 thousand dollars, accumulator capacity is enough for twenty-four hours energy supply of a house with two bedrooms. Customers must pay additional fee of 1500 – 1600 dollars for installation works, invertors and other consumable and expendable materials. Battery dimensions are about one meter breadthways and longwise, thickness is about 18 cm, weight is 100 kg. Accumulator recharge is possible both from wind generator/solar battery and from power grid. Powerwall can be installed indoors or outdoors, operational temperature may vary from − 20 to +43 Celsium degrees. Producer claims 10-years warranty for the battery.

Industrial version of Powerpack has 100 kW of power, but its construction enables easy combination of separate elements into large systems with total power up to 100 MW, that is quite enough for power supply of large industrial object. Approximate price tag is 250 dollars for 1 kW.

Zcell technology

When Redflow company from Australia declared about market launch of home powerful storage batteries with liquid electrolyte, many specialists did not take it with a grain of interest. However, during sales launch in March 2016 first samples got positive reviews. Nowadays Redflow is mainly oriented to the internal Australian market of solar energy consumers.

Permanent “green” tariff reduction combined with growing prices on energy sources make Zcell liquid electrolyte batteries into more and more attractive option for households. The energy storage system developed by the Australian engineers is based on 10 kW zinc-bromine storage battery. Accumulating energy from solar batteries, it gives power back at peak-load moments, at evening and night hours. it is It is quite reasonable to mention some advantages of the battery:

• the maximum possible discharge rate is 100%, and producers claim here, that complete discharge does not affect future battery capacity and its operating parameters in any way.
• battery can be stored in discharged state for a very long time, which does not affect its parameters in any way.
• battery capacity changes from very little to none in course of time, manufacturing company gives 10-year accumulator warranty.
• battery has its own built-in electrical protection system; avialable interface allows to control and to manage system operations via the Internet
• installation simplicity: system is supplied in monoblock formfactor for easy inward or outdoor household installation and network connection.
• ecological safety: all accumulator elements are subject to recycling
• battery dimensions: it is the most miniaturized mass production battery with liquid electrolyte.

Main problems, as some experts suppose, are related to zinc-bromine accumulator, that is very effective at longtitude cycles of energy accumulation and storage, but not so good at short charge-discharge cycles. In addition, most customers got used to be oriented on lithium-ion accumulators, that makes further commercialization of ZCell a bit problematic, especially outside Australia.

SonnenCommunity technology

Sonnen company is the undoubted leader at German market of the domestic energy storage systems, total sale rates are over 10 thousand home power systems. Sonnen presents storage batteries with different capacity from 2 to 16 kW/h, and claims that operation time is no less than the 10 thousand discharge/charge cycles with 80% maximum possible discharge rate.  Recently the company acts not only as equipment producer but also positions itself as service provider at electricity market.

In November 2015 Sonnen started an ambitious project in Germany. SonnenCommunity platform is a possibility to create virtual pool for proprietors of solar systems and electric batteries. Surpluses of electric power, generated by solar batteries, can be distributed among participants of virtual network. For example, some power amount can be transferred to charge storage batteries of other network member or sold on wholesale market in future. Taking into account  rapid decline of “green” electric power tariffs, this will allow green power producers to sell it in real time mode when prices are most favourable. Any user, who purchased Sonnen equipment, can be connected to the virtual network. Sonnen also uses new software that can visualize aggregated storage in real-time.

Market experts recognize Sonnen as the most real competitor of Tesla company, which already sold about thousand systems for domestic solar power-stations. Indeed, the cost of energy storage is lower in Tesla systems, but Sonnen insists on better operational time and charge/discharge cycles quantity.

Smart Towns technology

In Japan, where about 1 million new houses are erected annually, Zero Energy Homes (ZEH) standard will become mandatory in 2020. Panasonic and other Japanese firms, being direct competitors of Tesla’s Gigafactory, already sell turn-key solutions for domestic solar power stations to their local customers, making electric power storage system as an additional feature. Panasonic will implement its own “smart city” project near Yokohama. It is planned that all domestic solar power-stations and systems of energy accumulation within city perimeter will be incorporated in the single network. This will allow not only to provide energetic safety of the city but also to enter the Japanese wholesale market of electric power.

Panasonic is one of the largest producers of powerful storage batteries in the world, large production volumes allow company to sell their products at very attractive prices. Smart Towns is a young, ambitious project, where Panasonic will try to realize new approaches in accumulation and further distribution of electric energy. Thus the company will use the recent Canadian experience, where Panasonic realized large “Sunny batteries + accumulator” project. The company plans to implement a few projects on construction of electricity storage systems for dwelling houses in Australia, even though strong competition at this market.

Sulphuric-natrium batteries technology

NGK Insulators from Japan was one of the first companies to enter the world market of electricity accumulation and storage systems, offering technology of sulphuric-natrium batteries with liquid electrolyte. Nowadays total power of NGK Insulators accumulators all over the world makes about 3 GW, accumulators of this very type form the greatest network of electric storage batteries in whole world, located in Japan. From 2007 to 2010 the company’s share at long-duration electricity storage accumulators market was about 66%. Due to technological features, sulphuric-natrium batteries have a large operational time, but are subject to fire risk at high temperatures.

In spite of the fact that lithium-ion batteries fit better for creation of large systems of electricity storage than liquid electrolyte accumulators, the latter will hold their positions as alternative technology for the long-term accumulation of electric power for some time. For example, quite recently NGK Insulators won a tender to build large system of energy accumulation (35 МW- 280 MW) in Italy.

Intensium Li-ion battery technology

The French Saft company became one of main newsmakers since it was purchased by Total petroleum giant for 1 billion of US dollars, which makes it the largest acquisition for accumulator producers. Before  ownership changes company was an active participant in different projects all over the world, creating systems of electric power storage and management, based on lithium-ion batteries of Saft own production. Main Saft efforts were concentrated on projects in remote areas with high prices of electric power. Installation of 1,2 MW electric system power for a remote settlement on Alaska, large solar power-station in Anahole (Hawaii), and also newest contract on construction of the 10 MW system of energy accumulation in Puerto Rico can be considered as bright examples of company’s work. Market experts make prudent comments on proprietor changes, noting that at the beginning the  company will not be able to compete with such well-known industry leaders as LG Chem, Samsung SDI, Tesla and Panasonic, at least on the production volumes.

Pure Wave S&C technology

S&C Electric has more than 100 years of experience in planning and building of engineering communications, creation and protection of control system for electric networks. Today S&C Electric is one of few leaders in innovative software decisions, intended to increase network reliability, productivity and efficiency.

The company is specialized on development and introduction of solutions both for commercial and industrial objects and private dwellings, and also standalone systems of energy supply. For example, a S&C Electric united 4 electric micronetworks in Texas into single network, combining different sources of electric power generation (solar energy included), and also several systems of electricity storage. In addition, the company developed one of the largest systems of electricity storage in Great Britain. Another 7 МW project is Half Moon Ventures in Minster city, Ohio.

Aqueous Hybrid Ion battery technology

Hybrid ionic accumulator, developed by Aquion company, uses natrium-ion water solution (based on ocean water) and has an ambition to become the most ecologically clean and safe battery at the market. Among other accumulators with liquid electrolyte, Aquion technology is targeted at long-term storage of electric power.

The company successfully provided project financing on early stages of the technology development. Aquion engineers made following calculations: after beginning of mass production of hybrid accumulators, their cost should be about 160 dollars per 1 kW/h. But it’s a little bit early to take such statements as real fact. Aquion mobilized almost 200 million dollars as investments, but succeeded to complete only few commercial projects based on hybrid accumulators. All these projects were implemented on markets, where electricity tariffs are initially very high – for example, in Puerto Rico. To provide Aqueous Hybrid Ion battery technology with some good commercial prospects, vendor company needs some very hard work into expenses reduction.

Zinc-iron flow battery technology

Company ViZN is an another producer, which focuses its interest on large capacity accumulators with liquid electrolyte. Nowadays accumulators with electric power generation based on chemical reaction of iron and zinc, are avialable in different configurations. They are used as a reserve source in home powers systems, for electric power accumulation and redistribution networks, and also for creation of autonomous power networks – for example, for remote deposits development in mining industry. Technology perspectives can be illustrated by the fact, that recently ViZN won a tender on creation of the system of currents stabilization in Ontario (Canada) with 2МW/6MW total power.

Specialists however mention, that new technology of zinc-iron flow battery still needs confirmation of its commercial attractiveness. At considerable cutback on its production costs, batteries of this type can takeover considerable market share of long-term accumulators (3+ hours). In addition, ferrous-zinc accumulators with their  non-acid environment have the best indexes of system  lifecycle and productivity in comparasion to other accumulators with liquid electrolyte. Thus the strategic task of ViZN is to make hard-headed investments, concentrated on expenses reduction due to production technology improvement and production volumes increase.

RESolve technology

Multi-field RES project company became one of founders in building of a large-scale electric depository with 88 MW of total power; another one, much more powerful (200 MW), is now at planning phase.

Vendor company has developed its own RESolve control system, that allows to integrate  all electric power storage devices with different sources of current generation (solar batteries, wind generators etc.) into unified system. The RESolve system determines optimal office hours that allows both to minimize risks automatically and to make correct redistribution of generated energy with maximal profit via wholesale energy selling to the general grid. Nowadays  RES realized about 10 own projects. In addition, Resolve software platform is used in several outsource projects.

YCube technology

German-American Younicos company is one of leading suppliers of software for the systems of energy storage and system integration. The company traces its origins back to research laboratory, so it implements into very strong positions in German industry of solar and and wind power geneartion. Younicos developed the great number of software solutions and utilities for many large-scale projects in Germany. Lately company promotes its own equipment for energy accumulation under Y.Cube brand.

Main Y.Cube feature is module system that can be connected to different sources of electricity generation. Module construction design allows to create systems with total power from 200 kW up to 10 MW (for the long-term storage of electric power), and even more powerful systems up to 20 MW (for short-term electricity storage). Thus software allows to adjust easily main controls of the system.

Advancion technology

Advancion technology is the result of more than 30 years of AES company research and development work at electricity market. Last 8 years company actively works in the segment of commercial energy accumulation and management software for electric power storage systems. For municipal and industrial objects AES offers default configurations of electric energy storage systems from 100 kW up to 1000 MW total power. Company implemented a great number of large-scale projects in Great Britain, Chile and Netherlands, several other objects in India, Dominican Republic and Philippines will be added by the end of 2016.

AES software allows to attend different sources of electric power generation, that is especially important during peak-load intervals. One of key advantages of AES decisions is module construction principle, that allows to grow power capacity according to increasing consumer necessities. By the end of 2015 the company produced 4 version of Advancion. Technology of Advancion can be easily integrated with existing software solutions in energy supply monitoring and management.

AES cooperates with leading producers of industrial accumulators, that enables substantial decrease in financial expenses and build-up time during creation of powerful systems of energy storage.

Hybrid Electric Buildings technology

AMS software allows to optimize management of available resources. Using innovative technologies of load management and due to integration of different sources of electric power and control of power traffic, AMS guarantees its customers trouble-free energy supply even during peak loads. The company already implemented one large-scale project in California as 3,5 MW power storage system for a water filtering plant, nowadays AMS works at even more complex object with 50 MW. AMS uses Tesla Powerpacks for construction of energy storage system.

AC battery technology

The Australian Enphase company is often mentioned as a Tesla competitor foremost due to their active promotion of conceptually different principle of energy storage, namely batteries of alternating current or AC batteries. By the end of 2015 the company presented its own module battery for the home energy storage systems with 1,2 kW/h capacity at the market price about 838 AUD per 1 kW/hour. The battery is already adapted to existing solar power station configurations and can be installed in a customer’s house during 1,5 hours. The company gives 10-year warranty on lithium iron phosphate accumulators. Nowadays Enphase takes orders on systems installations in Australia and New Zeland, but by the end of current year plans to enter USA market and to start work in Europe in 2017.

V2G and 2nd EV life batteries technologies

Partnership of Japanese Nissan motor-car company with Eaton engineering giant (the latter company already has large experience in development of popular Nissan LEAF electrocars), aims on creation of industrial systems of energy accumulation and storage. Today companies realize xStorage, which is pilot project on creation of backup power supply system for a private house in Great Britain.

Due to the fact that the electric power generation by wind generators or solar modules makes some inconstancy, energy storage subsystems became the important part in energy supply systems. The electric power accumulated for a day is delivered in a network at evening hours or at moments of peak consumption, when energy amounts, generated by a solar power-station, appear to be not enough for consumer needs. Thus, it is necessary to understand that system of energy accumulation and storage is not simply an accumulator, leading global companies understant this concept in some other words. Manufacturers offer complex solutions that include both actual accumulators (storage units) and software solution that provide control over accumulator condition and optimal load balancing.