Various stationary technologies of storage of electricity

The storage solutions of energy are divided into six categories
Mechanics (hydroelectric stopping, Station of transfer of energy per pumping - STEP, storage of energy by compressed air - CAES, wheels of inertia)
Electrochemical (piles, batteries, hydrogen vector)
Electromagnetic (superconductive reels, supercapacities)
Thermics (latent heat or significant).

Mechanical storage

The pumping stations are technologies of storage by gravitation. They are made up of two reserves of water to heights different connected by a system from drains. They are equipped with a system of pumping making it possible to transfer water from the lower basin towards the upstream reservoir in off-peak hours. In full hours, the station functions like a traditional hydroelectric station.
One distinguishes two types of pumping
Pumping stations of contributions: they make it possible to go up via pumps a volume of water between its own tank and the higher reserve of a fall treatment by turbine action. Turbinate water comes thus from the gravitating contributions and the contributions of the pumping station
Stations of transfer of energy per pumping (STEP): they are characterized by an operation in cycles pumping-treatment by turbine action between a lower tank and a higher tank, thanks to reversible turbopumps. Pumping can be mixed, turbinate water comes from the gravitating contributions and of the contributions of the pumping station or pure the natural contributions with the higher tank are negligible
The important size of the installations makes it possible to store great quantities of energy, until several days of production according to the size of the tanks, and of important mobilizable capacities of power in a few minutes, of a few tens of megawatts to several gigawatts according to the height of water.
The STEP can also be installed in maritime frontage, with the sea like reserve lower and a reserve upstream than the top of a cliff or consisted a dam.
The pumping stations play a big role in peak period and are an basic element of safety of the network insofar as their production is mobilizable in a few minutes.
It is probable that new capacities of STEP are planned within the framework of the renewal of the hydroelectric concessions. The definition of the market of capacity envisaged by the law Nouvelle Organization of the Markets of Electricity, said law NAMES, would allow also the development of new storage capacities of electricity.
However, the hydroelectric projects can have environmental impacts and social important which slow down the acceptability of these works.

Storage of energy by compressed air

The installations of storage of energy by compressed air of great power consist, by using electricity available to low cost in period of low fuel consumption, to store air in underground cavities thanks to a compressor. At the time of the peak demand, this compressed air is released to make turn of the turbines which produce electricity thus.
The output of the CAES is unfortunately reduced because the compression of the air is accompanied by a heating. In order to improve the performance of it, of the storage systems thermics are under development in order to recover heat.

Inertial storage

Used a long time for the regulation of the steam engines, the principle of the wheel of inertia makes it possible today to store energy in the form of mechanical rotation temporarily.
A wheel of inertia consists of a mass, ring or tube out of carbon fiber driven by an electrical motor.
The contribution of electrical energy makes it possible to make turn the mass at speeds very high between 8.000 and 16.000 turn/min in a few minutes. Once launched, the mass continues to turn, even if more no current feeds it.
Electricity is thus stored in the wheel of inertia in the form of energy kinetic. It could be restored by using an engine as electric generator, involving the progressive fall number of revolutions of the wheel of inertia.
The storage systems by wheel of inertia have a very strong reactivity and a great longevity. Indeed, this system can absorb very strong variations of power on very great numbers of cycles. However, the wheels of inertia undergo pressure losses because of phenomena of autodécharge and do not allow to obtain one duration of important autonomy. These systems are thus adapted for applications of regulation, energy optimization of a system and improvement of quality.

Electrochemical storage

The storage systems of energy thanks to hydrogen use an intermittent electrolyser. For the periods of low fuel consumption of electricity, the electrolyser uses electricity to break up hydrogen and oxygen water, according to the equation 2 H2O = 2H2 + O2. This hydrogen then compressed, is liquefied or stored in the form of metal hydride.
Then, there exist three different means to reinject electricity on the network starting from stored hydrogen
The first consists in supplying a combustible battery
The second consists in synthesizing natural gas according to the process of the methanation. This gas can certainly be injected directly in the existing gas network but especially be used to feed a power station with traditional gas, producing electricity
The third consists in using hydrogen directly in a power station with gas especially conceived for this purpose, in order to manufacture electricity.
The interest of this type of system resides
In the great flexibility of use of the hydrogen vector, which has as a characteristic to be easily stored and transported, that it is in liquid or gas form
In decoupling energy-power: indeed, the capacity of absorption capacity or production is dimensioned by the electrolyser or the combustible battery. The watt-hour capacity is dimensioned by the size of the tanks and can go several hours at several days according to the application of the system
During their use, the electrolysers and the combustible batteries release from heat, between 20 and 50% of the energy of the system according to the technology, whose valorization improves the economic profitability of the system.

Electrochemical batteries

The electrochemical batteries are designed by stacking of discs made up of various types of chemical elements. There exist thus batteries lead-acid, cadmium-nickel, metal nickel-hydride, lithium-ion, lithium-polymer, lithium-air, sodium-sulfur, sodium chloride (streaked), etc
Stacking is then connected to a system of electronics of power which, during the discharge, converts the D.C. current of the batteries into alternative course to the tension, the frequency and the power desired. This system is also used in the opposite direction to reload the batteries.
In the storage systems by electrochemical batteries, the assemblies of batteries are conceived to provide the power and the capacity according to the uses for example stabilization of the networks, power supply emergency. The storage capacity of power and energy varies according to technologies. The main advantages of the batteries are their flexibility of dimensioning and their reactivity.

Batteries with circulation

In the storage systems by batteries with circulation, two liquid electrolytes containing of the metal ions (couples of metal ions zinc/brominates, polybromure/polysulfide of sodium and vanadium/vanadium), separated by an exchanging membrane from protons, circulate through electrodes. The exchange of loads makes it possible to produce or absorb electricity.
The produced or absorptive power is dependant on the dimensioning of the membrane of exchange and the electrodes, while stored energy is dependant on the volume of the electrolytes.

Electromagnetic storage

The principle of the supercapacities rests on the creation of an electrochemical double-layer by the accumulation of electric charges to the interface between an ionic solution and an electronic driver. With the difference of the batteries, there is no reaction of oxydoreduction.
The interface between the loads plays the part of dielectric. The electrode contains activated carbon of very high specific surface. The combination of a high conducting surface and a thickness of dielectric very weak makes it possible to reach extremely high values of capacity compared to traditional condensers. The electrolyte limits the tension of the elements to a few volts.

Thermal storage (heat and cold)

The installations of thermal storage mainly relate to the industrial and tertiary markets with achievements of about 1 to 10 MW, the heating networks, and the residential market by the means of the medical warm water balloons (ECS).
These installations have an important potential in terms of competitiveness for the tertiary sector and industrial and as regards impact on the demand for electricity with the point. Indeed, by storing heat or the cold in period of weak electricity demand, the potential of shift of the calls of power is important. On the heating networks, the storage of heat makes it possible to optimize the dimensioning of the installations, in particular within the framework of extension of existing networks.
The storage of heat in the medical warm water balloons mobilizes today a park of several million installations, which represents a call of power of several gigawatts to the maximum. This call of power is prédictible and commandable, which makes it possible to shift this call of power in a programmed way.

Comparison of various technologies of storage

There exists today a great number of technologies of storage. Their integration in the electrical communications raises interrogations as for the choice of the technology most adapted to the needs. Indeed, each technology has its specificities in terms of size, delivered power, cost, many cycles and thus of lifespan, energy density, technological maturity, etc
Thus, to compare technologies of storage and to choose the process and the dimensionnementun particular use, several technical factors must be taken into account.
Diffuse storage will make it possible to set up microgrids, to even develop subsistence farming when the tariffs of repurchase of renewable electricity are sufficiently inciting. Centralized storage is interesting as regards profitability. Indeed, it is ensured by the strong one variabilié of the price of electricity on the European market: storage makes it possible to store a bought electricity in period of slack demand and thus at low cost and to resell it in period of strong demand at a higher cost.
Then, various criteria can be used to choose the good technology of storage:
Power available and energy capacity. The combination of these two criteria makes it possible to define the ratio energy/power corresponding to the time of realizable discharge, often characteristic of a particular application
The reaction time is an indicator of the reactivity of the means of storage. It is sometimes preferable to define the rate of rise and decrease in load which characterizes in a finer way the reactive behavior of the system
Effectiveness, definite like relationship between stored energy and restored energy (in MWhOUT/MWhIN)
The lifespan, which it is sometimes preferable to define of many acceptable cycles of load/discharge for technologies like the batteries
For other uses, other criteria are to be taken into account, like the energy density (in MWh/kg or MWh/m3) for mobility for example.
Other criteria are also to take into account such as the exploitation and capital costs, the performances and constraints environmental and the geographical location optimized to limit the losses induced by transport. Certain times, the optimum can even lie in the association of several technologies.

Comparison of the various techologies of storage of electricity (Given DGEC and EPRI)

Technology Capacity Power Response times Costs of the investments (€/kWh) Lifespan (Nb of cycles) Use Comments
STEP 1 to 10 GWh 0,1 to 2 GW 10 min 600 to 1.500 11.000 Network 99% of storage capacities of electricity
Need for compatible sites
CAES 10 MWh with 10 GWh 15 to 200 MW 1 min 400 to 1.200 11.000 Network second adiabatic generation and technologies under development
Need for compatible sites
Hydrogen 10 kWh with 10 GWh 1 kw with 1 GW 100 ms 3000 to 5.000 25 years Industry
Private individuals
Flexibility of use of produced hydrogen
Possibility of developing produced heat
Decoupling of the power of stored energy
and with circulation)
1 kWh
10 MWh
0,01 with
10 MW
1 ms 300 to 3.000 500 to 4.000 Industry
Private individuals
Strong reactivity
The batteries with circulation require a maintenance in temperature
Wheels of inertia 0,5 with
10 kWh
2 with
40 MW
5 ms 3.000 to 10.000 > 10.000 Network Very strong reactivity
Low watt-hour capacity
3 kWh Tension:
2,5 V
3 S   > 10.000 Network
Very strong reactivity
Storage of energy
0,3 with
30 kWh
  8 ms   > 10.000 Network

The services which storage could render to the electrical communications

On the technical plan, technologies of storage of electricity can bring many services to the electric system. These services are classified in four main categories
The help
The smoothing of the load
The maintenance even improvement of the quality of food
The integration of renewable energies of sources

The help

The storage of electricity makes it possible to mitigate the failures of the network and/or to help with the restarting of a generating station like guaranteeing the safety of the public network of electricity.

The smoothing of load

The storage systems are a means
To smooth the active power injected on the network by a means of production of renewable energies, essentially intermittent
To defer the energy production of the periods of slack demand in electricity about the periods of strong demand. That thus allows a better management of the park of production and a reduction of the use of the means of thermal production of point.

The maintenance even improvement of the quality of food

Technologies of storage allow
Supply of reserves of active power making possible the participation in the adjustment of the frequency of the network and/or the mechanism of adjustment
The absorption or the restitution of the power reactivates for the regulation of the tension
The management of specific congestions on the network
To permanently ensure a good electricity supply in substituent the means of production such as the thermo plants.

The integration of renewable energies of sources

The storage systems of electricity are
A means of smoothing the production vis-a-vis the intermittent nature of renewable energies in order to better controlling the quantity of input to network
A means of deferring the production of the periods of slack demand to resell it in peak period where the prices of repurchase are higher in order to improve the profitability of its installation
A means of facing obliterations of production to optimize the production of its installation.
Technologies of storage can also render services economic to the electric system, namely
A easier arbitration on the markets
The possibility of deferring the investments on the distribution networks

Project PUSHY

Project PUSHY, financed by ISI-Oséo, is composed of two sub-projects: the project OSSHY and project LASHY. These two projects are carried out in partnership with ECA Liten, LINDE, WH2, ENERGHY and Green Access. These are two projects of demonstration which will emerge, after validation, on commercial offers.
Project OSSHY concerns the industrialists who wish to produce their hydrogen locally. This project directly does not relate to the storage of energy, this is why one will insist especially on the second shutter of project PUSHY: project LASHY.
Project LASHY puts in contact renewable energy producers of sources with the industrial market of hydrogen. This project has as an ambition to create a die innovating in the sector of industrial hydrogen by installing an electrolyser on a production site of renewable energy, more particularly near power stations microphone-hydraulics concerned with the arrival in the term of contracts of obligation of purchase.
The objective is triple
To develop to the maximum renewable energies
To create a new hydrogen logistics via solid storage
To promote a source of production of green hydrogen
Project LASHY aims to study the coupling of an alkaline electrolyser with a power station of electrical production of the microphone-hydraulics type by allowing an arbitration between production of hydrogen for industrial applications and injection of electricity on the network.
Because of arrival in the term of certain contracts of obligations of purchase since 2012, a certain number of owners and owners of power station microphone-hydraulics will lose their tariff of repurchase of electricity and, therefore, will undergo a fall of their incomes. To mitigate this fall, project LASHY proposes to convert part of electricity produced into hydrogen by electrolysis of water. This hydrogen is then stored in a tank to be sold to industrial customers.
The objective of project LASHY is thus to validate the relevance of such a system and to optimize its operation like its technical and economic performances.

Electrolyze water

The electrolysis of water is a process which uses water (H2O) like raw material to produce gas hydrogen and oxygen thanks to an electric current.
Within the framework of the project, surplus electrical energy makes it possible to produce hydrogen by electrolysis of water. This hydrogen is then stored in solid storages McPhy, then sold to the local industrialists.

Operation of tanks McPhy the storage

The storage of hydrogen in solid form is carried out thanks to metals, called hydrides, which have the capacity to absorb hydrogen. These metals function as of genuine sponges with hydrogen which in the case of absorb hydrogen starting from a certain pressure 10 bar the tanks used for LASHY and restore hydrogen with lower pressure 4 bar.
To build tanks starting from these sponges with hydrogen. It is initially necessary to form discs of hydrides. These discs of hydrides are then piled up to form racks, which one arranges in a shelter until reaching the storage capacity desired by the customer. This technology makes it possible the tanks to be very modular.

Greenergy Box TM of AREVA

AREVA, through its Storage subsidiary company of energy, developed a storage solution and of energy management containing hydrogen: Greenergy Box TM. This development was carried out with the support of the public agency of financing and support for technological innovation OSEO, within the framework of Hydrogen the Horizon program Energy (H2E). Hydrogen the Horizon program Energy (H2E) is a platform of innovation gathering 19 partners sharing competences and means around an objective: to build in France a hydrogen die durable and competitive energy while meeting the needs for the first customers.
This industrial concept innovating, composed of an electrolyser and a combustible battery, is a single device in the world on this level of power. It allows the storage of hydrogen and oxygen obtained by electrolysis of water in period of weak energy demand and their recombination to produce electricity at the time of the peaks of consumption.
Coupled with renewable energies, Greenergy BoxTM brings a solution to the problems of intermittency, by storing surplus energy and by restoring it when the electricity produced by the renewable sources is insufficient.
Greenergy BoxTM has, therefore, three principal functions
Production of hydrogen and oxygen per electrolysis
The storage of energy in the form of hydrogen and oxygen
Production of electrical energy and thermics via the combustible battery

Its features

Of a modular range of power of 20 kw to 100 kw, Greenergy BoxTM offers an important energy storage capacity over one long life. Several systems can be coupled in order to increase the power and the energy capacity and to thus meet the needs for the various markets. Its current electric output from 30 to 35% tends to increase and could reach 45% from here a few years.

A first realization of this concept: the platform of demonstration MYRTLE

Located on the site of Vignola in Ajaccio, the platform MYRTLE (renewable hydrogen Mission for integration with the electrical communication) is resulting from the engagement of three partners: the university of Corsica, the ECA and AREVA. It aims at proving the feasibility of a storage of photovoltaic energy via hydrogen in order to chop the peaks of production of the solar panels.
To this end, a photovoltaic power station of 560 kWc is connected to a hydrogen chain made up of an electrolyser of 10 Nm3/h, tanks of storage of hydrogen and oxygen respectively of 1.400 Nm3 and 700 Nm3 and a combustible battery of 100 kw.
This battery with hydrogen is directly connected to the electrical communication to smooth the production of the photovoltaic panels.
This project, cofinanced by the Corsican territorial collectivity, the State and the European Union received the certification of the Capénergies pole of competitiveness.
Since 2009, AREVA works on the deployment of the hydrogen equipment like on the aspects of integration and safety. In particular, the modes of enforcement of the various regulations, the definition of standards or procedures standards to deploy this type of storage are worked the administrations concerned. Research tasks are undertaken with the INERIS and Liquid air to produce base figures making it possible to better sit these standards and payments.
In January 2012, the platform was inaugurated, after the first tests of coupling to the network, undertaken in December 2011. The tests of characterization and qualification of the subsystems were carried out on site in first half of 2012, and the last adaptations of the site were undertaken for the passage in nominal exploitation. The first operations of the platform in nominal mode were carried out at the summer 2012, which confirmed the functionality of the platform. Maintenance actions for upgrade of the installation are in hand, in order to make profit the platform from technological changes on the hydrogen chain.
It is about a crucial stage for the storage subsidiary company of energy of AREVA which enables him to validate its technology on a pilot scale and to initiate the following stage of industrialization.
Coupled with renewable energies, this process with the advantage of being completely clean.
Moreover, it facilitates the penetration of EnR by allowing the chopping of the peaks of consumption, the attenuation of the variations, and the limitation of overpressures in a context of low fuel consumption.
Lastly, it offers an autonomous energy of help without logistics of provisioning, at the time of cuts of the electrical communication.

Target applications

Shown industrially, the technology of AREVA is a process innovating of storage of energy to the concrete and immediate applications.
Greenergy BoxTM represents a solution for the areas where complex electric provisioning: absence of electric lines, strong dispersion of the population, escarpé relief, etc It, particularly, is adapted to the insular context
Greenergy BoxTM positions, also, on the markets of storage to support the integration of renewable energies to the electrical communication, the security of the domestic network and a decentralized energy management of microphone-districts type.

Storage gravity power

During many decades, the wells and the deep mines with open sky were dug for various applications such as the ventilation of the mines, the access to the layers of ore, municipal public works and the tests of decree of defense. Methods used include drilling and the breath (widespread technology).
The GPM will use the technology and the methods of mining industry with open sky tested, to reduce the cost, at the weak risk and high banc excavation. The principal elements of a GPM are the principal tree, single piston, pressure pipe, system of sealing, devices of positioning of the piston, the powerplant and electrical equipment.
GPM will use the turbopumps Francis type on the level of the ground which are able to provide a great effectiveness to high pressure in the turbine pump modes. These same turbine pumps are basic technology behind PSH and are traditionally designed to measure by using an iterative process of tests and error which requires several years for the development. However, an constant improvement of the knowledge of the hydrodynamics and computational dynamics of the fluids (CFD) with largely improved the capacity of the computer, allow a different approach: computer-aided design based on CFD.
The turbopumps can passed of zero with full power in the large installations of GPM in less than 20 seconds, which confers to them a prompt response ideal for the maintenance of the auxiliary services and the electric markets. Their effectiveness and their capacity are much higher than those of the turbines with combustion with gas. Gravity power studies the offer and the methods of joint ventures with international companies qualified to provide the series production of Francis turbopumps for GPM.
During two last decades, our scientific expert as a chief, Dr. Jingchun Wu, developed a system of optimization of design based on CFD-FEA which integrates in-house tools of design paddles, mailleurs automatic and parameterized mathematical models of geometry, with the code 3D Navier-Stokes commercial. This powerful system provides a means much more effective of optimization and approach traditional test-error and was used to design the wheel turbine pump, tandem cascades, volute and partial of the tube of aspiration to fulfill the specific requirements of a GPM.
execution time customer :
runtime server : 0.07 seconds