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Energy Storage System (ESS) |
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by Fermaud ADOUMADJI MBAIORNOM | 30-11-2022 06:50
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Energy storage consists of preserving a quantity of energy for later use. By extension, the expression also designates the storage of matter containing energy. Energy storage is at the heart of current challenges, whether to optimize energy resources or to promote access to them. It allows to adjust the "production" and the "consumption" of energy by limiting the losses. The energy, stored when its availability is higher than the needs, can be restored at a time when the demand proves to be greater. Faced with the intermittence or fluctuation of production of certain energies, for example renewables, this operation also makes it possible to meet a constant demand. Storage methods depend on the type of energy. Fossil energy sources (coal, gas, oil), in the form of reservoirs in their natural state, naturally fulfill the function of stocks. Once extracted, they can easily be technically isolated, hosted and transported. Storage is more complex for intermittent energies: their production is relayed by energy vectors such as electricity, heat or hydrogen, requiring specific storage systems. The need for storage is a response to economic, environmental, geopolitical and technological considerations. The global increase in demand for fossil fuels, the resulting rise in prices and political unrest in several producing countries make supply partially uncertain. Energy storage is therefore a geostrategic asset, particularly in the case of hydrocarbons. In the economic field, especially during peak consumption, energy storage can help regulate price fluctuations indexed to variations in supply and demand. For businesses and individual consumers, available energy, without interruptions or unexpected price increases, is a necessity in view of current lifestyles. Storage is also a means of limiting losses during overproduction and therefore reducing overall energy consumption. From a technological point of view, the development of portable equipment and hybrid and electric vehicles requires new forms of storage making it possible to accommodate a high density of energy in a limited volume and to restore it easily. Technical or scientific operation In the form of chemical energy Any fuel can be considered as a store of energy in chemical form. When burning, the compound releases energy in the form of heat that can be recovered and recovered. • Intrinsic storage • Hydrocarbons Liquid hydrocarbons are currently the dominant form of bulk energy storage, particularly for the transport sector. The fuels come from fossil fuels and are 75% efficient from "source to pump". Biofuels are derived from biomass, with a yield of 70% "from biomass to pump". • Biomass The term "biomass" refers to all organic materials that can become sources of energy. In the case of plants, it is a form of solar energy storage: organic matter comes from the CO2 captured during photosynthesis. Biomass can be used either directly (wood energy), or after anaerobic digestion of organic matter (biogas) or new chemical transformations (biofuel). However, this energy storage process is long, on the order of several months, and low in efficiency. Indeed, only 1% of the solar radiation used during photosynthesis is returned in the form of biomass. • Hydrogen production Dihydrogen, commonly called hydrogen, does not exist naturally but is very abundant on Earth in atomic H form (water, hydrocarbons, etc.). Many production processes exist, including the reforming of fossil fuels with steam (at 900°C) and the electrolysis of water. Electrolysis, which consists of breaking down the water molecule into hydrogen and oxygen, requires electricity (profitable if the production of electricity itself has a low cost). Hydrogen has the ability to release energy, which makes it a particularly interesting form of storage. It can be used directly as fuel for vehicles equipped with gas-powered combustion engines. It can also be stored before being reconverted into energy by means of a fuel cell, providing electricity and heat. Its use is also envisaged for stationary applications (electricity and heat in houses). Hydrogen has the advantage of being able to be produced from all primary energy sources (fossil, wind, solar). However, the electrolyser-hydrogen-fuel cell systems still have a very high investment cost, for an overall efficiency of less than 50%. In addition, their lifetime is insufficient in the context of applications coupled to the electrical network. In the form of thermal energy Currently, thermal storage is little exploited. Its use should grow with the development of thermodynamic solar farms. • Sensible heat storage Raising the temperature of a material stores energy. This principle is, among others, that of solar water heaters: they recover heat during the day to restore it later, with an average efficiency of around 40% for the most recent systems. The preferred materials are water, synthetic oil, rock or even concrete. For large volumes, heat from solar collectors or industrial waste can be stored underground. Geological storage, which can be coupled with geothermal operations, is still not very widespread. • Latent heat storage This mode of storage is based on the energy involved when a material changes state (for example solid-liquid). The inverse transformation releases the accumulated energy in the form of heat or cold, with an efficiency of around 60%. This technique can be applied in buildings, through Phase Change Materials (PCM). Incorporated into the walls, they serve as a thermal regulator depending on the heat provided by the sun. In the form of mechanical energy This category includes the most well-known ways of large-scale storage: hydraulic and compressed air storage. It also includes flywheels. • Potential mechanical energy • Hydraulic storage It makes it possible to store large quantities of electrical energy through the potential energy of water. A WWTP (pumped power transfer station), a type of hydroelectric plant, is used to transfer water between two basins located at different altitudes. When the grid provides a surplus of electricity, water from the lower basin is pumped into the upper basin. Under the effect of gravity, this mass of water represents a future electricity production capacity. During a power production deficit, the circulation of water is reversed: the pump becomes a turbine and restores the accumulated energy. With an efficiency that can reach more than 80%, it is the most widely used solution for storing energy in power plants. • Compressed air storage When electricity demand is low, existing systems use old salt mines as reservoirs and a motor-generator-turbine package. When the demand for electricity is high, compressed air is used to turn a turbine coupled to an alternator producing electricity. The yield, currently around 50%, is an area of research and development. Compressed air storage from wind and solar energy is the subject of pilot installations in Germany and the United States(1)(2). • Kinetic mechanical energy Energy can be stored as kinetic energy in a "flywheel", a wheel-like device rotating around its central axis. An electric machine supplies it with kinetic energy (motor operation) and recovers it as needed (generator operation), resulting in a drop in the speed of rotation of the flywheel. This system makes it possible to restore more than 80% of the accumulated energy but for a limited storage time. In practice, the flywheel is used for very short-term smoothing of the energy supply within production devices. This is particularly the case for heat engines and especially diesel engines. In the form of electrochemical energy Energy storage in electrochemical batteries is the most common technique for small amounts of electrical energy. Depending on the type of battery (lead-acid, lithium-ion, nickel-metal hydride, etc.), different chemical reactions are caused from electricity: this is the charging phase of the battery. Depending on demand, the reverse chemical reactions then produce electricity and discharge the system. Electrochemical batteries are often intended for portable applications. With relatively low power, they nevertheless have a large storage capacity for long discharge times (up to several hours) with a rate of efficiency of 70 to 80%. These devices can also have emergency functions when the electrical network is faulty or in the case of electricity production from renewable energies, with stored energy values from a few Wh up to 40 MWh. Energy storage systems can be separated into two main families: mobile systems, also called “on-board”, and stationary systems. In the first case, the storage ensures the presence of an energy source during a trip. This is undoubtedly the most familiar category in everyday life since it includes mobile phones as well as thermal and electric vehicles. In the case of stationary systems, the purpose of the storage system is to attenuate, or even cancel, variations in energy consumption or production. This category therefore includes not only all emergency power supply systems, but also thermal storage such as hot water tanks that accompany the majority of building heating systems. Despite these differences, all storage systems have one thing in common: they work in cycles. A cycle consists of charging phases, storage phases and, finally, discharging phases. As described a few paragraphs below, it is by studying the characteristics of these cycles that it is possible to determine which system will be best able to meet the needs of an application. While these characteristics can be numerous and, for some, quite complex, two of them are of particular importance. The first of these key points is performance. It is the ratio between the energy extracted from the system and that previously stored. The second key element is time. This occurs both during the charge/discharge phases and during the storage phases, and thus determines the power of use of the storage system. Sources:
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2 Comments
Hello, this is your mentor Minkyung.
Thank you for sharing abundant knowledge on ESS. I can see that you have put so much effort into doing research on the topic. To make your report even better, if you could explain what the pictures describe, then the readers will understand it more clearly.
Thank you for your hard work, and I'll be looking forward to your next report ;)
Posted 07-12-2022 19:05
Hi, Fermaud ADOUMADJI MBAIORNOM!
This is your mentor, Yoon.
Thank you for sharing your knowledge of energy storage systems.
Your article is not only well structured but also clear and concise. Your writing is convincing as you included reliable sources of information.
I can see the hard work you've done in searching all those specific details.
Excellent job on writing the thematic report.
I am looking forward to reading your following report!
Posted 05-12-2022 00:41