Grid energy storage (also called large-scale energy storage ) is a collection of methods used to store large-scale electrical energy in power grids. Electrical energy is stored during the period when production (especially from intermittent power plants such as renewable electricity sources such as wind power, tidal power, solar power) exceeds consumption, and returns to the network when production falls below consumption.
By 2017, the largest form of grid energy storage is hydroelectricity, with conventional hydroelectric generation and pumped storage. Alternatives include the storage of rail potential energy, in which a rail car carrying a 300-ton weight is moved up or down on an 8-mile section of a sloping rail, storing or releasing energy as a result or storing potential energy of an unused well, at where 100-ton weight is raised or lowered in a 12,000-foot-reduced oil well.
An alternative to grid storage is the use of peak power plants to fill the demand gap.
Video Grid energy storage
Benefits of storing and managing peak loads
Shops are used - feeding electricity to the grid - at a time when consumption that can not be delayed or delayed exceeds production. In this way, electricity production does not need to be drastically increased and down to meet instantaneous consumption - instead, transmissions from a combination of generators plus storage facilities are maintained at a more constant level.
An alternative and complementary approach to achieving the same effect with grid energy storage is to use smart grid communications infrastructure to enable demand responses. This technology shifts electricity consumption and electricity production from one time (when not useful) to another (when needed).
Each power grid must match the production of electricity for consumption, both of which vary drastically over time. Any combination of energy storage and demand responses has these advantages:
- fuel-based power plants (ie coal, oil, gas, nuclear) can be more efficient and easy to operate at a constant production level
- the electricity generated by intermittent sources can be stored and used later, whereas otherwise it should be transmitted for sale elsewhere, or turned off
- peak generation or transmission capacity can be reduced to the total potential of all storage plus deferred charges (see demand-side management), saving costs from this capacity
- prices are more stable - storage costs or demand management are included in the price so there is less variation in tariffs charged to customers, or alternatives (if rates remain stable by law) minus losses to utilities from expensive at wholesale power level -peak when peak demand must be met by import wholesale power
- emergency preparedness - vital needs can be met reliably even without transmissions or ongoing generations while unnecessary needs are suspended
The energy coming from the sun, tidal and wind sources inherently varies - the amount of electricity generated varies with time, lunar phase, season, and random factors such as weather. Thus, renewable energy in the absence of storage presents a special challenge for electric utilities. While linking multiple separate wind sources can reduce overall variability, the sun is reliably unavailable at night, and tidal power shifts with the moon, resulting in ups and downs occurring four times a day.
How much this affects the given utility varies significantly. In the peak summer utility, more sun can generally be absorbed and adjusted to the demand. At the peak utility of winter, to a lesser extent, winds correlate with heating demand and can be used to meet such demand. Depending on these factors, beyond about 20-40% of the total generation, intermittent sources connected networks such as solar power and wind turbines tend to require investment in network interconnection, grid energy storage or demand side management.
In a power grid without energy storage, energy-dependent generation stored in fuel (coal, biomass, natural gas, nuclear) should be increased up and down to adjust the rise and fall of electricity production from intermittent sources (see power generation loads). While hydroelectric and natural gas plants can be rapidly upgraded upward or downward to follow the wind, coal and nuclear power plants take considerable time to respond to loads. Utilities with fewer natural or hydroelectric power plants are thus more dependent on demand management, network interconnection or costly pumped storage.
French consulting firm Yole DÃ © Â © veloppement estimates the "stationary storage market" could become a $ 13.5 billion opportunity by 2023, compared to less than $ 1 billion by 2015.
Request side management and grid storage
The demand side can also save electricity from the grid, for example charging an electric vehicle battery saving energy for vehicles and heating storage, district heating storage or ice storage provides thermal storage for buildings. Currently this storage only works to switch consumption out of peak hours, no power is returned to the power grid.
The grid storage requirement to provide peak power is reduced by the demand time of the usage price, one of the benefits of the smart meter. At the household level, consumers can opt for cheaper off-peak times for clothes washing machines/dryers, dishwashers, baths and cooking. Commercial and industrial users will also take advantage of cost savings by delaying some processes to non-busy times.
The regional impact of unpredictable wind power operations has created a new need for interactive demand responses, where utilities communicate with demand. Historically this is only done in co-operation with large industrial consumers, but can now be extended to the entire grid. For example some large-scale projects in Europe connect variations in wind power to convert the industrial freezing food load, causing small temperature variations. If communicated on a grid-wide scale, small changes to heating/cooling temperatures will instantly change consumption on the grid.
A report released in December 2013 by the US Department of Energy further explains the potential benefits of energy storage and demand-side technologies to the power grid: "Modernizing the electrical system will help countries meet the challenges of handling projected energy requirements - including addressing climate change by integrating more energy from renewable sources and improve the efficiency of nonrenewable energy processes Advancements to the power grid must maintain robust and robust power delivery systems, and energy storage can play an important role in meeting these challenges by increasing grid operating capability, lowering costs and ensuring high reliability, and delay and reduce infrastructure investment.Finally, energy storage can be an instrument for emergency preparedness because of its ability to provide backup power and grid stabilization services. "Report is written by a core group of developers representing the Office of Electrical Delivery and Energy Reliability, ARPA-E, Office of Science, Office of Energy Efficiency and Renewable Energy, Sandia National Laboratory, and Pacific Northwest National Laboratory; all involved in the development of grid energy storage.
Maps Grid energy storage
Form
Air
Compressed air
Another grid energy storage method is to use the off-peak or renewable electricity generated to compress the air, which is usually stored in old mines or some other geological features. When demand for electricity is high, compressed air is heated with small amounts of natural gas and then through turboexpansion to generate electricity.
Compressed air storage is usually about 60-90% efficient
Liquid air
Other electrical storage methods are compressing and cooling the air, converting it into liquid air, which can be stored, and expanded when needed, rotating the turbine, generating electricity, with up to 70% storage efficiency.
Battery
Battery storage is used in the early days of current direct electric power. Where AC power network is not available, isolated lighting plants operated by wind turbines or internal combustion engines provide lighting and power for small motors. The battery system can be used to run the load without turning on the engine or when the wind is calm. A lead-acid battery bank in a glass jar provides power to illuminate the lamp, as well as start the engine to recharge the battery. Battery storage technology is typically about 80% to more than 90% efficient for newer lithium ion devices such as Tesla Powerwall
Battery systems connected to large solid-state converters have been used to stabilize power distribution networks. Some grid batteries are located alongside renewable energy generators, either for alternate wind-powered or alternating solar power, or to divert power output to other hours of the day when the renewable plant can not generate power directly (see Installation example ). This hybrid system (storage generation) can reduce pressure on the network when connecting renewable sources or used to achieve self-sufficiency and work "outside the network" (see stand-alone power systems).
Contrary to the application of electric vehicles, the battery for stationary storage does not suffer from mass or volume constraints. However, due to the large amount of energy and energy implied, the cost per power or energy unit is very important. The relevant metric for assessing the interest of a technology for a storage grid scale is $/Wh (or $/W) rather than Wh/kg (or W/kg). Storage of the electrochemical grid is possible thanks to the development of electric vehicles, leading to a rapid decline in battery manufacturing costs below $ 300/kWh. By optimizing the production chain, the industry's ultimate goal reaches $ 150/kWh by the end of 2020. This battery relies on Li-Ion technology, which is suitable for mobile applications (high cost, high density). The technology optimized for the grid should focus on low cost and low density.
Grid-oriented battery technology
Sodium-Ion batteries are a cheap and sustainable alternative to Li-ion, because sodium is much more abundant and cheaper than lithium, but has a lower power density. However, they are still at an early stage of their development.
Automotive-oriented technology relies on solid electrodes, which display high energy density but requires an expensive manufacturing process. Liquid electrodes are a cheaper and less dense alternative because they do not require processing.
Battery state-liquid
This battery consists of two molten metal alloys separated by an electrolyte. They are simple to manufacture but require a temperature of several hundred degrees Celsius to keep the alloy in a liquid state. These technologies include ZEBRA, Sodium-sulfur batteries and liquid metals. Sodium sulfur batteries are used for grid storage in Japan and in the United States. The electrolyte is composed of solid beta alumina. Liquid metal battery, developed by the group Pr. Sadoway, using Magnesium and antimony liquid alloys separated by an electrically insulating molten salt. This is still in the prototyping phase.
Stream the battery
In a rechargeable charge battery, the liquid electrode comprises a transition metal in water at room temperature. They can be used as a fast response storage medium. The redox vanadium battery is another flow battery. They are installed at Huxley Hill (Australia) wind farm, Tomari Wind Hills in Hokkaid? (Japan), as well as non-wind farm applications. Battery flow 12 MWÃ, Â · h should be installed at Sorne Hill (Ireland) wind farm. This storage system is designed to smooth out transient wind fluctuations. Hydrogen Bromide has been proposed for use in utility scale type flow batteries.
Example
For example, in Puerto Rico, a system with a capacity of 20 megawatts for 15 minutes (5 megawatts hour) stabilizes the frequency of electric power generated on the island. A 27-megawatt (1575 megawatt hour) nickel-cadmium battery bank was installed at Alaskan Fairbanks in 2003 to stabilize the tension at the end of a long transmission line.
By 2016 the zinc-ion battery is proposed for use in grid storage applications.
In 2017, the California Public Utilities Commission installed 396 stacks of Tesla batteries at the Mira Loma substation in Ontario, California. The stack is deployed in two modules each 10MW (total 20MW), each capable of running for 4 hours, thus adding up to 80MWh of storage. This array is capable of lighting 15,000 homes for more than four hours.
BYD proposes to use conventional consumer battery technology such as lithium iron phosphate batteries (LiFePO4), connecting multiple batteries in parallel.
The largest grid storage battery in the United States includes a 31.5MW battery at the Grand Ridge Power plant in Illinois and a 31.5 MW battery in Beech Ridge, West Virginia. Two batteries under construction in 2015 include a 400MWh (100MW to 4 hours) Southern California Edison project and a 52 MWh project in Kauai, Hawaii to fully time shift the 13MW solar farm output into the night. Two batteries are in Fairbanks, Alaska (40 MW for 7 minutes using Ni-Cd cells), and in Notrees, Texas (36 MW for 40 minutes using lead-acid batteries). Battery 13 MWh made of used batteries from electric drive Daimler Smart is being built in LÃÆ'¼nen, Germany, with the hope of a second life of 10 years.
By 2015, storage of 221 MW batteries is installed in the US, with total capacity estimated at 1.7 GW by 2020.
Electric vehicles
The company is researching the possible use of electric vehicles to meet peak demand. Parked and plugged electric vehicles can sell electricity from the battery during peak loads and charge during the night (at home) or during off-peak.
Hybrid cars or plug-in electric cars can be used for their energy storage capabilities. The vehicle-to-grid technology can be used, converting any vehicle with a 20 to 50 kWh battery pack into a distributed load-balancing device or an emergency resource. It represents 2 to 5 days per vehicle with an average household requirement of 10 kWh per day, assuming an annual consumption of 3650 kWh. This quantity of energy is equivalent to a distance between 40 and 300 miles (64 and 483 km) in vehicles consuming 0.5 to 0.16 kWh per mile. These figures can be achieved even in the conversion of home electric vehicles. Some electric utilities plan to use old plug-in vehicle batteries (sometimes producing giant batteries) to store electricity. However, the big disadvantage of using a vehicle to an energy storage network would be if each storage cycle emphasizes the battery with a complete charge-discharge cycle. However, one major study shows that the use of vehicle-to-network storage intelligently actually increases battery life. Conventional lithium ion (cobalt-based) batteries break down with the number of cycles - newer li-ion batteries do not break down significantly with each cycle, so they have a longer lifetime. One approach is to reuse unreliable vehicle batteries in special grid storage [1] as they are expected to be good in this role for ten years [2]. If the storage is done on a large scale, it will be much easier to guarantee replacement of degraded vehicle batteries in cellular usage, since old batteries have value and direct use.
Crazy Wheel
Mechanical inertia is the basis of this storage method. When electricity flows into the device, the electric motor accelerates large spinning discs. The motor acts as a generator when the power flow is reversed, slowing down the disk and generating electricity. Electricity is stored as kinetic energy from disk. Friction must be kept to a minimum to extend the storage time. This is often accomplished by placing the flywheel in a vacuum and using magnetic pads, tending to make the method expensive. The larger flywheel speeds allow for greater storage capacity but require strong materials such as steel or composite materials to withstand centrifugal forces. The range of power and energy storage technologies that make this method economical, however, tend to make the wheel of force unsuitable for general power system applications; they may be best suited for load-leveling applications on rail power systems and to improve power quality in renewable energy systems such as the 20MW system in Ireland.
Applications that use flywheel storage are those that require very high bursts of power for very short periods such as tokamak and laser experiments in which the motor generator rotates to the operating speed and partially slows down during discharge.
The flywheel storage is also currently used in the form of an uninterruptible Diesel rotary power supply to provide an uninterruptible power supply system (such as those at large data centers) for the ride-through power required during transfer - ie, a relatively short time between power loss to sources of electricity and heating of alternative sources, such as diesel generators.
This potential solution has been implemented by the EDA in the Azores on the islands of Graciosa and Flores. The system uses an 18 megawatt-second flywheel to improve power quality and thus enables increased use of renewable energy. As the description shows, the system is designed again to smooth the supply fluctuations temporarily, and can never be used to cope with outages over several days.
Powercorp in Australia has developed applications using wind turbines, flywheels and low-diesel load (LLD) to maximize wind input to small networks. A system installed in Coral Bay, Western Australia, uses wind turbines integrated with flywheel and LLD based control systems. The flywheel technology enables wind turbines to supply up to 95 percent of Coral Bay's energy supply at times, with a total annual wind penetration of 45 percent.
Hydrogen
Hydrogen is being developed as a storage medium for electrical energy. Hydrogen is produced, then compressed or liquefied, cryogenicly stored at -252.882Ã, Â ° C, and then converted back into electrical energy or heat. Hydrogen can be used as fuel for portable (vehicle) or stationary energy generation. Compared to water storage and pumped batteries, hydrogen has the advantage of fuel with high energy density.
Hydrogen can be produced either by reforming natural gas with steam or by electrolyzing water into hydrogen and oxygen (see hydrogen production). Natural gas reforms produce carbon dioxide as a by-product. High temperature electrolysis and high pressure electrolysis are two techniques in which the efficiency of hydrogen production may be improved. Hydrogen is then converted back into electricity in internal combustion engines, or fuel cells.
The efficiency of AC-to-AC hydrogen storage has proven to be in the order of 20 to 45%, which imposes an economic constraint. The price ratio between the purchase and sale of electricity should be at least proportional to the efficiency in order for the system to become economically viable. Hydrogen fuel cells can respond quickly enough to correct rapid fluctuations in demand or power supplies and regulate frequencies. Whether hydrogen can use natural gas infrastructure depends on the construction material of the network, the standard in the joint, and the storage pressure.
Equipment required for hydrogen energy storage includes electrolysis plants, compressors or hydrogen liquids, and storage tanks.
Biohydrogen is a process that is investigated to produce hydrogen using biomass.
Micro-combined heat and power (microCHP) can use hydrogen as fuel.
Some nuclear power plants may be able to take advantage of the symbiosis with the production of hydrogen. High temperatures (950-1000 Â ° C) gas cooled by a fourth generation nuclear reactor have the potential to electrolyze hydrogen from water by thermochemical means using nuclear heat as in the sulfur-iodine cycle. The first commercial reactor is expected by 2030.
A community-based pilot program using wind turbines and hydrogen generators began in 2007 in the remote Ramea, Newfoundland and Labrador communities. A similar project has been taking place since 2004 in Utsira, a small town on the island of Norway.
Underground hydrogen storage
Underground hydrogen storage is the practice of storing hydrogen in underground caves, salt domes, and drained oil and gas fields. A large amount of hydrogen gas has been stored in underground caves by Imperial Chemical Industries (ICI) for years without difficulty. The Hyunder Europe project is indicated in 2013 that for wind and solar energy storage, an additional 85 caves that can not be covered by the PHES and CAES systems.
Power to gas
Power to gas is a technology that converts electric power into gas fuel. There are 2 methods, the first is using electricity to separate water and inject the resulting hydrogen into the natural gas grid. The second less efficient method is used to convert carbon dioxide and water into methane, (see natural gas) using electrolysis and Sabatier reactions. Excess power or peak power generated by a wind generator or solar panel is then used to balance the load in the energy network. Using existing natural gas systems for hydrogen, Hydrogenic fuel cell makers and natural gas distributor Enbridge have been working together to develop such powers into Canadian gas systems.
Storage of hydrogen pipes in which natural gas networks are used for hydrogen storage. Before switching to natural gas, the German gas network operated using towngas, which consisted mostly of hydrogen. The storage capacity of the German natural gas network is over 200,000 GWÃ, Â · enough hours for several months of energy needs. By comparison, the capacity of all German-pumped power plants is only about 40 GW Â ° h. Transportation of energy through the gas network is carried out with much less losses (& lt; 0.1%) than in the power grid (8%). The use of existing natural gas pipes for hydrogen is studied by NaturalHy
Power-to-ammonia concept
The power-to-ammonia concept offers a carbon-free energy storage route with a diversified application palette. At a time when there is a low power surplus of carbon, it can be used to make ammonia fuel. Ammonia can be produced by breaking water into hydrogen and oxygen by electricity, then high temperatures and pressures are used to combine nitrogen from the air with hydrogen, creating ammonia. As a liquid, it resembles propane, unlike hydrogen alone, which is difficult to store as a gas under pressure or cryogenically melts and stores at -253 ° C.
Just like natural gas, stored ammonia can be used as a thermal fuel for transportation and power generation or used in fuel cells. A standard 60,000 m3 ammonia fluid tank contains about 211 GWh of energy, equivalent to an annual production of about 30 wind turbines. Ammonia can be burned clean: water and nitrogen are released, but there is no CO2 and little or no nitrogen oxide. Ammonia has many uses other than as an energy carrier, this is the basis for the production of many chemicals, the most common use is for fertilizers. Given the versatility of this use, and given that the infrastructure for transport, distribution, and safe use of ammonia already exists, it makes ammonia a good candidate for being a large, future non-carbon energy carrier.
Hydroelectric
Water pumped
In 2008 the world's pumped storage capacity was 104 GW, while other sources claimed 127 GW, which consists of most of all types of grid electrical storage - all other types combined are several hundreds of MW.
In many places, pumped hydroelectric power plants are used to equalize the daily power load, by pumping water into high storage reservoirs during off-peak hours and weekends, using the basic load overload of coal or nuclear sources. During peak hours, this water can be used for hydroelectric power, often as a reserve of high-value quick response to cover temporary demand. The pumped storage recovers approximately 70% to 85% of the energy consumed, and is currently the most cost-effective form of mass storage. The main problem with pumped storage is that it usually requires two nearby reservoirs at very different altitudes, and often requires substantial capital expenditure.
Pumped water systems have high delivery delays, which means they can be on-line very quickly, typically within 15 seconds, which makes the system highly efficient at absorbing variability in consumer demand. There are more than 90 GW of pumped storage operating around the world, which is about 3% of global generation capacity instantly. Pumped water storage systems, such as Dinorwig storage systems in the UK, have a five or six-hour generating capacity, and are used to smooth variations in demand.
Another example is the 1836 MW Tianhuangping Pumped-Storage Hydro Plant in China, which has a reservoir capacity of eight million cubic meters (2.1 billion gallons US or water volume over Niagara Falls in 25 minutes) with a vertical distance of 600 m (Leg 1970). This reservoir can provide about 13 GWÃ, Â · h of gravitational potential energy stored (can be converted to electricity by about 80% efficiency), or about 2% of China's daily electricity consumption.
The new concept in pump-storage is utilizing wind energy or solar power to pump water. Wind turbines or solar cells that direct the water pump to store wind energy or solar dams can make this process more efficient but limited. Such a system can only increase the volume of kinetic water during windy and daytime periods.
Hydroelectric
Hydroelectric dams with large reservoirs can also be operated to provide peak generation at peak demand. Water is stored in the reservoir during the low demand period and is ejected through the plant when demand is higher. The net effect is the same as the pumped storage, but without loss of pumping. Depending on the capacity of the reservoir, the plant may provide daily, weekly, or seasonal loading.
Many of the existing hydroelectric dams are quite old (eg, Hoover Dam was built in the 1930s), and the original design precedes newer intermittent sources such as wind and solar for decades. The hydroelectric dam that was originally built to provide baselier power would have a generator size corresponding to the average water flow into the reservoir. Increasing dams with additional generators increases their peak power output capacity, increasing their capacity to operate as a virtual grid energy storage unit. The United States Reclamation Bureau reported an investment cost of $ 69 per kilowatt of capacity to raise an existing dam, compared to more than $ 400 per kilowatt for a fired oil-breaking generator. While a flattened hydroelectric dam does not directly store excess energy from other generating units, it behaves equally by collecting its own fuel - incoming river water - during the high output period of other generating units. Serving as a virtual grid storage unit in this way, an improved dam is one of the most efficient forms of energy storage, since it does not have a pumping loss to fill its reservoir, only increasing losses to evaporation and leakage.
Dams that plug in a large reservoir can store and release large amounts of corresponding energy, by controlling the flow of the river and raising or lowering the level of the reservoir several meters. Limitations do apply to dam operations, their release is generally subject to government-regulated water rights to limit the downstream effects of rivers. For example, there is a grid situation where base load thermal generators, nuclear turbines or winds are producing excess power at night, dams are still needed to release enough water to maintain adequate river levels, whether electricity is generated or not. Conversely there is a limit of peak capacity, which if excessive can cause the river to flood for several hours every day.
Superconducting magnetic energy
Superconducting magnetic energy storage (SMES) stores energy in the magnetic field created by direct current flow in a cryogenically cooled superconducting coil to a temperature below the critical temperature of the superconductor. The typical SMES system includes three parts: a superconducting coil, a power conditioning system and a cryogenic cooled refrigerator. After the superconducting coil is filled, the current will not rot and the magnetic energy can be stored indefinitely. The stored energy can be released back to the network by releasing the coil. The power conditioning system uses an inverter/rectifier to convert alternating current (AC) power into direct current or convert back DC to AC power. The inverter/rectifier accounts for about 2-3% of the energy lost in each direction. SMEs lose the least amount of electricity in energy storage processes compared to other methods for storing energy. The SMES system is very efficient; round-trip efficiency is greater than 95%. The high cost of superconductors is the main limitation for commercial use of this energy storage method.
Due to the cooling energy requirements, and the limit in total energy that can be stored, SMES is currently used for short-duration energy storage. Therefore, SMES is most often devoted to improving power quality. If SMES is used for the utility it will be a diurnal storage device, which is charged from basic load power at night and meets peak load during the day.
Superconductor technical challenges of magnetic energy storage have not been solved to be practical.
Thermal
In Denmark, direct electricity storage is considered too expensive for very large scale usage, although significant use is made of existing Norwegian Hydro. In contrast, the use of existing hot water storage tanks connected to district heating schemes, heated by either electrode boilers or heat pumps, is seen as the preferred approach. The stored heat is then transmitted to the residence using the district heating pipes.
The liquid salt is used to store the heat collected by the solar tower so that it can be used to generate electricity in bad weather or at night.
Off-peak electricity can be used to make ice from water, and ice can be stored. The stored ice can be used to cool the air in large buildings that will typically use electric AC, thereby shifting the electrical load out of peak hours. In other systems, stored ice is used to cool the gas turbine generator's incoming air, thereby increasing the peak generation capacity and efficiency at its peak.
The Pumped Heat Power Storage System uses heat pump/heat pump which is highly reversible for pumping heat between two storage vessels, heating one and cooling the other. The UK-based engineering company, Isentropic, which developed the system claimed a potential electric savings of up to 72-80% of electric current.
Storage of gravitational potential energy with solid mass
According to Scientific American , ski lifts and railways are some places that are considered to store energy by moving heavy objects up or down.
Economy
The cost of measured electricity storage depends on the type and purpose of storage; as a subsecond-scale frequency regulation, small-scale/hour peak mills, or seasonal storage of day/week scales.
Using battery storage is said U $ 0.12-0.17 per kWh.
In general, energy storage is economical when marginal electricity costs vary much more than the cost of storing and recovering energy plus the price of energy lost in the process. For example, assume a pumped-storage reservoir can pump into a reservoir over a volume of water capable of producing 1,200 MWÃ, Â · hours after all losses are taken into account (evaporation and seeping in reservoirs, efficiency losses, etc.). If the marginal cost of electricity during off-peak time is $ 15 per MWÃ, Â · h, and the reservoir operates at an efficiency of 75% (ie, 1,600 MWÃ, Â · h consumed and 1,200 MWÃ, Â · h of energy taken), then the cost The total filling of the reservoir is $ 24,000. If all the stored energy is sold the next day during peak hours by an average of $ 40 per MWÃ, Â · hour, then the reservoir will see $ 48,000 in revenue for the day, for a gross profit of $ 24,000.
However, the marginal cost of electricity varies due to operational and fuel costs varying from different generator classes. At one extreme, basic load power plants such as coal-fired power plants and nuclear power plants are generators with low marginal costs, because they have high capital and maintenance costs but low fuel costs. At other extreme points, peak power plants such as gas turbine natural gas plants burn expensive but cheaper fuel to build, operate and maintain. To minimize the total operational cost of a power plant, the base load generator is sent most of the time, while the peak power generator is delivered only when necessary, generally when energy demand peaks. This is called "economic delivery".
The demand for electricity from various networks in the world varies throughout the day and from season to season. For the most part, variations in electricity demand are met by varying the amount of electrical energy supplied from primary sources. However, more and more operators are storing lower-cost energy produced at night, then releasing it to the power grid during peak periods of the day when it is more valuable. In areas where hydroelectric dams exist, discharges may be delayed until demand becomes greater; this form of storage is common and can utilize existing reservoirs. This does not save the "surplus" of energy produced elsewhere, but the net effect is the same - albeit without loss of efficiency. Renewable supply with variable production, such as wind and solar power, tends to increase net variation in electrical loads, increasing the chances for grid energy storage.
It might be more economical to find an alternative market for unused electricity, than to try and keep it. Direct High Voltage Currently allows for electric transmission, loss of only 3% per 1000 km.
The International Energy Storage Database The US Department of Energy provides a list of free grid energy storage projects, many of which show the source and amount of funding.
Load leveling
Demand for electricity from consumers and industries continues to change, widely in the following categories:
- Seasonal (during dark winters more electricity and heating is required, while in other climates hot weather increases the requirements for air conditioning)
- Weekly (most industries close on weekends, lower request)
- Every day (like the morning when the office is open and the AC is turned on)
- Every hour (one method to estimate television viewing rates in the UK is to measure power surges during ad breaks or after programs when viewers switch to turn on boiler)
- Transients (fluctuations due to individual actions, differences in power transmission efficiency and other minor factors to account)
There are currently three main methods for handling changing requests:
- Electrical devices generally have the working voltage range they need, typically 110-120Ã, V or 220-240Ã, V. A small variation of load is automatically smoothed by slight variations in the voltage available throughout the system.
- Power plants can run below their normal output, with facilities to increase the amount they generate almost instantaneously. This is called 'spinning backup'.
- Additional generations can be brought online. Typically, this is a hydroelectric or gas turbine, which can be started in minutes.
The problem with standby gas turbines is the higher cost, expensive generating equipment not being used far from time. Spinning backups also come at a cost, plants that run below maximum results are usually less efficient. Grid energy storage is used to shift generations from peak load times to off peak hours. Power plants can run at peak efficiency during night and weekends.
The demand-demand leveling strategy may be intended to reduce the cost of peak power supply or to compensate for intermittent wind and solar generation.
Energy demand management
To keep electricity supply consistent and to handle various electrical loads, it is necessary to reduce the difference between generation and demand. If this is done by changing the load it is referred to as demand-side management (DSM). For decades, utilities have been selling power from peak to large consumer at lower rates, to encourage these users to shift their burdens out of peak hours, in the same way that telephone companies do with individual customers. Typically, this time-dependent price is negotiable beforehand. In an effort to save more money, some utilities are experimenting with selling electricity at a spot price per minute, allowing users with monitoring equipment to detect peak demand as it occurs, and shifting demand to save users and money utilities. Demand side management can be manual or automated and not limited to large industrial customers. In residential and small business applications, for example, the appliance control module can reduce the use of water heater, air conditioning, refrigerator, and other devices during this period by turning it off for some part of the peak demand time or by reducing the power they are drawing. Energy demand management involves more than reducing overall energy use or moving the load out of peak hours. This highly effective method of energy demand management involves encouraging power consumers to install more energy-efficient equipment. For example, many utilities provide rebates for the purchase of insulation, weatherstripping, and energy-saving appliances and bulbs. Some utilities subsidize the purchase of geothermal heat pumps by their customers, to reduce electricity demand during the summer by making air conditioning up to 70% more efficient, as well as to reduce winter power demand compared to conventional air-fired heat pumps or resistive heating. Companies with large factories and buildings can also install such products, but they can also purchase energy efficient industrial equipment, such as boilers, or use more efficient processes to produce products. Companies may get incentives such as low interest rebates or utility or government loans for the installation of energy efficient industrial equipment. Facilities may divert their request by requesting a third party to provide Storage of Energy as a Service (ESaaS).
Portability
This is the most successful field for energy storage technology today. Disposable and rechargeable batteries are everywhere, and provide power for devices with varying demands like digital watches and cars. Advances in battery technology are generally slow, however, with many advances in battery life perceived by consumers due to efficient power management rather than increased storage capacity. Portable consumer electronics have benefited greatly from the size and reduction of power associated with Moore's law. Unfortunately, Moore's law does not apply to transport people and goods; the underlying energy requirement for transport remains much higher than for information and entertainment applications. Battery capacity has become a problem because of growing pressure for alternatives to internal combustion engines in cars, trucks, buses, trains, boats, and airplanes. This use requires a much larger energy density (the amount of energy stored in a given volume or weight) than the current battery technology that can be produced. Liquid hydrocarbon fuels (such as petrol/gasoline and diesel), as well as alcohols (methanol, ethanol, and butanol) and lipids (straight vegetable oils, biodiesel) have much higher energy densities.
There is a synthetic pathway to use electricity to reduce carbon dioxide and water into liquid hydrocarbons or alcohol fuels. This path begins with electrolysis of water to produce hydrogen, and then reduces carbon dioxide with excess hydrogen in a variation of the reverse water gas shift reaction. Non-fossil sources of carbon dioxide include fermentation plants and sewage treatment plants. Converting electrical energy into carbon-based liquid fuels has the potential to provide portable energy storage that can be used by existing stock of motor vehicles and machine-driven equipment, without the difficulty of dealing with hydrogen or other exotic energy carriers. This synthetic pathway may draw attention in light of efforts to improve energy security in countries that depend on imported oil but have or can develop large sources of renewable or nuclear power, as well as to face possible future declines in the amount of oil available. to import.
Because the transport sector uses energy from petroleum is very inefficient, replacing petroleum with electricity for mobile energy will not require huge investment for many years.
Reliability
Almost all devices that operate on electricity are affected by the sudden removal of their electricity supply. Solutions such as UPS (uninterruptible power supply) or backup generators are available, but these are expensive. An efficient power storage method will allow the device to have an internal backup for power outages, and also reduce the impact of failure at generating stations. This example is currently available using fuel cells and stylish wheels.
See also
References
- Saving For The Day Without Wind by Sean Davies in The E & amp; T Magazine Vol 5 Issue 9 of www.IET.org
Further reading
- Baxter, Richard (2006). Energy Storage: A Nontechnical Guide . PennWell Books. ISBN 978-1-59370-027-0.
External links
- Nickel-cadmium batteries connected to a large grid
- Stasionary Energy Storage... Locks to Renewable Grid
- Electrical Storage Factbook
Source of the article : Wikipedia
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