Gravity battery

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A gravity battery is a type of electricity storage device that stores gravitational energy, the energy stored in an object resulting from a change in height due to gravity, also called potential energy. A gravity battery works by using excess energy (usually from sustainable sources) to raise a mass to generate gravitational potential energy, which is then lowered to convert potential energy into electricity through an electric generator. One form of a gravity battery is one that lowers a mass, such as a block of concrete, to generate electricity. The most common gravity battery is used in pumped-storage hydroelectricity, where water is pumped to higher elevations to store energy and released through water turbines to generate electricity. [1]

Contents

Development

The earliest form of a device that used gravity to power mechanical movement was the pendulum clock, invented in 1656 by Christiaan Huygens. The clock was powered by the force of gravity using an escapement mechanism, that made a pendulum move back and forth. Since then, gravity batteries have advanced into systems that can utilize the force due to gravity, and turn it into electricity for large scale energy storage.

The first gravity based pumped-storage hydroelectricity (PSH) system was developed in 1907 in Switzerland. In 1930, pumped-storage came to the United States by the Connecticut Electric and Power Company. As of 2019, the total world capacity for PSH is 168 GW (gigawatts). [2] The United States has 23 GW capacity from PSH, accounting for nearly 2% of the energy supply system and 95% of utility-scale energy storage in the US. Gravity based pumped-storage electricity is currently the largest form of grid energy storage in the world. [3] [4] [5] [6]

In 2012, Martin Riddiford and Jim Reeves developed the first functioning prototype of GravityLight, a small-scale gravity battery that is now commercially available in certain countries. [7]

Energy Vault, a Swiss company founded in 2017, stores electricity using a crane that raises and lowers blocks of concrete. [8] [9] [10] In late 2020, a prototype built in Arbedo-Castione used six cranes on a 110-meter-high tower to move 35-ton concrete blocks with a capacity of 80 megawatt hours. [11] [12]

Gravitricity, founded in 2011 by Peter Fraenkel, built a 15-meter 250-kilowatt gravity battery prototype near Edinburgh, Scotland that started trial operations and grid-connection in April 2021. [13] [14] [15]

Mechanisms and parts

Gravity batteries can have different designs and structures, but all gravity batteries use the same properties of physics to generate energy. Gravitational potential energy is the work required to move an object in the opposite direction of Earth's gravity, expressed by the equation

where U is gravitational potential energy, m is the mass of the object, g is the acceleration due to gravity (9.8 m/s2 on earth), and h is the height of the object. Using the work-energy principle, the total amount of energy generated can be expressed by the equation

where E is the total amount of energy generated and h1 and h2 represent the initial and final heights of an object. The change of energy directly correlates to the vertical displacement of a mass; the higher a mass is lifted, the more gravitational potential energy is stored. The change in energy also directly correlates to the mass of an object; the heavier the mass, the bigger the change in energy.

In a gravity battery, a mass is displaced, or lifted, to generate gravitational potential energy that is transformed into electricity. Gravity batteries store gravitational potential energy by lifting a mass to a certain height using a pump, crane, or motor. After the mass is lifted, it now stores a certain gravitational potential energy based on the mass of the object and how high it was lifted. The stored gravitational potential energy is then transferred into electricity. The mass is lowered to fall back to its original height, which causes a generator to spin and create electricity.

Types of gravity batteries

Large scale

Pumped-storage hydroelectricity (PSH) is the most widely used and highest-capacity form of grid-energy storage. In PSH, water is pumped from a lower reservoir to a higher reservoir, which can then be released through turbines to produce energy. An alternative PSH proposal uses a proprietary high-density liquid, 2+12 times denser than water, which requires a smaller head (elevation) and thus decreases the size and cost of the necessary infrastructure. [16] [17]

Energy-storage-by-rail is a concept where excess renewable energy is used to run heavy train cars uphill during times of low energy demand. The potential energy is released later by using regenerative braking as they roll downhill, acting as a gravity battery. [18] A utility-scale (50 MW) facility called GravityLine began construction in October 2020 by Advanced Rail Energy Storage, located at the Gamebird Pit gravel mine in the Pahrump Valley, Nevada, and is planned to deliver up to 15 minutes of service at full capacity. [19]

Lift Renewable Energy uses a form of gravity battery. To store energy, buoyant gas containers are pulled down into water by a winch, water is in effect lifted hundreds of meters. The cycle is then reversed and electricity is generated as the gas containers rise. Relatively little infrastructure is required, the batteries can be sited near major population centers, round trip efficiency is 85+%, and the system can be built at a GWh scale.[ citation needed ]

Lifted Weight Storage (LWS) technology uses surplus energy to mechanically lift solid weights vertically, typically on a pulley system. When extra energy is needed, the mass is lowered, and the pulley turns a generator. [20]

Energy Vault 60 meter prototype in Castione-Arbedo 2021 Energy Vault Test Tower 2021.jpg
Energy Vault 60 meter prototype in Castione-Arbedo 2021

EnergyVault is designing a LWS system using a tower built from 32-ton concrete blocks, stacked with 120-meter cranes. One commercial unit is expected to store 20 MWh of energy, or enough to power 2,000 Swiss homes a day. [9]

Gravitricity's LWS system in an underground shaft uses an electric winch to lift a 500-to-5000-tonne weight, which when lowered turns the winch motor as a generator. The system generates 10 MWh, enough to power 13,000 homes for two hours. The weight can also be dropped quickly for a small burst of power. [21] [ non-primary source needed ]

Small scale

GravityLight is a small gravity-powered light that operates by manually lifting a bag of rocks or sand up and then letting it fall by itself to generate energy. It is designed as an alternative for those who do not have access to electricity and typically rely on kerosene lamps, which are expensive, dangerous, and polluting. [7] [22] [23]

Economics and efficiency

Cost of gravity batteries varies by design.

Pumped storage hydropower costs $165/kWh to operate, with a levelized cost of storage (LCOS), of $0.17/kWh. [24] [25] The pumps and turbines of PSH systems operate at up to 90% efficiency. [26]

Gravitricity's 250 kW demonstrator is expected to be $1.25 million, promising a 50-year lifespan and efficiency of 80–90%.[ citation needed ] A 2018 comparative review of the proposition was favorable considering the extended lifespan and power-to-energy cost ratio. [27]

Gravity batteries can make solar and wind more viable as they can store the excess energy they make during peak hours and distribute it later when needed. [20] [28]

Environmental impacts

Gravity batteries are designed to be paired with renewable energy solutions whose sources (sunlight, wind, etc) are frequently variable and do not necessarily coincide with demand. It is hoped that they will have a better long term cost than chemical batteries, while having fewer environmental issues than other traditional storage solutions such as pumped-water storage. It is anticipated that gravity battery systems will be able to quickly provide power during peak consumption which may allow them to supplement or replace fossil fuel peaking power plants. Single weight systems are expected to be able to achieve full power generation in less than a second. [13]

Among low-carbon long-duration energy storage methods, pumped storage hydropower had the lowest current energy cost, though lithium-ion batteries are expected to overtake it in the future. [29] :38 Pumped storage hydropower and other long-duration storage methods are considered to have low environmental and security risks compared to battery technology, with the only limiting factor being geology. [29] :45–47

Gravity (chemical) battery

From 1870 to 1930, [30] the term "gravity battery" was used to describe a collection of popular battery types where gravity was used to keep the chemical constituents separate based on their respective densities. [31]

See also

Related Research Articles

<span class="mw-page-title-main">Hydropower</span> Power generation via movement of water

Hydropower, also known as water power, is the use of falling or fast-running water to produce electricity or to power machines. This is achieved by converting the gravitational potential or kinetic energy of a water source to produce power. Hydropower is a method of sustainable energy production. Hydropower is now used principally for hydroelectric power generation, and is also applied as one half of an energy storage system known as pumped-storage hydroelectricity.

<span class="mw-page-title-main">Potential energy</span> Energy held by an object because of its position relative to other objects

In physics, potential energy is the energy held by an object because of its position relative to other objects, stresses within itself, its electric charge, or other factors. The term potential energy was introduced by the 19th-century Scottish engineer and physicist William Rankine, although it has links to the ancient Greek philosopher Aristotle's concept of potentiality.

<span class="mw-page-title-main">Energy storage</span> Captured energy for later usage

Energy storage is the capture of energy produced at one time for use at a later time to reduce imbalances between energy demand and energy production. A device that stores energy is generally called an accumulator or battery. Energy comes in multiple forms including radiation, chemical, gravitational potential, electrical potential, electricity, elevated temperature, latent heat and kinetic. Energy storage involves converting energy from forms that are difficult to store to more conveniently or economically storable forms.

<span class="mw-page-title-main">Power station</span> Facility generating electric power

A power station, also referred to as a power plant and sometimes generating station or generating plant, is an industrial facility for the generation of electric power. Power stations are generally connected to an electrical grid.

<span class="mw-page-title-main">Distributed generation</span> Decentralised electricity generation

Distributed generation, also distributed energy, on-site generation (OSG), or district/decentralized energy, is electrical generation and storage performed by a variety of small, grid-connected or distribution system-connected devices referred to as distributed energy resources (DER).

<span class="mw-page-title-main">Pumped-storage hydroelectricity</span> Electric energy storage system

Pumped-storage hydroelectricity (PSH), or pumped hydroelectric energy storage (PHES), is a type of hydroelectric energy storage used by electric power systems for load balancing. The method stores energy in the form of gravitational potential energy of water, pumped from a lower elevation reservoir to a higher elevation. Low-cost surplus off-peak electric power is typically used to run the pumps. During periods of high electrical demand, the stored water is released through turbines to produce electric power. Although the losses of the pumping process make the plant a net consumer of energy overall, the system increases revenue by selling more electricity during periods of peak demand, when electricity prices are highest. If the upper lake collects significant rainfall or is fed by a river then the plant may be a net energy producer in the manner of a traditional hydroelectric plant.

<span class="mw-page-title-main">Hydroelectricity</span> Electricity generated by hydropower

Hydroelectricity, or hydroelectric power, is electricity generated from hydropower. Hydropower supplies one sixth of the world's electricity, almost 4,500 TWh in 2020, which is more than all other renewable sources combined and also more than nuclear power. Hydropower can provide large amounts of low-carbon electricity on demand, making it a key element for creating secure and clean electricity supply systems. A hydroelectric power station that has a dam and reservoir is a flexible source, since the amount of electricity produced can be increased or decreased in seconds or minutes in response to varying electricity demand. Once a hydroelectric complex is constructed, it produces no direct waste, and almost always emits considerably less greenhouse gas than fossil fuel-powered energy plants. However, when constructed in lowland rainforest areas, where part of the forest is inundated, substantial amounts of greenhouse gases may be emitted.

<span class="mw-page-title-main">Electricity sector in India</span> Power generation and distribution

India is the third largest producer of electricity in the world. During the fiscal year (FY) 2022–23, the total electricity generation in the country was 1,844 TWh, of which 1,618 TWh was generated by utilities.

<span class="mw-page-title-main">Grid energy storage</span> Large scale electricity supply management

Grid energy storage is a collection of methods used for energy storage on a large scale within an electrical power grid. Electrical energy is stored during times when electricity is plentiful and inexpensive or when demand is low, and later returned to the grid when demand is high, and electricity prices tend to be higher.

The following outline is provided as an overview of and topical guide to energy:

<span class="mw-page-title-main">Peaking power plant</span> Reserved for high demand times

Peaking power plants, also known as peaker plants, and occasionally just "peakers", are power plants that generally run only when there is a high demand, known as peak demand, for electricity. Because they supply power only occasionally, the power supplied commands a much higher price per kilowatt hour than base load power. Peak load power plants are dispatched in combination with base load power plants, which supply a dependable and consistent amount of electricity, to meet the minimum demand.

<span class="mw-page-title-main">Micro hydro</span> Hydroelectric power generation of 5 to 100 kW of electricity

Micro hydro is a type of hydroelectric power that typically produces from 5 kW to 100 kW of electricity using the natural flow of water. Installations below 5 kW are called pico hydro. These installations can provide power to an isolated home or small community, or are sometimes connected to electric power networks, particularly where net metering is offered. There are many of these installations around the world, particularly in developing nations as they can provide an economical source of energy without the purchase of fuel. Micro hydro systems complement solar PV power systems because in many areas water flow, and thus available hydro power, is highest in the winter when solar energy is at a minimum. Micro hydro is frequently accomplished with a pelton wheel for high head, low flow water supply. The installation is often just a small dammed pool, at the top of a waterfall, with several hundred feet of pipe leading to a small generator housing. In low head sites, generally water wheels and Archimedes' screws are used.

<span class="mw-page-title-main">Off-the-grid</span> Not being connected to public utilities

Off-the-grid or off-grid is a characteristic of buildings and a lifestyle designed in an independent manner without reliance on one or more public utilities. The term "off-the-grid" traditionally refers to not being connected to the electrical grid, but can also include other utilities like water, gas, and sewer systems, and can scale from residential homes to small communities. Off-the-grid living allows for buildings and people to be self-sufficient, which is advantageous in isolated locations where normal utilities cannot reach and is attractive to those who want to reduce environmental impact and cost of living. Generally, an off-grid building must be able to supply energy and potable water for itself, as well as manage food, waste and wastewater.

<span class="mw-page-title-main">Hybrid power</span> Combinations between different technologies to generate electric power

Hybrid power are combinations between different technologies to produce power.

<span class="mw-page-title-main">Solar power</span> Conversion of energy from sunlight into electricity

Solar power, also known as solar electricity, is the conversion of energy from sunlight into electricity, either directly using photovoltaics (PV) or indirectly using concentrated solar power. Solar panels use the photovoltaic effect to convert light into an electric current. Concentrated solar power systems use lenses or mirrors and solar tracking systems to focus a large area of sunlight to a hot spot, often to drive a steam turbine.

<span class="mw-page-title-main">Hydroelectric power in India</span>

India is 5th globally for installed hydroelectric power capacity. As of 31 March 2020, India's installed utility-scale hydroelectric capacity was 46,000 MW, or 12.3% of its total utility power generation capacity. Additional smaller hydroelectric power units with a total capacity of 4,683 MW have been installed. India's hydroelectric power potential is estimated at 148,700 MW at 60% load factor. In the fiscal year 2019–20, the total hydroelectric power generated in India was 156 TWh with an average capacity factor of 38.71%.

<span class="mw-page-title-main">Variable renewable energy</span> Class of renewable energy sources

Variable renewable energy (VRE) or intermittent renewable energy sources (IRES) are renewable energy sources that are not dispatchable due to their fluctuating nature, such as wind power and solar power, as opposed to controllable renewable energy sources, such as dammed hydroelectricity or biomass, or relatively constant sources, such as geothermal power.

<span class="mw-page-title-main">Hydroelectricity in the United Kingdom</span>

As of 2018, hydroelectric power stations in the United Kingdom accounted for 1.87 GW of installed electrical generating capacity, being 2.2% of the UK's total generating capacity and 4.2% of UK's renewable energy generating capacity. This includes four conventional hydroelectric power stations and run-of-river schemes for which annual electricity production is approximately 5,000 GWh, being about 1.3% of the UK's total electricity production. There are also four pumped-storage hydroelectric power stations providing a further 2.8 GW of installed electrical generating capacity, and contributing up to 4,075 GWh of peak demand electricity annually.

<span class="mw-page-title-main">Tesla Megapack</span> Large-scale battery energy storage product manufactured by Tesla Energy

The Tesla Megapack is a large-scale rechargeable lithium-ion battery stationary energy storage product, intended for use at battery storage power stations, manufactured by Tesla Energy, the energy subsidiary of Tesla, Inc.

<span class="mw-page-title-main">Energy Vault</span>

Energy Vault is a Swiss-based, global energy storage company specializing in gravity and kinetic energy based, long-duration energy storage products. Energy Vault’s primary product is a gravity battery using a multi-headed crane to store energy by stacking heavy blocks made of composite material into a tower, capturing potential energy in the elevation gain of the blocks. When demand for electricity is high, the crane lowers these blocks to the ground, with the motors functioning as generators and delivering electricity to the grid.

References

  1. Chaturvedi, D.K.; Yadav, Shubham; Srivastava, Tamanna; Kumari, Tanvi (July 27, 2020). "Electricity storage system: A Gravity Battery". 2020 Fourth World Conference on Smart Trends in Systems, Security and Sustainability (WorldS4). London, United Kingdom: IEEE. pp. 412–416. doi:10.1109/WorldS450073.2020.9210321. ISBN   978-1-7281-6823-4. S2CID   222137266.
  2. "International - U.S. Energy Information Administration". Energy Information Administration. Retrieved October 30, 2020.
  3. "Most pumped storage electricity generators in the U.S. were built in the 1970s - Today in Energy - U.S. Energy Information Administration (EIA)". www.eia.gov. Retrieved November 16, 2020.
  4. "Pumped Hydropower". Energy Storage Association. Retrieved November 16, 2020.
  5. "Pumped-Storage Hydropower". Energy.gov. Retrieved November 16, 2020.
  6. "2018 Pumped Storage Report" (PDF). National Hydropower Association. January 1, 2018. Retrieved November 3, 2020.
  7. 1 2 "When Gravity Equals Light". July 3, 2018. Retrieved October 28, 2020.
  8. Spector, Julian (April 3, 2020). "The 5 Most Promising Long-Duration Storage Technologies Left Standing". Greentech Media. Retrieved October 28, 2020.
  9. 1 2 "EnergyVault". EnergyVault: Enabling a Renewable World. EnergyVault. 2020.
  10. Kelly-Detwiler, Peter (October 14, 2019). "Energy Vault Receives $110 Million From SoftBank For Gravity-Assisted Power Storage". Forbes. Retrieved October 30, 2020.
  11. "Revolutionary idea to store green power for the grid". swissinfo.ch. January 3, 2020.
  12. "What is the 'gravity energy storage system' that is attracting attention as a low-cost energy storage means?". gigazine.net. January 7, 2021.
  13. 1 2 Moore, Samuel K. (January 5, 2021). "Gravity Energy Storage Will Show Its Potential in 2021". IEEE Spectrum. Retrieved February 9, 2021.
  14. "Gravitricity celebrates success of 250kW energy storage demonstrator". Solar Power Portal.
  15. "Gravitricity battery generates first power at Edinburgh site". BBC. April 21, 2021.
  16. Ambrose, Jillian (February 8, 2021). "Powering up: UK hills could be used as energy 'batteries'". the Guardian .
  17. "RheEnergise Home Page". www.rheenergise.com. Retrieved February 8, 2021.
  18. Massey, Nathanael. "Energy Storage Hits the Rails Out West". Scientific American . Archived from the original on December 4, 2017. Retrieved December 31, 2017.
  19. Hebrock, Robin (October 16, 2020). "Energy storage project breaks ground in Pahrump". Pahrump Valley Times. Retrieved March 18, 2021.
  20. 1 2 says, Len Gardiner (February 20, 2020). "What Are Gravity Batteries?". TheGreenAge. Retrieved October 29, 2020.
  21. "Fast, long-life energy storage". Gravitricity. Retrieved October 28, 2020.
  22. "GravityLight - light from the lift of a weight". deciwatt.global. Retrieved October 29, 2020.
  23. "GravityLight". Deciwatt. Retrieved November 1, 2020.
  24. "Energy Storage Technology and Cost Characterization Report" (PDF). U.S. Department of Energy. July 1, 2019. Retrieved November 1, 2020.
  25. "Pumped-hydro energy storage – cost estimates for a feasible system". Brave New Climate. April 5, 2010. Retrieved November 16, 2020.
  26. "Pump Up the Storage | Do the Math". November 15, 2011. Retrieved November 16, 2020.
  27. O'Neill, Neasan (April 23, 2018). "Is gravity and old mineshafts the next breakthrough in energy storage?". Imperial College News. Imperial College London.
  28. Ong, Sandy (December 6, 2019). "Mix Mountains and Gravity for Long-Term Energy Storage". IEEE Spectrum. Retrieved November 16, 2020.
  29. 1 2 Mann, Margaret; Putsche, Vicky; Shrager, Benjamin (February 24, 2022). Grid Energy Storage: Supply Chain Deep Assessment (PDF) (Report). United States Department of Energy. Retrieved August 6, 2022.
  30. "Google Ngram search for popularity of the term Gravity Battery". Archived from the original on April 8, 2020.
  31. "Gravity Batteries by Robert Murray-Smith". YouTube .