Energy storage

From ScienceForSustainability
Jump to navigation Jump to search

In a grid connecting electricity generators to consumers the amount of electricity generated must exactly match the amount demanded at every instant or voltage (and frequency) will rise above or fall below their ideal levels. Excess voltage can damage equipment, and if voltage is too low some appliances will not work. If supply falls too much below demand grid operators will have to disconnect - black-out - areas to prevent blackout of the whole grid. If the whole grid blacks out, restoring power requires a complex procedure of bringing power stations back into synchronism with each other - each has to run at exactly the same speed (frequency) - whilst re-connecting areas only at a rate that generators can supply them.

In a grid supplying many consumers, unpredictable short-term fluctuations in demand are inevitable: people turn lights, heaters, kettles and cookers on and off as they need. On a large grid connecting thousands or millions of consumers such random short-term fluctuations tend to even out, but aggregate into more slowly varying and predictable changes: peaks in the morning when people get up and in the evening when they return from work and cook, peaks during breaks in popular TV broadcasts, fluctuations in heating demand in response to changing weather conditions etc. Over a period of months demand varies as more power is demanded for winter heating in cold climates, and/or summer air conditioning in warmer regions.

In grids comprising mostly thermal (coal, gas and nuclear) and hydroelectric power plants, short-term random fluctuations are evened out by the flywheel effect of the massive spinning alternators of these plants. This 'spinning reserve' can make up or take up the difference between power generation and demand for a few seconds, with relatively modest, acceptable changes in voltage and frequency. Over longer periods the grid operators have to increase or decrease supply to match demand. Hydro can respond in a matter of seconds, gas and coal more slowly. Nuclear can respond more slowly still, and is usually run at a constant rate with no variation in output.

The other way to balance supply with demand is to vary demand, where possible. This has for many decades been done to even out day- and night-time demands by offering lower off-peak tariffs which consumers can take advantage of by running water heaters, storage heaters, washing machines etc when electricity is more plentiful. Some heavy industrial consumers of electricity also participate in similar schemes. This sort of arrangement particularly suits grids with large amounts of nuclear and/or wind generation. With modern electronics built into smarter appliances there is the potential to increase the responsiveness of electricity demands to supply e.g. freezers can draw more power and run colder during times of surplus and reduce their consumption during times of high demand.

Intermittent renewables - wind, solar PV, wave and tide - present challenges to grid operation, partly because grid operators have to cope with the uncontrollable variability to supply as well as variations in demand, and partly because they reduce the amount of spinning reserve in the system.

Compensating for variations in intermittent renewables' supply is accomplished by maintaining a reserve of fossil fuelled power stations - running at below capacity and able to increase or decrease power to complement the renewables' output. This limits the degree of decarbonsisation possible since even the biggest offshore wind turbines produce energy only about half the time on average, so fossil fuels have to supply the remainder. Also when fossil fuelled power stations are running below full capacity they're less efficient than when they run flat out, and their carbon emissions are correspondingly higher. To achieve deep decarbonisation with intermittent renewables requires either a means of storing energy when the wind is blowing, sun shining etc, or massive transmission lines over inter-continental distances to ship energy from areas where there is wind/sun etc to those where there is none. Either of these solutions requires not only huge amounts of generation capacity but also orders of magnitude greater resources than currently exist, and have problems of cost, availability of raw materials, and/or political issues.

The problem of spinning reserve is more easily tackled. Huge battery installations such as Tesla's Big South Australian Battery are capable of responding to demands to store or supply power very quickly, giving short-term stability to the grid and responding quickly to sudden changes until slower-responding plants can take over. Many of these frequency service installations are being added to grids where intermittent non-spinning supplies make a significant proportion of capacity.

See also: Chemical fuels


Fluctuations and Storage David MacKay; Sustainable Energy Without The Hot Air

List of energy storage projects Wikipedia

Energy Storage Association

UK Energy Storage Network

Energy Storage News

News, analysis and opinion on energy storage technologies

Distributed Energy Storage Revenue To Exceed $16.5 Billion By 2024 Joshua S Hill; CleanTechnica; 13 Jan 2015

Is large-scale energy storage dead? Roger Andrews; Energy Matters; 8 Apr 2016

Many countries have committed to filling large percentages of their future electricity demand with intermittent renewable energy, and to do so they will need long-term energy storage in the terawatt-hours range. But the modules they are now installing store only megawatt-hours of energy. Why are they doing this? This post concludes that they are either conveniently ignoring the long-term energy storage problem or are unaware of its magnitude and the near-impossibility of solving it.

Green Energy Doesn’t Work Without Energy Storage That Doesn’t Exist Yet Andrew Follett; Daily Caller; 29 May 2016

from Investment in energy storage vital UEA press release about paper:
The value of arbitrage for energy storage: Evidence from European electricity markets Dimitrios Zafirakis, Konstantinos J. Chalvatzis, Giovanni Baiocchi, Georgios Daskalakis; Applied Energy; 27 May 2016

From liquid air to supercapacitors, energy storage is finally poised for a breakthrough Damian Carrington; The Guardian; 4 Feb 2016

Smarter Network Storage UK Power Networks

We are undertaking trials to improve understanding of the economics of electrical energy storage. The learning gained will help improve cost effectiveness and provide a more sustainable, efficient and flexible way to reinforce networks.

Grid-Scale Storage of Renewable Energy: The Impossible Dream Euan Mearns; Energy Matters; 20 Nov 2017

The utopian ambition for variable renewable energy is to convert it into uniform firm capacity using energy storage. Here we present an analysis of actual UK wind and solar generation for the whole of 2016 at 30 minute resolution and calculate the grid-scale storage requirement. In order to deliver 4.6 GW uniform and firm RE supply throughout the year, from 26 GW of installed capacity, requires 1.8 TWh of storage. We show that this is both thermodynamically and economically implausible to implement with current technology.
Considers pumped hydro, battery and chemical conversion & storage

Battery storage* in perspective – solving 1% of the problem Roger Andrews; Energy Matters; 19 Feb 2018

The energy world is fixated on the “huge” amounts of battery storage presently being installed to back up slowly-increasing levels of intermittent renewables generation. The feeling seems to be that as soon as enough batteries are installed to take care of daily supply/demand imbalances we will no longer need conventional dispatchable energy – solar + wind + storage will be able to do it all. Here I take another look at the realities of the situation using what I hope are some telling visual examples of what battery storage will actually do for us. As discussed in previous posts it will get us no closer to the vision of a 100% renewables-powered world than we are now.
*Note: “Battery storage” covers all storage technologies currently being considered, including thermal, compressed air, pumped hydro etc. Batteries are, however, the flavor of the moment and are expected to capture the largest share of the future energy storage market.


DOE Global Energy Storage Database

The DOE Global Energy Storage Database provides free, up-to-date information on grid-connected energy storage projects and relevant state and federal policies.
All information is vetted through a third-party verification process. All data can be exported to Excel or PDF. Our hope is that this site will contribute to the rapid development and deployment of energy storage technologies.

Energy Storage in the UK - An Overview Renewable Energy Association; Winter 2015-16

Energy Storage Procurement in California - APR2014 24 Jul 2014

SR15 Chapter 4 IPCC Energy Storage
The growth in electricity storage for renewables has been around Grid Flexibility Resources (GFR) that
would enable several places to source more than half their power from non-hydro renewables (Komarnicki,
2016). Ten types of GFRs within smart grids have been developed largely since AR5 as renewables have
tested grid stability (Blaabjerg et al., 2004; IRENA, 2013; IEA, 2017d; Majzoobi and Khodaei, 2017) though
demonstrations of how to do this without hydro or natural gas-based power back-up are still needed. Pumped
hydro comprised 150 GW of storage capacity in 2016, and grid-connected battery storage just 1.7 GW, but
the latter grew between 2015 to 2016 by 50% (REN21, 2012). Battery storage has been the main growth
feature in energy storage since AR5 (Breyer et al., 2017). This appears to the result of significant cost
reductions due to mass production for Electric Vehicles (EVs) (Nykvist and Nilsson, 2015; Dhar et al.,
2017). Although costs and technical maturity look increasingly positive, the feasibility of battery storage is
challenged by concerns over the availability of resources and the environmental impacts of its production
(Peters et al., 2017). Lithium, a common element in the earth’s crust, does not appear to be restricted and
large increases in production have happened in recent years with eight new mines in Western Australia
where most lithium is produced (GWA, 2016). Emerging battery technologies may provide greater
efficiency and recharge rates (Belmonte et al., 2016) but remain significantly more expensive due to speed
and scale issues compared to lithium ion batteries (Dhar et al., 2017; IRENA, 2017a).
Research and demonstration of energy storage in the form of thermal and chemical systems continues, but
large scale commercial systems are rare (Pardo et al., 2014). Renewably derived synthetic liquid (like
methanol and ammonia) and gas (like methane and hydrogen) are increasingly being seen as a feasible
storage options for renewable energy (producing fuel for use in industry during times when solar and wind
are abundant) (Bruce et al., 2010; Jiang et al., 2010; Ezeji, 2017) but, in the case of carbonaceous storage
media, would need a renewable source of carbon to make a positive contribution to GHG reduction (von der
Assen et al., 2013; Abanades et al., 2017) (see also Section The use of electric vehicles as a form of
storage has been modelled and evaluated as an opportunity, and demonstrations are emerging (Dhar et al.,
2017; Green and Newman, 2017a), but challenges to upscaling remain.


Power to Gas Wikipedia

Science for Energy Scenarios

3rd Science and Energy Seminar at Ecole de Physique des Houches, March 6th-11th 2016
presentations on EROI, power-gas-power, intermmittency, grids, etc
discusses losses in conversion to and storage of H2, CH4 (circa 60% efficiency for H2, 39% for CH4)


Battery Storage Needed to Expand Renewable Energy Umair Irfan; Scientific American; 13 Feb 2015

The U.S. Department of Energy is exploring energy storage strategies to accelerate the use of wind and solar power

UC Irvine invents nanowire battery material with off-the-charts charging capacity Next Big Future; 20 Apr 2016

University of California, Irvine researchers have invented nanowire-based battery material that can be recharged hundreds of thousands of times, moving us closer to a battery that would never require replacement. The breakthrough work could lead to commercial batteries with greatly lengthened lifespans for computers, smartphones, appliances, cars and spacecraft. Scientists have long sought to use nanowires in batteries. Thousands of times thinner than a human hair, they’re highly conductive and feature a large surface area for the storage and transfer of electrons. However, these filaments are extremely fragile and don’t hold up well to repeated discharging and recharging, or cycling. In a typical lithium-ion battery, they expand and grow brittle, which leads to cracking. UCI researchers have solved this problem by coating a gold nanowire in a manganese dioxide shell and encasing the assembly in an electrolyte made of a Plexiglas-like gel. The combination is reliable and resistant to failure. The testing electrode was cycled up to 200,000 times over three months without detecting any loss of capacity or power and without fracturing any nanowires.

Lithium-Ion Will Be Tough To Beat, Says Argonne Battery Whiz Jeff McMahon; Forbes; 26 May 2016

People who are working on next-generation batteries often put lithium-ion down, saying the current technology is too costly, too flammable, or too limited to meet the clean energy and clean transportation demands of the future. But four years into a five-year effort to develop a better battery at Argonne National Laboratory, one Argonne engineer concedes Li-ion will be tough to beat in the marketplace.

UCI Student Accidently Creates A Rechargeable Battery That Lasts 400 Years Tod Perry; Good; 13 Sep 2016

.... recent discovery at the University of California, Irvine by doctoral student Mya Le Thai. After playing around in the lab she made a discovery that could lead to a rechargeable battery that lasts up to 400 years. ... Thai coated a set of gold nanowires in manganese dioxide and a Plexiglas-like electrolyte gel. ... nanobattery developed at UCI made it though 200,000 cycles in three months

The $2.5 trillion reason we can’t rely on batteries to clean up the grid James Temple; MIT Technology Review; 27 Jul 2018

Fluctuating solar and wind power require lots of energy storage, and lithium-ion batteries seem like the obvious choice—but they are far too expensive to play a major role.



AES Constructing Largest Battery-Based Energy Storage Array in United Kingdom AES Energy Storage

Carrickfergus, Northern Ireland, 20 July 2015 – AES announced today that it has begun construction of its first advanced, battery-based energy storage facility in the United Kingdom. The Kilroot AdvancionTM Energy Storage Array will provide 10 MW of interconnected energy storage, equivalent to 20 MW of flexible resource. The array is expected to begin operations by the end of 2015.

Gigha - redT - redox

Utility Scale Storage for Gigha redT energy

Thanks to a £3.6m funding award from the UK Department for Energy and Climate Change (DECC), redT are currently working on the demonstration and pre-commercialisation of a 1.68MWh version of its grid scale flow battery. The energy storage system is being designed for the remote Scottish Isle of Gigha and will be integrated with the island’s wind farm and deployed with the help of project partners; Scottish and Southern Energy (SSE), EA Technology Ltd., Community Energy Scotland (CES) and Gigha Green Power Ltd. (GGPL). The MWh scale vanadium battery will provide much needed energy storage for a location which has limited grid connection via an ageing subsea cable.
The wind farm on Gigha was one of the first community owned grid connected wind farms in Scotland and currently consists of three wind turbines with a combined capacity of 775kW. A fourth turbine of 330kW is being installed, however it will need to operate at an extreme 0.85 power factor to overcome voltage rises and is also constrained to 225kW. Over the 25 year life span of the turbine, this constraint will amount to a loss of 3GWh at a value of around £300,000 and approximately 1.5kt CO2. Furthermore, under the current passive network operating arrangements, the constraint also prevents additional renewable generation capacity from being added to the island, including wind turbines, photo-voltaic panels and tidal stream generators.
The MW Scale Energy Storage system to be implemented on Gigha will address the constraint, allowing for a 20% minimum increase in wind energy generation, which will provide additional income for the island.
In addition to creating revenue from removing constraints from the wind turbine, the implementation of the redT Energy Storage system could potentially enable:
  • The sale of wind energy to the market during peak times and price spikes
  • Local backup power supply in the event of network faults
  • Further generation connections downstream of the Energy Storage System (ESS)
  • Replacement of the fish-farm diesel generators with an Uninterruptible Power Supply (UPS) derived from the ESS - creating environmental benefits and reducing fuel costs.
  • Electricity Trading (arbitrage)
  • The Dispatch of network services (voltage control, load-shifting for assets)
  • The Dispatch of balancing and capacity services such as Frequency Response and Short-Term Operating Reserve (STOR) through an aggregator
redT Vanadium Redox Flow Batteries were chosen for the project because of their ability to balance variable generation from renewable sources and its cost effective time shifting. The new VRFB utility scale technology will meet the need for efficient distributed storage, combined with the ability to respond instantly to demand, dispatching energy over a 12-hour duration when required. The all-Vanadium batteries contain no heavy metals, use non-flammable materials and the electrolyte is completely recyclable. This 2.5-year project aims to demonstrate the utility scale system in a demanding UK application and to develop the technology further towards the goal of full scale commercial manufacture.

Frequency stabilisation

UK’s fastest energy storage system launches The Engineer; 17 Mar 2016

A £4m battery-based energy storage facility has launched today at Willenhall substation near Wolverhampton as part of research led by Sheffield University. The system, which the university said is the UK’s fastest as well as one of its largest, is capable of responding to National Grid demands in 4/10ths of a second. It is also the first in the country to use a lithium titanate battery. Toshiba’s 2MW battery is made up of 21,120 cells and can supply energy to 3,000 homes for 20 minutes. It was chosen for its rapid charge and discharge times, its long lifetime and its safety.
UK National Grid Enhanced Frequency Response

How Britain will keep the lights on Emily Gosden, energy editor ; Daily Telegraph; 26 Aug 2016

Eight new battery storage projects are to be built around the UK after winning contracts worth £66m to help National Grid keep power supplies stable as more wind and solar farm are built. EDF Energy, E.On and Vattenfall were among the successful companies chosen to build new lithium ion batteries with a combined capacity of 200 megawatts (MW), under a new scheme to help Grid balance supply and demand within seconds.

Britain Is About to Take a Great (Battery) Leap Forward Jessica Shankleman; Bloomberg Technology; 25 Aug 2016

Grid-scale electricity storage will move closer to commercial reality on Friday when the U.K.’s grid operator offers contracts to companies to help balance the network, a key measure needed to help balance increasing supply from renewables. National Grid Plc will announce the winners of a bidding round for as much as 200 megawatts of storage capacity, which is about the size of a small power plant. It’s likely to be the storage industry’s biggest award this year in global market expected to install $5.1 billion of equipment in 2020, according to Bloomberg New Energy Finance. Storage plays a key role in the greening of utilities’ networks by allowing grid managers to handle higher volumes of intermittent power from the wind and sun.
Any winning bidder of National Grid’s tender must be able to supply power within 1 second and deliver 100 percent of the capacity it offered for at least 15 minutes.
200MW * 15m = 50MWh



UK 2 and 3kWh batteries in wall-hung box


Vaca system / CAISO / Sodium-Sulphur batteries

CAISO Battery Storage Trial Todd "Ike" Kiefer; Transmission and Distribution World / The Grid Optimization Blog; 21 Nov 2016

Despite all the hype and giga-promises, there has yet been no breakthrough in electricity storage technology that delivers all the requisite features of high energy density, high power, long life, high roundtrip efficiency, safe handling, and competitive cost. Batteries are still a long way from being a substitute for fossil fuel power plants or any other actual power generators because of physical and economic limits of current technology.


Powervault tech specs

Why Tesla's Powerwall Is Just Another Toy For Rich Green People Forbes

Tesla Discontinues 10-Kilowatt-Hour Powerwall Home Battery Julia Pyper; Green Tech Media; 18 Mar 2016

Tesla has quietly removed all references to its 10-kilowatt-hour residential battery from the Powerwall website, as well as the company’s press kit. The company's smaller battery designed for daily cycling is all that remains.

Tesla Wins Massive Contract to Help Power the California Grid Tim Randall; Bloomberg; 15 Sep 2016

Tesla Motors Inc. will supply 20 megawatts (80 megawatt-hours) of energy storage to Southern California Edison as part of a wider effort to prevent blackouts by replacing fossil-fuel electricity generation with lithium-ion batteries.

South Australia

Elon Musk wins bet, finishing massive battery installation in 100 days Timothy B. Lee; Ars Technica; 23 Nov 2017

Tesla has completed construction of a massive 100-megawatt, 129-MWh battery installation in South Australia. The new facility boasts the largest megawatt rating for any grid-connected battery installation in the world.

Tesla Fulfilled Its 100-Day Australia Battery Bet. What’s That Mean for the Industry? JULIAN SPECTOR; GTM; 27 Nov 2017

Musk later noted that the cost of losing that bet would have been around $50 million, Business Insider reports.

Elon Musk just won a $50 million bet for building the world's largest lithium-ion battery in 100 days Simon Thomsen; Business Insider Australia; 23 Nov 2017

Musk said that if he failed to meet the deadline, the project would have cost him "$50 million or more."

performance / FCAS

Tesla big battery outsmarts lumbering coal units after Loy Yang trips Giles Parkinson; Renew Economy; 19 Dec 2017

The Tesla big battery is having a big impact on Australia’s electricity market, far beyond the South Australia grid where it was expected to time shift a small amount of wind energy and provide network services and emergency back-up in case of a major problem.
Last Thursday, one of the biggest coal units in Australia, Loy Yang A 3, tripped without warning at 1.59am, with the sudden loss of 560MW and causing a slump in frequency on the network.
What happened next has stunned electricity industry insiders and given food for thought over the near to medium term future of the grid, such was the rapid response of the Tesla big battery to an event that happened nearly 1,000km away.
Even before the Loy Yang A unit had finished tripping, the 100MW/129MWh had responded, injecting 7.3MW into the network to help arrest a slump in frequency that had fallen below 49.80Hertz.
Data from AEMO (and gathered above by Dylan McConnell from the Climate and Energy College) shows that the Tesla big battery responded four seconds ahead of the generator contracted at that time to provide FCAS (frequency control and ancillary services), the Gladstone coal generator in Queensland.
But in reality, the response from the Tesla big battery was even quicker than that – in milliseconds – but too fast for the AEMO data to record.
Importantly, by the time that the contracted Gladstone coal unit had gotten out of bed and put its socks on so it can inject more into the grid – it is paid to respond in six seconds – the fall in frequency had already been arrested and was being reversed.
Gladstone injected more than Tesla did back into the grid, and took the frequency back up to its normal levels of 50Hz, but by then Tesla had already put its gun back in its holster and had wandered into the bar for a glass of milk.


Energy Storage Technologies Energy Storage Association

Batteries Not Excluded Simon Parkin; How We Get To Next; 11 Feb 2016

The supercomputer in your pocket and your next car rely on them — so what will we do if we run out of lithium?
battery history, chemistry, sustainability

US agency reaches 'holy grail' of battery storage sought by Elon Musk and Gates ARPA-E

Uncle Sam's boffins stumble upon battery storage holy grail ARPA-E

Spanish company Graphenano claims Graphene Polymer batteries with triple the energy density of lithium ion and commercialization by end of 2016


Lithium Ion batteries wikipedia

Ten years left to redesign lithium-ion batteries Kostiantyn Turcheniuk, Dmitry Bondarev, Vinod Singhal, Gleb Yushin; Nature Comment ; 25 July 2018

Reserves of cobalt and nickel used in electric-vehicle cells will not meet future demand. Refocus research to find new electrodes based on common elements such as iron and silicon, urge Kostiantyn Turcheniuk and colleagues.

Flow batteries

Flow battery Wikipedia

Redox Flow Batteries Energy Storage Association

Redox flow batteries (RFB) represent one class of electrochemical energy storage devices. The name “redox” refers to chemical reduction and oxidation reactions employed in the RFB to store energy in liquid electrolyte solutions which flow through a battery of electrochemical cells during charge and discharge.

Highly efficient grid-scale electricity storage at fifth of cost - researchers modify hybrid flow battery electrodes with nanomaterials University of Warwick; 22 Jan 2021

Researchers in WMG at the University of Warwick, in collaboration with Imperial College London, have found a way to enhance hybrid flow batteries and their commercial use. The new approach can store electricity in these batteries for very long durations for about a fifth the price of current technologies, with minimal location restraints and zero emissions.

The researchers enhanced three hybrid flow cells using nitrogen doped graphene (exposed to nitrogen plasma) in a binder-free electrophoresis technique (EPD)

Wind and solar power are increasingly popular sources for renewable energy. Unfortunately, intermittency issues keep them from connecting widely to the National grid. One potential solution to this problem involves in the deployment of long-duration battery technology, such as the redox flow battery. Despite its great promise the current costs of this system are a key determining factor to real-world adoption. An affordable grid battery should cost £75/kWh, according to the US Department of Energy. Lithium-ion batteries, which lead the charge for grid storage, cost about £130/kWh.

Now WMG researchers have found a way of enhancing hybrid flow batteries or regenerative fuel cell (RFC) technology that could store electricity for very long durations for about one-fifth the cost of current storage technologies, with flexibility in siting and with minimal environmental impact. The technology combines carbon-based electrodes with economically sourced electrolytes, (manganese or sulphur, which are abundant chemicals in the planet) by means of a simple and yet highly effective electrophoretic deposition of nano-carbon additives (nitrogen-doped graphene) that enhance the electrode durability and performance significantly in highly acidic or alkaline environments.

The researchers have published their findings in a paper entitled, ‘Hybrid Redox Flow Cells with Enhanced Electrochemical Performance via Binderless and Electrophoretically Deposited Nitrogen-Doped Graphene on Carbon Paper Electrodes’ in the December 2020 edition of the journal ACS Applied Materials & Interfaces.

Dr Barun Chakrabarti, a Research Fellow in WMG at the University of Warwick and one of the lead authors on the paper said:

“This EPD technique is not only simple but also improves the efficiencies of three different economical hybrid flow batteries thereby increasing their potential for widespread commercial adoption for grid-scale energy storage.”

The hybrid flow battery’s total chemical cost is about 1/30th the cost of competing batteries, such as lithium-ion systems. Scaled-up technologies may be used to store electricity from wind or solar power, for multiple days to entire seasons, for about £15 to £20 per kilowatt hour. These batteries are also extremely useful for grid-scale load levelling applications as their design is very flexible due to their unique feature of sizing their power independently of their energy.

The energy density of a hybrid flow battery, especially the polysulphide/air system (S-Air), is 500 times higher than pumped hydroelectric storage. It is also so much more compact and can be placed near any renewable generation.

Vanadium-Flow Batteries: The Energy Storage Breakthrough We've Needed James Conca; Forbes; 13 Dec 2016

the new V-flow batteries reduce the cost of storage to about 5¢/kWh.

UniEnergy Technologies (UET) of Seattle produces the largest MW-scale vanadium flow batteries yet, using a molecule developed at the Pacific Northwest National Laboratory. PNNL’s breakthrough was to introduce hydrochloric acid into the electrolyte solution, almost doubling the storage capacity and making the system work over a far greater range of temperatures, from -40°C to 50°C (-40°F to 122°F), removing a large previous cost of maintaining temperature control.

Presently, the largest installed V-flow battery in the U.S. is a UET 2MW/8MWh (power/total dischargeable energy in a single full charge) system in Washington State at the Snohomish County Public Utility District’s Everett Substation. This vanadium battery can keep the lights on in 1,000 homes for eight hours.

A V-flow battery system planned for Dalian China by UET's sister company Rongke will soon be the largest battery in the world at 200MW/800MWh.

New type of ‘flow battery’ can store 10 times the energy of the next best device Robert F. Service; AAAS Science; 27 Nov 2015

Lithium instead of Vanadium

See Gigha above.

zinc-bromide / Redflow


My home Redflow ZBM2 energy system installation by Simon Hackett Redflow; 28 Nov 2016

Sulfur / Sulphur

New Sulfur Flow Battery for Affordable Long-Term Grid Storage Prachi Patel; IEEE Spectrum; 16 Oct 2017

With a new battery, researchers at MIT say they have found the sweet spot for energy storage. The energy-dense battery could be the first to compete with the installed cost of pumped hydro and compressed-air storage, which cost around $100 per kilowatt-hour of energy stored. Scaled-up versions of the new battery could store electricity for a fifth of that, at $20/kWh. By comparison, Tesla claims its Gigafactory can produce batteries for around $125/kWh.
The new battery might even have what it takes to replace fossil fuel “peaker” plants that can quickly inject power into the grid at high demand times. To compete with peaker plants, we need immense batteries that store energy from wind and solar for multiple days, even months, at an installed cost of around $50/kWh.
The device, reported in the journal Joule, is a type of flow battery, in which both the anode and cathode are liquid electrolytes. The anode in this case is sulfur dissolved in water, while the cathode is an aerated liquid salt solution that takes up and releases oxygen.
Lithium ions move between the electrolytes, and the salt solution at the cathode takes up or releases oxygen to balance the charge. During discharge, it takes up oxygen and the anode ejects electrons into an external circuit. When the oxygen is released, electrons go back to the anode, recharging the battery.


SunVault Energy

claims 80 / 175-200 / 375 WH/kg
> 500 cycles
"significantly lower - under market" cost
90-95% charge depth
carbon + non-toxic electrolyte

Fast-charging everlasting battery power from graphene Han Lin;; 19 Jul 2016

Swinburne University researchers have invented a new, flexible energy-storage technology that could soon replace the batteries in our cars, phones and more. Han Lin's new super battery (actually, a supercapacitor) can store as much energy per kilogram as a lithium battery, but charges in minutes, or even seconds, and uses carbon instead of expensive lithium.
Previously, a major problem with supercapacitors has been their low capacity to store energy. But Han has overcome this problem by using sheets of a form of carbon known as graphene, which has a very large surface area available to store energy. Large scale production of the graphene that would be needed to produce these supercapacitors was once unachievable, but using a 3-D printer, Han is able to produce graphene at a low cost.

Economics & feasibility

A Nation-Sized Battery pdf Tom Murphy - associate professor of physics at the University of California, San Diego.

what it would take to build battery-based storage for the US for 100% renewables

The Holy Grail of Battery Storage Roger Andrews; Energy Matters; 18 Aug 2016

A recent Telegraph article claims that storage battery technology is now advancing so fast that “we may never again need to build 20th Century power plants in this country, let alone a nuclear white elephant such as Hinkley Point” and that the “Holy Grail of energy policy” that will make this solution economically feasible – a storage battery cost of $100/kWh – will be reached in “relatively short order”. This brief post shines the cold light of reality on these claims by calculating battery storage costs based on the storage requirements for specific cases estimated in previous Energy Matters posts. It is found that installing enough battery storage to convert intermittent wind/solar generation into long-term baseload generation increases total capital costs generally by factors of three or more for wind and by factors of ten or more for solar, even at $100/kWh.

Blowout Week 251 Roger Andrews, Energy Matters; 20 Oct 2018

Tesla [...] has just increased the price of its 13.5 kWh Powerwall unit plus supporting hardware from $US6,600 ($489/kWh) to $7,800 ($578/kWh)

The cost of wind & solar power: batteries included Roger Andrews; Energy Matters; 22 Nov 2018

For some time now we here on Energy Matters have been harping on about the prohibitive costs of long-term battery storage. Here, using two simplified examples, I quantify these costs. The results show that while batteries may be useful for fast-frequency response applications they increase the levelized costs of wind and solar electricity by a factor of ten or more when used for long-term – in particular seasonal – storage. Obviously a commercial-scale storage technology much cheaper than batteries is going to be needed before the world’s electricity sector can transition to intermittent renewables. The problem is that there isn’t one.

Battery raw materials

Batteries, mine production, lithium and the “cobalt crunch” Roger Andrews; Energy Matters; 29 Aug 2018

Growth in Li-ion batteries depends on a number of imponderables, such as how rapidly the world converts to electric vehicles, how quickly battery manufacturing capacity can be ramped up and where the electricity to power millions of EVs will come from. This post ignores these issues, concentrating instead on the question of whether the mining sector can increase production of the metals and minerals needed to support a high-battery-growth scenario, and without running out of reserves. The data are not good enough to reach a firm conclusion, but the main uncertainty seems to be whether cobalt production from the Congo, which presently supplies over half of global demand, can be relied on. Lithium and cobalt reserves will not be exhausted in the time frame considered (out to 2030) but will be close to it if no additional reserves are discovered.


Seasonal Storage for Homes? German Firm Sells Residential Batteries Tied to Fuel Cells JASON DEIGN; GreenTech Media; 26 Mar 2018

A German firm is aiming to help homes obtain year-round self-produced renewable energy with a hybrid storage system combining batteries with hydrogen.
Zeyad Abul-Ella, managing director and founder of Berlin-based Home Power Solutions (HPS), said his company’s Picea all-in-one unit, which went on sale this month, “has a hundred times more storage capacity with twice the output” of competing systems.
The system deliverssolar-powered heating and ventilation as well as electricity, the company said. It comes with a guarantee that customers can service 100 percent of their own energy requirements from their own solar panels, which are not included.
Under the hood, the Picea system contains lead-gel batteries and a fuel cell, electrolyzer, solar charge controller, inverter, hydrogen tank, heat exchanger and storage, ventilation unit and energy management system.
It has a peak electrical output of 20 kilowatts, a continuous power rating of 8 kilowatts, and can store energy for thermal, daily and seasonal use, according to a product data sheet. The daily storage capacity amounts to 25 kilowatt-hours.
The Picea’s thermal storage tank, meanwhile, can deliver up to 45 kilowatt-hours, with 350 kilowatt-hours to 1 megawatt-hour of seasonal storage capacity, presumably delivered through hydrogen.
The technology mix is designed to allow the Picea to keep a household running off solar and battery storage in summer, while storing up enough hydrogen to cover energy use over the winter.
Overall, the system, which will start shipping in the fourth quarter of 2018, is expected to deliver between 3 and 6 megawatt-hours of energy a year.
This should be enough to satisfy the needs of a four-person German household, which the German Federal Environmental Agency calculates would use around 4 megawatt-hours a year, according to HPS.
On launch, the company said Picea pilot installations were running “in a range of environments.”
Abul-Ella said the first 50 Piceas were being sold for €54,000 ($66,550), excluding sales tax. Installation costs “will be charged separately by the distribution partners, in line with usual practice,” Abul-Ella said.
Given that the German Association of Energy and Water Industries says a typical three-person home in Germany now spends €85.80 ($105.70) a month on energy, that means a payback period of more than 50 years.
And this price does not include the cost of a solar array.

Hydro / pumped hydro

Pumped Storage SEWTHA

Pumped Storage Energy Education

Assessment of the European potential for pumped hydropower energy storage - A GIS-based assessment of pumped hydropower storage potential Marcos Gimeno-Gutiérrez, Roberto Lacal-Arántegui; European Commission JRC Scientific and Policy Reports; 2013

'Store more energy in water', says Scottish Power dodgy figures

Dinorwig Power Station

c. 340MW (?)
Synchronised and spinning-in-air emergency load pick-up rate from standby: 0 to 1,320 MW in 12 seconds

Cruachan Power Station (aka "Hollow Mountain")

The station is capable of generating 440 megawatts (590,000 hp) of electricity from four turbines
When the top reservoir is full, Cruachan can operate for 22 hours before the supply of water is exhausted
Therefore capacity = 440 * 22 = 9680MWh


Norway Could Provide 20,000MW of Energy Storage to Europe Mike Stone; Green Tech Media; 10 Aug 2015

Norway has a lot of hydroelectric plants: a total of 937 of them, which provide a population of 5 million with around 98 percent of its electricity. In fact, the Scandinavian country is home to roughly half of all the hydroelectric water storage reservoirs in Europe.
This vast system could also offer a Europe a substantial amount of energy storage -- up to 20 gigawatts of it -- if an ambitious scheme currently being proposed can overcome political and social hurdles and get the necessary funding. That’s according to Kaspar Vereide, an engineer at the Norwegian University of Science and Technology in Trondheim. And his models suggest it could all be achieved in seven years.

Why Norway Can’t Become Europe’s Battery Pack Jason Deign; Green Tech Media; 13 Mar 2017

New research casts doubt on the view that pumped hydro power could allow Norway to act as battery pack for other parts of Europe.
Dr. Björn Peters, a German energy investor turned researcher, says that even though Norway’s hydro capacity is “huge,” most of it is in fact needed to power Norway. “Theoretically, Norwegian electricity storage would be sufficient to compensate for the fluctuations in solar and wind energy in Germany, even if Germany was supplied solely by sun and wind energy,” he said. “However, since 2002 an average of about 44 terawatt-hours had to be stored between the summer and winter in Norway. The lowest and highest filling levels of the reservoir lakes were [between] about 15 terawatt-hours and slightly over 77 terawatt-hours.” This means nearly all the country’s 82 terawatt-hours of storage was used by Norwegians, Peters said.


UK hydro storage is ‘undervalued’ RE News; 4 Oct 2016

There needs to be a radical overhaul of the way pumped storage hydro’s benefits are quantified to reflect the value it can bring to the electricity system, according to a new report by DNV GL. The report – ‘The Benefits of Pumped Storage Hydro to the UK’ – was funded by the Scottish Government, SSE and ScottishPower and makes several recommendations to encourage the expansion of the technology. There needs to be a radical overhaul of the way pumped storage hydro’s benefits are quantified to reflect the value it can bring to the electricity system, according to a new report by DNV GL. The report – ‘The Benefits of Pumped Storage Hydro to the UK’ – was funded by the Scottish Government, SSE and ScottishPower and makes several recommendations to encourage the expansion of the technology.

Strath Dearn

World’s biggest-ever pumped-storage hydro-scheme, for Scotland? Scottish Scientist; 15 Apr 2015

The Loch Ness Monster of Energy Storage Euan Mearns; Energy Matters; 22 May 2015

further comments on Strath Dearn


Glenmuckloch Pumped Storage Hydro Scheme Glenmuckloch Pumped Storage Hydro Ltd; Dec 2015

Non-Technical Summary

The Glenmuckloch Pumped Storage Hydro Scheme Euan Mearns; Energy Matters; 12 Dec 2016

Scotland is to get a new pumped storage hydro scheme, not in the Highlands but in the Scottish Borders. With a capacity of 400 MW and an estimated 1.7 GWh of storage this plant can make a meaningful 4 hour contribution to peak generation every day. But wooly[sic] arguments made about smoothing intermittent renewables makes it unclear if this commendable strategy is the intended use.


Dubai to build Persian Gulf’s first hydroelectric plant, 880 million gallon ‘battery’ Michael Kowalczuk; electrek; 23 Dec 2016

The plant will make use of the 1,716 million gallons water stored in the Hatta Dam to generate electricity. It will also see the construction of an upper reservoir that will be built in the mountain 300 meters above dam level, which will be able to store up to 880 million gallons. The 250 MW power station will make use of falling water passing through turbines to generate electricity during peak hours. During off-peak hours, the station will utilize solar energy to pump water back up to the upper reservoir.

Chile - Valhalla

The Valhalla solar/pumped hydro project Roger Andrews; Energy Matters; 27 Dec 2017

When and if it gets built the Valhalla project will consist of a 600 MW solar farm and a 300 MW pumped hydro plant which, it is claimed, will in combination deliver continuous baseload power to Northern Chile. If the project works as planned it will indeed deliver continuous baseload power, but only enough to fill about 5% of Northern Chile’s baseload demand. However, it would be the first to demonstrate that baseload power can be generated from a utility-scale PV plant. Development is presently on hold while Valhalla seeks $1.2 billion in financing.
The Valhalla project will send intermittent generation from the 600 MW Cielos de Tarapacá solar PV farm to the 300 MW Espejo de Tarapacá pumped hydro plant in order to convert it into baseload power.

How Chile’s electricity sector can go 100% renewable Roger Andrews; Energy Matters; 3 Jan 2018

If pumped hydro plants that use the sea as the lower reservoir can be put into large-scale operation Chile would be able to install at least 10 TWh of pumped hydro storage along its northern coast. With it Chile could convert enough intermittent solar into dispatchable form to replace all of its current fossil fuel generation, and at a levelized cost of electricity (provisionally estimated at around $80/MWh) that would be competitive with most other dispatchable generation sources. Northern Chile’s impressive pumped hydro potential is a result of the existence of natural depressions at elevations of 500m or more adjacent to the coast that can hold very large volumes of sea water and which form ready-made upper reservoirs.

Australia - Snowy 2.0

Higher electricity bills if Snowy 2.0 hydro not built, says Frydenberg Paul Karp; The Guardian; 9 Jan 2018

The Snowy 2.0 pumped hydro scheme would add 2,000 megawatts of capacity to the existing hydro plants and 350,000MW hours of storage.

Frydenberg said this was the equivalent of 2,700 of South Australia’s big batteries or $180bn of Tesla power walls.

The project’s feasibility study, released in December, found that despite costing up to $4.5bn it would still be economically viable.

Addressing the fact that the estimated $2bn cost of transmission to connect Snowy 2.0 to the grid is not included, Frydenberg said poles and wires “are typically regulated assets that are built by the operator”.

About Snowy 2.0 website

Great Lakes

The pumped hydro storage potential of the Great Lakes Roger Andrews; Energy Matters; 12 Feb 2018

The potential energy contained in the waters of the Great Lakes amounts to approximately six thousand terawatt hours, enough to supply the US and Canada with electricity for an entire year were the lakes to be drained to sea level. This of course will never happen, but there may be potential for partial utilization of the resource. A pumped hydro system that uses Lakes Huron and Michigan as the upper reservoir and Lake Ontario as the lower could theoretically generate 10 terawatt-hours, or more, of seasonal energy storage without changing lake levels significantly. The most likely show-stopper is the increased likelihood of flooding in the lower St. Lawrence River during pumped hydro discharge cycles. (Inset: Niagara falls runs dry in 1969).

USA / Hoover Dam

The Hoover Dam pumped hydro proposal Roger Andrews; Energy Matters; 1 Aug 2018

The Los Angeles Department of Water and Power (LADWP) plans to add a pumped hydro system to the existing Hoover dam hydro plant to help store California’s excess solar and wind generation and to increase the dam’s capacity factor, which is currently around 20%. As far as I know this would make the Hoover dam the world’s first hydro plant to combine both conventional and pumped hydro. No project details are presently available, but there is enough background information to scope out what the project might involve and whether it will justify its reported $3 billion price tag. The results show that numerous technical, legal, and environmental issues will have to be resolved before the project can go ahead, and if it does it will store only a small fraction of California’s growing intermittent renewable surpluses. It seems that the benefits will not justify the cost.

Other Seawater Pumped Storage locations

The seawater pumped hydro potential of the world Roger Andrews; Energy Matters; 18 Apr 2018

As discussed in numerous previous posts the world will need immense amounts of energy storage to transition to 100% renewables, or anywhere close to it, and the only technology that offers any chance of obtaining it is sea water pumped hydro (SWPH) storage. Here I consider the practical aspects of SWPH and conclude that there are only three places in the world where a combination of favorable shoreline topography and minimal impacts would allow any significant amount of SWPH to be developed – Chile (discussed here), California (discussed here) and, of all places, Croatia.

compressed air

Compressed Air Energy Storage (CAES) Energy Storage Association

The Intermountain Energy Storage Project Power Engineering; 19 Apr 2016

Compressed Air store in underground salt cavern in Urah for wind power supply for Los Angeles

underwater balloons

Storing Energy in Underwater Balloons R. Kress; EnergyBiz Magazine; Spring 2016

Hydrostor, a Canadian startup that has launched the world's first underwater compressed-air energy-storage solution ... recently brought online a grid-connected, 1-MW system using inflatable balloons positioned 180 feet below the surface of Toronto's Lake Ontario. The system -- capable of holding enough energy to power 330 homes -- will be operated by Toronto Hydro. The utility intends to use the Hydrostor system to store electricity during offpeak hours and then tap into it as demand grows.

ARES rail

The train goes up, the train goes down: a simple new way to store energy David Roberts; Vox; 28 Apr 2016

It's from a company called ARES. Here's how it works:
  • The train carries big rocks uphill, consuming electricity.
  • Then the train carries big rocks downhill, generating electricity.
That's it. The energy stored by going uphill is released by going downhill.

ARES Performance

An ARES facility will provide the full range of energy storage capabilities generally associated with pumped-storage hydro at approximately 60% of the capital cost and at a significantly higher efficiency. Additionally, ARES has system features which are not traditional to competing forms of energy storage, including but not limited to the following attributes:
  • Reactive Power Production – The shuttle-trains onboard Dual 3-Level Active Rectifier/Invertors are capable of supplying 25% of generated system power as reactive power for grid VAR support in full discharge mode and in excess of 100% of system power as reactive power while synchronized to the grid in standby.
  • Heavy Inertia – When in direct grid synchronization the ARES shuttle-trains provide beneficial heavy inertia -- augmenting grid stability against the loss of heavy generating facilities and increasing reliance on solar energy.
  • High Efficiency Regulation – While providing Regulation-Up and Regulation-Down support to the ISO a separate dedicated pool of loaded ARES shuttle-trains are available to dispatch from mid-system elevation complying with ISO regulation commands without having to overcome the efficiency loss of operating on pre-stored energy. As such an ARES facility is able perform a round-trip regulation Reg-Up/Reg-Down command at over an 86% operating efficiency.
  • Variable Output at Constant Efficiency – Unlike CAES and pumped-storage hydro there is no loss of system pressure during discharge. ARES system efficiency is constant over the full range of discharge and power output.


  • efficiency > 80%
  • capacity 50MW 12.5 MWh

Is ARES the solution to the energy storage problem? Roger Andrews; Energy Matters; 6 Apr 2016

many sources and calculations, extensive discussion of storage technologies in the comments


Articles in category: Flywheel Energy Storage Association

Making the Case for Spinning Reserve on the Grid Chris Campbell; Renewable Energy World; 31 May 2011

an[] application for which advanced energy storage is showing significant benefits is spinning reserve. In this application, storage assets can efficiently increase the reliability and improve the responsiveness of the electric power grid. Advanced energy storage can also release traditional generation—otherwise encumbered by an obligation to provide some amount of spinning reserve— to sell more valuable energy output.
To help ensure consistent availability and reliability of electricity, utilities keep generation capacity on reserve that can be accessed quickly if there is a disruption to the power supply. For example, if a base load generator or a major transmission line delivering imported power goes down, the utility and/or grid operator will access its reserve capacity to compensate.
Typically, this reserve capacity is created by generators that are already synchronized with the power grid but are not operating at full capacity. If backup power is needed, utilities will increase the output of these generators, usually by increasing the rotation of the turbine (hence “spinning reserve”). Typically, a 10-minute response time is a minimum requirement to qualify as spinning, or “operating” reserves.
However, leveraging traditional generation assets for creating reserved capacity creates a number of inefficiencies. For example, because these generators are operated below their rated value, the utility is not maximizing their power output that could be used for base load supply. Also, it requires the use of additional fuel to ramp these generators up in the event that their reserved generation potential is needed, which increases emissions while reducing the net efficiency of the power system.
Alternatively, energy storage can be implemented onto the power grid as spinning reserve assets. These systems provide a cleaner, more efficient mechanism for utilities to compensate for disruptions to the power supply while enabling them to leverage the full capabilities of their generation assets to deliver base-load power. The most advanced storage solutions are also equipped with sophisticated monitoring and control systems, enabling them to detect disruptions in the power supply and communicate quickly with the grid to near-instantaneously discharge and provide the reserve capacity when it is needed.

Amber Kinetics

Amber Kinetics: Turning Flywheels Into Multi-Hour Energy Storage Assets Jeff St. John; Greentechmedia; 10 Dec 2015

Flywheels are a well-known energy storage technology, at least on the power side of the equation. They work by spinning up a heavy disk or rotor to high speeds, and then tapping that rotational energy to discharge high-power bursts of electricity. Companies like Vycon, Active Power and Beacon Power provide emergency ride-through power for buildings, or fast-responding frequency regulation services for grid operators, to name two typical use cases.
But it’s a lot harder to use flywheels to store energy for hours at a time. Mainly, that’s due to “coasting losses” -- the inevitable mechanical and electromagnetic forces that slow down a heavy spinning object. These challenges have pretty much relegated long-duration flywheels to research labs -- at least, until now.
Last week, Amber Kinetics unveiled a four-hour duration flywheel system, one it says combines the efficiency and flexibility of an electrochemical battery with the durability and lifespan of a simple mechanical device.
The core system is a 25-kilowatt-hour flywheel, capable of charging and discharging for more than one duty cycle per day,
Ten flywheels in a storage container make up what the company is calling an “energy block,”


Europe’s first flywheel storage plant set to debut Power Engineering International; Apr 2015

The first grid-connected hybrid flywheel project in Europe has been announced and is to be sited in the Irish midlands.
SchwungradEnergie Limited is behind the project and will collaborate with the Dept. of Physics and Energy at the University of Limerick and US company, Beacon Power.

Irish flywheel storage project could prove crucial tech for EU green ambitions Diarmaid Williams; Power Engineering International; Apr 2015

The first grid-connected hybrid flywheel project in Europe could potentially be rolled out across the rest of the European Community once it initially gets off the ground in Ireland.
Frank Burke, Technical Director at Schwungrad, the company behind the flywheel project told Power Engineering International that the Irish experience in using the technology to maintain a stable grid as more and more renewable power is loaded on will serve to inform other member states.
“With the Irish context there is the pretty high target of going 40 per cent renewable by 2020 which is only a few years away now. One of the problems at the moment is that the system can’t allow more than 50 per cent of non-synchronous renewable generation at any one time; it’s not just renewable, that also applies to the interconnectors because those interconnectors are DC and are not synchronised. The problem is growing every year where a renewable plant is having to be curtailed because they can’t allow more than 50 per cent on.”

gravity battery

Gravity Battery: An illustrated concept detailing the long-term, low-maintenance storage of energy through the use of the force gravity


Thermal Energy Storage - Technology Brief IRENA: International Renewable Energy Agency

Thermal stores Energy Saving Trust

The Drake Landing project uses an interseasonal thermal store

The Future Role of Thermal Energy Storage in the UK Energy System: An Assessment of the Technical Feasibility and Factors Influencing Adoption Eames, P., Loveday, D., Haines, V., Romanos, P.; UKERC; 2014

ThermalBanks™ store heat between seasons ICAX Interseasonal Heat Transfer

Ice store

Viessmann Installs First UK 'Energy from Ice' Heating System Heat Pumps Today; 10 Oct 2015

Heating and refrigeration solutions manufacturer, Viessmann, has installed 'ice store system, in a UK property domestic property, the company announced this week. The innovative system recovers energy from renewable sources to heat or cool buildings, and supplies hot water. Viessmann installed the first system in a new, sustainable housing development at HUF HAUS' UK show room near Weybridge, Surrey. The system takes energy from ice to heat or cool the house. It supplies the energy to heat pumps for heating and hot water in the winter, and for cooling in the summer. The Viessmann system takes energy from water in its ice store. The water temperature drops and, as the energy is withdrawn, the water freezes . The system keeps on taking heat from the ice.

Fighting Air Conditioning's Peak Demand With Thermal Energy Storage James Conca; Forbes; 7 Jul 2016

As we head into the hottest part of summer in the Northern Hemisphere, in what could be the hottest year on record, we barely give a thought to what using air conditioning does to our electricity grid. And what it will do to a hotter world in the future.


Thermodynamic analysis of a liquid air energy storage system Giuseppe Leo Guizzi, Michele Manno, Ludovica Maria Tolomei, Ruggero Maria Vitali; Energy; 15 Dec 2015

The rapid increase in the share of electricity generation from renewable energy sources is having a profound impact on the power sector; one of the most relevant effects of this trend is the increased importance of energy storage systems, which can be used to smooth out peaks and troughs of production from renewable energy sources.
Besides their role in balancing the electric grid, energy storage systems may provide also several other useful services, such as price arbitrage, stabilizing conventional generation, etc.; therefore, it is not surprising that many research projects are under way in order to explore the potentials of new technologies for electric energy storage.
This paper presents a thermodynamic analysis of a cryogenic energy storage system, based on air liquefaction and storage in an insulated vessel. This technology is attractive thanks to its independence from geographical constraints and because it can be scaled up easily to grid-scale ratings, but it is affected by a low round-trip efficiency due to the energy intensive process of air liquefaction. The present work aims to assess the efficiency of such a system and to identify if and how it can achieve an acceptable round-trip efficiency (in the order of 50–60%).

Load shifting of nuclear power plants using cryogenic energy storage technology Yongliang Li, Hui Cao, Shuhao Wang, Yi Jin, Dacheng Li, Xiang Wang, Yulong Ding; Applied Energy; Jan 2014

  • Cryogenic energy storage is used for grid scale load shifting of nuclear power plant.
  • Supercritical air liquefaction and re-gasification processes are facilitated by thermal fluid based sensible cold storage.
  • Peak capacity of nuclear power station can be nearly tripled with a roundtrip efficiency of around 70%.
To balance the demand and supply at off-peak hours, nuclear power plants often have to be down-regulated particularly when the installations exceed the base load requirements. Part-load operations not only increase the electricity cost but also impose a detrimental effect on the safety and life-time of the nuclear power plants. We propose a novel solution by integrating nuclear power generation with cryogenic energy storage (CES) technology to achieve an effective time shift of the electrical power output. CES stores excess electricity in the form of cryogen (liquid air/nitrogen) through an air liquefaction process at off-peak hours and recover the stored power by expanding the cryogen at peak hours. The combination of nuclear power generation and the CES technologies provides an efficient way to use thermal energy of nuclear power plants in the power extraction process, delivering around three times the rated electrical power of the nuclear power plant at peak hours, thus effectively shaving the peak. Simulations are carried out on the proposed process, which show that the round trip efficiency of the CES is higher than 70% due to the elevated topping temperature in the superheating process and thermal efficiency is also substantially increased.

Pumped Heat Energy Storage (PHES)

Pumped Heat Electrical Storage (PHES) Energy Storage Association

In Pumped Heat Electrical Storage (PHES), electricity is used to drive a storage engine connected to two large thermal stores. To store electricity, the electrical energy drives a heat pump, which pumps heat from the “cold store” to the “hot store” (similar to the operation of a refrigerator). To recover the energy, the heat pump is reversed to become a heat engine. The engine takes heat from the hot store, delivers waste heat to the cold store, and produces mechanical work. When recovering electricity the heat engine drives a generator.
PHES requires the following elements: two low cost (usually steel) tanks filled with mineral particulate (gravel-sized particles of crushed rock) and a means of efficiently compressing and expanding gas. A closed circuit filled with the working gas connects the two stores, the compressor and the expander. A monatomic gas such as argon is ideal as the working gas as it heat/cools much more than air for the same pressure increase/drop - this in turn significantly reduces the storage cost.



Isentropic Ltd was established to develop Pumped Heat Electricity Storage (PHES), a standalone energy storage system based on a novel, high efficiency reciprocating engine and large scale thermal stores. The long-term market opportunity for energy storage is a low-cost stand-alone system which will allow the grid to respond to variation in load and generation as more power comes from intermittent renewable sources.

Isentropic Pumped Heat Electricity Storage (PHES) is in development at our UK facility.

The development of the thermal stores has also led to an energy storage technology integrated into gas power plant: Gas Turbine Integrated (GTI) Storage.

GTI-Storage offers either Rapid Response or Enhanced Turndown systems, one a fast reacting technology to support frequency response on the grid and the other to provide longer term storage. Both of these technologies are at the development stage.

Isentropic PHES Technology Explained Isentropic Ltd; Youtube; 19 Mar 2014

Molten Silicon

Silicon will blow lithium batteries out of water, says Adelaide firm Ben Potter; Financial Review; 10 Feb 2017

An Adelaide company has developed a silicon storage device that it claims costs a tenth as much as a lithium ion battery to store the same energy and is eyeing a $10 million public float. 1414 Degrees had its origins in patented CSIRO research and has built a prototype molten silicon storage device which it is testing at its Tonsley Innovation Precinct site south of Adelaide. Chairman Kevin Moriarty says 1414 Degrees' process can store 500 kilowatt hours of energy in a 70-centimetre cube of molten silicon – about 36 times as much energy as Tesla's 14KWh Powerwall 2 lithium ion home storage battery in about the same space. Put another way, he says the company can build a 10MWh storage device for about $700,000. The 714 Tesla Powerwall 2s that would be needed to store the same amount of energy would cost $7 million before volume discounts.
The device stores electrical energy by using it to heat a block of pure silicon to melting point – 1414 degrees Celsius. It discharges through a heat-exchange device such as a Stirling engine or a turbine, which converts heat back to electrical energy, and recycles waste heat to lift efficiency.

Hot rocks

Wind and solar can become dispatchable within three years Leigh Collins; Recharge News; 20 Mar 2018

A new low-cost storage solution to enable dispatchable wind and solar is set to become commercially available as soon as 2020, and it could revolutionise the world’s energy industry.
The technology being simultaneously developed by wind turbine maker Siemens Gamesa and start-up Stiesdal Storage Technologies is a form of thermal energy storage that uses excess renewable energy to heat a “pack bed” of crushed volcanic rocks to as high as 600°C. The stones stay hot for days or weeks simply by being well insulated; then when energy is required, the heat is converted back into electricity and delivered to the grid for as little as €70 ($86.25) per MWh — far cheaper than any gas peaker plant or battery system.
Since retiring from Siemens at the end of 2014, Stiesdal has set up his own eponymous company, which is now working on its own version of the “hot-rock” thermal storage system, with a view to building a pilot plant of up to 5MW/120MWh in Denmark next year.
“There are two main differences [between the Siemens and Stiesdal systems]. Siemens uses an electric heater to heat the pack bed; I use a heat pump. And then they use a steam system for discharge; I use an air-based system that resembles a gas turbine.
“They prefer a system that is a little simpler than what I do, which I also think is a good idea. But I have sort of become seduced by my heat pump system. I really like it.”
Both projects use off-the-shelf equipment to keep costs low. Stiesdal uses “dirt cheap” mineral rock wool as the insulation material, saying that his pack bed will only lose 0.5% of its heat per day; SGRE uses “a combination of different materials”, including mineral rock wool, but declined to provide a heat loss figure. Stiesdal uses basalt, the most common rock type on Earth, as the storage medium; SGRE uses a different “common rock”, declining to specify the particular type. Stiesdal says his rocks will reach 550°C, SGRE says its will hit 600°C.
... SGRE will build a commercial pilot project “around 2020” of about 100MWh, probably in partnership with one of those interested utilities — while launching the technology onto the market at the same time.