| A | B | C | D | E | F | G | H | |
|---|---|---|---|---|---|---|---|---|
1 | Technology | Brief description | Efficiency | Pros | Cons | Key companies | Stage of development | |
2 | Pumped hydro | Water is pumped into a reservoir at the top of a hill when electricity is abundant, then released downhill and used to power a turbine when electricity is needed. | 70-85% | Huge scale possible, cheap, allows decoupling of conversion and storage parts of system | Limited to areas with specific geographical / topographical features (i.e. hills, lakes), huge scale makes it challenging to fund | RheEnergise (next-generation) | Mature (next-generation = demonstration projects) | |
3 | Lithium-ion batteries | Should need no introduction. Being rapidly deployed in smartphones, in electric vehicles and on electricity grids around the world. Store electricity chemically. | >90% | Can be deployed anywhere, modular, costs falling rapidly. New types of battery (e.g. LFP, solid state) are improving performance and reducing costs. | Degradation means life of ~10 years (today - this will increase), typically only economic for storage durations of <8 hr, costs scale with energy storage capacity, concerns about demand for raw materials | Too many to list - e.g. CATL, LG, BYD, Panasonic | Mature, but improving and scaling | |
4 | Sodium-ion batteries | Batteries that use sodium in place of lithium. | ~90% | Can be deployed anywhere, use abundant raw materials, low degradation, potentially lower cost than lithium-ion, starting to be used in EVs which will drive volumes | Low energy density - batteries have to be bigger and heavier | CATL LiNa Energy | Early commercial projects | |
5 | Lead acid batteries | Batteries consisting of two electrodes made of a lead compound (the compound in question changes as the battery charges and discharges) and a sulphuric acid electrolyte. | 70-80% | Can be deployed anywhere, low cost, can provide high currents instantaneously, reliable across a wide range of operating temperatures. | Low roundtrip efficiency (compared to li-ion), low energy density, short lifespans, increased fire risk, limited depth of discharge. | Too many to list | Mature | |
6 | Metal air batteries | React metal with air in order to release energy (technically, metal air batteries use metal as an anode and atmospheric oxygen as a cathode). Several metals are being explored including iron and zinc. | 45-50% | Long storage durations (days rather than hours), safe, low cost, theoretically store more energy per kg than Li-ion | Low roundtrip efficiency (~50%), not demonstrated at any scale | Form Energy Zinc8 Energy e-Zinc | In development (Form) Demonstration projects (Zinc8) | |
7 | Nickel hydrogen batteries | Like a cross between a battery and a hydrogen fuel cell. As the battery is charged, hydrogen is produced and stored in pressure vessels. As the battery is discharged the hydrogen is consumed. | ~85% | Long lifespan (30,000 cycles) with minimal degradation, no maintenance required, operates in harsh environments (very high and low temps), no risk of thermal runaway, modular | Still higher cost than Li-ion today, not tested at grid scale, single manufacturer | EnerVenue | In development | |
8 | Liquid metal batteries | A high temperature battery that uses liquid metal electrodes and a liquid electrolyte. Charging the battery causes the negative electrode to get thicker, while the positive electrode gets thinner. When the battery discharges the reverse happens. | ~80% | Long lifespan with minimal degradation, low cost raw materials, simple manufacturing process | High operating temperature limits efficiency and storage duration, limited track record, single manufacturer | Ambri | Early commercial projects | |
9 | Sodium sulphur batteries | A high temperature battery that comprises a molten sodium anode, a molten sulphur cathode and a solid electrolyte. | 50-85% | High energy density, inexpensive raw materials, limited degradation (even under deep discharge cycles). | High operating temperature limits efficiency and storage duration | NGK Insulators BASF | Early commercial projects | |
10 | Flow batteries | Batteries that store energy in tanks of liquid electrolyte. | 65-85% | Zero degradation, very safe, conversion and storage decoupled (to store more energy, you just need bigger tanks of electrolyte) | Lower roundtrip efficiency and higher cost than Li-ion | Invinity ESS Inc. Redflow | Early commercial projects | |
11 | Compressed air energy storage (CAES) | When electricity is abundant air is pumped at high pressure into large tanks or salt caverns. When electricity is needed this air is released and used to drive a turbine. | 60-70% | Cheap, long storage durations, allows decoupling of conversion and storage, solid roundtrip efficiency, no degradation | High pressure air at scale can be dangerous, limited by geology - requires salt caverns for large scale storage | Hydrostor Apex CAES BaroMar Augwind | Early commercial projects | |
12 | Liquid air energy storage (LAES) | When electricity is abundant air is cooled to -200 degrees and stored as liquid in insulated tanks. When electricity is needed again the air is warmed, expanded and used to drive a turbine. | 40-70% | Can be deployed anywhere, long storage durations, reasonable cost relative to Li-ion, safe, allows decoupling of conversion and storage, no degradation | Questions about roundtrip efficiency, complex engineering projects | Highview Sumitomo SHI FW | Demonstration projects | |
13 | CO2 battery | Similar to liquid air but uses carbon dioxide. When electricity is abundant, CO2 is compressed so that it becomes a liquid at very high pressure. When electricity is needed, the CO2 is evaporated and expanded and used to drive a turbine. | ~75% | Solid roundtrip efficiency, low cost, no degradation. | Complex engineering projects, not yet tested at any meaningful scale | Energy Dome | Demonstration projects | |
14 | Geomechanical pumped storage | Similar to compressed air but uses water. When electricity is abundant, water is pumped underground until high pressures are achieved. When electricity is needed, the water is allowed to exit the rock formation, driving a turbine and generating electricity on the way. | TBC | Uses widely available components (e.g. pumps and compressors), long durations are possible - i.e. 10 hours or more, allows decoupling of conversion and storage, no degradation. | High pressure at scale can be dangerous, limited by geology or requires fracking (which can be controversial), complex engineering projects, not tested at any scale, single manufacturer. | Quidnet Energy Sage Geosystems | In development / demonstration projects | |
15 | Subsea pumped hydro | A large tank is placed on the seabed. When electricity is abundant water is pumped out of the tank. When electricity is needed, water is allowed to flow back into the tank under pressure, driving a turbine and generating electricity | TBC | Zero onshore land footprint, can be co-located with offshore wind, uses widely available components. | Complex engineering projects, construction likely to be expensive given offshore and at depth, super early stage - not tested at any scale. | Sperra | Research project | |
16 | Hydrogen | When electricity is abundant, it's used to power electrolysers and create green hydrogen. When electricity is needed again, hydrogen is converted back into electricity using a fuel cell. | 40-66% | Long storage durations, allows decoupling of conversion and storage, vast scale possible, potential for significant cost declines as hydrogen is deployed for other use cases | Low roundtrip efficiency, currently high cost, storage of hydrogen is challenging | ??? | In development | |
17 | Non-hydro gravity storage | When electricity is abundant, motors raise heavy objects (typically using tower cranes, or winches over mine shafts). When electricity is needed, objects are lowered and used to drive a turbine. | 80-85% | Simple, low cost, can be deployed anywhere (as long as you can build a tower / vertical shaft), no degradation | Low energy density - suitable for delivering / absorbing short bursts of power, not able to store large amounts of electricity | Energy Vault Gravitricity Terrament | Demonstration projects | |
18 | Flywheels | Heavy, spinning disk is accelerated to very high speeds. Used to drive a turbine when electricity is required. | ~90% | Simple, low cost, can be deployed anywhere, fast response, high roundtrip efficiency, no degradation | Low energy density - suitable for delivering / absorbing short bursts of power, not able to store large amounts of electricity | Levistor | Mature | |
19 | Supercapacitors and ultracapacitors | Similar to batteries in that they contain electrodes and an electrolyte. However, supercapacitors use static electricity rather than electrochemistry to store energy. | 85-98% | Can be deployed anywhere, no degradation, no maintenance, high power output, fast response, proven technology | Low energy density - suitable for delivering / absorbing short bursts of power, not able to store large amounts of electricity (typical cell has capacity of 0.03 kWh) | ??? | ??? | |
20 | Thermal storage | Electricity is used to make something very hot or cold and keep it that way until heating or cooling is required. | N/A | Simple, supports electrification of heat without requiring significant grid upgrades | Not technically an electricity storage technology as heat or cold will be used directly - storage in this way removes optionality | Brenmiller Rondo Sunamp Tepeo Caldera | Demonstration projects / early commercial projects | |
21 | Thermal storage plus thermophotovoltaics | When electricity is abundant heat is generated and transferred to blocks of graphite which reach temperatures in excess of 2,000 C. This heat can be used directly as needed, or converted baxk into electricity using thermophotovoltaic cells which harvest energy from the white hot graphite. | <50% | Theoretical low cost enables long storage durations, storage and conversion are decoupled. | Low roundtrip efficiency, very early stage, limited downward pressure on thermophotovoltaic cell cost. | Fourth Power Antora Energy | In development / demonstration projects | |
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23 | Notes: | |||||||
24 | - This was created as a personal project. Feel free to use the information as you wish, but please credit me if you do (my name is Kit Fitton and my BlueSky handle is @kitfitton.bsky.social) | |||||||
25 | - More detail on each of these technologies is available in this Medium article | |||||||
26 | - The accuracy of information in the above table is in no way guaranteed. | |||||||
27 | - If you have any questions, if there are technologies I've missed, if you spot any errors, or if you just want to chat, get in touch with me on BlueSky at https://bsky.app/profile/kitfitton.bsky.social. | |||||||
28 | - And no, Bitcoin is not a battery. | |||||||
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