Long Duration Storage

Cost-effective, geographically flexible, seasonal storage can help overcome the variable nature of some renewable energy sources while improving service reliability and resilience by mitigating supply/demand peaks. This energy industry segment was identified as one that can help accelerate the transition to a sustainable, equitable, and abundant energy future.

Against current state-of-the-art comparable technology, what markers must innovations in this space meet to overtake the fossil fuel-driven energy?

  • **Benchmark**: What is the current state-of-the-art and/or most common technology/process to evaluate against?
  • **Cost**: Based on the chosen benchmark, what is a competitive capital cost and/or O&M/service cost?
  • **Duration**: Based on the chosen benchmark, what is the warranted duration? What would be the audacious, yet realistic, duration?
  • **Efficiency**: Based on the chosen benchmark, what is a target efficiency?
  • **Lifecycle**: Based on the chosen benchmark and industry trends, what is the warranted lifecycle?

Please share details and resources if possible.

Hi @b0bbybaldi, @Access600, @anis, @nastben, @cananacar, @honghong - In regards to long duration storage of renewable energy sources - What markers must innovations in this space meet to overtake the fossil fuel-driven energy?

Hi @Shashi this is a problem of scale mostly. I like that @JessicaYoon pointed out that each geographic location has inherent competitive advantageous types of storage. Amongst the most popular ones that I believe are good options that utilise gravity or pressure-based systems. Some examples of these are pump based storage where one would move fluid towards a place of higher potential energy (either gravitational or because of pressure interactions with environmental conditions). When needed, such excess produce would maintain stability for electricity production. Nevertheless, as one can see, these systems are very different from one another, making it hard to reach the benefits of scale that fossil fuels already enjoyed inherently to their nature.

Therefore, it would make sense for individual companies to specialise in each type of storage to reach scale by applying their expertise in a global scenario, subsidising batteries, especially newer optimised chemistries, and optimising and increasing hydrogen from renewable energy production. For this reason, I am a firm believer that Hydrogen production would be a very competitive type of storage for renewable energy as the transition from fossil fuels to such would also be reasonably painless.

Other exciting technologies optimise efficiencies and enhance system-wise communication by utilising advancements in computing and internet technologies. These innovations would reduce consumption, and increase efficiency would also reduce the storage needs; thus, we need to think about increasing storage while reducing the need for it with better-designed starting points.

The long term energy storage I use as a benchmark is the Strategic Petroleum Reserve (United States)
While this is a fossil fuel device, it represents about 100 Quad BTUs which is what US leaders have depended upon for decades. Adding to this reserve, there is a significant amount of fossil fuels located in pipelines and tanks distributed widely across the nation.
While getting to net zero is important, I don’t think the US (or other nations) will abandon energy security or stability.
The purpose of my post is to establish a sense of magnitude of the amount of energy that needs to be stored. I also hope to establish a sense of the stability of the energy while being stored.

Some will advocate hydrogen for storage. Others will suggest batteries or even ammonia. I think the molecules I favor most are a blend of tridecane and pentadecane.

Thanks @b0bbybaldi and @mikelandmeier for sharing these inputs. We would further like to understand from you both, your take on the cost markers that an innovation in this space needs to meet for people to shift to renewable energy.

Hi @curranc, @RicardoChacartegui, @EEI, @AnthonyMburu, @aphhuang, @jmathieu - Curious to know if you have any inputs to share on - In regards to renewable energy storage space, against current technology, what benchmarks for cost, duration, efficiency and lifecycle will help in overtaking the fossil fuel-driven energy?

Speaking from an East African perspective, which would probably hold true for most of Sub Sahara Africa, the cost benchmark of fossil fuel driven energy ranges from US$0.15 - US$70/kWh depending on scale, type of fossil fuel (from HFO to Diesel), market prices, subsidies and taxation. Since storage needs generation, i like to look at it from the angle of pairing solar PV + storage (this being the most scaleable renewable energy technology for the continent). Current benchmarks for Solar PV at scale hover around the USD 0.04-0.06/kWh range and battery energy storage currently varies from US$0.07 -0.14/kWh, implying a total Solar + Storage LCOE of US$0.11 - 0.20 ( excluding financing costs). Thus the cost benchmark of fossil fuel driven energy has been breached already. However the other factors will decidedly drive attractiveness of renewable energy storage even further: we have seen manufacturers like Tesla offering 15 year warranties ( implying +5400 cycles at 100% DoD) and flow batteries offering +20,000 cycles. Round trip efficiency rates of about 90% suggest marginal improvements are possible but these may not move the needle much further. Battery energy storage cost curves promise the biggest opportunity in overtaking fossil fuel energy- my prediction is that another $200/kWh price drop in the commercial and industrial BESS space from the observed range of just north of $450/kWh all in & commissioned will catalyse mass adoption of renewable energy + storage in the region: benchmark electricity prices range from $0.04 (heavily subsidised) - $0.22/kWh (more cost reflective) thus renewable energy + storage LCOE’s of between US$0.06 - 0.12/kWh will completely shift the electricity dynamics for most Sub Sahara African markets.
Storage duration depends on application- with hydro plants / compressed natural gas being some of the most common- long duration BESS are not yet there…the current balance of power / energy combinations benchmark set at the 4hr or 0.25C. Flow BESS offer longer durations albeit at the cost of round trip efficiencies and cost/kWh. The duration challenge can be solved by a combination of higher energy densities, low self discharge and infinite modularity: The Neoen Hornsdale BESS delivers 130MWh in blocks of 220kWh Tesla Powerpacks. Tesla’s Megapack now provides modular blocks of 3MWh, a 14x improvement. Duration may thus not be such a constraining factor for renewable energy storage.
In summary, my prediction is that the benchmarks to watch out for are better battery chemistries that deliver 10,000+ cycles, $250/kWh all in costs while maintaining round trip efficiencies of +90%

Hi, @Shashi I’m sorry if my reply will seem vague but I do not want to flood this page with an entire essay on the potential costs associated with energy storage. I would, however, recommend this report as it is a comprehensive one.


In a summary, although Fuel Cells and Electrolyzes still pose a high capital cost, when seen under a Levelized cost of electricity they are already cost-effective at a 28 to 19 USD cents/kWh range. While batteries, which are the most popular ones are at 83 - 28 USD cents/kWh. Although pumped hydro and air are the lowest cost at 13 - 10 USD cents/kWh they are not the most reproducible ones as to keep such metrics one requires salt caverns, or a diverse gravitationally potential terrain (such as one close to hills).
Therefore, Hydrogen is already the most cost-competitive, easily reproducible type of energy storage on a global scale, and one which can still be largely improved with further research and economies of scale.

Thanks @AnthonyMburu and @b0bbybaldi - for sharing these insights.

Hi @lixianfeng, @grhoffman7, @bernardsaw - Energy storage being your area of expertise would love to hear your thoughts on - What benchmarks for cost, duration, efficiency and lifecycle against current technology will be helpful in reliable and resilient renewable energy.

Hi, @Shashi. according to USABC, the long term goal for the energy storage system for EV is as below:
Power density: 600 W/L
Specific power density-discharge, 80% DOD/sec: 400 W/kg
Specific power-Regen, 20% DOD/10sec: 200 W/kg
Energy density-C/3 Discharge: 300 Wh/L
Specific energy-C/3 Discharge rate: 200 Wh/kg
Specific power/specific energy ratio: 2:1
Life: 10 years
Cycle life-80% DOD, cycles 1000
Selling price-25,000 units @40 kWh: 100/kWh
The reference can be found below