During a few very hot and calm days in Texas in July of 2022 their more than 30,000 MW of wind power was operating at less than 8% of rated capacity but demand was setting new peaks. They scraped by with no blackouts.  During the winter of 2020-21 a similar no wind period occurred during an unusual cold spell which also knocked out some of their fossil fuel and nuclear generating capacity, causing dayslong blackouts across most of the state and multiple deaths mostly due to a lack of home heating. In addition, some natural gas production and transmission was disrupted.

It is common in parts of California to run out of power on hot days when there is little wind after the sun goes down, or on hot cloudy, windless days. Northern California has suffered rolling blackouts for the last couple of summers. Now Southern California is beginning to experience similar issues. On sunny and windy days from 2 to 5 PM they sometimes have over 1000 MW of excess power, and most nights after 10 PM have huge amounts of excess wind power. In 2021 California curtailed over 1.5 TW-HR of renewable energy and in the first half of 2022 over 2 TW-HR was curtailed.

Batteries seem to be a simple solution; however, these systems are expensive, have a lifetime of less than 12 years, take up a huge amount of land area, and generally are only practical for a few hours of energy storage. They are a good short-term emergency power source and will undoubtedly play an important role in the future energy mix. But they don’t solve the underlying problem – if the grid is short of power for more than a few hours, longer duration energy storage is required.

In addition, as the penetration of renewable power generation increases and the number of hours fossil fueled units operate declines, the average consumption of natural gas will decline and the average amount of gas in storage reservoirs will decline as there will be no incentive to store gas that won’t be used. However, the peak gas demand will decline to a much lesser degree, or possibly not at all. This means that at peak times of electric energy usage on days when renewable generation is hindered by low wind speed and clouds, or on windless evenings, an increase in high deliverability gas storage (stored gas that can be returned rapidly to the pipeline system) will be required to supply the fuel for the fossil fueled generation needed to meet grid demands.

Large Scale Long-Duration Hybrid Energy Storage

To accomplish a high penetration of renewable energy on the grid (more than 20-25%) while maintaining grid reliability, long duration energy storage systems are required that can store multiple days of electric energy. Large scale long-duration hybrid energy storage systems can fill this need. The storage system needs to be able to store both multiple hours of excess wind at night and shorter bursts of excess wind and solar power that often occurs in the afternoons.   

Not too different than a plugin hybrid car, large scale long-duration hybrid energy storage systems store excess electric energy and returns it when needed with the addition of a small amount of fuel. And like the plugin hybrid, hybrid energy storage brings along some important synergies.

  • Energy density is one – the same factor that gives the plugin hybrid much greater range than a full electric vehicle (EV).
  • Some plugin hybrids allow the engine and batteries to be used together to provide short bursts of power greater than what the battery or engine alone can supply, just as hybrid energy storage systems can return energy to the grid at a rate faster than the maximum charge rate, something batteries can’t do.  
  • As with the plugin hybrid vehicle, there are CO2 emissions, but this is largely offset by charging with excess renewable energy and the reduced environmental impact from the mining and manufacturing of the equipment compared to the manufacture of lithium-ion batteries.
  • When the battery goes dead on the plugin hybrid the car can still run on the engine. When the stored energy in the hybrid long-duration energy storage system is used up, they can still produce about 30% of their power by burning fuel.
  • Plugin hybrids cost more than an engine driven car but less than a full electric vehicle – the large scale long-duration hybrid energy systems cost more than a peaking gas turbine but much less than the same kilowatt-hour battery storage system  

Current Large Scale Long-Duration Hybrid Energy Storage Technology
Compressed Air Energy Storage

Compressed air energy storage (CAES) is a proven method of large scale long-duration hybrid energy storage. There are currently three of these systems in operation, two of them in operation for several decades (the 330 MW plant in Huntorf Germany; and the 110 MW system in Macintosh, Alabama), and the just recently started 100 MW system in China. These installations use off-peak power to compress air that is stored in underground salt caverns. They return more than 125% of the stored power to the grid at peak times by heating the air in a natural gas-fired combustor and expanding the hot, high-pressure air through a turbine driving a generator. The fuel rate is more than 25% less than that of a modern combined cycle power plant. The main drawback of CAES technology is the requirement for a location with very specific geology.  

 

Pumped Hydro

The oldest long duration energy storage systems in operation, pumped hydro is simple, reliable, and efficient but most of the suitable sites have already been developed.


The Just In Time Energy’s Technology Can Solve the Need for Both Long Duration Electric Energy Storage and High Deliverability Gas Storage

Just In Time Energy has two new approaches to large scale long-duration hybrid energy storage, both based on our patent approved technology – a vastly improved LAES system, and a completely new Combined Electric and Gas Storage System.

Optimized Liquid Air Energy Storage System   

 
Just In Time Energy’s Optimized Liquid Air Energy Storage (OLAES) system is a significant improvement over traditional LAES technology. Several air separation companies have proposed LAES systems, but all these systems proposed using a high pressure regenerator vessel to store, in a cold absorbing media, the phase change cold from the pumped liquid air as it is vaporized prior to the heating and expansion of air to make power. This stored cold is used to reduce the power consumption when making the next batch of liquid air. There are problems with this concept - the regeneration vessel is almost as large as the liquid air storage tanks but operating at the liquid air pump discharge pressure, not at atmospheric pressure like the storage vessels, and this thick-walled pressure vessel is fabricated from expensive cryogenic materials, making it impractical to build a system with more than 6 to 8 hours of energy storage. This pressure vessel makes it impractical to operate the system at pressures above about 900 psi, limiting the power output and efficiency of the system.

Just In Time Energy’s OLAES system eliminates the regeneration vessel. The phase change cold is used to make additional on-peak power which is normally worth anywhere from five to more than fifty times the value of the off-peak excess renewable power. Eliminating the expensive regeneration vessel allows for a higher pump pressure and thus increased power and efficiency from the hot air expansion and allows for multiple days (even weeks) of liquid air storage.

The OLAES system uses the -320°F phase change cold in the pumped liquid air as it is vaporized to re-condense the vaporized air after heating and expanding it in a first hot air turbine down to about 450 psia. Thus, forming a new liquid air stream at 450 psia and -200°F, which is then repumped to high pressure, vaporized, heated, and expanded again in a second hot air turbine to near atmospheric pressure, thereby producing more power.

The -200°F phase change cold in the 450 psia liquid air as it is vaporized, prior to the second heating and expansion, is used to condense the working fluid of an organic Rankine cycle to make additional power or used as a cooling source in a district energy cooling system, or for the support of other refrigeration needs. Typically, the heat added to the system is from the exhaust of a gas turbine.

The OLAES system produces about 1.7 times as much power from the same amount of liquid air compared to the traditional LAES system with a regenerator and thus a corresponding increase in net operating review.
The heat rate of the OLAES system ranges from about 3200 BTU/KW-HR to 4500 BTU-KW-HR with an energy ratio (on-peak produced electrical energy/off-peak energy consumed) between about .75 and 1.4, depending on the cycle configuration, heat source, and operating pressures and temperatures. Energy density ranges from about 380 to 420 KW-HR per cubic meter of stored liquid air.  

The primary revenue stream from the OLAES system is the sale of the produced electricity. The major operating costs are fuel and the cost of the excess renewable power used to produce the liquid air. There is a potential for additional revenue streams. As the penetration of renewable energy on the grid increases there will be an increasing need for what is known as “ancillary” grid services. These services include spinning reserve credits for electric power that can quickly respond to changes in demand (usually this means responding within 10 minutes), grid voltage and inertia support, and the providing of VARs (volt-amps reactive) to the grid for power factor correction. See the detailed description of the OLAES system for a more detailed discussion about ancillary services, how the OLAES system can provide these services, and overall economics.

Basic flow diagram of Just In Time Energy’s OLAES System

​

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

See the Technology Details Section for a more complete explanation of the OLAES system.


Combined Gas and Electric Storage
Just In Time Energy’s Combined Gas and Electric Storage (CEGS) system uses the same concept as the OLAES system except the working fluid is liquefied natural gas (LNG) instead of liquid air. Using excess renewable power, pipeline gas is converted to LNG and stored at off-peak times. The electric energy used to make the LNG is returned to the grid and the gas to the pipeline system at peak times. The returned gas flow rate can be 3 to 4 times more than the withdraw rate when producing the LNG, thus providing a high deliverability source of stored gas when fossil fueled generation (beyond that generated by the CEGS system) is called upon to backup renewable power.    

As the second expansion in this cycle is down to the pipeline system pressure rather than atmospheric pressure as with the OLAES System, heat rate is typically greater than that of OLAES system, but still well under 5500 BTU/KW-HR. The energy ratio varies between about .85 and 1.7. Energy density is about 270 KW-HR per cubic meter of stored LNG (2000 KW to over 2500 KW per KG/S of returned gas to the pipeline).
This system has two primary revenue streams – the value of the power returned to the grid and the value of moving the natural gas from off-peak to peak times. As with the OLAES system there is also the potential for ancillary grid services revenues.

​

​

​

​

​

​

​

​

​

​

​

 

 

See the Technology Details section for a more complete explanation of the CEGS system.

While the patented cycles are new, the components making up the OLAES and CEGS systems are well proven at the operating conditions required. Just In Time Energy has had support from the major manufactures of the key components with equipment selections and performance data for the gas turbines, hot gas expanders, cryogenic pumps, and heat exchangers.