- Storing energy in compressed air has been around for decades, and has been used world-wide in many systems.
- When power is abundant and demand is low, it’s drawn from the grid to compress air into a salt cavern hundreds of metres underground. When the power is needed, the air is let out from the cavern to regenerate the electricity.
- Salt caverns have been used for many decades to store natural gas because not only are they naturally hermetic, but also salt undergoes plastic flow under pressure, so it seals any cracks that may occur. And what is safe for gas is safer for air.
- There are salt basins globally, in which caverns can be made cheaply and easily.
Both unique and well proven
Storelectric's CAES design is brings known sub-system
technologies, well proven at comparable scales, from other industries into
CAES. This equipment has been optimised over decades in highly comptetitive
situations, and made exceedingly reliable in difficult environments and extreme
conditions - so why re-invent the wheel? As Siemens said in the video, "The
components are available, the caverns are available, it does work and it will
work."
The main development work in this design lies in:
- Total
system design and integration
- Interfaces
between the sub-systems
- Control
and safety systems relating to these
This approach minimises development time, cost and risk,
while maximising overall system efficiency and reliability.
Currently our (pending) patents are all process IP which,
for which further information can be provided on request.
EXISTING CAES PLANTS
Huntorf, Lower Saxony, Germany
Compressed air energy storage (CAES) has been in operation
since 1978 in Huntorf in Germany, and since 1992 in McIntosh, Alabama, USA.
Both of these plants regenerate the electricity by feeding it into a gas-fired
power station, roughly tripling the efficiency of the power station.
When compressing the air, by the laws of thermodynamics it
heats up. When expanding it again, that heat needs putting back into the air.
Both Huntorf and McIntosh waste that heat, leading to only 42% overall
efficiency in Huntorf and 54% in McIntosh (the difference being because
McIntosh's power station is Combined Cycle).
McIntosh, Alabama, USA
Huntorf and McIntosh have proved useful additions to their
local grids, in operation daily. Storelectric has another technology, an
evolution these two plants, which can be retro-fitted to CCGT power stations
that are near appropriate geologies, which burns gas and has an efficiency
expected to be above 60%
There are three adiabatic CAES projects under way in America
since 1999: General Compression, Lightsail and SustainX. Despite combined
funding of $250m, since then they have only built just over 2MW in combined
demonstrator capacity, with significant technical, up-scaling and down-time
issues.
Storelectric's CAES Solution
In contrast to the existing CAES Plants, Storelectric has
several solutions, which will increase our efficiency from the 42/54% of the
existing plants to between 55-70% for a full-scale plant. We calculate that
these efficiencies give us significant margin for profitability, with the
First-of-a-Kind (FOAK) plants of both technologies offering strong double-digit
whole-project Internal Rates of Return (IRRs). This portfolio of technology
solutions enables us to configure each plant to the specific requirements of
each location and its load case and operating mode.
- Variant
1 (CCGT CAES) uses methane to heat the air and is a low cost conversion of
gas-fired CCGT or OCGT power stations to energy storage, which almost
halves emissions while adding storage related revenue streams, extending
the lives of the plants; round trip efficiencies are ~55-60% depending on
plant size (compared with up to 50% for existing CAES) and with durations
of 4 hours to many days;
- Variant
2 (TES CAES, licenced from TES CAES Technology Ltd) uses the heat stored
during compression (which the existing plants do not utilise) to heat the
air during expansion / generation. Emissions are zero and round trip
efficiencies are 60-70% depending on plant size, in the range 20MW to
multi-GW and sith durations of 4-12 hours.
The latter is fully green and the former uses less methane
than the original power station. These solutions can be hybridised (yielding a
very long duration storage plants with very low but not zero emissions,
extremely cost-effectively) and optimised depending on location, availability
of fuel, investor opportunity-risk profile and other factors.
Storelectric also has other innovations. By having 100%
renewable solutions, we already reduce the system's inertia and simplify it. No
research is required to achieve these benefits; however, in order to maintain
our technical lead, following successful installation and operation we will
also pursue a whole programme of R&D focused on increasing efficiency,
reducing capital and operating costs, and shortening lead times.
Our Variant 1 process allows the use of existing Combined
Cycle Gas Turbine (CCGT) technology for CAES. It consumes little over half the
gas of an equivalent-output CCGT and therefore almost halves the emissions, and
has most of the other benefits of electricity storage such as demand turn-up
capability. This is suitable for both new build and retro-fit, provided the
location has the right geology. The retro-fittable version can be seen as a
life extension of existing plants, in that their emissions reduction makes them
a much more attractive asset in the context of global emissions reduction
targets.
With our variant 2 (TES, licenced from TES CAES Technology
Ltd) we balance the heat over the entire cycle, storing the heat of compression
separately from the air, to be put back in during expansion / generation. This
results in a 68-70% efficient system (at 500MW) with no or very little gas burn
(depending on configuration) and hence emissions. Our plans include a future
R&D programme, which will work towards 75-85% round trip efficiency.
Both variants can be applied effectively at the distribution
and transmission levels, balancing the requirements of each part of the grid,
and as such can make maximum use of embedded and transmission benefits. All are
entirely compatible with global emissions reduction objectives.
Storelectric is currently investigating the potential of
using depleted North Sea oil and gas fields. This would improve security of
supply in a UK power sector with a high proportion of intermittent renewables.
Using existing North Sea oil and gas infrastructure, fully depreciated, would
be very cost effective. CAES provides a new use for such infrastructure,
avoiding or smoothing decommissioning costs. The scale of depleted oil and gas
fields would allow the creation of massive CAES facilities (100 TWh) that could
up and balance the entire UK electricity system. This could create an
engineering export opportunity for the UK in the many areas where oil & gas
deposits co-exist with renewable energy resources (e.g. Middle East, North
Africa, Central Asia). Offshore hydrogen versions of CAES are being developed
by Storelectric and top UK universities.Storelectric is at the forefront of a massive growth
opportunity and its approach allows it to stay ahead of the market for the
conceivable future.
Economics of CAES
All Storelectric's CAES solutions are built entirely of
known subsystems, proven at comparable scales and load cases.The whole project
IRR for the FOAK of both TES and CCGT configurations is expected to be in
double digits with up-side potential of as much as a further 15%, at all scales
from 20MW up to 100s of MW. The up-side potential is due to the conservative
assumptions used in those figures, and the evolution of the markets (volume,
price, spreads and market instruments).
A CAES plant can deliver into various revenue streams
including:
- Capacity
Market;
- Wholesale
markets / arbitrage;
- Balancing
services;
- Ancillary
services.
It can also deliver additional benefits for infrastructure
deferrals and replacements, which are currently unremunerated and therefore
assumed in our financial projections to generate zero revenues, and are also
mostly ignored in our assessments of potential up-sides to our revenues.
Nevertheless, they offer some further potential future up-sides to revenue
streams and hence profitability. They include:
- Storing
otherwise curtailed renewable generation;
- Enhancing
interconnector energy flows and profitability;
- Reducing
grid connection capital and revenue costs for renewables;
- Natural
power compensation, e.g. inertia and reactive power / load;
- Improving
the business case for CCGTs (our CCGT CAES variant).
Thus we have a >£1trn global market, strong current and
future revenues, low capital and operating costs and internal rates of return
on investment of between 10% and 27% without considering the above synergies.
We have mature market references and 3 main technology variants, of which we
can also do hybrids depending on the application and requirements. We also have
sites for our first plants.
As spreads between peak and off-peak prices, and price
volatility, grow with the increasing share of renewables on the grid, the
economics of power stations deteriorate. Meanwhile the economics of
Storelectric's CAES improve fast: according to industry forecasts,the IRR
(Internal Rate of Return on investment) above will be achievable solely by
arbitrage tradingeither by the time the first large plant starts trading, or
shortly after.
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