Digital twins heat up the capabilities of energy storage plants

Engineering Industry News

Renewable natural gas (RNG), solar, wind and other sustainable resources are at
the core of decarbonisation and energy transition strategies. To effectively
support their large-scale adoption, it is necessary to ensure dispatchable
generation and predictable supply to the grid. Future-oriented energy storage
plants that leverage cutting-edge industrial automation, such as digital twin
technology, can succeed in this by taking advantage of accurate, real-time
simulation models.

Alan Messenger, Sales Director at Optimal Industrial Automation, looks at how to
support future energy security by enhancing energy storage with automated digital

Renewable energy sources, such as RNG, provide multiple benefits. In addition to
supporting ambitious decarbonisation and net zero goals, they also offer the most
economical way to create a decentralised power system. This, in turn, can help achieve
universal, reliable and affordable access to power.

For these reasons, the use of alternative energy sources is increasing in popularity,
representing almost 11% of power generated globally and forming a major part of the
energy mix in many counties. 1 For example, renewable energy use in Norway covered
more than 60% of total consumption in 2018. 2

One of the key challenges that must be overcome to support the increasing adoption of
renewable natural gas and other replenishable resources for power generation is
balancing fluctuating electricity demands with the intermittent nature of some green
sources. For example, to succeed in decarbonisation efforts and avoid any wastage, it
is essential to prevent curtailment. This occurs when a power generation system is
prevented from exporting to the grid, usually because of a temporary constraint caused
by congestion, essentially wasting potential low-carbon energy supplies.
The importance of advanced energy storage solutions
To fully utilise generation capacity, robust, reliable and highly efficient energy storage
solutions are required, as they can provide the level of flexibility needed to maintain stable and consistent supply to the grid. Strategies such as these can support peak shaving and load shifting activities.

Compressed-air energy storage (CAES) in its various thermo-mechanical forms, is
among the most promising technologies available at a commercial scale for high-
capacity energy management. By saving potential energy in the form of compressed air,
these systems are able to generate large amounts of power on demand.

Also, apart from access to a cavern, CAES facilities are not dependant on specific
geographies, unlike pumped hydropower, and their daily self-discharge is very low,
making it possible to effectively keep the stored energy for long periods without any
considerable losses. In addition, due to the well proven nature of the underlying
equipment, CAES plants typically have a designed lifetime of over 40 years, which
keeps the overall costs per unit of energy (or power), among the lowest for all available
storage technologies.

To achieve these results, CAES facilities can utilise different configurations, one being
the innovative liquid air energy storage method, which leverages thermo-mechanical
principles to advance the benefits of CAES. In the liquid air variant, air is purified and
cooled to its liquid state during the charge phase. It is then stored at cryogenic
temperatures and low pressure in suitable tanks. When discharged, the liquid air is
pumped to a high pressure, evaporated, and heated to expand the liquid air stream. The
resulting high-pressure gas drives a set of turbines in a power recovery unit.

Liquid air energy storage is the way forward

The liquid air energy storage cycle described above utilises components that are
commonly found in conventional power stations and industrial air separation plants.
Therefore, they offer multiple advantages. Firstly, they are well-proven and broadly
accepted. Secondly, this equipment is widely available to support commercial-scale
facilities. Finally, they have well-understood maintenance requirements.
Furthermore, the use of liquid air energy storage systems leads to energy densities that
can be up to 8.5 times higher than conventional compressed air alternatives. 3 Therefore
it is possible to create compact plants that are more economical, efficient, easier to
implement and suitable for sites with limited available space.

In addition, the power generation cycle eliminates the need for combustion and the
associated carbon emissions while also supporting ‘cold recycle’ practices. Waste heat
from the liquefier compressors is recovered within the process for highly efficient
operations and the storage and recycling of thermal energy released during discharge
3 Wang, S.X.; Xue, X.D.; Zhang, X.L.; Guo, J.; Zhou, Y.; Wang, J.J. (2015). The Application of Cryogens
in Liquid Fluid Energy Storage Systems. Physics Procedia, 67, 728–732. can be used as part of a closed-loop system to support air liquification activities during charging.

Automating energy storage process control

A liquid air energy storage process offers per se unique financial and environmental
benefits. Nonetheless, with temperatures ranging between -200 and +600 °C and
pressures reaching up to 200 bar, small variations in these can impact performance
significantly. This means that the optimum control of processing parameters throughout
the different phases is key. This is essential to maintaining energy efficiency and low
costs while maximising the end results.

By supporting real-time feedback and feedforward systems as well as remote
monitoring, industrial automation technologies provide an ideal solution to consistently
deliver peak performance and efficiency. More precisely, fully integrated automated
process control provides a highly available, responsive and secure framework for
monitoring and visualisation, trending and analysis as well as the management and
synchronisation of all pieces of electro-mechanical equipment onsite.

By using this type of automated setup, liquid air energy storage plant operators can
ensure the proper sequencing of all processes and promptly address any alarm to
maximise uptime, ultimately delivering high efficiency and productivity. As a result, it is
possible for facilities to realise dispatchable and predictable power distribution to the
grid while also maintaining a low – or even net zero – carbon footprint.

However, having precise control over operations to ensure optimum operations requires
an in-depth understanding of the process and the ways in which all components work
together and influence each other. Only in this way it is possible to effectively regulate
all activities. As liquid air energy storage facilities are relatively new, this insight may not
be readily available to plant managers.

Leveraging digital twin technology

Having a flexible automation setup that can support liquid air energy storage plants
while helping to develop process knowledge is a key resource. Moreover, the use of
advanced data analytics can enable the creation of an accurate and precise process
model known as a digital twin.

This offers a real-time virtual representation of a physical asset. It uses data generated
by sensors on the system as inputs and produces predictions about future behaviours. It
then turns this data into accurate, accessible and easily understandable information
formats for immediate insights. As more data becomes available, the digital twin can be
constantly updated to offer improved accuracy and additional capabilities. The most

immediate benefit of a such framework is the ability to organise all process information
and have a single, comprehensive process overview that allows for effective decision-

Digital twins empower operators to simulate different operating conditions and
scenarios, evaluating the system’s limitations without the need to run these in the
physical world. This, in turn, helps improve cost-effectiveness and safety. Consequently,
a digital twin application that encompasses all stages of a liquid air energy storage plant
is a key tool that can be used to enhance process modelling and understanding while
also enabling agile operations and driving continuous improvements. Furthermore,
these virtual representations can go even further, interacting with their physical
counterparts as cyber-physical systems (CPSs) to create even more proactive and
flexible setups.

To fully reap the benefits of the latest industrial automation solutions, such as advanced
process control and digital twins, energy storage facilities should partner with an expert
system integrator. This can address the specific needs of the sector and is equipped to
support innovative processing methods and technologies, delivering futureproof,
scalable solutions that can grow with a business as well as advance it.
A digital twin of the first full-scale UK liquid air energy storage facility
Highview Power, a global leader in long-duration energy storage solutions, is supporting
the global adoption of advanced cryogenic plants with its proprietary liquid air energy
storage technology. The company’s latest project is the construction of a 50 MW liquid
air energy storage facility (with a minimum of 250MWh) in Carrington Village, Greater
Manchester, UK.

Able to power approximately 200,000 homes for 6 hours a day, the plant will help
balance the supply and demand for renewables. To ensure successful operations at this
landmark facility, the company is collaborating closely with its automation and
technology development partner, Optimal Industrial Automation.

The automation system integrator has been supporting Highview Power since the
creation of the cryogenic energy storage specialist’s first pre-commercial scale
demonstration plant at the Pilsworth Landfill facility in Bury, Greater Manchester. Since
the automation requirements of this initial facility were unspecified, due to the unique
nature of the technology, an automation specialist that could ‘handle the unknown’ and
deliver a flexible solution was a must. Having already developed a proven system to
address these challenges, starting with the instrumentation requirements and through to
commissioning, Optimal was the obvious choice.

For its latest, larger project in Carrington, Highview Power was keen for the automated
system to feature a digital twin of the liquid air energy storage facility for use in training
and for marketing demonstrations. This would support the growth of good asset data,
which is key to the continuous improvement of the process model and an increasingly
detailed understanding. By doing so, the digital twin would ultimately support the
optimisation of this and future plants as well as futureproofing energy storage
operations, in line with the company’s digital transformation strategy.

To develop this cutting-edge solution, Optimal had to address a number of exacting
requirements. Firstly, the team had to select heavy-duty instruments that could
withstand the operating conditions at the liquid air energy storage plant. Secondly, it
was essential to create an automated setup that would be extremely accurate and
reliable in order to promptly identify and act upon any change in the key processing
parameters, such as temperature and pressure, while maximising plant efficiency,
performance and safety.

When looking at the parameters that the digital twin needed to account for, it was
necessary to enable it to interface with advanced mathematical models and simulation
software platforms in addition to the physical automation system. To address this level
of complexity, providing a solution that could support multithreading and multiprocessing
functions was crucial.

Thanks to its extensive expertise in building, integrating and optimising automation
systems for challenging and highly regulated industries, Optimal has a unique
knowledge of a wide range of vendors’ portfolios as well as the most suitable products
available on the market. With this insight, the company was able to leverage high-
performance components featuring world-class redundancy, availability, fault-tolerance
as well as maximum connectivity.

The automation system is now ready to support full operations at the Carrington facility.

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Press release from DMA Europa.

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