THE ROLE OF CRITICAL POWER SYSTEMS IN OUR JOURNEY TO NET ZERO
Power You Can Trust
Introduction
This opinion piece seeks to focus on the impact our transitional journey to net zero will have on “critical power systems” and what they could look like in an “all electric” future. The author considers some of the options currently available to reduce C02 emissions, such as:
• Using current technology to reduce emissions for new and existing infrastructure
• Current and potential future standby power options
• The impact of manufacturing and sourcing “alternative fuels” and how their production and distribution could impact emissions reductions
• The importance of the wholistic approach offered in ISO14064
• A case study of an electric critical infrastructure project
UK CRITICAL INFRASTRUCTURE
United Kingdom’s infrastructure is a complex network of systems and services that are essential for the country’s economic stability, security and quality of life. These elements are often referred to as Critical National Infrastructure (CNI) and include the following key sectors:
• Energy
• Transport
• Water
• Telecommunications
• Health
• Finance
• Food
• Government and Public Services
• Education
• Housing
The current UK government recently added Data Centres to the list of critical infrastructure. These infrastructure elements are interconnected and interdependent, forming the foundation of the nation’s economy and society. Ensuring their resilience, sustainability, and efficiency is vital for the country’s future growth and prosperity. Most if not all of the essential elements of these sectors will be grid powered but backed up in some way by a “critical power system” comprising of a UPS, standby diesel generator or typically both.
WHY ARE CRITICAL POWER SYSTEMS SO IMPORTANT?
Today most aspects of our lives are impacted by technology based around or in some way managed by IT and powered by electricity. It could be the humble traffic light system, the light we turn at home, the water we drink, the “news” feed on our mobile phone, the food we buy in the supermarket to the lifesaving procedures we might receive in hospital. All of these services are in some way delivered by means of electrical power with IT supporting the critical infrastructure.
For many years the UK National Grid has been dependent on coal, nuclear and gas power stations for the vast majority of its output. Coal and nuclear sources of power were considered to be “base load” generation with gas also being part base load and also flexible enough to help deal with short term “peak” load requirements. This mix has ensured a high level of grid stability.
The last decade has seen a massive push away from coal with the last station closing at the end of 2024. During this period much of the UK’s aging nuclear fleet has been decommissioned further reducing the amount of “base load” generation available to the grid. In this period we have seen a larger dependence on the use of gas but a really significant increase in “renewable” sources namely wind and solar.
Critical power systems, which typically include UPS and standby generators, have been a key part of part of our critical infrastructure for more than a century. Over that period there have been massive changes in both the technology used to make and operate these systems, the types of equipment they now protect and the range of critical applications to which they are put. Critical power systems are an integral part of our country’s critical infrastructure and are relied upon to provide power in the event of a grid failure. As we transit to a carbon zero future, more of the electrical power we use will be generated by wind, solar and other low emission sources. Maintaining the stability of the grid stability will be essential if we are to avoid either blackouts or grid instability. To safeguard against these eventualities, we must enhance our “critical power supply solutions”, but how do we make them more “green”?
The 2020’s has witnessed an explosion in the construction of hyperscale Data Centres all are currently backed up with UPS and standby diesel generating sets. The use of AI is predicted to grow exponential growth in the coming decade. Recent analysis by McKinsey’s suggests global demand for data centre capacity could rise at an annual rate of between 19 and 22 percent from 2023 to 2030 to reach an annual demand for power of 171 to 219 gigawatts (GW) all of which will be protected by UPS and standby diesel generation.
CURRENT AND POTENTIAL FUTURE STANDBY POWER OPTIONS
Here we consider current and solutions under development that can be built into new and future infrastructure. We also consider the limitations as we currently know them to be. These include:
• Battery energy storage systems (BESS) are available today and being installed mostly for grid stability applications and some data centre trials.
• More compact and efficient battery / chemical storage types under development such as thermal energy storage systems (TES).
• Mechanical Energy storage systems i.e. pumped water storage have been around for a long time. Compressed air storage and flywheels are also under development.
• Fuel Cells (natural gas or liquid H2) have been around for many years and have been used in critical power applications. The electrical capacity (rating) of these units remains limited at present.
• A new range of standby generator engines that can run on gases such as hydrogen rather than diesel or HVO alternatives. These engines are available today in ratings similar to their diesel alternative however they come with some limitations.
SOURCING CURRENT AND FUTURE FUELS
Today virtually all standby generators used in the provision of critical power systems are compression ignition diesel engines. Diesel engines are a mature technology which is continuing to respond to ever increasing emission reduction targets. They are favoured as:
- They are a largely mass-produced and “relatively inexpensive”.
They use fuel that is easily accessed. - They start quickly and have a good level of load acceptance, a prerequisite for a standby system.
The deployment of standby diesel generator as back up to critical installations continues to grow year on year particularly with significant growth currently coming from the Data Centre sector.
Internal combustion engines have the ability to burn a range of fuels such as diesel, natural gas, liquified natural gas (LNG), methane, land fill gas etc (Diesel compression ignition – gas spark ignition). Natural gas widely used in for example Combined Heat and Power (CHP) systems, with other locally sourced gases used on land fill and water treatment sites.
In this section we look at some possible alternative fuels for the standby generator market and any potential operational impact.
HYDROTREATED VEGATABLE OIL (HVO)
Hydrotreated Vegetable Oil (HVO) is available today and is being widely adopted particularly in the data centre market. HVO is a liquid fuel that is a paraffinic bio-based liquid fuel produced using a special hydrotreatment process.
The adoption of HVO (EN 15940) could translate into a widely claimed maximum 90% reduction in CO2 emissions over its entire lifecycle (1, 2 & 3). Production can be from recycled vegetable oils or fats that do not impact crop resources. Today most is manufactured from virgin vegetable oils, such as rapeseed, sunflower and palm oil removing them from the food chain. In the case of palm oil production, we know if to be responsible for widespread deforestation. First-generation biodiesels such as EN590 B7, which we currently use in road vehicles and standby generation, contains just 7% of bio content (mostly from crop sources).
HVO has a slightly higher energy density than fossil diesel by weight but, it has a lower energy density by volume. Recent tests results undertaken by an engine manufacturer indicate that engine fuel consumption by volume is higher 4% in l/hr (latest Rehlko (formally Kohler) test data).
THE CASE FOR AND AGAINST HYDROGEN (H2)
SOME FACTS ABOUT HYDROGEN
Hydrogen is very much lighter or less dense than natural gas, you need approximately 3 times the volume of hydrogen compared to natural gas to get the same amount of energy. Were we to transfer the gas grid overnight from natural gas to hydrogen it would need to run at approximately three times the pressure. Whilst the UK’s main gas pipe infrastructure will be hydrogen ready by 2033 there is no indication yet as to when the local distribution network will be upgraded. This would require an increase in the rating, capacity and frequency of the compression stations as the grid pressure is increased along with transmission losses.
There have been some local area trials of introducing a small % of hydrogen into the natural gas network which are reported to have been successful. It is generally thought that a mix off up to 20% hydrogen would not create issues in operating the domestic heating systems and cookers (Institution of Mechanical Engineers 14th Jan 2022) (4). To be able to use 100% hydrogen, new pipe infrastructure, boilers and cooking appliances would have to be installed – so the switch to a hydrogen grid would be a significant investment.
HYDROGEN PRODUCTION
At the end of 2021 of hydrogen produced globally:
- 47% from natural gas
- 27% from coal
- 22% from oil (as a by-product)
- Around 4% comes from electrolysis
Electricity had a global average renewable share of about 33%, meaning that only about 1% of global hydrogen output was “green” produced with renewable energy. The UK generates a significant amount of surplus wind power, particularly during periods of high wind. This surplus is often managed through a process called curtailment. In 2022, the UK generated:
- Approx 30% of its energy from renewables
- Wind contributing around 23% of the total generation
- Up to 6% of wind power was curtailed (5).
Electrolysers could generate hydrogen from water using “surplus electricity”. Electrolysers are expensive, hence running them only when electricity is cheap doesn’t make economic sense. There aren’t any current plans for the largescale installation of electrolysers making it unclear how much of a role hydrogen will play as we roll out new wind power projects.
Hydrogen’s low ambient temperature density results in a low energy per unit volume, which necessitates the development of advanced storage methods requiring significant investment.
The UK Government recently published “Clean Power 2030 Action Plan” which set out a plan for the large-scale production and distribution of both “blue” and “green” hydrogen (6). With significant wind power projects planned in the coming decades there is potential for a significant surplus capacity to be available for producing hydrogen.
OTHER GASES
Internal combustion engines can be adapted to run on a number of different types of gas such as land fill gas, methane, Liquid Petroleum Gas (LPG) or Liquefied Natural Gas (LNG). Depending on the gas selected derating of a generating set may be required as the calorific value of gases differ e.g. LPG – rating reduced by around 40%.
POTENTIAL IMPACT IN STANDBY GENERATION
Whilst using a gas mix may work for things such as domestic boilers it may not be the case for other more specialised equipment such as generator or CHP systems. To provide a consistent system output, gas engine performance is based on a specific gas or mix of gases. Engine mapping must be matched to the calorific value of the gas. To ensure the correct mix of fuel reaches the combustion chamber of a gas fuelled standby generating set or CHP would be to inject the gas into the fuel line locally.
In the short to medium term, it is difficult to see that there will be any real alternatives to the use of standby diesel generators emerging from the current field. The use of gas alternatives are possible but it will be down to the type of gas, how available it is, how it can be produced and distributed will be key to its successful adoption. Some large scale hyperscale data centre builders are considering micro grids and or Small Nuclear Reactors (SMR) but the space required for such solutions and hence potential adoption in the UK and across Europe is likely to be limited. With the limited operational hours run by standby generating sets, the relatively low cost of HVO verses the energy used to produce, distribute and store hydrogen locally could well offset their relative emissions impact (Scope 1, 2 and 3 emissions assessment).
Hydrogen is widely tipped as the future fuel of choice with a number of combustion engines manufacturers have brought gas (spark ignition) engines to the market, all of which are able to run on either natural gas, hydrogen or other specific gases. These gas-powered generating sets are available for standby generation or CHP systems at ratings equivalent to those of today’s diesel generators.
There are a number of drawbacks to this change:
- Start up and load acceptance performance is much slower than a diesel engine which will require changes;
- In the way loads are applied
- To various standards and guidance documents (i.e. BS ENISO8528 HTM06 etc.
Regardless of the fuel used, NOx will always be present in the exhaust if an internal combustion engine is used.
The way in which we produce, store and distribute hydrogen will need to be developed before widespread adoption will take place as the providers of critical infrastructure are usually mandated to provide services during prolonged periods without utility power:
- In Healthcare, HTM06 suggests a 200-hour contingency of diesel fuel. It would require over 50 tonnes of hydrogen to support an all-electric major teaching hospital for 48 hours.
- Data Centres typically require at least 48 hours of standby fuel.
Fuel cells or hydrogen fuel combustion engines produce no NOx or other harmful emissions but can only really be considered ‘green’ if they use “green hydrogen.
THE IMPORTANCE OF THE WHOLISTIC APPROACH OFFERED IN ISO14064
ISO 14064 (7) is an international standard for greenhouse gas (GHG) accounting and verification. It provides a framework for organisations to quantify, monitor, report and verify their GHG emissions. ISO 14064 aims to provide a consistent and transparent approach for organisations to measure and report their GHG emissions.
THE UK NATIONAL GRID
In 2023 transmission losses of the UK National Grid (8) were approximately 8% of all power produced or 25 TerraWatt hours. The 25 TerraWatts of losses need to be included in the UK’s Scope 2 calculation, proportioned according across existing business, infrastructure and must be considered when designing new infrastructure.
Note: It has not been possible to secure accurate data relating to the overall energy efficiency (% conversion efficiency) of the UK National Grid.
Traditional gas fired power stations operate with a thermal efficiency of around 35%. In 2022 the thermal efficiency of the UK’s gas fuelled combined cycle stations reach an overall efficiency of level 49% (9).
Interconnectors: The UK imported electricity through interconnectors with neighbouring countries the sources of generation are not declared (10).
The National Infrastructure report of February 2021 suggested that by 2030 65% of power generated should be from renewable sources leaving 35% being base load generation. With load on the National Grid set to increase (11), if grid stability to be maintained (at least into the mid-term) some of the inertia and short circuit capacity required will need to come from “base load generation”. With nuclear projects seemingly having such a long concept to grid connection time, then much of the base load generation required will continue to come from gas.
It is here then that micro grids could play their part with CHP included in that mix.
ALL ELECTRIC CRITICAL INFRASTRUCTURE
In this section the author offers an example of what an “all electric” hospital (12) could look like in the future and the importance of giving full consideration to the ISO14064 and scope 1,2 and 3 emissions.
In a recent case study paper by Schneider Electric it considered what an “all electric” hospital would like today and in 2040.
In the example a 2024 mixed fuel large hospital would have:
- Electrical load of around 16MW all supported by standby generation.
- Heating power is provided via gas boilers accounting for approximately 80-90% of the hospital’s gas usage: installed capacity is 18 MW.
In a 2040 “all electric version”
- Gas boilers are replaced by heat pumps and electric boilers – generator backed – total electrical load 36MW
The 16MW of standby generators required in the “today” scenario would need to be 36MW in the “all electric” scenario carrying with them
- Embedded carbon used in their production and manufacture (Scope 3) assessment
- Additionally, emissions from regular testing of the much larger standby generator installation (Scope 1)
The hospital cannot remove all its scope 1 emissions even if the standby generators are powered by HVO fuel. Over time some of the standby generation could be modified to run on hydrogen or other gases. It could introduce its own energy production using a “microgrid approach”. This could include PV, a wind turbine, battery energy storage (BESS) and a CHP system (future using hydrogen/other gases).
A number of NHS Trusts are looking to move away from the continued use of CHP systems in an effort to reduce their scope 1 emissions. In an “all electric” future, CHP systems are not currently being considered at all.
The inclusion of a CHP system in the example outlined above could:
- Reduce the number of generating sets required (depending on selected rating) reducing scope 3 emissions. Reduced scope 1 emissions resulting from testing of few generating sets.
- Whilst a large (+2MW) modern CHP system with a total operational efficiency of upwards of 85%would increase Scope 1 emissions, it offers a much higher level of efficiency than gas powered generation from the grid hence reducing overall emissions.
Adding solar panels, BESS and a wind turbine can further reduce scope 2 emissions. As we move forward we need to consider all emissions i.e. scope 1,2 and 3 rather than just Scope 1.
The micro grid approach has the potential to be more effective in areas such a large data centres where rejected heat from the engine of the CHP system can be used to feed evaporative cooling units.
CONCLUSION
The use of HVO can potential yield a 90% reduction in CO2 emission from a packaged standby generator solution (1,2).
Significant progress is required in the production, storage and distribution of hydrogen before it becomes a viable alternative to Diesel/ HVO especially for the UK’s critical infrastructure sites both existing and new.
Widespread adoption of fuel cells in standby applications is low due to the limited capacity of the devices themselves and the availability of hydrogen. Continued development of this solution is important as neither CO2 or NOx is emitted during use.
Large capacity batteries are currently being deploy as grid balancing devices, to mop up surplus wind capacity and on some early standby applications. Physical size (and cost) are major limitations on most UK sites.
Hydrogen will play a part in the UK’s transition away from fossil fuels and an all-electric future. Technology needs to be developed to lower costs associated with the production, storage and distribution of hydrogen such that supplies can be accessed close to the point of consumption. Either a separate hydrogen distribution network is constructed or a way needs to be found to ensure that there is a consistent gas mix right across the network.
For several days during the early part of 2025 wind power generation played a very minor role in the country’s energy production mix. It is essential, for our future energy security, to ensure that we have sufficient “alternative” sources, to cover those times when the wind doesn’t blow. Having idle plant isn’t financially viable be it gas, nuclear, solar or wind so we must find a way to ensure we don’t pay the same heavy price for idle plant as we currently do for wind power disconnections: all power generated must be efficiently and effectively used.
As we look to update existing infrastructure to reduce CO2 emissions, move towards an all-electric future and design and build the infrastructure of the future, it is vital that we embrace the tools and structure provided by ISO 14064 to ensure we made the correct choices. Fully considering all aspects of how we can maximise the energy efficiency of all our organisations, fully assessing the true CO2 impact of each decision.
ACKNOWLEDGEMENT
The author acknowledges the support and information provided by
- Rehlko (formally Kohler) Generators (FRANCE)
AUTHOR
G R Halliday
Business Consultant
WB Power Services Ltd
ENQUIRE NOW
