Whitepaper

At O-Hx, we aim to transform industrial and commercial cooling. Our focus is on innovation, sustainability, and efficiency. Boasting over 50 years of combined expertise, we lead in thermal-energy-storage technology.

Furthermore, our team blends engineering know-how with financial insight. Also, we integrate business development and software innovation. As a result, we provide advanced solutions for today’s environmental challenges.

EnergiVault
FOREWORD

Cooling is at the very heart of modern life and its benefits, both seen and unseen, affect every part of society. That dependency is destined to grow further, adding to the global challenge of climate change. Because whilst cooling is crucial to everyday life – from keeping food fresh, vaccines usable and people healthy and comfortable – it is also highly energy intensive and environmentally damaging.

According to a joint report from the United Nations Environment Programme (UNEP) and the International Energy Agency (IEA):

“In a warming world, prosperity and civilisation depend more on access to cooling. The growing demand for cooling is creating more warming in a destructive feedback loop.’’

There are approximately 4 billion cooling devices in use around the world. The Green Cooling Initiative says that figure is growing by 10 devices every second and estimates it will reach 9.5bn by 2050. This rising demand for air conditioning, refrigeration and data centre cooling would result in a 90% increase in energy consumption and the associated environmental impact without mitigating action.

There is no single solution and it is widely accepted that a varied approach is required, including a reduction in demand through improved building design, better utility regulation and aggressive energy-efficiency strategies.

The Birmingham Energy Institute and the Institute for Global Innovation at the University of Birmingham addressed the issue in the report in A Cool World: Defining the Energy Conundrum of Cooling for All. Its key conclusions stressed that access to cooling is essential for meeting the world’s social and economic goals, but warned that unmanaged growth represents one of the biggest threats to achieving climate targets for CO2 emissions. It added that, if cooling is to be sustainable there is a need, not only for more efficient air conditioning and refrigeration, but also a fundamental overhaul of the way cooling is provided with a new needs-driven, system-level approach.

It is here that the technology behind the EnergiVault® can make a key contribution, by making cooling equipment more efficient and helping match high building loads without the need to consume electricity during peak times. This innovative Cold Thermal Energy Storage (CTES) solution is designed to optimise energy usage for chillers in industrial and commercial applications, and provide peak building load cover if required.

EnergiVault
THE RISE IN COOLING DEMAND

Demand for cooling is growing quickly, driven by factors such as climate change, the growth of urban areas, an expansion of the global middle class and higher incomes. A report from The Economist Intelligence Unit (EIU) estimates that annual global sales of air conditioning and refrigeration units will reach 460 million by 2030, compared to 336m in 2018.

Cooling in all its forms offers many crucial and wide-ranging benefits, including how fresh food and medicines are protected, how people stay healthy and comfortable in a warming world, and how critical facilities such as data centres and energy plants are maintained.

Rising temperatures from climate change are increasing the requirement for air conditioning in new markets, as are wealthier households, while the growth of urban areas is significant because cities, by their nature, tend to trap heat.

Environmental incubator and accelerator 350 PPM estimates that cooling technologies (including refrigeration, AC and heat pumps) account for 25-30% of global electricity consumption and 10% of global emissions. In the UK, the Carbon Trust says total refrigeration and cooling demand accounts for 16% of electricity consumption.

This demand must be met if countries are to meet the United Nations (UN) Environment Programme’s Sustainable Development Goals covering issues such as food security, health, inequality, education and employee productivity. But such rapid growth comes at a cost.

Cooling account for 20% of global power consumption and 10% of global emissions.

Refridgeration and cooling demand accounts for 16% of the UK's electricity consumption.

- According to the Carbon Trust

Cooling is a significant contributor to climate change, either directly through emissions from the use and leakage of refrigerants, or indirectly because equipment often operates on fossil fuel-based power. One of the key challenges, therefore, is that cooling is adding to climate change as well as being one of the things we most need to adapt to it.

Almost all cooling systems are powered by electricity, and the growth in cooling will intensify the demand on power grids. According to 2018 figures from the University of Birmingham, cooling equipment uses 4TWh of energy annually worldwide, around 3.5% of the total energy demand from all sources, and this is projected to rise by 90% by 2050.

Although grid-supplied electricity is steadily decarbonising in markets such as the UK through a move towards renewable energy, much of the world’s electricity is still generated by fossil fuels, resulting in increased CO2 emissions.

TECHNOLOGY
LANDSCAPE

Re-imagine the way we use and deliver cooling. In so doing we need to understand the portfolio of cooling needs, the size and location of multiple thermal, waste and ‘wrong-time’ energy resources available.

Professor Toby Peters 

Professor of the Cold Economy 

University of Birmingham

EnergiVault
ENERGY MONITORING INSIGHT

MITIGATING MEASURES

There has long been an acceptance that more must be done to combat climate change.

 

The Montreal Protocol was established in 1987 to regulate the production and consumption of ozone-depleting substances (ODS) used as refrigerants. However, many of the alternative hydrofluorocarbons (HFCs) introduced as a result had high global warming potential (GWP), leading to the Kyoto Protocol and Kigali Amendment to phase down their use.

 

On a wider scale, The Paris Agreement holds nations legally accountable for their efforts (or lack of) to tackle climate change, while the UN’s Sustainable Development Goals are a collection of 17 linked global targets designed to be a “shared blueprint for peace and prosperity for people and the planet’’.

 

A varied and concerted approach is clearly required to address the impact of cooling on the environment across all of these targets, as well as increased measures to reduce the energy consumption of cooling equipment and decarbonise buildings.

 

This includes improved building design and urban planning alongside the adoption of low GWP refrigerants in equipment and district cooling systems.

 

It also requires new equipment technologies while the improved management of existing devices can help the drive towards Improved efficiency. Incorporating energy storage into a cooling system can potentially reduce indirect emissions. Without storage, cooling equipment has to run to meet demand, even when conditions are not optimal.

 

By separating when energy is imported, or when cooling is generated, from when cooling is used, efficient energy storage enables conventional equipment to be run under non-optimal conditions for less of the time. 

 

Different types of technologies can be applied to reduce the cooling industry’s impact on the environment.

COOLING NETWORKS

Cooling networks produce and distribute cooling energy through a chilled water network to cool buildings.

COOLING DEMAND REDUCTION

Reducing a building’s total cooling load through architectural design, such as shaded areas.

THERMAL ENERGY STORAGE

A system to store energy generated during off-peak hours to be used later during peak demand.

ALTERNATIVE COOLING METHODS

Of which there are many, including air conditioning, and chilled water systems.

ENERGY RECOVERY

Re-use waste energy from one part of the system to part heat or cool elsewhere in the same system or premises

SUSTAINABLE ELECTRICITY

Includes 4 main options: wind power, solar power, bioenergy and hydroelectric including tidal energy.

EnergiVault
THE UK ENERGY SUPPLY

The majority of cooling applications in the UK utilise electricity in some form. With no single solution to reducing the impact of the cooling sector on the environment, the UK’s energy providers have been working towards a more sustainable provision of energy for some time, increasing renewable sources such as wind, solar and tidal.

At 7am on Friday 21 April 2017, the UK was operating without coal power for the first time since the 1880s. However, coal power is still used to some extent, underlining that the provision of ‘green’ energy is at nature’s mercy. Wind and solar are not at constant supply levels, so relying on that energy source is not always possible.

Carbon intensity is an important indicator of the environmental impact the energy we use is having in the UK. It provides a measure of how ‘clean’ our electricity supply is by indicating the grams of carbon dioxide released to produce 1 kilowatt hour of electricity.

It can be assumed that the more demand on the grid, at a time typified as a peak, the more carbon intensive the electricity supply would be. This, however is not always the case. As mentioned earlier, renewable energy can fluctuate quite a lot in terms of generation, and sources such as wind, hydro and solar will vary not only day-by-day, but also hour-by-hour and month-by-month. 

Patterns of electricity use are, by contrast, quite clear to see; UK energy consumption generally peaks between 07:00 and 18:00 each weekday. Renewable sources are prioritised by the simple fact that as supply increases because it is a windy day, for example, then we use more wind-generated electricity to meet demand and lessen fossil fuel use. Generally, the energy source used to balance demand is natural gas.

As more capacity builds in the network for renewable provision, reliance on carbon intensive fossil fuels will decrease. But for the moment, further challenges for improving the physical network need to be overcome to prevent thermal constraints, which are ‘energy bottlenecks’. If demand is greater than network capabilities, then bottlenecks occur.

In addition, when renewable energy and embedded energy generation is high, bottlenecks can also occur because of the increasing amount of energy the network has to carry. Managing this thermal constraint can cost on average approximately £30 million per month.

The Operability Strategy Report from the National Grid shows that by 2030, some areas of the network will see peak power flows which are 400% greater than the current capability

Cooling load in relation to energy consumption.

Focus on renewable energy sources and carbon intensity has given rise to 30-minute monitoring of our energy supply, with interactive dashboards and data feeds available from network operators.

 

For the average consumer, this level of information, if harnessed correctly, allows decisions to be made when it is more environmentally friendly and cheaper to operate certain appliances, charge electric vehicles and carry out certain tasks.

 

On a commercial or industrial scale, this pattern of variation is not always possible. In the cooling sector, demand is usually attributed to higher ambient temperatures, which generally occur in the middle of the day and coincide with peak energy consumption.

The Department for Business Energy and Industrial Strategy (BEIS), 2021 Cooling in the UK report highlights that even with localised renewable energy generation from solar panels, the supply and demand peaks vary at different points in the day. Furthermore, as already outlined, the amount of solar generation or wind generated electricity fluctuates greatly.

An ability to automatically and flexibly respond to unpredictable electricity supply conditions, and match this to operational demands, would significantly enhance grid efficiency.

While adding local renewable energy sources to buildings or cooling plant does help to reduce the reliance on the grid and, in turn, fossil fuels, it is not currently a comprehensive enough solution to make any viable impact.

The relationship of energy consumption and production costs across a typical day in the UK.  Source: Cooling in the UK, BEIS 2021

This level of information allows decisions to be made when it is more environmentally friendly and cheaper to operate certain appliances, charge electric vehicles and carry out certain tasks.

EnergiVault
ENERGY STORAGE

Energivault - Thermal energy storage

Energy storage for cooling is available in a variety of forms.

This can be one of the most effective methods of negating the effects on the environment of high loads during peak energy periods,and can be approached in two different ways.

1. Store the electrical energy, captured when network demand is low, to be used when required to power cooling plant.

2. Store the thermal energy, generated when network demand is low, to be used when required.

The first solution. Involves the use of electrochemical batteries,

such as the typical lithium-ion examples in everyday use, which feature a chemical material called an electrolyte. When electrons move from the cathode (+) to the electrode (-), the battery is charged and the chemical potential energy is increased. When discharging, the opposite takes effect.

Lithium batteries degrade over time, losing energy capacity.

It is suggested that when lithium batteries are used as energy storage systems on a large scale, they will need to be replaced roughly every 8-10 years, which can be a costly process, especially when replacing larger industrial variations. These batteries would power cooling plant such as a chiller directly, either taking the place of the supply from the grid or supplementing it.

Sensible heat

Sensible heat is a term used to describe a change in enthalpy by absorbing or rejecting energy causing a temperature change at a given pressure. For example, one kg of water, which is the weight of one litre of water, will require 4.186 kJ of energy to raise its temperature by 1oC at atmospheric pressure. Similarly, it will be required to reject 4.186 kJ of energy to decrease by 1oC. The phase of the water does not change, it would remain as a liquid between 0 and 100oC

Latent heat, or latent heat of fusion

Latent heat, or latent heat of fusion, describes the change in enthalpy of a substance by absorbing or rejecting energy, causing a phase change at a given pressure. Once water reaches 0oC it needs to reject 333.5 kJ/kg to turn from a liquid to a solid, or in this case, ice. No temperature change occurs, but energy transfer is still present.

Comparison based on 2.4MWh of cooling per day, discharged over 1 hour with 20 year life.

CTES (cold thermal energy storage) BESS (battery energy storage system)

From a design aspect, if a sensible energy store was to be used, then a large amount of liquid would be needed to harness enough energy to meet the demand. Furthermore, the changes of volume and therefore pressure with temperature change also need to be factored into design. If a phase change energy store was to be used, then almost 80 times the amount of energy could be absorbed or rejected by ice than it could the same weight of liquid.

Rate of energy transfer

Ice has been used as a CTES for centuries, dating back to the early Egyptians who used rapid evaporative cooling to generate their ice. Its applications now vary greatly, but one challenge remains unchanged – how do we cool items quickly? In the agricultural and food sectors, blast chilling can take place, reducing produce temperature rapidly. However, on fishing vessels such mechanical plant is not normally available and ice is used to chill produce quickly, preserving its quality and stopping it from spoiling during long trips.

Lithium batteries degrade over time, losing energy capacity.

It is suggested that when lithium batteries are used as energy storage systems on a large scale, they will need to be replaced roughly every 8-10 years, which can be a costly process, especially when replacing larger industrial variations. These batteries would power cooling plant such as a chiller directly, either taking the place of the supply from the grid or supplementing it.

It has already been established that ice can absorb a lot of energy, relatively speaking, but the available surface area of the ice plays a large part in how quickly that energy can be absorbed and the rate of temperature reduction, therefore, of the fish. Therefore, you regularly see fish covered or layered in ice shards, but rarely see one laid on a block of ice. The same principles of CTES can also be applied to cooling liquids – fluids that can be used for process cooling or for comfort cooling. A building’s chiller would normally circulate chilled water or ‘heat transfer fluid’ around a building serving evaporators of varying purposes. If the heat transfer fluid came into contact with ice, then its temperature would potentially reduce and either increase its energy absorption capabilities or reduce the amount of work the building’s chiller would have to do to reduce its temperature again. The greater surface area of ice that the heat transfer fluid comes into contact with, the more energy is transferred and the greater the cooling effect.

Creating a CTES requires the designer to select a phase change material, this being the substance that will be stored and used to cool down the secondary fluid, or produce. Two main choices exist, utilising sensible heat exchange or latent heat exchange.

It is here that the design of the CTES is crucial. How can ice crystallisation be maintained, without forming a solid block and therefore reducing the contact surface area?

EnergiVault
ENERGIVAULT® OVERVIEW

To provide an insight into the capabilities and operation of a CTES, the EnergiVault® is a leading example of how energy can be harnessed when at its cheapest and most environmentally friendly, and assist existing chilled water systems in becoming more cost-effective, raising overall efficiencies.

The EnergiVault® consists of a charger and thermal battery; it generally integrates with an existing chiller but can provide cooling on its own.

The system’s charger is designed and calibrated to provide evaporating temperatures set according to the fluid (heat transfer fluid) circulating in the buildings existing cooling system. Its tolerance is set to reduce the temperature and, therefore, the energy of the heat transfer fluid until ice crystals begin to form, creating a working fluid of ice slurry.

The ratio of solid phase matter to liquid phase matter is critical in this ice slurry as this mix is the difference between an ice slurry and a structure that is no longer fluid. As previously discussed, the EnergiVault® must maintain a working fluid to maintain a high heat exchange area. Therefore, the ice crystals are kept between 0.1 and 1mm to maintain fluidity and take the shape of a perfectly spherical crystal to avoid the clumping typically found in dendritic crystals.

The ice slurry is stored within a large thermal vessel, and an interface heat exchanger is used to discharge the cooling into the working fluid. A simple blending valve allows the integration of the EnergiVault® into any existing chiller. The blending valve either supports the current chiller operation by adding a controllable amount of additional cooling or is positioned to provide 100% cooling capabilities.

EnergiVault®️
Thermal Battery

Cooling capacity

The overall control strategies of EnergiVault® can become quite extensive, as described later, but here we focus on its primary purpose, how does the EnergiVault® know its thermal store is ‘charged’? As ice crystals form, the amount of ice slurry within the cylinders increases, meaning less working fluid. The working fluid is of greater density than the ice crystals, and therefore the weight of the cylinder decreases. In contrast, as the amount of ice slurry decreases, the weight of the cylinder increases because of the increase in heat transfer fluid.

 

This weight change is monitored by load cells and configured to calculate the amount of cooling capacity in the thermal store and, in turn, the state of the ice slurry, leading to its agitation to maintain a working fluid rather than solidification. Note: Working fluid or heat transfer fluid is the medium that is cooled when in contact with the ice.

EnergiVault
TIME OF USE SHIFTING

CTES systems like EnergiVault® provide significant benefits when considering Time of Use, for the energy consumed to provide cooling – and as a complete backup cooling system.

A simple rule of thumb would be to utilise electricity during the night on a cheaper energy tariff to reduce the cost of operation. However, there are a lot of other factors that make EnergiVault® even more beneficial to the bill payer and the environment.

Scalable control strategies allow integration into existing systems and live external data. Numerous data points need to be monitored and assessed to map a complete system’s efficiency, operating costs and impact on the environment.

These include, but are not limited to:-

- Time of Use shifting

- Chiller optimisation

- High heat grade heat recovery

- Low heat grade heat recovery

- SolarPV (local energy generation)

- Energy monitoring insight

EnergiVault
CHILLER OPTIMISATION

Existing chiller efficiencies and performance

By the nature of their design, chillers fluctuate their capacity and required input power depending on high ambient temperature or high heat rejection water circuit temperature. In addition, the load percentage in relation to the chiller capacity also holds a significant impact.

As ambient temperatures increase for air-to-water systems, or water rejection circuit temperature increases for water-to-water systems, maintaining energy exchange becomes increasingly difficult with higher operating pressures of the refrigeration circuit required and, therefore, a higher electricity consumption. Furthermore, as the load fluctuates away from the system design conditions, the chiller’s efficiency reduces as the load gets less.

Inverter control and the staging of chiller modules can reduce the amount of system efficiency decrease, but it is still an unavoidable consequence.

Energy cost and carbon intensity

Introduced earlier, the cost of energy production and the carbon intensity of our electricity supply fluctuate daily or even hour by hour. The cost of electricity supply per kWh becomes less as the national grid does not have to import as much electricity when demand falls. What is more, the carbon intensity of the supply fluctuates and becomes more environmentally friendly as the grid can use more renewable energy.

LOW GRADE AND HIGH GRADE ENERGY RECOVERY OPTIONS

With every cooling process, the by-product is ‘waste heat’, and the cooling process of the EnergiVault® is no different. As heat energy is removed from the parent fluid circulating around a building to form ice slurry, the waste heat is rejected into ambient air, typically at the condenser. Whilst remaining reusable energy, it is lost from the system. To maximise system efficiencies and add further weight to the cost and environmental savings, this waste heat can be utilised to generate hot water, space heating and other process heat requirements.

Both high (100oC) and low (40oC) grade heat generation is possible with multiple storage options to harness the heat recovery potential, decoupling from the EnergiVault® charging process, for flexible, on-demand, use.

EnergiVault
SOLAR PV INTEGRATION

Premises, such as food production factories, with large renewable energy generation systems can benefit end users through operation cost reductions. Usually, the Distribution Network Operator (DNO) will limit the amount of electricity that can be exported to the grid to avoid a surplus supply when demand is low. Still, with EnergiVault®, this complication can be removed.

By integrating on-site generation, such as solar PV and wind turbines, EnergiVault® can adjust its charging period to maximise the consumption of energy that is being generated on-site. In addition, it displaces high-cost grid- imported electricity at peak times.

EnergiVault
ENERGY MONITORING INSIGHT

How to maximise all the possible energy saving benefits:.

  • Produce a system that can untegrate with existing installations and monitor its performance and that of the existing system(s).
  • A solution that can adjust third-party setpoints depending on load requirements and judge efficiencies with enough intelligence to maximise them by completing the takeover of demand or providing supplementary cooling.

Monitoring half-hour energy supply data allows the judgement of:

  • When to charge the EnergiVault®,
  • When to turn existing chillers off, and
  • when to operate in unison.

Additional benefits are found by coordinating with renewable energy generated onsite, through solar, wind or combined heat and power – utilising ‘free energy’ rather than exporting into the grid.

There is no single solution to solving the energy crisis we are currently experiencing. However, EnergiVault® provides a comprehensive method for negating the effects on operating costs whilst reducing environmental impact.

EnergiVault
ECONOMIC AND ENVIRONMENTAL PROPOSALS

EnergiVault® is designed to be scalable according to site and financial requirements and therefore both environmental and operational cost benefits are variable. We estimate that by operating EnergiVault® alongside an existing chiller installation, savings of up to 69% can be realised against site cooling costs with up to 64% reduction of CO2 emissions.

Plug and play style integration provides an ideal model to create a system that will offer chiller optimisation, and forecasting through energy monitoring insight, Time of Use shifting, water production through heat recovery and power generation with solar PV.

With an estimated purchase price of £250,000 a payback time of 1.8* years can be realised.

EnergiVault
ENERGIVAULT® VS ADDITIONAL CHILLERS

Increased peak cooling loads generally mean adding more chiller modules to a cooling system, but is increasing chiller capacity the right solution? With EnergiVault®, reduced risks of production shutdowns, spoiled products, or compliance issues can be negated due to the benefit from additional chiller capability.

However; the additional added benefits of ToU shifting, chiller optimisation, heat recovery, and energy monitoring insight optimisation can be applied to the site's entire cooling plant, gaining significant financial and environmental benefits. In addition, the trickle charge nature of operation of EnergiVault® reduces the requirement for facility upgrades or potential additional operating costs from the grid network.

EnergiVault
ENERGIVAULT® TRIAL DELIVERS PEAK PERFORMANCE

Full-scale testing of the EnergiVault® cold thermal energy storage system from Organic Heat Exchangers (O-Hx) has seen performance exceed expectations in areas including peak load support, resilience and reliability.

A commercial demonstration unit installed at the Alnwick facility of drug development and manufacturing accelerator Quotient Sciences earlier this year, with benefits to date including:

  • Economic savings from charging with cheaper overnight electricity and from efficient trickle charge of the battery to replace inefficient chiller cycling.
  • Continuity of operations under high temperatures / humidity, when previously cooling demand could not be supported by existing systems.

Resilience from always having cold energy stored on site, in case of core system failure or shut-down

Bob Long, O-Hx, Executive Chairman and founder, said: “EnergiVault® has revelled in the high summer temperatures, displaying the ability to deliver huge amounts of thermal energy in support of struggling cooling equipment. We continue full-scale testing at Quotient Sciences, where our performance expectations were surpassed on many levels, including peak load support, resilience and reliability. With high confidence from this unit, commercialisation plans are now in place to be able to meet anticipated demand.’’

Stuart Munro, Head of Facilities at Quotient Sciences (Alnwick), added: ”O-Hx have been extremely professional, taking their proof- of-concept to a working unit that is now helping to support our site cooling demands. They managed to do all this without causing any disruption to our business.

“Quotient Sciences is committed to reducing its carbon footprint and energy consumption at every opportunity. It is innovations such as the EnergiVault® and engineers committed to change that our planet needs now.’’

Further Information about EnergiVault

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