How EnergiVault® is redefining the possibilities of thermal energy storage

How EnergiVault is redefining the possibilities of thermal energy storage

Bob Long, founder and Executive Chairman of Organic Heat Exchangers (OHx), explains why its EnergiVault® cold thermal energy storage system ticks all the right boxes for reducing energy costs, cutting carbon emissions and improving operational resilience.

The global demand for cooling, already a huge burden on electrical grids, continues to grow, driven by factors including climate change and the growth of urban areas. The need for new ways to store energy to help meet this demand and reduce the cooling industry’s impact on the environment was behind the creation of O-Hx in 2016.

Most modern cooling is powered by electricity and energy providers are working towards providing a more sustainable supply. Renewable energy levels are not yet able to meet baseload demand, however, and this presents a considerable obstacle to decarbonisation.

Carbon intensity is an indicator of how clean our electricity is, measuring how many grams of carbon dioxide (CO₂) are released to produce a kilowatt hour (kWh) of electricity. Electricity generated using fossil fuels is highly carbon intensive because the production process creates CO₂. Renewable energy has a much smaller carbon intensity value (often zero) because its production results in far fewer emissions.

The globally patented EnergiVault® from O-Hx is an innovative bolt-on cold thermal energy storage (CTES) system that adds a wide range of benefits to industrial and commercial chiller operations. This makes it an ideal partner for both space and process cooling, including the food chain, pharmaceutical, healthcare, data centres and other sectors. Crucially, it uses artificial intelligence to access the electricity supply at low tariffs and at periods of low carbon intensity, reducing both energy costs and environmental impact.

EnergiVault enables conventional chilled water systems to reach their full potential by offering:

  • The ability to overcome site power limitations
  • High peak cooling versus input power
  • Ultrafast response to cooling demand
  • No lifetime degradation
  • >20-year battery lifetime

How it works

EnergiVault® consists of a charger and thermal energy store, or battery, an insulated container available in 1MWht capacity units which are modular and fully scalable. The system can be used alongside an existing chilled water system, on its own, or in place of an additional chiller. As with a chiller added to meet increased peak cooling loads, it can reduce the risk of production or building shutdowns, while additional features such as time of use (ToU) shifting, chiller optimisation, heat recovery and energy monitoring can be applied across a site’s entire cooling plant.

The system’s ice crystalliser charges the battery by converting the heat transfer fluid (HTF), typically a water/glycol mix, into spherical ice crystals a fraction of a millimetre in diameter, each surrounded by a film of organic material. This binary ice acts as the phase change material (PCM), delivering a massive increase in the surface area over which thermal transfer takes place.

The energy exchange rate of a single block of ice would be lower than that found with multiple shards of ice, or an ice slurry. Each crystal has 66% useable energy in relation to its volume when stored inside the thermal battery and takes the shape of a perfectly spherical crystal to avoid the clumping typically found in dendritic crystals. The spheres are surrounded by a parent fluid specially formulated with a freezing point below the ice sphere it supports, thus inhibiting fusion while in storage.

Other phase change batteries have the limitation of a low discharge rate because of the surface area to volume ratio and cannot always meet a required load. By maintaining an ice slurry as its thermal store, EnergiVault® increases the range of energy transfer at any given time.

A standard 1MWht unit has a modulation range of 0-500kWt and can deliver 200kWt of cooling for 5 hours. Its rapid response capability means it can go from 0 to 200kWt rated cooling power in two minutes.

Recent developments have seen O-Hx further optimise the thermal battery, achieving an impressive 25% increase in its storage capacity, while significant cost reductions make this cutting-edge technology more accessible and financially attractive.

We are not just redesigning; we are redefining what is possible in thermal energy storage. The resulting improvements in efficiency and affordability translate into a quicker return on investment for customers, aligning economic benefits even more closely with sustainability goals.

EnergiVault® integrates seamlessly with existing chilled water circuits and building management systems. It collects data from the national grid and optimises to use low carbon intensity energy and cheaper energy tariffs.

How it saves money

CTES systems like EnergiVault provide real benefits when considering ToU shifting for the energy consumed to provide cooling. Taking advantage of the cheapest available tariff is the most obvious plus point, but there are numerous additional features that make EnergiVault® even more beneficial to both bill payer and the environment. EnergiVault® is running on the cheap energy of last night, deployed today to offset the client’s needs.

ToU shifting is one of EnergiVault’s scalable control strategies, which allows integration with existing systems and live external data. Applications such as food production factories with large renewable energy generation systems can benefit through operational cost reductions. By integrating on-site generation, such as solar PV or wind turbines, EnergiVault® can adjust its charging period to maximise the consumption of energy that is being generated, but not necessarily used, on site. It also displaces high-cost grid imported electricity at peak times.

With regard to heat recovery, as heat energy is removed from the HTF circulating around a building, the waste heat would typically be rejected into ambient air at the condenser. However, with EnergiVault® this waste heat can be utilised to generate hot water, space heating and other process heat requirements. Both high grade (100°C) and low grade (40°C) 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.

Energy Monitoring Insight

Maximising all possible energy savings requires a system that can fully integrate with existing installations and monitor all aspects of performance. EnergiVault® delivers 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 enables judgements on:

  • When to charge EnergiVault®
  • When to turn existing chillers off
  • When to operate in unison

EnergiVault® vs additional chiller

Although most commonly used alongside an existing chilled water system as outlined earlier, EnergiVault can also be deployed instead of an additional chiller. As with a chiller added to meet increased peak cooling loads, it can reduce the risk of shutdowns, spoiled produce or compliance issues, and boosts chiller capacity while avoiding the higher capital costs of under-utilised, peaking chillers. With many sites struggling to achieve the required power supply for multiple chiller installations, the system also delivers high-capacity cooling from low current input and high-capacity cooling when connection power is limited.


The modular design of EnergiVault offers significant advantages to any potential customer. It allows for scalable solutions tailored to varying cooling demands and site-specific requirements. This flexibility is vital for meeting the diverse needs of end users, ranging from industrial facilities to commercial spaces.

Clients are particularly interested in how multiple EnergiVault® units can be integrated into their existing systems to enhance efficiency, resilience, and sustainability. The ability to incrementally increase cooling capacity and energy storage aligns closely with the increasing demand for more adaptable and environmentally friendly cooling solutions.

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About Us

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

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