GREEN MATTERS
spherical ice crystals a fraction of a millimetre in diameter to avoid the ‘clumping’ typically found in dendritic crystals, each surrounded by a fi lm of organic material. This ice slurry acts as the phase change material (PCM), resulting in a huge increase of the surface area over which the thermal transfer takes place. This enables very high discharge rates, unlike solid ice technologies, and unlimited charge-discharge cycles. The thermal battery is an insulated container, available in up to 1MWh capacity units which are fully modular to meet demand. Because the charger and battery are independent, it is possible to have diff erent combinations of charger and store capacities to provide complete fl exibility to charge rate, total energy storage and discharge rate. A blending valve allows integration into any existing chilled water system. The valve either supports the current chiller operation by adding a controllable amount of additional cooling or is positioned to provide 100% cooling capabilities.
Timing is everything CTES systems can provide signifi cant benefi ts when considering the Time of Use (ToU) for the energy consumed to provide cooling. Using electricity during the night on a cheaper tariff is one way but there are other factors to consider.
Utilising a cloud-based AI optimisation engine ensures peak savings in electricity and carbon. The battery is “charged” by the refrigeration system using off -peak electricity, or locally generated renewable power, and then drawn down for use during high-tariff periods. ToU shifting is a scalable control strategies which allows integration with existing systems and live external data, enabling chiller optimisation, high and low heat grade heat recovery and solar PV (local energy generation).
We estimate that
integration with a chilled water system can provide approximately a 60% reduction in carbon emissions and in site cooling costs.
In addition to accessing electricity at its cheapest, the optimisation engine also enables the system to take advantage of periods of low carbon intensity on the grid, when more of the power is produced from renewable sources. Carbon intensity is an important indicator of the environmental impact of the energy we use. It provides a measure of how clean our energy supply is by indicating the amount of carbon dioxide released to produce 1 kilowatt hour (kWh) of electricity. The focus on renewable energy sources and carbon
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A schematic showing how EnergiVault integrates and compliments chillers within a building’s chilled water system.
intensity has given rise to 30-minute monitoring of our energy supply, with interactive dashboards and data feeds available from network operators. 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 driven by higher ambient temperatures, which generally occur in the middle of the day and coincide with peak energy consumption. Furthermore, the amount of solar generation or wind generated electricity fl uctuates greatly. An ability to automatically and fl exibly respond to unpredictable electricity supply conditions, and match this to operational demands signifi cantly enhances grid effi ciency.
Heat recovery and renewable integration As heat energy is removed from the heat transfer fl uid 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 effi ciencies 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 (100°C) and low (40°C) grade heat generation is possible with multiple storage options to harness the heat recovery potential, decoupling from the charging process for fl exible, on-demand use. By integrating on-site generation, such as solar PV or wind turbines, CTES systems can adjust the charging period to maximise the consumption of energy that is being generated on-site. As with the advantages outlined in ToU shifting, it again displaces high-cost grid imported electricity at peak times. Increasing the effi ciency of existing equipment and technologies is crucial in the drive to reduce both environmental impact and energy usage. The use of scalable thermal energy storage also has an important role to play as we develop new and improved ways to deliver cooling.
www.acr-news.com • July 2023 27
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