This study contrasts Chilled Water and Solid Ice Storage with EnergiVault, a hybrid solution securing the benefits of both systems whilst eliminating their performance limitations.
Cooling Flexibility
EnergiVault versus competing storage options
Feature | EnergiVault | Traditional Ice Tanks | Ice Bricks |
|---|---|---|---|
Energy density | High (slurry PCM) | Low | Medium |
Response speed | Instant | Slow | Moderate |
Footprint | Compact / modular | Large tanks | Modular |
Degradation | None | None | None |
Controls | Advanced optimisation-ready | Basic | Limited |
Use cases | Peak shaving, backup, optimisation | Load shifting | Load shifting |
- Poor discharge capacity - Low energy flexibility - Poor responsiveness to sudden cooling demand - Inefficient charging
- Poor temperature control - Low energy density - > 8x volume and higher footprint
- High capital cost - Limited lifecycles - Degradation over time - Low real turnaround efficiency - High-capacity connection - Storage without connected generation (Fault - Level) contribution; can add more generation instead
- Easy Integration with renewables to reduce energy and Co2 - High peak cooling versus input power - Ultrafast response to cooling demand - No lifetime degradation - >20- year lifetime - Highly scalable - Low footprint
Facilities managers and HVAC engineers are constantly searching for ways of reducing energy costs and carbon emissions through load shifting, load levelling and integration with on-site renewables.
A commonly used solution is chilled water storage, less common is solid ice storage.
Both these “cool storage” approaches can provide energy cost savings, reduce peak time non commodity costs such as transmission and distribution charges, provide peak cooling capacity and optimise on-site renewable generation, all in addition to back-up cooling for added resilience.
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Conventional CTES
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EnergiVault®
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Slow, low-power discharge
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Rapid, high-power cooling on demand
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Best for long-duration load shifting
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Built for peak shaving & fast response
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Limited role in resilience
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Supports N+1 and short-duration backup cooling
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Often oversized to meet peaks
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Reduces chiller and electrical oversizing
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Passive storage
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Active, controllable cooling asset
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However, both chilled water and solid ice storage systems have limitations which make them unattractive in many applications.
Chilled water systems are typically very large requiring huge volumes of chilled water with associated high chemical additive costs such as biocide and glycol. As the cooling comes from absorbing heat from the demand, the chilled water increases in temperature and returns to the storage tank, slowly increasing the storage temperature.
Solid ice storage has greater energy density than chilled water storage as it stores energy in the phase change between water and ice, however, the solid block of ice has limitations on cooling rates due to its limited surface are and therefore is not well suited to rapid cooling demands and responding quickly to short duration peaks, without being significantly oversized.
