While researching the construction and operation of refrigerated ice rinks, I realized that there are essentially two main types of technologies for cooling ice: glycol systems and CO₂ systems.
Behind my question lay one main concern: is there a refrigeration solution that is less expensive than glycol? It seems so, but it is not very popular.
From what I understand, the vast majority of refrigerated ice rinks—here and elsewhere, indoor and outdoor—use a glycol heat transfer fluid (often ethylene or propylene glycol), a proven technology that has been in use for a long time.
The current standard: glycol (secondary fluid)
In almost all modern ice rinks, the principle is as follows:
- A primary refrigerant (often CO₂ or ammonia) circulates in the mechanical room.
- This refrigerant cools a secondary fluid, glycol.
- The glycol then circulates through pipes under the concrete slab and keeps the ice between –5°C and –9°C.
Why is glycol used?
- Non-toxic (in the case of propylene glycol)
- Stable
- Relatively low viscosity
- Low corrosiveness
- Easy to maintain
- Safer than ammonia in direct circuits under the slab
As a result, glycol has become the standard reference for refrigerated ice rinks.
The main (less common) alternative: CO₂
Direct CO₂ – a growing technology
Some new installations opt for a CO₂ system, either in a secondary or direct circuit. These systems generally offer:
- Very good energy performance
- Lower energy consumption compared to some conventional systems
- On the other hand, higher installation costs
- And greater technical complexity, requiring specialized expertise
This type of technology is beginning to be deployed in Quebec, especially in modern arenas and larger-scale projects. However, it is still uncommon for municipal outdoor rinks.
Mechanics for creating and maintaining ice
Comparison of the glycol system compared to CO₂
According to ChatGPT.
| Criteria | Glycol System (Secondary Fluid) | CO₂ System (Direct or Secondary) |
|---|---|---|
| Principle | A refrigerant (often ammonia or CO₂) cools a glycol circuit that circulates through the slab. | CO₂ is used as the primary refrigerant (and sometimes as a secondary fluid) and operates at higher pressures. |
| Technology Maturity | Very common, well-established technology; the standard for most refrigerated rinks. | Newer and growing technology, mainly used in arenas and large modern facilities. |
| Technical Complexity | Moderate complexity; many companies can install and maintain it. | Higher complexity (higher operating pressures, more sophisticated systems), fewer specialists available. |
| Installation Cost | Generally lower than CO₂ systems for equivalent performance. | Often higher installation cost (specialized equipment and more advanced engineering). |
| Energy Consumption | Good performance, though slightly less efficient than a high-end CO₂ system. | Very high energy efficiency, especially in well-optimized systems. |
| Servicing & Maintenance | Maintenance contracts easier to obtain; parts and expertise widely available. | More specialized maintenance; stronger dependence on a small number of suppliers. |
| Availability of Local Expertise | High: many regional firms are familiar with these systems. | More limited: mainly specialized firms, often located in major urban centers. |
| Suitable for a Small Municipality? | Yes — often the safest choice: proven technology with well-known risks. | Possible, but requires strong planning and a usage level that justifies the investment. |
| Risk of “Vendor Lock-in” | Relatively low: several companies can service these systems. | Higher: even if the system performs well, the municipality becomes more dependent on the original supplier. |
Comparisons of available cooling technologies
| Fluid | Main Role | State / Nature | Typical Use in a Rink | Advantages | Disadvantages / Limitations |
|---|---|---|---|---|---|
| Glycol (ethylene or propylene glycol) | Heat transfer fluid (secondary fluid) | Liquid | Circulates through the pipes under the slab to transfer cold to the ice surface. |
– Very common technology – Stable and relatively non-corrosive – Easy to maintain – Safer than direct ammonia systems |
– Does not produce cold itself (requires an upstream refrigeration system) – Viscosity at low temperatures → requires pumping |
| Freon (CFC / HCFC / HFC, e.g., R-22, R-134a…) | Refrigerant (primary fluid) | Refrigerant gas | Used in older refrigeration systems (compressors) to produce cold. |
– Historically widespread – Well-known technology among refrigeration technicians |
– Environmental impact (ozone depletion, greenhouse gases) – Many Freons are banned or being phased out – Gradually replaced by CO₂, ammonia, or other modern refrigerants |
| CO₂ (carbon dioxide, R-744) | Refrigerant (primary fluid, sometimes secondary) | Refrigerant gas | Used in modern systems (transcritical or cascade) to produce cold; sometimes also used in a secondary circuit. |
– Very high energy efficiency – Low environmental impact (very low GWP) – Well suited for modern installations |
– High operating pressures → more complex technology – Higher installation cost – Requires specialized expertise |
| Ammonia (NH₃, R-717) | Refrigerant (primary fluid) | Refrigerant gas | Used in many industrial and arena systems (often in the mechanical room, combined with a secondary fluid like glycol). |
– Excellent energy performance – Very low environmental impact – Well established in industrial refrigeration |
– Toxic and irritating → strict safety requirements – Less desirable for direct systems under the slab – Requires rigorous risk management |
En conclusion
It seems fairly clear that glycol remains the preferred solution. Relying on new technology when skilled labor to maintain it is scarce carries risks: maintenance costs can skyrocket and repair times can be lengthy in the event of a breakdown.
In my opinion, it is better to opt for a long-proven solution to avoid unpleasant surprises. This is especially true given that North Hatley does not have a large budget: it is therefore necessary to choose a simple and manageable approach to avoid unnecessary complications.
With that said, happy thinking!
