Extreme cold: CO₂ cascade heat pump for −40°C ambient heating
Illustrative CO₂ (R744) + R515B cascade concept for district / industrial heating where fluorocarbon cascades lose capacity in deep cold.
Engineering data
- Case type
- Illustrative engineering example
- Data status
- illustrative
- Industry
- District heating
- Source temperature
- -40–-25°C
- Sink temperature
- 75–85°C
- Temperature lift
- ≈ 100 K
- Heating or cooling duty
- 150 kW
- Architecture
- CO₂ + R515B full cascade VCHP
- Result status
- Illustrative stable envelope near −40°C with engineered boiler backup
- Key risk
- Triple-point proximity in exceptional cold; need multi-energy redundancy; high discharge-side pressure design
- Existing system
- Gas / electric boiler peak + undersized air-source cascade
- Refrigerant
- R744 / R515B cascade
- COP
- 1.6–2.2
- Annual savings
- Illustrative ~40–55% operating-cost cut vs electric boiler (tariff-dependent)
- Estimated payback
- Illustrative 3–6 years
Project background
An anonymized northern industrial park needed reliable winter heat. Legacy fluorocarbon cascade units tripped or faded below about −25°C, forcing electric/gas boilers online for long hours.
Source / inputs
Design ambient −40°C. Sink 80°C-class hot water. Duty ~150 kW-class train. PLACEHOLDER numbers for screening only.
Heat pump solution
CO₂ low stage for deep-cold evaporation density + R515B high stage for useful leaving-water temperature; supervisory logic brings boiler peaking below envelope.
COP & savings
Illustrative COP ~2.0 at −25°C class points; ~1.6–1.9 near −30°C extremes—verify on rating sheet. Not measured field data.
Investment / ROI notes
Higher CAPEX than light commercial boxes; illustrative payback 3–6 years vs electric boiler under stated hours—site tariffs required.