F-gas phase-down timeline and CO₂ transition
UK F-Gas Regulation phases down HFC refrigerants by GWP. R404A (GWP 3,922): banned for maintenance use since 2020. R410A: phased down through 2025-2030. 2030 target: F-gas volumes at 21% of 2009 baseline. For large UK cold stores (above 1,000 kW cooling load): CO₂ transcritical (R744, GWP 1) is the primary replacement. CO₂ systems are essentially exempt from F-gas phase-down — future-proofed for the 2030 and beyond regulatory environment.
CO₂ transcritical electrical load profile
CO₂ transcritical systems use more electricity than equivalent HFC at ambient above 25°C (transcritical threshold). Below 10°C (UK winter): CO₂ at 90-100% efficiency, lower electrical consumption per kW cooling than HFC. Summer above 25°C: CO₂ 15-25% higher electrical consumption than equivalent HFC. Annual average UK: CO₂ systems use 8-12% more electricity than HFC equivalents. This means: solar PV systems should be sized slightly larger for CO₂ cold stores than equivalent HFC facilities to maintain the same self-consumption ratio.
Solar PV sizing for CO₂ transcritical cold stores
Self-consumption baseline: 88-94% (slightly below HFC equivalent of 90-96% due to summer electrical demand coinciding with peak PV output). Recommended sizing: system sized to winter baseload (peak self-consumption) rather than summer average. For 500 kW cooling capacity CO₂ store: 300-350 kW PV gives 92-95% self-consumption and 3.8-4.5yr payback. 400-500 kW PV gives 86-90% self-consumption with higher export. Optimal: 350-400 kW PV with battery peak-shifting for most UK CO₂ cold stores.
Heat recovery and battery storage with CO₂ systems
CO₂ transcritical gas cooler heat recovery (25-40°C lift over ambient): use for space heating, hot water, underfloor heating in dispatch. Heat recovery reduces total site energy 15-25%. Combined CO₂ heat recovery + solar PV approaches net zero operational energy for refrigeration and space heating scope. Battery storage for night setback: CO₂ cold stores run harder at night (cooler ambient — pulldown). 250-500 kWh battery sized to cover 4-6 hours evening pulldown: significantly improves total renewable contribution and reduces peak grid demand charges. Battery payback in CO₂ cold store context: 5-7 years.
Common questions
Does CO₂ transcritical refrigeration use more electricity than HFC?
At UK ambient above 25°C, CO₂ transcritical uses 15-25% more electricity than equivalent HFC. Below 10°C, CO₂ can be more efficient. Annual average: 8-12% more electricity at UK sites. Solar PV should be sized slightly larger for CO₂ cold stores to maintain the same self-consumption ratio as equivalent HFC facilities.
Can solar PV be sized to offset the CO₂ summer electrical peak?
Yes — the CO₂ summer peak coincides with peak solar generation. In practice, summer self-consumption for CO₂ cold stores is 85-92% (slightly lower than HFC 88-95%) because the CO₂ system's additional demand doesn't fully absorb additional solar generation on hot days. We model CO₂ load profiles specifically in our solar sizing calculations.