Premier class: R290 a standout for AC in high ambient temperatures

A recent technical workshop at the 27th Meeting of the Parties (MOP) to the Montreal Protocol in Dubai disclosed test results revealing that alternative refrigerant R290 (propane) outstrips the performance of widely used HFCs (hydrofluorocarbons) R22 and R410A in mini-split air conditioning systems.

Just a day after countries agreed to start formal negotiations over management of HFCs under the Montreal Protocol, the new test data confirms that the next generation of air conditioning products are in good hands when it comes to sustainable, energy efficient cooling in hot climates.

The report compiled by the Oak Ridge National Laboratory (ORNL) shows that climate-friendlier alternatives perform better than the stated HFCs, especially in high ambient temperatures.

Carrier Refrigeration provided the baseline equipment, specifically manufactured for high-ambient temperatures. The report titled “Alternative Refrigerant Evaluation for High-Ambient-Temperature Environments: R-22 and R-410A Alternatives for Mini-Split Air Conditioners” clearly puts R290 propane forward as the premier alternative refrigerant to R22 in mini-split systems.

R290 comes out on top: efficient, low-GWP, future proofed

R290 has a very low global warming potential (GWP) of just 3 compared to R22 (1,700) and R410A (2,088). On top of that, it was the only refrigerant to perform better than R22 at ambient temperatures of 27.8°C (82°F) and 35°C (95°F).

R290 achieved COPs of 3.85 and 3.30 in the stated temperature ranges, improving on R22’s by 11% and 7% respectively. Several synthetic blends from chemical producers Honeywell, Chemours and Arkema performed worse than both R22 and R290, in terms of both COP and capacity.

Other than the capacity of Arkema’s synthetic blend, R290 outstripped the alternative refrigerants in every other category and was the only refrigerant to achieve a higher COP than R22. In capacity, R290 rated 5.93, some 5% lower than R22.

Again at even higher ambient temperatures - 52°C (125.6°F) and 55°C (131°F) – R290 was the only alternative refrigerant to achieve a greater COP than R22, with gains of 7% and 8% respectively.

Importantly, the test results showed that all the refrigerants tested degraded in performance as the temperatures rose.

Further to that, the test results undersell the true efficiencies of R290 in that the alternative refrigerants were tested with existing air conditioners customised for R22 and R410A. For systems specifically designed for R290 it would be logical to expect the capacities and COPs to increase even further.

The ORNL results also showed that two synthetic compounds, R32 and DR-55, have better energy efficiency than R-410A at both medium and high ambient temperatures 125°F (52°C) yet both are significantly more environmentally harmful than R290, with GWPs of 650 and 698 respectively.

R290 systems are being rolled out in China and India already, and with delegates from high-ambient climates such as Saudi Arabia and Kuwait attending the meet, the message was very well received, with calls for more work to be done.

Some pointed out that while equipment performance looks excellent, challenges remain, including the need to develop safety standards and codes, ensure equipment availability, and train service technicians.

Conclusion: No future for R410A in hot climates

The Montreal Protocol mandates significant reductions in the production and use of R-22 by 2020. Yet, if very hot countries rely on R410A as a replacement for R22, rather than natural compounds like R290, they will lay new foundations for further regulation and be installing air conditioning systems that consume more energy than the next-generation products, have lower cooling capacities and present far greater harm to our atmosphere.

Report: Alternative refrigerants for R22 and R410A in AC