Researchers
at the Centre for Advanced Research in Building Science and Energy, CEPT
University, India, tested new super-efficient air conditioners and wrote this
report, aided by researchers at RMI and Lawrence Berkeley Labs. The coalition
of scientists in this effort is known as the Global Cooling Efficiency
Accelerator (GCEA).
The executive summary notes
that 20% of global building electricity use worldwide comes from air
conditioning, and AC is expected to be the second in electricity growth after
EVs by 2030. In India, the fastest growing AC market, it is expected that there
will be 1 billion room ACs by 2050, resulting in a 9-fold growth in power use,
stressing the grid. ACs that use highly efficient components, are optimized for
managing humidity, and incorporate low global warming potential (GWP)
refrigerants are expected to be the most efficient. Current testing standards
in relation to performance in humid environments need to be upgraded, according
to the report, mainly due to the energy requirements needed to adjust to high
humidity.
GCEA developed new standards
for humidity performance and began field testing in October 2023. They tested “seven
AC units from market-available typical and high-efficiency room AC models to
super-efficient room AC prototypes that are optimized for real-world conditions
and can manage humidity efficiently.” The testing requirements were set to
achieve a target temperature of 27°C and 60% relative humidity. The key
findings from the nine-month testing period are shown below.
Commercializing the
super-efficient AC units could reduce India’s power demand by 400GW (India’s
current total capacity) by 2050, the report found and worldwide with 3 billion
AC units expected to be in operation by 2050, the new units could reduce CO2
emissions by 68 gigatons (more than current annual global CO2 emissions now).
“ACs primarily cool the air through “sensible cooling,”
which lowers the air temperature. To a lesser extent ACs also dehumidify the
air in a process called latent cooling. However, today’s ACs are primarily
designed to manage temperature, not humidity, and their dehumidification
capabilities are limited. Most of an AC’s energy input goes toward sensible
cooling, leaving very little energy available for latent cooling. This energy
allocation is largely fixed, leaving users little control over improving the balance
between cooling and dehumidification. As a result, today’s ACs are inefficient
at managing humidity, leading to either discomfort or high energy bills for
people in hot humid climates.”
When AC units fail to control humidity, users tend to
over-run them to achieve desired comfort levels, resulting in higher energy
use. Current efficiency testing and ratings do not account for humidity
control. The researchers designed adjustable compressors, improved coil design
to better manage sensible and latent cooling loads, and added sensors and
control algorithms to detect loads and optimize the coil operation to ensure
efficient dehumidification. The innovations resulted in less energy use, lower
cost of ownership, and lower life cycle emissions.
GCEA identified four
intervention areas to make commercialization of these super-efficient AC units
a reality: 1) Update AC performance metrics and testing standards –
this is needed to counteract the tendency to over-cool in humid environments to
obtain desired comfort levels. The goal is to incorporate efficient
dehumidification performance into testing standards. 2) Partner with
the AC industry ecosystem – this is needed to get more manufacturers
to design and develop these systems. GCEA offers testing support. 3) Undertake
real-world demonstrations to gather performance data, generate evidence, and
build market confidence in super-efficient ACs. 4) Raise consumer
awareness – this will help people to purchase the super-efficient ACs
by teaching them that though they are higher in initial cost, they have a short
payback period and will save more over time with lower operating costs.
The industry once relied
mostly on fixed-speed AC compressors but has shifted to inverter ACs, which
feature a variable-speed compressor.
The testing was conducted between October 2023 and June 2024 and compared super-efficient models and standard non-inverter and inverter AC models, each with different efficiency ratings. Testing conditions also required measuring outdoor temperatures and relative humidities in 15-minute intervals, through India’s hottest and most humid months.
Refrigerants used in the
super-efficient units include R152a and R32.
“In the short-to-medium term in India, R32 is likely to
be the refrigerant of choice due to its proven performance, reliability, and
wide acceptability, making commercializing super-efficient ACs with this
refrigerant a viable option. We may also see the adoption of hydrocarbons like
R290, as its use has been demonstrated in the Indian market.”
How typical ACs
overcompensate for humidity by overcooling is shown below.
The lower power draw can also
help to guard against blackouts during peak demand periods if these units are
widely adopted, since they result in 50% average lower peak demand.
The climate impacts of using different
refrigerants with different GWPs are shown below. As noted above, R32 is likely
to be the refrigerant of choice in the near term. However, lower GWP
refrigerants such as R290, a propane refrigerant, a natural refrigerant that is
not patented and does not require manufacture by a chemical company like HFCs,
can be better choices for lower emissions, better performance, and lower cost.
I have long been a fan of R290 and wrote about it in my 2022 book Natural Gas
and Decarbonization.
Total cost of ownership must
rely on projections since these super-efficient ACs are not yet available, and
like any new technology, early costs will be higher. Once they are fully
commercialized, costs will drop. It appears they will (initially?) cost two to
three times more than typical ACs, but their lower operational costs will catch
up and overtake the typical ACs, resulting in significantly lower total cost of
ownership, including purchasing costs.
“Super-efficient ACs can provide significant cost
savings for consumers through reduced electricity bills and for the Indian
government through avoided investments in new grid infrastructure to meet the
growing demand for cooling. The government can support development and
production as well as incentivize adoption of super-efficient ACs by channeling
the savings from avoided grid investments to lower the first cost for consumers.”
The following are
recommendations going forward:
1 Policymakers
responsible for writing testing standards and designing labeling programs have
a key role to play in prioritizing revision of AC performance metrics and
testing standards that support production of super-efficient ACs. This
will help bring innovative technologies to bear and guide consumer choices.
2 Large
buyers can play a key role as anchor buyers to spur market demand for
super-efficient ACs. Relevant stakeholders within their
organizations — procurement teams, engineers, contractors, and consultants —
should prioritize products that reduce energy use, lower total cost of
ownership, cut life-cycle emissions, and enhance comfort, rather than focusing
solely on current performance metrics that are inadequate.
3 AC manufacturers are encouraged to
commit to developing and commercializing cost-effective super-efficient AC
products. This should be done in parallel with supportive
policies and market signals that enable manufacturers to continue their product
development.
4 Governments can explore innovative
strategies, including tax concessions, to boost the supply ecosystem, and
support financial mechanisms, such as rebates and low-interest loans, to
accelerate the market shift toward super-efficient ACs
References:
Bringing
Super-Efficient Air Conditioners to the Market: Insights from field testing in
India and the path forward. Developed by the Global Cooling Efficiency
Accelerator. RMI. April 2025. bringing_superefficient_acs_to_the_market.pdf
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