Reaching the Outer Limits of Efficiency
High-end HVAC cooling equipment pushes the SEER envelope
Energy efficiency ratings (SEER/EER) of air conditioners and heat pumps keep rising, thanks to new technologies such as electronically commutated motors (ECMs), inverter-driven compressors, and advanced heat exchangers. These technologies have helped boost high-end cooling equipment ratings to the mid-20-SEER range, which was unthinkable just a few years ago.
So how much higher can SEER/EER ratings go? Using today’s technology, manufacturers think there is still some room to grow in all types of cooling equipment. And as technologies continue to evolve, it is likely there will be even greater efficiency gains made in cooling systems.
The heart of any cooling system, whether it be an air conditioner, heat pump, rooftop unit, or geothermal system, is its compressor. While not solely responsible for a system’s efficiency ratings — as motors, heat exchangers, refrigerants, etc., also contribute significantly — it does play a very big part. For example, high-efficiency compressors, such as Emerson’s second-generation Copeland Scroll™ variable-speed compressor, can help system manufacturers achieve SEER ratings of more than 25.
“Emerson’s compressor efficiency has continued to increase over the past 30 years since the launch of the Copeland Scroll,” said Joe Linsenmeyer, marketing director of air conditioning, Emerson Commercial and Residential Solutions. “Using our compressors, several OEMs have introduced systems reaching 20-plus SEER over the last several years.”
A combination of technologies, including an AC inverter-driven variable-capacity compressor, high-efficiency ECM, optimized heat exchanger, and electronic expansion valve, helps York’s new Affinity™ YXV variable-capacity air conditioner reach an energy-efficiency rating up to 20 SEER.
“The whole system with our new advanced proprietary control including optimized algorithms makes a move forward to that next step or level in system efficiency,” said Ken Ely, product manager, Johnson Controls Inc.
There is still plenty of runway, though, as Ely predicts that cooling systems using current technologies may reach into the high 20-SEER range.
“It will not be one technology but a combination of technologies used in conjunction with an understanding of the changing test requirements and the impact on system ratings. I speak in systems, because at these levels, it is no longer an outdoor unit matched with various indoor unit suppliers and third-party thermostats. It is an engineered communicating system where all systems must communicate and speak the same language to reach these aggressive efficiency numbers.”
As an engineered system, reaching the next level of energy efficiency will not be the result of a magic bullet, said Ely.
“Instead, it will be small, incremental changes in multiple components and, more importantly, integrated system technologies that will take this industry to the next level. For system performance beyond that next level, new technology in heat transfer, motors, compressors, refrigerants, and controls will most likely be needed.”
Trane is focused on breaking through to that next level of efficiency, which is why the company is investing in research that is focused on developing new compressors, inverters, heat exchangers, motors, and airflow devices that will enable next-generation efficiency levels using the typical vapor compression system.
“We continue to be very active in helping identify and evaluate next-generation refrigerants that not only improve system efficiency but also reduce the environmental impact,” said Matt Barga, director of product management, Trane. “We are also investing in research and development for breakthrough technologies that might someday change the theoretical limit of efficiency that we are able to create today.”
While those breakthrough technologies may be a few years away, Trane still offers a number of highly efficient cooling products today, including TruComfort™ variable-speed air conditioning systems.
“TruComfort systems offer efficiencies of 22 SEER and provide precise comfort by running at the exact speed needed to keep a home comfortable,” said Barga. “This allows the variable-speed compressor, outdoor fan, and indoor fan to vary operating speed and Btu as the temperature outside changes, slowing down or speeding up gradually in as little as 1/10 of 1 percent increments to keep comfort within 0.5°F of the thermostat setting.”
Ductless systems are also making great strides in terms of energy efficiency, with many products now boasting mid-20-SEER ratings. One example is Midea’s Premier Hyper Series High Wall system, which has a SEER rating of 24.7 (14 EER).
“This series optimizes energy usage, while at the same time providing 100 percent heating capacities at an outdoor ambient temperature as low as 5°,” said Bruce Hazen, HVAC sales director, Midea. “As a result of its heightened, all-season performance and widened applications, users can experience lower electric and utility bills while still maintaining exceptional comfort.”
An even higher efficiency ductless system will launch later this year, when Midea releases the Quattro, a Premier Series product that will improve upon energy efficiency by another 8-10 percent.
“The Premier Quattro will have step-less inverter technology, which can gear down the inverter speed on demand,” said Hazen. “In addition, built-in Wi-Fi capabilities will provide the ultimate in comfort and convenience while also maximizing efficiency, as consumers have control of their environment at their fingertips while home or away.”
Geothermal heat pumps are already highly efficient, with EER ratings well into the 40s, but improvements can still be made.
“We don’t believe efficiency improvements have reached a limit yet,” said Naveen Halbhavi, director of marketing, ClimateMaster Inc. “Right now, a geothermal heat pump operating on an open well loop with existing technology can achieve 53 EER/5.9 COP with favorable water temperatures.”
ClimateMaster’s most efficient geothermal heat pump is currently the Trilogy QE Series, which operates at 24 EER/3.6 COP at full load and a 45 EER/5.1 COP during part-load conditions. The equipment utilizes technologies, such as microchannel heat exchangers and variable-speed blowers, pumps, and compressors, in order to reach its high-efficiency ratings. In addition, the system recovers energy and uses it to provide hot water, which reduces the user’s overall power consumption even further.
For now, ClimateMaster believes the best opportunity for increasing efficiency lies in using high-efficiency motors and compressors.
“We think there is another 10-15 years before geothermal reaches the limits of efficiency improvements,” said Halbhavi. “Going forward, we are continuously exploring ways to enhance efficiency either by new refrigeration cycles or thermal engineering.”
Energy efficiency is currently limited by compressor technology, said Robert R. Brown, vice president of engineering, WaterFurnace Intl. Inc., which is why cooling equipment will probably only see incremental improvements until a different compression technology is developed. “Using variable-speed inverter drives can yield higher efficiencies. In addition, heat exchanger optimization, as well as some of the new refrigerants, might improve efficiency a little bit, but we are largely at the limits with variable speed.”
There are some other technologies that can improve performance at differing conditions, said Brown.
“For example, in water heating and other higher ‘lift’ applications, vapor injection provides benefits of higher capacity and efficiency but adds a third heat exchanger, second expansion device, and some added cost and complexity,” he said. “As it gets applied to variable speed, the technology will provide a slight efficiency and capacity boost, as well.”
As can be seen here, improving the energy efficiency of cooling equipment is a continuing concern for manufacturers, with most devoting a lot of time and resources to developing the next generation of energy-efficient equipment. When any of these innovative technologies will be ready for market is anyone’s guess, but until then, chances are good that cooling system efficiencies will still continue to increase.
Publication date: 6/26/2017