Heat pumps favorably impact energy consumption and. Sustainable HVAC Technology. N e w T r e n d s i n

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1 N e w T r e n d s i n Sustainable HVAC Technology New technologies based on the use of CO2 as a natural refrigerant have been making progress toward addressing many aspects of energy savings and environmental protection, particularly outside the United States until now. Although widely used throughout Europe and Asia, CO 2-compressor technology has yet to take off in North America; but as focus continues on environmental repair, widespread use of this type of technology is on the horizon. B y M e r l e G. R o c k e All images courtesy of EcoThermics Corp. Heat pumps favorably impact energy consumption and environmental protection two pressing issues experienced around the world because they deliver much more heat for energy consumed than furnaces and heaters burning fossil fuel or using electricity. Heat pumps though have been restricted in application due to the limitations of available components and fluids designed for refrigeration. However, technology is evolving to enable a high-pressure transcritical cycle using non-regulated CO 2 that extends the temperature range in which heat pumps perform effectively. The equipment carries a premium price, but in water-heating applications, an investment in a CO 2 heat pump can deliver payback in 2 6 years because of the low energy consumption. High energy consumption strains our energy supply and produces ever increasing volumes of green house gases. One clear approach to reducing consumption is to use energy more efficiently and to use energy that would otherwise be wasted. Heat pumps do just that. 26 RSES Journal OCTOBER 2010 Rather than using fuel or electricity to generate heat from a furnace or heater, a heat pump lowers the temperature of a source by pulling heat from it, and raises the temperature at the destination by delivering heat to it using the thermodynamic properties of the intermediate fluid refrigerant. Conventional heat pumps use the hot stream to increase temperatures at the delivery point and reject the cold to cool outside air. Likewise, conventional air-conditioners and refrigeration units use the cold stream to lower temperatures at the heat source and waste the hot to heat outside air. Heat pumps deliver several units of heat for each unit of energy consumed in the compressor during the compression part of the thermodynamic cycle, typically delivering a COP above 3, and sometimes more than 4. Since furnaces cannot provide more heat output than the energy contained in the fossil fuel or electricity consumed, they never have a COP greater than 1.

2 Heat-pump technology continues to evolve to enable a high-pressure transcritical cycle using non-regulated carbon dioxide that extends the temperature range in which heat pumps perform more effectively. However, conventional heat-pump market penetration is significantly limited for two reasons: lack of performance at extreme temperatures, such as cold climates or high-temperature water-heating; and the cost and risk associated with handling regulated HFC refrigerants long-duration greenhouse gases. Market trends According to a June 2009 report from Priority Group and a 2006 report from U.S. Industrial Reports, the global heatpump market is a $20-billion industry, and it has some of the fastest growing segments (17.5%) in the $65-billion global HVACR industry. Following are a few cases expanding upon this. Heat pumps as a substitute for conventional HVACR products Introduced in commercial markets during the 1960s for a variety of heating and cooling applications, the heat pump soon expanded into residential markets as a substitute for less-efficient electric and fossil-fueled furnaces and air-conditioners. While this market expansion continues around the world, heat pumps have recently entered a new market segment domestic and commercial waterheating. General Electric introduced an HFC heat pump in 2009, the GeoSpring hybrid water-heater, promising a reduction in annual energy costs of 62% compared to a conventional natural-gas water-heater. Rheem introduced a similar product, the HP-50, promising a 50% reduction compared to a conventional electric water-heater. And the 2001 introduction of the Eco-Cute a play on the Japanese word for supply hot water, which is kyuto water-heater using CO 2 as a refrigerant has gained significant market share in Japan and Europe by demonstrating even greater energy-cost reductions of 80% and 36% compared to electric and HFC water heaters, respectively (Source: en-ex srl Italy, producing hot water at 65 C, 2009). Natural refrigerants as a replacement for synthetic refrigerants While synthetic refrigerants have dominated the market since their invention in the 1920s, natural refrigerants including CO 2, propane, butane and ammonia are growing in market share. Driven by regulation and economics, this trend has been established most notably in refrigerators and coolers that use the Greenfreeze refrigerant, which is a mixture of purified butane and propane co-developed by Greenpeace in With 100 million units produced annually by all the major European, Chinese, Japanese and Indian manufacturers these products have a 40% share of the world market, and a 90% marketshare in Japan and Europe according to a Greenpeace report, titled HFCs, A Growing Threat to the Climate (2009 Updated Edition). This technology was first introduced to North America in 2009 with Bosch and General Electric refrigerators. Naturally occurring carbon dioxide has great promise to meet long-term market and regulatory demands for safe, environmentally friendly and sustainable refrigerant in a large range of heat-pump applications. The thermodynamic properties of CO 2 make it an effective refrigerant in transcritical cycles crossing through the critical temperature and pressure below which the refrigerant is in a liquid and vapor mixture extending the effective application range beyond subcritical cycles for which HFC refrigerants are optimized. This translates into a compact package that can efficiently provide hightemperature heating and even pull heat from subzero sources. Heat-pump systems using CO 2 technology can benefit endusers with very low operating costs; and service technicians benefit because carbon dioxide is not toxic, flammable or regulated, making component replacement in the field less complex and costly. OCTOBER 2010 RSES Journal 27

3 Testing and field trials continue on CO 2 components, such as this one being performed on a semi-hermetic CO 2 compressor. Opportunities, problems, solutions Natural-refrigerant products are creating market awareness and demand by demonstrating the efficiency advantages of CO 2. According to Priority Metrics Group and U.S. Industrial Reports, the global markets for heat pumps and compressors are $20 and $2 billion, respectively, and several companies are developing CO 2 compressors to embrace this new opportunity. Development has advanced furthest for <2-ton systems, such as hot water-heaters, vending machines, mobile transport and >7-ton large, cascade systems for food refrigeration (per discussions with the U.S. Army Power Division, Environmental Systems Branch, OEMs, and U.S./European HVACR manufacturers). CO 2 compressors less than 7 tons successfully introduced in the market to date include a 2-ton, two-stage rotary compressor made by Sanyo used in a water-heater with the generic name of Eco-Cute, and a smaller scroll unit used in vending machines. Other CO 2 compressors in the 3 7-ton-size segment now include recently introduced models from Dorin (Italy) and Bock (Germany) targeted for commercial and industrial applications. Commercial-size, CO 2 heat-pump waterheaters were introduced in This being said, CO 2 presents a set of difficult technological challenges beyond conventional HFC heat-pump experience. A fundamental problem in transcritical compressor 28 RSES Journal OCTOBER 2010 development is attempting to adapt low-pressure (~400 psi) technology such as HFC-compressor designs to high-pressure (~1,600 psi) applications. There has been initial success in small applications. Due to the stringent engineering and manufacturing requirements with high pressures, the challenge to adapt low-pressure technologies is even more difficult with larger-size compressors. An axial piston compressor (developed by EcoThermics Corp. located in Peoria, IL) departs from conventional rotary, scroll, screw and reciprocating compressors adapted for use with CO 2. The compressor was designed to tolerate the high-pressure and particular requirements of CO 2. It is driven through an external input shaft, which allows system packagers the flexibility to have their choice of drive motors. The Axial Transcritical 54cc (AT54) model has demonstrated durability and high efficiency in tests performed at both the company s research facility and by Herrick Labs at Purdue University. Pilot production will begin in the second quarter of 2011 for the purpose of OEM system development and lab/field demonstration. EcoThermics also is developing additional CO 2 compressor technology that extends efficient heat-pump application to cold climates and high-temperature applications. A kw (3 7 ton) CO 2 compressor, an enabling component for a wide range of CO 2 heat-pump products also is

4 being developed. The compressor is differentiated from other CO 2 compressors in several respects. The multi-piston axial compressor design departs from conventional rotary, scroll, screw, reciprocating (piston/ crankshaft) compressors originally designed for synthetic refrigerants manufacturers. Also unique is an energy-recovery module designed to reclaim compression energy for an improvement in efficiency of up to 35%. Other benefits include high power density (manufacturability, durability) and application flexibility (portability, optional diverse modular power inputs such as ac/dc electric, and hydraulic power for offthe-grid operation, and variable-output capacity to maintain peak efficiency for continuously changing system demands). A flexible modular design allows for custom builds to meet a broad range of OEM specifications. Competitive advantages for OEM manufactured CO 2 heat-pump products include the following end-user benefits: g Reduced energy consumption; g Lower total cost of ownership; g Precise zone temperature; g Wider range of ambient conditional; g Higher heating temperatures; g Greater durability; g Environmental sustainability; g Smaller size and less weight; and g Easy to install and service. An advanced, sixth generation compressor prototype (the AT54, a single-stage 18-kW (4 5-tons) configuration is available today in limited quantities for pilot testing by prospective OEM customers. The AT54 has demonstrated durability, high efficiency (>60% overall isentropic efficiency) and high power density. Pilot production Circle Reader Service No. 57 OCTOBER 2010 RSES Journal 29

5 Heat-pump systems using this new technology will not only benefit end users who will realize significantly reduced equipment owning and operating costs but HVACR service technicians as well. in the low hundreds will begin in Q for the purpose of OEM evaluation and lab/field testing. These units have a targeted cost of $1,900. Looking to the future The initial target customers for these compressors are OEM heat-pump system providers for water heaters in applications such as dishwashing, laundry, kitchens and numerous industrial processes. The common requirement is hot water in excess of 80 C (180 F); and as was stated above, HFC heat pumps do not perform at these temperatures. Hot water at this temperature has conventionally been heated by electric, natural gas or propane equipment. CO 2 heat pumps consume as little as one-fourth the energy and present short payback periods since the initial installed cost is at a premium. With ease of installation in new and retrofit scenarios, energy-efficient CO 2 heat-pump water-heaters will compete well. An important byproduct is water-chilling and space-cooling for little additional cost. During the next several years, EcoThermics (among other CO 2 compressor manufacturers) will be working closely with OEM heat-pump system providers that share compatible goals for CO 2 heat pumps. The company will be identifying specific opportunities that leverage the AT54 compressor, adjusting requirements for additional customer s needs and completing UL certification of the production design. Full-scale production is targeted in Future development will focus on regenerating energy that is typically wasted in the heat-pump expansion cycle to improve system efficiency by as much as 30%; and supporting OEM-system providers to develop systems that recuperate heat-pump waste streams typically rejected to outside air. Heat-pump systems using this new technology will not only benefit end users who will realize significantly reduced 30 RSES Journal OCTOBER 2010 Lab test results (available at on CO 2 compressors will be an imperative resource to convince the marketplace that carbon-dioxide-based technology is worth the money, effort and time. equipment owning and operating costs but HVACR service technicians as well. In the meantime, the world is watching and waiting to share in these advantages as natural-refrigerant technologies spread across the globe. [Editor s Note: Check out this feature online for a direct link to a performance study, titled Experimental Performance of a Prototype Carbon Dioxide Compressor, that was done at Purdue University s Ray W. Herrick Laboratories, School of Mechanical Engineering.] Merle G. Rocke is the Chairman and CEO of EcoThermics Corp. He has an international background in manufacturing, technology, marketing, supply-chain integration and business consulting. For more information, Rocke at mrocke@eco thermics.com or visit