Compressor Modulation Offers Efficiency, Reliability, and Comfort
March 29, 2010
HVACR compressor manufacturers strive to deliver high levels of reliability, comfort, and efficiency in a market that also demands low cost and compliance with environmental laws. But now, more than ever, they are faced with an even stronger charge to provide compressors that offer an optimum level of efficiency while maintaining reliability and comfort.
The latest legislation, regulations, and end user preferences have contributed to that charge, creating tough demands with regard to energy efficiency and comfort. Compressor manufacturers have been making sure these challenges are faced head on by continuously delivering cutting-edge improvements in compression technology.
MODULATING TECHNOLOGY: A BALANCING ACTToday’s conventional, fixed-capacity compressors have a lot to offer, but because full compressor capacity is not always needed, units with conventional compressors run intermittently, to reduce output under light load conditions. This can cause discomfort from temperature swings and poor humidity control, as well as decreases in efficiency and overall reliability. As a result, manufacturers have worked to develop technologies that specifically meet part-load challenges and provide higher efficiency, improved comfort, and better system performance.
Modulating compressor technologies adjust capacity either in steps or in a continuous fashion for applications with varying loads and/or changing ambient conditions. This technology also reduces compressor cycling, achieves higher part-load efficiency, and provides enhanced humidity control at lighter loads, where fixed-capacity systems tend to struggle. This new wave of modulating compressors provides a variety of solutions for unique air conditioning and refrigeration applications.
Residential air conditioning applications: The residential air conditioning market in particular continues to face an increasing need for enhanced energy efficiency and improved comfort. A laundry list of new tax incentives and utility rebates are making high-efficiency systems more affordable for homeowners. These incentives have increased the adoption of high-efficiency systems, including geothermal systems, which have grown steadily, even through the economic downturn.
By adopting technologies such as modulating compressors, manufacturers are responding with more product choices to meet these efficiency incentives now available to their customers.
Stepped modulation is one compressor technology that is widely used in systems with higher SEER ratings, including both traditional air-to-air and water-to-air (geothermal) applications. Stepped-capacity scroll compressors, like the Copeland Scroll UltraTech™ compressor from Emerson Climate Technologies, are ideal for high SEER performance, and provide a simple, easy-to-apply solution to enhance system efficiency for both air conditioners and heat pumps.
They offer precise temperature control, improved part- load efficiency, and reduced on-off cycling, providing a highly efficient and reliable option for homeowners. With two steps of capacity, 100 percent at full-load and 67 percent at part-load, these compressors offer improved comfort and humidity control for both cooling and heating seasons, providing year-round benefits.
Another form of stepped-modulation technology applied in some residential applications today is an approach that utilizes multiple compressors connected with a manifold, commonly referred to as tandems. Tandems provide a rather simple means to reach high SEER targets in residential applications.
Continuously variable modulating compressor technology is also being introduced more frequently in the residential air conditioning space. Variable-speed compressors offer some of the highest system SEER potential, ultimately lowering energy costs and providing optimal comfort to the homeowner. Utilizing enhancements such as brushless, permanent magnet motors in the compressor, in conjunction with onboard electronics and system controls, variable-speed compressors offer manufacturers unique flexibility to reach optimal efficiency and comfort.
Variable-speed compressors have been around for years in similar applications, and manufacturers like Emerson Climate Technologies are actively working to deliver optimized solutions for residential air conditioners, heat pumps, and geothermal systems that leverage this proven technology.
COMMERCIAL A/CModulating compressor technologies are also a good solution for the specific challenges facing the commercial air conditioning industry, including precisely managing varying temperature and humidity load requirements in the most efficient manner. As the main power consumer in rooftop systems, compressors account for about 55-83 percent of the system’s total energy use, making them a primary target for improvements in efficiency. All in all, the commercial air conditioning market needs solutions that are flexible, reliable, efficient, and precise.
The continuously variable modulation found in scroll compressors with pulse width modulation or digital technology, such as the Copeland Scroll Digital™ compressor, offers a unique and proven solution for the specific needs of commercial air conditioning applications. This technology offers increased part-load efficiency in Integrated Energy Efficiency Ratio (IEER) rated systems, and provides some of the best energy savings and reliability available in this particular application.
Because of their ability to match varying loads, scroll compressors with digital technology are beneficial for applications that see large daily temperature swings and cooling loads, such as schools, restaurants, and movie theaters. And, because of their ability to maintain precise temperature control, they also provide a good solution for applications in hospitals, museums, or telecomm facilities. These compressors have enhanced controls and protection for additional reliability, as well as tighter temperature and humidity control and lower applied and operating costs. Ultimately they offer improved load matching over stepped modulation and provide much greater energy savings than hot gas bypass options.
Although scroll compressors with digital technology offer a uniquely designed match for commercial air conditioning applications, stepped-modulation compressor technology is also a very viable option.
The most effective stepped-modulation technology for certain commercial air conditioning applications, such as larger commercial chiller systems, can be found in tandem compressor technology. With tandems, two or more compressors can operate alone or together, delivering several discreet capacity steps as needed. Similar to other modulation approaches, tandems offer improved part-load efficiency while maximizing full-load efficiency. Tandems remain an important modulating technology option for both current and future applications.
COMMERCIAL REFRIGERATIONSimilar to the air conditioning industry, the commercial refrigeration sector desires energy efficiency, precise temperature control, and reliable products. In particular, retail and transport end users have a strong need to reduce their energy footprint and avoid food spoilage. Supermarket executives in particular rank energy savings as their No. 1 concern, above health care costs and competition.
With the cost of operating refrigeration equipment at 65 percent of total store electricity usage, it’s no secret that reducing energy costs while preserving perishable product integrity is a priority. To meet these needs, scroll compressors with digital technology have been adopted at a fast rate into supermarkets and seagoing refrigerated container applications. This approach greatly improves system efficiency relative to earlier refrigeration methods, such as hot gas bypassing or suction gas throttling.
In addition to scroll compressors with digital technology, supermarket end users are also finding high value by using digital technology with Discus® compressors. Similar to scroll compressors with digital technology, Discus compressors with digital technology allow the system to specifically match the capacity being generated to the required load, providing the opportunity for the system to operate more efficiently, resulting in optimum system performance and control.
The capacity modulation also reduces suction pressure and temperature variation of the refrigerated space and provides a dramatic decrease in compressor cycling rates, therefore improving compressor reliability. This compressor technology ultimately helps decrease product loss, reduce the store’s energy consumption, and extend equipment life.
THE FUTURE OF COMPRESSOR MODULATIONRegulations, standards, and demand: Although many modulation compressor solutions are already available, standards for air conditioning and refrigeration applications continue to evolve, making new technology enhancements and developments even more important. With new legislation increasing efficiency minimums up to 15 SEER in some regions, along with higher HSPF levels for heat pumps, the residential air conditioning industry should see a strong push for broader adoption of modulating compressor technologies in the coming years.
Energy regulations will also impact the commercial air conditioning and refrigeration segments, with new Energy Star levels including part-load requirements and the ever-increasing push by the Green Building Council for LEED level certifications and carbon footprint reductions.
Advancements in technology: Modulating compressors are an adaptable technology with room for growth and enhancement well into the future. One area that is currently expanding is the realm of electronics for controlling and monitoring these compressors. As the industry progresses with advancements in smart grid capability, active controls, combined with modulating compressors, provide the peak load-shedding potential that utility companies desire. As these developments in energy technology become a reality, and the demand for more-efficient systems and higher levels of comfort persist, compressor electronics will likely be required for optimal efficiency, communication, diagnostics, and reliable system performance.
The trend toward HVACR modulation is likely to continue due to the many modulation technology options available today, and the continued growth and evolution of systems that adopt these modulation methods. With this increased flexibility in choosing the particular modulation type that best meets system needs, the industry as a whole can truly benefit from the enhanced comfort, energy efficiency, reliability, and overall system value that modulating compressor technology affords.
Sidebar: Commercial ApplicationsCopeland Scroll Digital™ compressor technology has been successfully applied in a diverse range of commercial air conditioning and refrigeration applications worldwide. The compressor provides continuously variable-capacity modulation and is ideally suited for commercial applications with widely varying loads or a need to maintain precise temperature and humidity control.
It offers an innovative way to modulate the capacity of the compressor 10-100 percent so that the output precisely matches the changing cooling requirements of the space, and it does this without changing the speed of the motor. This approach to capacity modulation is as much as 30 percent more efficient than traditional hot-gas bypass and is capable of precisely holding temperatures to within 0.5°F.
This digital modulation technology is also being applied in Copeland Discus Digital™ compressors, which offer 10-100 percent continuous digital capacity modulation for enhanced reliability and efficiency, longer food shelf life, and less food shrinkage. These compressors are ideal for temperature-sensitive applications like supermarkets and food transport.
Sidebar: Residential ApplicationsCopeland Scroll UltraTech compressors currently have more than 1 million installations worldwide with superior levels of comfort and energy efficiency, saving up to 60 percent on energy costs as compared to conventional HVAC systems. With as much as a 200-W reduction in power consumption, systems equipped with UltraTech can better meet market needs for higher SEER and full-load EER ratings.
Its modulating two-step capacity design provides superior comfort by reducing humidity and allowing precise temperature control. These compressors deliver higher efficiency across the complete line than any other compressor technology, and now with the next generation of the line, this technology offers even greater improvements in reliability and increased part- and full-load performance.
Publication date: 03/29/2010