Since its emergence in the late 1980s, scroll technology has brought performance advantages to systems that have adopted scroll compressors. Those advantages have been evidenced by the acceptance of scrolls in commercial and residential air conditioning applications. In fact, scroll compressors now power the vast majority of the higher efficiency 12-SEER and 13-plus-SEER systems sold in the United States.

This shift in compressor technology was driven by the energy efficiency ratio (EER) gains provided by scrolls. Current scroll compressors achieve overall machine efficiencies greater than 72 percent.

Today, scrolls can achieve the overall compressor efficiency levels needed to help system designers meet the specifications demanded by market and regulatory requirements. Another important benefit of scroll technology is its ability to regulate its compression ratio so that it matches the desired performance profile of the system.

It is also important to note that as scroll technology has become more efficient, it has not grown in size or weight. Scroll compression technology's compact design makes it easier for manufacturers to apply scrolls in both existing platforms and new system designs.

In the years ahead, manufacturers will continue to explore new scroll compressor designs and seek out new ways to leverage energy efficiency across derivative versions of those designs. In fact, several of those designs are already available today.

New Refrigerants

Another major factor driving scroll evolution is the growing application of HFC refrigerants, such as R-410A. New R-410A scrolls are poised to replace older R-22 compressors as we move toward 2010, when chlorinated refrigerants will be banned from use in new equipment.

Much analysis and testing to date confirms that R-410A is the best long-term solution for residential and smaller commercial air conditioning designs. Since R-410A evaporates with a one-third higher heat transfer coefficient and one-fourth lower pressure drop compared to alternatives, it should play an increasingly important role in future system efficiency improvements.

Modulated Platforms

The design and introduction of new modulated platforms of scroll technology will also help drive future efficiency increases in commercial and residential air conditioning equipment. While modulation requirements vary depending on the application, modulated scrolls are well suited to the design because they are available in a simple package. Without the need for inverters or associated controls often used for modulation, the electronic controls required with scroll are simpler than those required with other compressor technologies.

In the U.S. residential market, a modulated two-stage scroll compressor is available for home air conditioners. The technology enables home air conditioning systems to operate more efficiently than single-compressor systems and improves humidity control. With a part load capacity stage, systems with modulated scroll can maintain precise temperature levels and lower relative humidity while saving homeowners up to 60 percent on energy costs when compared with 10-SEER systems.

In commercial air conditioning applications, digital modulation represents the latest innovation in scroll technology. Its simple design provides very precise temperature and humidity control, making it a good choice for commercial and light commercial applications, air dryers, refrigerated transport, and other applications. This broad range of application flexibility is possible because digital scroll capacity can range from 10 percent to 100 percent of full load.

Digital scroll technology builds on the fundamental scroll design platform by offering a new way to actively manage axial compliance - or the vertical separation of the scroll components. For example, Copeland's Digital Scrollâ„¢ employs two concentric scrolls, one inserted within the other. One scroll remains stationary, as the other orbits around it.

By utilizing time-dependent unloading of the scrolls axially, this technology achieves the desired capacity modulation by averaging the two states of loaded versus unloaded operation over time. This allows the capacity of the compressor to fluctuate and precisely match the desired temperature and power consumption for the system, providing the right amount of cooling needed for optimal comfort.

While this technology has broad interest in the U.S. commercial market, it is bringing improvements in comfort, energy efficiency, and environmental impact to people living in Asia. Digital scroll technology is also replacing traditional, inverter-driven installations in these developing markets.

Scroll's capability to match capacity and power consumption - and maintain precise temperature and humidity control - is providing a higher level of comfort, greater energy efficiency, and quieter operation for these systems, even as it lowers energy costs. The reduced power consumption of these units is helping reduce demand for new power generation facilities in the region.

Beyond Comfort Cooling

In Western Canada, scroll compression technology is helping oil and gas industry producers reduce greenhouse gas emissions and operating costs, while increasing production rates. The industry's first modular scroll compression package is giving producers a new level of flexibility and reliability.

This approach is critical to achieving low maintenance and enhanced oil production. Field data has shown that oil production rates have increased on many wells employing this new application of scroll technology.

Cooling equipment manufacturers in the refrigerated transport industry are using digital scroll technology to bring reliable temperature control to refrigerated transport containers. The technology offers a new way to modulate, or automatically adjust, the capacity of the compressor from 10 percent to 100 percent, so it can precisely match the refrigeration load.

Initial data shows that this approach is increasing energy efficiency by as much as 30 percent in transport applications, and is capable of holding a temperature to ±0.5 degrees F.

Monnier is vice president of engineering for Copeland's Air Conditioning Division. He has more than 20 years of experience in the HVACR industry and holds several compressor-related patents. Copeland is part of Emerson Climate Technologies. For more information, visit www.emersonclimatecontractor.com.

Publication date: 04/05/2004