Sustainable & Attainable: Prepared For Takeoff
Examples include gray-water plumbing systems, proactive ventilation strategies, water and airside energy recovery, and the use of occupancy sensing to maximize setback opportunities. But for many of us, when we think of hotel HVAC, we think of crude and inefficient packaged terminal air conditioners (PTAC) rattling under a windowsill with the requisite missing control knob.
However, a viable energy efficient alternative to PTACs may be seen in the Department of Energy's report, Energy Consumption Characteristics of Commercial Building HVAC Systems Volume III: Energy Savings Potential, which can be found at the DOE's Energy Efficiency and Renewable Energy website at www.eere.energy.gov/buildings/documents/pdfs/hvacvolume3finalreport.pdf. The technology is variable refrigerant volume, or VRV(tm), and it has been identified as one of the 15 most promising energy saving technologies worthy of further research and development.
The Wave of the FutureVRV systems (referred to as variable refrigerant flow or VRF systems by many manufacturers) were introduced in Japan in 1982 and have since been deployed throughout the world. These systems are basically very large-capacity versions of the ductless multisplit systems that have achieved a niche market in the United States. They use multiple compressors and deliver excellent part-load performance and zoned temperature control, resulting in excellent occupant comfort.
Both installed costs and energy operating costs are highly application-dependent, but initial estimates of energy savings relative to conventional systems are in the range of 5% to 15%, with higher savings (as much as 30%) in mild or hot humid climates.
Estimates of the installed cost premium of a VRV range from about 5% to 20% over conventional systems, but in a case study of a 43,000-sq-ft German hotel, the costs of a VRV and an air cooled screw chiller were nearly identical. Specifically, the costs for the indoor and outdoor units of the VRV were higher than for the chiller, but savings on insulation, valves, and installation made up the difference.
Several barriers exist to the adoption of VRV/VRF systems in the U.S. when compared to integrated heating/cooling options such as a rooftop system with gas heat, or a chiller/boiler system. These include first cost, maintenance, the lack of an integrated gas heating option, long refrigerant piping runs, and the lack of brand-name recognition. However, when the approach is compared to conventional PTACs applied in moderate and southern climes, the barriers can be narrowed to first cost (which may be offset by total life cycle costs) and refrigerant piping concerns.
Regarding long DX piping runs, many contractors contend that refrigerant leaks are hard to find and cumbersome to repair. There is a perception of increased liability exposure due to the large volume of refrigerant present in the system and long runs through occupied spaces. All of these issues have been sufficiently addressed in Europe, Asia, and Latin America, but a major education campaign is necessary to change the perceptions of contractors and engineers.
When it comes to brand name and reputation, you are looking at the same players who have defined the ductless PTAC market. And now that at least two of the leading Japanese manufacturers have entered into strategic alliances with leading U.S. manufacturers, contractors and owners may be more comfortable with their options.
VRV/VRF systems have substantial energy-related and nonenergy advantages over other systems in many cases. The barriers to adoption in the U.S. initially existed in other regions of the world, but they have been overcome though demonstration of the technology's benefits. To demonstrate the claimed advantages and to understand and overcome the barriers to commercialization in the U.S, someone has to step out of their comfort zone. Like the space program, progress cannot be made without risk, but the upside could be significant.
As former ASHRAE president Bill Coad said about HVAC innovation, "... if we accept the challenge it could be the beginning of a technological renaissance. It requires all of us to carry part of the burden of responsibility for moving our technology to the next level. We will have to accept the mindset of change with both its benefits and its risks. But it will assuredly give us new pride in ourselves, our colleagues and our mission."
Ground Control to Major Tom... Are you ready to explore the final frontier of HVAC? ES