U.S. energy requirements will nearly double by 1985. In the intervening years, we are and shall continue to rely upon coal, oil, gas and nuclear power for 95% of our needs. At the current pace, we are not developing these resources fast enough to accommodate our exploding demand for energy. Clearly, we must make a strong and concerted effort to conserve what we are able to produce, at least until nuclear energy (especially the fast breeder reactor) can take its share of the load.

Energy conservation is truly a challenge worthy of our attention. Moreover, energy usage is a field ripe for improvement. Energy has always been so cheap in this country that plant engineers and designers have not generally concerned themselves with using it wisely. Management did not care, or perhaps even know, about the many ways it was being wasted. The rapid increase of energy costs over the last few years, however, has required new thinking on the part of engineers and architects. Owners are now more than ever aware of energy consumption, energy efficiency ration (EER), peak load demand rates, and life cycle costs. This increase in cost has also necessitated that HVAC design engineers consider annual operating costs in addition to initial equipment costs.

The introduction of the rotary helical screw compressor to the HVAC market some ten years ago is now proving to be timely with its many energy saving features. The most important feature is the wide variety of systems to which it can be applied. Couple this flexibility with the unique method of capacity control, and the energy savings are greatly increased over the conventional centrifugal package chiller/cooling tower system.

This paper will describe some of the most common screw compressor applications ,currently in operation, along with recommended selection and design procedures. In addition, an annual power consumption calculation method is included to help compare the various systems. This information will enable the design engineer to better determine the total economi,cs of any one particular system.