Market opportunities for applied natural gas engine driven hybrid chiller plants

The economics of gas cooling were examined for the case of a nine story, 160,000 square foot office building and a 348 bed, 272,000 square foot hospital in 45 cities. These two applications represent a range of the energy intensities andoperating hours experienced by commercial buildings, with office buildings typically having fewer operating hours and lower energy intensities than a hospital. Specific cooling plant configurations evluated included: three all electric chillers, three all gas chillers, one base or lead gas chiller along with two electric chillers, and one gas chiller for peak shaving along with two electric chillers. Whole building simulations of each building and plant configuration using the DOE-2 building energy analysis code produced estimates of annual energy usage for each operating scenario in 45 cities. Comparison of results to the baseline electric chiller plant requirements and then application of marginal summer electric demand and consumption rates and gas energy rates gave estimates of savings. The total electric savings due to substituting gas chillers for electric chillers was then adjusted to account for the additional gas energy costs to arrive at the net operating cost savings for each case analyzed. Payback of the initial cost premium of engine chillers in five years or less due to operating savings resulted in 21 of the 45 cities.