On Target: A Complicated and Successful Energy Retrofit Program

Abstract

The Lone Star Gas Corporate headquarters, in Dallas, Texas, consists of a five building, 355,000 square foot office complex with buildings ranging in age from 14 - 60 years old between 20,000 - 100,000 square feet (SF), and with multiple HVAC systems served by two central plants. The company was facing the inevitable increase in electric utility costs knowing that two reactors at a new construction nuclear power plant would be coming on line over during the next five years. By taking a proactive stance, a six month detailed energy audit commenced after a thorough internal energy analysis was conducted. The result of the audit was a multi-year $1.7 million retrofit project encompassing nearly 20 major items would be implemented over three years. Total energy and cost avoidance savings were calculated to yield a simple pay back of 1.5 years and a cash pay out of 3.5 years. Total energy reductions of 32% were achieved and the predicted economics realized. The various projects involved the application of nearly 18,000 square feet of window tinting, a total facility relamping and efficiency improvement project, installation of more efficient filtration systems, installation of control valves on the chillwater system, installation of a building automation system, installation of a plate heat exchanger for hydronic free-cooling, isolation of after-hours and 24-hour cooling loads on a separate loop, isolation and conversion of 24-hour steam requirements to reduce excess boiler capacity and run time, improvement of return air systems, the replacement and increase of cooling tower capacity, implement a preventive maintenance program, and improved operating procedures that focused on demand side management without thermal storage. The combined results of these single projects enabled the facility to remove and not replace 25% of the physical plant cooling equipment (one single-effect steam absorber) upon reaching the end of its expected life. Project costs and avoided savings were tracked monthly throughout the three year period. Additional energy and cost avoidance tracking for two more years was completed. In five years, a positive cash flow of more than $550,00 is only 9% less than the original projection. Improved employee comfort and enhanced space conditions have returned significant benefits to the work force of nearly one thousand people occupying this facility.