How to Save on Heating Costs Even in These Harsh Winter Temperature
Munster, IN
Community Hospital's heating plant consists of two steam and two high temperature hot water (HTHW) boilers. The steam boilers are utilized in winter to supply steam for humidification, sterilization, surgery and other miscellaneous systems requiring steam. The HTHW boilers, on the other hand, are used year round to supply high temperature hot water. In winter, they are used to heat the building and, in summer, HTHW boilers are used to meet the summer reheat loads and to generate steam through the steam generators.
MEG was called upon to evaluate the existing HTHW system and provide feasibility of adding either a pony boiler system or a heat exchanger system to the existing heating plant (to improve system efficiency and operating costs). The existing HTHW boilers, originally used to serve the absorption chillers (replaced with electric), are currently oversized and thus not operating efficiently in summer. This change not only resulted in extra HTHW boiler capacity but also caused additional losses (such as short cycling, pre and post purge, radiation and stack losses) during startups and shutdowns in summer. According to the boiler manufacturer, these losses may be as high as 18%. Hence, the boilers may be rated at 78% efficient; an oversized boiler may be operating at efficiencies as low as 60% due to these losses.
Based on system evaluation and calculations, Millies Engineering Group recommended adding a steam to hot water heat exchanger utilizing existing steam boilers to meet the summer loads. In this option, the existing HTHW boilers would be off and the existing steam boilers operated to meet not only the humidification load but also to satisfy the reheat load via the new heat exchangers. In winter, however, the steam and HTHW boilers would continue being used as they are currently. Calculations indicated that there will be approximately $26,500 saved every year by not operating oversized HTHW boilers. Based on the above cost, the simple payback for this option would be under 7 years.
The hospital is very pleased with our findings and recommendation and is planning on implementing this option before the next heating season.