ASHRAE OR-16-C035

Abstract

<em>Institutional campuses often times encompass both centralized and decentralized heating and cooling systems. Each configuration inherently has advantages and challenges when trying to maintain occupant comfort while minimizing energy consumption. Recent technological advancement in computing power allows building energy modelers to quickly and efficiently develop models which can be evaluated as part of a centralized plant or as a stand-alone system. International attention to greenhouse gas (GHG) emission reduction has influenced policy in many nations around the world. According to the White House Press Secretary, the United States is targeting net GHG emissions 26-28% below 2005 levels by 2025. The attention to GHG emission reduction has brought the benefits of energy modeling to the forefront of building designers, managers and policy makers. Montana State University, located in Bozeman, Montana, has a dry, heating dominated climate. Currently the university operates a centralized steam plant serving 59 buildings totaling just over 3-million square feet. This centralized heating system distributes steam across campus using a network of utility tunnels. The cooling systems, however, are decentralized and primarily use cooling towers to reject heat. This paper details an alternative configuration the university evaluated and subsequently implemented to reduce GHG emission on campus. The university interconnected a small group of buildings to form an energy &#8220;mini-district&#8221; within the large centralized campus district. This mini-district contains eight buildings totaling just over 400,000 ft² (37,000 m²) or 14% of the total campus building square footage. These buildings contain research laboratories with substantial internal demand loads and traditional classrooms having natural, diurnal loads. Before implementing the mini-district it was common to see some buildings rejecting heat through cooling towers while adjacent buildings were experiencing heating demands. The energy mini-district uses a centralized heat pump plant with water loops allowing energy to be shared between the buildings. This configuration also allows for future incorporation of low carbon energy sources such as solar thermal arrays and ground-source bore fields. Building energy models were created and tuned using both historical utility data and energy measurements within the mini-district. Evaluation of the energy mini-district shows a GHG emission reduction of 14.26% over the original configuration using the steam heating plant with cooling towers.</em>