Campus energy plants produce chilled water, heating water, steam and/or electricity to serve a group of buildings in a common location. These energy plants are a vital key in today’s quest to design buildings with higher energy efficiency, reduced carbon footprints, water saving features, and lower environmental impact.
Chillers and boilers are the largest users of energy users by buildings. Any discussion on energy efficiency improvement must start with these pieces of equipment. Options to consider in the selection of chillers include the use of water-cooled condensers; emphasis on part load efficiency; the use thermal storage concepts; and optimization strategies for multiple chiller applications. Options to consider in the selection of boilers include the use of flue gas economizers; blowdown energy recovery systems; and matching boiler types to the load characteristics of the campus.
Major reductions in carbon footprint can be realized by the use of renewable energies such as solar, biomass and biodiesel. The most prevalent of these used for campus energy plants are steam systems using biomass fuels. In a typical application, biomass is conveyed to gasifiers where it is heated and pyrolyzed. The resulting syngas is then collected and burned in a furnace to produce steam. It is important to note that the burning of biomass does release the same amount of carbon dioxide as the burning of fossil fuels. However, fossil fuels release carbon dioxide captured by photosynthesis millions of years ago – an essentially “new” greenhouse gas. Biomass, on the other hand, releases carbon dioxide that is largely balanced by the carbon dioxide captured in its own, more recent growth.
Sustainability standards for buildings focus on the water used by people at toilets, urinals, and lavatories. However, cooling towers actually use more water than all the plumbing fixtures combined in a typical building. Water saving features for campus energy plants include the reuse of rainwater or coil condensate for cooling tower makeup; the use of boiler blowdown recovery tanks to limit cooling water; and the use of energy recovery chillers.
The consolidation of cooling and heating equipment at campus energy plants enables building owners to better protect the environment. This consolidation restricts the use of fuel and refrigerants to one common location that can employ tighter emission controls. Other environmentally friendly strategies for campus energy plants include the use of chemical-free water treatment for chiller plants; low NOx burners for boilers; and refrigerants with low or no ozone depletion potential.