From ASHRAE GreenGuide: The Design, Construction, and Operation of Sustainable Buildings, Second Edition
HEAT GENERATORS (HEATING PLANTS)
Considerable improvements in the seasonal efficiency of conventional heating plant equipment, such as boilers and furnaces, were made over the last several decades. Designers should verify claims of equipment manufacturers by reviewing documented data of this equipment demonstrating the efficiency ratings.
Some unconventional equipment and techniques to achieve greater efficiency or other possible green building design goals are described in the GreenTips at the end of this chapter.
COOLING GENERATORS (CHILLED-WATER PLANTS)
Chilled-water plants are most often used in large facilities. Their benefits include higher efficiency and reduced maintenance costs in comparison to decentralized plants.
Generally, a chilled-water plant consists of:
Condenser-water pumps (for water-cooled systems)
Cooling towers (for water-cooled systems) or air-cooled condensers
Associated piping, connections, and valves
Because chilled-water temperature can be closely controlled, chilled-water plants have an advantage over direct-expansion systems because they allow air temperatures to be closely controlled also.
Often chilled-water plant equipment will be in a single central location, allowing system control, maintenance, and problem diagnostics to be performed efficiently. Chilled-water plants also allow redundancy to be easily designed into the system by adding one (or more) extra chillers, chilled-water pumps, condenser-water pumps, and cooling tower fans.
Electric chillers used within chiller plants employ either a scroll-, reciprocating-, screw-, or centrifugal-type compressor (in order of increasing size). Models can be offered with both air-cooled or water-cooled condensers, with the exception that centrifugal compressors today are water-cooled only. Absorption chillers, powered by steam, hot water, natural...
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