Page 42 - Sustainable On-Site CHP Systems Design, Construction, and Operations

Applicability of CHP Systems 21

As stated previously, CHP is a specific application of DER. Several synonymous
terms have been used for CHP (MAC 2005):
• Cogen—cogeneration: combined production of both useful heat and power
• BCHP—building cooling, heating, and power
• CHPB—cooling, heating, and power for buildings
• CCHP—combined cooling, heating, and power
• Trigen—trigeneration: combined production of useful heating, cooling, and power
• TES—total energy systems
• IES—integrated energy systems
In order to keep consistency, only the term CHP or BCHP has been used in this
chapter. Some of the desirable conditions for BCHP to be competitive are
• Good coincidence between electric and thermal loads
• Thermal energy requirements in the form of hot water or steam
• Electric demand–to–thermal demand ratios ranging from 0.5 to 2.5
• Cost differential between electricity (total cost) and natural gas (total cost) of
greater than $12/10 Btu
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• Moderate to high operating hours (greater than 4000 hours per year)
• When electric power quality and reliability are important considerations
• Larger size building/facility, which allows lower initial cost of BCHP and larger
annual savings

Given these conditions, potential candidates for CHP can be grouped in two catego-
ries as
1. Commercial/institutional facilities (BCHP). Hospitals and other health-care facilities,
hotels, universities and educational facilities, supermarkets, large residential
buildings or complexes, research and development and laboratory buildings,
large office buildings, military bases, and district energy systems
2. Industrial facilities (ICHP). Chemical manufacturing, pharmaceutical and nutritional
units, food processing units, and pulp and paper mills
Given the uniqueness of industrial facilities, this chapter covers in detail the com-
mercial and institutional sectors wherein CHP systems are relevant. Detailed informa-
tion on CHP in the industrial sector can be found in “The Market and Technical Potential
for Combined Heat and Power in the Industrial Sector,” a report by the Onsite Sycom
Energy Corporation (Onsite 2000).

Applicability of CHP to Commercial and Institutional Facilities
It is difficult to precisely define the commercial and the institutional sectors given the broad
range of their activities. Commercial applications are typically driven by the energy used in
the building unlike industrial processes which are driven by manufacturing requirements.
In many commercial applications, the thermal load is not coincident with the electrical load
due to strong dependency on seasonal variations, and also due the limited operating hours.