NOx Emissions Impacts from Widespread Deployment of CHP in ...

NOx Emissions Report
operating scenarios. Groupings within building cluster types, such as hospitals (small,
medium, and large), were determined by both the calculated minimum building sizes for
feasible CHP adoption, as per the BCHP model, and the distribution of the building size
data from the HCAD database. Based on initial BCHP runs, facilities of less than 40,000
square feet were generally excluded, with the exception of hospitals, fitness facilities,
data processing centers, and libraries, where 20,000 square feet served as the cut-off
threshold.
Using this process, building assumptions including building size, number of stories,
building age, building envelope considerations, HVAC and boiler equipment size and
age, and building electrical and thermal loads were established for each building subcategory,
thereby creating a detailed prototype building with specific and detailed
characteristics suitable for computer modeling. Also at this time, consideration was given
to estimating the detailed equipment and operating strategy that an on-site CHP system
would most likely employ. The detailed building assumptions used for each prototype is
presented in Appendix A.
2.3 Modeling Building Performance
Computer modeling was used to determine the energy and environmental impacts
resulting from adoption of CHP systems at each of the prototype buildings. Computer
modeling was first used as part of an iterative process to establish the size and
configuration of CHP systems likely for each prototype building type and to compare the
energy and environmental impacts of the baseline and CHP alternatives. The NOx
emission implications for each building type are an output of the computer model and
discussed below and shown by prototype in Appendix A.
A detailed description of the modeling effort is provided below.
2.3.1 Prototype Building Models
The BCHP model and detailed spreadsheet models were used in the analysis of prototype
buildings. BCHP incorporates the program DOE 2.1, which is a building simulator that
uses detailed building characteristics and local weather data to generate hour-by-hour
electrical and thermal load profiles. The model’s algorithms automatically determined
HVAC systems and plant sizes.
A total of eleven BCHP models were developed. Due to similarities between building
types, these twelve models were considered to be suitable to model all of the desired
prototype buildings, although in some cases minor modifications were made to the model
to more accurately reflect anticipated building operation and use. For some prototypical
buildings, spreadsheet analysis was used to modify the results of the BCHP model to
improve accuracy across prototypical building types. The eleven BCHP models included:
• Healthcare (4): large, medium, and small hospitals, nursing homes
• Hotels (3): large, medium, and small
• Office Buildings (2): medium-rise office towers, colleges (with on-campus living)
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