Page 157 - Sustainable On-Site CHP Systems Design, Construction, and Operations

130 T h e Fe a s i b i l i t y S t u d y

and their capabilities (Downes 2002). He concludes that Ready Reckoner which analyzes
the replacement of a boiler and chiller with a new boiler and an absorption chiller
requires a lot of input data pertinent to the existing boiler. On the other hand, Cogen-
Pro, which is also meant for the same purpose, requires very little building parameter
information, but is conservative in estimating recoverable savings. Finally, BEA requires
a lot of information about the building since a detailed simulation is performed. This
tool cannot be viewed as a screening tool since it performs hourly simulations.
Another convenient to use automated spreadsheet program is RETScreen (2006)
which can analyze CHP and district energy systems. It requires monthly values of
heating, cooling, and power loads and equipment description in order to perform the
simulations. It has the capability of adding different CHP equipment (either from an
existing database or new ones) and computes life-cycle costs and greenhouse gas emission
reductions as well. It has been validated by independent consultants and compared
with other models as well.
Orlando (1996) provides two detailed case study examples involving the design of
CHP systems for a hotel and for an industrial plant using load duration curves. Williams
et al. (1998) describe an approach to sizing cogeneration plants which is knowledge
based. This decision support is meant to reduce the time and money needed for sizing,
and is so structured that the design can be progressively improved depending on how
much information is available to identify the optimal size. An example illustrates this
approach.

Hourly Energy Simulation Tools for Design
Computer programs which fall in this category require hourly thermal and electric load
data and allow detailed system and equipment sizing.
COGENMASTER (Limaye and Balakrishnan 1989) compares CHP alternatives to a
base case system where electricity is purchased from the utility and the thermal energy
is produced on site. Different financing strategies can also be considered. The software
can be operated under different types of input specifications: (a) with a constant aver-
age load specified for each hour of the year, (b) hourly data for three typical days of the
year, and (c) hourly data for three typical days of each month.
CHP Capacity Optimizer (Hudson 2005) is an automated stand-alone spreadsheet
program which computes the optimal capacities of prime movers and chillers that will
maximize life cycle, net present value savings from the CHP system. It is based on a
methodology involving nonlinear optimization and hourly operation simulation of the
CHP prime movers and absorption chillers. The original intent of this tool was to help
equipment manufacturers in identifying sizes of CHP equipment most suited to meet
current requirements.
The Building Energy Analyzer (BEA 2004) was developed by the Gas Technology
Institute in 2002 and upgraded to BEA Pro in 2004. This screening software tool is meant
to simplify energy audits in commercial buildings and evaluate the technical and economic
potential of CHP systems in such buildings. Several modifiable templates of commer-
cial buildings are built in. It can be used to evaluate several on-site power technologies
and cooling options (such as absorption cooling and desiccant dehumidification). It
performs hourly calculations over each hour of the year and also includes data from
numerous locations and utility rates.
BCHP Screening Tool (Fischer and Glazer 2002) is also a comprehensive detailed
hourly simulation program. It is an add-on to DOE 2.1 in that the detailed hourly building