Page 155 - Sustainable On-Site CHP Systems Design, Construction, and Operations

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

Phases Purpose
Screening, scope, qualification To determine if the site is a good candidate for
a CHP system
Preliminary—Level 1 To determine whether a CHP is technically
appropriate and has economic potential
Detailed, comprehensive—Level 2 Use verified data to optimize and refine the
results of Level 1 study. This includes: optimal
equipment sizing, configuration, application,
operation, costing, etc.

TABLE 8-1 Types of Feasibility Studies

Feasibility Study Phases Time Frame Information Required Typical Cost
Screening, scope, 30 minutes Minimal site information, None
qualifications average utility costs
Preliminary—Level 1 4–6 weeks 1–2 years utility data, building $1,000–$10,000
operation, building loads
(HVAC, thermal, process),
future plans, future equipment
replacements, projected
energy costs, etc.
Detailed, 1–4 months Level 1 study with enhanced $10,000–$100,000
comprehensive—Level 2 modeling, and costing depending on size
and complexity

Source: Values taken from U.S. Environmental, Protection Agency—Combined Heat and Power Partnership—
CHP Development Handbook.
TABLE 8-2 Resources Required for Different Feasibility Study Types

Further, there are several feasible equipment and system configurations, and the best
among them has to be selected while considering issues of uncertainty and variability
over time of many of the inputs. Two general types of programs have been developed:
those meant for a preliminary feasibility analysis, and those meant for a comprehensive
system design detailed enough for final decision making. The level of inputs and the
type of detail necessary to specify equipment and systems for both objectives are obvi-
ously widely different.
Most of the simulation programs developed to date pertain to sizing of CHP
systems. This section categorizes and briefly describes the primary types of design tools
available. Because of the variability of the thermal and electric loads and the distinct
possibility that a cost-effective system may be one which is sized for intermediate loading
(i.e., neither base load nor peak sized), the design of CHP systems requires evaluation
of various system configurations and scenarios which is best done on a computer. The
three types of design tools are discussed below.