Page 176 - Sustainable On-Site CHP Systems Design, Construction, and Operations

CHP Economic Analysis 149

quality assurance of the model. Disadvantages of some software models may include limi-
tations in modeling unique CHP plant applications, the model may have flaws that are less
than initially apparent to the user, or require “tricking” the simulation model by adjusting
the input to model an aspect of the CHP scenario that the model does not appear to support.
Spreadsheet models can be built that allow for very detailed analysis of unique or “out of
the ordinary” CHP applications, or allow the modeling to report a unique aspect of the
results. Advantages of spreadsheet modeling, for example, Microsoft Excel, include the
ability to build as detailed and unique of a model as the user desires, and increased ability
to follow the logic behind the calculations. Disadvantages of spreadsheet models include
more time to initially create and check the model, a higher chance of errors if close attention
is not paid to detail, a lack of annual hour-by-hour calculation, and making even small
changes to the model once it is substantially complete can prove challenging.

Estimating Annual Operation and Maintenance Costs
Another important aspect of estimating the annual costs of the BAU case or a CHP plant
alternative in an LCC analysis is the annual operation and maintenance costs. These
costs include

• Preventative/periodic maintenance of equipment
• Costs of consumables (lubricants, urea, test gas for emissions monitoring, etc.)
• Repair of equipment
• Rebuilding equipment during the life of the analysis
• Cost of permitting and annual testing (i.e., permit to operate, emissions control
testing)
• Cost of operators and maintenance personnel
• Cost of administrative staff
Permitting and testing costs can usually be estimated by discussing with the author-
ities in charge of such permitting or tests, or from companies that provide those testing
services. Costs for operations and maintenance staff, as well as maintenance staff, can
vary largely from region to region and from facility to facility. Some facilities may already
have these staff positions covered, whereas some facilities will have to start from the
beginning in staffing their operation. Some CHP alternatives may be designed to
operate with minimal operator intervention, whereas other facilities (i.e., those that
produce high-pressure steam) may require full-time attended operation.
Most major equipment manufacturers can offer historical maintenance and repair costs.
Often time, maintenance contracts are available that provide all necessary maintenance and
repairs on either a flat annual rate or based on hours operated or plant output. Additionally,
publications are available which offer typical maintenance and repair costs based on sur-
veys of equipment already installed and operating at various facilities. Below is information
from an ASHRAE research project regarding prime mover maintenance costs.
Prime Mover Operation and Maintenance Costs
Table 9-3 provides reciprocating engine operations and maintenance (O&M) costs. It
should be noted that the fixed cost is approximately 6 percent of the total hourly O&M
for this prime mover size range.