Table 26-15 Selected Performance Data for Reciprocating Engine Cogeneration Plant Configuration.

Table 26-15 Selected Performance Data for Reciprocating Engine Cogeneration Plant Configuration.

individuals to operate and maintain the cogeneration facility, most of the labor component of the above estimate can be re-assigned from the maintenance budget to the staffing budget. In addition to this figure, the same two maintenance costs used for the GT-1 system were applied to each year of RE-1 system operation:

1. Maintenance of boilers, steam system, and related equipment totals $50,000 per year.

2. Four operators for 24 hour per day coverage, at

$70,000 each, totals $280,000 per year.

Plant Performance

Plant performance data was provided by Coltec Industries for the above system. Unlike the combustion turbines, reciprocating engine performance is largely independent of ambient air temperature — combustion air temperature is regulated by a heating system to within a narrow range. For this reason, the table of plant operations included for this system shows overall plant performance as a function of load only. Engine loading can vary within the range of 50 to 100%. When the load exceeds the capacity of one engine-generator, a second engine-generator is started and the two share the load equally.

As discussed above, hot water produced by the cogen-eration system will be utilized by both the boiler plant and the manufacturing process. For clarity, the simulation considers the thermal output of the engines in terms of equivalent steam generation at 1,000 Btu/lbm (2,325 kJ/kg). Table 26-15 shows a representative portion of the performance data for this cogeneration plant configuration, including electrical and equivalent steam production, as well as fuel consumption values for the plant. These values are used by the operations simulation.

Project Cost

The study team developed a project cost estimate to implement this cogeneration configuration, including the cogeneration equipment described above, extension of the existing boiler plant building structure over the cogenera-tion system, construction, and system startup. The cost estimate also includes the hot water distribution and makeup water heating systems necessary to utilize available recovered heat in place of steam. The total cost to complete this project was estimated at $15,320,000, as summarized in Table 26-16.

System Simulation and Economic Analysis

The study team developed a simulation of the facility's loads, boiler plant, electric utility service, and cogeneration systems to compare the annual operating performance and costs of each case. This simulation begins with the historical electrical and steam loads and determines which equipment is available to meet those loads. In the base case, all steam loads are met by the existing boiler plant and all electrical loads are met by the electric utility. In the cogenera-tion cases, the cogeneration equipment will carry all loads up to operating capacity, with the excess met by the boiler plant and electric utility.

The simulation is structured to sequentially step through each 4 hour interval for a calendar year. For example, Table 26-17 is an excerpt from the simulation showing the time, temperature, and facility loads for January 1 and 2. The column headings show how each of these sources will operate to satisfy facility loads.

The simulation calculates total monthly consumption for each source of energy and the cost to provide this service is calculated based on boiler efficiency, projected fuel costs, and the electric utility rate structure. The end result of this simulation for each case is an estimate of the total cost to operate the available equipment to meet facility loads. By comparing the total operating cost for each cogeneration case with the base case, the analysis determines the net projected savings.



Engine Generators


Electrical Switchgear




Hot Water System


Design/Construction Services


Overhead and Profit






Table 26-16 Capital Cost Summary for Reciprocating Engine Cogeneration System.
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