6.8 Rules of Thumb for CHP Engineering and Installation Costs(1)

This section covers important rules-of-thumb and a variety of other important information that you need to consider when quickly assessing a project.

6.8.1 Site Feasibility Screening

Consider CHP if:

  • Purchased electric power cost (kW + kWh) > 6¢/kWh
  • Operating hours > 3,000 (high peak electric rates) and > 5,000 (rates ~ 6¢/kWh)
  • Thermal loads are greater then 0.50 of the kW load equivalent and coincide with the expected operation of the power generation system
  • Electric utility buy-back Rate > 4¢/kWh
  • State energy efficiency incentives
  • Defined interconnection standards
  • Output based emissions standards
  • Utility receptive to CHP

CHP Equipment Characteristics

  • kW peak. / kW average < 1.40
  • Thermal peak. /Thermal average < 1.40
  • Thermal/Power ratio (T/P)(2) provides indication of prime mover
    • T/P = 3 to 20 consider boilers and steam turbines
    • T/P = 1 to 10 consider gas turbines and HRSGs
    • T/P = 0.5 to 1.5 consider reciprocating engines


6.8.2 General Equipment Costing

Guidelines for equipment costing are shown in Table 6-2.

Table 6-2: Equipment Costing Guidelines

Equipment

Installed Cost (Equipment Only)

New Oil or Gas Boiler

$25 per lb steam/hr

New Coal-Fired Packaged Boiler

$100 per lb steam/hr excluding scrubbers

Back-pressure Steam Turbine Generator

$300 - $500 / kW excluding boiler

Extraction/Condensing Steam Turbine Generator

$500 to $700 / kW excluding boiler

Gas Turbine Generator with Heat Recovery Steam Generator (HRSG)

$400 to $1,500 / kW

Reciprocating Engine Generator with HRSG

$800 to $2,000 / kW

Microturbine with heat recovery for hot water

$1,200 to $2,000/ kW

Small Reciprocating Engine with heat recovery for hot water

$800-$1,500/ kW

 

Guidelines for estimating maintenance costs are shown in Table 6-3.

Table 6-3: Maintenance Costs (labor and materials)

Prime Mover

¢ / kWh (including overhauls)

Steam Turbine

0.1 to 0.25

Gas Turbine

0.25 to 0.60

Reciprocating Engine

- Low speed 120 to 900 rpm (> 10 MW)

0.70 to 1.00

- Medium speed 900 – 1,200 rpm (1 – 10 MW)

1.00 to 1.20

- High Speed 1,200 to 1,800 rpm (< 1 MW)

1.20 to 1.50

Guidelines for operating costs are shown in Table 6-4.

 

Table 6-4: Relative Owning and Operating Costs

Prime Mover

¢ / kWh

Back Pressure Steam Turbine (excluding boiler)

1.5 to 2.5

Condensing Steam Turbine (excluding boiler)

5.0 to 7.0

Gas Turbine

3.0 to 8.0

Reciprocating Engine

4.0 to 6.0

Assumes $3.00 / MMBTU gas price

 

 

(1) dapted from the Wisconsin Cogeneration Short Course

(2)T/P = Average THERMAL load in 1,000 BTUH /[ Average Electric Load (kW) x 3,412 BTU/kWh]

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