Savings
derived from the use of the Bi-Fuel System are the result of the
differential between the cost per kWh charged by the utility and
the cost per kWh to produce power with a Bi-Fuel generator. Due
to the premium prices which utility companies usually charge for
on-peak electricity, it is often most viable to operate the
Bi-Fuel generator as a peak-shaver, whereby power is produced
on-site only during those hours when electricity is at it's
highest price from the utility.
In
order to determine the cost of producing power with a Bi-Fuel
generator, several factors must be considered including:
A typical example of Bi-Fuel savings for a
500 kW peak-shaving project would look as follows:
Facts
and Assumptions
|
| Fuel consumption @ 500 kW: |
35 gph (100% diesel) |
| Peak hours per year: |
1500 |
| Gas ratio: |
70% |
| Diesel cost: |
$0.95 per gallon |
| Natural gas cost: |
$0.40 per therm (100 scf) |
| Maintenance cost: |
$.020 per kWh (includes overhauls) |
| On-peak utility costs per kWh: |
$0.12 |
|
Bi-Fuel
Operations
|
| Diesel use per hour: |
10.5 gallons (35 gph x .30) |
| Diesel cost per hour: |
$9.98 (10.5 gph x $.095) |
| Gas use per hour: |
34.3 therms* |
| Gas cost per hour: |
34.3 therms x $0.40= $13.72 |
| Total fuel cost per hour: |
$23.70 |
| Total fuel cost per kWh: |
$0.047 ($23.70 ) 500kW) |
| Estimated maintenance: |
$0.020 (includes overhaul costs) |
| Total Bi-Fuel cost per kWh: |
$0.067 |
|
Savings
|
| Bi-Fuel savings per kWh: |
$0.053 |
| Bi-Fuel savings per hour: |
$26.50 |
| Bi-Fuel savings per 1500 hours: |
$39,750 (750,000 kWh) |
|
| * 1 gallon
#2 diesel = 140 scf natural gas based on #2
diesel hhv of 140,000 btu/gallon and natural gas
hhv of 1,000 btu/scf; 35 gph diesel x .70= 24.5 x
140 scf = 3,430 scf = 34.3 therms |
|
| In the case of
diesel prime power operations, the Bi-Fuel System will
provide savings to the operator relative to the cost
differential between the two fuels. In this case,
operational costs other than fuel costs are not
considered as these costs will be equal to or less than
100% diesel operation during Bi-Fuel operation: |
Facts
and Assumptions
|
| Fuel consumption @ 500 kW: |
35 gph (100% diesel) |
| Hours per year: |
8000 |
| Gas ratio: |
70% |
| Diesel cost: |
$0.95 per gallon |
| Natural gas cost: |
$0.40 per therm (100 scf) |
|
100%
Diesel Operation
|
| Diesel use per hour: |
35 gph |
| Diesel cost per hour: |
$33.25 |
| Diesel cost per year |
$266,000 |
|
Bi-Fuel
Operations
|
| Diesel use per hour: |
10.5 gallons (35 gph x .30) |
| Diesel cost per hour: |
$9.98 (10.5 gph x $.095) |
| Gas use per hour: |
34.3 therms* |
| Gas cost per hour: |
34.3 therms x $0.40= $13.72 |
| Total fuel cost per hour: |
$23.70 |
|
Savings
|
| Bi-Fuel savings per hour |
$9.55 |
| Bi-Fuel savings per 8000 hours |
$76,400 (4 million kWh) |
|