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FUEL SYSTEMS
Fuel systems provide the necessary supply of
energy that a manufacturing facility requires to operate heating,
cooling and process systems. The optimization of these systems
can reduce fuel expenditures which can be a costly investment.
With the advent of deregulation and the creation of a more competitive
utility market the opportunity for the choice of fuel supplier can
increase the cost effectiveness of fuel systems.
The following module containing the recommendations
below attempts to illustrate the potential savings that can be achieved.
General Rules of Thumb:
- The average cost of electricity is $0.05/kWh
- The average cost of natural gas $0.35/CCF
- The average cost of #2 oil is $4/MMBtu
- There are 2000 hours per year per shift
(based on the assumption that one shift is 8 hours per day,
5 days per week, 50 weeks per year)
- A typical boiler or furnace has
a combustion efficiency of 80%
- Switching from electric heat to
natural gas or #2 fuel oil can reduce heating costs by 78%
Notes:
Before choosing the following targeted recommendations READ THE
FOLLOWING:
Pay back estimates for the following recommendations will use the
equation below. They will vary depending on the, application,
type of installation, and purchase quantity of material and labor
associated with each recommendation. It will be up to the
person doing the analyses to use the URL references below each
equation to help estimate an implementation cost.
The data correlating to
the variables below each equation will be prompted for in order
to execute a calculation. Frequently the fuel cost (FC)
associated with the specific recommendation will be prompted for
in order to calculate the annual cost savings (ACS). Unless otherwise
specific to a particular recommendation the ACS will be
calculated as follows:
- Convert from one
fuel to another
- Reschedule and rearrange
multiple source heating systems
- Replace purchased
steam with steam generated in-house or other energy source
- Replace electrically
operated process or space heating system with fossil fuel combustion
equipment
- Replace electrically
operated domestic or service water heater with one using fossil
fuel
- Use fossil fuel powered
generator to substitute for purchased electricity during peak
demand periods
- Increased use of
electrical equipment
- Reduce rates
- Purchase gas
- Use common propane
source
1. Convert from one fuel to another
Typical fuel conversion options are as folows: Convert combustion
equipment to burn natural gas or oil; oil or gas burners to coal;
gasoline to diesel, use propane or natural gas for engine fuel;
burn a less expensive grade of fuel in existing equipment.
The following equation illustrates the savings potential when a
fuel change results in an increased efficiency.
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AEB = actual energy used in building
per year, MMBtu/yr (obtained from utility bills)
hc= current system efficiency
ha = anticipated system efficiency, with new
fuel
CYCF = current yearly cost for fuel,
$/yr
AYCF = anticipated yearly cost for fuel, $/yr
AUCF = anticipated unit cost for new fuel, $/MMBtu
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2. Reschedule and rearrange multiple source
heating systems
The attempt to burn less expensive fuels and to stagger or disconnect
redundant boilers can reduce operating costs. The following
equations illustrate these options.
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ER = energy rating of boiler to be disconnected,
BTU/hr
LF = load factor
HY = operating hours per year
h1 = efficiency of boiler to be disconnected
h2= efficiency of boiler to be used in it's
place
EC1 = average cost of fuel for boiler to be disconnected,
$/MMBtu
EC2 = average cost of fuel for boiler to be used in it's
place, $/MMBtu
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3. Replace purchased steam with steam generated
in-house or other energy source.
The following equation
illustrates the potential savings derived when steam generated
in-house is used for process or building system applications.
Typically this is feasible when there are redundant or backup
boilers that can effectively support the capacity for the required
steam demand.
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LBS = pounds of steam consumed per year,
lb/yr
LH = latent heat of steam, Btu/lb (at delivery pressure);
see Thermo-Tables for
value of latent heat.
LF = load factor (this is 1.0 unless the steam demand changes)
SC = average steam cost, $/MMBtu
FC = average fuel cost, $/MMBtu
h = anticipated overall efficiency of the new boiler
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4. Replace electrically
operated process or space heating system with fossil fuel combustion
equipment.
Under conditions where
it is feasible use a fossil fuel fired system (in cases where:
the fuel is available in the plant, the cost of the fuel is less
than the electricity cost, and when the process that is affected
is not specific to electric heating methods) as opposed to an
electrically heated one. The following equation illustrates
the potential savings that can occur.
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KW = kilowatt draw of current equipment,
KW
CF = conversion factor, KW to Btu/hr, 3413
LF = load factor of equipment (if load factor does not
change use LF=1.0)
HY = operating hours per year
CE = average cost of electricity, $/MMBtu
CF = average cost of proposed fuel, $/MMBtu
h = anticipated efficiency of fuel burning equipment
(Note: the efficiency of the electrical equipment is assumed
to be one)
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5. Replace electrically operated domestic or
service water heater with one using fossil fuel.
When the cost of available
fossil fuels are much lower than the current cost of electricity
a hot water heating system should be changed to reduce heating
costs. The following equation illustrates the potential
monetary savings that can be achieved.
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HWR = daily hot water requirement for
plant, gal/day
DPY = days per year plant is operated
CONV = conversion factor, 8.345 lb/gallon
C = specific heat of water, 1 Btu/lb-ºF
Tin = enthalpy of inlet water at assumed temperature, ºF
Tout = enthalpy of water to service at given temperature,
ºF
CFe = cost of electricity, $/MMBtu
CFf = cost of fossil fuel, $/MMBtu
h = anticipated efficiency of fossil fuel system
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6. Use fossil fuel powered generator to substitute
for purchased electricity during peak demand periods.
Typically this is done
using a diesel, alcohol, or gasoline generator. The following
equation illustrates the potential monetary savings that can be
derived when a system of this type is implemented.
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DS = demand savings, KW/month
DC = demand charge, $/KW (from electric bills)
MY = months per year
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7. Increased use of electrical equipment
In cases where the electricity
cost is less than the fossil fuel cost associated with the use
of each, the following equation illustrates the potential
savings. This cost difference will exist when a fossil fuel
system is too expensive to operate due to specific process demands.
The following situations of when this is the case are: replace
steam jets on vacuum equipment with electric motor driven vacuum
pumps; use electric immersion heating in tanks, etc.; replace
fossil fuel burning process or space heating/cooling equipment
with electrical equipment; replace city water for cooling with
recycled internally pumped water via a cooling tower.
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FFU = fossil fuel used, BTU/hr
h = efficiency of current fossil fuel burning equipment
HY = operating hours per year
CF = cost of fossil fuel, $/MMBtu
CE = cost of electricity, $/MMBtu
(Note: the efficiency of the electrical equipment is assumed
to be one)
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8. Reduce rates
Combine gas meters to reduce rates; restructure fossil fuel rate
schedules in order to obtain lowest possible rates. the following
equation shows the monetary savings that can occur.
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AGL = units of gas transferred to a lower
rate (contact utility about rate structure/change)
CR = current rate per unit (see utility bills)
LR = anticipated lower rate per unit (contact utility about
rate structure/change)
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9. Purchase gas
The purchase of gas directly from a contract gas supplier can reduce
utility charges. The following equation illustrates this potential
savings.
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CGB = current annual gas cost, $/MMBtu
(from utility bills)
UG = units of gas purchased per year MMBtu/yr (from utility
bills), see Data Conversions
for any unit conversions.
PR = proposed rate per unit of gas, $/MMBtu (contact utility
for rate structure/change)
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10. Use common propane source
Supply all work stations from a common propane source instead of
using individual propane cylinders. The following equation
illustrates the potential monetary savings that can be achieved.
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AGC = annual gas usage from cylinders,
gal/yr
EC1 = unit cost of individual gas cylinders, $/gal
EC2 = anticipated unit cost of direct propane, $/gal
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