fuel value calculator by usda

8/11/2019 Fuel Value Calculator by USDA

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Fuel Value Calculator(or use this easy-to-use spreadsheet to calculate)

The Fuel Value Calculator is a tool that can be used tocompare typical unit costs of various fuels. Originallydeveloped by A.B. Curtis, Jr., of the USDA Forest ServicesSouthern Region, the fifth edition of the Calculator hasbeen published in cooperation with the USDA ForestService, Forest Products Laboratory, and the Pellet FuelsInstitute in Arlington, Virginia. The following informationis to be used in conjunction with the Calculator, which isavailable by contacting the Forest Products Laboratory.

Cost ComparisonHere, two examples are provided to show how wood can bea competitive alternative to fossil fuels. Based on typicalboiler efficiencies1 for fuel costing $3/million Btu($15/million Btu), the examples show that you can buygreen wood (at 50% moisture content (MC) on a wet basis)with the same heat content as natural gas or electricity for$17.22/ton ($86.10/ton) compared with $2.46/1000 ft($12.30/1000 ft) for natural gas or $0.010/kWh($0.050/kWh) for electricity. The calculations are useful indeveloping a budget for annual fuel costs.

$3/million Btu

1. Green wood (50% MC): 5.74 million Btu/ton

$17.22/tonton

Btumillion5.74

Btumillion

$3=

2. Natural gas: 0.820 million Btu/1000 ft3

3ft$2.46/10003ft1000

Btu820,000

Btumillion

$3=

3. Electricity: 3,340 Btu/kWh

$0.010/kWhkWh

Btu3,340

Btumillion

$3=

$15/million Btu

1. Green wood (50% MC): 5.74 million Btu/ton

$86.10/tonton

Btumillion5.74

Btumillion

$15=

2. Natural gas: 0.820 million Btu/1000 ft3

3ft0$12.30/1003ft1000

Btu820,000

Btumillion

$15=

3. Electricity: 3,430 Btu/kWh

$0.050/kWhkWh

Btu3,340

Btumillion

$15=

F l N t h ti l C t/ it
http://www.fpl.fs.fed.us/tmu/documents/fuel-value-calculator.xlshttp://www.fpl.fs.fed.us/tmu/documents/fuel-value-calculator.xls


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The concept of latent heat of vaporization is important to

understand in order to know the useful energy availablefrom any type of fuel that contains water, including wood,

coal, and peat. In wood or wood products, this water is

referred to as moisture content (MC). Commonly, watermakes up half the weight of a living tree and, if wood is

used for fuel, its MC is a factor in determining its energy

value.

In the combustion process of wood, energy in the fuel isneeded to change water into vapor, and the amount of

energy required is dependent on the MC of the woodthe

higher the MC, the more energy required. The amount ofenergy absorbed as water changes from a liquid to a gas at

its normal boiling point is called latent heat of vaporization.

The quantity of heat generated by a combustion process iscalled the heating value, heat of combustion, or the

calorific value. The higher heating value (HHV) of a fuel is

the amount of energy available from its complete

combustion, including the energy from condensing the

water vapor that results from the combustion. The lowerheating value (LHV) is the HHV minus the energy from

condensing the water vapor that results from the

combustion. All fuels generate some water from hydrogenduring the combustion process; this also results in a lowerheating value.

In the operation of heating boilers, the exhaust (flue gas)temperature is generally kept high enough to prevent

condensation of water vapor. When condensed water mixes

with other flue gas constituents, such as sulfides and

chlorides, corrosive acids are formed. These corrosive

acids can damage breachings, flues, heat exchangers, orother vents. Therefore, the latent heat of vaporization, or

the heat required to increase the temperature to the boiling

point, is not available for making steam, hot water, oruseful heat.

The attached chart shows efficiency, heating values (gross

and net), and cost comparisons for various fuel types.

Residential Heating ExampleDuring a heating season, between 50 and 150 million Btu

of energy are typically used to heat an average-sized home.

For comparison, the following chart shows an example ofexpected annual costs of heating a home (assuming 100

million Btu of energy for the heating season) using natural

gas, propane, fuel oil #2, seasoned firewood, wood pellets,and electricity. Note: Although natural gas, fuel oil, and

propane can be sold per therm, which measures heat

content of the fuel, the example uses volume (1000 ft 3of

natural gas 1 million Btu; 1 million Btu = 10 therms).

The comparison shows that seasoned firewood is the leastexpensive fuel, with natural gas and wood pellets a close

second and third. To determine whether seasoned firewood

is the fuel of choice, you need to compare heating systemsand determine how much time and effort you are willing to

spend processing and handling this fuel. Wood pellets

require less handling but still more than fossil fuels. Also,fossil fuel heating systems typically cost less, sometimes

significantly so, than firewood and wood pellet furnaces.

Example of Annual Home Heating Costs Using Various Fuelsa

Fuel

Grossheating value

bEfficiency

(%)Net

heating valueb

Fuel requiredfor 1 million Btuof usable heat

Averagecost/unit

Totalannual

fuel cost

Natural gas 1.03 million Btu/1000 ft3 80 0.82 million Btu/1000 ft3 1,220 ft3 $7/1000 ft3 $854

Propane 91,200 Btu/gal 79 72,000 Btu/gal 13.86 gal $1.25/gal $1,730

Fuel oil #2 138,800 Btu/gal 83 115,000 Btu/gal 8.68 gal $1.40/gal $1,220

Seasoned firewood 20 million Btu/cord 77 15.4 million Btu/cord 0.065 cord $115/cord $747

Electricity 3,413 Btu/kWh 98 3,340 Btu/kWh 299 kWh $0.08/kWh $2,390

Premium wood pellets 16.4 million Btu/ton 83 13.6 million Btu/ton 0.073 ton $120/ton $882aBased on 100 million Btu of energy for the heating season.

b1000 ft 1 million Btu; 1 million Btu = 10 therms.


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fuel value calculator by usda

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