#Slope of a graph m generator generator#
If the fuel units are m 3, the efficiency equation becomes:įinally, if the fuel units are kg, the efficiency equation becomes:Īs an example, you can analyze a 75 kW generator that burns diesel. HOMER plots this relationship in the efficiency curve in the Generator Inputs window when the fuel units are L. This equation gives the efficiency of the generator as a function of its relative output. If we divide numerator and denominator by Y gen, the capacity of the generator, and define a new symbol p gen for the relative output of the generator ( p gen = P gen / Y gen ) then the efficiency equation becomes: If the fuel units are L, the efficiency equation becomes: If the fuel units are m 3, the factor of 1000 is unnecessary, and the equation for m fuel is as follows: The following equation gives the generator's fuel consumption in units/hr as a function of its electrical output: HOMER assumes that the fuel curve is a straight line. The fuel curve describes the amount of fuel the generator consumes to produce electricity. For example, "units/hr" means L/hr for a fuel denominated in L, and kg/hr for a fuel denominated in kg. This section uses the term "units" to mean the units specified for the particular fuel, whether kg, L, or m 3. Similarly, if natural gas is denominated in m 3, its price is in $/m 3 and the fuel curve inputs for a natural gas engine are in m 3/hr/kW. For example, if diesel fuel is denominated in L, the price of diesel fuel is in $/L and the fuel curve inputs for a diesel generator are in L/hr/kW. After you create a fuel, all the inputs that relate to that fuel use the specified units. For example, you may choose to denominate liquid fuels (e.g., diesel, gasoline, and ethanol) in L, and gaseous fuels (e.g., natural gas, and hydrogen) in m 3.
When you create a new fuel, you choose which units you want to use for that fuel.
The units of the fuel curve inputs sometimes change when you select a different fuel from the drop-down menu because, in HOMER, fuels can be denominated in units of kg, L, or m 3. This section explains how HOMER creates the graph from the fuel curve inputs. In the Generator Inputs options, when you enter the fuel curve inputs, HOMER draws the corresponding efficiency curve.
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