Small wind / Buyer questions
Energy and economics
Can a diesel generator's rated fuel consumption estimate savings from wind at partial load?
The short answer
A diesel generator's rated-load fuel figure is not enough to estimate savings when wind changes its partial-load operation. Fuel consumption can include a component that remains while the engine is running. The assessment needs the relevant fuel curve, dispatch assumptions and service constraints rather than one universal litres-per-kWh factor.
Obtain the applicable operating evidence
Request manufacturer data or suitable measured fuel and electrical-output records for the actual generator and conditions. Identify whether figures describe instantaneous operation, an averaged duty or a test point. Keep units and the generator configuration explicit.
Do not infer fuel savings from nameplate electrical efficiency alone. The relevant change is between the operating states before and after wind is introduced, not between an arbitrary full-load point and zero generation.
Model the change in dispatch
Determine whether wind reduces generator output, eliminates some running periods or has limited effect because of minimum loading or system-support requirements. These cases can have different fuel consequences even for the same amount of wind energy.
Use a documented fuel relationship in each relevant interval. Any extrapolation beyond supported data should remain visible. A linear approximation may be useful in a defined range, but its coefficients and limits need a basis rather than a convenient default.
Reconcile fuel and energy results
Report displaced generator electricity, reduced running hours where applicable and estimated fuel savings as separate outputs. Check that startup, standby and retained service assumptions are treated consistently. Keep delivered fuel price and logistics assumptions distinct from physical fuel consumption.
The handover should retain the curve source, dispatch rules and sensitivity results. This lets the buyer compare a wind addition on evidence without claiming a fixed fuel saving for every generated kWh or an unverified compatibility between the turbine, converter and existing generator.
Sources
- HOMER Pro documentation: generator fuel-curve inputs and operating-load relationship
- System Advisor Model documentation: commercial cash-flow and financial assumptions
Examples are illustrative. Confirm product-specific performance, compatibility and supply scope in the applicable documents.