Small wind / Buyer questions
Energy and economics
Should an off-grid wind assessment examine consecutive calm hours separately from annual energy?
The short answer
An off-grid assessment should examine consecutive generation deficits because annual energy does not describe their duration. A system can generate ample energy across a year while having long periods when wind cannot meet demand. Backup, storage or permitted interruption must be assessed against the required service and its chronological conditions.
Define the service before counting calm hours
Record the critical load, allowable interruption and any flexible demand. Calm wind is not the only possible deficit condition: output can be positive but below demand. Likewise, not every low-wind interval creates a service problem if another verified supply is available.
Keep wind resource, equipment availability and load chronology aligned. A distribution of speeds alone does not retain the order needed to identify long deficit sequences.
Examine sequences with explicit assumptions
Use a suitable chronological generation model and load series to identify deficit duration and magnitude. If third-party storage is considered, its usable capacity, power limits, operating constraints and actual interfaces require separate evidence.
Do not size resilience from average daily generation or assume a windy day will immediately follow every calm day. Test relevant sequences and explain the historical coverage and uncertainty. A modelled result is conditional on those inputs, not a guarantee about the longest future deficit.
Connect the findings to a practical choice
Compare additional supply, demand flexibility and other alternatives on the same service basis. The result may favor wind as fuel-displacement generation while retaining a separately sized backup source. It may also show that wind adds little value for a particular small remote load.
The handover should report critical deficit cases, assumptions and responsibility for integrated system design. This prevents an attractive annual kWh total from being mistaken for evidence that one turbine can independently provide the required continuity of service.
Sources
- System Advisor Model documentation: wind-resource inputs and time-series limitations
- U.S. DOE Small Wind Guidebook: resource and siting background
Examples are illustrative. Confirm product-specific performance, compatibility and supply scope in the applicable documents.