ORIGINAL COMPANY-CONTEXT PRACTICE
Evaluate an operational renewable forecast
Original practice scenario inspired by TotalEnergies SE's public business context; this is not a reported interview question or a description of its internal systems. A fictional energy desk forecasts next-day renewable generation using weather forecasts, equipment status, and realized output. Describe an evaluation that reflects information available when the forecast would actually be issued.
Written for independent practice using company context; this is not a verified question from a company interview.
A REASONED APPROACH
Model answer.
Replay each forecast origin using only data available at that origin. Realized weather and retrospectively corrected equipment status can make an offline model look stronger than its operational version.
Work through it
- Record issue timestamps separately from valid timestamps for weather forecasts. Select the version published before each simulated decision cutoff.
- Use rolling-origin evaluation, fit preprocessing within each training window, and compare against persistence and seasonally appropriate baselines.
- Report errors by horizon, site, and low-generation periods. Include missing-input behavior and interval coverage if uncertainty estimates inform scheduling.
Tradeoffs to discuss
- Historical forecast vintages may be incomplete. A smaller honest replay is more useful than a larger evaluation with silently substituted realized weather.
Common pitfalls
- Random row splits leak nearby temporal structure.
- Good aggregate error does not guarantee reliable performance during the operating conditions that matter most.