Horizon and loss assumptions
Horizon, soiling, snow, availability, and AC losses.
Reviewed
What this is for
Everything the year does to production besides the weather file itself. A horizon is not a keepout: it shades everything at once, adds no electrical mismatch, and its interpolation wraps across north. Soiling is monthly because a dry-season build-up that one wet month clears is not the same array as one losing the annual average every month, and the difference lands on the months with the most sun.
Steps
- Open Conditions, select a set.
Horizon
- The Horizon card is the far skyline. Open horizon means nothing blocks the sky, or no profile has been fetched yet. Fetch terrain horizon asks the irradiance service for this cell. The plot is north-clockwise around the compass. A keepout on the designer is a different thing: that is a nearby object, and it lives on the design.
- A horizon saves the moment you fetch it or pick one from Profile. It does not wait for Apply, and it marks every run against this set as older than the conditions.
Losses
- Losses: soiling month by month (January through December), AC losses, Availability, first-year degradation, and Degradation after year one. The simulated year is year one and carries the first-year figure only. The ongoing rate reaches the money through a financial model, never through this run. None of it is saved until Apply.
- Leave a soiling month as the default if you have not measured one. Inventing a figure nobody has measured is worse than leaving the default.
- Model snow is off until you turn it on. The model list is disabled until then. Snow on a site that never sees it is a loss that did not happen.
- Add a custom loss is a named percentage for a real cause the engine does not model, a transformer for instance. It is applied after the inverter with AC losses and availability, lands in the last waterfall step, and gets its own slice under its own name in the donut. A custom loss called "contingency" is a guess wearing a name.
Uncertainty terms live on the Weather tab, not here. A dash is a contributor nobody has stated. Filling one with zero "to be conservative" shrinks the combination. That is P50, P90, and uncertainty.
Tips and common mistakes
- Horizon fetch and weather fetch are two buttons. One year of irradiance is not a skyline.
- Availability is uptime, not a tariff outage. Planned interruptions are a storage and dispatch input, on the site's supplier and group.
- Do not copy an annual soiling average into every month "to be conservative". That punishes the sunny months twice if the dirt actually sits in winter.