How wind, solar, and other renewable generation is forecast
Intermittent renewable generation is modelled using historical load factors to project forward generation profiles.
What is a load factor? The ratio of actual energy generated to the total installed capacity over a given period. For example, a wind farm with a 35% load factor generates 35% of its maximum theoretical output on average.
Average daily load factors for wind and solar are shown for Germany, Spain and Portugal.
Data sources
| Technology | Load factor source |
|---|---|
| Wind and solar | Historical data from Renewables Ninja (GB) and ENTSOE (Europe) |
| Run-of-river hydro | Historical availability data from ENTSO-E |
| Biomass | Historical availability data from ENTSO-E |
The model uses a 2018 weather year, with 15-minute interval availability data to construct representative load factor profiles. These are applied to projected installed capacity for each 15-minute interval across the forecast horizon.
Filling gaps where historical data is unavailable
For technology/country pairs where historical data is unavailable, or for technologies which don’t currently exist, substitution load factors are used based on countries with similar weather patterns that have available data.
| Missing data for | Substituted with |
|---|---|
| Netherlands | Belgium |
| Ireland | Great Britain |
Renewable subsidies can result in negative bidding prices
Renewable generators’ short-run marginal costs (SRMCs) are adjusted to reflect operational subsidies and renewable certificates. This can result in negative marginal costs — meaning generators are willing to pay to stay online.
Subsidised generators may receive payments for each MWh produced through:
- ROCs — Renewable Obligation Certificates
- CfDs — Contracts for Difference
- FiTs — Feed-in Tariffs
- REGOs / GOOs — Renewable Energy Guarantees of Origin / Guarantees of Origin
These subsidies are factored into bidding behaviour, which is why renewable generation sometimes bids at or below zero.