Glossary
Plain definitions of the terms used in renewable power forecasting and electricity markets, including the Turkish market terms you will meet on this site.
Updated
- P10, P50, P90
- Quantiles of a probabilistic forecast. There is a 10% chance that output falls below P10, a 50% chance that it falls below P50, the median, and a 90% chance that it falls below P90. Read more
- Ensemble forecast
- A set of weather model runs started from slightly different conditions. Each member is an equally plausible version of the future, and their spread shows how certain the forecast is.
- Numerical weather prediction
- Forecasting the weather by solving the equations of the atmosphere on a global or regional grid. AI-based models learn the same task from decades of past weather.
- Weather front
- The boundary between two air masses. When a front passes, wind speed and direction, temperature and cloud can change within an hour or two.
- Ramp
- A large change in output within a short time, often caused by a passing front. Ramps cause most of the error in wind forecasts. Read more
- Hub height
- The height of a turbine's rotor centre. Model winds at fixed heights, such as 100 metres, are adjusted to it.
- Power curve
- The manufacturer's curve that turns wind speed at hub height into a turbine's electrical output, from cut-in to cut-out speed.
- Capacity factor
- Actual output over a period divided by what the plant would have produced at full installed capacity over the same period.
- Inverter clipping
- The cap on a solar plant's output when the panels could deliver more DC power than the inverters can convert to AC. Read more
- Day-ahead schedule
- The production a plant commits to for each hour or 15-minute period of the next day. Deviations from it are settled as imbalance. Read more
- Imbalance
- The difference between metered output and the committed schedule, settled at imbalance prices.
- Newsvendor rule
- With costs that grow in a straight line, the best commitment is the quantile equal to the cost of a surplus divided by the sum of the costs of a surplus and a shortfall. Read more
- nMAE
- Normalised mean absolute error: the average hourly absolute error divided by installed capacity. Read more
- nRMSE
- Normalised root mean square error. Like nMAE, but large errors weigh more.
- Bias
- The average of forecast minus actual output. A positive bias means the forecast is too high on average.
- Persistence forecast
- A simple baseline that assumes output repeats an earlier period, such as the same hour two days before.
- KGÜP
- Kesinleşmiş gün öncesi üretim/tüketim programı: the final day-ahead production schedule that licensed plants in Türkiye submit to TEİAŞ for each settlement period of the next day. Read more
- KÜPST
- The Turkish penalty for deviations from the final schedule beyond a tolerance band set by EPDK, the energy regulator. Read more
- EAK
- Emre amade kapasite: the available capacity a plant in Türkiye declares for each settlement period of the next day.
- PTF and SMF
- Türkiye's day-ahead market clearing price (PTF) and system marginal price (SMF). Imbalance prices are derived from both.
- GÖP
- Gün öncesi piyasası, the day-ahead electricity market in Türkiye. Bids close at 12:30 on the day before delivery.
- EPİAŞ
- Energy Exchange Istanbul, the Turkish market operator. It runs the day-ahead and intraday markets, settles imbalances and publishes transparency data.
- TEİAŞ
- Türkiye's transmission system operator. It receives KGÜP submissions through its TPYS system.
- YEKDEM
- Türkiye's renewable energy support mechanism. YEKDEM plants still pay their own imbalance and KÜPST costs.