The objective is to minimize the expected cost in the whole system subject to all constraints. In principle, this solution will coincide with the outcome in a well-functioning electricity market. The simulated system can e.g. be the Nordic system or Northern Europe. The basic time step in the EMPS model is one week, with a horizon of up to ten years. Within each week, the time-resolution is 1 hour or longer.
In the strategy evaluation, incremental water values (marginal costs for hydropower) are computed for each area using stochastic dynamic programming. A heuristic approach is used to treat the interaction between areas. In the simulation part of the model total system costs are minimized week by week for each climate scenario (e.g. 1931 – 2012) in a linear problem formulation.
Hydropower: Each area in the model is an EOPS module. It is therefore possible to include a detailed representation of hydropower. In the simulation part, total hydro power production for each area is calculated. Thereafter, a rule-based reservoir drawdown model distributes production among all available plants within each area.
Other generation: Thermal power plants can be described individually by capacity, marginal cost (or fuel-type and efficiency), and start-up costs (optional). Plant outages may be modelled by an Expected Incremental Cost method. Wind-power and solar-power have zero costs and stochastic generation.
Transmission: A capacity and availability is specified for each controllable transport channel. Detailed power flow can also be applied, cf. Samlast/Samnett.
Consumption: For each area demand can be specified by annual levels, within-year weekly profile, and within-week hourly profile. During simulation, the demand is affected by prices and temperatures.
Some tasks the EMPS-model may perform:
- Forecasting of electricity prices and reservoir operation
- Long term operational scheduling of hydro power
- Maintenance planning (transmission or production)
- Calculation of energy balances (supply, consumption and trade)
- Utilization of transmission lines and cables
- Analysis of overflow losses, and probability for curtailment
- Analyse interplay between intermittent generation, hydropower and thermal power
- Investment analysis; system development studies
- Calculation of CO2-emisssions from power generation