POSY.jl Documentation

Model

POSY is a power-based power flow model. POSY's primary function is to determine electricity production and investment in new electricity production capacity so that the total cost is minimized.

Total cost is equal to the sum of all costs, including fixed costs (e.g. investment costs or fixed Operation and Maintenance costs) and variable costs (e.g. fuel costs or variable Operation and Maintenance costs) of installed technologies. Revenue of interconnection is also taken into account.

Optimization

The optimization is based on Linear Programming (LP) or Mixed-Integer Programming techniques (MIP) depending on the problem. To that end, POSY calls external solvers such as CPLEX, Gurobi, Cbc or GLPK (no solver is imposed).

Formalism

POSY is a capacity expansion + dispatch model with units clustering. Unit commitment is part of the dispatch process. The equality of supply and demand constraint is formulated in terms of power at each (hourly) timestep.

Time scale

POSY solves the problem for a given year, divided in 8760 hours.

Technologies

Models were created for the following sets of technologies:

Dispatchable: production is dispatchable and follows unit commitment. Subject to constraints such as up and ramping limits, minimum power output, startup and suptdown patterns, minimum uptime and downtimes.
Must run production: same as dispatchable, except the committed units always operate at full power.
Intermittent: electricity production follows an exogenous profile (based on historical time series for instance).
Storage: can store and discharge energy within charging and discharging capacity limits. The energy contain is also limited, and is subject to a storage efficiency factor. Can be subject to external intake (e.g. water inflow in water reservoirs). Production is considered as dispatchable. Storage is not subject to unit commitment.
Demand response: contains demand-side management, load shedding (value of lost load) and load shifting.
Interconnection: economic exchanges (imports / exports) with neighboring countries. Can be modeled either as fatal or as dispatchable and based on net transfer capacities (NTC) and spot price time series. Imports are considered as a costs, exports generate revenue.
System: can bear additionnal components such as transmission losses, and primary / secondary reserves.
Electrolysers: generate hydrogen from electricity.

Interconnection

POSY only models explicitly one territory. More precisely, exchanges with neighboring territories can be modeled, but the neighboring territories are modeled in a simplified way: they are only described through their electricity spot price time series and interconnector net transfer capacity with the territory modeled.