Modelling of small secondary energy storage units in long-term planning

Long-term planning involves the use of stochastic simulations to obtain reliability indices (loss of load expectation, unserved energy, etc.) and operation indices (expected ageing of components, expected operating costs). To make the use of probabilistic methods possible, the simulation interval should be large enough, and normally weekly or monthly intervals are used. When the simulation interval is greater than the storage autonomy and filling time of the storage facilities considered in the system, the behaviour of such “small” storage units cannot be properly described using the existing conventional models. To avoid this problem, a model for secondary energy storage units that allows the use of simulation intervals greater than the storage autonomy is presented. The model is validated with a real system using renewable energy sources, a diesel generator and a small electrochemical storage device