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In this paper a probabilistic model is presented to optimize the expansion of distributed generation in the electricity distribution network. The Monte Carlo technique is used to obtain probability distributions of the desired variables, such as: power flows, output power of distributed generators, costs, etc. The analysis of the results leads to optimized criteria for the expansion of distributed generation (DG) in distribution networks.

A high penetration of distributed generation in electricity networks makes it necessary to adapt the network to the new conditions of generation and consumption. Storage units can be converted within a few years in another element of power grids. Therefore, it is necessary to analyze the network to determine the optimal location of distributed generation, which lines need to be built or where to install the storage units. This paper presents a model of power network planning which takes into account the effect of the expansion of distributed generation. The results obtained show the continuing replacement of conventional generation by distributed generation and the importance of storage units in this process of replacement.

In this paper we present a techno-economical analysis of grid-connected lithium batteries. A time-of-use (TOU) electricity tariff will be considered so that batteries can be charged during hours of low electricity price and discharged during hours of high electricity price. Four cases will be studied, depending if it is allowed or not to inject electricity to the AC grid during the discharge of the batteries and also depending if there is photovoltaic generator. Case 1: batteries discharge just to meet the load (no electricity injection to the grid); Case 2: Batteries discharge meet the load and also inject to the grid; Case 3: Photovoltaic generator + case 1; Case 4: Photovoltaic generator + case 2. In all the cases, the Net Present Cost (NPC) is calculated. All the cases are compared to the base case of supplying electricity without batteries. The Li-ion battery cost must be reduced at least 70% to be profitable in this applications. In that case, if selling electricity to the AC grid is allowed and the selling price is 70% of the price of the electricity, the battery system can be a good option, with or without PV generator.