a b s t r a c tSerbia has wind with a good capacity factor, the respectable potential of which has not hitherto been utilized. There are a number of proposed wind power projects with an envisaged capacity of up to 2500 MW and the project documentation has been developed for 1300 MW. Within the existing feed-in tariff scheme, only 500 MW are eligible. This limitation is set in a conservative manner bearing in mind moderation (balancing) needs due to the variability of wind power generation. The existing Serbian energy system, with significant hydro generation, available pumped storage hydro capacity, and strong interconnections has many moderators for variable wind generation and for reliable technical performance of the grid. In this study, energy imbalances under different levels of wind penetration into the Serbian energy system were analyzed. Possible new moderation strategies for lowering energy imbalances due to wind integration were evaluated using the EnergyPLAN tool and are presented in this paper.

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Abstract:More variable renewable energy sources and energy efficiency measures create an additional flexibility gap and require a novel energy planning method for sustainable national energy systems. The firstly presented method uses only EnergyPLAN tool in order to decrease the flexibility gap in a national energy system. Generic Optimization program (GenOpt®) is an optimization program for the minimization of a cost function that is evaluated by an external simulation program, such as EnergyPLAN, which was used as the second method in this research. Successful strategies to decrease the flexibility gap are verified on the case of the Serbian national energy system using two methods for its structure design: (1) the iterative method, based on heuristics and manual procedure of using only EnergyPLAN, and (2) the optimization method, based on soft-linking of EnergyPLAN with GenOpt®. The latter method, named EPOPT (EnergyPlan-genOPT), found the solution for the structure of the sustainable national energy system at the total cost of 8,190 M€, while the iterative method was only able to find solutions at the cost in the range of 8,251-8,598 M€ by targeting only one sustainability goal. The advantages of the EPOPT method are its accuracy, user-friendliness and minimal costs, are valuable for planners. Highlights Heuristic and optimization method for sustainable national energy system structure  The same input assumptions resulting in different energy system structure  Both methods are successful in decreasing of the flexibility gap  The EPOPT method advantages are in the speed, accuracy and planner comfort  Advanced method for the sustainable national energy policy planning

Several Contracting Parties to the Treaty establishing the Energy Community of the South East Europe, currently in energy transition, have electricity production dominantly based on lignite which contrasts their new reality. Planning approach to designing a new feasible energy policy is presented in this paper. This novel approach in using EnergyPLAN tool stems from analysis of market operation of lignite thermal power plants on hourly basis, and quantification of the feasibility of the energy policy and its alignment with EU vision, and is presented in few scenarios. It was found out that the Serbian energy system is highly sensitive to the electricity market and CO2 tax increase, because the marginal costs for lignite generation will increase to more than 50?/MWh. Shifting in the merit order will be observed even at lower CO2 tax levels, because of the intensity of the emission of the electricity sector (calculated to be higher than 700gCO2/kWhel, according to current energy policy). Based on the increased use of renewable energy sources and more efficient energy conversion technologies, socio-economic and energy policy feasibility would be increased, while long-term marginal costs would be improved by 2?/MWh and emission intensity by 258 gCO2/kWhel, compared to the current energy policy. These contributions, shown in the Serbian case, are of general importance for other lignite dominated Contracting Parties to Treaty establishing the Energy Community.