Improving Reliability Indices of the Autonomous Power System of Crete Island Utilizing Extended Photovoltaic Installations

Abstract

Renewable energy sources (RES) have significantly helped in meeting the electricity demand of Crete, with their share in the energy balance to account for about 25% of the annual electricity production for the past five years. The contribution of photovoltaics (PVs) has been especially significant for the past three years, offering 10% in the peak demand, during summertime. This paper investigates what the capacity credit would be, i.e., up to what extent increasing existing PV capacity by about 20% can be considered as certain, to avoid installing thermal power units. In order to do so, probabilistic techniques have been applied to quantify the load that the installed thermal units in the Cretan power system should be able to meet at any time. In addition, the effect of the additional PV capacity to power system's reliability is evaluated, introducing a new reliability index and taking into account actual data, regarding the planned and unplanned thermal units' maintenance. Two scenarios have been examined using actual hourly data for load demand, PV, and wind production from the island power system of Crete. In the first scenario, the calculations were carried out considering the operation of the Cretan power system in its current state, while in the second scenario it was assumed that the PV production has been increased by 20%. Furthermore, we examine how the maximum value of capacity credit can be achieved as the PV installations are extended. In this regard, there is an upper limit of the additional PV capacity that leads to the maximum value of capacity credit.Energies 2020, 13, 64 2 of 15 much widespread in any power system as PVs as they are not modular with the exception of solar dishes [9] and face more sitting constraints than PVs. This is the reason for focusing on PVs and their potential reliability impact on island power systems like Crete.There have been numerous studies regarding the potential benefits of PVs already since 90 s. In [10] the value of PVs for voltage support, loss, and peak reduction, distribution systems are studied while comparisons are made with the conventional and widely used methods for voltage control and loss minimization. In another study [11], the value of PVs for society have been examined from both the consumer and the utility perspective, claiming that the decentralized PV systems have a higher value for the society due to the fact that the customers are involved in their own electricity supply. Generally, the presence of solar electricity resources, such as any other distributed generation, can eliminate or delay the need for investments on transmission or distribution grid level [12]. According to a past study [13], strategically sited PVs provide grid support to substation transformers by reducing their oil temperature due to the lower demand caused by PV.PVs have greatly helped in electrifying rural areas such as in middle northeast Africa and southeast Asia countries [14], Honduras [15], and desert regions [16], as an alternative to grid extension or fossil fuels....