Laboratório de Eficiência Energética em Edificações

1. STUDY OF PHOTOVOLTAIC POTENTIAL IN URBAN AREAS WITH DAYTIME LOAD PEAK R I C A R D O R Ü T H E R , P h.D. C A R O L I N A D A S I L V A J A R D I M OrientadorEng. Civil P A U L O K N O B , D r. Co-orientador INTRODUCTION OBJECTIVE Strategies to control the load curve mainly at the peak hours must start to be priority in the electricity sector. One option of displacement of this load is the use of photovoltaics (PV) connected to the utility grid. It is observed that for many feeders in urban areasthe peak load over the day, mainly due to air-conditioning loads, occurs when the solar availability is high. The load curves, for regions of "daytime consumption", will be analyzed and compared with the capacity of PV generation. To quantify through the Effective Load-Carrying Capacity (ELCC) the capacity of a PV power plant to effectively contribute to a utility’s capacity, reducing the peak of demand in regions in which the demand and solar incidence coincide. Universidade Federal de Santa Catarina Centro Tecnológico Departamento de Engenharia Civil EFFECTIVE LOAD-CARRYING CAPACITY - ELCC ELCC is defined as the ability of a power generator – whether PV or conventional – to effectively contribute to a utility’s capacity, or system output, to meet its load. Therefore ELCC for a PV system represents the PV’s ability to provide power to the utility when it is needed, which means the capacity credit of the PV power plant. Therefore, the ELCC of PV systems connected to the utility grid will be calculated, translating the capacity of PV plants of guaranteeing the supply of the load for a specific region analyzed. In urban centers, the peak load occurs mainly by commercial load (building) demand exactly when there is the highest solar energy output. So PV provides power when it is needed, thus displacing peak energy and reducing demand. PV generators located in areas with high PV capacity credits will also help on the transmission and distribution (T&D) system to relieve overloads, while reducing the need for costly T&D upgrades. Laboratório de Eficiência Energética em Edificações The figure represents the reduction of the peak load with the use of PV power plant. The minimum percentage of the reduction of the demand peak is represented by the Effective Load-Carrying Capacity. RESULTS OBTAINED IN FLORIANÓPOLIS - BRAZIL Power demand data of 11 of the 56 feeders suppying energy to the city of Florianópolis have been analyzed. The values of current are registered at intervals of one hour. Some feeders have these data registered from 01/08/2000 and others from 01/08/2001, with measurements until 30/04/2002. Although some feeders do not have registered data for a complete year, all of them have full data for the summer, which will define the coefficient and results being analysed in this work. Table 1: Identification of the 11 feeders For the calculation of the ELCC for each month of the year, clear days will be selected. This is due to the fact the along the year there are differences in solar irradiation and the demand curve has to be compared with the respective monthly solar generation curve. In order to calculate the ELCC it is necessary to obtain some values of the data base supplied by the local utility (CELESC, Centrais Elétricas de Santa Catarina), such as the identification of the feeder, Pico C that corresponds to the historical peak of demand, and day and hour when it occurred. Furthermore, ELCC is calculated based on the desired PV penetration levels. (i.e. the amount of PV generation in % of the total generation) The Effective Load-Carrying Capacity is determined by the difference between the peak of historical demand (Pico C) and the historical load peak considering the existence of PV plant (PicoCFV), divided by the power of PV plant (PotFV) and multiplied by 100. Based on ELCC values, it is not thought to exist high variation between the penetration levels of 1% and 5%; however, for penetration levels above 10% the values decrease significantly. It is perceived that by the calculations of the Effective Load-Carrying Capacity quite satisfactory values were obtained with regard to reduction of the demand peak. CONCLUSION Despite the fact that the peak of demand in Brazil is between 6:00 p.m. and 9:00 p.m., it was observed that 24 out of the 56 feeders analyzed in the city of Florianópolis present a daytime peak. In these cases the demand curve is related to the sun, mainly caused by the intensive air-contitioning use in urban centers. It was possible to quantify through the Effective Load-Carrying Capacity, the capacity of a photovoltaic plant of contributing effectively for the utility grid, thus reducing the peak of demand in regions where demand and solar incidence coincide, besides generating electrical energy. The dissemination of photovoltaic power plants in urban centers has a role of extreme importance as to the reduction of the peak of demand in the hours when the solar resource is coincident with the use of the energy. The periods of load peak are still a problem to the electricity sector; nevertheless there are studies under way that aim to tackle these problems in order to keep them under control. www.labeee.ufsc.br