A New Approach to Estimate from Monitored Demand Data the Limit of the Coverage of Electricity Demand through Photovoltaics in Large Electricity Grids

In a traditional large electricity grid without storage, there is a limit to the maximum photovoltaic energy that can be consumed as the demand and generation may not match, either in magnitude or in time. This paper aims to provide a new method to estimate the limit of the coverage of electricity demand by photovoltaics in large electricity grids. This new method eliminates the random and the periodic variability over time as it is based either on the load duration curve for demand and the output duration curve for PV generation. We will assume there is no energy storage or inter-network exchanges. Moreover, conditions for the best scenario for photovoltaics are provided in order to estimate the upper limit: photovoltaic overgeneration is not considered and a complete system flexibility is assumed. The knowledge of this limit will manage to provide not only a reference for the planning of the energy sector but also to analyze the viability of the integration of future photovoltaic projects in the electrical system. In order to illustrate the method, several large electricity grids have been analysed in order to determine the aforementioned limit. Values between 19.3% and 29.9% have been obtained.

Development of load duration curve system in data-scarce watersheds based on a distributed hydrological model

Many developing countries and regions are currently facing serious water environmental problems, especially the lack of monitoring systems for medium- to small-sized watersheds. The load duration curve (LDC) is an effective method to identify polluted waterbodies and clarify the point sources or non-point sources of pollutants. However, it is a large challenge to establish the LDC in small river basins due to the lack of available observed runoff data. In addition, the LDC cannot yet spatially trace the specific sources of the pollutants. To overcome the limitations of LDC, this study develops a LDC based on a distributed hydrological model of the Soil and Water Assessment Tool (SWAT). First, the SWAT model is used to generate the runoff data. Then, for the control and management of over-loaded polluted water, the spatial distribution and transportation of original sources of point and non-point pollutants are ascertained with the aid of the SWAT model. The development procedures of LDC proposed in this study are applied to the Jian-jiang River basin, a tributary of the Yangtze River, in Duyun city of Guizhou province. The results indicate the effectiveness of the method, which is applicable for water environmental management in data-scarce river basins.

DETERMINATION OF LOAD DURATION CURVE (ROSSANDER GRAPH) FOR THE REGIONS OF UKRAINE

The purpose of this work is to determine the duration of the ambient air temperatures of different gradations during heating periods in different regions of Ukraine, based on the climatic data for 2005-2018 and the construction of load duration curves for the respective regions. The load duration curve (Rossander graph) is used to determine the number of maximum thermal load using hours, as well as in cases where the thermal load is provided by several sources - to determine their level of participation in the total annual heat energy production. It is important for a more accurate technical and economic evaluation of implementation results for some thermal energy sources. The climatic data of meteorological stations located in the regional centers of Ukraine and the capital of Autonomous Republic of Crimea, or as close as possible to them, were used for the study. The climatic data of heating periods from the autumn of 2005 to 2018 were considered. As the result of study, the duration of various degrees of ambient air temperature in the heating period was determined for all the regional centers of Ukraine. Taking into account the significant climatic differences in the regions of Ukraine, the results were analyzed separately for two groups of regions, for which, according to averaged data, load duration curves were determined. The examples of using of obtained results for calculations are given. On the basis of obtained data regarding duration of ambient temperatures higher than +8°C during the heating season, the energy saving potential of implementation of weather-dependent regulation of heat energy production for heating purposes in different regions was theoretically estimated, which is, on average, 8.4% for the first temperature zone (north, center) and 13% for the second zone (south).