PV_ System grid connected management using automatic changeover switch

Abstract

Integrated renewable energy systems, which use different energy sources such as solar energy, hydro-energy and wind to satisfy various energy needs, are well suited for intertropical countries. Solar energy provides free energy solutions for many countries near the equator, including Rwanda. Even if solar energy technology keeps on its advancement, hydropower remains the principal power source in Rwanda even though it is expensive. Some households, schools, and health centers are getting solar energy systems from donations; others bought them due to the arrival of the national grid. Those systems are not used efficiently, they use them when there is a national grid cutoff. The intermittency of solar energy makes users shift from solar energy to the national grid. REG (Rwanda energy group) has set an energy strategic plan since 2015 for achieving a minimum of 512 MW of energy production in 2024/2025 to meet the total energy demand. They wanted to feed electrical energy 52% grid-connected and 48% for off-grid. The offgrid systems are often to be solar energy systems. Many African countries have an issue of overload on their national transmission line due to high population numbers. These days Rwanda is expanding transmission lines, but also it is not sustainable. Main research showed that the solution to the energy demand of any country is distributed generation (DGs). This study was focused on renewable energy integration, where solar energy systems will be connected to the national grid at the consumer level to reduce the heavy load on the national grid and to save money because DGs make energy cheap. The system name is PV system grid connected; solar energy uses the national grid as a backup. This system uses an advanced power electronic device called an automatic changeover switch. The system works automatically, when solar energy is weak, the device switches to the national grid automatically and even television continues to display. This study focused on the management of energy produced from solar energy in different households, schools and health centers also connected to the national grid. These energy users do not use solar, energy efficiency due to the solar intermittent. The case study was an electrical shop located in Gitega sector, Kigali city, where even Covid-19 measures could not interrupt the study. A solar energy system of 273 W was built and connected to the national grid that the shop uses. They use 273 W (Pmax) in fourteen hours (14 h). The total daily energy consumption is 3.822 kWh. The results showed that 97.5% of the energy from the national grid was saved.