Theoretical and experimental researches on energy generation and storage technologies in photovoltaic systems

Keywords: Energy storage technologies, photovoltaic systems, batteries, supercapacitors, grid connected solar inverters

The continuous dependence of the society upon new energy resources makes the energy – particularly the electrical energy – to be an essential element in all fields of the current economy. The enhancement of research on renewable energies as alternative power sources altogether with the constraints required by existing standards, are linked with energy efficiency, environment protection, emission reduction and fossil fuel consumption, quality of life, development of intelligent energy storage and management systems/grids, and increase the lifetime of energy storage and generation devices. On one hand, current trends are moving towards increasing the performance of storage devices, and on the other hand, aims to implement efficient energy management systems in order to optimize the energy transfer from the primary source of energy to the consumer by using intelligent techniques of command and control.

In this context, the author considers it appropriate to investigate energy storage techniques used in photovoltaic systems. Special attention is given to solar systems that use batteries and/or supercapacitors for energy storage and to photovoltaic systems connected to the public network. The major advantage of BES and/or SCES systems is that they can be mobile, independent from the power grid, and the main advantage of the grid tied energy systems is that they avoid the direct use of storage devices, known to be subject to aging. To speak about the efficient use of energy resources, it requires the public energy system to be equipped with energy storage facilities.

Theoretical and experimental realized researches have practical value for:
◦ Energy storing using battery/supercapacitor chargers;
◦ Determining the specific parameters of the energy storage devices and evaluation of their performance in different rates of charging/discharging;
◦ Using the proposed model for simulation of photovoltaic systems in order to improve the design and the implementation of them;
◦ Testing different charging methods based on MPPT algorithms, used in photovoltaic energy conversion systems;
◦ Practical implementation of a solar micro-inverter having power factor close to unity and harmonic distortion factor less than 5%;
◦ Using solar energy both, in photovoltaic mobile systems and in grid-connected micro-systems with high efficiency