The need for a significant reduction in the level of environmental pollution is imperative, because the signs of climate change are stronger and stronger. Unfortunately, however, the dependence on fossil fuels is still so large that in some States considerable resources are invested in the exploitation of underground oil and natural gas fields. For example, thanks to the melting of the glaciers caused by the thermal increase due to the greenhouse effect, in the near future we will proceed to the drilling of the seabed at the Poles, with a very high risk in case of losses of crude oil. In the United States, fracking is used to access fossil resources in the subsoil, with the consequent pollution of groundwater and even the triggering of earthquakes.

On the other hand, the boost to the use of renewable energy sources, especially in Europe, has faded as a result of the cancellation of incentives that favored its spread until a few years ago. Purchase prices for the end-user have been reduced considerably, but these must face an investment that will start to come back only after four or five years. This, in the time of economic crisis that we live, is certainly an obstacle to the diffusion, for example, of photovoltaic systems or systems for the production of wind power.

Italy is, according to the most recent data published by IEA (International Energy Agency's Photovoltaic Power Systems Program), the nation that has the highest percentage of energy compared to the needs (equal to 8%) produced by photovoltaic source.

Some countries, even at much higher latitudes, such as Germany, are however much ahead, as production from renewable sources, especially photovoltaic and wind power, is very significant, even equal to the electricity needs of the entire country on some Sundays of early summer. Other countries, such as Denmark and Sweden, are focusing a lot on renewable energy in general, especially on large-scale wind turbines, installed offshore: this policy will bring these states to energy independence in less than five years.

In Italy, as in all Mediterranean countries, environmental conditions make the use of solar power systems very convenient.

The energy production of a photovoltaic generator does not depend only on the conditions of sunshine and temperature at which it operates, but also on the type of control of the electrical variables, therefore voltage and current, at the terminals as well as the circuit that carries the energy towards the electric load or the distribution network. The complexity of the design and of the optimization of the controller and of the circuit depend on the non-linearity and the time variance, due to the atmospheric conditions, of the generator.

If we consider applications that include the integration of cells in pre-existing structures, especially in urban contexts (e.g. buildings, car park coverings), or related to mobility (e.g. integration in motor vehicles), problems linked to the control and management of the energy produced become much more complex and difficult to solve. In fact, in such cases, which involve a production of energy from a few hundred watts to a few kilowatts, the panels may have a different orientation with respect to the sun's rays, may be subject to shading, even partial, or to an accelerated and uneven degradation. For applications to mobility, these factors add a rapid variation in the level of sunshine the cells are subjected to, which can be much higher than that which are subject to the panels of a plant placed, for example, on the roof of a building.

Last but not least, in terms of control and optimization, there is the problem of managing the power flows from the photovoltaic generator to the loads and the distribution network, but also to and from an accumulation system such as a battery. In fact, the management of a so-called micro-grid requires control techniques and circuits for the processing of energy very advanced, which ensure a high performance in very different scenarios and that also ensure a life time to the entire system being as long as possible. From this last point of view, one of the devices that requires greater attention is the element of accumulation of the electric energy, whose state of charge and health must be appropriately monitored.

These themes are the key to success of modern energy systems for home use.

In fact, the economic incentives that until a few years ago were paid for the electricity produced - for example by the photovoltaic panels on the roof of the house - and released into the distribution network, are no longer available, and today the end user wants to face an expense for electricity availability in all conditions, even when network blackouts occur. This inevitably results in energy production, from renewable sources, and storage, all on site, through a plant that is as cheap as possible but also highly reliable.

DIEM's Electrical Engineering Group began research on photovoltaic systems, and more generally on the production of energy from renewable energy sources, in 2001. In more than fifteen years there have been numerous scientific achievements, awards, at national and international levels, collaborations with Italian and foreign companies, students trained in this field and now working in the research and development of prestigious universities and companies.

The Group's most significant contributions concerned the modeling of photovoltaic panels, control and power processing systems in general, monitoring and diagnosis of electricity storage systems.

The main results of the research activity were the numerous articles published in prestigious international journals, some of which (such as this 2005 document) are today a point of reference for the international scientific community in the area.

There were also numerous patents, whose rights were transferred to the University of Salerno, which include the members of the Research Group among the inventors. Other patents have been developed as part of research contracts with companies, such as ABB and Bitron. More generally, the collaboration with the electronics industry has been very intense and with prestigious partners (ABB, Texas Instruments, Bitron among others).

More recently, many of the scientific results have been achieved in some projects funded by the European Commission (FP7 and H2020), both in the photovoltaic sector, in sustainable mobility and in the diagnosis of electrochemical systems for the production of electrical energy from hydrogen.

All the research activities have been and are carried out also in collaboration with numerous prestigious foreign universities, with a very important impact on the training of Master Degree courses in Computer Engineering, Electronic Engineering, Mechanical Engineering and Management.