To increase energy efficiency and reduce the environmental impact of its facilities, the Department of Electronics, Information and Bioengineering of the Politecnico di Milano installed a system of photovoltaic panels on the facade of Building 20. The positioning of the panels, which are invisible to the untrained eye, allows for limited production but offers a concrete sign of the Department’s strive for sustainability.

The performance of the panels is constantly monitored and can be viewed on the home page of the Department’s website. The data, updated in real time, show the three most significant operating indicators for the photovoltaic system.

The first indicator (“Current solar power output”) expresses the active electrical power (in kW) produced by the panels at the time of display. The vertical location of the solar panels on the south facade of the building maximizes the active electrical power around midday on winter days with clear skies, when the sun is low on the horizon and the rays are almost perpendicular to the panels. On the contrary, production around midday in the summer months is reduced, due to the high angle of incidence of sunlight on the panel and the partial shading caused by the sun visors placed above the windows for thermal efficiency.

The second indicator (“Total solar energy produced”) is the total electricity produced (expressed in MWh) starting from the installation of the monitoring system (Spring 2021). Although the active electrical power may appear modest due to the limited size of the current plant, the overall production of solar power entirely consumed in Building 20 is not negligible, with the consequent economic benefits including savings on the electricity bill.

The third indicator (“Total CO2 saved”) represents an estimate of the total CO2 emissions avoided since the installation of the monitoring system (March 2022). How can this indicator be estimated? Each kWh produced by the panels and self-consumed locally leads to a corresponding reduction in the energy that must be purchased from the network. As the electricity market currently works, self-produced energy replaces that which would have been generated by the plants that would sell it at the highest cost, that is, the combined cycle plants powered by natural gas. The average value of CO2 emissions for these plants is around 350 g/kWh, a value which was then used to estimate the reduction of emissions corresponding to the total energy production of the plant.