Page 281 - ISES SWC50

9.14 ISES Institute Members: Politechnico Di Torino

20+ YEARS OF RESEARCH ON THE SUN AT DEPT. OF
ENERGY-POLITECNICO DI TORINO

The experimental research regarding solar energy at Politecnico di Torino has a long history, more than 20 years in
two different Departments, in the past, Department of Electrical Engineering and Department of Energetics, and
now after merging of them (2012) in the Department of Energy (Director: Prof. M. Perino).
For what concerns the solar photovoltaic (PV) technology supervised by Prof. F. Spertino, who collected the
heritage of Prof. A. Abete, pioneer in the research on PV generators and systems, a pilot plant was installed in 2000
on a rooftop of the former Department of Energetics. The Italian Agency for the Energy and Environment (ENEA)
managed the investment. This PV plant started its operation after that in 1999 a new Italian regulation made
possible, for a commercial or residential user, to exchange power with the national electric grid; in particular, this
regulation fixed an adequate price for the electricity injected into the grid, while in the past no monetary amount
was paid. This pilot PV plant, equipped with 18 PV modules in monocrystalline silicon with 13% of conversion
efficiency (at that time a remarkable value) is still operating after 21 years and is connected to the single-phase grid
(230 V/50 Hz). The performance was monitored in the first years to check the correct operation of the PV array with
rated power of 1.5 kW and of the centralized inverter in terms of conversion efficiency and quality of the current
and voltage AC waveforms.

The second PV plant was installed in 2003 in the former Department of Electrical Engineering on a terrace with
surrounding buildings that create shading problems. For that reason, the configuration of the DC-AC conversion
was the Module Integrated Converter (MIC) or AC module, in which each of ten PV modules in monocrystalline
silicon supplies a MPPT-integrated inverter able to create a stable grid connection with anti-islanding protection.
The power electronics is characterized by high-frequency commutation under resonance with low weight and is
inserted into a rugged and sealed enclosure. The PV plant with rated power of 1.1 kW is still operating and each AC
module has different duration of operation according to the daily evolution of the shading pattern.
The third PV plant was installed in 2010 and it is the first building integrated PV system on the rooftop of the
Politecnico’s startup company incubator (I3P): the special PV modules have double glaze with high thermal
insulation for winter season and are equipped with highly-efficient monocrystalline silicon (efficiency of 19%
with rated power of about 30 kW); they supply two inverters with three-phase grid connection (400 V/50
Hz). The orientation of the skylight in the two-pitch roof is east-west and so the first PV generator produces
the majority of energy in the morning, while the other one has the opposite behavior, producing mainly in
the afternoon.

In the last five years up to now, other three PV systems with global rated power near 900 kW have been
installed on the roof of different Politecnico’s buildings (Departments and classrooms) and connected to the
three phase grid with ability to exchange power in the framework of the so-called Italian “Scambio sul Posto”
(translated in English as “onsite power exchange”). The energy production from the PV systems is able to
meet about 10% of the total university consumption. The most important one, with rated power of 600 kW,
is placed on the saw-tooth (shed) rooftop of a former factory, now, after renovation, block of classrooms
of Politecnico. In general, the vision of Politecnico is to gradually shift towards the concept of nearly Zero
Energy Buildings (n-ZEB) for its real estate assets by using the photovoltaic generation to produce the
needed electricity.

Developing sustainable technologies is essential and highly desirable for mitigating the anthropogenic
impact on environment. In this context, the research of Prof.s P. Asinari and E. Chiavazzo, with their group,
investigates the use of solar energy to address and mitigate the problem of the water scarcity, especially in far-
away regions without access to the electricity grid as Sub-Saharan Africa, Central Asia, Southern Asia, Eastern
Asia and South-Eastern Asia. Recently, they have developed low-cost and low-carbon renewable energy
(thermal solar) driven desalination technology to reduce the carbon footprint in drinkable water production.
To this purpose, they have focused our attention on: i) optimizing the solar light harvesting process to
enhance the solar to vapour generation efficiency and ii) improving the use of the harvested energy flux
through an efficient condensation passive process with multiple re-uses of the heat of condensation (a lab-
scale prototype is reported on the left-hand side of the figure below). Thus, they have designed and realized a
standalone compact desalination unit based on a multi-effect distillation process able to produce fresh water.

ISES SWC50 - The Century of Solar-Stories and Visions | 263