Energy: ENEA and Italian Industry alliance for new solar thermodynamic plants

The future of solar thermodynamic energy in Italy starts in Sicily, where it was born, -according to legend- with Archimedes’ burning mirrors. Thanks to an alliance between ENEA and the Italian industrial world, in fact, the first plant in Italy to combine solar concentrated power and photovoltaics will soon be inaugurated in Partanna (Trapani), and another is about to be built in Trapani in the  Piana of Misiliscemi. ENEA will provide technical support to both projects, the Italian companies SOL.IN.PAR. srl and Stromboli Solar srl are the commissioning companies  and FATA spa (Danieli Group) the builder.

“These two projects are proof that the italian industry is investing in solar thermodynamic technology, implementing concrete initiatives despite bureaucratic and regulatory constraints”, Giorgio Graditi, Head of the ENEA Energy Technologies and Renewable Sources Department pointed out. "ENEA has been involved in these two plants to carry out several activities, ranging from design, construction and start-up supervision to performance assessment, up to the integration of the concentrated solar plant with photovoltaic technology", Graditi said.

The Partanna plant has an installed capacity of 4.26 MWe and can generate electricity for over 1,400 families (about 30% of the population of the municipal area, with 3 kW domestic users). "We expect to reach a thermal energy storage capacity of 180MWht, equivalent to approximately 15 hours of operation of the system at full load, even in the absence of solar radiation," Graditi explained.

The integration of thermal energy storage systems is an important aspect, since it allows to obtain thermal energy that can be converted into electricity and therefore program production to meet energy demand. In this way it is possible to decouple solar energy collection - which depends on the day/night cycle and the weather conditions - from electricity production, linked instead to consumer energy demand.

The total area of the solar field in Partanna is 83,000 m2 (about 10 soccer fields), where 126 linear Fresnel-type solar collectors are installed, arranged in 9 loops [1], capable of focusing the sun's rays on a tube receiver; a low-cost, non-flammable, environment-friendly mixture of molten salts (mostly potassium and sodium nitrates) flows inside (in case of circuit leaks, easy to remove because they solidify quickly), which is used both as a heat transfer fluid and as a means of accumulating thermal energy at a stable temperature of about 550 ° C.

The fluid heated in the solar receiver accumulates in the hot tank [2] then enters the steam generator, where it releases its energy and discharges into the cold tank; from there it returns to the solar receiver. The steam generated is sent to a generation group, steam turbine / alternator, with a power of 4.26 MWe.

The plant is equipped with a start boiler fueled with LNG - about 47 t stored in a cryogenic tank - to ensure the temperature of the molten salts is maintained above freezing point, especially in winter and at the beginning of the filling phase.

In addition to the two plants in Sicily, Italy is conducting other initiatives in the field of thermodynamic solar: in 2019 this technology was included in the strategic themes of the Electric System Research, the three-year research program on new energy technologies funded by the Ministry of Economic Development. In this context, ENEA has presented a three-year research plan on the main components of solar concentrating plants, which includes the study of new heat transfer fluids, the development of innovative surface coating materials for receiver tubes and the construction of advanced thermal storage systems.

Furthermore, by 2021 an experimental platform for the characterization of components for the supply of industrial heat at medium and high temperatures will be built at the ENEA Casaccia Research Center (Rome). "The process heat market could prove an effective tool for promoting thermodynamic solar energy: in this sector the competition with other renewable energy technologies is less fierce and the applications which would trigger the virtuous circle of the economy of scale increase significantly, also in the short-medium term ”, Giorgio Graditi pointed out.

The medium / high temperature heat produced by a  solar concentrating plant could be used, for instance, to power some pharmaceutical, food and textile industries processes, as well as produce 'green' fuels and hydrogen from biomass and water (electrolysis ). "Industrial energy consumption accounts for approximately 32% of global energy demand and, of this share, only 26% can be attributed to electricity consumption and the remaining 74% to thermal energy consumption, which could be satisfied by concentrating solar plants integrated into the industrial process ”, Graditi concluded.

Over the next decades the International Energy Agency expects a significant increase in the share of solar thermodynamic energy, which should cover more than 10% of the global primary energy requirement by 2050. Aiming at improving the thermal energy storage capacity of the systems will be crucial to attract further investment.

Whereas in Italy large-scale plants (over 20-50 MW) are difficult to build due to specific geographical conditions and authorization restrictions, the Countries where this technology has found greater application worldwide are Spain and the United States, which lead the ranking with the highest installed and operating power, 2.3 GW and 1.8 GW respectively, followed by China, Morocco and South Africa. A further boost to the development of this technology comes from the United Arab Emirates and India, leading the way with new plants under construction of 700 MW and 290 MW respectively.

For more information please contact:

Giorgio Graditi, ENEA, Department of Energy Technologies and Renewable Sources, giorgio.graditi@enea.it