Visiting Larderello Geothermal Power Plant
November 2024
Philip Ball.
Geothermal Energy Advisors recently visited the geothermal museum at Larderello
(Photo 1). Larderello, is the birthplace of geothermal derived electric power, which was
first demonstrated on July 4th, 1904. Larderello is located in La Valle del Diavolo – “The
Devil’s Valley”. Once called because of the spectacular lagoni, fumerole “lagoons and
fumaroles” coupled with the smell of Sulphur. The town of Montecerboli is located at
the head of Devil’s valley. The town gets its name from Montis Cerberi, a gabbro outcrop
known as the “mountain of Cerberus” the legendary three headed dog (Photo 2) that
guards the gates of the underworld (Stiles, 2024; Barbier et al. 1983). Today, the lagoons
and fumeroles in the valley which made the valley dangerous and uninhabitable, have
gone. 111 years of geothermal production have extinguished these, although they can
be found elsewhere in the region.
Photo 1: The Larderello Geothermal Museum.
Photo 2: Tomb of Cerberus in Giugliano, Italy (Altuntas, 2024)
Geothermal energy had been known about and used in the region for centuries and is
referred to in Etruscan/Roman literature (Burgassi, 2012). From as early as the 3rd
century geothermal phenomena and religion share a close history (Burgassi et al.,
1999). Lagoons were used as spar centers and were often cited as centers for healing.
Dante Alighieri (1265-1321) is reported to have once written about Larderello describing
“boiling water spills from its veins, while all around the steam constrained in the abyss
of the earth’s bowls thrusts forth… Song XIV of Le Rime (the Rhymes)” (Bianchi, 2015;
ENEL, 2024a). It was Piero Ginori Conti (Photo 3) who proved that steam could be used
to create electricity in 1904, July 4th. Following this, Power station No.1 was completed
in 1913 and was the first electric producing geothermal power plant in the world,
producing 250 kW. Prior to the use of power, the regions lagoons and baths were known
for their healing properties and Born production, which was founded by Francesco De
Larderel in 1827.
Photo 3: The bust of Piero Ginori Conti
The region is stunningly beautiful. This is remote Italy with old towns topping the
hilltops, and rolling hills covered in trees. Occasionally you spot the post-WWII
geothermal development the concrete cooling towers, somehow beautiful and calmly
cooling the hot water topped by gentle white clouds (Photo 4). At night the cooling
towers are beautifully lit up in red, white and green (Photo 5).
Photos 4: Regional view of cooling towers, Larderello district
Photo 5: Nuovocastello power plant at night.
The museum at Larderello and the region is well worth visiting. It is about a 2-hour drive
from Florence airport. The museum itself is small and informative and free to enter. At
the museum I met Andrea Farru, this was a great highlight for me, since Andrea is
extremely knowledgeable about Larderello. Andrea took me on a tour of the region to
see Pozo #120. An old well drilled 740 meters deep which is not used for power
production today, but maintained for demonstration purposes. The sound of the hot
pressured water thrusting forth once the valve was opened was incredible (Photo 6).
Photo 6: Pozo 120. Demonstration of geothermal waters
Following the well demonstration, Andrea took me to see the cooling towers at power
plant No. 3, originally developed after World War II (Photo 7). By 1950 The Larderello No.
3 power station had started production with four 25,000-kW and two 9000-kW units for
the auxiliaries. These were the first direct condensing cycle power plants (Parri et al.,
2016). Afterwards we visited the more modern turbine building and vertical cooling
systems (Photo 8) which produce 120 MWe (2x60 MWe) from a double-flow condensing
steam turbine (ENEL, 2024b)
Photo 7: Cooling towers of Power Plant #3, developed after World War II. Originally
there were 4 towers, only three remain today. One tower was redeveloped as an
amphitheater.
Photo 8: Modern hybrid (wet/dry) type forced draft cooling towers from Valle Secolo
geothermal electric power station, Valley Century 1 and Valley Century 2 (ENEL, 2024b).
Larderello is a natural hydrothermal system. Today power is generated from a collection
of 34 active power plants, which has the combined capacity to produce 769 MW
electricity. Larderello is the second largest geothermal power plant in the world, second
to the Geysers complex in the USA (ClimateCare, 2024). The geothermal power plant is
a Vapor-dominated geothermal system, which produces a significant amount of dry
steam which is used to drive the turbine. At the time or writing, ENEL are the current
custodians of the Larderello geothermal power plant.
Larderello, Italy is according to the global tectonic maps of Hasterok et al., (2022)
located within a Volcanic arc geodynamic setting, or more precisely the Campanian Arc
for its tectonic/physiographic setting (Ball et al., 2025). It is important to note, there are
no volcanos at the surface here in Larderello, as is commonly thought within Volcanic
arcs. There is however a 4-9 km buried granite intrusion that originated between 2.5-3.5
Ma (Gianelli et al., 1997; Manzella et al., 1998, Cavarretta and Puxeddu, 1999). The
granites are intruded into Mio-Pliocene (autochthonous) and Eocene to Paleozoic
(allochthonous) sediments and basement. Figure 1 indicates that the crust at the
location of Larderello has undergone a collisional and post-collisional evolution
(extension), and may be located at the flank of the modern-day back arc basin
responsible for the formation of the Tyrrhenian sea to the west. The extensional
processes resulted in rapid crustal thinning, a shallow Moho (~22 km) and a rapid rising
of the asthenosphere (Calcagnile and Panza, 1981). This was associated with a
prolonged magmatic activity that in southern Tuscany produced intense hydrothermal
circulation documented by both fossil (ore deposits) and active (geothermal fields)
systems (Ball, 2022).
Figure 1: Geological interpretation of deep seismic reflection lines suggest extension
dominated since early middle Miocene, linked to back arc basin formation (Brogi et al.,
2005)
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