Perspectives of off-shore

geothermal energy in Italy

Fabrizio Armani, Università degli Studi di Milano

Varenna, EPS – SIF International School on Energy 2012

The earth temperature gradient

• Average gradient :

140 °C @ 4 Km depth

Economically unsustainable

Anomaly areas needed

Geothermal field key elements

( Hydrothermal high enthalpy)

• Caprock

• Reservoir

• Hot body

Heat anomaly + water availability

starting point for geothermal exploitation

Example of geothermal power

plant

Geothermal electricity in Italy

• Installed Power : 737 MW (all in Tuscany)

• Produced energy: 5,4 TWh /y

• 1.7% of total electrical production ( 315 TWh/y)

• 7.7 % of renewable electrical production

• 3rd in world ranking of geo-thermoelectric producers

• 1st geo-thermoelectric producer in Europe

Source: GSE (2009)

Average earth heat

flow : 65 mW/m2

Tuscany: on-shore

geothermal exploitation

South Tyrrhenian

Back-arc basin

Heat-flow

anomaly from

250 mW/m2

South Tyrrhenian seamounts map – Marsili map

Is there a reservoir ? Density anomaly from

gravimetric measures (less density)

Rock density

2.67 g/cm3

Other hints of huge amount of

water inside the volcanic

structure

• Excess of hydrothermal-derived dissolved gases (CO2,CO,

CH4),as well as 3He / 4He with respect to the background

(Lupton et al. 2011 – J.G.R. )

• Hyaloclastite rocks (porous, formed by fast cooling after

eruption in sea)

• Geyser observed along the volcano wall.

Project features

• Huge amount of seawater filling fractured rocks

• Drilling site: volcano crest, 500 - 800 m below sea level

• Well depth: 1.5 – 2 Km (in order to intercept resevoir)

(such drilling tecnology already exists )

• 150 °C/ Km average temperature gradient expected

• Maximum water temperature of reservoir expected up to 400-500 °C

Electric power generation

• Power generation components hosted in oil-like off-shore platforms

• 200 MWe each platform (pilot project)

• 800 MWe planned for Marsili site (4 platforms)

• 1.3 and 5.2 TWh/y electricity production respectively (conservative estimations)

• High initial cost 700 M€ and 2 G€ respectively

• Expected cost of electricity in market range

( 80 – 140 €/MWh) without considering subsidies

policies

Conclusions

• Promising renewable technology

• Exploitation of all South Tyrrhenian seamounts is expected to cover up to 10% of Italian electric consumption (about 30 TWh/y)

• Several off-shore site all around world (Japan, Mexico, Caribbean, Indonesia)

• High number of working hours equivalent ( > 6500 h/y). Power stability.

• Quality of geothermal fluids must be evaluated after first drilling. No heavy metals nor pollutants have been yet observed

References

• Technical pictures and project overview,

courtesy of D. Paltrinieri (Eurobuilding)

Geopower Europe Conference

Milan, 6-7 december 2011

• http://www.eurobuilding.it/marsiliproject/

• P. Signanini et al. , I distretti vulcanici sottomarini del Tirreno: una

possibile risorsa geotermica?

Giornale di Geologia Applicata, 4(0153):195200, april 2006

• Lupton et. al. , Active hydrothermal discharge on the

submarine Aeolian Arch.

Journal of Geophysical Research, 116(B02102), february 2011.

Thank you for your kind attention !