Geothermal Space and Agribusiness Heating in Italty
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GEOTHERMAL SPACE AND AGRIBUSINESS HEATING IN ITALTY Roberto Carella 1 and Claudio Sommaruga 2 1 Unione Geotermica Italiana, 58 Via Caracciolo, I-20155 Milano, Italy 2Geothermal consultant, 62 Via Sismondi, I-20133 Milano, Italy Ground water is abundant in many Italian regions and, Key Words: geothermal heat uses, Italy. especially when tepid, is used for fish farming (Tuscany, Apulia). ABSTRACT Geothermal heat pump (GHP) uses of this resource are not Non-electric uses of geothermal energy in Italy are mainly common in Italy, contrary to Central and Northern Europe associated with the spa business, but a large share is also examples. related to agricultural utilisation (greenhouses and fish farming) followed by space heating, including district heating 3. GEOTHERMAL HEAT USE IN SPACE HEATING (DH). The main existing applications in space heating are in the Abano area, Ferrara and Vicenza (in Northern Italy) and Even though medium-low temperature water is available in Larderello area (Tuscany). The most important agribusiness large quantities at reasonable depth in Northern Italy and facilities include greenhouses at Amiata and Pantani (in Tuscany, few towns are geothermally heated. central Italy) as well as the fish farms of Orbetello (Tuscany) and of Brindisi and Sannicandro (Apulia). Geothermal space heating in Italy, including use in hotel facilities in the Abano area amounts to the equivalent of Concerning the near future, there is interest in geothermal 40,000 TOE/year. Energy from currently operating district heating in Grado (on the North Adriatic coast) and in geothermal DH systems (12,000 TOE/y out of the 15,000 some Tuscany towns, and in greenhouse heating at available) represents 2.3% of energy from all existing DH Castelgiorgio (Umbria) near the Alfina geothermal field. In plants (AIRU, 1998 mod.). The main geothermal space the longer term, moves to achieve the Kyoto environmental heating plants are briefly described hereunder. targets should favour the expansion of geothermal heat use in Italy. 3.1 Abano area (Veneto). 1. INTRODUCTION The largest direct use of geothermal heat occurs in the Abano area and consists in the individual heating of a large number Non-electric uses of geothermal energy worldwide, with an of spa hotels and of a spa centre. It represents one of the most installed capacity of 9,963 MWt, amounted to 36,910 GWh/y important examples of integrated use of geothermal energy in 1997 (FRIDLEIFSSON, 1998), corresponding to a for health purposes, space and recreational heating in Europe substitution of almost 2.9 million tons of oil equivalent per (DAINESE, 1992, CARELLA, 1992). year (TOE/y). According to LUND (1996), space heating applications are prevailing (33%), followed by agribusiness The Abano area extends for some twenty km2 at the eastern including aquaculture (25%), balneology (19%), heat pumps edge of the Berici-Euganei volcanic ridge in Veneto (NE (12%) and industry (10%). Italy). Several resort towns are located in this sector, famous for its numerous hot springs, with many hotels dedicated to The situation varies greatly from country by country. In Italy, the health and relaxation business. Abano is the most where direct uses amount to about 240,000 TOE/y, important spa town with about 80 hotels, almost all of which agricultural applications (60,000 TOE/y) represent 25% of the produce their own geothermal water. In all, including other total, after balneological-spa uses (52%) but ahead of neighbouring resort towns, some 120 hotels are fitted with residential heating (17% of which 10% is associated with spa their own geothermal facilities. Approximately 230 wells at hotels in the Abano area) (SOMMARUGA and VERDIANI, an average depth of 400 m are currently producing, by 1995; DICKSON and FANELLI, 1996; CARELLA and pumping, 3,600 m3/h of water from fractured Upper Mesozoic SOMMARUGA, 1999). limestone. Temperature ranges from 65°C to 87°C and salinity between 2.5 and 6 g/l. The main tourist season is in 2. ITALIAN GEOTHERMAL RESOURCES. spring and autumn. Average water production throughout the year is about 2,500 m3/h. Most hotels have two producing Italy is one of the most important countries in the world with wells and are connected with spa facilities. The utilisation regard to the availability of geothermal resources. A long belt scheme is quite simple and includes a set of heat exchangers on the West side of the peninsula, from Tuscany to Campania, which pass the geothermal heat to a separate fresh water near Naples, is the seat of very high temperatures often circuit for space heating and sanitary water needs. Hot and exceeding 200°C at shallow to medium depth, associated with cold water storage tanks are common but a back-up fuel boiler magmatic events. In the Northern half of this area several is seldom provided, and emergency needs are taken care of by geothermal fields (generally in Mesozoic limestone withdrawing heat from nearby wells. A large proportion of reservoirs) are exploited for electricity generation with the geothermal fluid is used directly, after filtering, for health subordinate heating uses, often in the agricultural sector. The treatments and to supply the swimming pools. The exhausted Po Valley, in Northern Italy, is underlain by a quaternary to thermal water, with a temperature of about 40-45°C, is Mesozoic sedimentary section with several aquifers at varying discharged at surface. The total heated space is about 2.5 depth with moderate temperature, but occasionally (Abano, million m3, in addition to 200 swimming pools. Substituted near Venice; Ferrara, north of Bologna) reaching relatively energy is estimated to be 25,000 TOE/y for space heating and high values (70-100°C) at no great depth. A certain number 90,000 TOE/y for therapeutic and recreational uses. of geothermal projects, mainly for residential heating and spas, 3.2 Ferrara (Emilia-Romagna) but also for agricultural uses, are in operation. The Ferrara geothermal field, in NE Italy, was discovered following oil and gas exploration carried out by AGIP. In 117 Carella and Sommaruga 1956 the well Casaglia 1, drilled to the depth of 3,379 m on a parties, A.I.M. developed the whole district system starting in large structural high without finding hydrocarbons, intersected 1988 and geothermal heating began in the second half of a 100°C aquifer starting at about 1,100 m depth in fractured 1990. Mesozoic carbonates. Casaglia 1 was re-entered in the late seventies and tested in 1981 under a joint-venture with ENEL, The heat plant (LEONI, 1995) consists of a stainless steel the Italian national utility, with AGIP acting as operator. As plate heat exchanger; three heat pumps (for a total of 7 exploitation of the resource required reinjection of the spent Gcal/h) with connected cooling towers; three peak and back- fluid, a new well (Casaglia 2, about 1 km from Casaglia 1 up gas fuelled boilers (for a total of 15 Gcal/h) and one and 1,960 m deep) was completed in 1981. This well has a geothermal water storage tank (capacity 200 m3). The district high productivity (up to 400 m3/h when pumped) of 100°C heating network includes a 7 km one-way domestic hot water water with salinity of 65 g/l. line supplying directly about 20 m3/h sanitary hot water to the end-users. Space heating is provided by a parallel 7.4 km After signing a preliminary heat sale contract with the Ferrara double line in pre-insulated steel pipe. Inlet network municipality in 1983, the project developed slowly on the temperature is 90°C and outlet 60°C. Air conditioning is downstream side until 1990 when the first geothermal heat through cold water (inlet 6°C, outlet 12°C) in the same line. delivery took place. The initial mining facilities consisted of After heat extraction, the geothermal water is discharged in Casaglia 2 well used as producer (at rate of 200 m3/h when the town drainworks at 20-25°C. The system services 74 main pumped) and Casaglia 1 acting as reinjector. In 1995, a users, heating a volume at 1.33 million m3. Energy substituted second producer (Casaglia 3) was drilled, parallel to and a is around 2,700 TOE/y and savings amount to 3,300 TOE/y. few metres from Casaglia 2, to a depth of 2,000m, doubling Use of geo-heat has been suspended in recent years, due to a the flow-rate from the field. dispute over the geothermal water price. The surface equipment operates in closed circuit at 18 bar. 3.4 Acqui Terme (Piedmont) Anticorrosion additives are injected in the producing wells. At the production site a filtering unit, followed by a set of three Another geothermal plant using heat pumps is that of Acqui titanium plate heat exchangers pass the available heat to a Terme, in NW Italy (PREZIUSO, 1989). Acqui is a spa town fresh water circuit feeding the district heating system, owned with a single hot spring (La Bollente) with a temperature of by the Ferrara Municipality and operated by its company 70°C and a free-flow of 33 m3/h. The geothermal plant owned AMGA. A pre-insulated steel double feeder line, 2 km long, by Acqui Terme municipality was designed to use the spring carries the hot fresh water to the heat plant and conveys back water when spa facilities are closed (spring, autumn and part the cooled fluid to the AGIP-ENEL heat exchangers. The heat of winter). The heat station consists of a plate heat exchanger; plant is composed of: the feeder terminal; two hot water and two gas fed heat pumps and two back-up gas boilers (total two cold water storage tanks, each of 1,000 m3 volume; and capacity 3.6 Gcal/h).