The innovative domestic heating system in Madonna di Campiglio, which exploits the bowels of the Earth

The innovative domestic heating system in Madonna di Campiglio, which exploits the bowels of the Earth.

The energetic problem is common to both great industry and the medium or small user, such as private citizens and craftsmen.
The present European and national sceneries present at least two main streams of consumption: thermical by combustion, and electricity that still depends on fossil fuel such as oil, natural gas or coal.The D.L.16 March 1999 n.79(Bersani Law), that has liberalized the electricity market has also established in Italy the so-called energetic market. According to it, it is now possible, for eligible users, to buy and sell electricity in the so-called "Power Exchange", where competition rules apply. Eligible users are, dating back to the year 2004, all those people who possess VAT number, that means, every client other than domestic users. These latter represent the bound customers, who cannot enter into a contract of supply with any distributor, but are obliged to stock up on those who exert the service in their own territory.
The market guarantor for those users is the so called single buyer (AU) who ensures the continuous availbility and supply of energy and fair prices. The AU signs buy and sell contracts on the market. From January 2007 every final client will become eligible, including domestic users.
Alternative sources of energy (aeolian, solar, geothermal, tidal, hydraulic, from biomasses and biogases etc.) have become more and more appealing. Among the measures for promoting their use, we find the Green Certificates, introduced back in 1999 and granted by the GRTN. They certify that a certain amount of energy (measured in kilowatt-hour - kwh) put on the market by a producer, comes from renewable sources. Those certificates, whose size is 50.000 Kwh, are in every respect, real shares listed on the energy market. The incentive lays in the fact that it is compulsory - both for producers and importers - to introduce on the market a share of energy produced after renewable sources equal to 2% of the total amount of energy produced during the previous year.
From 2004 to 2006 the compulsory share has increased yearly of 0,35 points per cent.
Whoever produces (or imports) electric energy produced from non-renewable sources can make up with it purchasing Green Certificates that belong to other subjects' exceeding production.
Italy is aiming at reaching 25% of electricity consumptions from renewable sources within 2010. The process of decentralization of energetic policies has given much authority to Regions and Autonomous Provinces: localization of district heating plants, energetic certification of buildings, restraints in heating-gas emissions and so on. Trentino is, in the national panorama, at the very first places as far as reguards the production of energy from alternative sources; almost all of it comes from hydroelectric power plants.
Zooming onto domestic users, in the Province of Trento, a case of optimization of natural resources with peculiar attention towards environmental issues has to be highlighted: the Hotel Garni del Sogno in Madonna di Campiglio. Since it is necessary to heat up buildings for most of the year, due to the local climate, the impact of the use of non-fuel sources is itself a great bonus, also in this case, where the production has to do with heat and not with energy.
The heating plant, realized by the engineer Schiavon and that represents the first example in its genre in the province of Trento, is linked to a careful thermic isolation of the building and uses geothermal power stored underground in the form of heat. It is a very simple concept, and it does not need any peculiar environmental condition.
Underground, and in particular in the groundwater, heat is stored coming from solar radiation and, what is more important, is that this tank, at certain depths, keeps a temperature that is constant all year around.
It is all about transfering that heat, properly amplified, offered for free by nature, to the inside of the building, through a heat pump. What is a heat pump anyway?

Each one of us is familiar with a fridge: it withdraws heat from a cold environment (called the "cold source"), that is its inner part, in order to hand over heat to a warmer environment ("hot source"), i.e. the more external one. Underground temperature is lower than the external one, while the temperature inside of the building is higher.
Since the transfer of the heat from a cold area to a warmer one cannot take place spontaneously, an external help is needed, and it is represented by electric energy that makes a proper engine (compressor), conceived for the purpose, work.
The heat pump works exactly like a fridge, the only difference is its final purpose: no more withdrawing heat from a cold environment to make it cooler and cooler, but giving heat to a warm environment (sanitary water and domestic heating for example). The "cold" source is the underground, with groundwater temperature at around 10°C constant; since it flows, the area is subject to a continuous exchange of water with the same incoming temperature (thermic capacity potentially unlimited), while the hot source is the water that circulates in the heating plant.
The bigger output and, thus the bigger convenience, is reached when the spring temperatures (T1 and T2) are close.
The installation plant is expensive as an initial investment, compared to a classical plant (a pump of 25 Kw costs around 20.000 euros), but it should pay off in 7-8 years, following the trend of the increasing price of fuel, that should make the consumption of electricity more convenient than the direct use of fuel (combustible). The optimum heating system for this kind of plant is floor heating that needs just a temperature of 37-38°C and that lays therefore in the range of the highest output of the pump, while the traditional one, i.e. panel heating system, needs a temperature of 60-80°C. Moreover, in the last years the output of the pump has gone from 1:2 (from 2 to 4 degrees), to around 1:4.
During the summer, pumps may also be used the other way around, so that they give heat to the underground and cool down the environment.
Since it is a thermodynamic type of heating, lacking totally of fuel combustions, we avoid heat and polluting emissions in the atmosphere, and also the installations of tanks, a possible cause of leaks in the ground. There is, of course, consumption of electric energy, but on a local level, the environmental impact is equal to zero.

A quantity of heat Q2 is extracted from the subsoil at temperature T2. Electrical energy, represented by L, is used to transfer it to the area to be heated at temperature T1, in the form of Q1, which also encompasses the heat into which L is transformed and is therefore greater than Q2.

In the case in question, 14 shafts were dug, reaching a depth of 105 m. The shafts were fitted with pipes leading to a collector connected to the heat pump. Water mixed with antifreeze (glycol) circulates in the pipes. The temperature remains constant at 105 m below ground, at 7-10°C, even in the winter. Upon reaching the subsoil, the water temperature reaches around 10°C. It then rises and transfers heat, via a heat exchanger, to the pump refrigerant, which evaporates into the evaporator. The refrigerant is then compressed by an electric motor. It heats up and is sent to the condenser, where it transfers its heat to the heating system water or hot water by condensing. It then expands and cools down in the throttle valve, partially evaporating. The hot water (4000 litres) and heating system water (4000 litres) is heated by two pumps that absorb 25 KW and 17 KW upon start-up.