| Abstract |
In the light of the imperative need to save fossil fuels, renewable energies must be increased, and, in the meantime, the efficiency in energy use has become a priority and an urgent goal. In Italy, a considerable part of energy?s consumption is due to houses?s heating and methane is by far the most used fuel. Therefore, the utilization of low temperature renewable sources should be recommended for these purposes, and, in particular, the use of geothermal resources that are widely available in Italy. This paper will analyze the natural gas saving?s amount for the nation-scale system in case of traditional gas-fired heating?s replacement with geothermal district heating. The measure of this saving is given by the parameter ?R? called ?energetic saving index?. Geothermal fluids are not homogeneously spread over the country and their characteristics may be quite different (hot water or steam), consequently, various cases are here considered according to the different available fluid types. In this view, four different cases of utilization of thermal fluids for space heating are considered; two of them regard high enthalpy fluids available only in geological areas with very high geothermal anomaly, while the other two cases are about fluids from moderate to low energy content that can be found in large areas of the Italian territory, where low geothermal anomalies occur. Obviously energy efficiency changes with the design parameters, and to compare the efficiency in different configurations is therefore proposed a standard criterion called index ?R?. To complete the analysis we must take into account the energy required to make the components and to build the plant. In this way, the pay back period, in terms of energy, can be estimated. This is particularly useful to compare different technical solutions. To conclude, also while working with renewable energy sources; plants? design and operation must always search for solutions with higher efficiency. |