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Gas combined-cycles

Natural gas was present in the production of electricity in Italy since the '60s, albeit marginal; it then had two moments of strong development: in the early '80s as a result of increased environmental awareness and a second time in the late '90s to the strong technological development of combined cycles. Until the '70s gas was used in open cycle gas turbines, essentially to cover the 'peak loads', it then began to be a primary fuel to be used in production for the 'base load'. The use of a natural gas boiler, although not very efficient, dates back to the early '80s (often after requests accepted by the Local Authority) and at the end of the '80s, the introduction in the Italian system of gas turbines for the re-development of conventional steam plants, replacing the traditional boiler with one or two gas turbines. The re-developments of Enel Plants in Montalto di Castro, Turbigo Levante, Rossano Calabro, etc. are the best known examples; performance, albeit higher than that of the combustion in the boiler was still relatively low (just over 40%).

The technological development of the '90s led to the diffusion of new combined cycle plants even in Italy; the first significant achievement was the Enel Leri Cavour Plant in Trino Vercellese with yields close to 50%. Subsequently, the combined cycle spread widely throughout Italy with other projects such as those of the Enel Plants in La Spezia, La Casella, etc. with yields much higher than 50%. Starting in 2000, natural gas overtook oil and has become the main source for the production of electricity in Italy. With 152.7 TWh of electricity in 2010 (44.5% of national production), natural gas was the main source for electricity in Italy. In the global scenario of energy sources, fossil fuels have always had an important role, 71% of the electricity produced today comes from coal, oil and natural gas. Even the projections made in the United States between now and 2020 indicate a continuation of the upward trend in the fraction produced from natural gas and it is expected to reach 33% worldwide in 2020. The projections of studies by the University of Chalmers up to 2020 show that the predominant part of the most recent plants (0-10 years) is gas and that the investments planned are in the overwhelming majority of cases of the same type.

This upward trend derives from the fact that natural gas is the cleanest by nature among fossil fuels. Furthermore, the recent impressive technological development of natural gas combined cycle has made these plants the most sought after worldwide for the production of electricity, due to their high efficiency, low emission levels and installation costs. Unfortunately, with respect to the advantages mentioned above, the main aspect against the use of gas as a fuel is its high price, which is linked to the oil market and continues to grow in international markets, in a way that now seems more structural than short-term. Since in electricity generation with natural gas, the cost of fuel accounts for about 80% of total production costs of kWh, it is easy to understand that it represents the true 'Achilles heel' of this source. In addition to this aspect, there are also typically national elements, such as taxes and the constraints imposed by the pipeline owners.

In this situation, because gas fuel has high costs regardless of the advantages mentioned, it is necessary to use it wisely. This need is the reason for which RSE dedicate part of its research studies to increase the efficiency, reliability and flexibility of combined cycles with the following goals:

 • Check the feasibility of a flexible operation of first-generation combined cycle plants, in relation to the progressive switching from basic plants to plants required to operate according to criteria of merit order, identifying potential problems and their solutions;
 • Experimentally characterize the behavior of the critical components of gas turbine equipment and assess the actual prospects for introduction in the national park generation, increasing the overall efficiency without reducing the reliability and security of the service;
 • Develop new methodologies and reliable and effective instrumentation systems for the evaluation of the degradation of critical components of the gas turbine;
 • Ascertain the performance of alternative processes for reducing NOx emissions, with the aim of reducing values to 1 ppm; • Quantitatively assess the release of other gaseous pollutants (particulate matter, formaldehyde, etc.) in natural gas combustion products.