The drive for achieving high values of fuel utilization factor, in the last years, has led to an increasing attention to combined heat and power (CHP) plants.In this scenario, the district heating allows to achieve high conversion efficiencies by centralizing in few large power plants the need of thermal energy in household sector. The power plants that feed the District Heating Networks (DHN) usually work by combined heat and power set-up.District Heating Networks have found a large development in the last decades. The main advantage of DHNs is the reduction of pollutant and thermal emissions in the city area. Further, the large use of DHNs increases the safety, due to the absence of combustion systems at the final users of thermal energy. For the same reason also the transportation of fuel in the city area can be drastically reduced by the use of DHNs.On the basis of the previous observations, in this study a new software for the DHNs design and analysis is described and validated. This software, which has been developed by University of Bologna, is based on the Todini-Pilati algorithm generalized by the use of Darcy-Weisbach equation.More in details, in this paper the main physical-mathematical models adopted in the realized software, called Ca.R.Di.F., and its validation are described

Gas turbine power plants are widely employed with constrained efficiency in the industrial field, where they often work under variable load conditions caused by variations in demand, leading to fluctuating exhaust gas temperatures. Suitable energy harvesting solutions can be identified in bottoming cycles, such as the conventional Organic Rankine Cycles (ORC) or the innovative supercritical CO₂ (s-CO₂) systems. This paper presents a detailed comparison of the potential of ORC and s-CO₂ as bottomers of industrial gas turbines in a Combined Heat and Power (CHP) configuration. Different gas turbine models, covering the typical industrial size range, are taken into account and both full- and part-load operations are considered. Performance, component dimensions, and operating costs are investigated, considering ORC and s-CO₂ systems specifics in line with the current state-of-the-art products, experience, and technological limits. Results of the study show that the s-CO₂ could be more appropriate for CHP applications. Both the electric and thermal efficiency of s-CO₂ bottoming cycle show higher values compared with ORC, also due to the fact that in the examined s-CO₂ solution, the cycle pressure ratio is not affected by the thermal user temperature. At part-load operation, the gas turbine regulation strategy affects the energy harvesting performance in a CHP arrangement. The estimated total plant investment cost results to be higher for the s-CO₂, caused by the higher size of the heat recovery heat exchanger but also by the high specific investment cost still associated to this component. This point seems to make the s-CO₂ not profitable as the ORC solution for industrial gas turbine heat recovery applications. Nevertheless, a crucial parameter determining the feasibility of the investment is the prospective carbon tax application.

In recent years, a rapid increase in the adoption of renewable energy sources and in the transition from a centralized electricity generation system to an increasingly distributed one has occurred. Within this scenario, in line with the European directives for achieving the objectives in the field of energy transition and climate change, energy communities are seen as potential contributors. The purpose of this work is to analyze the application potential of the energy community concept associated with district heating networks, leading to better overall energy-economic performance. This was demonstrated for a specific energy community in Italy, and it can be achieved by maximizing internal energy sharing—resulting from the electricity surplus generated by the photovoltaic system—and adopting different strategies that include heat pumps in order to maximize self-consumption and self-sufficiency, as well as to evaluate the most efficient investment in economic terms by exploiting the incentive tariff on shared energy. The results show that the performance of the system can be improved with the proposed design, achieving a significant reduction in the system’s energy demand, emissions and costs: compared to the reference case, the use of photovoltaics reduces primary energy demand by approximately 11%, while the addition of the energy community configuration allows emissions to be reduced by nearly 12%, with no additional investment.