In order to reduce greenhouse gas emissions and achieve global decarbonisation, it is essential to find sustainable and renewable alternatives for electricity production. In this context, the development of distributed generation systems, with the use of thermodynamic and photovoltaic solar energy, wind energy and smart grids, is fundamental. ORC power plants are the most appropriate systems for low-grade thermal energy recovery and power conversion, combining solar energy with electricity production. The application of a micro-scale ORC plant, coupled with Parabolic Trough Collectors as a thermal source, can satisfy domestic user demand in terms of electrical and thermal power. In order to develop a micro-scale ORC plant, a commercial hermetic scroll compressor was tested as an expander with HFC-245fa working fluid. The tests required the construction of an experimental bench with monitoring and control sensors. The aim of this study is the description of the scroll performances to evaluate the application and develop optimization strategies. The maximum isentropic effectiveness is reached for an expansion ratio close to the volumetric expansion ratio of the scroll, and machine isentropic effectiveness presents small variations in a wide range of working conditions. The filling factor is always higher than one, due to leakage in the mechanical seals of the scroll or other inefficiencies. This study demonstrates that using a commercial scroll compressor as an expander within an ORC system represents a valid option for such applications, but it is necessary to improve the mechanical seals of the machine and utilize a dedicated control strategy to obtain the maximum isentropic effectiveness.

The exploitation of renewable energies is a solution to the energy, economic and environmental issues related to the massive use of fossil resources. Thus, investing in renewable technologies is essential to achieve the carbon-neutral scenario within 2050. In this framework, geothermal energy may have a key role. In particular, power plants with a closed binary cycle are suitable for harnessing geothermal resources with low and medium enthalpy levels. They are prone to be integrated with other renewable devices to increase the global power output. Geothermal fluid can be drawn constantly from underground throughout the day and seasons. Conversely, the availability and intensity of solar energy depend on weather conditions and the time of year. In Italy, geothermal energy is currently harvested for continuous electricity generation, while solar energy is mainly used for photovoltaic generation. For small-to-medium size plants, rated between 5 and 20 MWe, the geothermal and thermodynamic solar hybridization may lead to relevant benefits for the economic competitiveness regarding separate photovoltaic or thermodynamic solar systems. This article aims to investigate the economic and environmental aspects of geothermal power plants with a closed binary cycle coupled with a topper cycle fed by linear parabolic solar collectors. The system operation in both design and off-design conditions was analysed, and exergo-economic and exergo-environmental simulations were conducted. The application site was selected near Torre Alfina (Italy). It has a water-dominant reservoir with a pressure of 44 bar, a temperature of 140 °C, and content of non-condensable gases (NCGs) approximately equal to 2% by weight. At the design point, the net power is 8.4 MW and the first and second principle efficiencies are 9.31% and 18.45%, respectively. The exergo-economic and exergo-environmental analyses indicate that the components with the highest economic and environmental impact are the condenser, the field of solar collectors, the evaporator, and the low-pressure turbine. The levelized cost of electricity (LCOE) is equal to 14.19 c€/kWh.

Nowadays it has become imperative to avoid the release of anthropogenic carbon dioxide into the atmosphere, which is the main cause of adverse climate change. Among the sectors that contribute the most to CO ₂ production are power generation and industrial processes. In the group of power generation systems, one of the most widely used on multiple fronts is the engine-generator set, due to its great versatility. Powered mostly by fossil fuels, it therefore emits a considerable amount of uncompensated CO ₂ into the atmosphere, so its long-term use requires solutions to avoid or, at least, reduce the release of not compensated CO ₂ into the atmosphere; one of them is the Carbon Capture, Utilization and Storage (CCUS). Several CO ₂ capture techniques are currently being studied extensively; the one considered in this article is the adsorption. An adsorption-type post-combustion capture system generally follows a cycle, which requires a certain amount of electricity to power auxiliaries and, more importantly, to compress the captured CO ₂ in order to use or store it. Since the adsorbent is in general very sensitive to the water vapour content of the gases stream to be treated, its abatement is required prior to the capture process. Various processes are used for this purpose, including an initial condensation by temperature lowering. In this study, it is investigated the possibility to recover the heat derived from the water vapour condensation to power an organic Rankine cycle (ORC) and generate electricity to be used for cooling the exhaust gases to the desired temperature and for the CO ₂ compression phase of the CCUS system. A thorough literature search on the subject has been carried out, particularly with regard to the type and size of expanders already commercially available or, at least, being studied, in order to match the size of the expander derived from the ORC design. Of the cycle, a preliminary design analysis has been carried out, i.e. the choice of the design point, the thermodynamic analysis (parameterized with respect to working fluid and maximum cycle pressure), and the sizing of the heat exchangers. Aspen HYSYS and Aspen Exchanger Design and Rating (EDR) have been utilised for modelling and simulation. In addition, a initial evaluation of the cost of the heat exchangers and the thermal machines has been carried out.