• Energy Research

Abstract It has been estimated that the world's consumption of Liquefied Natural Gas (LNG) will increase significantly over the next 20 years, thus making exergy recovery from the regasification process a fundamental issue. When LNG is regasified in order to distribute the fuel through a pipeline network, a large amount of exergy is released. Three combined cycle schemes for energy generation have been analysed in this paper: the first one is a direct expansion cycle, combined with a Rankine cycle, the second one presents a double expansion with reheating and a recovery heat exchanger, and the last one shows two parallel Rankine cycles working under different turbine pressures. The performance of the three cycles has been compared, and the effects of using working fluids with different characteristics have been analysed in detail. Twelve working fluids were selected, according to their thermodynamic, ambient and safety proprieties. The working pressure and temperature that maximise the specific work have been found for each cycle and fluid.

Abstract The increased use of fluctuating renewable energy sources (RES) that is expected in the near future will lead to challenges concerning their full integration in the distribution grid, the reduction of RES curtailments and the mitigation of electric unbalances on the grid. Besides electric batteries (EB), other technologies, such as Power-to-Gas (P2G), Power-to-Heat (P2H) and Combined Heat and Power (CHP), make it possible to exploit synergies between various energy networks, thus alleviating problems of RES integration. In fact, when these technologies work simultaneously in a single energy system, their installed power mix, along with their optimised management and control, play a fundamental role in the energy optimisation of the whole system. The aim of this paper is to offer a methodological approach for the analysis of the synergies between the different energy networks in order to cope with the increasing RES penetration. The proposed model has been used to perform a sensitivity analysis on the installed capacity of the various technologies; moreover, different simplified system management logics have been analysed by changing the priority order of the renewable energy surplus usage. The obtained results have been compared from an energetic, economic and environmental point of view.

Renewable Energy Sources are a viable solution to reduction carbon footprint and pollution. To front the high variability of the energy demand storage system must be added to RES to avoid energy curtailment.To coordinate the energy production with the demand and the storage an ICT platform operating over several levels is necessary to optimize the system behaviour.In this paper the implementation of a possible control system is described with specific reference of the PLANET project for two pilot sites located in France and Italy

Renewable Energy Sources (RES) have taken on an increasingly important role in the energy mix in the last few years, and it has been forecasted that this trend will continue in the future. The energy production from these sources is not dispatchable, and the increasing penetration of RES in energy mixes may therefore lead to a progressive loss of generation control and predictability. It has become clear that, to reach higher RES penetration levels, it is essential to increase power system flexibility in order to ensure stable operations are maintained. An ICT (Information and Communication Technology) tool that may be used to manage and optimize the flexibility offered by energy storage and conversion systems is described in this paper with specific reference to the Decision Support System (DSS) developed within the H2020 PLANET (PLAnning and operational tools for optimizing energy flows and synergies between energy NETworks) project. The paper focuses on how the PLANET DSS tool evaluates, manages, and dispatches the flexibility of Power to Gas/Heat (P2X) technologies. Moreover, the tool has been used to analyze a realistic case in order to show how the PLANET DSS tool could be used to evaluate the energy and economic benefits of taking advantage of the flexibility of P2X technologies.

Abstract The current solutions for power generation include a wide range of technologies, each providing specific advantages and limitations. In a decarbonization perspective, their carbon intensity will represent a crucial factor in determining their success towards a future low-carbon electricity mix. Today, natural gas combined cycles are among the most efficient plants, especially when operating in combined heat and power mode. This paper presents the analysis of the actual carbon intensity of a large-scale natural gas combined cycle, calculated on an hourly basis over several years of operational data, compared with the average hourly emissions of the Italian power grid both with the most recent electricity mix and the forecast to 2030 and 2040, based on the decarbonization targets that are currently in place. The results of this study highlight the very low carbon intensity of the electricity produced in CHP mode, with average monthly values as low as 242 g/kWh during the winter months, compared to around 350 g/kWh when operating in full-electric mode in summer. These values are lower than the current performance of the Italian electricity mix in winter, although the opposite is true in summer, confirming the importance of the cogeneration in decreasing the carbon intensity of the energy output. However, in a future low-carbon electricity system, fossil gas CHP units will have higher carbon emissions than the average mix. In order to achieve the decarbonisation objective it is necessary to take these considerations into account. The availability of a high-resolution estimate of the performance of power generation will support policy makers in developing strategies to deploy the most effective technologies to decarbonize the energy system.

The increasing resort to renewable energy distributed generation, which is needed to mitigate anthropogenic CO2 emissions, leads to challenges concerning the proper operation of electric distribution systems. As a result of the intrinsic nature of Renewable Energy Sources (RESs), this generation shows a high volatility and a low predictability that make the balancing of energy production and consumption difficult. At the same time, the electrification of new energy-intensive sectors (such as heating) is expected. This complex scenario paves the way for new sources of flexibility that will have more and more relevance in the coming years. This paper analyses how the electrification of the heating system, combined with an electric flexibility utilisation module, can be used to mitigate the problems related to the fluctuating production of RES. By using Power-to-Heat (P2H) technologies, buildings are able to store the overproduction of RES in the form of thermal energy for end-use according to the principle of the so-called Virtual Energy Storage (VES). A context-aware demand flexibility extraction based on the VES model and the flexibility upscale and utilisation on district-level through grid simulation and energy flow optimisation is presented in the paper. The involved modules have been developed within the PLANET (PLAnning and operational tools for optimising energy flows and synergies between energy NETworks) H2020 European project and interact under a unified co-simulation framework with the PLANET Decision Support System (DSS) for the analysis of multi-energy scenarios. DSS has been used to simulate a realistic future energy scenario, according to which the imbalance problems triggered by RES overproduction are mitigated with the optimal exploitation of the demand flexibility enabled by VES.