• Energy Research

The constant attention to sustainability aimed at reconciling economic and social development with environmental protection is the driving force of the continuous growth of renewable energy in the energy sector. Among the numerous actions taken by the European Commission (EC) in this direction, an important initiative towards the complete decarbonization is represented by the Renewable Energy Communities (RECs). According to the EC, “energy communities enable collective and citizen-driven energy actions to support the clean energy transition. They can contribute to increasing public acceptance of renewable energy projects and make it easier to attract private investments in the clean energy transition”. At the European level, numerous energy communities are emerging, although they are all based on photovoltaic production and, consequently, focus only on electricity flows. The aim of this paper is to define a thermal energy community in which thermal energy sharing can be achieved by exploiting the concept of the smart district heating network. Starting from a small existing district heating network, its conversion into a smart one will be analyzed and optimized with the aim of studying the sharing of thermal energy between the various prosumer and non-prosumer users connected to the district heating network.

Abstract Governments around the world strive to achieve ambitious targets of incorporating considerable amounts of distributed renewable generation and combined heat and power, in response to the climate-change challenge and the need to enhance fuel diversity. The scientific interest is moving toward off-grid power generation systems, based on conventional and/or renewable sources, often coupled with storage devices, which distribute power through a local grid network. This approach, applied to increase electricity access especially in remote areas, is effective to reduce poverty, mitigate climate change and improve the resilience. In this framework, the paper presents the assessment of different renewable sources for power generation in Nepal, aimed to (i) optimize the energy fluxes, (ii) evaluate the long term energy balance by comparing productions and consumption, (iii) preliminary size a multiple input/output storage device on the basis of specific boundary conditions. The study is geographically set within the Khumbu Valley, in the central part of the Himalayan Range, East Region of Nepal, recently damaged by severe seismic events causing serious consequences on population and territory. The specific features of the reference context have been assessed from different points of view, focusing on climate data, energy consumption, and available resources. Wind potential in several spots around Namche Bazar region was estimated using CFD methods, and a customized micro wind turbine – projected by University of Perugia – has been simulated to estimate a hourly production profile. With an accurate analysis of wind data and air density effects, it is possible to test energy production potential in areas with high average wind speed. The overall productions from wind turbines and solar PV panels were coupled with household load profiles; a storage system has been preliminary sized accounting technical and logistic aspects, e.g. charge limits of lead acid batteries and portability of the components in extreme conditions. Finally the avoided emissions were quantified in order to evaluate the mitigation effects on climate change.

The European and national regulations in the decarbonisation path towards 2050 promote district heating in achieving the goals of efficiency, energy sustainability, use of renewables, and reduction of fossil fuel use. Improved management and optimisation, use of RES, and waste heat/cold sources decrease the overall demand for primary energy, a condition that is further supported by building renovations and new construction of under (almost) zero energy buildings, with a foreseeable decrease in the temperature of domestic heating systems. Models for the simulation of efficient thermal networks were implemented and described in this paper, together with results from a real case study in Italy, i.e., University Campus of Parma. Activities include the creation and validation of calculation codes and specific models in the Modelica language (Dymola software), aimed at investigating stationary regimes and dynamic behaviour as well. An indirect heat exchange substation was coupled with a resistive-capacitive model, which describes the building behaviour and the thermal exchanges by the use of thermos-physical parameters. To optimise indoor comfort conditions and minimise consumption, dynamic simulations were carried out for different operating sets: modulating the supply temperature in the plant depending on external conditions (Scenario 4) decreases the supplied thermal energy (−2.34%) and heat losses (−8.91%), even if a lower temperature level results in higher electricity consumption for pumping (+12.96%), the total energy consumption is reduced by 1.41%. A simulation of the entire heating season was performed for the optimised scenario, combining benefits from turning off the supply in the case of no thermal demand (Scenario 3) and from the modulation of the supply temperature (Scenario 4), resulting in lower energy consumption (the thermal energy supplied by the power plant −3.54%, pumping +7.76%), operating costs (−2.40), and emissions (−3.02%). The energy balance ex-ante and ex-post deep renovation in a single user was then assessed, showing how lowering the network operating temperature at 55 °C decreases the supplied thermal energy (−22.38%) and heat losses (−22.11%) with a slightly higher pumping consumption (+3.28%), while maintaining good comfort conditions. These promising results are useful for evaluating the application of low-temperature operations to the existing district heating networks, especially for large interventions of building renovation, and confirm their potential contribution to the energy efficiency targets.

Life Cycle Assessment (the systematic analysis of the environmental impact of products during their entire life cycle), Carbon Footprint and Water Footprint assessments play an important role in decision-making processes. These assessments can help guide land management decisions and will likely play a larger role in the future, especially in natural areas with high biodiversity. Agriculture is a substantial consumer of fresh water, so it is important to identify causes and possible solutions to optimize agricultural water use. Water footprint assessments consider water consumption from several points of view and aid in reaching Sustainable Development Goals. Olive trees are a widespread agricultural crop growing in the Mediterranean Basin and are particularly important in the Umbria region in Italy. This paper estimates the water footprint impact related to the production of 1 kg of olives in a rainfed olive orchard managed using low environmental impact techniques. Eleven years of data collection (meteorological data, olives yield data, processes data) are analyzed for typical rural conditions. The results show that local management techniques have lower water requirements than standard international usages. These results can be used to improve and to further explore agricultural water use.

Abstract SCADA control systems are the keystone for reliable performance optimization of wind farms. Processing into knowledge the amount of information they spread is a challenging task, involving engineering, physics, statistics and computer science skills. This work deals with SCADA data analysis methods for assessing the importance of how wind turbines align in patterns to the wind direction. In particular it deals with the most common collective phenomenon causing clusters of turbines behaving as a whole, rather than as a collection of individuality: wake effects. The approach is based on the discretization of nacelle position measurements and subsequent post-processing through simple statistical methods. A cluster, severely affected by wakes, from an onshore wind farm, is selected as test case. The dominant alignment patterns of the cluster are identified and analyzed by the point of view of power output and efficiency. It is shown that non-trivial alignments with respect to the wind direction arise and important performance deviations occur among the most frequent configurations.

The performance of the innovative configurations of the “efficient” thermal networks is a key topic in scientific research, focusing on distribution temperatures and integration with high-efficiency plants and renewable sources. As it already happens for the electricity prosumers, a thermal prosumer may feed the district heating network through a bidirectional exchange substation with the excess of the locally produced thermal energy (e.g., by means of solar thermal plant) or with the waste heat recovered in the industrial processes. The Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA) and the Alma Mater Studiorum University of Bologna (UNIBO) designed a bidirectional substation prototype, based on a return-to-supply configuration, and tested steady-state and dynamic conditions to evaluate performances and optimization measures. In this paper, the Modelica language and Dymola software were used to run a multi-domain simulation and model-based design of the substation, starting from a new heat exchanger model featuring variable efficiency, based on the thermal resistance scaling method. Control systems and components were customized from models in standard libraries in order to reproduce the substation behavior under defined operating settings, and the model was validated on the abovementioned experimental tests. Numerical results in terms of exchanged powers, temperatures and flow rates were systematically compared to experimental data, demonstrating a sufficient agreement. In particular, the absolute mean deviation—in terms of temperature—between experimental and numerical data assessed over the entire tests remains contained in +/−1 °C. As further step of the analysis, an optimized model could be included as a component in a district heating network for further investigations on the prosumers’ effects on an existing traditional grid (e.g., in case of deep renovation of urban areas connected to district heating and/or creation of micro energy communities).

Abstract The present study aims at assessing environmental and energy compatibility of different solutions of thermal insulation in building envelope. In fact a good insulation results in a reduction of heating/cooling energy consumptions; on the other hand construction materials undergo production, transformation and transport processes, whose energy and resources consumptions may lead to a significant decrease of the environmental benefits. The paper presents a detailed carbon footprint of a product (CFP, defined as the sum of greenhouse gas emissions and removals of a product system, expressed in CO2 equivalents), which is a reflective foil conceived and produced by an Italian company. CFP can be seen as a Life Cycle Assessment with climate change as the single impact category; it does not assess other potential social, economic and environmental impacts arising from the provision of products. The analysis considers all stages of the life cycle, from the extraction of raw materials to the product’s disposal, i.e. “from cradle to grave”; it was carried out according to UNI EN ISO 14040 and 14044, and LCA modelling was performed using SimaPro software tool. On the basis of obtained results, different measures have been proposed in order to reduce emissions in the life cycle and neutralize residual carbon footprint. The results allowed to make an important comparison concerning the environmental performance of the reflective foil in comparison with other types of insulating materials.

In the last years, the growing demand for air conditioning has caused a significant increase in demand for primary energy resources. Solar-powered cooling is one of the technologies which allows to obtain, by using the renewable solar source, an important energy saving compared to traditional air conditioning plants. The paper describes different technical installations for solar cooling, their way of operation, advantages and limits. The objective of the present study has been to analyze the technical and economic feasibility of solar absorption cooling systems, designed for two different application fields: industrial refrigeration and air conditioning. The possibility to replace or integrate the existing plants is studied, by considering the refrigeration requirements of a company, which works in meat manufacturing, and the heating and cooling demands of a hotel located in a tourist town in Italy. In the first case, the system comprises an absorption chiller coupled to solar flat plate collectors, whereas the second application is about a hybrid trigeneration plant, known as thermo-solar trigeneration; this option allows having greater operational flexibility at sites with demand for energy in the form of heating as well as cooling, for example in a hotel. In this way the authors could compare different results obtained by a technical and economic experimental analysis based on existing users and evaluate the advantages and disadvantages in order to suggest the best solution for the two studied cases.

Abstract In recent years, the role of Life Cycle Assessment (LCA) of products and processes has increased in importance, since it is the best technique to quantify environmental impacts associated with a process or product. The study was carried out in an olive grove located in Central Italy with “Leccino” cultivar. The olive grove was established in year 2000 with a planting distance of 5.5 × 5.5 m, trained to the vase system, under dry conditions. The same methodology used for forestry trees (“model tree”) was adopted to estimate the biomass and the respective carbon stock of the below-ground and above-ground parts of the olive tree as well as quantification of the non-permanent components periodically removed, i.e. fruits and prunings. The environmental impacts associated with management processes were evaluated according to LCA standards (UNI EN ISO 14040 and 14044). In relation to the impact on climate change, the CO2 sources and sinks were calculated in order to obtain the net carbon stock of the olive grove. These data were confirmed by experimental measurement of the tree biomass in three representative olive trees. The treatments and processes that had the greatest impact were identified and the individual phases and materials were then analysed in order to propose possible actions for reducing emissions throughout the entire olive grove life cycle. Removals and emissions were compared on a time scale, in order to identify the break-even point. The results allow to assess the carbon footprint of an olive grove, at different stages of its life cycle, as a support tool for creating a sustainable production chain in the olive sector. The paper proposes a methodological approach that can be adopted also in other olive groves with different horticultural management models.

The 2012 European energy efficiency directive supported the development of cogeneration combined heat and power (CHP) and district heating and cooling (DHC) networks, stressing the benefits of a more efficient energy supply, the exploitation of recovered heat, and renewable resources, in terms of fuel consumption and avoided costs/emissions. Policy decisions play a crucial role: technical and environmental feasibility of CHP is clear and well demonstrated, whereas economic issues (fuel prices, incentives, etc.) may influence its actual application. In this framework, the introduction of low-carbon technologies and the exploitation of renewable energies are profitable interventions to be applied on existing plants. This work focuses on a small CHP plant, installed in the 90 s and located within a research facility in Italy, designed to supply electricity and heat/cool through a district network. On the basis of monitored consumption of electricity, heating, and cooling, energy fluxes have been analyzed and an assessment was performed to get a management profile enhancing both operational and economic parameters. The integration of renewable energies, i.e., solar-powered systems for supporting the existing devices, has been evaluated, thus resulting in a hybrid trigeneration plant. Results demonstrate how the useful synergy between CHP and DHC can not only be profitable from the economic point of view, but it can also create conditions to considerably boost the integral deployment of primary energy sources, improving fuel diversity and then facing the challenge of climate change toward sustainable energy networks in the future.