• Energy Research

In the evolving energy sector, where buildings are recognized as dynamic components of energy networks and smart grids, the implementation of new regulations and guidelines is crucial to optimize the interaction between buildings and the grid. The imperative to reduce building energy consumption facilitates the promotion of new technologies that rely on renewable energy generation and innovative materials. As technology has progressed, the multitude of energy vectors involved has made controlling energy systems increasingly challenging. This poses a barrier to the widespread adoption and implementation of cutting-edge technologies. In this framework, this paper explores an energy-efficient solution using an integrated photovoltaic/thermal collector and an active phase-change material storage system. The study optimizes the integration of technologies through a resistance capacitance model, assessing the impact on thermal comfort, energy savings and costs. A novel cascade methodology, combining particle swarm optimization search with model predictive control, is designed to select the optimal mode of operation for the proposed technologies. The economic feasibility of the proposed system is analyzed across different tariff structures, whereas the interaction with the grid is evaluated using energy flexibility key performance indicators. The energy and economic performance, as well as the flexibility of the system are assessed through a proof-of-concept conducted in an office building scenario. The results demonstrate an increase in energy efficiency, with savings ranging from 9% to 28% compared to a suitable baseline scenario, and a significant energy shift from on-peak to off-peak periods, potentially accounting for up to 46% of the total building load. This energy flexibility enables the grid to receive reduced demand during morning hours.

In 2030, 80% of the world's population will live in cities, when cities are responsible for over 70% of global carbon dioxide emissions. As the built environment accounts for 40% of the global primary energy consumption, changes need to take place towards the energy sustainable transition. The above, combined with Europe's aging building stock, bring the energy renovation and the building integration of active solar systems on existing buildings to the forefront of discussions. The research performed herein, investigates the effects on thermal comfort in public spaces caused by the building integration of active solar energy systems on existing facades in two coastal cities, Naples, Italy and Thessaloniki, Greece, using the Physiological Equivalent Temperature. A typical example of the urban system of each city is chosen, and active solar systems are integrated on the buildings’ facades. The thermal conditions on the street level are then simulated by the means of Envi-MET software. The aim is to compare the thermal conditions in the public space, before and after the integration, evaluated through different filters of solar urban planning/building integration of active solar systems, and subsequently focusing to propose the most viable combination of urban practice and building integration strategy.

In G. Pernigotto, F. Patuzzi, A. Prada, V. Corrado, & A. Gasparella (Eds.), Building Simulation Applications BSA 2017 (pp. 449–457).

Fifth generation district heating and cooling systems are becoming increasingly popular due to their ability for working with low temperature of heat transfer fluids. Among the other benefits, this characteristic allows for a better exploitation of renewable energy sources. On the other hand, these networks require a fine design and precise management to exploit their full potential. Both these requirements can be met by using advanced simulation and optimisation tools. This research proposes a simulation tool purposely conceived for the design and the optimisation of fifth-generation district heating and cooling systems. This tool is capable of assessing the effects of each building-plant system on the whole district heating and cooling water loop, and to evaluate the effectiveness of diverse network morphology. These capabilities are due the level of detail of the mathematical modelling which takes into account the thermohydraulic characteristics of the network, each building thermo-physics properties, and the heat pump/chiller detailed operation. The described tool has been adopted to simulate an existing experimental network prototype (consisting of a central heat pump, behaving as thermal energy balancing station, and eight users), and the achieved results were compared to those experimentally obtained for validation aims. The capabilities of the validated tool have been demonstrated by investigating an innovative control logic (representing a further novelty of this research) for a “proof-of-concept” fifth-generation district heating and cooling network. In particular, by adopting a predictive control logic, the water loop temperature is dynamically optimised to minimise the entire network energy demand. The adopted control strategy has yielded significant primary energy savings, amounting to 10.3 MWh/year, with a rate of 6.5 % compared to the reference case characterised by a fixed network temperature. These results underscore the potential of the proposed method and demonstrate the effectiveness of the developed tool.

Abstract This paper presents a novel dynamic simulation model for the analysis of a hybrid turboexpander system coupled with innovative high-vacuum solar thermal collectors. The model is developed in MatLab and it is able to dynamically calculate the energy, exergy, environmental, and economic performances of the investigated system, by taking into account the hourly fluctuation of thermodynamic and economic parameters (e.g. electricity cost, natural gas temperature, and flow rates, etc.). In addition, a computer-based Design of Experiment (DoE) approach was implemented for achieving the optimal design of the proposed system. A suitable case study is presented in order to show the capabilities of the developed simulation tool. Conventional and non-conventional decompression systems located in the weather zone of Messina (South-Italy) are investigated with the aim of assessing the optimal system configuration. By means of the computer-based DoE analysis, the optimal values of several design parameters (such as the number of solar thermal collectors, the volume of the hot water storage tank, and the size of the water loop pump) are calculated. Numerical results show significant primary energy savings (1.36 TWh/year) and avoided carbon dioxide emissions (348 tCO2/year). From the economic point of view, a feasible simple pay-back period of 4.51 years is achieved. The destroyed exergy of the system components are calculated, obtaining the highest value for the turbo-expander, equal to 12.0 TWh/year.

The energy impact of the transportation sector is consistently increasing. The European Union experienced a growth rate of 100% between 1990 and 2018, and current projections indicate that this growth trend is expected to persist over the next decade. In particular, the railway sector impacts a significant portion (up to 280 TWhel per year worldwide), and the energy consumption of HVAC systems has been found to be significant among various services provided on board, such as traction and auxiliaries, accounting for as much as 30% of the total energy requirements. This phenomenon can be attributed to the growing focus of stakeholders on ensuring a satisfactory thermal comfort experience while on board. In this context, the current manuscript suggests an innovative method for increasing the passengers' indoor thermal comfort while also taking the associated energy, economic, and environmental considerations into account. Specifically, it consists of an advanced comfort-optimal HVAC system control logic that prioritizes comfort, utilizing comfort-optimized indoor air setpoints. This innovative methodology surpasses the rule-based control logic proposed by the existing standards. To analyse the described control logic, a novel mathematical model for the energy, economic, and environmental performance analyses of modern train-HVAC systems has been developed. The simulation tool, validate through a code-to-code procedure, has the capability to incorporate weather data associated with actual railway paths, based on their location and orientation. To prove the potential of the proposed method and the capabilities of the developed dynamic simulation tool, a suitable proof-of-concept analysis has been conducted. In particular, for an existing railway coach operating in Italy, the standard and the innovative HVAC system control logics have been tested and compared in terms of energy, economic, environmental, and thermal comfort performance. The results of the analysis show that interesting thermal comfort hours increase (≃+1000 hours) and energy savings (-27%) can be achieved on yearly basis, proving the potential benefits achievable by the proposed method, and the capabilities of the developed tool.

This paper presents experimental and numerical analyses of a novel high-temperature solar cooling system based on innovative flat-plate evacuated solar thermal collectors (SC). This is the first solar cooling system, including a double-effect absorption chiller, which is based on non-concentrating solar thermal collectors. The aim of the paper is prove the technical and economic feasibility of the system, also presenting a comparison with a conventional technology, based on concentrating solar thermal collectors. To this scope, an experimental setup has been installed in Saudi Arabia. Here, several measurement devices are installed in order to monitor and control all the thermodynamic parameters of the system. The paper presents some of the main results of this experimental campaign, showing temperatures, powers, energies and efficiencies for a selected period. Experimental results showed that collector peak efficiency is higher than 60%, whereas daily average efficiency is around 40%. This prototypal solar cooling system has been numerically analysed, developing a dynamic simulation model aiming at predicting system performance. For a representative operating period, numerical data were compared with the experimental one, showing an excellent accuracy of the model. A similar system, equipped with Parabolic Trough solar thermal collectors (PTC) was also simulated in order to compare the novel solar collectors with such reference technology. For both systems a detailed thermo-economic model has been implemented in order to perform such comparison also from the economic point of view. Results showed that the rated energy performance of the prototypal solar cooling system featuring new collectors is better than that of the reference system. In particular, the difference between the novel and the reference solar cooling system becomes more and more significant, when considering the effects of dust and defocusing related to the tracking mechanism of concentrating collectors in harsh environments. Finally, from the economic point of view, results showed that the novel prototype was able to achieve a good profitability. (C) 2015 Elsevier Ltd. All rights reserved.

This paper aims to examine the integration of a hybrid photovoltaic/thermal (PV/T) solar system in an energy efficient, environmentally friendly, and technologically advanced prefabricated housing unit, to be considered as a cost and energy-saving solution of green construction. The study focuses on the energy production potential of the active solar system, in relation to the energy requirements of the housing unit, before and after the system's integration. For the energy and economic assessment of the proposed unit, a numerical investigation is developed in TRNSYS environment, in which the thermal and electrical behaviour of the coupled system – prefabricated house integrating the PV/T device - is conducted through dynamic simulations performed under Mediterranean and semi-continental climate conditions. Simulations are performed by considering the proposed prefabricated house with two modular wall units with and without integrating PV/T panels. A life cycle cost analysis is also developed to determine the viability of the enterprise, based on the only changing parameter between the reference (without PV/T) and the proposed case (with PV(/T). The results of the energy simulations and the life cycle cost analysis of the system are intended to assess the impact of the PV/T modules integration on the energy, economic, and comfort performance of the prefabricated building unit. Simulation results show that the proposed configuration leads to primary energy savings up to 548% for Larnaca, Cyprus, and up to 180% for Bolzano, Italy. It is observed that the energy savings are mainly due to the active effect of the proposed system (electricity production by solar renewable energy) that allows obtaining simple pay back periods ranging from 6.1 to 9.1 years for the simulated scenarios.