The installation of solar collectors applied or integrated into the building envelope may represent an interesting opportunity to increase the fraction of the building energy demands supplied through ...solar energy.
In particular, building solar thermal facades (BSTFs) could be very useful in high-rise buildings, which do not have sufficient spaces where to install a solar plant.
This paper aims to evaluate the energy performances of building solar thermal facades (BSTFs), constructed with two distinct types of solar collectors, flat plate (FPC) and evacuated solar collectors (ETC), through transient simulations, carried out with TRNSYS software, under different climate conditions. Moreover, an economic and LCA analysis on the two types of examined BSTFs were developed.
Additionally, this study presents a preliminary investigation on a prototype of ventilated building solar thermal facade (v-BSTF) built in Ragusa.
The results of such analysis highlight that BSTFs can represent suitable systems for the DHW production with great environmental and economic conveniences due to the short energy and CO2 payback times.
•Energy and environmental performances of building solar façades are presented.•Two scenarios have been studied, with flat plate and evacuated tube collectors.•TRNSYS software was used for carrying out the transitory simulations.•The performance of the building solar façades where analysed in four Italian cities.•A prototype of a ventilated building solar thermal facade (BSTF) is presented.
•Methodology to identify the best integration scenario of solar process heat is presented.•The methodology includes data gathering, performance simulation, and pinch analysis.•It was applied to a ...case study: a parabolic trough collector into a grape juice company.•Solar heat integration at process level increased the solar fraction.
A Chilean company dedicated to grape juice production used a 696 m2 parabolic trough collector to pre-heat the feed water of a liquefied petroleum gas boiler in a temperature range of 20–90 °C. During 2017 the solar field generated 241MWhth of heat, a low value for a concentration collector of such dimensions located in a place with high irradiation. This study presents a methodology to identify enhanced scenarios of solar heat integration into a grape juice industry and among them select the best scenario from an energetic perspective. This methodology started with data gathering of the thermal processes of the industry and the solar field (monitoring campaign and logbook of the industry) to generate the annual thermal demand. In a second step, the maximum theoretical generation potential of the solar field (1,107MWhth) was obtained with simulations in TRNSYS 18. Then, a Pinch Analysis to the process streams was performed to confirm that a higher solar heat integration potential (520MWhth) existed. The next step consisted of identifying different scenarios to increase the solar heat integration and analyzing them with simulations in TRNSYS 18 to identify the best-case scenario. The main increase on the solar fraction was achieved for the scenario when the collector working temperature was increased up to 140 °C and when heat was integrated at process level. Furthermore, it was concluded that one of the reasons for low solar fraction was the low thermal demand during months with high solar irradiation.
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To reach the EU 2030 goal of reducing greenhouse gas emissions targets, many apartments within residential buildings can be equipped with rooftop or building-integrated PV systems.
...However, as non-programmable renewable energy sources (solar, wind) are characterized by uncertainty and fluctuation, it is very difficult to match the supply with the demand for the building’s energy needs. Thermal and electric energy storage play a fundamental role in maximizing self-consumption, reducing the difference between peaks and valleys of the energy demand, and improving the electrical system's flexibility. In this study, the performances of an energy system composed of an electric heat pump (HP) fed by a PV plant and both thermal and electric storage are investigated. An innovative logic of the charge and discharge of the two storages as a function of energy generation and demand has been developed with the aim to optimize the energetic self-sufficiency of typical residential buildings. The results of the analyses carried out evidence that the system configurations with a thermal storage of about 1.000 L and an electrical storage of 5.0 kWh allow achieving rates of self-consumption and self-sufficiency of about 80%, which are 3 times higher than that one achievable by an energy system without storage. Moreover, this system configuration reduces dramatically the power exchange with the grid. The outcomes of this study are useful to provide indications for the design of the storage in combination with a solar-assisted heat pump system avoiding the recurrent praxis of oversizing of more than 100% of the electric storage.
•Switchable U-value as a way to cool buildings in summer when the outdoor temperature is lower than the indoor temperature.•Controlling the convection within closed elements as a new way of realizing ...a switchable U-value.•Experimental validation of the concept and parameter variation.•Simulation of the new element using TRNSYS show interesting potential.
To prevent the overheating of a well-insulated building in summer, façade elements with switchable U-value are a possible solution. A new translucent element with switchable U-value is presented. The convection around a translucent insulation panel is controlled by moving this panel vertically within the double glazing unit. Measurements of such elements show a possible switching of more than +100% of the U-value between the insulating and conducting state. Various geometries have been measured, and the influence of CO2 in the cavity has also been investigated. Based on the experimental results, TRNSYS simulations have been performed to investigate the overall performance of such a new element integrated in a real building. An optimized element could lead to a reduction of the cooling demand of up to 29.6% of the useful energy and to large improvements in the summer comfort.
Promotion of retrofit actions on existing buildings is a goal in Italy, since most of them were built before the 80′s when little attention was paid to energy saving. This paper presents an ...integrated passive design approach to reduce the heating demand and limit the costs of a representative existing residential complex located in Bologna, in the northern part of Italy. To this purpose, we explored different scenarios upon actions taken on the building structure: (1) High efficiency windows; (2) additional insulation on the external walls; or (3) the simultaneous application of high efficiency windows and improved thermal envelope, on both external walls and roofing. The numerical optimization has been performed dynamically using TRNSYS simulation tool, to evaluate energy consumptions in different structural conditions. Then, the developed model has been calibrated by the real consumption data deduced from energy bills (years 2009–2015). Finally, the energy results obtained in the above mentioned different scenarios have been evaluated under an economic assessment of cost investment: It has been highlighted that the payback time (PBT) results to be strongly influenced by the national policies of fiscal incentives. According to the present model, the most profitable condition is obtained when additional insulation on the external walls is applied: The total amount of energy saving resulted to be equal to 930.4 MWh, with an optimal PBT of roughly six years, when tax refund was contemplated.
A method is proposed to obtain the thermal properties of hollow clay blocks with integrated insulation for use in building energy simulation tools. Then, we show the significant impact of the ...interior coating on the dynamic thermal behaviour of these blocks. This method is composed of two numerical and two experimental phases. First, a numerical model in an unsteady regime has been created and calibrated by experimental studies on a wall sample tested in a guarded hot box. Finally, a validation phase is carried out by comparing TRNSYS simulations with in situ test data from a residential building. Finally, we provide reliable values for the thermal properties to be used in energy simulation software (equivalent thermal conductivity of 0.08 W.m
−1
.K
−1
, equivalent density of 630 kg.m
−3
and equivalent heat capacity of 430 J.kg
−1
.K
−1
).
This paper describes an integrated passive design approach to reduce the heating demand for an existing tertiary building through an improved thermal envelope design and high efficiency windows. The ...numerical optimization has been performed dynamically by means of TRNSYS simulation tool. The model here treated is aimed at the determination of the thermal demand with reference to a tertiary building in Italy, which it is supposed to be located in two different climatic zones, i.e., Bologna and Rome. The final part of the paper deals with the investment costs analysis, applied to each retrofitting scenario: it has been demonstrated that the simple payback period results to be strongly affected by the climatic zone of the building location and by the national policies of fiscal incentives.
In recent years, the interest of the scientific community towards building energy performance has become more evident in order to meet the National and European Directives. In this context, retrofits ...that result in improved building energy performance are widely investigated. The paper presents a comparative analysis of two different and complementary strategies to enhance the energy performance of an existing tertiary building located in Bologna, Italy. The first retrofit action is to reduce the heat transfer by transmission (i.e. use of low-emissivity glass) and the second one is to decrease the ventilation losses (i.e. installation of a heat recovery system). Then a third case has been investigated: it contemplates simultaneously both the solutions of windows replacement and installing a ventilation recovery system. Potential energy savings were calculated by means of dynamic simulation assisted by Trnsys energy simulation tool. Finally, an evaluation of the simple payback time and the net present value was performed in order to investigate global cost assessment. The window replacement option in the analyzed building office proved to be absolutely unprofitable, even if it would appear as the first and simplest action to be performed. On the contrary, the installation of a total energy recovery system resulted in sensible reduction of energy consumption and at the same time generated good values of NPV with reference to all the three different analyzed variation of the cost of energy.
Storage tanks with different cold water inlet devices for small Solar Domestic Hot Water (SDHW) systems are compared. The objective of the investigation is to reveal the impact of the cold water ...inlet device on the thermal stratification in two marketed tanks and to evaluate the possible enhancement in the annual system performance of small solar heating systems. Two different marketed inlet designs are compared, one connected to a small curved plate placed above the inlet tube, the other one connected to a much larger flat plate. The cold domestic water enters the stores in vertical direction from the bottom of the tanks. Temperature measurements were carried out for different operating conditions. It was shown that the thermal stratification inside the two tanks depends differently on the flow rate, the draw-off volume, as well as the initial temperature in the storage tank. To carry out system simulations, a multi-node storage model was used and expanded by an additional input variable to model the mixing behaviour depending on the operating conditions. The inlet device with a comparatively large plate compared to the less favourable design results in an increase of the solar fraction of about 1–3%-points in annual system simulations with a solar fraction of about 60% and fairly large domestic hot water flow rates. This corresponds to a reduction of the auxiliary energy supply of the solar heating system of about 3–7% (58–155
MJ/year) for the investigated solar domestic hot water system.
Energy simulations of buildings complement or replace the static calculations used so far and provide detailed answers to questions such as: what is the energy demand for individual purposes in a ...building and how does it change over the course of a day, a month, a year and also enable a comparison of several design variants and the selection of the optimal one in terms of energy consumption. Therefore, energy simulations of buildings help make decisions to optimise architectural and installation solutions, leading to a reduction in electricity, gas and water demand for the designed building. They indicate to what extent individual factors affect the demand for heating, cooling and electricity. The results of the analyses can be used as a basis for design and system decisions, and also provide interesting feedback to the investor.
This paper focuses on the year-round analysis of a three-zone building in TRNSYS. Attention is given to the values of the heat transfer coefficients through the envelope, heating and cooling demand, the effect of heat gains/losses on the energy demand of the building and thermal comfort. The article points out that the correct determination of the energy needs of a building influences the correct choice of renewable energy source and the lowest cost of installation.
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