Informing on Best Practices Using Design Builder and RET Screen to Calculate Energetic, Financial, and Environmental Impacts of Energy Systems for Buildings

Buildings represent 32% of total final energy consumption. In terms of primary energy consumption, buildings represent around 40% in most IEA countries (International Energy Agency). For such reason, strategies that lead to energy savings and greenhouse gases reduction are needed. This research aims to provide a methodology able to identify the best system configuration from a technical, economic and environmental point of view by using at the same time two energy software: Design builder, which is able to calculate buildings energy needs under dynamic conditions, and RETScreen, which allows feasibility analysis of clean energy projects. In order to assess the effectiveness of this operating procedure, a historical building has been modelled and a Combined Cooling, Heat and Power system based on an internal combustion engine has been chosen to ensure environmentally sound way. In this study it shows the application of the procedure to a case study as an historical building located in Orte City which is near Rome in Italy; the methodology could get a real preliminary analysis for choose the best active or passive system for improve the energy efficiency and environmental sustainability of existing buildings, also allowing a cost-benefit analysis useful for the concrete realization of the interventions studied

Definition of parameters useful to describe dynamic thermal behavior of hollow bricks

Dynamic thermal behavior of hollow bricks is attracting much interest nowadays as there is much concern on energy performance of building envelope. In fact, high thermal inertia of outer walls provides mitigation of the daily heat wave, which reduces the cooling peak load and the related energy demand. Different approaches have been used to study dynamic thermal behavior within the papers available on unsteady heat transfer through hollow bricks. Actually, the usually employed methods for calculation of unsteady heat transfer through walls are based on the hypothesis that such walls are composed by homogeneous layers, so they are not suitable for many common building components. In this framework, a study on the dynamic thermal performance of hollow bricks is brought forth in the present paper. A critical review of available data from the literature is provided. Literature data are used to propose a parameter useful to predict dynamic thermal behavior. A finite-volume method is used to solve two-dimensional unsteady thermal fields in some standard bricks with different imposed temperature solicitations, with a numerical code developed by the authors. New results are used to check the effectiveness of the proposed parameters

Dynamic thermal features of insulated blocks: Actual behavior and myths

The latest updates in the European directive on energy performance of buildings have introduced the fundamental “nearly zero-energy building (NZEB)” concept. Thus, a special focus needs to be addressed to the thermal performance of building envelopes, especially concerning the role played by thermal inertia in the energy requirements for cooling applications. In fact, a high thermal inertia of the outer walls results in a mitigation of the daily heat wave, which reduces the cooling peak load and the related energy demand. The common assumption that high mass means high thermal inertia typically leads to the use of high-mass blocks. Numerical and experimental studies on thermal inertia of hollow envelope components have not confirmed this general assumption, even though no systematic analysis is readily available in the open literature. Yet, the usually employed methods for the calculation of unsteady heat transfer through walls are based on the hypothesis that such walls are composed of homogeneous layers. In this framework, a study of the dynamic thermal performance of insulated blocks is brought forth in the present paper. A finite-volume method is used to solve the two-dimensional equation of conduction heat transfer, using a triangular-pulse temperature excitation to analyze the heat flux response. The effects of both the type of clay and the insulating filler are investigated and discussed at length. The results obtained show that the wall front mass is not the basic independent variable, since clay and insulating filler thermal diffusivities are more important controlling parameters

thermal analysis of a solar cooling adsorption system by a dynamic model

Abstract—In this paper is shown the possibilities to implement an energy solar system, without auxiliary elements, made to cool. The new technologies (vacuumpacked tube, tanks of build-up with variable volume, etc.), allow the possibility to obtain easily a stand-alone refrigerating system. Today it is always more and more the case where during the summer season there is a surplus of thermal energy whose use is to be assigned within the energy optimization system. The most immediate solution to this problem is the ability to produce cold by means of simple adsorption solutions, thus contributing to the cooling problem with low COP values. The most beneficial adsorbent both for its thermal/physical and low cost is the silica gel, a polymer of silicon dioxide, commonly used for its dehydrating properties, especially in the preservation of electronic material [1,3,13]. In this study we have developed a dynamic model with the software trnsys to verify the obtaining of appropriate warm fluid for an innovative cooling system absorption with gel of silica and water and it is tested on a real building as case study. The dynamic model analyzes the performance thermodynamic balance of a small size system has been made (about 20-50 kW), adequate to cool a Building of 900 sq m. and allow to assess the conformation (surface, storage volume, etc.). of a new generation solar power plant is able to guarantee a continuous operation during the summer period [2]. We have tested a solar cooling system with solar vacuum collectors on a real Building with Meteo data of three Cities as Rome Milan and Tunisi and we have tested the model comparing the results obtained. The model in fact allows to make a preliminary design of principal part of the plant and to evaluate function cost-benefit of a complex investment for innovative technology The interesting results obtained allow at a later stage to make a prototype validating the theoretical results with experimental measures. Index Terms—Silica gel, Solar Cooling, Buildin

Analysis of thermal field within an urban canyon with variable thermophysical characteristics of the building's walls.

In a typical urban configuration, a microclimatic analysis has been carried out. Using a CFD method, a N-S oriented urban street canyon, with a given H/W ratio, has been examined. The standard k–ε turbulence model has been used to simulate a three-dimensional flow field and to calculate the thermo-fluid dynamics parameters that characterize the street canyon. In this study has been analyzed the thermal flow field when the walls of the building change the properties of solar radiation absorption, in particular for α=0.2 and α=0.8. Solar radiation considered is that of 21/07 in Milan in two different hours: at 11:00 a.m. and at 02:00 p.m. The study shows the importance of the thermophysical properties of a wall, in the development of the thermal field and flow field. This is a very important topic, in terms of improvement of well-being and the quality of the air within the cities, through the choice of materials and colors of the facades of buildings.

Energy and thermodynamical study of a small innovative compressed air energy storage system (micro-CAES)

There is a growing interest in the electrical energy storage system, due to the high penetration of the energy produced by renewable sources, the possibility of leveling the absorption peak of the electric network (peak shaving) and the advantage of separating the production phase from the exertion phase (time shift). Compressed air energy storage systems (CAES) are one of the most promising technologies of this field, because they are characterized by a high reliability, low environmental impact and a remarkable energy density. The main disadvantage of big systems is that they depend on geological formations which are necessary to the storage. The micro-CAES system, with a rigid storage vessel, guarantees a high portability of the system and a higher adaptability even with distributed or stand-alone energy productions. This article carries out a thermodynamical and energy analysis of the micro-CAES system, a result of the mathematical model created in a Matlab/Simulink® environment. New ideas will be discussed, as the one concerning the quasi-isothermal compression/expansion, through the exertion of a biphasic mixture, that will increase the total system efficiency and enable a combined production of electric, thermal and refrigeration energies. This is something promising for the development of an experimental devic

Thermal inertia of hollow wall blocks: actual behavior and myths

In the context of growing requirements to save energy in buildings and high objectives for Net Zero Energy Buildings (NZEBs) in Europe, strong emphasis is placed on the thermal performance of building envelopes, and in particular on thermal inertia to save cooling energy. High thermal inertia of outer walls leads to a mitigation of the daily heat wave, reducing cooling peak load and energy demand. Moreover, building envelopes with high heat capacity act as heat storages, increasing the effectiveness of natural ventilation for thermal comfort through a night-day energy shifting. Even though there are some papers available in the open literature on dynamic heat transfer through hollow bricks, yet common calculation methods are applicable to homogeneous layers only. That is the case of ISO 13786 regulation "Thermal performance of building components - Dynamic thermal characteristics - Calculation methods", for example. On the other hand, hollow blocks are very commonly used in building envelopes. Thus, available methods are not suitable for prediction of dynamic thermal performances. On the other hand, the widely common assumption that high mass means high thermal inertia leads to the use of higher mass blocks or bricks. Yet, numerical and experimental studies on thermal inertia of hollow envelope-components have not confirmed this general assumption, even though no systematic analysis has been found in the open literature. In this framework, numerical simulations of the thermal performance of hollow bricks have been done with a specifically-developed finite-difference computational code. Three common basic shapes with different void fraction and thermal properties have been analyzed with a triangular pulse solicitation, in order to highlight the relevance of front mass and other parameters on the thermal inertia, measured through heat wave delay. Results show that wall front mass is often misleading as thickness, number of cavities and clay thermal diffusivity are more important

In situ thermal characterization of existing buildings aiming at NZEB standard: A methodological approach

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A New Method of Technical Analysis to Optimise the Design of Low Impact Energy Systems for Buildings

Energy consumption for civil constructions represents about 40% of total energy requirements, so it is necessary to achieve the goal of energy savings and the consequent reduction of greenhouse gases emissions. The study in content aims to provide a design methodology enables to identify the best plant configuration for buildings from a technical, economic and environmental point of view. To assess validity of the calculation model, an analysis of an historical building was carried out in combination with two softwares of proven reliability: TRNSYS, used to evaluate the thermal demand of users, and RETScreen, used to estimate the validity of the chosen energy model