Solar cooling: a case study

Throughout the years various methods for heat prevention and indoor temperatures control in the summer have been used. The alternative cooling strategies are based on various passive and low energy cooling technologies for protection of the buildings via design measures or special components to moderate the thermal gains, or to reject the excess heat to the ambient environment. All these techniques aim to reduce summer cooling loads and electricity demand for air conditioning. During the summer the demand for electricity increases because of the extensive use of heating ventilation air conditioning (HVAC) systems, which increase the peak electric load, causing major problems in the electric supply. The energy shortage is worse during ‘dry’ years because of the inability of the hydroelectric power stations to function and cover part of the peak load. The use of solar energy to drive cooling cycles for space conditioning of most buildings is an attractive concept, since the cooling load coincides generally with solar energy availability and therefore cooling requirements of a building are roughly in phase with the solar incidence. Solar cooling systems have the advantage of using absolutely harmless working fluids such as water, or solutions of certain salts. They are energy efficient and environmentally safe. The purpose of this paper is to describe a Solar Cooling System to be installed on the roof of a building in Rome, the headquarters of the State Monopoly. The medium size power plant is composed of the following components: − Solar Collectors; − Thermal Storage Tank; − Absorption Chiller; The plant design is based on a dynamic simulation in TRNSYS, a dynamic simulation tool used by engineers all over the world to make energy calculations in a transient state

Bioclimatic design, assisted by numerical simulation in a transient state

The bioclimatic design aims to realize designing, localizative technological, plant-engineering choices, in order to have a housing model that satisfies comfort requisites through microclimate passive control and the control of the energy for heating plants. The study in this field is booming and, thanks to fast and effective calculation systems, the researchers can achieve reliable outcomes in reasonable times. Starting by a good thermal-energetic design and a bit of intuition, the bioclimatic design issue has been tackled scientifically and sistematically. So, we reached spe-cific and general conclusions useful to quantify and select the most used technics in this field. Our work doesn’t aim at a strict demonstration but at a study through which verify, understand and in-crease the knowledge of thermal-energetic phenomenon of building-environmental interaction. Many of the simulations in transient state have been made on matters we considered the most influential on the global behaviours of residential buildings. The matters on which we focused are: thermal cover (ther-mal insulation and inertia), glazed surfaces, screenings (static and mobile), in direct geothermal energy, vent (natural and artificial, diurnal and nocturnal). All this work has the aim to create the right balance between naatural cooling and heating during a while year, in order to guarantee thermal comfort to residents, thereby decreasing to a minimum the use of plants during the summer and the winter. The consequent designing-technical choices come from scrupulous interpretation of the outcomes, achieved by extrapolating from generic treatment the compatibility with the climatic conditions. In this per-spective, the authors, with the research, are using their knowledges to get innovative outcomes and integrate the research with empirical matters. residential buildings. The matters on which we focused are: thermal cover (ther-mal insulation and inertia), glazed surfaces, screenings (static and mobile), in direct geothermal energy, vent (natural and artificial, diurnal and nocturnal). All this work has the aim to create the right balance between naatural cooling and heating during a while year, in order to guarantee thermal comfort to residents, thereby decreasing to a minimum the use of plants during the summer and the winter. The consequent designing-technical choices come from scrupulous interpretation of the outcomes, achieved by extrapolating from generic treatment the compatibility with the climatic conditions. In this per-spective, the authors, with the research, are using their knowledges to get innovative outcomes and integrate the research with empirical matters

A STUDY OF THE INFLUENCE OF THE VEGETATION ON THE CLIMATIC CONDITIONS IN AN URBAN ENVIRONMENT

This work was about the study of the variations of the climatic parameters in an urban area bordering a green area. The problem of the great urbanization of the territory led to the registration of high temperatures in the cities, during the summer. Such a phenomenon, called “heat island”, is caused by the employment of those materials used for the urbanization of the territory, that have different responses to the solar radiations that influences the naked soil or on a soil with vegetation. Actually, the presence of a green area in a territory strongly urbanized changes its environmental parameters and those of a bordering zone. In particular, it is possible to record the variation of air and soil temperature and the variation of the wind speed and direction. It as been studied a typical urban context, in which a green area is surrounded by an urbanized area constituted by buildings, car parks and streets totally asphalted. Then the effect of different types of vegetation on the urban area climate has been evaluated, with the help of numerical analysis, and, moreover, the influence area of a specific green area on the bordering urban context has been studied. The computational model employed is the software ENVI-MET that successfully reproduces the interaction among urban surfaces, the vegetation and the atmosphere. The outcomes achieved help to understand how a green area modifies a city climate, making an area climatically more benign both under the comfort point of view for the people living there and under the energetic point of view

SIMULATIONS OF TURBULENT ISOTHERMAL FREE JETS

In present work fluid-dynamic behavior of plan isotherm and axisymmetric three-dimensional turbulent air jets in free field has been developed. The study has been led by means of a fluid-dynamic numeric analysis (CFD) with particular attention to discretization type and boundary conditions influence on mathematical solution. Velocity variation along jet axis and on transversal sections has been determined; then results have been compared with data available in literature. Fluid-dynamic jets behavior has been studied with particular attention on entrainment and mutual influence among two or more jets, in accordance with their distance, with the aim of giving useful information about velocity field for ventilation plants project and construction. Mathematical model defined for two-dimensional and axisymmetric three-dimensional problems led us to good results; so in next works the methodology will be extended to three-dimensional phenomena

Study of the behaviour of the shutter prototype for non-residential, aimed at containing the summer heating load

This research aims at realising a shutter prototype which would allow the containment of the summer heating load in non-residential buildings. The prototype will be constructed with glass-block and will overhang the façade. It will be parallelepiped shaped; furthermore, it will have an isosceles section with the larger base positioned at the top of the hole forming, thus, a plan perpendicular to the façade and overhanging by 0,40 cm. With its positioning at the height of the envisaged holes and its particular geometrical shape, this prototype will replace the standard vertical shutter with one containing glass-block with a sharp inclination with respect to the incidence of the sun rays in the summer time. A measurement campaign is envisaged in order to optimize the glass inclination with respect to the incidence of the sun rays both during the winter and the summer time and the width of the horizontal anti-dazzle screen placed at the top of the shutter. The objectives of this research are: - Minimising overheating during the summer through the inclination of the glass surface; - Reaching a high level of visual comfort; - Realising a monitored natural ventilation. The horizontal overhang surfaces of the shutter will be equipped with a series of holes controlled by a system of rotating thin plates which, once positioned vertically, will allow the proper circulation of air and a further source of natural light. Furthermore, the geometrical shape of this prototype allows for the control of te shades; the holes on the higher and lower horizontal surfaces will guarantee a natural ventilation so to ensure the proper level of air moisture. The lack of mobile or steady anti-dazzle screens ensures a perfect view of the external surroundings; in addition to this, the standard levels envisaged for by the existing regulations on natural lighting on the back wall will not be altered. The aim of this work is that of providing a passive element which could concretely guarantee a high level of acoustic and visual comfort, and a proper ventilation in indoor non-residential environments