A solar trigeneration system, based on photovoltaic-thermal (PV/T) collectors, photovoltaic (PV) modules and a heat pump unit for heating and cooling, is modelled to forecast the thermal and electric yields of the system. The aim of the trigeneration system is to provide enough electricity, domestic hot water (DHW), heating and cooling power to meet the typical demand of an urban single family dwelling with limited roof area and allow the household to achieve a positive net energy status. The PV/T collectors and PV modules provide the electricity while the former also powers the DHW component of the trigeneration system. The heating and cooling components rely on a vapour compression cycle heat pump unit powered by electricity. In Fong et al. (2010), solar-powered electric compression refrigeration was found to have the most energy saving potential in subtropical climates. Thus, a heat pump based cooling system is a cost effective solution for residential applications in Lisbon, Portugal. Thus, according to the dwelling's location, construction details and energy demand patterns, the model computes the system's net results by comparing the dwelling demand with the trigeneration system supply. The paper presents a breakdown of the proposed trigeneration system model and describes each component briefly. Preliminary results produced by the model are presented and analysed in order to identify possible ways of improving the overall system performance. IntroductionA trigeneration system is capable of simultaneously generating electricity, heat and cooling power from a single power source. Such a system uses complementary processes to convert the by-products of the main energy conversion and obtain forms of energy which are in line with demand. For instance, a gas-powered turbine driving an electrical generator produces electrical energy and waste heat. The waste heat can be used to produce hot water and power an absorption chiller. The same concept can be applied in solar power plants. Solar radiation is harnessed and converted to heat used to power a turbine which then drives an electrical generator, producing electricity. Heat is an evident by-product of this conversion and can be used for the aforementioned trigeneration system. Also, solar collectors and photovoltaic modules can be used to harness solar energy and convert it to heat and electricity, respectively, which may be used to power several cooling technologies (Fong et al., 2010, Immovilli et al., 2008. The aim of this article is to demonstrate the potential of a solar trigeneration system for the residential sector by describing a model, the methodology that led to that model and analysing a set of preliminary results. Solar Trigeneration System for the residential sectorA turbine-based solar trigeneration system is not suitable for the residential sector due to, among other concerns, scale, size, power rating, initial cost and maintenance. Instead, a solar trigeneration system developed specifically for the residential sector can be envisaged b...
Humanity has been discussing aspects like environment, sustainable development, public health, leisure and work. Connections between these aspects are increasing its importance to decision makers. Urban air quality levels are one of the most important items, concerning public health in urban environment. The knowledge of pollutants influence on human health is a matter of major importance nowadays, and it is known that personal exposure to particle concentration is a key factor in citizens' health. Aspects like street geometry, motorways, pedestrian ways, traffic strategies, time and schedules, can influence air quality levels and consequently human exposure. This paper studies the influence of street geometry, wind direction, daily car traffic, pedestrian trajectories and particle matter concentration (PM 10 ) levels in short-term personal exposure on a busy street of Barreiro City in Portugal. Ansys Fluent was used to simulate particle dispersion in Bocage Street. Buildings' height, width, length and geometry, as well as distance between buildings and road width were considered in the simulation work. Different meteorological conditions were simulated, namely, wind direction and wind velocity.The results show that pollutant concentration is highly dependent on street geometry and wind conditions. The pedestrian trajectories and their time schedules also play a major rule in short-term personal exposure to PM 10 . It was noticed that when the building's orientation is the same as the wind, good pollutant dispersion is promoted. Also different size in buildings promotes recirculation that can be positive, increasing the wind velocity and promoting pollutant dispersion, if the wind direction is from North, or negative trapping pollutants when the wind is from South. It is also possible to conclude that pedestrian trajectories that correspond to crossing the road in the centre of the street results in the highest values in terms of short-term personal exposure to PM 10 .
This article is describes a study about the air flow distribution inside a refrigeration chamber, using computational fluid dynamic (CFD) simulation. The software used to perform this study was Fluent 14, from Ansys. The main objective was to study the air flow inside a cold chamber and the influence of air deflection and other strategies to achieve a better efficiency in air flow, under partial load product conditions. Special attention was given to the situation when a small quantity of product is located in a small part of the chamber. Measurements of temperature and air velocity were made inside the cold chamber, to validate the model. The results demonstrate that the air recirculation inside the refrigerated chamber, when loaded by a reduced quantity of product, is strongly influenced by the localization of product and localization of evaporator. To this situation the best air circulation of interior air is achieved by the introduction of an air deflector outside the evaporator
Abstract.A solar trigeneration system for off-grid households, based on photovoltaic-thermal (PV/T) collectors, photovoltaic (PV) modules and a heat pump (HP), whose aim is to provide enough electricity, domestic hot water (DHW), heating and cooling power to meet the typical demand of an offgrid single family dwelling, is modeled to predict its performance, enable system sizing and evaluate the impact of different control and management strategies. The system integrates an autonomous photovoltaic system, a solar DHW system and a heating, ventilation and air-conditioning (HVAC) system. Thus, according to local climate data, construction elements, load profiles and storage dynamics, the model computes the system's net results using a simple supply and demand approach. Additionally, a design space methodology is used to evaluate system performance for different sizes and identify a feasible design region within which reliable and cost-effective system sizing is possible.
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