Reducing CO2 in Passivhaus-Adapted Affordable Tropical Homes (original) (raw)
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Research & Development
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Positive energy residential buildings are houses that generate more energy from renewable sources than they consume while maintaining appropriate thermal comfort levels. However, their design, construction and operation present several critical challenges. In particular, the considerable load reductions are not always compatible with the increased level of comfort expected in modern houses. Tropical climates, meanwhile, should be more amenable to the implementation of positive energy houses for two reasons. Firstly, negligible heating is generally required as compared to colder climates, where the heating energy requirements are considerable. Then, renewable energy resources are usually abundant in tropical climates. This paper investigates the feasibility of positive energy residential buildings in the tropical island of Mauritius. A baseline model representing a typical Mauritian house is designed using DesignBuilder software. The energy efficiency of the model is then optimised by investigating a whole range of passive building design strategies, many of them adapted from vernacular architecture. Results reveal that the application of passive strategies such as shading, insulation and natural ventilation have precluded the need for artificial cooling and ventilation in the positive energy (PE) house. The resulting electricity consumption of the house decreases from 24.14 to 14.30 kWh/m 2 /year. A 1.2 kW photovoltaic system provides the most cost-effective solution to exceed the annual electricity requirements of the house.
Energies
Different methods to achieve zero-energy and low carbon on the scale of a building are shown by most of the research works. Despite this, the recommendations generally offered by researchers do not always correspond to the realities found during the construction of new buildings in a determined region. Therefore, a standard may not be valid in all climate regions of the world. Being aware of this fact, a study was carried out to analyse the design of new buildings respecting the “zero-energy and low carbon emission” concept in tropical climatic regions when they are compared with a base case of temperate regions. To reach this objective, the comparison between real and simulated data from the different buildings studied was developed. The results showed that the renovation of existing residential buildings allows for reducing up to 35% of energy demand and a great quantity of CO2 emissions in both climate types. Despite this, the investment rate linked to the construction of zero-en...
This Paper addresses operational energy and indoor comfort with particular focus on simple retrofit solutions for low-cost housing in developing countries. Technical innovations may eventually "trickle down" to the poor, though that notion is often queried, but in the meantime, millions continue to live in extremely bad conditions. Relatively simple measures could make a large difference to their indoor environment, health and wellbeing. One such measure is discussed here, in a new variation on a retrofit concept that was discussed and tested some years ago by one of the pioneers of passive climatisation in buildings, Baruch Givoni (Givoni 2011). A simple retrofit solution is described in order to reduce the internal heat gain caused by the uninsulated metal and similar roofs that are typical of low income buildings. The EPSRC-funded ELITH program (1), with lead partner Warwick University, UK, concluded in mid-2016. This research proposal was considered of particular relevance for our two African partner countries, Uganda and Tanzania, where large rural and peri-urban populations live in such dwellings. The proposal remains to be tested and evaluated in the field.
Solar Air-conditioning Systems Impact on the Built Environment – A Thermodynamic Approach
1. Introduction Energy consumption in European domestic and tertiary sectors represents about 40% of the annual EU-15 final energy use and about a third of greenhouse gas emissions. Among these, about two-thirds are concentrated in residential sector, the remaining part in commercial building. The household sector represents about 70% of total energy consumption in buildings sector [1]. During the last few decades energy consumption for cooling has increased dramatically in most European countries. The main reasons for the increasing energy demand for summer airconditioning are the increased thermal loads, increased living standards and comfort demands in conjunction with architectural characteristics and trends. During the summer the demand for electricity in Greece increases due to the extensive use of heating ventilation and air conditioning systems, which increase the peak electric load, causing major problems in the electric supply. In the current practice, air conditioning is exclusively based in the use of electric energy, while the use of solar energy is limited at heating of domestic hot water and in limited applications for space heating and fewer for cooling. It has been estimated that the total energy consumption in Greece, in 2003, for central air conditioning systems was 2909 GWh/y [2], whereas the per capita consumption was estimated at 371 KWh/ y [3]. The extensive use of electrically driven compression cooling equipment is responsible for an increase of greenhouse gases emissions, due to the energy production or to the leakage of the cooling fluids; intensifying the cycle of climate change. The latter is of great significance, especially in the case of public buildings. The energy behavior of the public buildings in Greece varies according to the building's age and its structural components [4]. Public buildings that have been constructed until 1940 are characterized by heavy structural components, lack of central heating, high energy consumption rates and satisfactory conditions of thermal comfort especially during the summer months. The majority of public buildings in Greece have been constructed during the period 1940-1980 (before 1973); these constructions are characterized by reinforced concrete, lack of thermal insulation, they usually have a central heating system, high energy consumption rates and medium thermal comfort. The energy behavior of the public buildings in Greece has significantly been improved, during the past 20 years, mainly due to the use of thermal insulation. In 1980 the buildings adsorbed 22% of total energy consumption; while in 1994 the absorbed energy came up to 30.9% [5].This increase can be attributed to the increase in the use of electrical energy. Taken into consideration the fact that the energy consumption in public buildings will be greater than 50 kWh/ m 2 , coming up to a total of 250 kWh/ m 2 ; it is obvious the need for rational energy use so as to avoid the economic as well as environmental impacts. For this reason the development of trendsetting technologies for reliable, affordable and environmentally friendly energy is vital. The use of solar energy to drive cooling cycles for space conditioning of most buildings constitutes 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 solar incidence. Solar cooling systems have the advantage of using harmless working fluids such as water, or solutions of certain salts. They are energy efficient and environmentally safe. They can be used, either as stand-alone systems or with conventional air conditioning, to improve the indoor air –quality of all types of buildings. The main goal is to utilize " zero emission " technologies to reduce energy consumption and CO 2 emissions.
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Economy and parsimony in the consumption of energy resources are becoming a part of common sense in practically all countries, although the effective implementation of energy efficiency policies still has a long way to go. The energy demand for residential buildings is one of the most significant energy sinks. We focus our analysis on one of the most energy-consuming systems of residential buildings located in regions of tropical climate, which are cooling systems. We evaluate to which degree the integration of thermal energy storage (TES) and photovoltaic (PV) systems helps to approach an annual net zero energy building (NZEB) configuration, aiming to find a feasible solution in the direction of energy efficiency in buildings. To conduct the simulations, an Energy Efficiency Analysis Framework (EEAF) is proposed. A literature review unveiled a potential knowledge gap about the optimization of the ASHRAE operational modes (full storage load, load leveled, and demand limiting) for ai...