Alternatives to air-conditioning: policies, design, technologies, behaviours

Far from being a panacea, air-conditioning is shown to create social, environmental and economic problems. Alternatives to air-conditioning are identified as a key means of reducing energy demand and carbon emissions, improving resilience to heat, and providing a healthy indoor environment. These alternatives are more than a technological issue and help to reframe coolth as an attribute and not a commodity. This editorial introduces the themes and individual papers in this special issue. It explores the implications of these alternative solutions across a range of issues: health and wellbeing; air quality; heat stress; technical/design solutions; economics and equity; climate change; social expectations and practices; policy and regulation; supply chain and procurement; education and training. Recommendations for change involve policy and regulation, construction industry business models, redefining the design decision process, improving performance and feedback, and updating workforce skills and capabilities

Characterization of High Porous PZT Piezoelectric Ceramics by different Techniques

Ultimate properties of a porous ceramic is highly process dependent. In this study, prevalent porous ceramics fabrication methods (Freeze casting, Foam reticulation and Burnable Plastic Sphere (BURPS) method) have been compared by fabricating the porous lead zirconate titanate (PZT) based piezoelectric ceramics. Field Emission Scanning electron microscopy (FESEM) studies were carried out to study the pore size and distribution of the ceramics. Hydrostatic co-efficients increased tremendously on incorporation of porosity which led to Hydrostatic Figure of Merit of 7480 in Foam reticulation samples (porosity 86%). The three dimensionally interconnected networks in the freeze casted samples led to lowest acoustic impedance (6 MRayls) despite not having the lowest density

Capturing the views of architects about building performance simulation to be used during design processes

In the past 30 years, much effort has been directed to make building performance simulation become inherent in architectural practice. Anecdotal evidence however shows that it still a long way for this goal to be achieved. This paper presents the outcome of a survey conducted in Australia, India, the US and the UK, to investigate difficulties that architects have to overcome in their day-to-day practices and identify the reasons why using building performance simulation, regardless how friendly the tools are, is still not and may never be in the mainstream of their practices. Based on the survey, the paper proposes a number of recommendations to overcome this challenge in line with IBPSA’s vision on bridging the gap between research and practic

Thermally Comfortable Affordable Housing: A Study on Residential Building Code In India

On an average, India has more than 3000 Cooling Degree Days (CDD). The multifamily public housing being constructed under India’s Prime Minister Awas Yojana (PMAY) is aimed at providing formal housing to the society’s Economic Weaker Section (EWS). It is essential that this housing delivers thermally comfortable in-doors to the occupants. This study mapped the design and construction practices followed under PMAY Urban (PMAY-U) against India’s Residential Energy Building Code, Eco Niwas Samhita (ENS). The metric prescribed in ENS is Residential Envelope Transmittance Value (RETV). For 80 PMAY-U projects, information related to spatial design, and walling assemblies was collated. 30 projects were short-listed for detailed analysis. The RETV for selected projects was calculated. The analysis demonstrated that walling assemblies and technologies having a lower thermal transmittance value (U-value) resulted in meeting the ENS prescribed RETV numbers, hence, code compliance. The study further extended to assess the energy performance of the housing unit by exploring the change in walling assemblies. The change in thermally comfortable hours were reported in the range of 4145 and 6034, and Energy Performance Index (EPI) of the dwelling units were reported between 64 and 68 kWh/m2/year for the various walling assemblies

Capturing the views of architects about building performance simulation to be used during design processes

In the past 30 years, much effort has been directed to make building performance simulation become inherent in architectural practice. Anecdotal evidence however shows that it still a long way for this goal to be achieved. This paper presents the outcome of a survey conducted in Australia, India, the US and the UK, to investigate difficulties that architects have to overcome in their day-to-day practices and identify the reasons why using building performance simulation, regardless how friendly the tools are, is still not and may never be in the mainstream of their practices. Based on the survey, the paper proposes a number of recommendations to overcome this challenge in line with IBPSA’s vision on bridging the gap between research and practic

Investigating optimum cooling set point temperature and air velocity for thermal comfort and energy conservation in mixed-mode buildings in India

In warm and hot climates, ceiling fans and/or air conditioners (ACs) are used to maintain thermal comfort. Ceiling fans provide air movement near the skin, which enhances the evaporation of sweat, reduces heat stress, and enhances thermal comfort. This is also called the cooling effect. However, AC usage behaviour and the effects of elevated air speed through the use of ceiling fans on indoor operative temperature during AC usage are not widely studied. This study investigated the optimum AC (cooling) set point temperature and air velocity necessary for maintaining thermal comfort while achieving energy conservation, in mixed-mode buildings in India, through field studies by using used custom-built Internet of Things (IOT) devices. In the current study, the results indicate a 79% probability that comfort conditions can be maintained by achieving a temperature drop of 3K. If this drop can be achieved, as much as possible, through passive measures, the duration of AC operation and its energy consumption are reduced, at least by 67.5 and 58.4%, respectively. During the air-conditioned period, there is a possibility that the cooing effect is reduced because of increase in operative temperature due to ceiling fan operation. Therefore, the optimum solution is to maintain the highest AC set point and minimum fan speed setting that are acceptable

Transient three-dimensional CFD modelling of ceiling fans

Ceiling fans have been used for decades as a means of providing thermal comfort in tropical countries such as India. However, recent years have witnessed a significant increase in the use of air conditioning as a means to achieve comfort, and therefore in the total energy consumption and related CO2 emissions. Ceiling fans are still viable options to limit use of air conditioners or in combination with air conditioners without compromising on thermal comfort and still achieving energy savings. Ceiling fans generate nonuniform velocity profiles, and therefore relatively non-uniform thermal environments, whose characteristics may be tough to analyse with simple modelling methods. This issue can be investigated using CFD. However, to date, there are few works on ceiling fans, CFD and thermal comfort. More accurate models are therefore required to predict their performance. The research presented in this paper aimed to develop and validate a three-dimensional transient implicit CFD model of a typical ceiling fan available in India by comparing simulation results obtained using different URANS turbulence models with measured data collected in controlled environment. The results highlight that this ceiling fan model is able to replicate the predominant characteristics of the air flow generated by the fan such as the meandering plume and the local fine free shear layers. The best results are achieved when the SST k-u turbulence model is used, with 83% of the simulated values being within the error bars of the respective measured value

A new methodological approach for estimating energy savings due to air movement in mixed mode buildings

In recent years, there has been a proliferation of air-conditioning in both residential and commercial buildings in India. Mixed mode buildings are buildings in which a combination of air-conditioning and natural ventilation is used to provide comfortable indoor environments. These buildings are likely to be less energy consuming than fully air-conditioned buildings, and further energy savings can be achieved by using air movement to increase the cooling set-point temperature without jeopardizing occupants’ thermal comfort. The aim of this research was to develop and test on a typical Indian apartment a methodology to quantify these energy savings using dynamic thermal simulations. The core of this method is the definition of the cooling set-point, which varies monthly according to the ASHRAE 55-2013 adaptive model. The results show that the annual energy demand for space cooling can be reduced by as much as up to 70 percent by using air motion devices. Moreover, the indoor thermal conditions during the occupied periods predicted by the model are closer to the values measured in field studies in India

Guidelines to bridge the gap between adaptive thermal comfort theory and building design and operation practice

Adaptive thermal comfort guidelines have been developed within the work of Annex 69: “Strategy and practice of adaptive thermal comfort in low energy buildings”. The guidelines have been established based on a framework for adopting adaptive thermal comfort principles in building design and operation developed by the authors. The guidelines target building practitioners, addressing the critical interrelated role building planners, building operators and occupants play. A successful adaptive thermal comfort design, in which design for human thermal adaptation is foreseen, planned, and carefully embedded in the design and operation intent, is based on broad knowledge and understanding of the multiple quantifiable and non-quantifiable factors influencing human perception, as well as human building interaction. Adaptive building design follows a user-centric integrated design approach and therefore it is critical to consider the occupants’ and the operators’ role in buildings already in the design phase. This paper focuses on three main challenges identified earlier and how these are addressed in the guidelines, i.e. i) updating prevailing knowledge about human thermophysiology and adaptation, ii) developing a procedure for design of adaptive opportunities, and iii) providing guidance for operational planning and operation of adaptive buildings. The challenge for future research remains to assess the magnitude of how specific design decisions affect particular adaptive mechanisms

Design charts to assist on the sizing of natural ventilation for cooling residential apartments in India

This paper presents four design charts (DC) to work as a simplified, easy-to-use and cost-effective tool to assist architects and building designers on sizing openings to deliver natural ventilation (NV) for cooling. The DC are derived from analytical techniques for four NV design systems based either on buoyancy-driven or wind-driven flow. The application of the DC is demonstrated to size NV openings for a bedroom in an apartment located in three Indian cities for two opening size scenarios: ‘business as usual’ (A); and ‘necessary size’ (B) to deliver the desired ventilation rates for cooling. The ventilation rates for cooling found with these DC are compared with outputs from computational fluid dynamics simulations. Findings show that for the earlier design stage the derived DC are effective tools. It is also found that the opening sizes used in scenario A do not deliver the desired NV rates for cooling, whilst the openings for scenario B must be sized separately for each city to be effective.</div