Passive Downdraught Evaporative Cooling Research Articles

DESIGN AND OPTIMIZATION OF A COST-EFFECTIVE NET-ZERO ENERGY MOSQUE LOCATED IN A HOT AND DRY CLIMATE

ABSTRACT This research paper presents a comprehensive analysis to develop an energy-efficient and net-zero-energy (NZE) model for a proposed hypothetical mosque model located in Riyadh, Saudi Arabia. The study employs a sequential optimization analysis using BEopt software (Building Energy Optimization Tool) to explore various energy conservation measures (ECMs) from three main categories: HVAC, lighting, and building envelope. The ECMs are evaluated based on energy savings and life-cycle cost, with the most cost-effective options selected for the proposed energy-efficient design package. Furthermore, a passive downdraught evaporative cooling (PDEC) system is introduced as a passive cooling strategy to further reduce the cooling energy consumption. Computational fluid dynamics (CFD) analysis is utilized to optimize the airflow around the building and PDEC tower, determining the optimal PDEC dimensions for enhanced ventilation performance. The PDEC system is found to contribute 12% to cooling energy savings, which further enhances the energy efficiency of the proposed mosque. A rooftop solar PV system is incorporated into the optimal energy-efficient design to achieve a NZE mosque. The results demonstrate that the NZE model achieves 80% energy savings, with the remaining 20% offset by the solar PV system. Moreover, life-cycle cost analysis reveals that the NZE model offers the lowest cost, making it the most cost-effective design option. This research provides valuable insights into designing sustainable mosques in hot and dry climates, such as Riyadh, offering a comprehensive solution to significantly reduce energy end-use and promote sustainable building practices.

Passive cooling and thermal comfort performance of Passive Downdraught Evaporative Cooling (PDEC) towers in a Saudi library: An on-site study

In the hot arid climate of Saudi Arabia, where air conditioning, primarily fueled by fossil fuels, accounts for a significant portion of energy consumption, the implementation of Passive Downdraught Evaporative Cooling (PDEC) towers presents a sustainable solution. This study conducts an extensive evaluation of PDEC towers in a public library, focusing on their effectiveness in reducing reliance on conventional cooling and enhancing thermal comfort. Through detailed field measurements, the study examines the influence of wind speed on the towers' cooling performance, correlating it with internal environmental conditions. The research extends to a comparative analysis of two prominent thermal comfort models: the Predicted Mean Vote (PMV) and the Adaptive Thermal Comfort (ATC) model. Findings indicate a notable interaction between wind speed and indoor air temperature, where increased wind speeds correspond to higher indoor temperatures. Despite this, the PDEC towers demonstrate a significant reduction in temperature, maintaining cooling effectiveness between 70 % and 75 %. The comparative study of thermal comfort models reveals that the ATC model provides a more relevant assessment of comfort levels in naturally ventilated spaces, with 71 % of the recorded temperatures falling within the comfortable range during the monitoring period. The research highlights the PDEC tower's potential in delivering effective passive cooling, adaptable to wind speed changes, and contributing to a sustainable and energy-efficient building environment in hot arid climates.

Integrating a passive downdraught evaporative cooling tower into a Saudi house - The impact of climatic conditions on PDEC performance

The Kingdom of Saudi Arabia (KSA) generates the most electricity of any country in the Gulf region, and virtually all that electricity is produced by the burning of fossil fuels - natural gas and crude oil. The residential sector accounts for about 50% of the total electricity demand in the Kingdom, and around two-thirds of that electricity consumption is used for air conditioning. As the Kingdom transitions away from its reliance on fossil fuels, reducing air conditioning energy demand in dwellings becomes a key objective. Passive cooling systems can significantly reduce cooling energy loads for buildings while maintaining thermal comfort. This study investigated the potential of integrating a passive downdraught evaporative cooling (PDEC) tower into a typical Saudi Arabian villa. A computational model of a spray PDEC tower was developed in IES-VE software and calibrated against field data. Then, an actual Saudi villa was monitored, modelled, and validated before a PDEC tower was digitally integrated into the villa. Finally, the villa and its PDEC digital twin were used to conduct a series of parametric analyses to determine the PDEC performance in different rooms and cooling energy consumption in the villa as functions of wind speed and direction. The research found that, counterintuitively, higher wind speeds reduced the effectiveness of the PDEC system to cool rooms in the villa and that wind direction also played a role in the degree of cooling experienced in different villa spaces. In the summer season, the results indicated that the total villa energy consumption was approximately 32,415 kWh in the base case, with cooling energy representing 88% of the total energy used (28,337 kWh). The integration of the PDEC tower resulted in a reduction of approximately 22% in cooling energy consumption, from 28,337 kWh to 22,032 kWh, while the PDEC was operational continuously throughout the day.

Numerical Analysis of Building Cooling Using New Passive Downdraught Evaporative Tower Configuration in an Arid Climate

Building energy consumption in hot arid climates is dominated by air conditioning use. Therefore, using passive cooling methods could reduce this demand, improve resource efficiency, and decrease carbon emissions. In this study, an innovative configuration of a passive downdraught evaporative cooling (PDEC) tower is investigated numerically. The governing equations are solved using the finite element method (FEM), and the effects of inlet velocity (0.5 m·s−1 ≤ uin ≤ 3 m·s−1) and temperature (35 °C ≤ Tin ≤ 45 °C) on the fluid structure, temperature field, and relative humidity are studied for three cases related to the position of the air outlet. The flow is considered as turbulent, and the building walls and the tower are assumed to be thermally well insulated. The PDEC tower is equipped with two vertical isotropic saturated porous layers. The results revealed that the inlet velocity and temperature play an essential role in the quality of the indoor temperature. In fact, the temperature can be reduced by about 7 degrees, and the relative humidity can be enhanced by 9% for lower inlet velocities.

Analysis of the Performance of a Passive Downdraught Evaporative Cooling System Driven by Solar Chimneys in a Residential Building by Using an Experimentally Validated TRNSYS Model

Natural ventilation, combined with a passive cooling system, can provide significant energy savings in the refrigeration of indoor spaces. The performance of these systems is highly dependent on outdoor climatic conditions. The objective of this study was to analyse the feasibility of a passive, downdraught, evaporative cooling system driven by solar chimneys in different climatic zones by using an experimentally validated simulation tool. This tool combined a ventilation model and a thermal model of the dwelling in which an empirical model of a direct evaporative system made of plastic mesh was implemented. For experimental validation of the combined model, sensors were installed in the dwelling and calibrated in the laboratory. The combined model was applied to Spanish and European cities with different climates. In the simulation, values of cooling energy per volume of air ranging between 0.53 Wh/m3 and 0.79 Wh/m3 were obtained for Alicante (hot climate with moderate humidity) and Madrid (hot and dry climate), respectively. In these locations, medium and high applicability was obtained, respectively, in comparison with Burgos (cold climate with moderate humidity) and Bilbao (cold and humid climate), which were low. The evaluation of the reference building in each location allowed establishing a classification in terms of performance, comfort and applicability for each climate.

Design of a Passive Downdraught Evaporative Cooling Windcatcher (PDEC-WC) System for Greenhouses in Hot Climates

A windcatcher is a wind-driven natural ventilation system that catches the prevailing wind to bring fresh airflow into the building and remove existing stale air. This technology recently regained attention and is increasingly being employed in buildings for passive ventilation and cooling. The combination of windcatchers and evaporative cooling has the potential to reduce the amount of energy required to ventilate and cool a greenhouse in warm and hot climates. This study examined a greenhouse incorporated with a passive downdraught evaporative cooling windcatcher (PDEC-WC) system using Computational Fluid Dynamics (CFD), validated with experimental data. Different hot ambient conditions of temperature (30–45 °C) and relative humidity (15–45%) were considered. The study explored the influence of different spray heights, layouts, cone angles and mass flow rates on indoor temperature and humidity. The average error between measurements and simulated results was 5.4% for the greenhouse model and 4.6% for the evaporative spray model. Based on the results and set conditions, the system was able to reduce the air temperature by up to 13.3 °C and to increase relative humidity by 54%. The study also assessed the influence of neighbouring structures or other greenhouses that influence the flow distribution at the ventilation openings. The study showed that the windcatcher ventilation system provided higher airflow rates as compared to cross-flow ventilation when other structures surrounded the greenhouse.

A parametric analysis of the influence of wind speed and direction on the thermal comfort performance of a Passive Downdraught Evaporative Cooling (PDEC) system – field measurements from a Saudi Arabian library

Building energy consumption in the desert climate of Saudi Arabia is dominated by cooling demand. Electricity for this cooling is generated predominantly from finite fossil fuel reserves. To improve resource efficiency and decrease carbon emissions, reducing this demand by using more passive cooling approaches is desirable. One system is the passive downdraught evaporative cooling (PDEC) tower. PDEC captures hot, dry winds at the top of a tower and then cools the air by passing it through or over water. This cooler air then flows out from the base of the tower into the building. In this study, a PDEC system in a small Saudi public library was monitored for two summer months. A key aim of this study was to investigate the relationship between local wind speed and direction and the performance of the PDEC towers. A thermal comfort analysis investigated the acceptability limits of indoor temperature using the adaptive thermal comfort model. A parametric analysis of the wind effects was conducted by grouping wind data in to ranges of wind speed and direction and then correlating them against environmental conditions in the library. The results indicated that the PDEC towers could deliver significant cooling for library users. However, the towers’ effectiveness was influenced by changes in wind speed, and in a counter intuitive way – stronger wind speeds tended to reduce the tower cooling efficiency.

Passive Downdraught Evaporative Cooling System Integration in Existing Residential Building Typologies: A Case Study

Abstract This paper analyses the integration of a passive downdraught evaporative cooling (PDEC) system in existing residential buildings through a case study, an existing 3-storey building located in a small city near Turin. This study was focused on the technological integration of a PDEC system in residential buildings rather than on its actual applicability, which proved to be very low to Turin's climate. Three main aspects are considered: a) a matrix of PDEC systems integration related to building typologies; b) the results of a laboratory testing in site conditions for evaluating the performance of PDEC systems and correctly dimensioning the evaporative tower; c) the design of an integrated PDEC-Building solution, showing that the described approach can be applied to existing designed buildings.

Direct evaporative passive cooling of building. A comparison amid simplified simulation models based on experimental data

Different simplified simulation models of a Passive Downdraught Evaporative Cooling tower (PDEC) were compared by using experimental data. Among these, a series of tests on a Passive Downdraught Evaporative Cooling tower (PDEC) were carried out at the SyTIn (Systems for Technology Innovation) Laboratory of the Department of Architecture and Design, Politecnico di Torino. In addition, other monitored databases were taken from literature and used as input data for the simplified models. The collected inlet airflow data were used for calculating predicted outlet airflow values by using four equations and a software from literature.The comparison of those outlet airflow data allowed for assessing the effectiveness and the accuracy of the analysed simplified methods, which are also used for simulating the PDEC tower in several dynamic simulation software such as DesignBuilder coupled with EnergyPlus. The presented results could help designers in choosing amid different calculation models.

Review of Passive Downdraught Evaporative Cooling Technique and its Application

Direct evaporative cooling has long been demonstrated as an energy efficient ,cost effective and no CFCs emission means for space cooling in hot dry regions .With the aggravating of the global climate warming and energy crisis, using passive cooling technique will be a good solution . In this paper, the theory of passive downdraught evaporative cooling techniques is analyzed. It is an environmental friendly technique in that it can provide more fresh air than the conventional air-conditionings, and also low cost on operation and no CFCs emission compared with conventional air-conditionings. In this paper, some cases will be introduced .The successful PDEC cases in hot dry areas show weather condition is the key factor for the feasibility using PDEC technique. From the analysis on the weather data in Turpan, which presents a typical climatic character in North-west China , predicts a great feasibility of using PDEC technique in public architectures.

The feasibility of passive downdraught evaporative cooling for high-rise office buildings in Cairo

This article reports on the initial findings of an ongoing study investigating the application of passive downdraught evaporative cooling (PDEC) to high-rise office buildings in Cairo. Two climate analysis methods are utilized to assess the suitability of PDEC to Cairo's climate. The first makes use of Givoni's building bio-climatic charts (BBCCs) while the second adapts the climate suitability analysis method (CSAM) initially developed to assess the potential of a given location for direct ventilative cooling to work with PDEC. PDEC is not a strategy that can readily be incorporated into buildings. The task is even more onerous if tall buildings are involved. The article discusses the means of configuring the high-rise office building to incorporate PDEC along with complementary passive cooling strategies such as night ventilation. A preliminary dynamic thermal simulation is performed on a developed model of the PDEC high-rise office building. The results of the dynamic thermal simulation confirm the validity of the two climate analysis methods but indicate that the effectiveness of PDEC at maintaining thermal comfort is largely dependent on the chosen definition of acceptable comfort conditions. Finally, the validity of the adaptive comfort model in predicting comfort conditions in PDEC buildings is discussed.

Passive downdraught cooling for schools in India: a study on Iira International School in Baroda, Gujarat, India

This study focuses on the design integration of passive downdraught evaporative cooling (PDEC) in a school building in the hot and dry climate of Gujarat, India. It sets out the design process through which different options were evaluated and assessed, and demonstrates that the combination of PDEC with other ‘common sense’ design principles can potentially deliver thermal comfort in school classrooms for most of the year. This is the first time that the application of PDEC to this building type has been evaluated, and indicates significant potential for wider adoption in India. It is anticipated that following construction, post-occupancy evaluation will be undertaken to establish performance in practice.

Passive downdraught evaporative cooling: performance in a prototype house

The design and performance of a passive downdraught evaporative cooling (PDEC) system are reported. This is the first application of this technique for housing in Europe. The system was integrated within a house designed and built by University of Nottingham students for the 2010 Solar Decathlon Europe event in Madrid, Spain. Testing of the thermal performance of the house occurred for a limited period during June 2010. Performance data have demonstrated that the combination of a high-performance building envelope and PDEC provided comfortable conditions inside the house over a period of increasingly warm weather. Estimates of the cooling achieved, based on the measured results, were compared with the energy required by the system to derive an indicative range of coefficient of performance (CoP) values under varying ambient conditions. The results suggest that PDEC can deliver significant energy savings and achieve comfortable thermal conditions without the need for additional mechanical cooling. This technique may therefore have wider relevance to housing in central and southern Spain, and other hot, dry regions of the world. Il est rendu compte de la conception et des performances d'un système de refroidissement passif évaporatif à courant d'air descendant (PDEC). Il s'agit de la première application de cette technique dans le domaine du logement en Europe. Le système a été intégré à une maison conçue et construite par des étudiants de l'Université de Nottingham pour la manifestation Solar Decathlon Europe 2010 qui s'est tenue à Madrid, en Espagne. Les données de performance ont démontré que la combinaison d'une enveloppe de bâtiment haute performance et d'un système PDEC ont assuré des conditions agréables à l'intérieur de la maison sur une période où le temps est devenu de plus en plus chaud. Les estimations quant au refroidissement obtenu, sur la base des résultats mesurés, ont été comparées à l'énergie exigée par le système de façon à déterminer une plage indicative des valeurs du coefficient de performance (CoP) dans différentes conditions ambiantes. Les résultats suggèrent que le PDEC peut assurer d'importantes économies d'énergie et créer des conditions thermiques agréables sans qu'il y ait besoin d'un refroidissement mécanique supplémentaire. Cette technique peut par conséquent présenter un intérêt plus large pour le logement en Espagne centrale et du sud, ainsi que dans les autres régions chaudes et sèches du monde. Mots clés: performance des bâtiments, refroidissement, courant d'air descendant, évaporatif, logement, innovation, passif

REINVENTING TRADITIONAL SYSTEM FOR SUSTAINABLE BUILT ENVIRONMENT: AN OVERVIEW OF PASSIVE DOWNDRAUGHT EVAPORTAIVE COOLING (PDEC) TECHNIQUE FOR ENERGY CONSERVATION

There has been a drastic increase in the use of air conditioning system for cooling the buildings all around the world. Interest in reducing emission of greenhouse gases, caused by fossil fuels to power the cooling requirements of the buildings has stimulated the enthusiasm towards adoption of passive cooling techniques for buildings. Passive systems use non-mechanical methods to maintain a comfortable indoor temperature and are a key factor in mitigating the negative impact of buildings on the environment. Of the different methods to reduce the cooling load, passive cooling of houses and buildings is the most suitable and sustainable method. Passive downdraught evaporative cooling (PDEC) is a passive cooling technique which involves spraying of controlled volumes of microscopic water droplets into hot, dry ambient air, thereby causing it to cool and descend into a required capture zone within a building. This paper is a review paper in which a study of Passive Downdraught Evaporative Cooling (PDEC) as a passive cooling technique for providing thermal comfort and its significance in energy conservation in buildings has been done. The interrelationship between sustainability and cooling needs of buildings has also been discussed. Further two applications of PDEC in contemporary architecture (Torrent Research Centre, Ahmedabad, India and New office building at Catania, Italy) have also been analyzed. Finally a critical analysis of using PDEC system in the buildings has also been done. Key Words: Passive, downdraught, evaporative, cooling, energy conservation.

Passive Down-Draught Evaporative Cooling: Thermal Modelling of an Office Building

Two simulation-based methods of predicting the dynamic thermal performance of non-domestic buildings in hot dry climates, conditioned by Passive Downdraught Evaporative Cooling (PDEC), have been evaluated. In the PDEC system analysed, microscopic droplets of water were evaporated in ambient air and the resulting cool dense air delivered passively, through controlled openings, to occupied areas. The first method predicts the annual hours of PDEC operation, the water usage and the frequency of occurrence of different internal temperatures. The second method, which requires a thermal model with an integrated airflow network, provides insight into the airflow control strategies. Both methods demonstrated that an office building, in Seville, would need support from a mechanical cooling system to remain comfortable. However, the predicted energy use and carbon dioxide production was just 25% of that for a conventional airconditioned building.

Passive downdraught evaporative cooling: principles and practice

Air conditioning is now recognized as a significant factor in global warming and climate change. In the search for alternatives, passive downdraught evaporative cooling (PDEC) is proving to be both technically and economically viable in different parts of the world. Brian Ford describes the principles and current practice of this innovative approach to cooling in the hot dry regions of the world.

Architectural and authentic

‘Linking practice with research’ is both our cover slogan and our objective. arq covers the broad spectrum of architectural endeavour – which comes together in design and buildings – and publishes contributions from both academics and practitioners. Take this issue.First, it covers and considers architectural research in many forms and ways. There's Rem Koolhaas' research on shopping; a pioneering application of a passive environmental system; a competition-winning scheme for new housing; an account of a completely unknown project by Le Corbusier; and an introduction to an alternative to air-conditioning in hot, dry climates. There's also a timely look back towards the beginnings of university-based architectural research in the 1960s; the first English translation of Freyssinet's remarkable essay on the sublime; and a review of Zaha Hadid's recent work and its theoretical base.Second, each of this broad spread of topics is design and practice-related. Most of the authors have academic affiliations but seven are also architects in practice and one is a practising engineer. Just two are architectural historians. Two of the articles – those on the design of the Jersey Archive and on passive downdraught evaporative cooling are interdisciplinary and based on considerations of sustainability. Our letters pages reveal a bias towards practice – but, although all our correspondents are practising architects or engineers, most have strong connections with academia.But this issue takes things a step further: it is the very first arq to carry an article directly based on an architect's drawings and design report – rather than on a piece especially written for publication. ‘From table to basin: St Mary's Island’ (pp. 229–247) is a lightly edited version of a competition-winning entry for a large ‘brownfield’ site in South-East England. For many years, there have been very few competitions of this kind. The Editors felt that Buschow Henley's scheme deserved more coverage than it had enjoyed in the professional press. Our referees agreed and made just one recommendation – that the architects should write a short introduction outlining their theoretical position.In our second issue, in the middle of a lively debate then being conducted in our pages (arq 1/1 and 2), Philip Tabor wrote a leader entitled ‘Design is research: is it?’ He asked whether ‘a design submission, entirely drawn and unaccompanied by text, would be awarded a research degree in architecture? Or, closer to home, would arq’s editor and referees, accept it for publication?’ The answer he concluded, was ‘Probably not.’ Six years on, ‘From table to basin’ represents a shift in editorial policy and a demonstration of the way in which designers can reflect upon their work as research in a way that journalists cannot.

Passive Downdraught Evaporative Cooling

This is the second in a series of four papers that describe a 3-year EU-funded research project into the application of passive downdraught evaporative cooling (PDEC) to non-domestic buildings. The paper describes the use of computational fluid dynamics (CFD) for modelling PDEC. It describes the modelling techniques used and applica tion to investigate the performance of a hypothetical office building in Seville. From the CFD analysis it is con cluded that: (i) CFD is invaluable for analysing the venti lation performance of PDEC buildings, (ii) wind buffering and appropriate aperture sizes are essential to maintain well-regulated flows, and (iii) a top-down ventilation strategy performs equally well in upflowing mode, e.g. during night venting.

Cooling without air conditioning: The Torrent Research Centre, Ahmedabad, India

This paper presents results from the first year of monitoring the performance of a laboratory building in the new 14,000m 2 Torrent Research Centre in Ahmedabad, India. The capital and running costs of air conditioning of non-domestic buildings in northern India are very substantial, while building costs (compared with northern Europe) are low. A cooling technique which maximises reliance on the building fabric and minimises reliance on mechanical equipment is therefore likely to be cost effective. Passive Downdraught Evaporative Cooling (PDEC) represents such a technique. At the Torrent Pharmaceuticals Research Centre in Ahmedabad, PDEC is used to service a number of laboratories and offices within the complex. A central open concourse on three levels allows evaporatively cooled air to be introduced to laboratories and offices at each level and exhausted via perimeter stacks. In the first completed laboratory building the PDEC system has now been working for 12 months. Results from the first summer indicate that internal temperatures are 10–15°C below the peak external air temperature, good air movement is being achieved, and no complaints of discomfort have been received from the staff. The paper describes and illustrates the key features of the building and reports on monitoring undertaken during April - December 1997.

Application of passive downdraught evaporative cooling (PDEC) to non-domestic buildings

The applicability of Passive Downdraught Evaporative Cooling (PDEC) for reducing energy consumption in hot dry climates is reviewed. A new EC Joule project explaining the application of PDEC in non-domestic buildings is described. The building performance assessment methodology which employs dynamic thermal simulation programs for thermal analysis, and computational fluid dynamics (CFD) codes for airflow modelling is discussed. The role which wind tunnel tests and field measurements have in producing improved models is noted. Preliminary results from CFD benchmark trials are presented.