Wind Catchers, traditionally known as Badgirs or Malqafs are Natural Ventilation devices. They have successfully been used in countries like Iran, Egypt, Pakistan, Afghanistan for many years.
This Vernacular Method is being ‘Adapted’ and utilized in various Contemporary Buildings. One such adaptation is the Strategy known as PDEC or ‘Passive Downdraft Evaporative Cooling’.
We use diagrams of the Torrent Research Centre, Ahmedabad; to discuss this technique.
3main Principlesare at play-
Evaporative Cooling – Water Sprays Cool the Warm Air Entering the tower
Cool Air Sinks – This Moisture Induced Air is Heavier and thus Sinks
Warm Air Rises – Warm Air in the rooms is Lighter and Rises
This sets up a Loop of Air.
The Project achieves a temperature drop of upto 13oC. When the outdoors sizzle at close to 44oC, the indoors are at around 30oC1. The Building incurred Additional Civil Costs of 13% for its Strategies. However, Energy savings helped payback the investment in less than 1 year2!
How do You feel about this Vernacular ‘Adaptation’ for Contemporary Buildings? Have you come across other such Projects?
What are your thoughts on the Practicality of this Technology? Let us know!
Look out next week, for the Pros | Cons of this Strategy in – Vernacular to Contemporary | PDEC | An ‘Adaptation’ – Part II
Following our case study Article and Video – Drip Irrigation in the City, we received expert response from a Ranchi, India based Civil Engineer, with almost 40 years’ experience.
Based on this discussion, and feedback, this week’s article outlines possible issues that may arise with use of this technology in Residential colonies.
In Case study 1 (original Case Study -Residence A), the Balcony A in question lies adjacent to a plumbing Shaft A, containing supply water pipes to the house. Thus, the plumber can easily provide a water connection (Source for the Drip Irrigation System) from this shaft to the balcony.
However, in Case Study 2 (Alternative
Scenario – Residence B),
the positioning of shafts is different. The Shaft B in the house (Residence B) is placed far from the Balcony. This makes it difficult to provide a water source for the Drip
The Shaft C, which offers a more direct route to Balcony B, contains water supply pipes belonging to another flat (Residence C). Thus, the plumber would be unable to draw a connection from this shaft.
Such technology could be Integrated at earlier Design stages in future Residential constructions. Thus, shaft and water supply lines could be planned accordingly, for convenience to Residents and to save Water.
We look forward to more such expert opinions, feedback, comments. These help us move towards further Sustainable Solutions, for our evolving Built and Urban Environments.
An Efficient technique largely used in Greenhouses and Agriculture, could be ‘Adapted’ to serve ‘Emerging’ City Needs – Assist Aging Populations and Address Water Shortages.
Looking at a City Case Study, Details, Pros and Cons.
This week we document Drip Irrigation used for balcony garden irrigation. The Case study is a 1000 sqft. flat dwelling, housing 2 aging persons. Having a large ground garden, while living in a metro city is a luxury most cannot afford. So, many people nurture beautiful balcony gardens. Often aging parents or grandparents may be living alone and looking after these spaces. They may or may not have access to domestic help for daily watering of plants. New developments are often also plagued with water shortages. Tiled balconies can become messy and slippery with pipe or bucket watering, thus posing a danger to aged people living alone.
We thus explore this technology, used in our case study, that may be able to address the above issues. It could remove unnecessary risk and make life a little more convenient for aged people.
The Nuts and Bolts
Looking at 3 main details –
1) Origin – Tap, Tap Connector, Elbow Connector, Main Pipe
2) Route – Main Pipe, Elbow/ Tee/ Straight Connectors
3) Destination – Main Pipe, Feeder Pipe, Stake/Anchor to hold Feeder Pipes in the soil of pots, Drip Emitter
Some advanced kits also include automatic timers for scheduling the watering cycle.
The whole kit could cost between ₹ 300 to above ₹ 7000 (around $4 – $100 depending on company, number of plants)
Pros and Cons
The Pros and Cons are based on feedback for the technology by the owners.
Note: The products utilized by the owners in the Case Study are by a company called CINAGRO™. We are spreading information about the ‘adaptive’ use of this technology to solve important city issues. We however, are NOT endorsing the products/ company in question. You could search for Drip Irrigation Garden online. There are various companies that sell/ install such products.
Hope these details help you make decisions for your homes and the homes of other aging people with similar requirements.
Have you used a similar technology in your projects? Tell us about your experience. Did you face any other issues than the ones described above?
Do you think this ‘Adaptation’ can help address Emerging city needs?
CapitaGreen is a 82,000 sq.m., 43-floor skyscraper in the Central Business District of Singapore1. The Video looks at its design for Sustainable Ventilation.
45 m1 tall Wind-Catchers atop the skyscraper are oriented towards the prevailing wind direction2. Designed to scoop winds at this elevation, they channel air down a core known as the ‘Cool Void’3. Air from the cool void spreads horizontally through the levels, reducing Air-Conditioning loads.
While researching various Passive Strategies and Technologies for the Building Envelope, we came across ‘Cool Roofs‘. We realized that this is a simple, low cost technology with large potential benefits. These include – Energy savings, Reduction of Urban Heat Island Effect and Greenhouse Gas Emissions, enhanced Durability of roofs, and Resilience to extreme heat 1.
Thus, this week’s Article and Video are dedicated to this important idea. The Video 2 , 3 , 4 outlines the Need for Cool Roofs and how they Protect Buildings. In the Article, we cover Initiatives by various parties working in the direction. We also look at some successful Case-Studies that could become models for future developments.
Due to multiple possible benefits, the technology has caught the attention of International actors, Indian central, state and local governments, as well as the Private sector. Their attempt is to use Cool Roofs for large scale Impact at the Building and Urban scales.
The Bureau of Energy Efficiency [(BEE), Government of India, Ministry of Power], has prepared a ‘Cool Roof Design Manual‘ 2 to spread technical information about Cool Roofs for the Composite Climate Zone of India.
A Fact Sheet5 and Issue brief6 have been released by Natural Resources Defense Council (NRDC) and Partners to showcase local projects, and to spread the message, so that action can be scaled up.
Green Building Rating systems like LEED, GRIHA, IGBC need compliance with the Energy Conservation Building Code (ECBC) norms. ECBC specifies minimum cool roof values (reflectance and emittance), for roofs with different slopes 6.
IIIT Hyderabad Cool Roof Calculator – The simulation tool by IIIT Hyderabad, uses a base and design case for testing various roof conditions in certain cities of India. A percentage change in cooling energy can be compared 2, 7.
The above efforts are helping common people as well as experts to understand and utilize Cool Roofs, by providing technical information, tools and answers to common questions. The following examples showcase successes in the field.
Ahmedabad’s Cool Roof Initiative, as part of its ‘Heat Action Plan‘ aims to convert 3000 roofs in 6 zones to Cool Roofs. This is being undertaken by city staff and student volunteers. They are using white lime paint, which costs as little as ₹0.50 per square foot 5.
Hyderabad is also witnessing a Cool Roof Initiative as part of its Building Energy Efficiency Program. The Pilot included 25 city roofs in low income areas. A High-Density Polyethylene (HDPE) cool roof membrane (costing ₹13 per square foot in Hyderabad) was supplied by Dupont as part of their CSR initiative 1.
The Indore and Surat ‘Cool Roof Project‘ is using local success stories to make a case for cool roof policies in the future. The project consists of over 100 households. They are using simple materials such as lime concrete, broken earthen pots, China mosaic tiles 6.
A Joint study was conducted by International Institute of Information Technology, Hyderabad (IIIT) and Lawrence Berkeley National Laboratory (LBNL) on 2 office buildings in Hyderabad. The studies saw a drop of approximately 20°C in Roof surface temperatures after application of cool roof coating 2.
We leave you with the following questions –
Have you used ‘Cool Roofs’ in your Project? Do you know of any projects using ‘Cool Roofs’?
What Benefits have you felt after application of the ‘Cool Roof’ technology?
What Problems did you face?
What kind of Assistance if any, did you receive from the Government or any other organisations?
Let us know! We would love to provide a platform, to showcase your project and spread more useful information.
Jaiswal A, Bhagavatula L, Awasthi A, Sarkar S. Keeping It Cool: Models for City Cool Roof Programs. National Resources Defense Council. https://on.nrdc.org/2jLgLPJ. Published 2018. Accessed November 27, 2018.
International Institute of Information Technology Hyderabad, Administrative Staff College of India, Indian Institute of Public Health Gandhinagar, Mahila Housing SEWA Trust. Keeping It Cool: How Cool Roofs Programs Protect People, Save Energy and Fight Climate Change.; 2018. https://on.nrdc.org/2FIxYas. Accessed November 27, 2018.
International Institute of Information Technology Hyderabad, Administrative Staff College of India, Indian Institute of Public Health Gandhinagar, Mahila Housing SEWA Trust. Issue Brief – Cool Roofs: Protecting Local Communities and Saving Energy.; 2018. http://www.phfi.org. Accessed November 27, 2018.
“The harmony of natural law reveals an intelligence of such superiority that, compared with it, all the systematic thinking and acting of human beings is an utterly insignificant reflection.”
Contemplating this powerful quote by Einstein could send chills down your spine. Our insignificance in the face of Nature’s power, begs us to show more humility. Nature doesn’t fear our walls, and everyday Climate related calamities should teach us better. It is ultimately in all of our favor, to Build with Nature, instead of withstanding it!
Following this chain of thought, today we look at Integration of Built with Water. Such a synergy with Water has positive effects on Micro-Climate and Energy Loads.
However, insects can be attracted to areas of vegetation and water. While all insects are not harmful they may not always be welcome in an urban setting.
Let’s look at some ways to address this issue-
1) Deeper water could prevent mosquitoes, since larvae prefer shallow water bodies of less than 2 feet
2) Natural pest Predators like Dragonflies are garden heroes
3) Select Plant Species that repel pests – Lavender, Citronella Grass, Marigolds
Building functions can be zoned according to the ventilation strategy for effective management and energy conservation. This is seen in Akshay Urja Bhavan1 where spaces are divided into zones according to setpoints – Apex, Controlled and Passive. Only around 12% of the area is air-conditioned. Mist cooling systems are used for the Controlled and Passive zones.
Buildings should preferably be oriented between 0o and 30o with respect to the prevailing wind direction2. The building form can incorporate courtyards or verandahs (transitions zones between inside and outside) for increased ventilation and thermal comfort. These features temper down the harshness of the exterior environment, providing shade and cool breezes in summer.
A building depth of around 15 meters or less would enable Natural Ventilation and Daylighting. This is an assumption based on our research of many buildings by WOHA applying their Unit thick Principle. Some buildings may not be able to achieve less depth due to larger functions such as Industrial labs.
Solution| Fragmentation of Form – Such buildings could employ courtyards or atriums to break the overall form, thus enabling light to penetrate or air to flow better. (eg. Cleantech One) Fragmentation of form is also seen in Indira Paryavaran Bhavan3, where two North-South oriented blocks are separated by a centrally running public spine.
Location, Sizing, Area – The location and size of windows, should take into account the wind direction and the ‘Living Zone’. The total area of openings should be a minimum of 30% of floor area2.
Window to Wall Ratio – The Window to wall ratio (WWR) should fall between 20-40% for Commercial buildings. In any case, it should not exceed 60%4.
Operable windows – The windows should preferably be operable with a staggered alignment. Operable windows may present certain issues. In the case of hotels for example, people might leave windows open when the air-conditioning is on, which would affect energy costs. Operable windows could also have safety implications.
Solution 1| Sensors – Some hotels install sensors that automatically shut off air-conditioning when windows are opened.
Solution 2| Individual Project Detailing – Safety concerns would need to be addressed in projects individually, through railing design details, selective openings or special locking mechanisms.
A 16 km (once campus completed) tunnel network of Air Earth tunnels, will be running 4 m below the ground in NIIT University, Neemrana Campus. Surface temperature and seasonal variations do not penetrate below this depth, keeping air temperature constant throughout the year. Fans will pull cool air through these tunnels. This would then be taken through precipitators to eliminate dust and would be supplied to the building through ducts. The result! – Pleasant 25oC temperatures indoors, without the use of air-conditioning, when temperatures outside are nearing 50oC5.
(ii) Wind Tower
These are utilized widely in desert climates (eg. Iran, Saudi Arabia). Tall towers are built with openings facing the prevailing wind direction. The openings are narrow and the towers may contain misters or other moisture creating devices. As the tall tower catches winds, air moves down the tower, cooling on the way and is used in the building. A similar system using Shower Towers is used at DPR Office, Phoenix.
(iii) Stack effect
According to the principle, warm air from an area would rise, making space for cooler air. This would generate a loop of air circulation. This effect can be seen at building scale or even at room level. In Indira Paryavaran Bhavan, the central courtyard spine coupled with well placed building punctures, generates the ‘Stack Effect’ at the building scale. The IRRAD Building, although using air-conditioning, is utilizing a similar principle. The vents are placed near the floor, instead of the ceiling. Cool air enters the room at a lower level and it rises as it become warm6.
(iv) Displacement Ventilation
In Neemrana University, the cool air from ducts is introduced at lower levels in rooms. This pushes warm air in the room upwards, which is then exhausted through openings in higher parts of the spaces. It is similar to the stack effect, but here an additional push is being provided by the introduced cool air, to get the circulation loop going.
(v) Wind Scoops
Wind Scoops like the one used in CapitaGreen can channel air into a ‘Cool Void’. This brings cool air from a higher altitude, deeper into a high-rise building. Air flow, such as that channeled by CapitaGreen maybe blocked by surrounding buildings in a different scenario.
Solution| City Planning and Studies– This leads to the need for city planning and studies like Computational Fluid Dynamics (CFD) to ensure these strategies are workable at a city level. This would help avoid “dead air zones”, wind canyons and other undesirable wind related events. This becomes especially important in city centers with greater density and multiple high-rise structures.
(vi) Solar Chimney
The DPR Phoenix Regional Headquarters in Pheonix, Arizona use solar chimneys to exhaust warm air from the building.
(vii) Evaporative cooling
This technique utilizes the latent energy used to convert liquid to gas. As water evaporates, its phase changes, which results in a cooling effect. This technique has been used widely in desert coolers.
Last week we were in conversation with Sustainability Professional Steven Lee from Malaysia. He is currently Principal at Edisi Hijau Sdn Bhd, Kuala Lumpur, Ipoh. Steven has been working with the IT industry for over 20 years, before making the move to Green Technology in 2007. (You could connect with him here – LinkedIn, Twitter)
Our discussion started with the post on Passive Strategies used in CapitaGreen, Singapore and the viability of such strategies in other projects and countries.
Today, we sum up points from this discussion and others that we think could be useful to our readers. We will focus on 3 Essential Passive Strategies – Natural Ventilation, Integration with Greens & Water and Daylighting. This part starts with Natural Ventilation.
Buildings account for 33% of the total electricity consumption in India. (Domestic 24%, Commercial 9%)1. Of this, HVAC is one of the highest loads accounting for almost 50-60%2.
What needs to be done and effects ?
Our effort should be to reduce the need for Air-conditioning, to help reduce energy loads. Less AC use or using air-conditioning at higher setpoints, could result in saving energy. In Residential scenarios for example, after 22oC, every 1oC higher set point equals 3-5% less energy use3.
Through design, planning, passive strategies like Natural Ventilation, integration with greens and water, we can increase thermal comfort. Thus people will want to use less air-conditioning and this will result in energy use reduction.
Climate is one of the chief factors determining the feasibility of Natural Ventilation. For example, Natural Ventilation is quite effective in Moderate climates and it may provide considerable relief in Hot and Humid conditions4. However, it could bring discomfort and dust in Hot and Dry Climates. Cold Climates also need protection from chilling exterior winds and might need enclosed conditions.
(ii) Wind direction
The wind direction determines design and viability of Natural Ventilation. Wind rose diagrams are used to understand prevailing directions, frequency, speed and other factors related to wind conditions in any particular area.
(iii) Thermal Comfort and Perception
Thermal Comfort is a complex, often subjective issue determined by multiple factors. Before the advent of AC, buildings were designed according to climate and context. People enjoyed the benefits of fresh air. Now, many occupants prefer fully air conditioned spaces since they have become used to such an environment. There might be instances when the AC is too cold for comfort, but this has become the norm. Enclosed buildings behave like greenhouses2, which then need air-conditioning to cool them down. So, the need is not only to improve thermal comfort , but also address people’s perception related to it. To address this complex issue, we could look at the following solutions.
Solution 1 | Custom Thermal Comfort Models– Countries could develop customized thermal comfort guidelines for Design. An example is the ‘Indian Adaptive Comfort Model’ developed by CEPT university. This is part of theGRIHA manual5and is adapted to Indian local conditions. For example, it provides Indoor Operative temperature values for all cities in India. These are setpoints which are required as per standards to achieve thermal comfort. They are to be monitored during the operation of the building. These models could help optimize setpoints and engage in better AC design.
Solution 2| Hybrid systems – DPR Office in Phoenix, Arizona uses a hybrid cooling system. They have special High Velocity Low Speed (HVLS) fans and operable windows. Cooling is provided by moist air through Shower Towers on the facade. There is also a Solar Chimney exhausting warm air. Only when the conditions are too extreme, they switch on the air-conditioning6. A hybrid cooling systemis also being designed for the new School of Design and Environment building NZEB in the National University of Singapore7. The NZEB at CEPT University is planning to utilize optimized natural ventilation coupled with a radiant cooling system2.
Solution 3 | Common areas could be Naturally Ventilated, (fully or partially) for starters. Since occupants spend lesser time in spaces like corridors, washrooms, lobbies, parking – such efforts might help the acclimatization process. An example can be seen inParkRoyalHotel @ Pickering.
(iv) Pollution andLocation
Natural Ventilation may not be possible if the outside air is polluted. Pollution could be due to traffic, dust from a construction site or other harmful substances, such as emissions from a factory.
Solution 1 | Location – Sensitive functions like schools or hospitals would ideally be located away from such areas.
Solution 2 | Natural Filters/ Barriers – If this is not possible, window opening design could be clubbed with strategies like Vegetation or Earth mounds, to act as noise barriers or to filter pollution.
This is Segment 4 of our Chain of posts focused on ‘Energy @ the Building Scale’.
[Extension of Part 4/5: The Red System (Energy), Singapore – Published: 28th May 2018]
Skyville@Dawson is a 111,106 sq.m., 48-storey1 public housing project by WOHA Architects in Queenstown, Singapore. It is one of two Build-To-Order (BTO) projects commissioned by Singapore’s Housing Development Board (HDB), as part of their “Remaking Our Heartland” initiative (the other being SkyTerrace@Dawson by SCDA Architects)4. This “housing-in-a-park” concept would show transferability in future projects and towns like – Waterway Terraces, Bidadari, Punggol Northshore, Tampines North6. It is the first housing development to be awarded the GreenMark Platinum Rating10. Skyville@Dawson’s Sustainable Design features including Passive Strategies are elaborated below-
(i) The Building is placed with its longer facades facing the North-South9 directions. This reduces exposure to the East and West directions, that are normally difficult to shade.
Clustering and Modules
(i) 8 apartments in plan(as seen in Plan diagrams above), surround a courtyard. This cluster is repeated 2 more times, to create 3 sets of apartments enclosing courtyards. This configuration also provides self-shading, especially from low angle rays from the East and West directions (as seen in the Shadow Studies above).
(ii) In Elevation, 12 clusters form villages, each comprising of 80 apartments.
(iii) The apartment layouts are column and beam free4. This provides the possibility of 3 layouts for residents – reducing wastage, allowing flexibility for multiple functions, family size and the future.
(iv) For standardization, efficiency and to reduce wastage, only 5 window types2 have been used in the entire development.
(v) The design uses precast and prefabricated10 elements to avoid errors and reduce wastage. This feature could also contribute towards LEED BD+C v4 Credit – Construction and Demolition waste management.
(i) The individual apartments are approximately 11 meters across in width, thus applying the Unit Thick Principle. Apartments also have openings in all directions. They are thus naturally ventilated and day lit, reducing artificial cooling and lighting costs.
Breathability – Horizontal Air Movement
(i) The clustering arrangement around courtyards, and the repetition of this module linearly, enables horizontal air circulation.
(ii) Common areas (Lobbies, Corridors, Staircases) and Apartments are naturally ventilated. Many units have not installed Air-conditioning3.
Breathability – Vertical Air Movement
(i) With minimal obstructions and the creation of Canyon like spaces, air moves vertically through the towers – accentuating the breezy atmosphere. The interaction of this air with greenery from sky gardens at intermediate levels, cools this air through evapotranspiration.
(i) ‘Sky Terraces’7 are located every 12 floors. These are designed as community spaces, where people can collect to interact with neighbors or simply visit to relax and enjoy the lush greenery.
(ii) A ‘Sky Park’7 on the roof has planters, hedges, and beautiful city views. Photovoltaics3 power the common area lighting.
Site Integration with Green and Blue
(i) A 150 m long bio-swale (gently sloping ditch with specific plants) filters and treats site stormwater before discharging it into the city drainage system5. Another example of a bio-swale – water treatment and recycling loop can be seen in Kampung Admirality.
(ii) The site is an ungated3 community, with Public Parks and Amenities that cater to the residents as well as the general public.
(i) Monsoon windows8 on the facade can be kept open during rains, thus providing cool breeze without wind-blown rain entering the home. A similar more advanced Monsoon Window design is utilized in another high-rise residential building – 1 Moulmein Rise, Singapore.
(ii) The walls on the facade have horizontal and vertical sunbreakers5. Balconies or horizontal ledges9 are used to provide shading for openings.
(iii) Double-height verandas10 on the ground level provide pleasant public spaces overlooking the parks.
That’s all for today! We hope you enjoyed this segment. As always, we would love to hear your thoughts, suggestions, queries, opinions.
See you next week.
Credits: Graphics : Selected graphics are produced as part of a team project for M.Sc. Integrated Sustainable Design at National University of Singapore (Building Semester – Stage 1 – Complex Living Systems). Group Members – Gajender Kumar Sharma, Aditi Bisen, Huang Hongbo, Zhao Yanming Text: Aditi Bisen
Last week in Part I, we introduced a Vernacular to Contemporary Adaptation – PDEC – Passive Downdraft Evaporative Cooling. A Vernacular ventilation strategy – Wind Catchers, which is being adapted to Contemporary buildings. We also looked at diagrams explaining the 3 main principles in this Adaptation.
This week we look at Prosand Consof this technology for Contemporary use.
1) Energy Saving
a) Decrease cooling demand
Temperature Drops of upto 13oC can be achieved1. When the outdoors sizzle at close to 44oC, the indoors are at around 30oC.
Night Ventilation using PDEC towers decreases cooling demand and operating time of the primary cooling system the following day3.
b) Less Fluctuations
Indoor Temperature fluctuations of around 3-4oC can be seen over 24 hours, when the outside Temperature fluctuations are between 14-17oC1.
2) Cost/ Applicability
a) Short Payback Period
Electrical Consumption savings helped achieve payback of additional capital cost in less than 1 year for the Torrent Research Centre, Ahmedabad.1
b) Can be used in new / existing buildings with simple construction elements at relatively low cost.
a) Applicable in areas without wind
As Air movement is created by momentum transfer from water to air and density difference; the technology can be applicable in areas without wind 4, 5.
4) Cleaner Air
a) Evaporative Cooling
The air is cleaned during the evaporative cooling process 6.
The cooling capacity maybe insufficient in certain cases, and could need conventional cooling as well 4.
2) Cost/ Applicability
a) High Water Consumption6.
b) Short life of Water Pads
3) Climate Dependency
a) Works best in Hot & Dry Conditions
The technology maybe most effective in hot and dry conditions. However, buildings can be designed to adapt to other conditions and seasons. For example, in the Torrent Research Centre, the system operates normally in the dry season. In the monsoons, the water spray is not used, whereas in Winters, the openings to the rooms and shafts can be controlled (opened or closed) by the occupants 1, 4, 6.
How do You feel about this Vernacular ‘Adaptation’ for Contemporary Buildings?
Have you come across other such Adaptations?
What are your thoughts on the Practicality of this Technology? Let us know!
Paanchal JB, Mehta N. “A Review on Design of Passive Down Draft Evaporative Cooling in Commercial building.” 2017;3(2). https://bit.ly/2B33ZoS.
Bowman, N. T., Eppel, H., Lomas, K. J., Robinson, D., and Cook, M. J. “Passive Downdraught Evaporative Cooling I. Concept and Precedents.” Indoor + built environment 9.5 (2000):284-290.
Etzion, Y., Pearlmutter, D., Erell, E., and Meir, I. A. “Adaptive architecture: Integrating low-energy technologies for climate control in the desert.” Automation in construction 6.5 (1997):417-425.Ford, B. “Passive downdraught evaporative cooling: principles and practice.” Environmental Design. Architectural Research Quarterly 5, Cambridge University Press (2001) : 271-280.
Givoni, B. “Performance of the Shower Cooling Tower in Different Climates.” Renewable Energy, 10, 2/3 (1997):173-178.