climates of Nairobi

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By: shamim_entezari (119 month(s) ago)

that was soooooo useful for me , thanks a lot

By: cheguevara (130 month(s) ago)

in this presentation using weather tool software climates of the city nairobi has been analyzed in details. the information you will come across in this short presentation is about wind analysis using windrose diagrams rain charts temperature and much more

Presentation Transcript

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By Qaisar Shamshad 2009-m.arch.01 Energy Efficient Architecture

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Nairobi Nairobi, city in south central Kenya, the capital of the country, located just south of the equator. The city’s name is derived from a Masai word meaning “place of cool waters.” Area=680 sq km average altitude =1675 m (5495 ft) above sea level

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Site Features The city center—and the area around it to the east and south—is a relatively flat plain, while the area to the west and north is hilly. Hilly area Dame In the residential areas situated some 300 feet(100 meters) higher than the city centre temperatures are 1° or 2° lower.

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Climates Nairobi’s altitude produces relatively cool temperatures despite the city’s proximity to the equator. The average annual temperature is 17º C (63º F). Nairobi’s average annual rainfall is 790 mm (31 in), with most of the rain falling in two rainy seasons, March to May and October to December. Contemporary Issues Water shortages Power outrages

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These graphs show that more than 50% energy is consumed in Building industry this leads to the urgent considerations to minimize this energy by utilizing different techniques.

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Energy consumption in different sectors and key factors those influence energy consumption

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Prevailing Wind Throughout the year 50% of the total wind flows from North-East to South-West

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Monthly analysis

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Prevailing Wind in Summer %age of Prevailing Wind in Summer

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Prevailing Wind in Autumn % of Prevailing Wind in Autumn

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Prevailing Wind in Winter % of Prevailing Wind in Winter

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Prevailing Wind in Spring % of Prevailing Wind in Spring

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Variations in Wind Speed in different seasons summer autumn winter spring summer

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Prevailing Wind Temperature

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For Heavy activities as Gyms, indoor games we may introduce the wind with temperature 15 to 20 For Heavy activities as Gyms, indoor games we may introduce the wind with temperature 15 to 20 For light activities we can use wind with temperature 20 to 25 Summer wind

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Autumn wind Even in Autumn for certain activities we can use the wind with temperature higher than 20 degrees

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Winter wind Cold wind in Winter season may have to be treated using some techniques and then utilized

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Spring wind

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Humidity most of the time in year remains in acceptable range except in dry season that does not last more than few weeks.

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Rains there are two rainy seasons, from mid-March to the end of May ("Long Rains"), and from mid-October to mid-December (the "Short Rains"). The average annual rainfall in Nairobi is about 900m, but the actual amount in any one year may vary from less than 500 mm to more than 1500 mm. The shortage of water may lead us to use different techniques to preserve rain water as Rain water Harvesting. The average rainfall(mm) for each month of the year, based on records for 50 years

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Long Rain Short Rain

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Cloud Cover Study of Cloud Cover becomes a matter of great concern specially when you are using some heating techniques those utilize direct solar gain or solar radiations. In Nairobi few weeks of January and December are cloudy.

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Summery of wind data analysis The main features of the climate are the existence of definite wet and dry seasons, and the absence of any large seasonal change in temperature. For convenience the year can be subdivided into four seasons as follows:- Mid-December to Mid-March: Warm, sunny, dry. Mid- March to May: Main rainy season. June to Mid-October: Cool, rather cloudy, dry. Mid-October to Mid-December Secondary rainy seasons. The only period of the year when the weather can be rather trying is during the hot, dry period shortly before the rains break in March. At this time mid-day temperatures rise to nearly 32°C, the relative humidity may fall to 10%, and a moderately strong easterly wind tends to raise the dust.

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Results of the Wind Analysis To make maximum use of air the appropriate orientation

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Temperature and Radiation analysis

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Climate classification The prevailing climates in Nairobi is Moderate with little variation throughout the year. Nairobi Climates

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Daily variations Although Nairobi is situated quite close to the Equator , its altitude of about 5,500 feet (1700 meters) results in enjoying an equable as opposed to a tropical climate, with temperatures neither uncomfortably low at night nor high at day times

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Temperature differences between Day and Night 10 to 15 Degrees variations Though seasonal variations are quiet small the daily range of temperature is quite large, averaging about 10° in May and 15° in February. The human body quickly becomes sensitive to small seasonal changes of temperature, and many people in Nairobi welcomes a fire in their homes during the evenings, especially in the months of July and August. In certain areas spaces are heated using Passive Heating Techniques.

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Seasonal variations in temperature winter summer autumn spring summer

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Analysis of Annual Dry Bulb Temperature with respect to Comfort range These analysis will help us in finding the requirements for heating or cooling. What do we need? Heating or cooling..

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Dry Bulb Temperature in January What do we need in this particular month? Heating or cooling..

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Dry Bulb Temperature in February

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Hottest day Dry Bulb Temperature in March

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Dry Bulb Temperature in April

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Dry Bulb Temperature in May

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Dry Bulb Temperature in Jun

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Dry Bulb Temperature in July

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Coldest day Dry Bulb Temperature in August

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Dry Bulb Temperature in Sep

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Dry Bulb Temperature in Oct

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Dry Bulb Temperature in Nov

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Dry Bulb Temperature in December

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Because of its proximity to equators we can avail both the sides North South Sun path and radiations study

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Solar intensity study Maximum intensity area This study effectively leads us to find out the direction from where we can avail best in terms of SOLAR GAIN

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Orientation adjustment to make for the available radiations Whereas the software shows the best orientation on North-West direction. But aft all the analysis I have come to realize that I will need heating most of the time. This can be easily complimented by Direct solar gain so the optimal orientation is as shown.

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Minimum Max radiations Low moderate Rise

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Solar intensity study with respect to building We can orient the building to make maximum of the available radiations specifically when requirements for the Heating load increases.

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From these analysis we can deduce these results: Average temperature throughout the year is 17 degrees. Most of the time we need Heating. (this will lead to the use of some heating techniques) Useable wind temperature and direction have been figured out. Seasons identification and requirements of the Heating load in different seasons and in different months have been calculated Amount of solar radiations and how far can we use them to make for the Heating requirements is calculated Finding the most suitable heating techniques

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TECHNIQUES First of all lets make some minute adjustments in the envelope of the building and see the results. In that we will see The existing comfortable range Change in comfortable range by chaining the %age of glazing area Change in comfortable range by applying different heating techniques.

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Step-1 Existing comfortable range

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Increase in comfortable range by using PASSIVE SOLAR HEATING Note the glazing ratio 20%

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EFFECTS OF GLAZZING ON THE COMFORTABLE RANGE IN NAIROBI Increase in comfortable range by using PASSIVE SOLAR HEATING and 30% GLAZING Note the glazing ratio 30%

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RECOMMENDED TECHNIQUE PASSIVE SOLAR HEATING Passive solar heating refers to the use of direct solar radiation to heat a space in winter. This can be done using a direct-gain system, in which sunlight passes through a transparent aperture directly into the habitable space, or indirectly where a separate solar collector is used and the heat transferred to the space via a medium. As Black Attic So the recommended techniques are Direct solar gain Black attic

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Increase in comfortable percentage by Passive Solar Heating

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Direct Solar Gain By orienting the building in a direction from where we may avail maximum radiation

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Black Attic Heat is collected in the Black Attic in the form of Hot air and Thermal Mass which is utilized as per require.

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