Terry Thomas Cooling is crucial in off-grid villages throughout the developing world: water, refrigeration for vaccines, cooling for Maasai cheese, and even spaces, whether for productive uses of energy (cold chains for fish or agricultural / dairy products) or homes and community spaces. In this webinar, we will hear from several speakers regarding the challenges and opportunities for cooling in off-grid villages. What innovative solutions have they discovered? How can keeping cool improve the lives of people throughout the developing world, particularly the hottest places? As well, what about the environmental impacts of cooling – how can we ensure keeping cool doesn’t cause further global warming? Our webinar series is a little different: each expert will speak for less than 10 minutes and will focus on their on-the-ground experience using photos to tell their story. Speakers: Mr. Philipp Denzinger, Project Manager, Green Cooling Initiative, GIZ Mr. Godwin Osigwe, Founder and CEO, Windair System Ltd. Dr Terry Thomas, Head Development Technology Unit, Engineering Dept, Warwick University Mr. Sam White, Director, Promethean Power Systems More -> http://e4sv.org/events/big-chill-off-grid-cooling-water-refrigeration-spaces/

1. Space-cooling in the Tropics
Notes by Terry Thomas, Warwick University
Notes for Smart Villages/LCEDN Webinar
“The big chill: Off-grid cooling”
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2. Space-cooling in the Tropics
Space cooling is mostly about lowering air temperature
but also includes dehumidification. ‘Work’ and ‘heat’ are
physically different forms of energy: ‘cold’ is an
intermediate form in terms of both difficulty and cost.
What is deemed a ‘comfortable’ or ‘tolerable’
temperature in a room is strongly influenced by the past
experience of its occupants and by their clothing, but the
AC industry has adopted largely N American comfort
limits expressed as a zone on a ‘psychrometric chart’. For
example where temp is between 22C & 28C and relative
humidity between 20% & 80%.
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3. Space-cooling in the Tropics
Temperate-to-tropical technology transfer
Improving the energy efficiency of space heating
has been a major process in temperate countries
since 1970: reducing heat losses, increasing boiler
efficiencies, upgrading standards, regulations and
labelling, & generally progressing from ‘low energy
house’ to ‘passivhaus’ to ‘power-exporting house’.
Is there any corresponding process to be expected
for space cooling in the tropics? Will ‘air-
conditioning’ soon become as normal in the tropics
as winter heating is in temperate zones?
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4. Space-cooling in the Tropics
Space-cooling strategies:
1. Employ architecture, modern or vernacular, that
reduces solar gain, especially through roofs and
through glass
2. In very dry climates use evaporative cooling
3. In climates with big day-night temperature
differences, export indoor heat by night & seal
the building by day: maximise thermal mass,
raise ceilings
4. Increase the indoor airspeed locally above 0.2
m/s via fans or lavish ventilation
5. Use ‘heat pumping’ only as a last resort
6. ‘Import’ cold from lakes and seas.
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5. Space-cooling in the Tropics
Cooling is mainly an urban problem because
• Urban areas are hotter (‘Urban heat island’
effect) by several degrees & rising dangerously
• Urban life is dominantly ‘indoors’
• Urban areas are richer, have better electrical
supply, have copied ‘international’ glass & steel
architecture
• Wind speeds are lower, space for ‘blue-green’
land-use is less
• Air conditioning within close-packed city
buildings raises the outdoor air temperature
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6. Space-cooling in the Tropics
Is space-cooling relevant to tropical villages?
• Urban AC is overloading electrical networks
and thereby depriving rural areas of power
• Neither heat-driven nor diesel-powered space
cooling are affordable in villages: daytime-only
PV-powered AC is just a possibility. Biomass-
powered cooling may become cheaper.
• Vernacular architecture, and use of outdoor
space, can minimise need for space-cooling
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7. Space-cooling in the Tropics
Low-cost cooling
Limit cooling to 1 room and restricted hours
Don’t design for the ‘hottest day ever’ but just
for common hot day conditions – this may save
½ the capital cost and ¼ of the running cost
Maximise shading (trees, 60 cm roof overhang,
east/west-end vegetation, verandahs)
Install ceilings and roof-space ventilation
Have big but closeable windows/shutters
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