For every person using air conditioning or air cooling, there are many more who can’t afford either and have to suffer extreme discomfort when their houses turn into virtual ovens in the summer, resulting in sickness and even death. The following contains the photos and the results of the experiment on an extremely simple roof cooling system. All it involves is to cover the roof during the day by a low emissivity cover and withdrawing it at night, exposing the roof for cooling by radiation to the sky. That is all.
DAY TIME
- From Sunup to Sundown, this flexible cover, with a very shiny bottom, is drawn over the slab.
- It shades the slab, while its low emissivity {0.01) due to the shiny surface prevents any radiant heating of the slab.
- So even though the slab gains some heat from the ambient air, and its bottom still remains below 30 Deg. C., at least five degrees below the body.
- So it feels cool enough to be free of heat stress.
NIGHT TIME
- During the night, the cover is retracted and the slab remains open to the sky.
- This allows radiant heat transfer from the slab to surface that is 30 Deg C. to the sky that can be minus 40 to minus 60 Deg. C depending on haze and clouds.
- The rate depends on the difference in the fourth powers of their absolute temperatures and the emissivity of the slab (.85). So the slab bottom cools down to 27 Deg. C.
- This rate is about 100 watts/Sq. Mtr.
Results
- The shade prevents heating during the day and promotes cooling by sky radiation at night.
- The combined effect maintains the slab bottom temperature to be always below 30 Deg. C. that is over five deg rees below the body,
- Since there is no heat radiation from the roof, it is quite comfortable.
Next Step
- A 2.5 M x 2.5 M frame supported by four vertical pillars is covered by a plastic tarpaulin.
- A shiny film is pasted to its underside.
- A timer operates a motor that opens and closes the cover at the proper time.
- An architectural college has taken it up as a Master’s Project.
Conclusion
By combining the modern method of pre-cooling the ventilation air with the zero energy Indian method of cooling the structure, we can get the best of both the worlds and achieve “Comfort” Ventilation and also save energy since less air is needed as it is cooler and the M.R.T. Is lower.
Surendra H. Shah
Innovator
Age: 90 years
(Patented in the USA, Indian patent pending).
