Household cooling device is designed to run without electricity

Household cooling device is designed to run without electricity
(Tech Xplore)—Nice. A cooler that runs without electricity. It is not a gadget targeted at hiking professionals or vacationers roosting in pods in the States and Europe; this one is a device designed for people who have no electricity at all in their homes.

A video was posted last month telling the story of the Eco-Cooler. Grameen Intel employees volunteered and teamed up with Grey Dhaka (Bangladesh wing of Grey, communications company), the Eco-Cooler project.

(For those not sure if "Intel" has any connection with the Intel, the answer is yes. Grameen Intel describes itself as a social business information technology company, formed as a collaboration between Intel Corporation and Grameen Trust. Intel Capital and Grameen Trust made investments to create Grameen Intel Social Business and they are the shareholders of the company.)

The video opens in Daulatdia, Rajbari. where many people live without any electricity at all. Many rural homes in Bangladesh are made with corrugated tin.

"We are a flood-prone nation, so in rural Bangladesh, most people build their homes out of tin, instead of mud," said Jaiyyanul Huq in The Observers.

In the summer temps reach 45 Celsius. Staying inside homes cannot beat the heat. The heat beats the residents. People find greater comfort resting just outside their homes. Huq in The Observers described the heat as like being in a sauna in the Sahara.

The video shows a man walking and collecting soda and water bottles. Those are a key component for the Eco-Cooler. The bottles are cut in half and put into a grid.

"As hot air passes through, the bottle neck compresses and cools the air."

The cooler is said to drop temperatures by up to 5° Celsius. (Not a lot in numbers but for a mother fanning a baby in the indoor heat, that drop may feel better.)

Jaiyyanul Huq wrote how Ashis Paul came up with the idea. "Paul started thinking about ways to bring relief to these people. He was turning it over in his mind when one day, he overheard his daughter's physics tutor explaining to her how gas cools when it expands quickly. Ashis has an 'inventor' mentality and he's always been fascinated by science. So, he started experimenting. He told us about his idea of making an air-conditioner out of plastic bottles."

The video said the idea was being adopted in villages across the country. According to Grey, "With the help of the Grameen Intel employees, the Eco-Coolers have been installed in villages in Nilphamari, Daulatdia, Paturia, Modonhati and Khaleya across Bangladesh."

India TV said according to reports the coolers have been installed in almost 25,000 homes.

"After initial tests, blueprints of the Eco-Cooler were put up online for everyone to download for free," said Syed Gousul Alam Shaon, Managing Partner and Chief Creative Officer at Grey Dhaka.

Is there a copyright involved? "We urge everyone to download the how-to guide, made available on this website and make their own version of the Eco-Cooler. There are no copyrights," stated the web site for EcoCooler.

In response to seeing the video on YouTube, numerous reader comments included remarks that said the idea was not effective.

Comments ranged from saying the concept sounded like nonsense to those who expressed doubt and one reader suggested a placebo effect may have been at work making the residents feel better. Some comments were from those who tried out the idea and said it worked for them.

Matthew Humphries, senior editor,, weighed in: "It sounds too good to be true, but it exists and is in growing use across the country of its origin: Bangladesh, where 70% or residents live in tin huts without power."

Humphries provided an explanation of how this is constructed:

"To make an Eco-Cooler you take a piece of board cut to the size of a window on your house. Then drill holes in the board big enough to push a plastic neck through. Gather some old plastic bottles and cut the bottoms off, then slide the neck of each bottle through the holes and secure them with the cap. Do this until the board is full. Hang the board on the window..."

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Jun 10, 2016
It does sound like nonsense, where does the heat go? I suppose wind could provide the work needed to transfer heat, but air flowing through a grid does not provide any avenue for the heat to escape. Is it absorbed into the bottles? That doesn't make sense, that heat would be transmitted inside by the air flow. Reflected back outside? How? Transferred into another dimension? I don't think so.

Jun 10, 2016
Actually the air is compressed just as described.

Jun 10, 2016
I could imagine that when the air is compressed (slightly) as it enters the neck of the bottle it will slightly rise in temp. If the board was able to conduct some of that heat away from the neck then theoretically it would work. Refrigerators work on a very similar principle. However the compression in this invention must be very small and the conduction of heat away from the neck is also very weak. I cant think that it would be effective.

Jun 10, 2016
In principle this *might* work... but I find it almost impossible to believe that it actually has a measurable impact. If this provided even 10W of cooling I would be impressed. Cooling a room noticeably would require >500W.

That's not to say it can't be improved though. The idea seems sound - it should be possible to get fairly high power levels with the right design.

Jun 10, 2016
Someone needs to instrument one of these with sensors to figure out where the heat energy is going, if it is indeed going somewhere.

Jun 10, 2016
If there is no work then no cooling can occur. To cool a gas via compression the gas is first compressed. This process heats the gas and requires work. The gas then passes through a heat exchanger which results is a compressed. This gas can be expander and is therefore cooled.

You can't get something for nothing, so in this case how much energy can you get from ambient air when it is compresses by the air blowing by wind forced circulation. Remember that the air will "see" the bottle neck as a restriction. Even if you 'close your eyes' to this, as noted in earlier comments the air 'forced' through the bottle neck must somehow be cooled before it is expanded into the room. The pressure drops in this process must be extremely low, if not vanishing, and consequently, and cooling must be vanishing as well.

It would be interesting to see if someone actually follows the above commenter's suggestion to instrument the 'gadget'.

Jun 11, 2016
I thought about the fluid flow being the cause. As air moves from the bottle into its neck, its speed increases, so as per Bernoulli's law its static pressure decreases. Now if the volume doesn't change, the temperature will also decrease.

There are problems however. A 5 degrees temp drop corresponds to a pressure drop of about 13 mmHg, which corresponds to an air speed of about 50 m/s or 180 km/h or 114 mph, which is too much for the people inside.

Another possible cooling effect is the Joule-Thomson effect. But that works well at incoming air pressures of tens of atmospheres, which then drop at 1 atmosphere.

Or maybe the cause is somewhere else: the bottles improve the air flow through the house and then by water evaporation the temperature drops. But then why doesn't it work the same by simply opening the window?

Jun 11, 2016
Put the word prefix "Eco" in front of just about anything and the gullible among us automatically assume the device is a boon to mankind and works as stated.

Jun 12, 2016
"Transferred into another dimension? I don't think so."

Check out a de-laval nozzle for reference. There is a way for a converging-diverging nozzle to turn heat into linear motion of the air over a pressure differential - in other words, the air becomes cooled because part of the thermal energy turns into linear kinetic energy.

Jun 12, 2016
For a cubic meter of air to drop down 5 K in temperature, it needs to lose 1.005 kJ x 5 K x 1.127 kg = 5.66 kJ of energy and gain as much in velocity, assuming the heat doesn't go anywhere else.

But that would mean the air coming out of the bottle was moving at nearly 100 m/s so that can't be the reason either.

The only reasonable explaination is that the bottles somehow help the ventilation by bringing cooler air from the outside to the inside of the hut. They may work as a kind of air ram valve that turns the house into an air pump where air flows one way through the house - in through the window and out through the door - rather than just fluttering back and forth with the wind and not carrying away the heat.

You have to remember, the air outside is not that hot. The air inside the house is, because it's stagnant and the tin house collects heat.

Jun 12, 2016
Ooops, really bad thinking. On their website, Intel compares the air when you blow with lips open, versus pursed. The first delivers air from your lungs, nice and warm. The second mixes in a large batch of surrounding air (this is called ENTRAINING), if that surrounding air is cooler than your lungs, the jet will be cooler. If the proposed system experiences a wind, it will create lots of little jets at the window, that will move air inside the home and add a little from outside. In no way is this a cooler, but more of a fan with limited ingress of outside air compared to open window.

Jun 13, 2016
In order to provide cool air for a warmer air source, energy must to be removed from the air source. Period. Can't get something from nothing. The cooling effect from blowing air onto your skin results from water evaporation. The skin feels cooler because evaporating the water requires energy.

The entire rational for the report is based on a flawed context.

Jun 17, 2016
What if the effect is given by water evaporation inside the air? Maybe water contained in air is not just vapor, but also small droplets, even at subsaturation conditions. Maybe by slightly changing the pressure, as happens when air speed increases, water starts evaporating, thus absorbing heat and cooling the air. It's just a hypothesis.

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