I talked about a light that utilizes the power of gravity to light up a few days back. This flashlight is a bit similar in a way that, it also doesn’t need any batteries. But the underlying mechanism it uses, is completely different.
The winner of this year’s Google Science Fair, in the age group of 15-16, was a 15-year-old girl from Canada, Ann Makosinski. In her project she created a flashlight that, instead of batteries, uses our body heat to light up. She calls it “Hollow Flashlight”
The flashlight uses 4 Peltier tiles to convert the temperature difference (between body and room temperatures) into energy. One side of the tiles is heated by our body heat and the other side is at room temperature. This temperature difference creates electricity using the Thermoelectric effect. The tiles used for this light need a minimum of 5 degree difference of temperature to work.
Peltier tiles utilize thermoelectric effect to convert temperature difference into electricity. When there is a enough temperature difference, charge carriers move from hot area to the colder area. This separation of charges builds up a potential difference across the height of the tile. This potential difference can be used up for various things. In this case, it was used to light up LEDs.
Advantages: The amount of potential difference produced depends on the material. Peltier tiles are great because they are compact and they do not use any moving parts. Elimination of any moving parts eliminates wear and tear. They last long and do not need a lot of maintainance. However, their efficiency is not so great. So, they are used only where long life is essential.
The Voyager space probe and other deep space probes, where long life is of prime importance, use Thermoelectric generators (another image). The heat there is produced by a radioactive isotope. Implanted pacemakers which require long life also use it as a source of energy. All of them work utilizing the same effect – thermoelectric effect. The eco-fan, a wood stove fan, also uses the same effect in a very creative way.
Thermoelectric Generators have a very interesting history.
A $5 lamp that lights up using gravity can be used without electricity or batteries, over and over again with no running costs. Impressive enough? There is more.
A British company, after working for 4 years on this project, with an aim to replace kerosene lamps, started an internet fundraising campaign on Indiegogo and successfully raised about 7 times more than what they had aimed for – aimed for raising a fund of $55,000 and ended up raising $399,590. They had invented the Gravity Light.
Gravity light uses the force of gravity to light up – a free, completely reliable and totally unlimited source of energy. For it to start, the user is supposed to lift up a hanging weight of about 10 kg. And there! As the bag full of dirt, stones or sand starts coming down slowly, it lights up an LED light. The weight keeps coming down for about 30 minutes and then it has to be raised again. It generated a very minuscule amount of electricity and manages to give out a much brighter light than a kerosene lamp.
The energy generated from it can also be used to charge batteries, charge phones, run a radios etc, with attached accessories.
Interestingly, the company has plans to develop various other gravity powered solutions. So, in the future, we might probably see a way to reach the internet without batteries or electricity.
Other interesting lighting ideas:
] [Water + Bleach lamp
] [Algae + CO2 lamp
During a period when electricity was only a thing for the Gods, around 400 B.C.E., in the hot-arid deserts of Iran where temperatures touched 40 degree centigrade, ancient engineers had found a way to keep their ice from melting. Two thousand years back, a cold storage facility was being used. The impressive thing about it – it was clean and sustainable technology.
What are these?
Yakhchals, or ice pits of ancient Persia were the huge mounds (buildings hollow from the inside), which made it possible for Persians to store away the ice for summers, meat, dairy products, other food items and chilled frozen Faloodeh for the palace. Beside treats for the palace, the method of preserving ice was so professional yet simple that even the poor could afford it.
Structure and Working
The structure of these buildings above the ground is a large mud brick dome, often rising to about 60 feet in height. Below it are large underground empty spaces, up to 5000 cubic meter in volume. This space had access to wind catch and often contained a system of wind-catchers that could easily bring temperatures inside the space down to frigid levels in summer days. The structures were built so well that many still remain standing.
Working: The massive insulation built into the walls (due to the use of a special mixture of sand, clay, egg whites, lime, goat hair, and ash) and the continuous cooling waters that spiralled down its side kept the ice frozen throughout the summer by evaporative cooling (just like those mist fans). They also had a trench at the bottom to catch water from the molten ice and to refreeze it during the cold desert nights. The ice was then broken up and moved to rooms deep in the ground. As more water ran into the trench the process was repeated.
Geography: These were built in the areas that had suitable condition for producing natural ice or places where there was feasibility of water freezing during the cold nights.
Major architectural elements:
- Shading wall – To avoid direct exposure to sunlight and to let the structure remain cool in the shade.
- Provisional pool – To supply water for evaporative cooling to take place.
- and Ice reservoir – To keep the cycle going. Freeze > Melt > Refreeze at night and so on…
The end of Yakhchal (reasons)
- Since the advent of electricity-guzzling freezers and air conditioners, unfortunately, the use of these architectural wonders has been considered as foolishness. This is probably the reason no Yakhchals are being used for cold storage anymore.
- Desert storms, caused a lot of erosion to these structures, especially to the ones that were isolated in the desert regions.
- Since Yakhchal’s ice formed in the open it was prone to combining with dust and resulted in contamination. That was another reason it wasn’t considered as a choice useful enough for modern purposes.
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