A C Mathur

I have been making various sorts of mobiles for over 35 years now.

I learnt the art of balancing forks and spoons over the edges of cups and glasses at home.

When I was living as a bachelor in Calcutta, I found a book on Calder's mobiles at one of the book fairs there. Reading that book, I got more seriously into making mobiles.

My understanding of his mobiles has increased greatly nowadays.

Previously, there was a class of mobiles that he made where the parts did not have freedom to move in relationship to each other.

In July 2009, Microsoft Research released Project Tuva, based on the famed Messenger Lectures presented at Cornell University in 1964 by the late Richard Feynman, an American physicist and California Institute of Technology (Caltech) professor who shared the Nobel Prize in Physics in 1965 for his contributions to the development of quantum electrodynamics. Bill Gates, Microsoft chairman, made the lectures freely available to the public to encourage people to learn about science via a Silverlight-enhanced video player that presents the original, BBC-recorded videos of the seven physics lectures. The videos are searchable and include linked transcripts, notes, and interactive extras, originally including academic commentary on the first of the lectures.

Now commentary on all seven lectures has been added by Robert Jaffe, Jane and Otto Morningstar Professor of Physics at the Massachusetts Institute of Technology (MIT). Jaffe first met Feynman early in his academic career.

Engineering students will find some great resources for reading and writing about the topic.

What is wrong with the existing Solar cookers?

Summary

1. They are made for the wrong audience.
2. They are too expensive compared to the alternative devices already available with families to cook.
3. They use the wrong technology.

Details

1. They are made for the wrong audience.
• For a family, they cannot cook food for the members who leave the home in the morning, say by 8 AM or 9 AM. In poor families where all the members go out for work, there is not much that a solar cooker can do.
• They can cook lunch for about 180 to 200 days in a year for stay behind members.
• If the Solar cookers are combined with hay-cookers, they can serve at least one hot dish for dinner. This requires that a cooking member should be home after 3 PM.
2. They are too expensive compared to the alternative devices already available with families to cook.
• A poor family that might benefit from not paying for fuel has its cooker as five bricks and a pot on the top. Often the pot is a tin that held 15 kgs of oil and is sold in the second hand market at a throw away price. It uses wood ( sticks, broken wooden crates, branches etc) as its fuel. The cooking arrangement of bricks and pot costs no more than ₹ 25 and wood is almost free. It works on all days and gives a hot meal by 8AM. At this price point it is not possible to design a solar cooker that can compete with the alternative. At least I am not making any effort to compete in this market.
• A more middle class family where the mother stays at home ( and does not earn an income) and the family has a gas stove that cooks all the food whenever required can be characterized as having a device that cost between ₹ 600 to ₹ 900 and a monthly fuel bill of ₹ 150 to ₹ 200 a month. For it to cook with a solar cooker that works about half the time, the solar cooker needs to be designed to cost between ₹ 250 to ₹ 3,000. The cost of ₹ 250 represents an ideal value for money as it is just below the proportionate capital cost of the device that is already with the house wife. Paying more than ₹ 3,000 for a device means that the house hold is purchasing something costing 5 times the existing device to get a utility for one meal on 180 days out of 360. Roughly the cost of fuel saved balances the interest locked up in the device. For this market, we will try to make a solar cooker trying to keep the price as close to ₹ 250 as possible.
• NB The present parabolic solar cookers in the Indian market cost anywhere from ₹ 10,000 to ₹ 8,500. Their high costs spring from the costly plastic (Mylar equivalent) reflecting surfaces that they use.