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Learn how to make your own solar water heater with spare parts from the kabbadiwalla. It may well cost more than the claimed amount but it will teach you how simple the technology really is. Of course, if you want to store the water, you’ll have to make, or invest in, an insulated tank.
And don’t forget to read the comments at the bottom of the post (on the Instructables site, not this one) for more low-cost ideas.
Go To: Solar Thermal Water Heater For Less Than Five Dollars
I was designing an ovoid conference room the other day and trying to remember the string and pin method of drawing an ellipse because, at some stage, I’ll have to mark it out on site. Headed off to the world’s favourite search engine and after a couple of mis-hits, landed on Math Open Reference which shows a simple animation of how to do it. The site also has tons of other simple geometry stuff. A definite bookmark.
Go to :: Math Open Reference
And while I was searching for more information on Sodium Acetate for the previous post on sealing concrete, I came across a way of simulating the natural patina that appears on rocks that have been exposed to air – especially desert air.
What interested me about this information was that you can obtain different colours by varying the dilution and mixture of different metal sulphates and acetates.
Go to :: http://www.patentstorm.us/patents/5308646-description.html [LINK BROKEN]
Researchers in Jordan seem to have identified Sodium Acetate as a simple, cheap and ecologically friendly way of sealing concrete which is not my favourite material for various reasons – one of them being that the steel bars inside are prone to corrosion. This might be, at least partially, an answer to that problem.
The actual report in PDF format [~2.5 MB] via: SciGuy and: Treehugger