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Ellen McCallie's Carriacou diary: Sun and sea

Updated Monday 28th January 2008

Sun and sea are plentiful on Carriacou – find out how the team were able to harness the energy from solar power in order to distill seawater.

Day 1

This is a very straightforward challenge. Jonathan immediately had a strategy, so we could set to work quickly.

A parabola is a special shape. I learnt all about it in math, but never had used it practically. This was a very practical use – to focus the sun’s rays at one point so the kettle gets really hot and evaporates water, which we will collect and cool in a tube.

Jonathan is making nice drawings to explain the parabola. What I have to say is that it was quite funny watching us do the calculations. As it turns out we both have a bit of difficulty getting numbers in and out of our heads. If I see a big number and try to write it down, I do fine, but if someone asks me to say the number out loud, the digits get all mixed up in my head. For example, 395.87 might come out 539.78. This makes a big difference to your answer! Jonathan has slightly different troubles, but the end result was two people who love and use math regularly, but who fight to keep the digits straight. It was a nightmare until we just kept quiet and did our calculations in silence, checking our answers against each other’s.

I never thought I’d ever smash a mirror by choice. We smashed many of them to put on the parabola to focus the Sun’s rays. The prototype we made worked so well. You could feel the difference in heat as your hand moved toward the focus. I kept forgetting to use one of the homemade thermometers to measure the temperature differences.

I’m still not sure about the resin we tapped from the bursera (Bursera simaruba) tree – the one that smelled like incense, in programme 4. The wet season isn’t here full force yet, so the tree may not have enough fluid to make sap. I doubt I’ll get more than just an ooze, but I’d hate to be wrong and lose any, hence the little cup made from the calabash (Cresentia cujete) fruit shell. This is really important for Kathy as she needs a sealant to make the lightbulb completely waterproof. As it turned out, we got enough sap and it worked!

Day 2

We cooked the shells so the calcium carbonate (limestone) in the shells was oxidized to calcium oxide (quicklime). We then mixed the calcium oxide with water to produce calcium hyrodoxide (slaked lime). Calcium oxide and water react vigorously together and produce heat when they react to form calcium hydroxide. We also added inert material (sand and clay) to finish the mortar.

Day 3

I am glad we collected water yesterday, because all we’ve gotten today was rain. The rest of today was a bit odd. We’d finished our challenge, so all we could do was help others as needed. I cut a lot of branches for fuel wood. We never know what we’ll need for the next programme, but I’ve learned that almost every chemical reaction requires heat. We have two sources: the sun and fire. Fire is more controllable, so we’ve all sawn a lot of logs. I think about all the people around the world that use fuel wood daily for cooking. If I had been born in another time or even now, but in another place, my main jobs may have been collecting fuel wood and water. This was common in Timor, Indonesia where I did my graduate work. It is also common in most of Africa, sections of India, in the Amazon and all over Southeast Asia. Basically, most of the developing world uses fuel wood. War torn areas turn to fuel wood as well. It’s tough to blame people for deforestation when they are cutting wood to make food…

It will take political, economic and social change for this type of deforestation to stop. The other type of deforestation, clear cutting and selective logging for production of materials for the developing world, is a whole different issue, however. We don’t need old growth or tropical forest wood for survival. We exploit these resources by 'demanding' low prices for press board, lumber, chopsticks, toothpicks and, in some cases, paper. Indonesia’s amazing Dipterocarp forests are being obliterated for such items. I’d rather see us in the developed world pay a lot more attention to where the wood is coming from and paying a lot more for these products. This way there would be more habitat for orangutans (literally, "people of the forest" in Indonesian), yellow, blue and pink kingfishers, and the rest of the plants, animals and people who live in the forest.

 

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