Solar Panel

Hello!

So we tested a solar panel yesterday. The solar panel works best if you shine light very close to it (but then it heats up, and silicon doesn't work very well when it's heated up, so this can definitely backfire). It also works best if the light is perpendicular (normal) to the solar panel. Testing was fun because we had several issues (you take readers ACROSS the resistor when you're using a voltmeter, except when there's no resistor, when you just connect the circuit, using the voltmeter as a resistor) (versus you take current by connecting the circuit, which is why you can easily blow out the multimeter if you send too much current through it.), including the light issue.


We also attempted to generate a VI curve, which is shown below.

You can see that the R^2 value isn't very good, and you'll also notice that the voltage axis starts at .350, instead of zero. Unfortunately, going too much above 150 ohms for the resistor made the voltage go down too far to read. I think it would have worked a lot better if we could have collected more points, especially with a lower voltage, so that we could have seen how the drop in efficiency was supposed to work.

Then, we had data from day 2! I unfortunately wasn't there, but my group is wonderful and sent me their data. It is more logical in that there is a value for zero voltage and maximum current. It is also more logical in that you can see how efficient the solar panel is in converting energy... which is actually pretty efficient, according to this graph, since the curve is a concave versus a convex shape!

 

Gretchen's blog also tells me that we tested for "bird poop", and that even covering 3 rows didn't produce much of a change for voltage and current. How awesome!

Monica

Jodie Wu's Talk

Hello!

I attended Jodie Wu's talk, and it was absolutely amazing. As she said, 10% of entrepreneurs make it work, and hers is working.

When she started out talking, my first thought was : I want to be an  entrepreneur! Look at the difference she's making, with her idea under her instruction brought to fruition. She's making it happen.

Then she started talking about all of the challenges-- ie the details of how she got this company to work :). The engineering part isn't even half of the challenge... she had to go into the business world to get sponsors, to learn about when you can sell things, to learn about how to sell things, to learn how to earn trust from people... She has to work in so many different worlds that she (and I) aren't trained in. She has to work with people in the US, who are funding this, and people in developing countries, who are the consumers, and run this operation almost completely on her own with no indication of whether she'd succeed or not. You always hear about the amazing stories of the people who succeed, of which she is one, and yet you don't hear about all of the people who failed. And all of this work went into making a product that it really quite simple from the outside-- an existing technology, a corn scraper, hooked up to a bike. Now, of course, she's going into solar lamps, but SO MUCH WORK to get a corn scraper on a bike to people! It's amazing.

So her talk was really inspiration, but also shows the difference between straight engineering, which can be done in a university (and as she said, often ends in a university), and actually making a difference to people. It seems so sad that the people who are trained to engineer things aren't the people who need the things who are engineered, because I bet it would work much better if the consumers were also the producers. But you make do with what you have... or give education to those consumers! Education's the key to everything :).

So in summary, I'm so impressed by all Jodie Wu has managed to accomplish, and that I don't think I could accomplish, and I've definitely received a new perspective on the difference between doing something in a university setting and doing something that is actually useful, and gets to, the consumer.

Monica

Water Carrying Challenge

Hello!

We got to do a really fun challenge where we tried three different ways of carrying water. In order of easiest to hardest, they were:

Namlo/tumpline (which involves putting the heavy things on your back, connected with a strap across your forehead)

Hipporoller (that's not actually the brand, but you have a cylindrical container with a smaller cylinder hole down the center, where you put a circle of rope that you can pull around)

Bucket-style carrying (how we normally carry buckets), and

Balancing on your head (which is apparently the second most efficient way to carry weights, and if you're really good at it you can do it without hands! I found it hurt though, unlike the rest of them, and I couldn't see anything because it pushed my hat over my eyes.)

We carried the same orange bucket of water for all of these, except for the roller, because you can carry heavier weights in that. The tumpline was definitely the most comfortable, and Prof Banzaert says it's the most efficient way to carry weights, because it basically feels like you're carrying a backpack but that it's supported across your whole body. Your neck gets a little stiff, but overall the best way to carry a bucket of water. Plus, your hands are free and you have a lot of visibility!

The hipporoller was great because you could roll the water. It wasn't so good up or down hills though; up the hills it was really hard to pull, and down the hills it was hard to control. It had great maneuverability though. Some of the problems that we discussed in class was that it wasn't very sanitary (there's no way to clean it or get the water out), the seal will break pretty easily, and it's super expensive to ship.

The bucket-style carrying was pretty awkward because it bangs against your legs, and it makes your arm hurt pretty fast. Not recommended for any sort of long distances.

The head-carrying thing is apparently fine once you get used to it, but it just made my head hurt, and I was very uncomfortable with the amount of pressure being placed there. However, it does leave your hands free if you do it right, and balances the weight over your whole body.

It's unbelievable that many women in developing countries do this for 7 hours a day. Carrying that kind of weight can't be good for you no matter how you do it... though I do hope tump lines become more culturally accessible. Then again, I haven't tried to carrying any kind of weight for more than 2 minutes over any kind of distance. I really need to go have one of these experiences.

Monica

ps, sorry I forgot to post on Thurs :(. I did tell all of my friends about it!