Monday, April 30, 2007

The Ciclovía

From what I´m told by people here in Chorrillos, their mayor is a pretty good one. He hasn´t been seriously accused of corruption, and has been reelected twice. And every once in a while he has a really good idea, but sometimes the execution is a little lacking -- like the Ciclovía (cycle path) that was recently put into place. Traffic is heavy in most parts of the city from dawn to dusk, and lots of bicyclists have been killed by careless drivers. So a separate traffic lane for bicycles could have a big impact on safety and encourage more people to use bicycles, reducing auto traffic.

The Ciclovía in Chorrillos is similar to what a lot of North American cities have done, reserving a space in the public thoroughfares exclusively for bicycles. And in some areas where the road was recently widened, it was implemented very effectively. But for the most part it just consists of a couple of yellow stripes painted on top of whatever was already there. And human nature being what it is, it´s hard to imagine that the mototaxis that have always parked on a certain street, or the pedestrians who fill the sidewalk at one of the busiest bus stops in the city, are going to pay much attention to the new yellow lines. So while there will undoubtedly be a reduction in the number of bicyclists run over by vehicles, there will probably be an increase in the number of pedestrians run over by bicycles. I suppose it´s a good tradeoff.

Tuesday, April 03, 2007

The Aquaflector

I´ve assembled a small scale model of the water pasteurization system that we hope to test in June or July. I´m trying to identify an organization that has experience with other water projects and has a presence in a sunny rural area where we can install it. My friend Larry Winiarski Jr. (whose father invented many of the stove and oven designs that I´ve been implementing) has invented a way to make a very inexpensive solar concentrator using strips of aluminized mylar stretched tightly in metal frames, and ganged together to track the sun. It could just as well be used as an economical way to increase the output of a solar electricity generator, which is the application he originally had in mind for it.

My contribution to the design is a yet-to-be-proven control system that uses an odd-shaped bucket of water with a slow leak, where a floating weight tied to the control arm falls at a varying velocity during the day to precisely follow the motion of the sun. (I haven´t yet calculated the exact shape of the bucket required, but it´s represented in the model by a sort of diamond shaped bucket, which is a very rough approximation of the needed shape).

This device takes advantage of the fact that purification of water doesn´t require boiling, but only pasteurization. That is, as long as the temperature is held at a certain temperature for a certain amount of time, all of the dangerous bacteria and viruses will be killed. The amount of time varies inversely with the temperature, but the absolute minimum is 65 degrees C, at which pasteurization requires about 30 minutes. Raising the temperature of water from room temperature to 65 degrees C requires only half as much energy as boiling the water! But holding it at that temperature requires either the expenditure of more energy or the use of a well insulated container.

In the aquaflector system (so named by Larry), the untreated water enters one end of a shallow, wide heating duct that is suspended about 4 meters above the ground. The top of the duct is covered with insulation, and the reflectors concentrate the sunlight on the bottom of the duct to heat the water. At the far end of the duct is an exit pipe with an automotive thermostat (the little red thing between the water duct and the retention tank) that opens at 71 degrees C. The heated water enters an insulated retention tank that has been sized to hold about half an hour´s output, and the bottom of the tank contains an exit pipe connected to a float valve so that when the tank is full, the coolest, densest water (which has spent the most time in the tank) is released for use.
A further improvement to the design which I haven´t yet reflected in the model is the use of a heat exchanger to improve the efficiency of the system. ¨Waste heat¨ from the treated water will be used to preheat the untreated water, increasing the output of the system by a factor of two or three.

Relleno picado -- a very Peruvian dish

Sonia has been teaching me to cook some new dishes lately, like guiso de calabacín (a delicious squash stew), estofado de pollo (a juicy chicken dish with large chunks of potato and a variety of other vegetables) and most recently, something called relleno picado (chopped blood sausage) that seems to combine a lot of the elements that are typical of Peruvian cuisine. The final product doesn´t look very interesting, so I´ve only captured a photo of the ingredients. But it doesn´t matter since you normally eat it as a sandwich filling.

The ingredients are:
  • a blood sausage called relleno (which is hard to find here in Lima, but Sonia knows a lady from Chincha who brings it to a market near my apartment once a week). It´s wrapped in a real intestine like old fashioned sausages, and sometimes contains rice.
  • a hot pepper called aji amarillo which is used in just about every Peruvian dish that is spicy

  • an onion (Peruvians prefer red ones for almost everything)

  • a couple cloves of garlic (essential for almost any Peruvian food -- even for plain white rice that you´re serving as a side dish)

  • a bunch of spearmint leaves (also very common in Peruvian cooking)

You just chop everything finely and fry it together. It´s hard to describe the flavor. The mint is a nice complement to the other flavors. It´s really tasty!

Water For San Genaro -- part 5

I went to San Genaro last weekend to see how the neighbors are getting along with their new water resource. Freddy invited me and Sonia to eat lunch with his family, and told me that so far their monthly water bills have been much lower than we anticipated. Each family has had to pay a grand total of $1.60 for the first two months of usage. That´s about a tenth of what they used to pay! Unfortunately there are a few neighbors who don´t like the idea that someone else might receive more savings than themselves, and are insisting that people pay for the amount of time that they use the water rather than just splitting the bill evenly each month. But monitoring the amount of time each family uses would take a extraordinary amount of effort for the small improvement in ¨fairness¨.

Now that the neighbors have one success under their belt, they´re meeting every month to discuss other ways to improve their neighborhood. Lately, discussion has turned toward the construction of an illegal connection to the sewer system! I told Freddy that I thought it was a very bad idea and that it would leave them liable to severe penalties if it were discovered. But I was encouraged by the fact that the neighbors are realizing that they can accomplish more when they organize themselves. I guess empowerment has its good side and its bad side.