(Up to: Hacking Reality Proles And Technology Natural Gas )

What makes good, elegant technology? I think it comes down to using natural physical properties in a way that may not be so technologically superior to what has gone before, but that doesn't depend on a man-made power infratructure, or at least tries not to. It should also use these sources as directly as possible, e.g. you could, theoretically speaking, have a fridge that uses heat to induce movement in liquid, which could be pushed round a colling device, or something, but why not just skip all that? No moving parts is generally more efficient in these terms.

What natural resources are available as power sources?

• Convection/Conduction, as above, i.e. differences in temperature - could/should this be used to provide motion?
• Gravity
• Water movement - may come under gravity
• Light - this includes solar power, but may also be used in less "sophisticated" manners - take the simplicity of a sundial, for instance

Here are some things that prove that you don't need the latest gadgetry to get something useful done. I like to think that as ideas and technology evolve, it all gets simpler and more elegant.

• Pot-in-pot refrigerator, and also the main page for the awards that highlighted it (needs Flash, gah) and a German article on it too. It's basically like a one-way thermos effect - 2 ceramic pots, one inside the other, with wet sand between the 2, in a warm atmosphere. Heat evaporates from the outer layer, gets sucked through the sand, and the inside cools down.

I wonder if it's possible to construct a self-refreshing version of this that takes water from a supply and imparts it into the sand, so you don't have to keep refilling it by hand. I also wonder how well it would work in a cooler environment (seeing as it gets cold by being hotter outside), or if there's a way to use the idea in a UK environment.

• An article on slow sand filtration looks interesting, and links to www.davnor.com, who have a Biosand filter - see jpeg picture of how it works, and notice the cunning idea that as biomass builds up in the system, the efficiency apparently increases. These filtration devices always use the natural gravitational properties inherent to water-in-pipes, rather than any kind of powered pumps, too. Also need to look more closely at this some time.

Googling for this was inspired by similar a sand-charcoal-gravel barrel filtration method on a CAFOD flyer I got with a magazine. I'll see if I can dig out a proper link to that one, or scan it in, or something.

• Ground-Source Heat Pumps:
  The temperature beneath a certain depth in soil remains mostly constant around the year, I am informed, and can be used as a more efficient method to cool and heat flows of water. Nice introduction to GSHP
  Extensive US Government information regarding its use, including temperature maps of America, et al.
  Home Energy magazine article from 1994

• Perhaps slightly more complicated, and more "alternative" than "revolutionary", here's an article on Building your own BioDiesel station.

• Wow! I love the idea of a Solar Chimney, for its simplicity, as well as its view from the air. However, as is pointed out, it's pretty inefficient (probably so even after design improvements), and perhaps "to produce 200 MW at a practical efficiency in this high solar gain area will require a tower of about 1 km high and a collection area of 40 square kilometres" (although this may be based on the inefficient design).

• See also this solar tower in Spain which is effectively a big mirror to turn water into steam.

Maybe the problem is that we're averse to technology because it's inefficient, after becoming used to evolved technology that was once just as inefficient (e.g. steam power), but we've forgotten just where we've come from, and the necessary progress technology relies upon in order to become as efficient as we expect.

• The playpump, a system to pump water using the energy produced by kids on a roundabout.

• Stirling Engines are an old but still-interesting idea. They're not the most efficient source of energy around, and need some help to get going, but they do run on just a warm surface.

  • Here's a picture of a small one bought from Kontax:
    
    (For original photo and further comments, see it at Flickr)
  • Open Source Energy Network page on Stirling Engines
  • Aug 11, 2005: 500MW Stirling Engine project in S. California
  • Stirling Engine clock
  • Electric car that could use a stirling engine

  I wonder just how many things can be converted from manual wind-up (e.g. wind-up radios, etc) to a Stirling Engine-powered wind-up mechanism, especially (?) if they produce heat?

  • Rotary Stirling Engines including this Cola can engine that cools itself using its own shadow.

• Ramp creates power as cars pass (with corresponding Slashdot article). Nice. Maybe this should be part of a "boot-strapping" category of lo-hi tech that makes simple use of ongoing (but not necessarilly efficient) "advanced" technology, such as cars. See also BMW's turbosteamer concept.

• Similarly, capturing wind from cars may offer another way to tap fast roads.

• A new cookstove in Darfur highlights the fact that the evolution of a technology can be just as (if not more) important than the technology itself. The stove was developed by studying what was important to the Sudanese women. A more efficient stove uses less fuel, which means less time outside the camp, which means less exposure to risk. Sometimes it's not that the techology offers a new "thing" to do (the end result is the same) but that it assists something otherwise unoassociated to technology.

• Not quite so "low level", but interesting use of temperature to propel underwater robots based on volume, mass, and moving up and down. Sometimes it takes several steps.