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Difference between revisions of "Hexayurt infrastructure"

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Revision as of 03:51, 20 March 2007

Hexayurt Project Header

Overview

Take your house. Cut off the water, the electrical power, the natural gas, and the sewage lines. That's what a hexayurt is like without the infrastructure systems which need to be shipped with it as an integral part of the housing system.

It helps to think of your own house as you go through this - replace each system in your mind with the one from the outline below. Remember that the systems are huge - the electrical system isn't the wires in your house, or strung along the poles outside - it's the power station, the huge transformers, the high voltage long distance lines, and the aspects of the govenment which regulate the grid, plus the banking infrastructure to keep all that stuff paid for.

To provide services in the traditional way in the devloping world is extremely difficult. Even though some of these line items look expensive, it's important to remember that they are very, very cheap compared to their first world equivalent service infrastructures!

Hexayurt solar

Substitute for national grid or heavyweight solar with:

  • One 80 watt panel connected to a 15 minute AA battery charger (e.g. the new generation Rayovacs)

These items will be connected into a "power pillar" - a walk-up charging station where people come with their empty NIMH batteries, drop them into the charger, wait 15 minutes, then take them home. Assuming a 10 hour charging day, that services 40 sets of batteries.

Each AA NiMH battery has a capacity of approx 2000 mAh at 1.25V, equivalent to 2.5 VAh. If charger efficiencies are 25% (my guess) then we need about 10 Wh to charge each battery.

80 W for 10 hours is 800 Wh per day or enough to charge 80 batteries a day.


Applications for this system include:

What won't work:

  • Heavy-draw mains appliances (toasters, video projectors)

Financial model:

  • $400 for the panel, $100 for the charger and pillar. ($12.50 per household)
  • $200 for 80 fast charge AA batteries say 4 each for 20 households.
  • $100 or 20 lighting units.
  • $700 total or $35 each for 20 households.

$50 per household should comfortably buy everything required for basic electrical services. A bare bones system (lighting and stoves only) would be about $12.50 per household because the cost of the panel, charger and pillar could be split between 80 households.

Hexayurt gas

Gas will be used for cooking and heating applications.

Substitute for natural gas infrastructure (pipes and plants, trucked in propane) with:

Wood gasification stoves use sophisticated combustion engineering realized in the form of cheap sheet metal forced air stoves. Two AA cells power ten hours of cooking, with a peak heat output of 3KW from finger-sized twigs. Wood gasification stoves are low emissions because the fuel is burned either as gas (volatiles boiled out of the fuel) in super-abundant oxygen blown in by the fan, or as charcoal similarly burned in abundant oxygen.

Wood gasification stoves are rated as ten times more efficient than open fires, and three times more efficient than high-efficiency clay stoves.

Financial model:

  • $20 or less per stove, one per household

Fuel costs are low, perhaps $1 per household per week or less. In a small and well insulated shelter or home, even this relatively modest heating device should provide most or all of the heat required -- even through the winter -- in most climates.

Hexayurt water

Introduction

A substitute for Water purification plants and pipelines, or trucked-in water, achieved with: Solar water pasteurization.

Purpose

Primary use of the cooker is to heat water to 160+F for the full day as a means of sterilizing both it and the container.

Designs

Build a simple solar cooker into the side of each hut using the same building materials as the rest of the unit (i.e., reflective insulation boards). 

Issues

  • Sterilisation is effective against biological contamination however it will not remove heavy meatal contamination.
  • If the water temperature is less than 160F then bacterial growth will increase rather than killing bacteria off. Reliable indicators that the water has been fully treated, are being worked on by a variety of groups.
  • Also, I do not suggest cooking on the Solar cooker as a core technology. General field reports seem to indicate solar cooking doesn't go over terribly well in many areas.
  • The aim of this is to capture solar heat and concentrate it in the water. This conflicts with the general cooling strategy for the Hexayurt, which is to reflect as much solar heat as possible and prevent it from being captured. Better would be to place the solar cooker facing away from the Hexayurt, towards the sun. Then it will intercept solar energy that would have hit the Hexayurt and direct it towards the water.

Cost & Materials 

The financial model is based on $10 or less per household for one solar cooker.

Interwiki Links

Hexayurt sewage

Substitute for pit latrines, septic systems or conventional sewage handling with:

Financial model:

Possibly as cheap as $20 per household in warm areas, assuming shared toilet banks. Practical, realistic designs have not undergone the "value engineering" necessary for this application yet, so are still too costly, although clearly a cheap, basic, functional unit for any given climate could be created.

Water System

Priorities

  • public health is the overwhelming priority.
  • low cost is essential - if it's not cheap, it won't be used as much and won't achieve as much.
  • low ecological impact is very desirable if it doesn't compromise public health.
  • suitable for various cultural practices. Target users may be accustomed to using water to cleanse (but can most often cope with small amounts of water), or other anal cleansingW methods, so the device should ideally tolerate sticks, rocks, paper, or whatever else is likely to be thrown in.

Options

Development Status

Together these systems appear to combine to provide the majority of the services provided by the pipe-and-wire infrastructure harness of a first world household for a cost in the neighbourhood of $200 per household for a relatively plush system, and a minimalist installation could be under $100 per household or less with more resource sharing.

The vast majority of the products required to put together this package are common, off-the-shelf items. However, very few if any of them have gone through the rigours of deployment in the field conditions we are talking about. The CCFL flashlights are an excellent example: available in stores for around $10, with an excellent battery life and 10,000 hour or better tubes, they appear perfect. But the are not waterproof, only water resistant.

What would the failure rate be if we deployed them in a refugee camp? Would the manufacturer - either Eveready, or the plant which makes them in China, be willing to make small design changes or product a special edition, or would we hit dead ends unless we were willing to have a custom model produced from scratch (a whole different line of business.)

My hope is that we can rely on the open source approach to solve many of these problems - that as long as all of our intellectual property is open, then domain experts can help us find answers to all the questions that come up, without feeling like they are helping a for-profit or partisan group. Free IP means freedom to participate for many people. We can give the companies who produce the products we want tweaked or improved the ideas on how to do it, and they can use them or not as they please.

My estimate is that it will take 10 to 15 years for this approach to be fully vested - tried in the field, failures identified and rectified, and technologies matured to the point where it becomes obvious to all parties that we have a scalable solution. Whole systems design is hard, and takes time, and a lot of lives are at stake.

But if we don't start now, we aren't going to have that fully finished solution 10 or 15 years down the line.

This is not to say that we could not push much harder and much faster - deploy units in the field and just see what happens, and learn by doing. But to have confidence in that approach I'm going to need a really experienced NGO-type to vett the project in serious detail and guide basically every step. I'm not prepared to have somebody die because I sent the wrong brand of duct tape or the stove turns out to perform poorly on the available fuels where it was sent.

PS: the $200 number is padded for a more expensive toilet, and for a share of village-scale utilities like the one-per-village 2 kilowatt central power utility.

PPS: http://www.rmi.org/sitepages/pid560.php (the Sustainable Settlements Charette, where a lot of the definition of scope happened)

http://worldchanging.com/archives/002202.html (some older writing I did on infrastructure which might help fill in some details in my unusual perspective on this stuff.)