Practical boiling

["Crispin" <crispin@newdawn.sz>]

Dear Stovers with an interest in Boiling

I have given this some thought and have come up with a practical use for
rapid boiling.

Every year we hear of some disaster or other where people are left without
water supplies and they have to make do with what they can find.  They are
always advise to boil their water before drinking it.

In developing countries there is a constant need to purify water and without
real changes in service delivery, people have to boil water to purify it.
This is going to become more of a problem in Africa in the near future
because people who are HIV+ with HIV- babies are encouraged to use bottle
feeding after 6 months.  This leads to all the problems that health
professionals have been railing against for many years; in particular it
gives babies bacteria that cause diarrhoea, dehydration and death.  Maternal
health professionals have been fighting the baby formula people for decades
to get people to breastfeed their babies for 2 years.

Now that HIV is so prevalent, there are serious reasons for encouraging
people to go to bottle feeding especially after 6 months of age.  Before
that, it has been shown, babies have a better chance of survival if they are
breastfed, even though there is a real chance of mother-to-child
transmission of HIV in the process.

You cannot have safe and successful bottle feeding without several things
being in place, particularly two regimens: one for the water/formula
preparation and the other for maintaining sterility of the nipples, bottles
and mixing vessls.

These require treated or boiled water.  Boiling all water used in infant
formula preparation is difficult and fuel consuming.  People do not do it
properly because it is inconvenient, life is hard and they are probably
already suffering from HIV/AIDS related conditions.

The challenge to stovers all over the world is to prepare a technology
package that will boil small amounts of water in a short time using as
little fuel as possible.  This means that the combination of
fuel+stove+water container must function as a package to deliver
convenience, sterility, affordability and sustainability in terms of
technology transfer and fuel type.

Our competition should have a practical side so that our actions do not
begin in words and end in words.  We should demonstrate a method of
preparing water in sufficient quantity and of high enough purity to allow a
person living in a remote locality the ability to bottle-feed an infant
safely.

The water vessel must be 'open season'.  Anything that assists the stove
developer to achieve the primary purpose is allowed.  The fuel has to be one
that can be made, collected, manufactured or is otherwise available in
remote areas.  The stove should be able to be fired rapidly and boil a
minimum quantity of water for a certain time period, to be established by
health workers in the area.  Three minutes is a likely minimum, but some
places have parasites that require longer boiling times - up to 20 minutes.

Thus flash lighting and flash boiling are recommendable to meet the time
constraints (adding convenience) but the boil must be maintained for a
certain period so as to kill the biological contaminants.  The empahsis
should be on system efficiency - i.e. minimum cost of fuel, or minimum
quantity of fuel used, or minimum wealth loss in terms of time (given an
'opportunity cost' value) and material and minimum time taken.  The stove's
depreciation cost might also be factored in.

Water purification kits are being distributed from the UK through Rotary
programs and they cost UKPounds 40 each ($64).  I suggest this is too high
for a practical stove-pot combination, however it could serve as an initial
guide.  Large numbers of the kits are given out each year so it is clearly
in someone's interest to do so.  They work but they use purification pills
which must be purchased ad infinitum.

I suggest that we take the figure of US$50 (selling to the public price) as
the limit for any recommended technology combination (fuel+stove+pot) and
that this be pursued by the Stove Group.

The things that remain to be defined are the amount of water to be boiled -
which I recommend be 3 litres, and the time to be held at the local boiling
point - I recommend 3 minutes.

I further recommend that the time taken to bring the water to a boil be
rated separately from the fuel consumption rating.  This can be done by
giving a distinct 'dimension' to the former by assigning a colour to
different classes of speed, in the same way partical physicists do with
sub-atomic bits and pieces.

For example, the time taken to reach a boil can be rated in minutes:

Under 2 minutes    Red
4 minutes    Orange
6 minutes    Yellow
8 minutes    Green
10 minutes  Blue
12 minutes  Ingido
14 minutes  Violet
14+minutes  Brown

The rating of the stove's fuel consumption should be the grams of water
boiled divided by the number of grams of fuel used to boil it for 3 minutes.

3000cc of water / 675 gm of fuel = 4.44

Thus a stove that performs (brings the water to a boil) in 9.3 minutes and
uses 560gm of wood to keep it boiling for 3 minutes rates as a "Wood burning
Blue 5.36"

Those seeking a Red rating will struggle to get a low fuel use value, but
there are customers for that class of product.  A claimed Green class stove
that runs badly on a particular day will find itself bumped into the Blue
class where its fuel profligacy may work against it.

This practical application offers many challenges to the stove makers.  It
rewards rapid heating in the beginning, a high turndown rate, an efficient
arrangement of fuel for initial combustion and an ability to stretch the
fuels' heat yield into the final seconds.

There is no real need to minimize the fuel load in the beginning as it is
the fuel consumed _during_ the test that is important, thus removing the
pursuit of unreasonable stove layouts specially designed to use tiny fuel
loads for contest applications only.

I believe this challenge is worthy of being met and that the rating method
is durable and flexible enough to allow for dozens of different designs of
stove, pot and fuel for many years into the future.

Sincerely,
Crispin



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