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RAINBOW POWER COMPANY LTD
E-mail Newsletter #76
30 September 2004
CONTENTS:
1. MONTHLY OCTOBER SPECIAL
2. ELECTRIC FENCES
3. 12V EMERGENCY PUMP
4. FUTURE COURSES
5. CONCLUSION
1. MONTHLY OCTOBER SPECIAL: A battery charger is a great
back up to a solar system, particularly when you get
several days of rain or someone in the house decides
they want to watch the cricket for 3 days straight! The
Australian made Woods ‘Dialomatic’ chargers
are robust and also have the advantage that they can
charge an individual 2 or 6 volt battery. For October,
we are offering 10% discount off the published price
of our 12V-30A model (40A peak). Check out BCH-032 on
our website for more details.
2. ELECTRIC FENCES: Electric fencing can be a cost effective
and practical method of fencing for a wide variety of
animals.
There are several brands and models available from rural
agricultural stores which are battery powered as opposed
to being powered by the 240V grid. The battery type units
can then be powered by solar modules.
Due to the wide selection of energizers and accessories
on the market, we no longer sell the energizers. However,
we can supply you with a suitable solar panel and battery.
When you buy the energizer, only buy one as big as you
require, eg, if a 3 km unit will do the job, don’t
purchase one for 20 km, as they will need a solar panel
several times larger and more expensive than you’d
otherwise require. A 3 km energizer can be typically
powered by a 2W solar module.
Several months ago one of our readers, Jules, submitted
some hints about using electric fences which is reproduced
below:
“I have used a number of different electric fence
units, from small to medium large, to power up to several
kilometres of fence, and I believe that they are an almost
essential part of fencing. In theory, smaller units are
fine for shorter fences, but in practice, shorting out
from long grass/plants is an unavoidable drain in most
situations. Medium and large units are available using
12V power and either an attached solar panel or a separate
panel. The units with a built in solar panel are rather
costly for what you get and the logical conclusion might
be to run your fence off your 12V home battery bank/solar
system. Provided all the connections are good, and the
unit is operating properly, this causes no more trouble
than a pulse across your TV screen with each fence discharge.
There are however two major problems that inevitably
crop up over a longer (several year) period:
a) As mentioned in your book (Energy From Nature), lightning
is a hazard to electric fence units. Even if you do not
have any direct strikes of lightning, a farm fence is
a custom designed electricity catcher. It is of course
possible to use diverters to earth (most) of a lightning
strike and it is sometimes possible to detach a fence
during a storm (though this could be dangerous in itself).
The problem with lightning is that the voltages generated
are just so huge that any form of protection has its
limits.
b) Electric fence units are subject to more failure
than most other electrical equipment. I’m not sure
why this is, but I’d guess that the mixture of low
voltage with strong pulses of high voltage is problematic.
It is quite common to get some sort of feedback of high
voltage from the output side of the circuit to the input.
Some units seem to do this when in perfect working order
and others can develop it as a fault where transformer
insulation breaks down.
Both of the above failures can be very serious for sensitive
electronic equipment like computers and solar regulators.
The best and safest way to power an electric fence is
from a separate panel/battery/earth system preferably
housed in a shed away from your house. A reasonably cheap
and very functional system can be put together with a
second hand solar panel (and if you’ve been using
solar for a while you might well have a spare), a decent
car battery (or that size of deep cycle battery), and
the highest output 12V fence unit you can stretch to.”
3. 12V EMERGENCY PUMP: With the fire season approaching
and many people now buying ‘back up’ water
tanks with our increasing drought, I thought I’d
share a few ideas with you.
An Emergency Pump on a Grid Powered House:
In the past year I have been receiving increasing numbers
of inquiries from grid connected home owners about solar
and 12 Volt water pumps. These inquiries are coming as
a result of a number of community concerns including:
1) The aerial footage of dozens of brick homes burned
in the Canberra bush fires a couple of years ago next
to swimming pools full of water created a lasting impression
in some people’s memories. When there is fire there
is a danger that the city water pressure or your own
water pump could fail.
2) A few years ago some city Councils banned the use
of water tanks. Now some of the same Councils are giving
homeowners subsidies to install them! Some Councils have
advised their rate payers that the days of being able
to use town water for their gardens are gone forever.
In some tank locations getting a plumber and an electrician
to put in a 240V pump can be quite costly.
3) There are increasing concerns about the reliability
of our grid supply which may be needed to supply household
water requirements.
4) The provision of a pressurised emergency water supply
by installing a header tank can be expensive or difficult
on some properties.
So what are some of the possible solutions? Generally
the ‘problem’ is to pressurise water from a
ground mounted rainwater tank. In some cases the tank
is near the ‘grid’; in other cases it might
be next to a shed or garage.
A battery charger powered pump would have one of our
Flojet domestic pressure pumps connected to perhaps a
car battery which is kept charged by a small automatic
(regulated) battery charger. Even a car battery should
power the smaller Flojet pump for several hours should
the grid fail. This is long enough to provide domestic
water for an emergency loss of power for at least a couple
days. A larger deep cycle battery would be suggested
if you experience frequent grid failures.
A solar powered battery pump might be the best option
if the grid is a bit far away or if there are frequent
or prolonged grid failures. If you are only going to
use the pump for say an average of twenty minutes a day,
a 5 Watt solar module might be large enough to do the
job!
In all cases, you need to remember that wet lead acid
batteries are potentially dangerous if not installed
properly. They release explosive hydrogen gas when charging,
contain acid, and the cabling should be fused to prevent
fires in the event of an electrical fault. Contact our
office for more detailed advice.
4. FUTURE COURSES We have scheduled 2 courses prior
to Christmas:
Weekend Course (for system owners) 13 & 14 November
Overseas Training Course starts 18 November This is
a one month course designed primarily for overseas students.
We only have 1-2 places left. See our website for more
details.
5. CONCLUSION: That’s all this month folks! Send
us your ideas and questions. However, there is no need
to send our newsletter back to us when you reply! If
you would like a price or product information, please
tell us which country you are from if it is not evident
from your e-mail address. This allows us to assess if
local GST (tax) is applicable or whether 240 Volt 50HZ
products will work in your country, etc.
Dave Lambert and the RPC crew |
