Building a Proof of Concept in the Back Yard
Why get all steamed up (joke - oh, good grief) about electricity? Heat is what solar does well.
Use the heat directly and simply - don't get caught up in the problem of trying to store it
- just make the installation a bit bigger so there is enough production in the day to carry through
the night.
Here is a small proof of concept - made from "found objects" - bathroom mirror tiles, skate bearings,
old fuel drums, car and tractor parts - hang it on a disused power pole and it doesn't cost that much.
Bad Water to Good
The objective is to show that it's easy to make potable water from bore water (which
is slightly too salty to drink) and/or grey water - which is household effuent from kitchen, laundry
and bathroom (ie. not black water or sewerage as in toilet effluent - doing that is political suicide).
Here are some water samples - it's not easy to photograph water, but it's an attempt to show
the difference as in before and after.
Fresh water on the left - bore water (middle) is clear to look at but undrinkable - and the
grey water (right) is milky with detergent and food suspended in it.
The total dissolved solids (TDS) in the samples was estimated using a resistance meter to
determine the conductivity in microSiemens, and the amount of dissolved solids was read from tables.
At this stage there is no analysis of the fresh water because of ongoing experiments with
different setups
| Water |
Conductance |
TDS |
| Fresh |
86 µS/cm² |
55 ppm |
| Bore |
940 µS/cm² |
600 ppm |
| Grey |
1920 µS/cm² |
1230 ppm |
and ideas. It would become too expensive to get lab reports on
each trial, so the conductance measurements are enough for the moment.
When the technique has been developed more there will be independent analysis and quality reports.
Given that so called "pure" water has a TDS of less than 1ppm, the fact that this elementary setup can
achieve around 50 ppm is very gratifying. In fact this may be too low in salts to be used for drinking
water, which is usually around 100 to 500 ppm for domestic supplies.
How Does it Work?
A fairly standard tracking fresnel reflector concentrates solar energy on an insulated collector,
heating the water which is circulating through as a thermosyphon.
This heat is stored in the steel heat transfer tank until needed by the water separator. The tank
is insulated by a double layer of household fibreglass batts and covered with an outer skin.
Raw water comes into the feed water tank on the ground (bottom left in the diagram) and is
pressurised for the trip up to the water separator. This is a normal household automatic pressure
pump, but a solar powered equivalent could be used eventually.
This feed is via the heat exchanger which transfers heat from the hot separated water coming
down to the cool feed water going up.
The two lines of separated water are returned to the waste water and the fresh water tanks, ready to
be pumped away for disposal and/or use respectively.
