Introduction
Availabilty of hot water on tap is taken for granted by
many of us, but for the vast majority of South Africans this is a luxury they have seldom
experienced and up to now, have seen no prospect of in the future.
Solar water heating is the obvious solution in South
Africa. The main drawback to date has been the cost of an installation. High cost has
prevented widespread use even in relatively affluent areas.
In poorer urban and rural situations electric water heating
is often unavailable due to lack of an electricity supply and even when electricity is
available, electric water heating is unaffordable due to high running costs (electric
geysers are the single largest electricity consumers in most homes costing some R40-R60
per month which is simply not affordable for low income families). In these cases water is
usually heated on open fires or coal or paraffin stoves or, in most instances, not at all.
For those of us with hot water on tap consider what a major
deprivation it would be to;
- Wash the baby on a cold winter’s day with cold water
- Shave with cold water on a cold winter’s morning
- Wash dishes without hot water to loosen burned food &
fat
- Bath or shower using cold water in winter
Currently available solar heating systems
Current technology consists either of conventional
metallic collector plates with glass or acrylic covers with integrated or separate storage
and plastic collectors usually with integral storage. Installed systems cost in the range
R1 000-00 to R3 000-00 for a smallish house which, if affordable, is still economic as the
electricity saved pays for the system in 2-5 years. Disadvantages of currently available
systems are;
- Affordability
- Susceptibility to hail in the case of systems with glass or
perspex covers
- UV weathering of plastic systems
- Scaling (lime deposits in the collector)
The idea behind this system
The idea is to make use of discarded plastic (or glass)
no deposit beverage containers which would otherwise end up as a litter problem or take up
landfill space as little or no recycling takes place using such containers. By using a
heating system which makes use of such containers we can;
- "Recycle" beverage containers
- Provide small scale solar heaters at nominal cost
- Develop micro industries to source discarded bottles,
assemble systems and maintain systems
- Encourage "self help" solutions
- Save electricity, reduce depletion of coal and other natural
resources and reduce global warming
Patented Concept
The concept has been patented as South African Patent
No. 96/9441
The basic module would probably use 6 of 2 litre bottles
yielding 6 litres hot water.
The units can easily be connected in multiples giving 12
litres, 18 litres etc.
Components of an installation
Unique/ manufactured components;
- The header. In test prototypes this has been molded polymer.
We envisage this being either injection molded plastic in high volumes or precast in
cement in low "self help industry" volumes.
- The insulation. This could either be formed polystyrene or
similar foam, an airfilled bubble "sock" or a low tech wrapping and cladding
User/ installer sourced components;
- Used 2 litre beverage bottles. Either purchased & drunk
specifically for this purpose or sourced as a recycling/ recovery operation
- Hose & fittings. A length of standard garden hose with
barbed or click type fittings.
- A valve – plastic inline type or other shutoff
solution.
- Black paint. Applied to the exposed bottles to improve heat
transfer.
Installation and Operation
The assembled collector is placed on a roof (or any high
structure) close to a tap.
In the morning the hose is connected to the tap and filled
up (overflow pipes indicate when full).
During the day solar energy heats the water in the lower,
exposed bottles. The hot water moves to the top insulated bottles by convection.
When the sun goes down the lower bottles lose their heat
but the insulated bottles retain their heat.
When needed, hot water flows by gravity via the hose into a
bath/tub, bucket or similar.
Typical water temperatures are;
Time of day |
Summer |
Winter |
| Early Evening say 6-7pm |
60°C |
50°C |
| Next Morning 6am |
40°C |
30°C |
| Tap (cold) water temperature |
25°C |
10°C |
Note that normal mixed bath water temperature is
around 35°C so that anything above 30°C seems quite warm or hot.
