Eskom Solar Heating & Water Quality
At present in South Africa we are in the middle of an energy crisis with the parastatal Eskom suffering from badly maintained old and failing generating plants. The electricity supply is erratic and the cost per unit is escalating annually at a staggering rate.
“From 2007 to 2021, electricity tariffs increased by 753%, whilst inflation over this period was 134%. Thus, electricity tariffs increased more than five-fold in real money terms in 14 years” (credit Google) and the predicted increase about to come into effect is widely believed to follow the trend of the last 5 years.
Unfortunately with modern technology, fashions, and the availability of luxury items electricity has become vital to the modern lifestyle and with the present trend towards respecting the environment, climate change and reducing reliance on fossil fuels – especially the newly proposed to move from the internal combustion power vehicles to electrically powered vehicles – is set to completely swamp an already overstressed supply. So again most of the responsibility has fallen on the end user, one can either stick their head in the sand and pay the exorbitant tariffs, or try to minimise electrical footprint by making appliances more efficient when it comes to electrical usage. As is widely known one of the biggest offenders when it comes to electrical usage is the water heater, known in South Africa as a geyser with heating elements range from 1.5kW to 3kW dependant on size, manufacturer and model. Taking into consideration that a 150ltr geyser with a 3kW heating element takes up to 3 hours to raise the temperature in the geyser from ambient cold water temperature to 65°C, equating to an energy consumption of 8.72kW!
So how to get rid of this power hungry beast?
Will we have to do without hot water? Thankfully there are alternatives using nature’s energy, i.e. solar power.
There are two main technologies of the process of solar heating your water. The older technology uses flat plate collectors to collect the solar rays and transfer the energy as heat to the water. But as the panels lay flat, the solar rays strike the panels at an oblique angle during the early and late parts of the day and are only perpendicular at midday. Whereas with evacuated vacuum tube technology, solar angles (the angle at which the panel meets the sun) plays a very little role as the sun is always striking at an optimum angle.
Because of the pure vacuum between the inner and outer casings there is virtually zero heat loss. This is evident by touching a glass vacuum tube which is cold while the liquid inside can be boiling. Almost 94% of the suns energy is directed to the inside of the tube and is captured. Flat panel collectors will always lose heat through the glass, and become less efficient at higher temperatures.
So many feel that the newer technology of the evacuated vacuum tube technology is more advanced and efficient than that of the flat plate but how does it work?
Solar evacuated-tube collectors contain rows of tubes which are constructed by encasing metal absorber tubes inside transparent glass tubes. The air in the space between the two tubes is removed to create a vacuum which prevents convective or conductive heat loss.
(When dealing with vacuum tube solar heating systems one must be very cautious as the temperatures of vacuum tubes versus flat panel collectors can be as much as two times higher so overheating needs to be addressed properly to avoid damage and possible bodily harm.) Theevacuated vacuum tube technology works in a similar way to a thermos flask by trapping the heat inside and providing an insulation barrier against heat loss back to the air. Evacuated vacuum tubes utilize a copper heat pipe in the centre of the tube (some models utilise fins for even better energy absorption).
The solar energy is transferred to the heat pipe which contains a small amount of liquid (normally water with a food grade glycol) that is under a vacuum. Physics dictates that liquids that are under a vacuum will boil at a lower temperature. Because of this phenomenon, the liquid inside the heat pipe can boil as low as 30 degrees Celsius and turns to vapour.
The vapour rises to a condenser bulb whereby it is cooled by releasing heat through the bulb into the copper manifold through which the water to be heated passes and changes state back to a liquid, which sinks back down the heat pipe. However the temperature exerted on this heat exchange surface can peak as high as 150°C. This will cause minerals in the water to come out of solution and into suspension and suddenly scale build up on the heat exchange surfaces comes into play.
Just 1mm of scale build-up on heat exchange nubs can results in up to 40% decrease in heat transfer efficiency while 1mm build-up on the inner bore of pipe work can result in up to a further 10% decrease in heating efficiency due to the scale absorbing heat energy from the water as it passes over it.
So what options are open to us?
- We could soften the water using a traditional ion exchange but that then brings its own set of disadvantages –
- Softening the water will alter the pH from base to acidic which means that the water will be corrosive and the installation will be more prone to chemical and electrolytic corrosion
- This process would be removing healthy minerals from the water and replacing them with three times the amount of salt which is not advisable for human consumption
- The regeneration of the ion exchange beds is both time consuming and expensive if one takes into consideration the constant requirement of water analysis’s to check hardness levels. It is also very bad for the environment to evacuate sodium enriched water into the municipal waste systems as removing the sodium is very difficult and expensive for them. For this reason many states in America have started to ban ion exchange softeners
- We could explore new technologies such as electronic capacitive impulse technology which combines new thinking for an old problem using the natural process of electrophoresis. This technology is un-intrusive as it is fitted on the outside of the pipework and works by manipulating the ionic structure of the scale forming calcium and magnesium crystal from a 3 dimensional snowflake shape which due to electrical attraction is prone to the formation of encrustations to a simple rod shaped mono crystal with only a positive and negative end which can only form strings which would be carried away in the water flow and not form encrustations. This new technology works in three steps
- The manipulation of the ionic structure of the crystals stops the formation of new encrustations
- Via the natural process of electrophoresis, and the formation of the mono crystal, a by-product is carbonic acid which will dissolve the already formed scale encrustations.
- When there are no more scale encrustation to dismantle this process will deposit a protective carbonate layer on metallic pipes creating extra protect against both chemical and electrolytic corrosion
To go into this process in greater detail please visit www. https://www.amanzirms.co.za/cwt-technology/ where the processes and chemical reactions are explained in greater detail.
