Vacuum Tubes vs Flat Plate
These are the two basic considerations when you want to choose a solar water heater for your house. There are tons of companies on the Eskom scheme today and all of them offer a variety of systems. The question is! Is there a right or wrong system?
The answer is simple..........NO!!!!!
Every single system listed on Eskom's site WILL work and WILL save you money. All of them carry at least a 5 year guarantee (an Eskom requirement) and all of them will give you value for money. Some systems are more efficient than others, some are more expensive, some are imported.....So how do you choose the right one.
I am dealing with solar quotations and potential customers on a daily basis and have had all the questions. It usually goes something like this....." I had XYZ Solar give me a quote and they say that Vacuum tubes are better" or " I had XYZ Solar give me a quote and they said that the pumped systems are better".
I will do a 4 part series on the main differences in systems. (Vacuum Tube vs Flat Plate, Pumped vs Thermosiphon, Direct vs Indirect, High vs Low Pressure, Large Geyser vs Small Geyser)
I will try and list facts of all the systems to help you decide...Starting with Flat plate vs Vacuum tube
Flat Plates
1) Older, but tried and tested AND developed technology
2) Works in much the same way as a the green house effect
3) Produced mainly in virtually all countries that produce solar collectors
4) They are well suited to
higher ambient temperatures and work well in situations of consistently higher sunshine (SA, Australia, parts of USA.)
5) They take up less "roof space" since the actual heat collecting are is bigger.
6) Can reach easily 80-90'C in summer (in SA) - ( BUT who uses 90'C water anyway)
7) More rigid than most tubes, because of the more sturdy design
8) Can be cheaper than tubes
9) Frost protection needed
10) Easier to install and handle
Vacuum Tubes
1) It is true that its the newest technology
2) Works in much the same way as a Thermal Coffee Mug
3) Produced mainly in the East but also by some European manufacturers
4) They are well suited to
cold ambient temperatures and work well in situations of consistently low sunshine (parts of europe, canada etc.)
5) They take up more "roof space" to yield the same result as flat plate collectors (because of the drastic reduction in actual absorber area)
6) Can easily boil water in summer months (in SA)
7) When the vacuum is lost it looses its efficiency (something you may only pick up a lot later)
8) Can be cheaper to install than Flat plates
9) Virtually frost resistant
10) More parts (manifold plus 10 to 32 tubes)
So both has pro's and con's ....In my opinion the flat plate(and its sort of proven by facts
Wikipedia - vacuum tubes ) is much more suited for South African climate. We have a lot more sunny days than cloudy ones, our ambient temperature is high throughout the year, in winter months we still have warmish mid day temperatures(only the evenings and mornings are freezing cold) and its more rigid- since we live in Africa and Africa is not for sissies....
I will follow up soon with the rest of the types...
Good Day To All
Pieter Swart
www.4seasonssolar.co.za
