What is Quality in a Solar Water Heating Panel
General principles
Solar water heating panels are a safe and environmentally friendly way of producing heat. It makes no sense to us if the panels need to be regularly changed, maintained or serviced.
Solar thermal panels should be built strongly, have a very long working life and should require limited maintenance producing versatile controllable heat for domestic, commercial, new build, self build and process heat for industry.
They should be designed for use as a sealed system through heat exchangers rather than directing potable water through the panels so that they can be used for maximum efficiency with more than one heat circuit if needed. Solar systems built with our panels should be very low maintenance structures with as strong and nearly as long lasting as the building they serve.
The materials used should be recyclable and environmentally benign but strong long lasting and of the highest quality. Our solar water heating panels are built to these standards.
The panel box should be light but strong –as strong as a roof
The solar water heating panel tray is stamped from a single sheet of aluminium manganese alloy, anodized for corrosion protection. This seamless method of construction is not only very strong, but there are no rivets to come undone and no seams which can act as weak point in the structure.
Most other panels are made up of a tray constructed by welding aluminium profile together and then welding a back sheet, to form a box. This generally means that the panels have to be thicker and heavier without being stronger.
The glazing should be strong low reflection, high absorption and low emissivity
The glass is safety solar low iron tempered glass 4mm thick. It is TUV tested to withstand golf ball sized hailstones. It is highly transparent and allows more than 93% of available light to reach the absorber plate. This glass will not let you down. The MCS Certification, equivalent to the Solar Keymark Standard ensures the panel provenance & performance.
Some use environmentally unfriendly plastic (which discolours and decays over time) and others use low iron tempered glass but without the TUV hailstone resistant testing.
(Fixed to the weather station wall/mountain the Vacuum panels are providing the heating & hot water needs of the station).
The absorber plate should be of long working life
Patented Solar Thermal Panel Absorber Folding Technology
The absorber plate is made of a single sheet of aluminium and using a specially patented technique, is folded around the heat pipe.
This means that there is virtually a 360° contact between the heat pipe and the absorber plate. This method of fixing enables the sheet aluminium and the copper pipe to expand and contract while holding their shape and full contact with each other so that heat can conduct efficiently with minimal loss. There is no welding, soldering or bonding used on the absorber in Thermosolar panels similar to the way the Aerospace Industry builds planes.
Most panels use aluminium or copper absorber sheets but spot weld, solder or laser welded together from fins. The welding is a potential point of failure with the heat stresses. In addition, the heat pipe is soldered, welded or laser welded to the absorber plate. The point of contact between the absorber and the heat pipe is only a few degrees. Over a period of time due to the heat collected on the absorber surface and the heating and contraction of the heat pipe and the absorber plates the heat pipe tends to become detached in places causing less heat to be transmitted to the heat pipe and the panel to perform less effectively and with less efficiency.
The heat pipe should be of long working life
In the solar panels the heat pipe is a continuous copper pipe without joints (except at the two connections to the manifold pipe). This is a robust form of construction preventing leaks, weeps and avoiding liquid loss in the collector which tends to condense on the glazed surface, thus preventing optimum efficiency and over a period of time decaying the absorber surface.
Most panels weld or solder a series of parallel heat pipes to the manifolds, creating the necessity for at least ten or twelve joints in the heat pipe to and from the manifold, making failure much more likely.
Our heat pipe is designed to eliminate the possibility of leaks, using no joints and hence avoids liquid loss which could otherwise condense on the glazed surface. Such a system will have a longer working life.
The Panel absorber surface should be selectively coated with an environmentally friendly material
The solar water heating panels are selectively coated (creating a series of microscopic ridges to present a greater surface area to the light) with our own formula aluminium oxide coating, which is designed to produce only useful heat for the application rather than to produce all possible heat. This coating is 100% safe.
Some solar panels are coated with black paint, which performs in hot direct sunshine conditions but not in cloudy light conditions or on cooler days. Some panels are selectively coated in black chrome. We think this is an area of potential environmental danger as well as potential health risks. See US Dept. of Labour’s note on Hexavalent Chromium.
The ability to stagnate without causing collector damage
The ability to hold heat stresses over a prolonged period of time. The owner of the collectors should be able to leave the property vacant and unattended knowing that the panels will safely stagnate and will not require covering in times of high insolation and low heat requirements.
Super Hot solar swimming pool heating which has ability to stagnate without damaging the panel
This overcomes the problem of having to “dump” the heat. Our panels are designed stagnate at 374 Fahrenheit (190 degrees Celsius) – in other words they will not get hotter than that regardless of insolation conditions. If panels are required for continuous heat processes which will always draw the heat and which require more heat than the solar system can produce, then the end user should specify one of our process heat panels which stagnate at around 482 Fahrenheit (250 degrees Celsius).
No Heat Dump Required
Our solar water heating panels do not require a Heat Dump
The panels are designed with 4 connections. The meander within the panel negates the need for a heat dumps as in stagnation the glycol will flash to steam.
The panels are designed with 4 connections. The meander within the panel negates the need for a heat dumps as in stagnation the glycol will flash to steam.
The glycol will then get pushed out of the collector into the expansion vessel. For this reason it is better to have collectors with four connections.
There are two kinds of absorber types;
1st – Collectors that cook out
Certain panels or all tube systems with only 2 connections. Easy to install but the disadvantage is that once they start to stagnate all of the glycol needs to steam up to get transported out of the absorber. This means very high stress on the glycol and the membrane of the expansion vessel because of the large amount of steam which reaches all the way down to the vessel. On larger system you would always need to install a pre expansion vessel to protect the membrane of the main expansion vessel.
2nd – Collectors that steam out
These are collector types with 4 connections. This type of absorber will push the glycol out of the absorber as soon as steam develops, pushing it to the expansion vessel. The glycol will then be protected inside the expansion vessel. As soon as the panel cools down and the steam starts to condensate the glycol will get pushed back into the panels, this design increases the longevity of the glycol and the entire solar system, without the need for expensive heat dumps
The expansion vessel should have at least the pressure related to the height of the system + 0.5bar. Though the system should have a minimum pressure of 1.5bar on the entrance of the pump. This pressure is important for the pump to work properly.
The ability to produce controllable hot water
Panels are controlled by the digital controller; the controller is installer programmable (to enable high efficiencies to be achieved by reflecting the end user’s life style and living requirements) and by regulating the heat precisely. There are various controllers, some can divert heat to two or more separate hydraulic systems according to the installer’s programmed requirements. SECON Renewables stock a range of very good controllers.
Solar Water Heating Digital Controller
Designed to avoid internal condensation issues
Hot Solar Water Thermal Solar Panel Designed to avoid internal panel condensation issues
Many panels are permanently covered with condensation; while some condensation is inevitable our panels are designed to remove any internal condensation within an hour of light striking the absorber surface making the panels last longer and work better.
The ability to withstand high pressures and work at high pressures
Australia Solar Swimming Pool with Vacuum Panels
In the solar water system the heat circuit is pressurised to ….psi. This means that the Glycol does not evaporate until the temperature of the heat circuit is in excess of 120+ degrees Celsius thus ensuring that in very hot daylight conditions all heat requirements will still be met. The heat circuit is a Tichelmann system which ensures that pressure is equally maintained in all parts of the system.
The connection design should be solid and easy to fit
The patented connection kits, which connect panel to panel and panel to the heat circuit are robust easy to fit and will last longer than brazing connections without leaks or weeps; these connections have been used in Europe in hundreds of thousands of systems over many years without any problems.