solar thermal collector type and its advantages
TRANSCRIPT
Easy-InstallPanel
“It's interesting little pipe play that can be significant in improving efficiency of the panel and also keeping installation cost with risk involved, in check.”
Spain was one of the most ambitious countries got ahead with solar thermal power. In this country a significant growth in domestic solar heating applications has been encouraging to inventors for some time and innovations are coming from not only industry but also from enthusiasts. In the issue of June 2015 our team represented array configuration of solar thermal panels which has same targets as this one but with different techniques. Where this will score points on that system, will be evident at the end of this article. Now, its clear that we are here for new kind of solar panel, which is great for domestic installations.
As we make it clear here that most of the systems produced in large arrays are forced circulated fluid in them, so mustn't be confused with that of thermosyphons primarily in Asian markets.
Take a textbook of fluid mechanics and head to piping chapters, first eyesight is always losses in the pipe. Yes!, The loss of pressure is just unavoidable if we pass fluid through pipe and is also proportional to the length of pipe. If the circuit is a set of pipes arranged with different lengths, as is the case for a most solar panel array, there is an unequal distribution of the volume of water circulating in each pipe. The shorter travel and the fewer changes of direction (elbows, T couplings, etc.), gives greater volume of water. Therefore to cause the same volume of water to circulate through each of the different circuits, it is advisable to compensate for losses of load. This is achieved with
balancing valves or by ensuring that the travel of the fluid with changes of direction (elbows, reducers, etc.) along all possible paths throughout the circuit of the system is exactly the same.
To get this object, it is known to send the heat transfer fluid through one end of the solar panel and to cause it to return through the opposite end. This require a path to be produced outside the solar panel for sending or returning the heat transfer fluid. There has been previous designs available with insulation on auxiliary lines that run outside the solar panel.
We are here to solve lot of problems that a designer faces when designing system lines of fluid. One thing is pretty clear here is, in this system the sending or return of the heat transfer fluid must be traveling inside the solar collector. On other hand, it is acceptable that a smaller amount of travel outside the solar collector, but every effort should be made to eliminate outside fluid recirculating parts. The effect thus produced firstly eliminates a large number of components such as pipes, elbowed couplings, flanges, absorption, expansion and insulation elements, etc. and secondly, it eliminates much of the work force involved in fitting the recirculation pipes to the connection and insulation elements.
All of the things were done by Spanish developers here by taking one factor into account is that the efficiency of the entire installation is must be increased, because the
insulation inside the collector body(Average thickness 40 to 60 mm) is normally much thicker than the pipe insulators (Average 2025 mm). Important factor to take into account is that all the parts inside the collector are protected from harmful atmospheric conditions, such as oxidation, galvanic corrosion, cracking, contact with acids, dirt, etc.
Don't get confused by statements below, you can come back and read again to understand the meaning after finishing article once. It is possible to do partial incorporation by integrating only the fluid recirculation pipe and the supply or return pipe respectively plus the double connection elbow for recirculation outside the solar panel. However, total integration of the elements inside the collector is also possible. We have three possible preferred configurations:
1) If the array of solar panels has three or more solar panels, three configurations are necessary: the initial one (through which the heat transfer fluid enters and leaves), the intermediate one (for circulation between the initial and final solar panels) and the final solar panel of the installation (where the return of the fluid to the initial solar panel begins).
2) If the solar panel array has two solar panels, the initial and final configuration will be sufficient, without the intermediate model.
3) If the solar panel array has only one solar panel, it would not need a configuration that integrates the
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initial and final solar panel.
Recirculation PipeUsing the sending pipe
for recirculation is considered good as the fluid is colder than in the return pipe, and because the recirculation pipe has less contact with the collecting surface than in the rest of the heat absorber it has less effect on its efficiency. It also enables better integration of other elements such as sensors or steam separators.
Now, just concentrate on Fig. 1 which shows a rough layout of a typical solar panel illustrating which has collecting surface, and the pipes forming the circuit for the heat transfer fluid(water). It can be seen that circuit has a bottom collector pipe and a top collector pipe. Between the two collector pipes multiple absorber pipes are arranged which in this case are parallel and connect the two collector pipes at bottom and top. At the structure, doesn't see any significant changes from conventional systems and it provides the heat transfer fluid with multiple routes to reach top collector pipe by parallel absorber pipes. Keep the length of parallel absorber pipes same is the advice from the developer. Did you ever find that header pipe is attached with different lenghts of absorber pipes/tubes?
Look at the panel and first thought must be ...make bottom collector pipe as inlet and top pipe as outlet for the panel permanently. Although it is sufficient for the single panel, this will loose when you have to make an array. It is advantageous for forming
arrays of solar panels for each of the collector pipes to have an inlet and an outlet for fluid. In this particular case these inlets and outlets of the collector pipes are also inlets/outlets for
the solar panel.
This solar panel is equipped with an additional recirculation pipe which also has an inlet and an outlet(simply open ends to use) for the heat transfer fluid. This additional recirculation pipe is the pipe used to return the fluid from the end of the installation to the start point. Easy way to use it, is for taking the heat transfer fluid to the most distant point of the installation before fluid circulates through the collector pipes. Again, the additional recirculation pipe is actually placed in the same space as the rest of the pipes in the circuit.
Let's start installing this panel in different configurations. For single solar panel as system, the outlet (the right end) of the top collector pipe and the inlet (the left end) of the bottom collector pipe can simply be plugged by a cap. Now, the outlet (the right end) of the bottom collector pipe is connected by a double elbow to the outlet (the right end) of the recirculation pipe. At this stage, these operations can be done outside the solar panel by using necessary elements. The fluid then enters at the left end of the recirculation pipe and gets out as hot from the left end of the top collector pipe. Thought of different configuration? No problem they are possible. Like, to arrange the caps and the elbow inside the solar panel and enjoy USP.
Return PipeNext configuration as in
Fig. 2 with an installation of three modular solar panels. The caps and the double elbow which cause the fluid to change direction have also been shown. An important note here, these are not engineering drawings by any means. So, most of the elements that piping should contain are not shown for reasons of clarity e.g. the connection accessories between
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the corresponding solar panels have not been shown. See, there is new return pipe of the heated fluid has is shown outside the panel. Some designers may opt for shielding the recirculation pipe from being struck directly by the rays of the sun. They can keep the recirculation pipe inside the same space as the collecting surface.
Structure suggests that the fluid enters through the inlet, flows through the recirculation pipes and become little hot. Next, fluid passes through the double elbow and flows down the absorber pipes formed between the bottom collector pipes to the top collector pipes. At the end top collector pipe can be connected by an elbow to return pipe placed outside panel .
Stopper & direct couplingFig. 3 has an improved
array compared to the one in Fig. 2 in which three different types of solar panel have been used. Here also, the travel of the hydraulic circuit outside the solar panels to be minimized as much as possible.
The first type of solar panel corresponds to the solar
panel to the leftmost of array. In this type, a stopper on its collector pipe has been arranged between the first absorber pipe from left and the next absorber pipe. This first absorber pipe has the same diameter as the collector pipes (Generally the parallel absorber pipes have a smaller diameter). Note that, only the outlet of the
top collector pipe is plugged by a cap.
We have four external caps, but they can also be produced inside the solar panel and even inside the collector pipe. The second type panel corresponds to the intermediate solar panel and is similar to that in Fig. 1 and 2. The third type corresponds to the rightmost solar panel and has inside it a
direct internal connection between the recirculation pipe and the bottom collector pipe.
In this system, the fluid enters through the inlet of the first solar panel. First, fluid flows through the recirculation pipes and the direct connection and then through the bottom collector pipes to the stopper. Fluid will rise to the top collector pipes through absorber pipes and finally passes through the first parallel pipe of the leftmost solar panel to the outlet of the solar panel. This outlet is the same outlet of the bottom collector pipe since the stopper obstructs the direct exit to the solar panels 2 and 3.
Here the first solar panel is base of system. You can add as many panels similar in design as that of panel no.2 in between first panel and rightmost panel.
Series ConnectionIn Fig. 2 and 3 the solar
panels are mounted in parallel, that is to say, the inlet and outlet solar panels are interconnected. It is also possible to connect them in series forcing the fluid to flow through the entire circuit of each solar panel before entering the next one.
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Three solar panels connected in series can be seen in fig.4. Developer, on purpose imported solar panel design of first panel from Fig. 3, with a individual stopper added to the all bottom collector pipes. The main point here is that the top collector pipes are not interconnected and this results in series connection of panels. Every single panel in this configuration can make system work by removing other panels in array.
Flexible ModelGo back and see fig.3
once again. Did there something to worry about?
Yes, See that first panel, it is different from other panels
and so, it's a special one. This needs a different manufacturing method for the first solar panel. To avoid this need fig. 5 will help.
It's interesting little pipe play that can be significant in improving efficiency of the panel and also keeping installation cost with risk involved, in check.
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