I don’t want to start a fundamental debate with technical comparisons here, but just ask a question that arises from my laziness … (researching is quite extensive—and the more you learn, the more complicated it gets).
I’ve already looked at the documentation from different companies and noticed that tube vacuum collectors tend to be in a higher price range than conventional flat-plate collectors.
Looking at the technical data, I feel like I need to study it all over again.
To explain: I want to start by trying out a collector that I install myself to see how much hot water I can generate. Then, multiplying that and implementing it on a larger scale in a professional installation should allow me to calculate in advance what the whole thing would cost, which shouldn’t be a problem.
So far, I am quite skeptical about the payback calculations I have seen. (–When thinking about photovoltaics, I already gave up for this reason.)
My problem is that the pitch of my gable roof faces DIRECTLY west.
Is that even enough to make the investment worthwhile?
The tube collector is supposed to perform better in this respect, as it can make better use of side radiation.
But when I look at the efficiency figures from the companies, I notice that for differences of around 7%, they act like one system is boiling the water and the other is almost cooling it ;-)
Has anyone had experience if the better sensitivity to side radiation really provides a significant advantage?
In the long run, the flat-plate collector is probably simpler than the tubes, since I see that spare parts are also offered for the tubes ?! – For me, this raises the question: does the vacuum degrade? After how long?
Even though this is a trial, I would prefer not to set up two test installations.
Thanks in advance for any tips,
a believer in the wisdom of the crowd. ;-)
I’ve already looked at the documentation from different companies and noticed that tube vacuum collectors tend to be in a higher price range than conventional flat-plate collectors.
Looking at the technical data, I feel like I need to study it all over again.
To explain: I want to start by trying out a collector that I install myself to see how much hot water I can generate. Then, multiplying that and implementing it on a larger scale in a professional installation should allow me to calculate in advance what the whole thing would cost, which shouldn’t be a problem.
So far, I am quite skeptical about the payback calculations I have seen. (–When thinking about photovoltaics, I already gave up for this reason.)
My problem is that the pitch of my gable roof faces DIRECTLY west.
Is that even enough to make the investment worthwhile?
The tube collector is supposed to perform better in this respect, as it can make better use of side radiation.
But when I look at the efficiency figures from the companies, I notice that for differences of around 7%, they act like one system is boiling the water and the other is almost cooling it ;-)
Has anyone had experience if the better sensitivity to side radiation really provides a significant advantage?
In the long run, the flat-plate collector is probably simpler than the tubes, since I see that spare parts are also offered for the tubes ?! – For me, this raises the question: does the vacuum degrade? After how long?
Even though this is a trial, I would prefer not to set up two test installations.
Thanks in advance for any tips,
a believer in the wisdom of the crowd. ;-)
Höhlenmensch17 Feb 2019 22:52@boxandroof-Thanks for the additional tip. At first, because of the suspicious name, I actually thought "Guerilla Photovoltaics" was a joke.
I clicked on it anyway and found it interesting. Apparently, you can start small, which is appealing for "DIY enthusiasts."---I will do some research.
@nordanney-...I do understand that in winter, you can't expect warm collector water, while photovoltaic panels can still be useful in that case.
Of course, everything eventually pays off.
The key question for most users is always the payback factor, which is individually different regardless of the actual time frame.
If I’m an "environmentalist" (not meant negatively), I don’t care about the time and I know I’m ahead of my time in a good way, so I’m willing to open my wallet today.
Others look at their bank account and wonder, "What happens in 10 years?" and prefer to sit in the garden with friends, popping open some bottles of champagne "Chateau Lafite Rothschild south-facing" (the one with the earthy finish) ;-) instead of investing in the future.
Besides, you have to have the means. Many who have these systems installed unchecked in their new homes will realize after a while that some repayments can be quite difficult, and the money machine doesn’t always run smoothly. (Hopefully, the offers weren’t time-limited and won’t be adjusted again after a few years—this has happened before.)
Who knows what tomorrow will bring? (At the moment, our "peace angels" are itching to cancel contracts again and upgrade as quickly as possible, but that’s not relevant here.)
Heat or electricity, which none of us want to do without, is a vast topic.
I have also researched heat pumps and micro combined heat and power units in parallel, which overall leads to my skepticism.
If you want to compare everything properly (air/water heat pumps / deep drilling / shallow burial – micro combined heat and power units – electricity/heat – flat plate / tube solar collectors), you’d better be retired and have enough time to make a sensible decision. (If retired, not with a "minimum pension"—sorry for the pun.)
The information I have gathered from “specialist companies” in the past mostly turned out to be problematic.
For example, check out the "free energy consultations"—they 100% always lead to the advisors having our data and being inside the home. These are professionals working on commission. This is not a criticism since we all work for money, but from my experience, I can only question how optimal and accurate all their statements are.
That’s why my original post and plan for a small trial entry.
Sorry for the long text, but the admin will probably overlook it since storage space is not a big issue nowadays.
Best regards from SKF (FutureSkepsisMan), with the small trial entry :-)
I clicked on it anyway and found it interesting. Apparently, you can start small, which is appealing for "DIY enthusiasts."---I will do some research.
@nordanney-...I do understand that in winter, you can't expect warm collector water, while photovoltaic panels can still be useful in that case.
Of course, everything eventually pays off.
The key question for most users is always the payback factor, which is individually different regardless of the actual time frame.
If I’m an "environmentalist" (not meant negatively), I don’t care about the time and I know I’m ahead of my time in a good way, so I’m willing to open my wallet today.
Others look at their bank account and wonder, "What happens in 10 years?" and prefer to sit in the garden with friends, popping open some bottles of champagne "Chateau Lafite Rothschild south-facing" (the one with the earthy finish) ;-) instead of investing in the future.
Besides, you have to have the means. Many who have these systems installed unchecked in their new homes will realize after a while that some repayments can be quite difficult, and the money machine doesn’t always run smoothly. (Hopefully, the offers weren’t time-limited and won’t be adjusted again after a few years—this has happened before.)
Who knows what tomorrow will bring? (At the moment, our "peace angels" are itching to cancel contracts again and upgrade as quickly as possible, but that’s not relevant here.)
Heat or electricity, which none of us want to do without, is a vast topic.
I have also researched heat pumps and micro combined heat and power units in parallel, which overall leads to my skepticism.
If you want to compare everything properly (air/water heat pumps / deep drilling / shallow burial – micro combined heat and power units – electricity/heat – flat plate / tube solar collectors), you’d better be retired and have enough time to make a sensible decision. (If retired, not with a "minimum pension"—sorry for the pun.)
The information I have gathered from “specialist companies” in the past mostly turned out to be problematic.
For example, check out the "free energy consultations"—they 100% always lead to the advisors having our data and being inside the home. These are professionals working on commission. This is not a criticism since we all work for money, but from my experience, I can only question how optimal and accurate all their statements are.
That’s why my original post and plan for a small trial entry.
Sorry for the long text, but the admin will probably overlook it since storage space is not a big issue nowadays.
Best regards from SKF (FutureSkepsisMan), with the small trial entry :-)
I have both solar thermal and photovoltaic systems—and I’m not a fan of this “either-or” debate.
Both have their pros and cons (especially if you don’t have a heat pump as your heating system; with a heat pump, you can skip solar thermal and rely fully on photovoltaics). I could easily write pages about this, but my child is asking to be put to bed ;-)
So now I’ll briefly address the ORIGINAL QUESTION from the OP (I think I’m the only one in this thread doing so):
If you go for solar thermal, choose a vacuum tube collector. It’s a bit more expensive but significantly better and more efficient. Especially when the sun hits the collector at an angle or from the side, vacuum tubes deliver MUCH better results thanks to their parabolic mirrors—also during transitional seasons.
Both have their pros and cons (especially if you don’t have a heat pump as your heating system; with a heat pump, you can skip solar thermal and rely fully on photovoltaics). I could easily write pages about this, but my child is asking to be put to bed ;-)
So now I’ll briefly address the ORIGINAL QUESTION from the OP (I think I’m the only one in this thread doing so):
If you go for solar thermal, choose a vacuum tube collector. It’s a bit more expensive but significantly better and more efficient. Especially when the sun hits the collector at an angle or from the side, vacuum tubes deliver MUCH better results thanks to their parabolic mirrors—also during transitional seasons.
A brief addendum: You won’t be able to run a heat pump or an electric heating element for hot water with just a small guerrilla photovoltaic setup... you need significantly more photovoltaic capacity than just one or two modules for that... and personally, I wouldn’t risk installing something like that illegally on the roof.
S
Stefan89020 Feb 2019 20:37Our general contractor would have preferred to install solar thermal systems. Why? Because that’s what he has always done so far.
In principle, there is nothing wrong with solar thermal, as long as the investment is low. Our energy consultant calculated the annual savings for our case: about 120€/year. It would therefore take 100 years to recoup the investment costs.
Now we are planning a photovoltaic system, where the payback period is about 10 years.
In principle, there is nothing wrong with solar thermal, as long as the investment is low. Our energy consultant calculated the annual savings for our case: about 120€/year. It would therefore take 100 years to recoup the investment costs.
Now we are planning a photovoltaic system, where the payback period is about 10 years.
ST has an additional cost of around 2800 gross. With savings of 120 euros per year, that amounts to just over 20 years, not 100. You are right, if you really do the math, all the eco-friendly stuff is not economically worthwhile, but the energy-saving regulations nevertheless apply.
G
Grundbuch10 Apr 2019 08:40A bit late, but I hope this still helps. I have had 4.4 m² (47 sq ft) of evacuated tube collectors facing east for 15 years, combined with geothermal for a 300-liter (80-gallon) tank. When the sun is shining, the boiler heats up fairly quickly; in winter, the temperature only reaches about 30-35°C (86-95°F), which is too low for showering. If I had 20 collectors, I could have 3000 liters (800 gallons) at 30°C (86°F), but that would still be pointless. Your 80 liters (21 gallons) is far too little—just enough for one shower—and it would be fully used up by even a small collector. After 10 years, I had one defect: scaling, but luckily I was able to fix it myself without scaffolding. So, evacuated tubes around 4 m² (43 sq ft) combined with a larger tank (300-500 liters / 80-130 gallons), or guerrilla systems and heat pump boilers.
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