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. ;-)
B
boxandroof15 Feb 2019 10:36Preliminary remark: Sorry if I don’t address the collector question. I believe this technical issue is premature and I would suggest reviewing the entire project as a whole in your position.
What others do is not always appropriate, and this is often the case with solar thermal systems. If you want to upgrade your roof and do something meaningful, I would cover the east and west sides with photovoltaic panels. Morning sun, evening sun, midday sun. Photovoltaics pay for themselves financially through feed-in tariffs or savings. You can use the electricity for all sorts of purposes, including heating water with a storage tank. The latter is mentioned just as a thought aid, but it is not really practical.
Solar thermal can make sense with DIY work and as a replacement for electric water heating, as in your case. However, I would weigh it against other measures such as photovoltaics, energy consulting, or heating optimization.
That doesn’t make sense. Either do it completely or not at all. Research yields in advance (see above). What will you do with the storage tank if your experiment doesn’t succeed? That’s very poor environmental practice.
Does your heating system have such high losses that it’s reasonable to use expensive electricity for hot water in summer? If you ever replace your heating system, solar thermal might limit your options or cause additional costs. For the next heating system, I would plan hot water production for summer operation or compare it against solar thermal, which means the savings (compared to electric hot water) will be much lower.
Calculate how much you could save at best with an ideal south-facing orientation before proceeding further.
Example calculation (rough amateur estimate, please use your own numbers):
1. €3300 investment = €800 hot water storage + €1500 collectors + €500 accessories + possibly €500 solar-compatible instantaneous water heater
2. €200 annual electricity cost in summer for hot water production
€3300 / €220 per year = 17 years. That means from year 17 onward it starts to pay off, assuming no defects or maintenance costs. As said, just an example; your result might be 5 or 100 years.
A west-facing orientation can still provide sufficient yields, just check other forums online.
No, he wants to install solar thermal on the roof. This is much less sensible than photovoltaics for electricity generation.
Or do you mean me? Yes, I would do that in his position.
Höhlenmensch schrieb:
In terms of environmental concerns and cost-saving measures, I see many upgraded roofs, which leads me to think that I should also act somewhat future-oriented.
What others do is not always appropriate, and this is often the case with solar thermal systems. If you want to upgrade your roof and do something meaningful, I would cover the east and west sides with photovoltaic panels. Morning sun, evening sun, midday sun. Photovoltaics pay for themselves financially through feed-in tariffs or savings. You can use the electricity for all sorts of purposes, including heating water with a storage tank. The latter is mentioned just as a thought aid, but it is not really practical.
Solar thermal can make sense with DIY work and as a replacement for electric water heating, as in your case. However, I would weigh it against other measures such as photovoltaics, energy consulting, or heating optimization.
Höhlenmensch schrieb:
Since I am an experienced DIY builder with skills in all trades, I want to set up a collector, connect it to a storage tank, and test on different sunny days how and to what extent I can produce my shower water more cost-effectively. If the results are positive, I can install a larger system on my entire roof.
That doesn’t make sense. Either do it completely or not at all. Research yields in advance (see above). What will you do with the storage tank if your experiment doesn’t succeed? That’s very poor environmental practice.
Höhlenmensch schrieb:
In summer, my heating system (oil) is off and I heat water electrically to shower.
Does your heating system have such high losses that it’s reasonable to use expensive electricity for hot water in summer? If you ever replace your heating system, solar thermal might limit your options or cause additional costs. For the next heating system, I would plan hot water production for summer operation or compare it against solar thermal, which means the savings (compared to electric hot water) will be much lower.
Höhlenmensch schrieb:
Unfortunately, I don’t have a south-facing roof available for installation, which is why I am skeptical whether the effort is worthwhile.
Calculate how much you could save at best with an ideal south-facing orientation before proceeding further.
Example calculation (rough amateur estimate, please use your own numbers):
1. €3300 investment = €800 hot water storage + €1500 collectors + €500 accessories + possibly €500 solar-compatible instantaneous water heater
2. €200 annual electricity cost in summer for hot water production
€3300 / €220 per year = 17 years. That means from year 17 onward it starts to pay off, assuming no defects or maintenance costs. As said, just an example; your result might be 5 or 100 years.
Höhlenmensch schrieb:
Manufacturers and installation companies always claim it’s worthwhile, even if only a cup of warm coffee comes out in the end.
A west-facing orientation can still provide sufficient yields, just check other forums online.
Nordlys schrieb:
You seriously want to put solar panels on an old building with an oil heating system?!
No, he wants to install solar thermal on the roof. This is much less sensible than photovoltaics for electricity generation.
Or do you mean me? Yes, I would do that in his position.
Höhlenmensch15 Feb 2019 12:12Thank you for the partly detailed answers and suggestions.
Regarding the suggestions about photovoltaic systems, I can only say that photovoltaics is not an option for me.
I have conducted extensive research in the photovoltaic sector and concluded that, in my opinion (personal opinion), it is not cost-effective. When considering all factors, there are additional costs beyond the prices offered by companies. (Degradation of panels’ performance year by year, loss of efficiency due to dirt accumulation, additional issues with electricity buyback due to differing conditions from power producers (my case Berlin-Vattenfall), switching providers because of electricity prices, meter installations with extra lightning protection measures, varying efficiencies of inverters, self-consumption times (if the sun is shining during the day, my electricity demand is at its lowest), if battery storage is used – including maintenance and lifespan... etc.)
A precise calculation, which does not overly simplify but includes all actual costs, led me to an amortization time of about 15 years, which made me abandon the project!
That is why I switched to solar-assisted hot water generation.
As mentioned earlier, the oil heating is switched off in summer. My 80-liter (21-gallon) hot water boiler is heated once with 3 kW and then provides hot water for the entire day.
The solar support is intended only as an additional aid, which I want to test first. Measuring and control technology is not a problem for me, and I already have a small storage tank and installation materials for the trial.
So, in summary: photovoltaics, no!
Solar thermal collector, maybe yes, if a west-facing orientation delivers enough performance.
I will determine the performance experimentally over several days (clear, cloudy, dull, cold) and see what hot water temperatures I can achieve. I can then extrapolate this to a larger system on the roof to decide whether I want to go ahead with it.
This leads to the core question of this thread: flat plate or evacuated tube collector?
Does the tube collector deliver “significantly” more performance, even with diffuse west sunlight?
I am willing to invest in one collector for the trial (if it does not meet my expectations, you will find my collector special offer on E-Bay).
The statement “gas or nothing” I have already heard from suppliers, who, by the way, congratulated me saying that after 10 years at Easter, I would have golden eggs in the nest.
Greetings from the hot water user who, unfortunately, has become a skeptic over the years :-)
Regarding the suggestions about photovoltaic systems, I can only say that photovoltaics is not an option for me.
I have conducted extensive research in the photovoltaic sector and concluded that, in my opinion (personal opinion), it is not cost-effective. When considering all factors, there are additional costs beyond the prices offered by companies. (Degradation of panels’ performance year by year, loss of efficiency due to dirt accumulation, additional issues with electricity buyback due to differing conditions from power producers (my case Berlin-Vattenfall), switching providers because of electricity prices, meter installations with extra lightning protection measures, varying efficiencies of inverters, self-consumption times (if the sun is shining during the day, my electricity demand is at its lowest), if battery storage is used – including maintenance and lifespan... etc.)
A precise calculation, which does not overly simplify but includes all actual costs, led me to an amortization time of about 15 years, which made me abandon the project!
That is why I switched to solar-assisted hot water generation.
As mentioned earlier, the oil heating is switched off in summer. My 80-liter (21-gallon) hot water boiler is heated once with 3 kW and then provides hot water for the entire day.
The solar support is intended only as an additional aid, which I want to test first. Measuring and control technology is not a problem for me, and I already have a small storage tank and installation materials for the trial.
So, in summary: photovoltaics, no!
Solar thermal collector, maybe yes, if a west-facing orientation delivers enough performance.
I will determine the performance experimentally over several days (clear, cloudy, dull, cold) and see what hot water temperatures I can achieve. I can then extrapolate this to a larger system on the roof to decide whether I want to go ahead with it.
This leads to the core question of this thread: flat plate or evacuated tube collector?
Does the tube collector deliver “significantly” more performance, even with diffuse west sunlight?
I am willing to invest in one collector for the trial (if it does not meet my expectations, you will find my collector special offer on E-Bay).
The statement “gas or nothing” I have already heard from suppliers, who, by the way, congratulated me saying that after 10 years at Easter, I would have golden eggs in the nest.
Greetings from the hot water user who, unfortunately, has become a skeptic over the years :-)
W
wurmwichtel15 Feb 2019 12:30Höhlenmensch schrieb:
...
I have conducted extensive research in the photovoltaic sector and concluded that, in my personal opinion, it is not cost-effective. When considering all factors (...) periods of self-consumption (when the sun shines during the day, I need very little electricity), if own storage is used via battery systems—their maintenance and lifespan....etc...... Solar thermal (ST) has the same problem:
If you don’t need it, you don’t know where to put the heat, and when you urgently need it, none is available.
To put this into numbers from a photovoltaic system (which can be almost directly transferred to solar thermal):
In June, with sunshine, measured output at noon was 9.8 kW (daily amount ~80–100 kWh)
In December, with sunshine, measured output at the same time: 0.6 kW (daily amount 2–3 kWh)
The disadvantage of solar thermal is that you can only use the heat yourself. Photovoltaics, on the other hand, can sell excess energy and are therefore more economical.
N
nordanney15 Feb 2019 12:52Höhlenmensch schrieb:
If you consider all factors, there are several additional costs beyond the prices offered by companies. (Decreasing performance of the collectors year by year, reduction due to dirt buildup, additional issues with feed-in tariffs because of varying conditions among power producers (I am referring to Berlin-Vattenfall), switching providers due to electricity prices, meter installations with extra lightning protection measures, different efficiencies of inverters, self-consumption times (when the sun shines during the day, I need the least amount of electricity) Then you are not fully informed. From my own experience (south/west/southwest orientation): payback period is just under 8 years. 10-year warranty on 85% performance as well as on the inverter. The problem with feed-in tariffs: it does not exist, because there are legal regulations in place. Lightning protection is not necessary, why should it be? By the way, you can influence self-consumption yourself: for example, do not run the washing machine, dryer, or dishwasher at night.
Höhlenmensch schrieb:
Water collector possibly yes, if the west orientation provides sufficient output. The effectiveness is even lower there, since you have an abundance of warm water in summer (you can’t shower or bathe that often) and in winter it doesn’t really work.
I believe you are not going to be convinced anyway, although basically every answer here says: Choose photovoltaics and not solar thermal.
8 years is already quite good. I usually expect around 10 years, but 15 is quite unrealistic...
Nowadays, a 25-year performance warranty is quite common, and if the inverter breaks, the cost is not that high. To operate a photovoltaic system at a loss, you really have to be severely overcharged when getting a quote.
Nowadays, a 25-year performance warranty is quite common, and if the inverter breaks, the cost is not that high. To operate a photovoltaic system at a loss, you really have to be severely overcharged when getting a quote.
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