Solar tubes questions

The_B_Man · 02-08-2019 10:13pm #1

I had a salesman offer me some tubes for 5k (after the €1250 grant & being a special customer etc). Said the tubes are top quality from Germany. He said 15 on the back, and 15 on the front, as my house is at an awkward angle.

I never heard of the company but they seem to be on the SEAI website. So I said I'd go ahead with the install.

Kinda having second thoughts now.

Firstly, I get the impression I'm paying over the odds and paying the salesmens salaries. If I'm only paying about 500 over, I'd just go ahead with it for the sake of convenience tbh. Plus I currently have a very awkward setup, due to a bogey plumber, whereby my boiler and cylinder basically need to be moved. As part of a solar install, they'd potentially both go into the attic (or maybe just the new cylinder), which is what I want, and probably would have done anyway in a few years.

Secondly, my current heating system is new (~1 year) and fairly efficient. Probably €800 a year as an estimate on heating. This will probably increase repayment to 15 years. I might offset some of it by selling the old 150L cylinder. I'd probably get 200-300.

Thirdly, am I being picky to not want these tubes on the front of my house?

Finally, it seems that I underestimated the maintenance. Am I right in thinking I need to keep an eye on the coolant to make sure it never goes over 135C? Also I've to change it every 3 years as well? (Your man said 10 years!).

The only positives I see are a) I get my cylinder and boiler moved out of sight, and b) I think solar is "cool", and c) its "green".

So should I cancel?
IF I go ahead, what should I keep an eye on with the installers?

Thanks.

n97 mini · 03-08-2019 12:24am

My neighbour got solar thermal fitted two weeks ago. She claims it cost her 9k (40 year old 3 bed semi, so tank would need to be replaced etc.) Now, putting the immersion on for an hour a day on full day rate she'll get payback in 61 years. That's not counting servicing.

Sounds like you'll do better though. Maybe a 34 year payback? Or closer to 70 if you switch to night rate electricity.

I'm being a bit facetious, but I honestly can't see any economic reason to install solar thermal. Go PV instead.

ted1 · 03-08-2019 12:28am

Tubes are oh no use , get solar PV and a divertir. Tubes give hot water. Most of which is dumped and th dumped heat isn’t taking into consideration for pay back periods

The_B_Man · 03-08-2019 9:26am

OK I didn't know tubes had such a bad reputation. I thought they were preferred over PV due to their 95% efficiency compared to 22%.

I was considering PV but the efficiency % put me off. I figured it'd be like any technology and that would increase in a few years and I'd be raging I got it in.

I'm hoping I can cancel these tubes now since I haven't paid the deposit, just signed a few forms.

Calahonda52 · 03-08-2019 11:34am

The_B_Man wrote: »

OK I didn't know tubes had such a bad reputation. I thought they were preferred over PV due to their 95% efficiency compared to 22%.

I was considering PV but the efficiency % put me off. I figured it'd be like any technology and that would increase in a few years and I'd be raging I got it in.

I'm hoping I can cancel these tubes now since I haven't paid the deposit, just signed a few forms.

Tubes don't have a bad reputation.

You need to understand the basis of the efficiency calculations: the limit in PV is down to the science of the silicon chips, aka a physical limitation which will not be changing any time soon.
https://en.wikipedia.org/wiki/Solar_cell_efficiency
for the full treatment

As for 95% for thermal, its BS without knowing the basis of the calculation.
http://www.apricus.com/html/solar_collector_efficiency.htm#.XUVhiS0ZMkg

Thermal is useful iff you have the use for the hot water and don't have to dump the excess heat. The sizing for domestic applications is predicated on a daily usage of hot water.

My preferred option for thermal is with a thermal store, which can then be used with a heat pump, amongst other things

unkel · 04-08-2019 2:11am

n97 mini wrote: »

My neighbour got solar thermal fitted two weeks ago. She claims it cost her 9k .

LOL, let me guess a con pany with the number 8 in its name?

Solar thermal tubes are a far more efficient way to heat your water than solar PV. But things are a bit more complicated these days if you are talking money.

Back a few years ago there was no subsidy on solar PV and there was a €1300 subsidy on solar thermal. It made sense to go solar thermal if you used lots and lots of hot water, like myself. We needed to get our cylinder replaced anyway, so that reduced the ROI on the system substantially.

These days that subsidy is still there but there is now also a massive €3,800 subsidy on PV. And the cost price of the parts of solar PV has dropped dramatically since too.

If I had no solar at all today, I would go for a large solar PV system, if over 4kwp with a diverter. I would not go solar thermal

The_B_Man · 04-08-2019 9:28am

If your house was facing south west would you get solar at all, knowing you'll need a panel on front and back of your house which will only be used half the time? As in, back one used in the morning, front one used in the evening.

db · 04-08-2019 9:55am

The_B_Man wrote: »

If your house was facing south west would you get solar at all, knowing you'll need a panel on front and back of your house which will only be used half the time? As in, back one used in the morning, front one used in the evening.

I have 30 tubes on a south facing roof heating a 300L cylinder. This provides most of my hot water from April to September, about 50% March ch and October and a small bit the other months. On your roof you won't get anywhere near this. I can't see where the benefit is at all.

n97 mini · 04-08-2019 8:51pm

unkel wrote: »

LOL, let me guess a con pany with the number 8 in its name?

The van was out the front. I didn't recognise the name of the company but I don't think it had any numbers in the name.

Tbh I don't believe her. She's the kind of person who likes to tell people how much she spends, and would just as easily tell you she spent 40k on a car that is only 32k new (she buys brand new every 2 years).

I think solar thermal has use cases but in a 3 bed semi with a gas boiler, it's very limited. Like you said, PV is the way to go.

The_B_Man · 04-08-2019 10:25pm

Ye OK I think I'll ring them Tuesday and see if I can cancel.
They said they'd be taking the deposit out then, so hopefully the stuff I signed wasn't too binding!!

ted1 · 05-08-2019 3:54pm

The_B_Man wrote: »

OK I didn't know tubes had such a bad reputation. I thought they were preferred over PV due to their 95% efficiency compared to 22%.

I was considering PV but the efficiency % put me off. I figured it'd be like any technology and that would increase in a few years and I'd be raging I got it in.

I'm hoping I can cancel these tubes now since I haven't paid the deposit, just signed a few forms.

Fuel is free so efficiency isn’t relevant.

Calahonda52 · 05-08-2019 5:11pm

ted1 wrote: »

Fuel is free so efficiency isn’t relevant.

.
Not entirely, depending on energy demand and available surface area

ted1 · 05-08-2019 6:42pm

Calahonda52 wrote: »

.
Not entirely, depending on energy demand and available surface area

Demand doesn’t come into it. Space may.

Bottom line PV tubes create heat which is dumped. Many people don’t require 300l of hot water

unkel · 05-08-2019 11:03pm

The latest ruling in the case of the woman who covered the full road facing front of her roof with PV (without PP) was that she was allowed to keep them. This opens the floodgates for anyone who wants to plaster their property with PV. That combined with expected (low) FIT does not work in favour of solar thermal either.

You can heat up many times more water with the same surface area of thermal than you can with PV though, that's just a fact.

ted1 wrote: »

Many people don’t require 300l of hot water

Indeed. We do though. Family of 5 with 4 women. The quote the OP is getting is pretty poor. I paid €4.7k (after hard negotiation) for a high end Kingspan 40 tube system (that vents itself at 95C) with a 360l highly insulated cylinder back in 2016. Considering I had to replace my cylinder anyway I reckon pay back was about 10-12 years compared to heating the water with our newish and highly efficient gas boiler. But that has now increased though as there is more maintenance than I expected. Back then the payback on Solar PV was more like 50+ years. Prices for panels / inverters have been slashed since and we now have a very generous subsidy on PV

rolion · 06-08-2019 12:01am

I love the warriors that blames the solar thermal and praise the solar PVs..i wonder how many of them touched a solar tube element or have them in the house....

In the case of having half of the year hot water at the tap and at the shower,a full 300 litres cylinder heated up from 20ish all the way up to 60ish at least twice a day.
Solar tubes thermal are best anytime and under any competition for one thing: having hot water at the tap summer days and pre-heat the water winter times.

I'm a realist and, as unkel said,with latest PVs grants,it beats the solar tubes in prices, but i am willing to make a deal.
Anyone with PVs and myself with tubes and let's see how that performs over,let's say few weeks...

I start now with 58 degrees top of the cylinder...

unkel · 06-08-2019 2:21am

rolion wrote: »

I love the warriors that blames the solar thermal and praise the solar PVs.

Isn't it funny though that blaming and praising can and should change at an instant? Prices and coming and going subsidies make a huge difference whether a system should be encouraged or not.

An immersion diverter on a 2kwp system last year was a stupid choice. Costing more than it would ever pay back. Now on a 4kwp-6kwp system with a massive subsidy it makes a lot of sense. More sense than a solar thermal system

It is imperative that we are all honest about the financials of renewables. Some of us go renewable at all cost, and praise to the people that do, the world needs them. But I feel we need to be honest so hopefully a lot of people will come on here and install some solar in their homes and have no regrets after.

rolion · 06-08-2019 9:06am

@inkel.

You are right about the prices and grants.

But i hate seing so call facts based on some sort of maths logical rationale... PVs are better at managing hot water because the grants for PVs are better than grants for solar tubes... thats what heats my "cooling agent" over the 37 degrees...

And,i dont know how or why, but i find no longer a no point in wasting my dear electrons generated by the PVs in debating one versus another... same as EVs vs ICEs on other topics, i guess is human nature ...

Either one,good choice and enjoy it...

michealkc · 06-08-2019 7:03pm

unkel wrote: »

The latest ruling in the case of the woman who covered the full road facing front of her roof with PV (without PP) was that she was allowed to keep them. This opens the floodgates for anyone who wants to plaster their property with PV. That combined with expected (low) FIT does not work in favour of solar thermal either.

You can heat up many times more water with the same surface area of thermal than you can with PV though, that's just a fact.

Indeed. We do though. Family of 5 with 4 women. The quote the OP is getting is pretty poor. I paid €4.7k (after hard negotiation) for a high end Kingspan 40 tube system (that vents itself at 95C) with a 360l highly insulated cylinder back in 2016. Considering I had to replace my cylinder anyway I reckon pay back was about 10-12 years compared to heating the water with our newish and highly efficient gas boiler. But that has now increased though as there is more maintenance than I expected. Back then the payback on Solar PV was more like 50+ years. Prices for panels / inverters have been slashed since and we now have a very generous subsidy on PV

What is the subsidy on PV?

unkel · 06-08-2019 8:59pm

rolion wrote: »

You are right about the prices and grants.

But i hate seing so call facts based on some sort of maths logical rationale... PVs are better at managing hot water because the grants for PVs are better than grants for solar tubes

That's the way it is. My EV cost almost €40k gross and there is no way I would have bought it if I had not got €5k subsidy for it. A €5k discount on the VRT. A €4k scrappage scheme and a further negotiated discount. So it cost me €25k, which was similar to a similar size reasonable spec Skoda Octavia. And then the savings began...

Without these subsidies I would still be driving an old petrol car.

michealkc wrote: »

What is the subsidy on PV?

You get €700 subsidy per installed kwp of solar PV for the first 2kwp, and if you go above 2kwp you only get another €700 subsidy per kwp for the next 2kwp if you have a battery installed. That attracts a further €1000 subsidy

So on a 2kwp system you get €1,400
on a 4kwp and above system with a battery you get €3,800

Very, very generous.

Solar tubes questions

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