Simple solar thermal

[Jilly]

I love this simple solar thermal kit that really doesn't look to shabby. Conventional ones are a silly price.

 

https://www.solariskit.com/store

 

[SteamyTea]

Was a podcast on the Beeb about it the other day.

 

Hopefully @Onoff will print us one up.

[joe90]

I have loads of UFH pipe left over, shame it’s not black 🤷‍♂️

[Radian]

51 minutes ago, Jilly said:

I love this simple solar thermal kit that really doesn't look to shabby. Conventional ones are a silly price.

 

https://www.solariskit.com/store

 

Thanks for posting this up. Interesting to see a company making a product that's not far removed from the DIY versions we've discussed on here. I've been thinking about what you could do with black PVC conduit, 90^o elbows and solvent weld to make a serpentine flat panel absorber. 

[joe90]

I think the problem with all wet solar systems are integrating them into the house plumbing, fine fir a hot tub etc. I discounted them in favour of PV a long time ago (but still to get round tuit 🙏👀)

[SteamyTea]

43 minutes ago, joe90 said:

I have loads of UFH pipe left over, shame it’s not black 🤷‍♂️

Spray can of matt black and it soon will be.

 

I have often thought that it woud be worth fitting UFH, with aluminium spreader plates, under the roof time.

Well, worth it till it leaks.

[JohnMo]

1 hour ago, Jilly said:

I love this simple solar thermal kit that really doesn't look to shabby. Conventional ones are a silly price.

 

https://www.solariskit.com/store

 

I looked at those and for a house need quite a few, which ended up being quite expensive.

[Radian]

44 minutes ago, joe90 said:

I think the problem with all wet solar systems are integrating them into the house plumbing, fine fir a hot tub etc. I discounted them in favour of PV a long time ago (but still to get round tuit 🙏👀)

Agreed. However, I was thinking of using it to heat some water for a workshop sink using gravity. Just a small amount at a time for hand washing after working on the car.

[joe90]

33 minutes ago, SteamyTea said:

I have often thought that it woud be worth fitting UFH, with aluminium spreader plates, under the roof

My workshop metal roof is scorching hot, shame to waste that heat, however hopefully I will cover it In PV soon.

[SteamyTea]

16 minutes ago, joe90 said:

My workshop metal roof is scorching hot, shame to waste that heat, however hopefully I will cover it In PV soon.

Be interesting to know what the temperate differene is between PVed and unPVed roofs.

Maybe a project for when you get it fitted as I am ausre there will be a bit that is not covered.

[joe90]

4 minutes ago, SteamyTea said:

Maybe a project for when you get it fitted

A concern I have is I know PV panels loose efficiency when they get hot, so are panels less efficient over a tin roof than a clay or concrete roof? 🤷‍♂️

[Pocster]

3 minutes ago, joe90 said:

A concern I have is I know PV panels loose efficiency when they get hot, so are panels less efficient over a tin roof than a clay or concrete roof? 🤷‍♂️

You would assume so . I’m sure I read in a few places once temperature starting exceeding 25degs you lose 1% efficiency per degree . Tbh the efficiency downgrade must be minimal. By 11am in the current weather I’m almost maxing out my PV generation anyway . 

[Onoff]

As I've said before the Yanks have been using pex to make bfo collectors for years.

 

https://www.builditsolar.com/Projects/PoolHeating/TomCollector/TomPEXCollector.htm

[SteamyTea]

59 minutes ago, joe90 said:

A concern I have is I know PV panels loose efficiency when they get hot, so are panels less efficient over a tin roof than a clay or concrete roof

Probably not.

You have to look at the raised temperature in conjunction with the extra radition that they are getting.

We tend not to get exessive temperatures without excessive radiation in the UK (thare are odd exceptions where a wind blows over a mountain and, as it falls to Earth, compresses the air and heats it up).

So if a module is tested a 20% converstion efficency, at 25°C anC d at 800 W/m², and for every 1°C above that it looses 0.5%, at 35,you get 138 W/m² of electricity.

If you tested it at 35°C, but at 1000 W/m², you get 171 W/m² out.

 

(not exact figures, but highlights how the 'efficiency' is measured)

 

The other thing is that during those fairly rare high temperature events, you don't need much electricity.

Edited August 14, 2022 by SteamyTea

[Radian]

1 hour ago, joe90 said:

A concern I have is I know PV panels loose efficiency when they get hot, so are panels less efficient over a tin roof than a clay or concrete roof? 🤷‍♂️

 

But the roof is in shade so as long as there's an air gap under the modules, it's pretty much irrelevant what they mounted on. I saw some pwople were experimenting with water cooling PV to increase output. Not a realistic proposition I would think although it did seem to gain a little.

[Wil]

I've just been up on the roof scrubbing my solar panels. They were filthy after the farmer's harvesting around us coated them in dust but I still don't get much improvement in performance. They're on a tin roof and my 5kWp of panels is maxing out at about 4kWp during this hot weather. It's really irritating that there's a 20% loss in performance when they get warm. They are on a tin roof and it's cooking* hot up there though.

 

* This being a standard unit of temperature somewhere after 'really' and before 'nuclear'...

Edited August 14, 2022 by Wil

[SteamyTea]

21 minutes ago, Wil said:

really irritating that there's a 20% loss in performance when they get warm.

Is it just the temperature, it could be the altitude and azimuth of the sun.

There is also turbidity in the atmosphere.

Often the reason the modules seem to perform better in the spring and autumn is not temperature, just the altitude of the sun is the same as the roof pitch at noon.

Edited August 14, 2022 by SteamyTea

[Onoff]

38 minutes ago, Wil said:

I've just been up on the roof scrubbing my solar panels. They were filthy after the farmer's harvesting around us coated them in dust but I still don't get much improvement in performance. They're on a tin roof and my 5kWp of panels is maxing out at about 4kWp during this hot weather. It's really irritating that there's a 20% loss in performance when they get warm. They are on a tin roof and it's cooking* hot up there though.

 

* This being a standard unit of temperature somewhere after 'really' and before 'nuclear'...

 

Could you use some of the panel output to power a fan, blowing air under the panels. Would that cut it down to say 10% loss overall?

[Radian]

50 minutes ago, SteamyTea said:

Often the reason the modules seem to perform better in the spring and autumn is not temperature, just the altitude of the sun is the same as the roof pitch at noon.

Agreed. Altitude of Sun for 51^o 30'N (London) astro.ukho.gov.uk:

 

 

So for the modules to be perpendicular to the Sun on during the Summer Solstice in London they should be inclined at about 28^o whereas  for the Winter Solstice they should be at 75^o to get maximum output when facing South at midday. Anything less than perpendicular will create a loss. So for a 45^o pitch roof, April/September will give best results.

[Radian]

32 minutes ago, Onoff said:

 

Could you use some of the panel output to power a fan, blowing air under the panels. Would that cut it down to say 10% loss overall?

Being realistic, given the slightest breeze, far more air will be circulating than you could create over such a large area with a fan. Much better to use a hybrid thermal/PV panel to shift cold water in one end and hot out the other.

 

(he says trying to get the thread vaguely back on topic)

Edited August 14, 2022 by Radian

[Pocster]

Simple solar thermal .

You put a full paddling pool out in the sun for your grandson early in the morning.

He never uses it .

Simple solar thermal ffs!

[Wil]

My panels are about 30 degrees inclined and just W of South, so I usually see peak power in the 1-3pm zone. Having cleaned the panels, the only thing I can think of is either atmospheric (it's clouded over this afternoon) or the heat degrading performance. I have seen the panels hit 5kWp previously in cooler temps, but this tends to be between clouds. Hard to tell if they can sustain it as the sustained sunshine seems to come with some excess heat!

 

I'd love to try the simple solar thermal, and yes, the paddling pool has been out all day and the only users seem to be the bees. Who then need rescued.

[SteamyTea]

1 hour ago, Radian said:

Agreed

I should have added that is peak power, not peak generation.

Dare I mention kW (power) and kWh (energy, or in this case generation).

 

[Radian]

48 minutes ago, SteamyTea said:

I should have added that is peak power, not peak generation.

Dare I mention kW (power) and kWh (energy, or in this case generation).

 

 

You may have noticed that I avoided any specific quantification because it depends on the goal. If trying to burn through a safe door with a PV powered plasma cutter, maximising kW may be more important than kWh. Particularly if you want a quick getaway.

[SteamyTea]

5 minutes ago, Radian said:

trying to burn through a safe door with a PV powered plasma cutter

That's where you are going wrong.