Haven't read all of the way through but we should probably start here.

https://ieeexplore.ieee.org/document/9143083

Not just Amazon, Walmart is now suing Tesla over solar panel fires https://www.solarreviews.com/blog/solar-home-energ...

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

There was discussion here recently about a Walmart fire in Indiana. Wonder if that one is part of the lawsuit.

https://www.eng-tips.com/viewthread.cfm?qid=492974

I would like to hope they give a reason why they went on fire.

Turning them off doesn't really help if its the panels that are going on fire. You would have to cover them otherwise they will just sit at max Voltage and be able to produce max current @12 amps when a fault occurs. Wiring issues they can still produce and feed the flames.

Seems it was issues with the MC4 connectors which because all Tesla installations use optimisers even if there is not shading issues means they have 4 times as many connections compared to clean strings.

The MC4 are crimped and not soldered apparently. And they are solid tube crimp. Not fold over crimp.

And we're fitted onsite by contracted installers.

Just checked my panels and they have german sprung loaded cable grips inside them over a s grip. Which I presume allows thermal moving of wire strands and no arc gaps being produced.

Did a search for similar fire events in Europe and there hasn't been any since the regulations about diodes came out.

Crimp connectors are supposed to work by mechanically welding the wires to the connector. It very much depends on proper installation. I believe there are even tools that won't release until you've applied enough compressive force.

In my experience, crimp connectors done properly don't fail.

Soldered connections can "fail" at the melt temperature of the solder. Proper crimp connections fail at the melt temperature of the metals.

Spring-loaded connectors can fail if the springs lose their temper. I've dealt with it a few times.

Hard to believe, I know; but some installers are incompetent.


spsalso

I would be suspicious of incorrect wire insulation selection before I went after the crimped connectors. Everything uses crimped connectors, they are tried and true. However, running electric wire in a high UV exposure environment such as a rooftop might not register as a special environment to many installers.

From what I've seen on top of houses, the installers put the wire in conduit. So the insulation is not exposed to UV. Perhaps they do things differently on the roofs of Amazon facilities out in wherever.

It looks like there's either a fabrication error of the product, or an installation error by the installers. Which it is, or both, doesn't seem to be showing up.

On the installer's side, it seems to me that if one of his connections failed, the failure is contained inside a junction box. And one or more panels shuts down. I don't see how a giant fire would ensue. That's why junction boxes were "invented".


spsalso

So how hot is it the roof? Maybe 150F plus resistive heating.
And now you put that into conduit so there is no air cooling.
And now you cycle this each day with a soak period.
Better be some pretty good wire insulation.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

"So how hot is it the roof? Maybe 150F plus resistive heating.
And now you put that into conduit so there is no air cooling.
And now you cycle this each day with a soak period.
Better be some pretty good wire insulation."

Typical insulation is rated for 194F. There are higher temp available.

Temperatures of working environments must be included in calculations: various de-rating factors. For example, Table 310.15(B)(2)(a) of the NEC has corrections for ambient temperatures up to 437F.

There is also a correction factor for the number of conductors in the conduit: Table 310.15(B)(3)(a)

Should the insulation still fail, the conductor will be shorted to ground; and a breaker will trip. Any damage will be contained in the conduit.


spsalso

The initial wire runs from the panels to the (switchboard for us generator guys, not sure what solar calls it) are unprotected. Any faults within that intial run are usually catastrophic. If you have ground fault detection you may catch it when the first wire chaffs through.

The initial run of a typical solar panel handles about 300 watts. If there's a failure in that initial run, the panel will either be disconnect from the load by the failure, or it will deliver its full power (300 watts) to the failure point. I am not sure what a relatively small amount of power will cause, but I don't think I'd use the word catastrophic. I could see some metal-melt maybe happening. But consider that it's likely that some of the metal that is melting is the wire delivering the power. And thus the fault may be "self-clearing". I would think it most important not to have ignitable materials nearby.

But start adding panels up, and....

I do agree that the designers of the system should pay attention to "failure to a short". It DOES seem likely that a ground fault system and/or an arc fault system gets appropriate pretty quickly.



spsalso

When I say soldered I was meaning silver soldered which in my limited experience in the oil industry they did on power systems but they were crimp then solder. But this was for explosive gas environments. But realistically that's not going to be used in the field for solar.

USA there seems to be major work and discussions about arcing industry wide and yet another code is likely to be issued for arc suppression systems and detection.
Solar in Europe and Australia it is hardly ever mentioned and seems to be a none issue. I can't work out why its a big problem in one area and absolutely nothing else where. In fact both those areas run much higher voltage strings than the US which is capped at 600V domestically, We are capped at 1000V domestically and the farms run 1500V strings. But already there is political lobbying that we should also change the codes to include it. I presume its linked to single market requirement economics and if the rest of the markets don't need it then it sticks out like sore thumb and increases costs/reduces choice in that market. Plus makes local suppliers uneconomic outside that region.

When I say sprung the wire is fed across a conductor edge and then the sprung part is another edge gripping the wire so it S through between the edges. So when it heats up and the strands move they are kept in contact. I think the main idea is that it can thermal contract and expand and rearrange itself and the contact area doesn't reduce over time. https://www.farnell.com/datasheets/sunclix.pdf

In this case it may not be the crimp but the quality of the male - female connection causing arcing as they seem to be saying it is the connectors from one supplier.

As for the tripping to ground. We don't have fused/breakered strings in Europe. The wire is protected by the max current able to be produced by the panels which is under 13 amps. You can connect a panel directly to ground and a 16 amp fuse/breaker will do absolutely nothing. German inverters have to have a grounding fault detection system. Which works by the grounding of the panels goes back to the inverter and it uses that to work out if all the electrons are going to where they should be. But all it can do is trigger dry switch which can be linked to a audio or visual warning and send you and email/ flag it in the monitoring system. You can't stop the panels producing power unless you block the sunlight.

I think they also reported that they found when they inspected the other installations they found quiet a few of them not grounded at all. So its more than likely revolves round installation errors across a broad range of topics. Tesla seem to have issues with the in roof domestic solar setups as well in the USA but I can't find any reports in Europe. And we don't have the conduit requirements. In fact my strings just go through flexible plastic tube rated at 1500v through the internal walls of my house down to the cellar. USA seems to require most installations to be piped down external walls.

Construction materials may also be a feature, With our consumer units being made out of plastic not metal along with most of our electrical boxes its pretty much normal to use none flammable plastics for components.

I might add this inability to kill power to solar is one of the political lobbying arguments that enphase are trying to use to restrict/ban DC string inverters and only use micro inverters. And of course they hold the bulk of the patents for micro inverter tech. Its a mess of codes and practises. But engineering wise the problems are varied and region specific. The ones that were global they have tackled eg the bypass diodes and panels going on fire.

I don't think Australia is on top of this issue, either. It is reported that about 10% of house fires in Australia are started by rooftop solar. But that could be because domestic installations are done by cowboys.

I couldn't find much for AUS on the subject.

If you have any links I would be interested.

The cowboy issue is rearing its head in the UK there is just so many people trying to get installs at the moment. And a colossal shortage of hardware. The popular brands are 6 months plus lead times. But the brands are restricted for grid tied due to them setting up a cartel qwango of installers/ suppliers which isn't required legally but they have managed to get all the grid DNO's to require it and also house insurance company's. If you have an approved cowboy installer who then walks after a rubbish install of course they will wash their hands of it and say its a civil matter. So 10% price hike for not a lot.

Solder, braze, weld all imply a temperature range. Whether it's lead solder or silver solder, they all melt within a low temp range that's included by the definition of soldering. There is also a silver brazing process often erroneously referred to as solder. This is most familiarly used for joining copper pipe in refrigeration systems. I have never seen electrical connections joined by brazing.

Alistair,

Media reports:

https://theconversation.com/solar-panel-fire-seaso...

https://www.9news.com.au/national/solar-panel-rela...

https://www.abc.net.au/news/2022-06-05/rainfall-an...

There are many more, but these are all domestic installations, not the big commercial fires reported in the US.

"Solder, braze, weld all imply a temperature range. Whether it's lead solder or silver solder, they all melt within a low temp range that's included by the definition of soldering. There is also a silver brazing process often erroneously referred to as solder. This is most familiarly used for joining copper pipe in refrigeration systems. I have never seen electrical connections joined by brazing."

I've heard of the term "brazing", but never used it or heard anyone else apply the term. Up until now, my understanding has been that it refers to a joining of two metals using a brass alloy. I've never seen it done.

I have done work called "soldering" by all concerned with the task.

There was what I would call "soft soldering", typically using a lead-tin alloy that can be melted by a hot iron. This would be in the range of 600F-700F. I have typically used it in electronics.

And there was "hard soldering". Also called "silver soldering", since it uses an alloy with a high silver content. This required a torch, typically acetylene/air. Temperature range is 1200F-1500F.

You get a much better bond with solver soldering, if that's what you need. I did an experiment of laying a 12 gauge copper wire across another and soldering the two together with soft solder and another with silver solder. I then hammered them flat. The soft soldered wires separated. The solver soldered wires did not.


I do know there is a silver bearing soft solder, and have used it. In my case, I found no advantage.


spsalso

Sounds more like brazing I am on about you need a blow touch with MAPP gas in it a propane torch it will just still there.

I am more than happy with the possibility that crimping a connector onto a solar wire is outside the skill set of causal labour trained in 5 mins how to use the tool.

https://www.gov.uk/government/publications/fire-in...

Just found this for solar fires in the UK.

Not many of them in the grand scale of things.

Interesting that isolators are the main culprit.

The Germans prefer to have a DC disconnect on the actual inverter. Hence I don't have them. There is no fusing in the UK to my knowledge on series strings. But I presume an inline locally install fuse box has the same risk as an isolator. I don't have either.

Connectors next on the list must admit I used sunclix because that's the make on kostal inverter. And the panels came with two mc4 connectors for every 10 panels one male and one female which where also sunclix (panels assembly done in Estonia by NAPs)

My inverter is mount on a concrete cellar wall.And there is a linked fire alarm down there. Many installations you see in solar groups they are in people's attics mounted on fibre board and battery sitting under them on wooden flooring.

But me doing that is more luck than judgement.

Wonder if some of these roof fires are linked to the old school firemen's isolators which are just a remote isolator.

This has been an interesting discussion. Two of my three kids have solar on their houses and we're thinking about it. However, when I saw the heading "Solar system fires", my first thought was, "Which planet is it this time?"

============
"Is it the only lesson of history that mankind is unteachable?"
--Winston S. Churchill

Yes, a very confusing title. Probably too late for the OP to put something useful there instead.

Keith Cress
kcress - http://www.flaminsystems.com

Yes "solar system" definitely brings to mind the sun with planets around it.

Add fires and I'm wondering if it's a solar storm or coronal mass ejection event. Some transformers got close to catching on fire during previous events in 1989. We are currently at a peak in the 11 year cycle of solar activity. The results of a solar storm just hit earth yesterday https://www.indiatoday.in/science/story/geomagneti...

On the original subject, my gut feel is workmanship / connections. I have been involved in infrared monitoring of electrical equipment for the past 20 years (at least on and off). The vast majority of electrical events (infrared findings, occasional smoke, and rare fires) reported at our power plant were related to connections. Combine that with the current solar environment where we have had high rate of installation over the past decade with demand for lots of new workers and the result is potential for a lot of installation workmanship events. Just my SWAG fwiw...



=====================================
(2B)+(2B)' ?

I see the issue, although most read my first post and understood. At any rate, I have asked management to change the title to "Rooftop solar system fires". Watch this space.

Quote (hokie66 (Structural))

I don't think Australia is on top of this issue, either. It is reported that about 10% of house fires in Australia are started by rooftop solar. But that could be because domestic installations are done by cowboys.

Most of the installations are done by cowboys unfortunately.
There were also different 'best practice' aspects that have since been reversed due to issues, such as use of polarised breakers and their subsequent withdrawal.

Having had to do utility mandated inspections on a few installations, there's plenty of opportunity for cowboy workmanship to creep in, and that's without the often seen incorrectly selected equipment that isn't suitable for duty, but still used as the installers don't know any better.

The interesting thing with solar panels is when a short occurs there's enough current flowing to get things really hot but not enough to melt conductors, blow clear or trip breaker magnetic elements. This results in the short sitting there for ages until the material around it gets hot enough to burn.

EDMS Australia

I must admit as a mechie my gut feeling is to reduce the number of connections in a systems because its doesn't matter if we are talking electrical, hydraulic, pneumatic they are in the main the failure points. Especially if they involved onsite fitting.

Its one of the reasons why I don't like and would avoid any of these modules that sit under the panels be it optimisers or rapid shut down isolators. You double up on the amount of connectors and they will be dissimilar makes between module and panel.

The cowboy stuff goes beyond electrical.

A workmate had a system fitted 2 months ago and ask me to go look at it. he has panel corners sticking high of the roof ridge line, And the wires under the panels are spaghetti with some of them dangling and touching the roof. Others are not touching but the connectors are the lowest point of the loop. Which is just asking for roof problems and water ingress into the connectors. The corners proud of the ridge line he can do nothing about and apparently is local permitted. but the big boss came to see the wires dangling and was extremely upset. The workers turned up on a Sunday unpaid to fix them.

Solar groups in UK are showing pictures of 100mm racking bracket screws which should be through into the trusses just sticking through the moisture board it was lucky the owner spotted the bumps in the insulation. court case now in progress for a new roof. MSC which is meant to be the trade oversight of standards and quality have washed their hands of it and say its a civil matter. Quite what you get for paying 15% more for a certified MSC installer I can't really work out.

From Tugboat's link to the IEEE article:



Are "lack of drainage" and "DC arc in combiner box" not installation errors?
The other factors could also be exacerbated by poor workmanship during installation.

Combiner boxes are notoriously found to be totally crappy quality in many cases. You can end up with a lot of amps running thru them at the hottest part of the day. I can see a lot of them stressing out and smoking.

Keith Cress
kcress - http://www.flaminsystems.com

It would be good to show which particular country you are describing.

That which is done in one country may not be done in another.

For example: whatever a "combiner box" is, in the US they should not be a problem due to "a lot of amps running thru them".

If y'all want to talk about crap installations in far away places (which you may well inhabit), please note where those far away places ARE.


spalso

We don't have combiner boxes here just straight strings to inverter no fuses and no rapid shutdown.

They are the place where multiple strings come through, that's where the fuses/breakers are located, Surge protection for the strings, string monitoring if it's not done and the rapid shut down isolators if required if it's in the attic and also the earthing bus bar and grounding protection stuff. Some also do the paralleling of strings up as well. If there is DC charging of batteries involved there is a whole load of other stuff in there as well.

They are used a lot in the USA due to a code regulation you have. Before about 10 years ago USA mainly used inverters with transformers and required a separate ground spike to the solar which was bonded across to the main house spike. That then went to the combiner box to be used for the surge protection, array grounding and to the inverter DC side.

The transformer less inverters get the ground from the AC side and as such don't require a dedicated earth spike of their own for the DC side. But the fusing, surge protection, Dc breakers, firemans isolator etc are still being put into combiner boxes. They developed over the years into quite an industry and heavily sold as major safety required items. Each box has colossal amounts of connection points between various components handling some very high currents and voltages. And they like to get them as small as possible which is one of the selling points.

The old transformer inverter setups with battery with all the trunking etc you could easily fill up 2m2 of wall with all the bits and bobs that are now included in the purpose made combiner boxes which come in at under 0.5m2.

German codes require all that external stuff to be included inside the transformer less inverter. Europe has never really used transformer isolating inverters. Plus, it's a different setup because we have 230V/400V 1/3 phases and USA has your split phase setup.

The above is what I know on the subject of combiner boxes and I will admit it may be incomplete or wrong in some parts especially surrounding the earth required onto isolating transformer setups.

Some solar setups are works of art with the wiring and various bits and pieces, You look at mine with 5 cables coming down a flexitube from the ceiling into the inverter and it feels very like you have turned up to a gun fight with a potato gun when everyone else has military assault rifles. The combiners can be 500$ plus. Some say but you need to be able to isolate the strings. Only time I have ever disconnected mine after installation in 4 years, was to boot up my second inverter and register it with the grid for the new barn. And due to that being delayed building it and paperwork deadlines, I did a Boeing and borrowed a string of the first inverter to power it up. Connected the AC to the house and internet registered it and then left it for 3 days until I got the confirmation from the grid that paperwork was now complete and then put it back the way it was and the new inverter under my bed.

spsalso; Not a problem!

Chinese crap combiner boxes installed in the USA.

Keith Cress
kcress - http://www.flaminsystems.com

Am I right about what combiner boxes are itsmoked?

I am talking about an ex soviet state in the EU, with knowledge of how they do it in Germany, UK and a little bit about France mainly due to mates that have systems installed in those countries.

In fact, I should be getting sales bonuses of Kostal and BYD for the number of systems installed I have been involved with. And on a hit list for Enphase and Solar Edge.

"spsalso; Not a problem!

Chinese crap combiner boxes installed in the USA."

Thanks. And what is the name on those "combiner boxes"? And the model number?

While the UL is not high on my list of integrity-first organizations, I do imagine that every "combiner box" would have to have UL approval to be installed in a solar system.

I can imagine that if an installer installed a non-UL approved item, and it started a fire, the insurance company involved would suddenly divorce themselves from the need to pay out to their insured.


spsalso

We get lots of issues with Hoffman brand enclosures on our boats. They have a stainless steel unit that uses square section o-rings integrated into the heads of the screws that hold the cover on. They use buna-n rubber for the o-rings. After about 5 years the o-rings have multiple cracks and the enclosure starts admitting water from spray. I have had to go through my fleet and replace all o-rings with silicone and have also had to replace the gasket with EPTFE tape. Hoffman is a premier brand, we don't have any better choices.

And as someone has said before most of the solar stuff is in plastic enclosures these days.

And there is a huge difference in temperature range specification. The 5$ each MC4 connectors are -40 to +85 C the 1.50$ are 0 to 60 degs C.

Not that most consumers would ever look at a tech sheets.

Quote:

installed in a solar system

Not this again... Do you mean a photovoltaic system?

Keith Cress
kcress - http://www.flaminsystems.com

Maybe a photovoltaic system installed in our solar system.

An insurance company that had to pay because of a fire from a non-rated box, would likely go after the inspected, installer, and maybe even the finance company. Substandard crap is not allowed, according to code.
The homeowner would not know this, and a licenced installer/electrician/inspector would.

Hoffman boxes are a premium brand, and are not the cheapest, but it might be salt water that you are fighting. The steel boxes work well in the mostly dry country.

Sparweb mentioned drainage. How do these combiner boxes drain?

They don't from what I have seen they are basically fancy consumer units with various ratings which as tug says are not lifetime guaranteed. They seem to like bling fancy photo's of complicated fancy electrical gear with vast marketing verbose nonsense about implied safety benefits with very little actual meat of case requirements for having the features. So its lots of DIN modules with heavy duty wires going between various points. They look impressive I will admit. But the engineering case for having a lot of the stuff is nice in theory but just the addition of 30-40 connections running at high voltage and in the US case high currents seems to create more incidents than they protect against.

Keith,
‘Photovoltaic’ is an example of sesquipedalianism. We are not all sparkies here.

It also could have been some German who came up that word

John R. Baker, P.E. (ret)
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

Hahaha!

You use "sesquipedalianism" to complain about photovoltaic??!!

These systems are generally referred to as "photovoltaic" or "PV system" or "solar" carefully, without the word 'system' attached.

Keith Cress
kcress - http://www.flaminsystems.com

There is two domestically.

Solar thermal is the most efficient and uses vacuum tubes to heat water which is then used.

Photovoltaic produces usefull electrons.

There are a couple of other methods, the most scary one is again thermal which involves mirrors onto a ball heating water to utterly stupid temps and pressures which then gets expanded through a turbine. To produce electrons.

They also increase the work of fire people trying to put out the structure fires.

Quote (Alistair_Heaton)

...the most scary one is again thermal which involves mirrors onto a ball heating water to utterly stupid temps and pressures which then gets expanded through a turbine.

You mean like this solar thermal farm where mirrors reflect the sunlight onto a series of 'boilers' mounted on towers, creating steam which then turns a set of turbines down at ground level? The picture below shows the Ivanpah solar farm near Ivanpah, CA, just inside the border from Nevada, on the way to Las Vegas:


April 2019 (Sony a6000)

Here's an earlier shot of one of the towers taken while the facility was under construction:


May 2012 (Sony DSC-H2)

John R. Baker, P.E. (ret)
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

FYI, they are mostly using sodium or molten salts in the tower instead of water.

Yea, I knew that ;-(

John R. Baker, P.E. (ret)
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

Thought they called those 'bird flamers".

Keith Cress
kcress - http://www.flaminsystems.com

Streamers is the official name.

Imagine what offshore wind turbines are doing to birds where they aren't so easily counted when dead?

Animals are harmed by all types of power generation. That is fact. But a serious consideration we need look at is the sudden shift in light temperature from low energy sources such as LEDs. Suddenly we have moved from 1700k to 6000k when transitioning from incandescent to LED. In that same time period there has been a mass die off of insects and I believe artificial late night light is a contributing factor.

Thats the scary ones, I didn't go into the full details of them, they are basically setup like a nuclear reactor with primary and secondary circuits. Don't know much about them just read a bit of low level interest stuff.

They have done plenty of studies about on and offshore windfarms in UK and birds. The populations don't show any drop in numbers and no vast numbers of fatalities around onshore ones.

Huh, that's odd because our studies show vast fatalities around our onshore ones.

Interesting will have to go look again.

They have put a lot of work in on minimising it in both Scotland and Norway.

I think one of the solutions was to paint one blade black.

Here is the sort of stuff we see on the subject in Scotland. And there is quite a large anti windfarm movement.

https://scotlandagainstspin.org/2020/10/the-wind-s...

Birds strikes and avoidance of wildlife has been part of my professional life for years.
Windfarms are actually a bit of a risk for aviation. They mess with radar mosaics and also can do nasty things to the lower wind profiles and turbulence. So we do get briefed on them and follow them.

Seems to depend on your definition of vast. Compared to the genocide that cats do to the bird populations its actually a very small amount. More of an excuse for NIMBYs to try and not have them nearby.

Streamers!

That's right! Thanks for that.

Keith Cress
kcress - http://www.flaminsystems.com

I had a friend who's job it was to find and count dead birds on wind farms.

https://www.google.com/url?sa=t&source=web&...

It wasn't so much an issue of the number of birds killed but the types of birds. The raptors and predatory birds were most likely to fall victim.

That top bit gets to 550 degs C

Just googled why they call them streamers. Poor birds getting roasted

Yeah Alistair, probably not a problem up your way, more of a Southern California focus issue.

Keith Cress
kcress - http://www.flaminsystems.com

Do you paint one blade black in the USA?

Negative.

We make the blades water-clear so birds can't see them.

I kid. But no black blades.

Keith Cress
kcress - http://www.flaminsystems.com

Why would that help?

Apparently it makes a darker disc in the air that birds can more easily recognize.

Keith Cress
kcress - http://www.flaminsystems.com

Re birds and wind turbines: The Danish ornithologist society estimate that a wind turbine on land on average causes the deat of 4 bird pr. year based on research done in the German Bundesländer Brandenburg (comparabel to Denmark). Cant really say if thats few or many. I guess it will depend on the species killed. Appearent eagles are not scared by wind turbines and sea eagles often gets killed by wind turbines. In Denmark its estimated that wind turbine annually kills 10,000-17,000 birds whereas traffic kills 1,100,000 birds.

--- Best regards, Morten Andersen

To add to Morten's data, cats kill 2.4 billion birds a year.

Keith Cress
kcress - http://www.flaminsystems.com

Sounds about the same as the stuff we hear in UK.

Aviation wise we hit relatively alot of birds of prey as well because they are not scared of us.

Have sat a few times in a thermal with a bird of prey with it eyeing us. Prey birds high tail it out of there.

This is different to the flocking birds who maximise their individual chances by keeping close together. Aka what sully had to deal with.

We never hit black crows way way to intelligent.

Alligator lizards in the air? Is that what that means?

Power companies also have to keep track the birds that are killed. But building owners don't. Why?
Shiny buildings injor more birds per year.

There is another type of solar that uses mirrors to focus the sun light onto a pipe. But not so high temperatures.

Quote (cranky108)

There is another type of solar that uses mirrors to focus the sun light onto a pipe. But not so high temperatures.

That sounds more like a system for producing, or at least preheating, water for a domestic/commercial hot water system. There's a couple of homes near here who have both photovoltaic and what appears to be panels which have what looks like plumbing running to and from them. I've heard of people installing systems like that to heat their swimming pool.

John R. Baker, P.E. (ret)
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

I took a "solar" class towards the end of the last century. That class was almost completely about using solar for heating, both buildings and water. I don't recall anything about photovoltaic, probably because it was still strikingly expensive to do for a whole building. I had an acquaintance who also took the class and installed solar hot water. As far as I know, it's still working.

My recollection was that one option was to build your own (hot water) "panels" from scratch. I don't think there was much out there commercially.

The class was quite interesting. There was discussion of placement of thermal mass and windows and roof overhang and........


spsalso

JRB, I beleive cranky108 was referring to the so-called Solar Energy Generating Systems, also located in CA. Generates steam to run turbines. Looks like mostly retired in 2021, replaced with PV.

The problem with sloppy work is that the supply FAR EXCEEDS the demand

Yes, I once considered doing a solar hot water system, but nothing came of it as that was about the time that we moved from Michigan to SoCal. While we owned our home in Michigan we had to rent when we first got here, and I lost interest, but I've still got a couple of books that I bought back then, 'Solar Heating and Cooling: Engineering, Practical Design, and Economics', by Jan F. Kreider and Frank Kreith, published in 1975, and 'Producing Your Own Power: How to Make Nature's Energy Sources Work for You', by Carol Hupping, published in 1974. While the first book was your pure engineering text, the second one was more of a new age tome published by a company known for books on organic gardening and such.

John R. Baker, P.E. (ret)
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

I actually have a solar water heating system on my roof. It was there when I purchased the house. It now doesn't work, and I have no documents on how it is supposed to work.
I suspect it needs anti-freeze, but I don't want to climb on the roof to put it in. Besides what type?

There must be piping down to some system in the house and a control system. You can usually service them without going on roof.

Now days the plumbing and freeze issues tend to drive people to PV water heating instead as a 'dry' power cable is much easier to run and solar panels are cheap. You add an electric water heater in front of the existing water heater and it preheats and stores the solar thermally.

Keith Cress
kcress - http://www.flaminsystems.com

The big thing in uk is the mysolar Eddie and zappi products which divert solar hot water and ev charging.

People are also fitting Willis heaters to use with it for filling the full tank.

Itsmoked, I don't think there are subsidizes for solar heat, only PV.

The freeze issues are easily managed with a bit or propylene glycol.

The corrosion issues are a bigger problem. They are easily managed but most lack fundamental understanding of corrosion prevention including those that sell the treatment products (there are steps required to prepare a system for protection).

Quote:

I don't think there are subsidizes for solar heat, only PV

All the better reason to use PV.

Keith Cress
kcress - http://www.flaminsystems.com

Actually, the water heater system I have, stores the pre-heated water in an electric hot water tank. Just that the electric element is not connected.
I guess I could use it, and set up some PV to heat the water heating elements.

More and more people are going that route as no one wants to deal with the plumbing, antifreeze, and heat exchangers and all that. This is making the electrical aspect of water heating get some focus. You can now get elements that are half and half, half line voltages and half DC solar voltages. DC switching hardware is showing up.

You might find this DIY Solar thread I started interesting reading. I'm surprised it's the largest thread on the entire forum by more than 2x if I'm not mistaken.

direct-to-water-heating

Keith Cress
kcress - http://www.flaminsystems.com

True that typical electric water heater thermostats are not made for DC. But even with a typical 120v inverter, it may not work as expected, as the elements are made for 240V.

There are alot of people using these Willis heaters on their water tanks in europe with solar to avoid giving electricity to the grid free.

https://www.stevensonplumbing.co.uk/willis-externa...
https://heatingpartswarehouse.co.uk/product/willis...

They fit them in parallel to the cold input and the top of the cylinder. And it just cycles the water in the cylinder until the whole thing is at whatever temp you like no pump required.

You can get DC immersion heaters versions and they have a temp safety cut out.

Don't have one personally but everyone seems happy with them, usually linked to an Eddi solar diverter. Some have 2-3 in series, and they kick in and out depending on the solar output.

Some run them direct DC as well just limit the series string voltage so it doesn't bust 230V the current will be self limiting any way to under 12 amps 3 kW immersion max current is 13 amps. And they put them on the buffer cylinder, but you need to have mixer valves on every circuit if you do that.

Plumbed right, a solar water heating system can be setup to drain at night and then not require heating loops or anti-freeze.