Poll

Do you keep records of your solar production

No I dont have solar
21 (58.3%)
No I don't care
3 (8.3%)
I look at the GTI LCD occasionally
4 (11.1%)
I look at the GTI display often
3 (8.3%)
I look at the GTI display even after dark
3 (8.3%)
I have solar, no GTI and I keep records (like Mike)
2 (5.6%)

Total Members Voted: 36

Author Topic: UK solar doldrums  (Read 7620 times)

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Offline fourtytwo42

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Re: UK solar doldrums
« Reply #175 on: March 19, 2018, 12:17:07 am »
hahaha now if I lived on a ship I might just have one of those to hand :) maybe this is where keeping your panels indoors in the warm is a winner :)

EDIT interestingly just used summer washer (sponge on long stick) to wipe snow off lower 3rd of panels and output immediatly lept up to a respectable 100W or so. Lesson is oriantation of shadow is important to whether the shading diodes work or not!!
« Last Edit: March 19, 2018, 01:25:21 am by fourtytwo42 »
 

Offline Hero999

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Re: UK solar doldrums
« Reply #176 on: March 19, 2018, 09:33:34 pm »
I believe solar panels are more efficient, at lower temperatures, because the voltage drop of the diode junction increases.
Other way around a silicon junction voltage reduces at -2mV/degC.
Exactly, as the temperature rises, the voltage drops, so lower temperatures should yield higher a efficiency.

As long as the solar panels aren't covered in snow, the colder it is, the more power you'll get, for the same amount of sun.

What's it like today? Where, I live most of the snow has now melted, although it's still near freezing.
 

Offline woody

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Re: UK solar doldrums
« Reply #177 on: March 19, 2018, 11:07:01 pm »
Over here (Netherlands) today it's completely cloudless with an outside temperature of 3 deg. C. The maximum power I saw today from our 30 panels (one of which is broken) is around 6300W, average inverter temperature is 35 deg C, average panel temperature is 25 deg. C. A total of 7200Wp is installed with (not so efficient) microinverters.

In my experience clear days in spring (March/April/May) always have higher yields than clear days in summer. Monthly yields are higher in summer due to more fair weather and longer days, but record days are always in the spring.

I think this is not only due to lower panel temperatures but also because the air contains much less water on fair cold days. What also helps is the fact that my panels are at angles that work better in spring (45+55 degrees).

« Last Edit: March 20, 2018, 03:45:35 am by woody »
 
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Offline woody

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Re: UK solar doldrums
« Reply #178 on: March 20, 2018, 03:45:15 am »
And indeed, today's total generation is at an all -time-high of 38.1 kWh. Now I wish I had replaced the one broken microinverter earlier....
 

Offline fourtytwo42

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Re: UK solar doldrums
« Reply #179 on: March 20, 2018, 05:17:13 am »
Wowww thats amazing around 7.2Kwh per Kw installed!!
I made 2.8Kwh per Kw installed today a record for this year so far :)
Mine is lower partly because I dont export so everything is used in the house.
Peak power today was 0.9Kw per Kw, this depends on the load offered at the best time of day, it sometimes hits 1.05Kw.
I agree on spring sunshine, again my panels are about 52degrees that also happens to be my Lattitude :)
Clearer air, no high haze this time of year and no airborn dust from the feilds, as for pollution the surrounding pig farms dont seem to affect solar as much as my nose hahaha
About the same conditions here Hero :) and yes the Axitec panels Pmpp increases 0.45% every degree C lower.
« Last Edit: March 20, 2018, 05:26:09 am by fourtytwo42 »
 

Offline woody

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Re: UK solar doldrums
« Reply #180 on: March 20, 2018, 07:14:39 pm »
I'm not sure how you arrive at 7.2kWh/kW installed. PVOutput tells me 5.3kWh/kW which seems more accurate. Still amazing to me; our yearly average hovers around 2kWh/kW  ;D
 

Offline fourtytwo42

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Re: UK solar doldrums
« Reply #181 on: March 20, 2018, 08:47:50 pm »
I'm not sure how you arrive at 7.2kWh/kW installed. PVOutput tells me 5.3kWh/kW which seems more accurate. Still amazing to me; our yearly average hovers around 2kWh/kW  ;D
Neither am I and I cannot now figure out how I arrived at such a number, many thanks for the correction :)
My annual average is just about 1.1Kwh/Kw but that includes downtime for tinkering, holidays when it's switched off and as explained earlier the fact that I don't export. Your figures show me what is possible, may I ask your lattitude and oriantation ? Mine is 52,35N and SSW(235deg) almost on the meridian, roof angle 51deg.
« Last Edit: March 21, 2018, 03:22:35 am by fourtytwo42 »
 

Offline woody

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Re: UK solar doldrums
« Reply #182 on: March 21, 2018, 02:13:59 am »
Our position is 52.44N 4.40E, give or take a couple of miles. Orientation is 190 deg. 16 panels under 55 deg and 14 panels under 45 deg. We have lots of part-time shading, hence the micro inverters. The system is net connected and always on. Except the one inverter that broke down last March and still is not fixed by me :-[
 

Offline fourtytwo42

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Re: UK solar doldrums
« Reply #183 on: March 21, 2018, 03:28:01 am »
Were almost identical, very interesting to exchange information, fortunatly I dont have any serious shading. I have wondered about a steerable array to pick up the rising sun but from what I could estimate the power gain would not justify it. Interesting issue with micro inverters having to scamper up the roof to replace them but as you say good for heavy shading.
 

Offline woody

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Re: UK solar doldrums
« Reply #184 on: March 21, 2018, 04:16:48 am »
Are you east or west in the UK?

Microinverters are a bit of a tradeoff imo. Using them means (apart from a number of other advantages) that if one stops, the rest of the system keeps working. When your central inverter fails, nothing works. The downside is indeed that for every failing inverter you have to go on the roof, remove the panel, replace the inverter underneath and reinstall the panel. Which is a b*tch. So it gets postponed as long as possible.

I use Enecsys inverters.These inverters were sold with an operating life expectancy of greater than 25 years and came with a 25 year warranty. They were designed to be more or less unbreakable due to not using electrolytic caps inside.  I got them in early 2013 and then Enecsys became insolvent in early 2015. So much for the warranty. Out of the 30 inverters on my roof I have 2 broken so far. I'm kinda hoping that these 2 are the early failures on the left side of the bathtub curve  :)
 

Offline fourtytwo42

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Re: UK solar doldrums
« Reply #185 on: March 21, 2018, 08:23:53 pm »
East 0,48E in East Anglia so quite close to the Netherlands :)

As for microverters IMOP the cost is very hard to justify dramatically increasing the payback time of the system but for many that is not a concern. Also for me I wanted to build my own converters for water heating so microverters were not an option. I have see many blown single inverters on Ebay and many lurid stories about failures so I guess the commercial units are built for a price. I had a few mosfet failures in the early day's caused by turning on the immersion heater switch with inadiquate gate voltage but since then no more problems.

Shame about Enecsys they had a good idea but I guess the real world performance was not up to the marketing hype hence the companies failure.

Beutiful sunny day here today so out potato planting :)
 

Offline woody

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Re: UK solar doldrums
« Reply #186 on: March 21, 2018, 09:36:10 pm »
We indeed are at comparable latitudes. Nice for comparison.

I'm still not decided about those micro inverters. They do solve the 'bad panel in a string', mppt-per-panel and shading problem. The latter is important on my roof. Single point of failure vs multi point of failure is also better with micro inverters. But IF something goes wrong there is way more work than with a single inverter. I start to see that as a disadvantage. Then there is the better monitoring, you can pinpoint malfunctioning solar panels. But solar panels themselves hardly ever fail so that advantage is minimal. A last advantage is that you don't have high DC voltages on the roof. Only 230VAC. Disadvantages are slightly higher costs and slightly lower efficiency.

If I had to do this again I probably would use 4 smaller, 2 kW central inverters, strategically distributed over the panels.

« Last Edit: March 21, 2018, 09:51:24 pm by woody »
 

Offline coppice

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Re: UK solar doldrums
« Reply #187 on: March 21, 2018, 10:32:01 pm »
Are you east or west in the UK?

Microinverters are a bit of a tradeoff imo. Using them means (apart from a number of other advantages) that if one stops, the rest of the system keeps working. When your central inverter fails, nothing works. The downside is indeed that for every failing inverter you have to go on the roof, remove the panel, replace the inverter underneath and reinstall the panel. Which is a b*tch. So it gets postponed as long as possible.

I use Enecsys inverters.These inverters were sold with an operating life expectancy of greater than 25 years and came with a 25 year warranty. They were designed to be more or less unbreakable due to not using electrolytic caps inside.  I got them in early 2013 and then Enecsys became insolvent in early 2015. So much for the warranty. Out of the 30 inverters on my roof I have 2 broken so far. I'm kinda hoping that these 2 are the early failures on the left side of the bathtub curve  :)
If a small company offers you a 25 year warranty, you can be sure they aren't expecting to be around for long, and probably don't care too much about the product's durability. Even if its a big company, they may have partitioned the activity into a subsidiary which they can let go to the wall, without pulling down the main enterprise.

Micro-inverters seem to be very popular in the US. They nicely avoid things like shade issues, but the cost is a problem.
 

Offline ahbushnell

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Re: UK solar doldrums
« Reply #188 on: March 22, 2018, 01:18:33 am »
We indeed are at comparable latitudes. Nice for comparison.

I'm still not decided about those micro inverters. They do solve the 'bad panel in a string', mppt-per-panel and shading problem. The latter is important on my roof. Single point of failure vs multi point of failure is also better with micro inverters. But IF something goes wrong there is way more work than with a single inverter. I start to see that as a disadvantage. Then there is the better monitoring, you can pinpoint malfunctioning solar panels. But solar panels themselves hardly ever fail so that advantage is minimal. A last advantage is that you don't have high DC voltages on the roof. Only 230VAC. Disadvantages are slightly higher costs and slightly lower efficiency.

If I had to do this again I probably would use 4 smaller, 2 kW central inverters, strategically distributed over the panels.
Isn't the reduced efficiency offset by fixing the shading problem?
 

Offline fourtytwo42

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Re: UK solar doldrums
« Reply #189 on: March 22, 2018, 03:11:19 am »
If I had to do this again I probably would use 4 smaller, 2 kW central inverters, strategically distributed over the panels.
I have seen central inverters with 2 seperate mppt channels supporting 2 strings and hence reducing the voltage and helping with shading. I would not be suprised if a little hunting might turn up one with even more though that doesnt help your single point of failure issue. Another thing that concerns me with many recent inverters is they are so called "transformerless" for a gain of a few percent efficiency (read reduced manufacturing cost) and IMOP dramatically reduced safety by connecting your rooftop panels directly to the grid!
 

Offline capt bullshot

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Re: UK solar doldrums
« Reply #190 on: March 22, 2018, 05:28:15 pm »
If I had to do this again I probably would use 4 smaller, 2 kW central inverters, strategically distributed over the panels.
I have seen central inverters with 2 seperate mppt channels supporting 2 strings and hence reducing the voltage and helping with shading. I would not be suprised if a little hunting might turn up one with even more though that doesnt help your single point of failure issue. Another thing that concerns me with many recent inverters is they are so called "transformerless" for a gain of a few percent efficiency (read reduced manufacturing cost) and IMOP dramatically reduced safety by connecting your rooftop panels directly to the grid!
The rather high DC voltage with these (typically 300V under full load, but allowed to 450V for smaller ones, and 900V for large installations) is way more dangerous than the direct mains connection. In case of a broken wire within the panels or the wiring, you'll get a nice arc setting your roof on fire (yes, the panel's plastic rear side can burn like hell). And there's another issue with the non-symmetric DC volatage in relation to earth with some panel, causing early degradation by some weird kind of internal material migration.
Anyway, mine (a dual string transformerless one) does just fine, and I haven't seen any dead pigeon dropping from my roof yet ;)
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Offline fourtytwo42

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Re: UK solar doldrums
« Reply #191 on: March 23, 2018, 01:07:42 am »
If I had to do this again I probably would use 4 smaller, 2 kW central inverters, strategically distributed over the panels.
I have seen central inverters with 2 seperate mppt channels supporting 2 strings and hence reducing the voltage and helping with shading. I would not be suprised if a little hunting might turn up one with even more though that doesnt help your single point of failure issue. Another thing that concerns me with many recent inverters is they are so called "transformerless" for a gain of a few percent efficiency (read reduced manufacturing cost) and IMOP dramatically reduced safety by connecting your rooftop panels directly to the grid!
The rather high DC voltage with these (typically 300V under full load, but allowed to 450V for smaller ones, and 900V for large installations) is way more dangerous than the direct mains connection. In case of a broken wire within the panels or the wiring, you'll get a nice arc setting your roof on fire (yes, the panel's plastic rear side can burn like hell). And there's another issue with the non-symmetric DC volatage in relation to earth with some panel, causing early degradation by some weird kind of internal material migration.
Anyway, mine (a dual string transformerless one) does just fine, and I haven't seen any dead pigeon dropping from my roof yet ;)
Not that I wish to provoke an argument on our thread devoted to output but the operating conditions of the panel string is identical irrespective of whether there is a transformer in the inverter or not, the only differance being whether or not they are galvanically isolated from the grid, so all of your worries concerning arcs etc apply equally to a transformerless inverter regardless of what you may have been told by your installer.
 

Offline Monkeh

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Re: UK solar doldrums
« Reply #192 on: March 23, 2018, 01:13:29 am »
If I had to do this again I probably would use 4 smaller, 2 kW central inverters, strategically distributed over the panels.
I have seen central inverters with 2 seperate mppt channels supporting 2 strings and hence reducing the voltage and helping with shading. I would not be suprised if a little hunting might turn up one with even more though that doesnt help your single point of failure issue. Another thing that concerns me with many recent inverters is they are so called "transformerless" for a gain of a few percent efficiency (read reduced manufacturing cost) and IMOP dramatically reduced safety by connecting your rooftop panels directly to the grid!

Forget to turn off the DC isolator and you can get a pretty nasty surprise - it's not directly connected but I've had a ~600V leakage belt out of mine, that woke me up in a hurry. The big isolators and labels aren't for show!
 
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Offline woody

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Re: UK solar doldrums
« Reply #193 on: March 23, 2018, 02:51:50 am »
Isn't the reduced efficiency offset by fixing the shading problem?

On my roof I'm pretty sure that that's the case. The reduced efficiency is only a couple of percent anyway and I am not really complaining. Only noting that on bright days in summer when shading is less of an issue some electricity is wasted by micro inverters when compared to central inverters.

To be honest, I think it is really difficult to prove one system is better than the next. Way too many variables are at play.
 

Offline fourtytwo42

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Re: UK solar doldrums
« Reply #194 on: March 23, 2018, 05:24:03 am »
Isn't the reduced efficiency offset by fixing the shading problem?

On my roof I'm pretty sure that that's the case. The reduced efficiency is only a couple of percent anyway and I am not really complaining. Only noting that on bright days in summer when shading is less of an issue some electricity is wasted by micro inverters when compared to central inverters.

To be honest, I think it is really difficult to prove one system is better than the next. Way too many variables are at play.
Exactly :) a few percent here or there can easely be lost in measurement accuracy, I think the choice is personal maybe even depending on availability of something for a good deal at the time. Most people will stand by what they have selected and thats only natural :) Sadly the clouds from the Atlantic arrived this afternoon, westerlies bad for solar, easterlies bad for potatoes what a choice :)
 

Offline woody

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Re: UK solar doldrums
« Reply #195 on: March 23, 2018, 06:40:27 pm »
And not only measurement accuracy. Bird shit. Leaves. Lichen. Temperature. Snow. Clouding. Humidity. Con trails. Fired ground fault interrupters that only get noticed after a week. There are a myriad of reasons why a solar array does not deliver its designed output. The choice of inverter technology is only one of them and in my experience, a small one at that.

Hope the potatoes work out or else it's going to be a lot of Fish and Chips in the fall  :D
 
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Offline Bassman59

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Re: UK solar doldrums
« Reply #196 on: March 24, 2018, 11:18:00 am »
I live in sunny Tucson, Arizona. There are 18 panels on my roof, with a maximum generation capability of 6.1 kW. The energy production is about 40 kWh a day, and right now most of that is going back to the grid. We don't turn the air conditioning on until the monsoon season (July) when the humidity makes swamp cooling ineffective. Even with the A/C on in the summer, I expect to have electric utility bills that are just the connection fees and the taxes, around $22/month.

We expect mid-summer daytime temperatures to be above 100ºF starting in May, and it'll remain like that until the end of September.  If this year is like last year, we'll have a month of 110ºF + days in the middle. Wheeeee!
 
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Offline paulca

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Re: UK solar doldrums
« Reply #197 on: March 26, 2018, 06:04:46 am »
Well my nano setup hit boost voltage on the battery for the first time.  Panel voltage shot up, amps fell, battery pinned at 14.40V, so rapidly found things to charge off it.  I now have a pile of charged LiPos.  No point wasting sunlight.  I expect I'll be needing it next few days look rubbish and it can be cloudy for weeks at a time here, so having an energy stock pile helps.
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Offline fourtytwo42

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Re: UK solar doldrums
« Reply #198 on: March 26, 2018, 08:40:09 pm »
I live in sunny Tucson, Arizona. There are 18 panels on my roof, with a maximum generation capability of 6.1 kW. The energy production is about 40 kWh a day, and right now most of that is going back to the grid. We don't turn the air conditioning on until the monsoon season (July) when the humidity makes swamp cooling ineffective. Even with the A/C on in the summer, I expect to have electric utility bills that are just the connection fees and the taxes, around $22/month.

We expect mid-summer daytime temperatures to be above 100ºF starting in May, and it'll remain like that until the end of September.  If this year is like last year, we'll have a month of 110ºF + days in the middle. Wheeeee!
A solar power paradise, payback very fast I should imagine where here in northern europe it's a real struggle to make it economic. Many years ago the subsidies were very much higher but I dont see many new installations going in now, ok for those already on high subsidies as I seem to remember they were fixed for 25 years..........
 

Offline fourtytwo42

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Re: UK solar doldrums
« Reply #199 on: March 26, 2018, 08:42:34 pm »
Well my nano setup hit boost voltage on the battery for the first time.  Panel voltage shot up, amps fell, battery pinned at 14.40V, so rapidly found things to charge off it.  I now have a pile of charged LiPos.  No point wasting sunlight.  I expect I'll be needing it next few days look rubbish and it can be cloudy for weeks at a time here, so having an energy stock pile helps.
Sounds like your ready for anything the atlantic has coming to you, forecast for later this week not to good over here in the east either. So hopefully this will encourage you now we are past the spring equinox the worst part of the year is done with and it's make hay while the sun shines :)
 


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