Is north facing solar a complete waste

unkel

We live in strange times that us as amateur buyers often know more than the professional sellers that we deal with. Because we have a specific question / situation and research it ourselves which gives us in-depth knowledge on that specific point. While the professionals know a little bit about everything in their field, but not as much as us on this specific point. Same with GPs (doctors), same with EV car sales persons, solar installers, etc.

bullit_dodger

https://www.boards.ie/discussion/comment/120070659#Comment_120070659

i remember when you first came in (12+ months ago) asking the question about the north facing roof. Great to see that you gave it a lash and were able to work through the problems. It's a case of having to work with what you got, but awesome to see that your installation is so far being a positive thing for you.

Respect.

Manion

https://www.boards.ie/discussion/comment/120073192#Comment_120073192

https://www.boards.ie/discussion/comment/120073569#Comment_120073569

The trend of "SEAI says no" is something that's popped up a few times on the quotes thread. The kind interpretation is just a lack of awareness but It seems to be the go to when an installer doesn't want to hassle of the whatever you're asking them to do but also doesn't want to reputational hit. People have been told this about batteries as well. I'm in the process of applying for the grant, it should be another month or so before I hear back but there was nothing about North facing not being allowed.

It took me quite a bit of time and effort to get an installer willing to do the job, part of it is convincing them you've done your home work, all the tools are available on this forum and it all comes down to the price point. I think earlier on I made reference to folks paying as much as me for a E/W 4-5kWh installation, therefor how could it not make sense to do 8kWh north facing when I'm predicting 5,000 kWs generation a year.

Some neighbors where actually asking about it this morning and the main thing I said to them was it's about your personal circumstances. For instance, is a 7-8 year RoI something you're happy with. We're in a very fortunate position not to have to borrow to pay for all this but if someone was paying about 5% on financing to cover the cost, I'm not sure I would recommend it to them. Also how do you feel the future is going to shake up in terms of electricity costs because ultimately you're taking a bet. Ultimately solar is a capital investment now to ensure your electricity bills for ever more are cheaper than they would have otherwise been and there is something very attractive about that.

Just to recap:

• The main negatives for north facing is that the power generation is not only less it's highly concentrated in the summer months.
• You need a large installation to bring down the marginal cost per peak unit capacity, if you cannot get up into the 7-8kWp range, you're going to run into problems.
• Load shedding is a bigger aspect of the model so you'll need a decent night rate and obviously batteries to get the most out of the system.

Regarding only being able to get 1.6kws, perhaps smaller panels would allow you to get better coverage south facing, though shadow is the real issue. Some basic calculation here of of 4.8kWp north (that's probably pushing the limit for a single string) and 1.6 kWp south assuming Dublin will give you roughly 4K Units a year.

Manion

Todays outputs for a taste.

ixtlan

I came across this wondering the same thing as the OP.

My situation is a bit different in that I have a semi-detached house with a hipped roof, which hugely restricts how many panels can be installed. Lots of people are going to be in this situation I expect.

I did have one installer look at the almost directly South-facing front roof and say they could not get more than 4 panels on it and so it wasn't worth it. And I guess that's right from a certain point of view, but looking at the solar calculators people kindly added and inspired by Mannion I was working out the numbers.

I should add that my gable roof has a chimney and is close to the house next door so probably could not take any panels. The front faces 30 degrees East of South, so the back 30 degrees West of North. Any North panels would generate about 55% of the annual KWh output of the South roof ones. The interesting thing is that a North-South installation of 4/4 panels would generate a little more electricity than an East-West split if I had such a setup. In fact the 8 panels together would generate almost 80% of what they would if they were all on the South roof. Seems surprising but that's what the numbers say.

I assume installing on the North roof also will increase install costs, and I know that even the 8 panels is arguable in terms of whether it's enough panels to be cost effective (unclear if I can get more on), but I was intrigued by that 80% number and wondered what people think.

Ix.

con747

https://www.boards.ie/discussion/comment/120113298#Comment_120113298

As far as the amount of panels goes I was told I could only fit 7 on, I have 16 on now 3 orientations, east-west-south. I see no reason why fitting panels on the north side would be any more expensive than any other orientation. Find a good installer, a list here https://www.boards.ie/discussion/2058243236/solar-pv-boards-members-installer-information#latest and let them see how many you can actually fit.

DC999

https://www.boards.ie/discussion/comment/120113421#Comment_120113421

I'm the exact same. Have 16 and whole roof is filled including flat roof. I was told 6-7 from 1st installer

Manion

Mini update. Using shelly EM to monitor what's going into the the Inverter and what's coming from it I'm averaging about 82% efficiency over the last couple weeks. Nothing really to do with North facing, more due to the fact I'm doing two conversions for the load shedding AC -> DC -> AC. It's something to factor in for anyone considering augmenting there setup with offloading consumption from day rate to night rate. The shelly isn't officially rated in terms of accuracy. On the Solar side I'm getting about 89% efficiency and I'd expect overall efficiency to improve the more power is being generated.

Galego

https://www.boards.ie/discussion/comment/120117249#Comment_120117249

Do you mean 18% losses in between the inverter and battery?

20% is always mentioned although it really depends how (what current) you charge and discharge the batteries.

Manion

Total system loss as measured by comparing AC Energy into the Inverter from the main consumer unit plus DC Energy from the Solar panels versus Energy returned from the Inverter to the consumer unit. I'll have to have a think about how I might get just the Battery values. I've grown weary of the Solis reporting.

graememk

https://www.boards.ie/discussion/comment/120117649#Comment_120117649

Welcome to the club 😂

Some of it's fine, the battery stats, not so much

Galego

Just for my understanding, I am yet learning....., I always see a % kwh exported to grid when the inverter is pulling from the battery to meet the house demand. It is working around 5% (average).

Is that the part of the famous "20%" losses between DC to AC from Battery to Inverter to House Demand?

Manion

No that's you're consumption rate and is in addition. The inverter aims to export zero and it does this by readings from the CT clamp, if the CT Clamp is over reporting power demand it will over supply power causing an export. I'm seeing about 2-3% myself and have been thinking of ways I might mitigate against that. It's a shame these things don't come with any mechanism to tune them as I consistently export about 300 watts daily.

Galego

Thanks for clarifying that one for me.

It seems to me it only does it when pulling from the battery and not from the solar.....that's what it is odd to me.

Manion

Grant approved yesterday so no issue with north facing and grant. I actually went back through the documents a d cannot see where it states the aspect for the installation.

https://www.boards.ie/discussion/comment/120123917#Comment_120123917

Nice one.

I'd never heard of the aspect even coming into the equation tbh.

Fingleberries

https://www.boards.ie/discussion/comment/120123917#Comment_120123917

Nice one, well done. I thought as much (as even the SEAI calculator has a N/S split as a possible option, but glad to hear that it is all in order.

ixtlan

I had another installer look at my north/south roof (online call), and again immediately say they would not install on the North-north-east roof and the South was too small.

"Others will install on a North roof, we won't". Implying that anyone who would do it would be disreputable. I pointed out the calculations showing I could generate slightly more than an East-West split, and asked would they install on such a roof, and they said yes... and then agreed that that was an interesting way of looking at it... but No...

One could argue it's better for the country for me to not get this done since the installers have all the work they need and it's better if those who can generate more get preference. That's a reasonable argument, but not the one they are making...

Anyhow I don't know. I probably won't proceed. Maybe I'll wait a few years for the panel efficiencies to go up...

ix.

unkel

Buy parts yourself. Get a roofer to install your panels, get an electrician to hook up your inverter. Job done. No subsidy, but probably cheaper "doing" it yourself. No point waiting for panel efficiency to go up, they don't go up by much more than one percentage point every 2 years or so.

Manion

It’s disheartening but you will get that from some installers. I had a very similar experience with one of the installers. They just get tunnel vision.

DC999

Did a quick check and my NW panels are only averaging 0.3kWh a day per 1kWp at the moment (so 9kWh in the last month). Sun never gets near them now.

Output is decent to end Sept. And they will be grand in spring once sun moves around again (only live 6 months so don't yet know when NW will ramp up). They are handy for evening sun around dinner time - for part of the year.  

con747

https://www.boards.ie/discussion/comment/120135209#Comment_120135209

Did you check on the Sun's path app? https://play.google.com/store/apps/details?id=jp.gr.java_conf.siranet.sunshine&hl=en&gl=US It should give you a good idea when they will kick in.

DC999

https://www.boards.ie/discussion/comment/120135246#Comment_120135246

Cool, never knew about that. Will try it.

Manion

Nice app. I'm going to be sorted come summer time ;). It's interesting the above I'm seeing the same 0.3kWh a day per 1kWp and I'm delighted with it. Got up to 3.2KWs there the other day.

Manion

Just an FYI on February. The model I used to calculate payback period had we generating 124 for Feb, but came out at 165, about 33% more, so delighted about that. Hitting about 88.94% self consumption, this would have been higher except I was a bit slow reacting to the improved output and had been filling up the batteries to 100% at night. I found a 90% threshold meant I wasn't exporting more than .5 units a day (CT clamp accuracy error). In terms of load shifting, my monthly Grid cost came to 99 Euro, 72.86 Euro for night rate and 26.5 Euro for day rate. I'd 84 Peak units and 485 off peak units, so I've gone 83% off peak. Feb 1st was the first day off the year I didn't use any peak units due to the solar output.

DC999

https://www.boards.ie/discussion/comment/120316201#Comment_120316201

Class. Appreciate the info. I am curious how it goes for you.

jkforde

just an observation when driving past a house with a perfect low pitched roof (no PV!) on a hazy day... to me it looked like the south and north facing roofs were both getting a fair share of the diffuse solar watts... so just a consideration for those thinking of North facing panels, lower the pitch the better perhaps (I guess a solar output calculator like PVGIS would tell you that anyhow but they're designed for direct irradiance aren't they?)

unkel

Yes, you're spot on. A friend sent me a pic of the north face of his roof getting direct sunlight. Couldn't believe it as mine is nowhere near, not even at noon. His pitch is extremely low though (semi D 70s built, mine is a semi D 2000 built)