Deleted

Martyn1981

Deleted_User said:

70sbudgie said:

To get more 'bang for your buck' have you considered how the orientation of the PV panels affects the seasonal performance? For example, my E-W panels give me longer duration of usuable generation for the summer 6 months, with a lower peak which would be wasted (or in my case exported). Now well into my second year of PV ownership, I have started looking in more detail at other aspects - for example, how much shorter my generating days are now, because the sun doesn't really get far enough from south (either E or W). So if I were going to add extra panels to improve my winter generation, I would look at a south facing panels and mount them closer to vertical. I wouldn't necessarily expect this to add much to my summer generation, but it would improve the winter generation. And consequently, I believe it would be the opposite of a diminishing return on my investment.

Edit to add: this is the principle behind the architectural feature of big eaves - they provide shade from the high sun in the summer, but let in more low winter sun.

We've done our best with this, but it's a bit of a trade of with appearances and performance. 

We have two 700w arrays each feeding into a different generator. They get sun all day long, but face SSW. I can't remember the angle off-hand, but I think 10 degrees or so (so not far off flat). This is mainly for appearances. At the time our thinking was that it would allow the very early morning sun to hit the panels a bit sooner. We also figured that when the sun hardly shows it's face in winter there wasn't a lot of point going overboard to optimize for it. But we haven't done the actual calculations to prove that theory. 

We also have additional panels feeding in via the mains adaptor - half are SSE, half are SSW - angle about 45 degrees or so - they're mounted on the walls of the house and I don't remember the exact angle. 

So we've bits and bobs in various places that each do better at certain times of year/day. Changing angles isn't completely out of the question, but it'd need to make a big difference to make it worth doing. But good idea to add this to my spreadsheet and 'what if' scenarios. 

This comment (and others) confuses me, as they seem contradictory. For instance a shallow pitched panel wouldn't benefit early generation (nor late), but would in fact do the opposite. You'd want steeper pitched panels to gain more generation earlier, later and in the winter months when the sun is lower.

The same applies to the several comments about winter generation. You suggest no point in trying to optimize for it - For those off-grid, or aiming to minimise annual leccy import, then you should specifically target winter demand, by optimising steep panel pitch, and KWp. The understanding is that this will reduce summer generation (v's shallow pitch) but still lead to overcapacity/oversupply.

For comparison I've stuck a random pin in Oxford on PVGIS, for 1kWp of south facing PV it gave:
35d - 1,017kWh pa, 36kWh Dec
50d - 1,008kWh pa, 42kWh Dec
60d - 974kWh pa, 44kWh Dec

[60d v's 35d would mean a 4% annual reduction, but a 22% increase in the winter when every Wh is needed.]

Hence my confusion, as your comments state benefits, where it seems you'd do worse, and my PV experiences (on grid), plus all conversations I've had with off-grid PV'ers suggest more PV and steeper, will always supply a better balance.

The cost of PV panels themselves, is now so low, that adding more is the first and simple step, where possible, and can even allow for a smaller amount of battery storage by increasing the average daily supply, rather than trying to store all excess.


Btw - another reason I suspect folk are struggling with your statements is that your power and energy figures often don't relate, and you seem somewhat confused by them. For instance several of your posts, such as the 13th Nov (as an example) make no sense. You mention a 10W bulb, but then give an energy consumption figure for it that would take ~3yrs, and is roughly equal to a whole month's average leccy consumption for UK households.

Martyn1981

Hi, again you contradict yourself, the early morning sun is not high in the sky, it is low in the sky, hence why a steep pitched panel works better than a shallow one. this also applies to the winter months, when the sun remains low all day.

You mention altering the pitch of panels through the year, but as I showed with actual figures, there is little to no point, as the annual 'losses' from a steep pitched panel are tiny at about 4%, and all of that 'loss' is during the summer when you already have enough. So no need to alter pitch, simply choose the best pitch for the winter.

Your figures for 1kWp of PV are entirely false. They will never generate 4,800kW (not even 4,800W) of power, and will not generate 4,800kWh of energy in a year, even in the most ideal location (in the world) with dual axis tracking, you would struggle to get half that. Your winter claim of 360Wh is also entirely false, just Dec (not winter) as I stated is 100x that figure.

Next you state that 20% extra is piddling (though you state a 100% increase in your energy figure) in the winter. That suggests to me that you aren't actually serious about your claims, and may just be playing with us. All additional generation in the winter has high value.

Also you state that the extra would be consumed by inverter running costs, that is also false, since the losses are covered by the low generation, and wouldn't rise significantly by higher generation.

Your statements absolutley fly in the face of everything I've ever been told and taught by off-gridders, who target winter demand (not summer), and then simply have oversupply. Obviously this is simple commonsense.

Back to the lightbulb, you gave a power figure of 10W, and and energy consumption figure of 240kWh. Your post made many such statements, much like this new one, where your power and energy figures simply don't match, or aren't based over a reasonable time period (such as ~3yrs for the lightbulb). You may not like using energy when talking about energy, but your use of power instead makes many of your calculations unusable.


Again - Given your stated positions on reducing grid demand, and potential off-grid aims, I'm more and more leaning towards you playing us, as your arguments are the exact opposite of conventional wisdom. That said, if you are playing us, then I take my hat off to you, well played sir, well played.

ABrass

Assuming you're in the Midlands a SSE orientation and 10 degree slope and no shading you'll generate 1750kWh total over the year according to PVGIS using standard assumptions.

https://re.jrc.ec.europa.eu/pvg_tools/en/

How much do you think you're going to generate a year?

Magnitio

I am amazed at the patience of people who have tried to point out the numerous errors in @Deleted_User posts. It does appear that no progress is being made and that we are wasting their time as well as ours.

QrizB

From fiddling with PVGIS it seems the best panel inclination for total all-year generation is something like 5-10 degrees less than your latitude. In the south of England that's 40-45 degrees, in the north of Scotland 50-55 degrees.

For best winter generation it's around 10-15 degrees more than your latitude; 60-65 degrees in the south of England, 70-75 degrees in the north of Scotland.

ABrass

For off grid you're optimising for the wrong thing, there you want to minimise the difference between winter and summer.

For self consumption and selling to the grid optimising for all year round is normally best as you get the greatest volume of kWh.

Optimising for the summer is just odd. But if you don't know how to measure the power you generate I guess it's academic.

gefnew

Would you like to post pictures of your set up so people may get a better understanding of what you have and how you use it.
Regards

ABrass

Yes you can. Each kW of panels should provide around 40kWh during January if you get a good angle on it.

If you install 8kW of panels then that's 320kWh or 10kWh a day on average. You'd need a lot of batteries to deal with peaks and troughs and to be thrifty with your power use but that's achievable, albeit expensive. And even with batteries there's a good chance you'll have low sun days weeks when it becomes really awkward. A lot of off grid people have a petrol generator as backup for that.

But you aren't really describing off-grid, you're describing a DIY, no MCS solar system that relies on the grid for backup.

zeupater

Hi scarter

Reviewing posts for clarity ....

1. You are not off grid for electricity and have solar+battery as a mains failure backup solution which is also used to reduce mains usage ?
2. Your plan is to maximise solar consumption in the summer ?  
3. You have ~2kWp of panels mostly facing SSW, mounted on wood-stores in the garden ?
4. The panels you have are 175Wp because 200Wp panels would be too big to mount on the log store roof ?
5. You have 12 of these panels (2000/175=11.4) giving a true nominal capacity of 2.1kWp ?
   
6. You have a total of 7kWh of battery storage capacity ?
7. You have 2xBluetti AC200Max portable storage units, each having Energy storage capacity of 2kWh & delivering 2.2kW of Power ?
8. You have additional Bluetti expansion battery capacity of ~2kWh ?
9. This would be a single B230 expansion unit connected to one of the AC200Max units ?
10. The Bluetti AC200Max has a maximum solar connected charge rate of 900W ?
11. You additionally have storage comprising 1xBluetti EB70 equiv (1000W/716Wh) and 2xBluetti AC50S equiv (300W/500Wh) totalling 1716Wh capacity ?  
    
12. The Batteries are charged directly via DC connection to the panels?
13. Your main ~2kWp of panels are not connected as one array but operate as 2x 1kW DC arrays each connected to one of the Bluetti devices ?
14. You expect to return batteries to a fully charged state using the attached solar panels each day?
    
15. You still have mains gas connectivity for cooking & heating, although you are attempting to minimise it's use through use of solar ?
16. Your total outlay for 2kWp of DIY solar + larger portable batteries was ~£7k ?
17. You installed (/expanded) the system to it's current capacity in September this year?
18. You are currently (as of Nov 2022) saving ~1.5kWh/day, so around ~45p/day ?
    
19. You expect to heat water, use a dehumidifier/refrigeration etc in summer with the current setup with an ultimate goal of eventually going off grid ?
20. Going off grid means both gas & electricity, so all appliances,, cooking & heating will be via a combination of solar & biomass ?
    

Any chance of addressing the above as it may help ... Z

# Edit - Additional info: Kit change edit 8/9 + insert new 11 + minor grammar

Martyn1981

Deleted_User said:

ABrass said:

For off grid you're optimising for the wrong thing, there you want to minimise the difference between winter and summer.

For self consumption and selling to the grid optimising for all year round is normally best as you get the greatest volume of kWh.

Optimising for the summer is just odd. But if you don't know how to measure the power you generate I guess it's academic.

I've already explained this. Optimizing for winter just doesn't result in worthwhile gains. Yes, you can do it, but you'll get miniscule improvement because the sun simply doesn't shine much in winter.

And the price you'll pay is a BIG loss in energy in the summer.

So you need to weigh it all up. And my conclusion is that you CANNOT get off grid though solar alone in winter. You need another strategy. So it makes more sense to capitalize on what you can get in summer.

But it's a judgement call.

Correct, you generate less in the summer, when you have more than enough, and more in the winter when you don't have enough.

Here again are the numbers I got from PVGIS, and I've added the best summer month figure too:

35d - 1,017kWh pa, 36kWh Dec, July 125kWh
50d - 1,008kWh pa, 42kWh Dec, July 115kWh
60d - 974kWh pa, 44kWh Dec, July 106kWh

using your summer optimized figure of 22d, the same location gets (per kWp):

22d - 983kWh pa, 29kWh Dec, July 128kWh

You may disagree, you may not understand, but I'd suggest that the 60d generation package is far, far superior to the 22d package. If you really are interested in minimising grid import, and the potential for going off-grid, then you would absolutely be optimising for winter generation, not summer generation.

In my personal case, I have shallow pitched E/W arrays, and generate more than enough in the summer. I have plans, and even some of the necessary kit to add a south facing, steep pitched (60d or 70d) ground mount. Just 2kWp of additional panels would double my current December generation, when I need it most.

Please don't get me wrong, I have no issue with you trying to maximise summer, and minimise winter generation for yourself, but I utterly disagree with your claims, statements and confusing numbers, as regards maximising the potential of PV, which involves considering not just supply, but also demand, and how best to manage the two. I also suspect that your claims about PV, generation, winter, summer etc, are based on your theories, and not on the realities, hence why I (and others) have supplied actual numbers for comparison.

If you believe that the above 22d line is better than the 60d line, then so be it, but if given the choice, I would choose the 60d option without hesitation.