Solar panel orientation

JKenH

I came across this article from 2014 which suggests an E-W configuration is best for solar panels - maybe not for maximising peak PV but certainly good for the grid and maybe, of more interest, better for day to day living.

(I have reproduced the text of the article in a separate post - see below - but here is a link to the original article.)

https://www.dropbox.com/s/dhyt5wjotgvkkji/Most%20solar%20panels%20are%20facing%20the%20wrong%20direction%2C%20say%20scientists%20-%20Telegraph.pdf?dl=0


I am a late adopter and not benefiting from the super high FiT rates of the pre 2012 and even pre 2016 installations. I also have a (nominally) E-W installation. I had deferred going solar because our roof could not accommodate South facing panels but as the cost of solar PV has come down I have eventually committed. My 2 roof slopes are actually 100* E of S and 80* W of S (if that makes sense) so would expect the W roof to be a bit better than the E roof hence I biased the install 14 panels W and 12 E. I could have got even more on the W roof but fancied a more even spread of power during the day as I no longer have to desert the house all day to make a living.

I have noticed from the bout my generation post that I am consistently underperforming those with S or close to S facing panels and if the PVGIS stats are to be believed things are only going to get worse as the sun drops lower and the days shorten. I am in theory only going to get about 40% of what I would expect from a S facing set up in the depths of winter. Will things really be that bad?

I have noticed that in cloudy weather the output, irrespective of time of day, from the 2 inverters is much closer to a 12E/14W split, ie the low level diffuse PV seems less dependent on orientation (although looking at recent Oscar scores over the last few quite cloudy days here the S panels are still considerably more productive). Do the PVGIS figures take this into account and what is the experience in practice?

JKenH

This is the text of the article

Most solar panels are facing the wrong direction, say scientists
In northern hemisphere most solar panels point south. But west-facing panels are able to generate more even flow of electricity than spikes of energy at lunchtime

Most solar panels are facing the wrong direction, say scientists
Thousands of people have spent vast sums of money installing eco-friendly solar panels but most will have probably had them fitted facing the wrong way, according to energy experts.

The solar power industry is being urged to reconsider its approach to installing panels after one of the UK!!!8217;s leading experts, Professor Ralph Gottshalg of Loughborough University says too many solar panels are facing in the wrong direction.

Professor Gottshalg said Germany has too many solar panels which means that its grid is disrupted on sunny Summer lunchtimes with a flood of solar power so cheap it has to be almost given away.

He is urging to the UK to follow Germany!!!8217;s recent policy of putting panels on east-west facing roofs to smooth the supply of power during the day and prevent spikes of power at midday.

Conventional wisdom in the northern hemisphere is to face solar panels south so they get the most exposure to sunlight during the day.

Architects and installers, as a rule, use this approach all the time particularly on home solar panel installations.

In November, American research revealed that panels facing west may actually get more energy from the sun, and at more convenient times.

The study was carried out by the Pecan Street Research Institute, who studied homes with solar panels in Austin, Texas.

Scientists found that when homeowners faced their panels west they were able to generate more electricity each day.

They also generated more electricity in the afternoon, when power grids experience peak demand.

Though the increase was small - just two per cent - experts said it would certainly add up over the years.

Add to this the afternoon boost, reducing grid dependence during peak hours by 65 per cent as opposed to 54 per cent for south facing panels, could have widespread efficiency implications beyond single homes.

Professor Michael Walls, of Loughborough University said: !!!8220;There are half a million installations in the UK facing south. To maximise the amount of power produced by those panels, facing south is correct.

!!!8220;What we are saying that if you have the solar panels facing east-west then you can even out the power during the day. You may lose about 10 per cent of power if you go east-west but this addresses a problem that exists in Germany where because everything is facing south, you get this peak power at midday which is very difficult for the grid to cope with.

!!!8220;So in Germany they are advising people to go east-west so they are smoothing out the supply of power from all these solar panels. We get similar spikes of power too, although it wouldn!!!8217;t make sense for people to change their solar panels if they have already been installed.

!!!8220;In total we have 2.8 Gigawatts of solar in the UK but Germany has approaching 20 Gigawatts. In Cornwall they can!!!8217;t install any more solar panels because the grid can't handle it.!!!8221;

Solar panels are made up of photovoltaic (PV) cells that are layered in semi-conducting material, usually silicon.

When light shines on the cell it creates an electric field across the layers. The stronger the sunshine, the more electricity is produced.

In the UK, the average domestic solar PV system is 3.5 to 4kWp and typically costs from £5,500 to £9,500.

A 4kWp system can generate around 3,700 kilowatt hours of electricity a year !!!8211; roughly equivalent to a typical household's electricity needs.

As well as this, households using a solar panel will be paid a minimum sum for all electricity generated by their system, known as the Feed-In Tariff (Fit).

The Fit currently stands at 14.38p per kilowatt hour (kwh) for each unit of electricity created, providing an income of around of around £785 a year.

Martyn1981

E/W is fine economically since the ability to install twice as much PV usually means the cost of a larger system is about 80% of that (per kWp installed) of a smaller single roof south facing system. So the two can balance each other out.

But ..... whilst 80% of south facing sounds ok(ish), you'll find most of that missing 20% is in the bottom 6 months, and since those 6 months produce less generation (E/W or S facing) then the impact is pretty painful.

My location simply selecting on PVGIS 1kWp at 35d pitch south facing and west facing I get the following (in kWh's):

May and June south facing are 123 & 123
for west facing it's 112 & 116 so pretty much fine

December south facing is 30.4
west facing is 13.6 ....... not so good.

Batteries will even out the daytime when generation is high and make up for low gen in the morning and evening for a south facing system, but sadly nothing much we can do about low winter gen.

I'm planning a small 4 panel install in the garden in a few years, perhaps 1.2kWp, and all at a steep pitch 50d or 60d to maximise the winter gen. Going back to the PVGIS figures above, 1kWp at 50d pitch south facing would give 115 in May and 34.2 in Dec.

jimjames

JKenH wrote: »

Most solar panels are facing the wrong direction, say scientists
Thousands of people have spent vast sums of money installing eco-friendly solar panels but most will have probably had them fitted facing the wrong way, according to energy experts.

While I appreciate the sentiment behind the article my panels are not facing the "wrong" way, they are facing the only way that is possible on my house and that is South facing. There may be options for other houses that have different roof configurations but our choice was south or no solar.

pinnks

Pretty much the same here too. I have the main ridge running N/S, so main roof broadly west-facing. On the east side I have an E/W ridge, meaning I can only really put PV on the south and north-facing parts of that roof.

I could in-fill with 1 east-facing panel on the south end of that main east side and about 4 panels at the north end but there would be so much shading as to challenge even SE.

So, I settled for a 3,500Wp system on the west-facing and 1,750Wp on the south-facing parts of my roof layout.