Solar PV novice - Generation Meter Readings

Usky

Good morning all,

I'm a solar pv newbie; just had a 15 panel Sanyo 3.75Kw array installed with a Fronius inverter. Sadly the inverter is tucked away in an inaccessible corner of the loft and I've just ordered an Owl monitor so I can keep track of what's going on easily. The house is in Monmouthshire, faces south, south east and the roof angle is 30 degrees. There are no obstructions shading the panels.

I have a question about my generation meter readings. Am I being paranoid, or would you expect higher generation figures than:

• Day 1: 29/01: Overcast: 2.33 units
• Day 2: 30/01: Overcast & Wet: 0.82 units

Bizarrely I thought Sunday was a darker day than yesterday despite being drier, but my panels obviously decided otherwise.

I'm tempted to get in contact with the installers, but thought it wise to ask advice from other people who have solar pv first. What do you guys think? Is there an issue here, or am I just expecting too much from my installation on a dull day?

Usky

Dave_Fowler

Usky wrote: »

Good morning all,

I'm a solar pv newbie; just had a 15 panel Sanyo 3.75Kw array installed with a Fronius inverter. Sadly the inverter is tucked away in an inaccessible corner of the loft and I've just ordered an Owl monitor so I can keep track of what's going on easily. The house is in Monmouthshire, faces south, south east and the roof angle is 30 degrees. There are no obstructions shading the panels.

I have a question about my generation meter readings. Am I being paranoid, or would you expect higher generation figures than:

• Day 1: 29/01: Overcast: 2.33 units

• Day 2: 30/01: Overcast & Wet: 0.82 units

Bizarrely I thought Sunday was a darker day than yesterday despite being drier, but my panels obviously decided otherwise.

I'm tempted to get in contact with the installers, but thought it wise to ask advice from other people who have solar pv first. What do you guys think? Is there an issue here, or am I just expecting too much from my installation on a dull day?

Usky

Sounds about right to me. Figures at this time of the year average around 4kWh per day. But when you get a good sunny day giving 12kWh the cloudy days must be 1 or 2kWh otherwise the average figure would not be right.

Dave F

Usky

Thanks for that Dave - you've obviously found some non-biased average figures somewhere, the only ones I turned up in my brief search this morning were from manufacturers and suggested rather larger yields (surprise, surprise).

Dave_Fowler

Usky wrote: »

Thanks for that Dave - you've obviously found some non-biased average figures somewhere, the only ones I turned up in my brief search this morning were from manufacturers and suggested rather larger yields (surprise, surprise).

There are many sets of figures on pvoutput.org

My 18 month's set of figures are posted here:- http://pvoutput.org/list.jsp?userid=3658

You can select just UK figures by looking at the PV ladder for the UK team and also look at similar postcodes to yours.

Dave F

rogerblack

Dave_Fowler wrote: »

There are many sets of figures on pvoutput.org

I suggest also finding a generation site which submits automatically through the day, so you have a better idea of how generation occurs.
http://www.pvoutput.org/intraday.jsp?id=3744&sid=2940 - for example. (not mine)
The 'daily' results - click below the live graph - are quite enlightening.
It's been under 0.5kWh for a 4kW panel on about 8 days this year so far.

Usky

Thanks for the responses guys; really interesting figures on the pv output web. I have to say I'm much easier in my mind now (and feel a bit foolish thinking there may have been a problem with my installation). For the sake of the record, this morning dawned bright and sunny and although that didn't last my generation meter showed a 1.5 unit increase by midday.

jimjames

It is amazing how much difference the weather does make. Some suppliers might quote the line "you only need daylight" which as you have seen might be technically true in that daylight does generate electricity but to generate serious amounts you need sunlight.

I did a comparison on my blog which showed it was about 10x difference between dull day and sunny during December. This may well vary at different times of the year

http://uk-solarpanels.blogspot.com/2011/12/solar-pv-difference-weather-makes-for.html

Usky

Interesting Jimjames, thanks for that. I'm eagerly awaiting a sunny day now to see how my system performs and get a decent comparison of my own.

jimjames

Today has been the worst day yet since our panels were installed in November 2011.

The total for the day was 0.2kWh. Even on a recent cloudy day we have generated nearly 1kWh so the ability of these thick clouds to block the sun is obviously a lot more than normal cloudy/rainy days.

For the first time the panels had a solid period of over an hour between 12 and 2pm when they were not generating at all. Generally they will always be outputting something around midday even if low output so today was very unusual to get such low output.

Usky

jimjames wrote: »

Today has been the worst day yet since our panels were installed in November 2011.

The total for the day was 0.2kWh. Even on a recent cloudy day we have generated nearly 1kWh so the ability of these thick clouds to block the sun is obviously a lot more than normal cloudy/rainy days.

For the first time the panels had a solid period of over an hour between 12 and 2pm when they were not generating at all. Generally they will always be outputting something around midday even if low output so today was very unusual to get such low output.

Sorry to hear that Jim; I managed a princely 2.43Kwh here today... I'm a happy bunny.

reeac

You'll need to be patient but it may be a consolation to hear that our 2.2kWp system which was forecast to generate 1850 kWh per annum is just coming up to a year old and has generated over 2300kWh.. Take the long term view.