Solar panels: records of actual performance

[lw395]

Bloke down the road has a single 250W panel which he puts horizontal on his motorboat. He's moored fore and aft so he gets next to no actual shading apart from sun below the hill type of thing..
He runs a monitoring/alarm system, tops up his batteries and runs the fridge 24/7 more than 6 months of the year. This is South Coast UK. He can turn his fridge or heater on by SMS, and get SMS messages for things like low battery or intruder alarm.
I would think a lot is possible by spending a bit on modernising the monitoring and turning off everything which isn't needed.
I say modernising, all that SMS control and picture message alarm stuff is old hat now, possibly the up-to-the-minute gadgets are not the most frugal on power? 2G phone modules were pretty low current when I was playing with them over 10 years ago. A lot of people are using wifi and so forth now which can be surprisingly watty.

 

[Mistroma]

Bloke down the road has a single 250W panel which he puts horizontal on his motorboat. He's moored fore and aft so he gets next to no actual shading apart from sun below the hill type of thing..
He runs a monitoring/alarm system, tops up his batteries and runs the fridge 24/7 more than 6 months of the year. This is South Coast UK. He can turn his fridge or heater on by SMS, and get SMS messages for things like low battery or intruder alarm.
I would think a lot is possible by spending a bit on modernising the monitoring and turning off everything which isn't needed.
I say modernising, all that SMS control and picture message alarm stuff is old hat now, possibly the up-to-the-minute gadgets are not the most frugal on power? 2G phone modules were pretty low current when I was playing with them over 10 years ago. A lot of people are using wifi and so forth now which can be surprisingly watty.

I have data from 2012-2019 in a variety of locations. However, you should be able to get everything you need from JRC Photovoltaic Geographical Information System (PVGIS) - European Commission. It is a pretty good model with a lot of historical data and I have always found that the results I measured were pretty close to predicted.

I found the old version easier to use but the current one isn't that bad. Just work in kW and kWh and ignore the fact you might have 0.1kW panel. Entering a 200 kW panel size gives nnn kWh output but you just interpret it as having a 200 W panel and output is nnn Wh.

Step 1: Select your location on the map

Step 2: Try Off-Grid tool

Enter panel size 100W (ignore fact it is actually 100kW as already mentioned)
Set slope to 0 degrees
Click visualise or download CSV
Monthly output is shown
Just divide by days in month to get daily output in kWh per day (ignore kWh as it is Wh as your panel is in W, not kW)


You can might try hourly data tool with 0 degree slope and 0 degree azimuth for a range of years from 2005-2016 for historical data.
The off-grid tool should be all you need.

 

[Baggywrinkle]

I have data from 2012-2019 in a variety of locations. However, you should be able to get everything you need from JRC Photovoltaic Geographical Information System (PVGIS) - European Commission. It is a pretty good model with a lot of historical data and I have always found that the results I measured were pretty close to predicted.

I found the old version easier to use but the current one isn't that bad. Just work in kW and kWh and ignore the fact you might have 0.1kW panel. Entering a 200 kW panel size gives nnn kWh output but you just interpret it as having a 200 W panel and output is nnn Wh.

Step 1: Select your location on the map

Step 2: Try Off-Grid tool

Enter panel size 100W (ignore fact it is actually 100kW as already mentioned)
Set slope to 0 degrees
Click visualise or download CSV
Monthly output is shown
Just divide by days in month to get daily output in kWh per day (ignore kWh as it is Wh as your panel is in W, not kW)


You can might try hourly data tool with 0 degree slope and 0 degree azimuth for a range of years from 2005-2016 for historical data.
The off-grid tool should be all you need.

Thanks for that link ... been looking for it on and off for ages, I used that site in my original calculations and then couldn't find it again. ... just plugged the numbers in and it corresponds almost exactly to the historical performance of my 300W instalation. Brilliant.

 

[Halo]

Wouldn’t it be better to put your boat on the hard for the winter rather than leaving her swinging about in the gales. You are bound to get some chafe. Ashore you can then have mains electric and keep her nice and dry below. If she is worth all that security and monitoring she is worth looking after in the winter


I have had 3.5 kw of solar panels on my roof for 9 years. On a perfect spring day they produce up to 22kwh. On a dark wet December day it can be as little as 200 wh. This gives a ratio of 110\1 for a perfectly aligned unshaded array. Wherever you mount your panels you can’t be sure of alignment on a swinging mooring.

 

[TwoHooter]

.....However, you should be able to get everything you need from JRC Photovoltaic Geographical Information System (PVGIS) - European Commission.

That site didn't work for me - I'll give it another try.

Wouldn’t it be better to put your boat on the hard for the winter ....

That is another possibility but it isn't actually that much cheaper in a lot of marinas where the annual berthing fee is not much more than a winter on the hard plus summer berthing fees. The swinging mooring I am looking at would cost only 37% of our current marina.

 

[lw395]

I have data from 2012-2019 in a variety of locations. However, you should be able to get everything you need from JRC Photovoltaic Geographical Information System (PVGIS) - European Commission. It is a pretty good model with a lot of historical data and I have always found that the results I measured were pretty close to predicted.

I found the old version easier to use but the current one isn't that bad. Just work in kW and kWh and ignore the fact you might have 0.1kW panel. Entering a 200 kW panel size gives nnn kWh output but you just interpret it as having a 200 W panel and output is nnn Wh.

Step 1: Select your location on the map

Step 2: Try Off-Grid tool

Enter panel size 100W (ignore fact it is actually 100kW as already mentioned)
Set slope to 0 degrees
Click visualise or download CSV
Monthly output is shown
Just divide by days in month to get daily output in kWh per day (ignore kWh as it is Wh as your panel is in W, not kW)


You can might try hourly data tool with 0 degree slope and 0 degree azimuth for a range of years from 2005-2016 for historical data.
The off-grid tool should be all you need.

It may help to reduce your kWh from kW of panels to 'equivalent hours of full sun'.
Then what drives your 'budget' is how many consecutive 'dark days' you need to cope with.
A 'dark day 'in January might be something like equivalent to about half an hour of sun.
Then you need to decide how likely it is you'll get more than 3 in a row.
And what the consequences of getting a whole dark week would be.

Some people stop doing everything that not 'essential' after one or two dark days.
Depends what your objectives are.
But weighing it all up, many installations end up justifying a certain amount of wind power.
You see it on things like roadside monitoring.

 

[Mistroma]

It may help to reduce your kWh from kW of panels to 'equivalent hours of full sun'.
Then what drives your 'budget' is how many consecutive 'dark days' you need to cope with.
A 'dark day 'in January might be something like equivalent to about half an hour of sun.
Then you need to decide how likely it is you'll get more than 3 in a row.
And what the consequences of getting a whole dark week would be.

Some people stop doing everything that not 'essential' after one or two dark days.
Depends what your objectives are.
But weighing it all up, many installations end up justifying a certain amount of wind power.
You see it on things like roadside monitoring.

Yes, I modelled that years ago. It gets pretty complex even daily as some output drives fridge etc. at around 100% but some output to battery is wasted because of variable charge efficiency. Then you throw in variability over days and start relying more on batteries but getting higher charge efficiency. I try to charge laptops, tablets and phones when domestic batteries are at 100% to use any waste solar output.

Not such a problem in Greece as dull days are widely spaced. I manage pretty well during the peak summer with 345W. I have a spare 100W which helps at either end of the season (plus a small wind-gen). However, not nearly enough if I wanted to stay over the winter as solar output falls off a cliff. Not a problem as I'm not on the boat over winter.