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Solar panels - spread of generation through the day

  • 08-03-2023 11:40am
    #1
    Registered Users Posts: 11


    Hi, Sorry for the newbie question - I had a look but can't find the answer. We are looking at solar panels, with or without batteries, someone is home most of the time. I'm wondering, for the Apr-Oct timeframe (anything else is a bonus) how the spread of generation runs through the day? So, for example with say a 3.6kwp system we should be net exporters for those months, but if e.g. for the first couple of hours of the day or in late afternoon we were not producing enough to run the base load and computers (WFH) then batteries become more viable. Does anyone have figures/graph of production through the day? Or can you point me at them? Thanks.



Comments

  • Registered Users Posts: 6,896 ✭✭✭circadian


    It's hard to say, location, direction of panels and roof angle can make a difference. From personal experience the battery is handy, if not expensive.


    In winter, if there's a bright morning and dull afternoon you've at least avoided relying completely on the grid for another few hours.



  • Registered Users Posts: 11 fiona111


    I'm disregarding winter - that is just a bonus. South facing, 30 degrees. I know figures will vary depending on, as you say, location, direction and angle, but percentages of daily production for each hour should be roughly comparable?



  • Administrators, Computer Games Moderators, Sports Moderators Posts: 32,127 Admin ✭✭✭✭✭Mickeroo


    Here's my best day from last April with a 3.72KWp system, s/sw facing in Mayo. Should give you an idea of when you start generating and stop on a good day at that time of year.





  • Registered Users Posts: 8,441 ✭✭✭micks_address


    Here's our spread from yesterday (23kwh generated).. 7kwp system.. 4kwp south east, 3kwp north west. North west string should start to produce more later in the month as sun gets higher in the sky.. look at the daily pv production figures thread.. should be some south facing systems posted there. Dont disregard winter.. south facing can do well on any bright day.. of course days are shorter but ive seen some crazy numbers posted for December/Jan on south facing systems.. yesterday i was working from home so did 4 wash-loads and a drier run which i reckon would have cost about 7 euro on peak electricity rates.. a battery will definitely help balance things out.. we charge nightly on nightboost rates and then discharge during the day to run the house.. hardly any peak rate usage at all.. our nightboost rate is about 12 cents kwh.. between 2 and 4am with EI..




  • Registered Users Posts: 545 ✭✭✭idc


    With batteries and a day/night rate you can also charge the battery on cheap rate to use during the daytime. My last 2 monthly bill i used a total of 22 kWh at day rate (and that included Xmas day where we definitely used the battery up completely due to all the cooking) battery and solar powered the house during for the rest of the time between 8am and 11pm!

    In the summer with battery I should not need to even use the grid at all, only complication with that is I have an EV now and FIT may impact - ie better to export than use at night based on rate i have, although while on deemed FIT better to use as much in house.

    Your best bet is to fill in details of size of system/location/orientation etc here JRC Photovoltaic Geographical Information System (PVGIS) - European Commission (europa.eu)

    I've only really used the Grid connected yearly projection option, but i did recently try the hourly data - but that will produce tonnes of data to an excel file!!



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  • Registered Users Posts: 11 fiona111


    Those are interesting figures @Mickeroo and @micks_address - exactly the sort of thing I was looking for. Of course, in both cases those are for sunny days, which is fair enough. Looking at your figures @Mickeroo with a similar sized system the basics would be covered 9am to about 7pm in May, with more needed for e.g. washer and dishwasher, which should be run 12-4pm if no battery. And @micks_address, if I halve your figures to bring it to a similar sized system then a good day in December would see the basics covered 9am-3pm. Ok - so to work out the feasibility of a battery then I need to look at usage outside those times, FIT rates and night rates to see if it was worth going for full usage in the summer and night rate battery top up in the winter. Thanks!

    Edit: And thanks @idc - that came in while I was typing.



  • Administrators, Computer Games Moderators, Sports Moderators Posts: 32,127 Admin ✭✭✭✭✭Mickeroo


    Just for contrast, here is the worst day I had last April(there was some very brief sunshine in the evening going by the spikes around 18:00):





  • Registered Users Posts: 1,063 ✭✭✭silver_sky


    Check out the app "Sun's Path". It'll show you the times based on your location and orientation.



  • Registered Users Posts: 10,803 ✭✭✭✭the_amazing_raisin


    A lot depends on the orientation of the panels. South facing gives a very strong peak in the middle of the day whereas East-West gives a long spread of power through the day

    One thing I'm learning in the first few weeks is just how much clouds affect your generation, for example yesterday with clear skies I generated 31.4kWh whereas dull overcast Monday I only managed 5.7kWh

    If you're trying to figure out how many panels to install, here's my general advice; cover the roof if you can.

    You'll always find ways to use extra energy (cook dinner at lunchtime for example) and if you have a battery then there's a much better chance to fill the battery from solar with more panels

    It's also easier to add batteries post installation than panels. We've no battery at the moment but are setup for one after the grant gets paid


    As I mentioned, you'll also tend to find uses for extra energy. If you've any plans to own an EV for PHEV for example, they can be charged from solar for some free kilometres. Another popular idea is to use a diverter like an Eddi to heat your hot water from immersions


    If you're handy with some home automation you can have smart sockets that turn on heaters or air conditioners when the sun is shining

    In any case, the bigger the system you install the more money you'll get from the FIT

    "The internet never fails to misremember" - Sebastian Ruiz, aka Frost



  • Registered Users Posts: 4 bobburns007


    Hi fiona 111,

    I use Globalsolaratla.info

    you must input some data ie location, system size, pitch angle and aspect.

    It will give you all the info you’re looking for.




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