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  1. #41
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    Default Re: Avoiding solar power throwaway

    I have been asking this question about feeding excess power into the grid wherever I can.
    It's the elephant in the room syndrome. People are not forthcoming. (note the silence from Fluffy in this thread!)
    Other forums are the same. People don't want to talk about it!
    Well I guess we'll just have to keep hammering away..

  2. #42
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    Default Re: Avoiding solar power throwaway

    How would you measure what power you are recieving from the sun, see that it is more than you are currently using and then pushing that extra power to a chosen appliance, like a pool pump for instance? Obviously your battery has to be fully charged first. I find that I chow into my battery reserves and then the day runs out and my batteries are 40% charged.

    Another thing, my inverter 'apparently' has a hard switch that makes the panels feed the batteries. Is there truth in the statement that that switch gets 'tired' with age and does not turn on as it is supposed to do? I find that my batteries is not fully charged, even when there is good sun, but the inverter does not relay the solar to charge the batteries.
    Last edited by DrJohn; 2021/05/24 at 06:56 AM.

  3. #43
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    Default Re: Avoiding solar power throwaway

    Quote Originally Posted by Richard Mackay View Post
    I have been asking this question about feeding excess power into the grid wherever I can.
    It's the elephant in the room syndrome. People are not forthcoming. (note the silence from Fluffy in this thread!)
    Other forums are the same. People don't want to talk about it!
    Well I guess we'll just have to keep hammering away..
    It very much depends on your local municipalities rules and regulations. In Cape Town it does not seem to be worth it unless you have a very large setup. See below my thread.

    https://www.4x4community.co.za/forum...Cape-Town-SSEG
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  4. #44
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    Default Re: Avoiding solar power throwaway

    What I do - assuming sunny days:
    10pm till the sun takes over, I draw 800w from the inverter.
    9am inverter watts go up to 2300w, charge slower, power more loads off solar.
    11am set inverter to 3500w as geyser 1 goes on, powering house and geyser.
    1pm geyser 2 goes on
    3-5pm adhoc loads are switched on.
    5pm set inverter to 800w for evening use AND don't use batteries. As end of day, last sunlight, all is used with rest of cooking loads being for Eskom.

    The above done on 4.2kw panels, that's what my loads need over 12 months to cater for average consumption.

    SOC: Right through the day, when SOC is i.e.
    37%, SOC moves up to 35.
    43%, SOC move up to 40,
    47%, SOC move up to 45%
    and so forth, to reach 100% SOC by 5pm, done automatically.
    The above works well with sunny days, which we have most of the year.

    Alternatively once can also use NodeRED to set the inverter max power based on panel performance, getting the similar result.

    The core behind all of this is to:
    1) shave off the 24/7/365 loads using batteries and panels, the loads that costs the most over 12 months.
    2) keep the large heavy loads away from the batteries - weather dependent.
    3) IF clouds move over and batteries must be used, only % points are used to the min SOC setting at the time.
    4) And loadshedding is not an issue, as the Critical Loads can comfortably fit on whatever SOC the batteries are at.

    With all the above, the regular everyday loads are sorted automatically, scheduling adhoc loads during the rest of the day like say 3pm, dishwasher/dryer goes on etc.

    Conclusion:
    IF one uses a bitt more Eskom due to weather, that is too expensive to try and sort that.
    Also learnt, don't try and micromanage production, sort the average first, the schedule big loads, or one can get caught in a endless loop, costing a ton more, with no ROI ever on that.
    Focus on the data you have, work those average numbers.
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  5. #45
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    Default Re: Avoiding solar power throwaway

    We are completely off-grid on a small holding, so no option to feed back, and with us having to pay a monthly fee just for the connection, would probably not be worth it anyway.

    I have 2 DB boards, one is for the house and is always on. The other one is on a relay and only comes on if battery is full enough, and on here we have all the outside plugs, swimming pool pump, dam pump, electric geyser, swimming pool heatpump, car charger and so on.

    We sold all our petrol appliances on the small holding, and got electric ones. Lawn mower, bush-cutter, weat-eater, chain-saw, log saw, log splitter, etc.

    Most of our consumption in the mornings go into the electric car, then when my wife leave at about lunch and start driving the kids around, the pool, heat-pump, geyser and all the other things switch on.

    We also have an induction stove top and use this more than we use the gas stove. And maybe small, but in the day we use an electric kettle, you can also pour this into a flask for later.
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  6. #46
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    Default Re: Avoiding solar power throwaway

    Impressed by the practical knowledge in this thread.

    I am at the point of buying and installing a 5kW system in my home.
    The one thing I have learnt so far is that you can damage your invertor quite easily. (I really do not want to do that)

    I am looking at a Solis grid tied hybrid. For starters I will only install about 2 kW of battery.

    I want to oversize the panels. Ie installing 6kW or more on my 5kW invertor.

    So here is the question:
    1 What happens when I supply more kW from the panels than the invertor can convert. Will it protect itself by just limiting to what it can, or will it shut down or will it get damaged?

    2 Must I always have less panels kW than what my invertor can handle??

    (To be in line with today I am trying to flatten the curve of my supply on the high side, and not the low side)

  7. #47
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    Default Re: Avoiding solar power throwaway

    Quote Originally Posted by Pieter de Waal View Post
    I want to oversize the panels. Ie installing 6kW or more on my 5kW invertor.

    So here is the question:
    1 What happens when I supply more kW from the panels than the invertor can convert. Will it protect itself by just limiting to what it can, or will it shut down or will it get damaged?

    2 Must I always have less panels kW than what my invertor can handle??

    (To be in line with today I am trying to flatten the curve of my supply on the high side, and not the low side)
    1 - You can oversize, inverter draws from the panels, panels are not "pushing" the power ... in totally laymen's terms.
    2 - You have more than the inverter supply at max draw, like me, have a 5kva (4kw) but I know that 99% of the time I don't need more than 3.5kw, so the 4.2kw is there for winter, not summer.

    Determined that with data.

    Maxed the 2kw array with ease. Added more panels to 3.5kw. Maxed that with ease in winter, needed 500w more ito panels. So I added 2 more panels and now I have 4.2kw.

    I can go to 7kw I want, all that will mean is that I will have more power earlier and later in the day, midday the MPPT will clip the max power If it the draw exceeds the design specs of the MPPT.

    BUT ... here is the titbit we learnt in Cpt.
    If you install a 5kva, or 10kva or even 15kva inverter, a inverter that cannot be limited to 3.5kw max when connected to a DB board, then you have to limit the max the array can produce i.e. 3.5kw.

    Now because panel angles differ and all that, a i.e. 5kw array can max 3.5kw peak hours, you get a engineer to work it all out and submit that to CoCT, that your 5kw array can only do a max of 3.5kw peak hours.

    So check with your local authorities.
    Last edited by the_terrible_triplett; 2021/05/24 at 12:33 PM.
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  9. #48
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    Default Re: Avoiding solar power throwaway

    What TTT said.

    Remember to distinguish between the charger (built in MPPT) and the inverter.

    Although I don't know Solis, I can guarantee you the MPPT will have a maximum upper threshold for volts and watts.

    As an example, my MPPT can handle 150Volt max and 2000W in 48V configuration.

    The watts is not that crucial as the inverter will only take what is required to meet load demands, but NEVER EXCEED THE VOLTS. The smoke will escape.

    Make very sure what yours can handle, especially when you plan to oversize. You will have to look at best serie/parallel configuration for your strings taking the max limits into consideration.
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  11. #49
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    Default Re: Avoiding solar power throwaway

    Richard I live in East London. Had to register with the city council electricity department, and get a new meter, and a new billing system applied.
    Now feeding into the grid, as we speak....
    Needed is the right meter, a receptive municipality, and all the red tape to be sorted, then you're done.
    D.

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  13. #50
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    Default Re: Avoiding solar power throwaway

    Quote Originally Posted by IanK View Post
    Richard I live in East London. Had to register with the city council electricity department, and get a new meter, and a new billing system applied.
    Now feeding into the grid, as we speak....
    Needed is the right meter, a receptive municipality, and all the red tape to be sorted, then you're done.
    D.
    So what is total costs to feed back (once off & monthly fee)
    ..And the scale of watts feeding back into the grid - remuneration for feeding in?
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  14. #51
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    Default Re: Avoiding solar power throwaway

    Quote Originally Posted by IanK View Post
    Richard I live in East London. Had to register with the city council electricity department, and get a new meter, and a new billing system applied.
    Now feeding into the grid, as we speak....
    Needed is the right meter, a receptive municipality, and all the red tape to be sorted, then you're done.
    D.

    Did you have to pay for the meter and how much is the differential rate between use and feedback?

  15. #52
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    Default Re: Avoiding solar power throwaway

    Quote Originally Posted by the_terrible_triplett View Post
    1 - You can oversize, inverter draws from the panels, panels are not "pushing" the power ... in totally laymen's terms.
    2 - You have more than the inverter supply at max draw, like me, have a 5kva (4kw) but I know that 99% of the time I don't need more than 3.5kw, so the 4.2kw is there for winter, not summer.

    Determined that with data.
    Thank you guys. I will gladly overdo it on the panel sizing.

    It will give me more time when I am maxed out and thus producing more kW per day. Also with overcast I will get better returns. At 9 in the morning I may have 2kW instaed of 1 kW.


    Now the next big question for me:
    I will have shadow spots moving across my panels.
    Are the shadow compensated panels really worth it or is the real improvement negligible ?

  16. #53
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    Default Re: Avoiding solar power throwaway

    Quote Originally Posted by Pieter de Waal View Post
    Thank you guys. I will gladly overdo it on the panel sizing.

    It will give me more time when I am maxed out and thus producing more kW per day. Also with overcast I will get better returns. At 9 in the morning I may have 2kW instaed of 1 kW.


    Now the next big question for me:
    I will have shadow spots moving across my panels.
    Are the shadow compensated panels really worth it or is the real improvement negligible ?
    Pieter bear i mind you will be using 2 strings with say 6 panels in series. All panels today have bypass diodes in to still work at say 33 or 66% if the shade happens to be on a column of cells. Shade will reduce your output as per the level of shade on the worst panels shading. If only 1 string has shade the 2nd string would deliver at full tilt.
    With some shade on 1 panel in series it is not all or nothing.
    Last edited by ekkekan; 2021/05/24 at 04:20 PM.

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  18. #54
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    Default Re: Avoiding solar power throwaway

    I am planning, so i cannot say that this answers the original question, but i think this is the way to use 'surplus' power in daytime.
    Regards
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  20. #55
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    Default Re: Avoiding solar power throwaway

    Roelof

    Your problem is not unique and storage of energy from solar is a challenge
    If your system is big enough to cater for all loads then you are well off. Well done.
    I would then invest in a electric vehicle as a 50 -75kW battery will take quite a bit of energy to charge back up.
    Depending on how far you drive... your system at home might be still to small.

    My challenge with the solar system is to shift the energy from day to night usage -
    I am considering a second geyser as the use of a single geyser does not work if one family member is using the geyser in evening then the morning it is cold due to the cold water inflow.
    So the geyser needs to be switch on from either battery power or ESCOM. Libdoo nicely describe the solution above.

    In Europe heating homes with circulating water thought the houses are fairly common: Either prebuild into the houses flooring or pipe systems feeding into fin grids situated against the walls in rooms.
    Not sure but if I stayed in Sutherland that would be a nice solution. Depending on where you stay and what your needs are.

    My latest discovery is a company that has a trial run on storing energy into ground heating it up to 600 degC and then extracting the heat with water specifically for heating homes. Not sure if this is practical in SA.
    I'd rather go for heat storing in a water geyser.

  21. #56
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    Default Re: Avoiding solar power throwaway

    Jou huis se mure vloere en meubels is groot stoorplek van hitte of koue.
    Gebruik jou oorvloed dag energie om die huis se basiese temperatuur te reguleer met 'n aircon wat dan deur die dag jou huis warm of koud maak.
    Jy gaan minder heaters vanaand kan loop want die hele huis is daai paar grade al klaar warmer.

    Kyk byvoorbeeld as daar skielik n koue front inkom, vat dit jou huis 2 of drie dae om af te koel. Nou kan jy daai selfde gedagte gebruik om jou huis se basis temperatuur te reguleer.

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  23. #57
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    Default Re: Avoiding solar power throwaway

    Quote Originally Posted by Pieter de Waal View Post
    Jou huis se mure vloere en meubels is groot stoorplek van hitte of koue.
    Gebruik jou oorvloed dag energie om die huis se basiese temperatuur te reguleer met 'n aircon wat dan deur die dag jou huis warm of koud maak.
    Jy gaan minder heaters vanaand kan loop want die hele huis is daai paar grade al klaar warmer.

    Kyk byvoorbeeld as daar skielik n koue front inkom, vat dit jou huis 2 of drie dae om af te koel. Nou kan jy daai selfde gedagte gebruik om jou huis se basis temperatuur te reguleer.
    I like this idea of the heat pump raising the temp in the house during the day if even by only 3-5 degrees.

    My house's ground floor is very cold in winter but still cool enough in summer so as to not need aircons. This is where I need to have the heat pump.

    The 2nd floor is where we need aircons during summer due to it getting much more sun, but during winter this is fine and there we only need our electric blankets come sleep time.

    Definitely I will be looking into this thanks!
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  24. #58
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    Default Re: Avoiding solar power throwaway

    This whole thread and all it's ideas can be summarised into six words.

    "Make hay while the sun shines."
    Cheers

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  25. #59
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    Default Re: Avoiding solar power throwaway

    Quote Originally Posted by Fluffy View Post
    This whole thread and all it's ideas can be summarised into six words.

    "Make hay while the sun shines."
    The key though, is what type of hay

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  26. #60
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    Default Re: Avoiding solar power throwaway

    Quote Originally Posted by Kamakazi View Post
    So what is total costs to feed back (once off & monthly fee)
    ..And the scale of watts feeding back into the grid - remuneration for feeding in?

    I am also in East London. Feeding back around 300 to 400 kWh per month.

    Costs:
    You are required to get a smart meter that can measure power in both directions.
    This is R8200 but possibly free if your already have a smart meter or is up for install but can not confirm. I paid R8200

    You then pay a R183.23 connection fee, normally R53.04 for post paid.

    For that you get a lower kWh rate of R1.820 vs R2.3595 for post paid for energy imported
    You then get R0.5628 for every kWh you export.

    Export Import ratio of 3.23:1, which means defiantly better to use than to export.

    I have DC elements on my geyser. Can change output power from 0-400kw in 10w steps, this tracks batter power and holds it around 0W once battery is full.
    Pool Pump is also controlled by the system and turns on once we hit a charging rate and off once we start discharging, it is rate limited so it only changes state every 10mins.

    Batteries do make financial sense for us but increased payback to 8years. We are using FreedomWon lithium iron phosphate batteries with 2x Victron Multiplus 2 and run everything regardless of grid or no grid.

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