9000KWh reliance on grid is no good; how to avoid?

brandnewb

Solar Enthusiast
Currently I draw +- 9000 KWh more from the mains grid than I supply to it in one year.

Earlier I posted this thread
That started it all

TL;DR
I have an 11kw 3 phase EV charge, I 3KW single phase heat pump, a 15KW 3 phase electric heater and several kitchen appliances that draw +- 3KW to run.

I'd ideally go off grid once I have demonstrated it can be done for a year or 2.

What configuration of 3.2v 280AH LifePO4 cells would you recommend?

EDIT
Please ask for more details so I can help you guys help. I am far too inexperienced to think of a better way of explaining myself at this point in time.
 
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curiouscarbon

Science Penguin
Hi!

may i ask, do you want to be able to run all of those appliances continuously at the same time?

that would change the result

good luck with your project!
 

brandnewb

Solar Enthusiast
;) Nah. For example the eheater is seldomly used anymore since I finally have my heating (heat pump, under floor heating, pellet stove) under control.
I just want to be able to run it when needed. One never knows if it might be essential at one time or another

The EV charger is a concern though as my current ev car will only accept the charger at full power (16 amps). The 6 and 10 amps mode it does not accept. And because we charge it at night there is no solar power to back it up. I am working on wind power though as we speak

The heat pump runs continuously during winter times and should have a high priority. I mean I'd rather prepare my dinner on a camping gas stove if that prevents the heat pump from not running and the house slowly turning into ice.
 
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houseofancients

Solar Addict
so you're wanting to know what you need extra in solar panels, or battery ?

9000 / 365 = 24.657534246575 kwh a day

so need about a 25 kwh generation a day ( in summer and winter)

you first need a good hard and long look into shaving down your usage, or as mentioned before, be quite rich ;)
 

curiouscarbon

Science Penguin
roof square meter estimate?

if panels not on roof, approx how many square meters available to place photovoltaics panels?
 

brandnewb

Solar Enthusiast
Basically the question is two fold. How do I store it and how do I generate it.

currently my main roof is already completely full with 44 PV panels +- 12100 Wp. it is 3 phase and grid tied and feeds the house first and what is left over goes into the grid. This house first is nothing special. This is seemingly what happens naturally when tied to the grid as elec flows to the path of least resistance is how i understood it.

I have room left for about the same amount of panels on some other area on my land.
Since we only have a 3 x 25amp mains connection I am not sure if I can simply add that and expect my breakers to remain happy when, ehh I mean if ;), we have good summer days.

I was thinking of heating a huge water storage tank of like maybe 10k liter in my crawlspace and heat that as a thermal buffer by using it as a dump load. Having such an amount of heat storage will also be good news for my heat pump that sometimes cries a little on cold days.
 

Diysolar123

Solar Addict
well, good thing you decided against such high voltages hehe
you need to be very careful with all the electronics at that voltage... you can easily blow out mosfets due to exceeding their maximum voltages, arcing danger goes from "possible" to a certainty with the smallest mistake; DC arcing is nothing like AC arcing...

at that power level you are thinking of it will take very deep pockets and it may make more sense to go with a commercial system.
Actually I would probably just go with a large propane storage tank and generator for the largest components on those difficult low generation days/seasons (a week of cloudy winter days) and sustainable power source with what is reasonable given solar panel space and battery storage needs. Do not shoot for a perfectd solution, but a compromise solution that meets all your needs with multiple technologies.

There is nothing magical about about power generation and consumption...
You have already added up what you want to have, it is just "simple math" taking into account your average power generation from your area to figure out how much panel area you need and for batteries it is just a matter of adding it all up with power losses due to conversions/wire/etc...

it may make more sense to really sit down with a spreadsheet and decide what you can do to reduce you current power demands.
 
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kuranaga

Solar Enthusiast
so you're wanting to know what you need extra in solar panels, or battery ?

9000 / 365 = 24.657534246575 kwh a day

so need about a 25 kwh generation a day ( in summer and winter)

you first need a good hard and long look into shaving down your usage, or as mentioned before, be quite rich ;)
thats an incorrect calculation. He will need different amounts in winter and summer. And the generation will vary during winter and summer. Could be twice as much in winter as in summer or vice versa depending on climate zone
 

DJSmiley

Solar Addict
Note: This applies to NL, since the picture of the distribtion board is from Liander and has some dutch text (eg earth provided by supplier).

For now, local storage isn't a real option if you take the costs involved into consideration. At this moment, up to approx 2030, you still can substract the power from the PV from the amount of used power from the grid.

From 2023 onwards, this will be lower (starting at 89% in 2023). But even with the lower numbers, it's still cheaper than spending $$ on batteries and chargers.

Things might change however, our government isn't know for keeping it's promises well (Eg multiple times adjusting tax benefits for EV despite earlier agreements)

For now, I would make sure your yearly PV generated power matches your consumption.
When installing new PV, I personally would go for a hybrid inverter if available, so you can eventually add batteries.

If I ever manage to find a new house, I'll go for such an option, and see where we are within a few year regarding battery prices and the costs of electricty to see when to install batteries.

3 vs 1 phase is a difficult one. I prefer to 'downscale' to single fase, since thats easier to handle (just add an inverter in parallel if you need more power). With 3-phase, its always a PITA to make a decent separation between the phases without overloading one.

However, on the other hand, with an EV it's preferred to have 3-phase, since the majority of the EV's in europe are either 16A single phase (3.6kW) or 3-phase (11kW), and a 32A (7.2kW) is only on a few (older) models available.

Based on the current available options, I would opt for a single phase house setup, plenty of PV panels, and use the grid for
- EV charging (with seperate metering so it can be company paid)
- additional feeding when needed during winter if the solar panels can't keep up
- Backfeeding to the grid since especially in the summer the amount of PV is way overkill.

For heat storage: I don't see the benefits. 200-300L is generally sufficient for normal purposes. And when you need the heat the most (winter) it's already hard for the PV to provide sufficient power, let alone adding massive amounts of heating power.
 

brandnewb

Solar Enthusiast
He will need different amounts in winter and summer. And the generation will vary during winter and summer. Could be twice as much in winter as in summer or vice versa depending on climate zone
yes, that is indeed my dilemma, hence the wind turbine experiment
 

brandnewb

Solar Enthusiast
For now, I would make sure your yearly PV generated power matches your consumption.
NOt entirly suyr how much I consume. I do know I draw +- 9000 from the grid a year. In a good year my PV system reports a generation of more than 11000 KWh.

In any case I think you are right as that is what is my intend indeed. Just generate an insane amount of power and what ever is left feed back into the heated water buffer
 

brandnewb

Solar Enthusiast
For heat storage: I don't see the benefits. 200-300L is generally sufficient for normal purposes. And when you need the heat the most (winter) it's already hard for the PV to provide sufficient power, let alone adding massive amounts of heating power
In my scenario my current 500l heat buffer is just about adequate. But when my inlaws come and visit we have full house and then I tend to shave off a minute or 5 from showering.

The intended 10k l heat storage is more meant to ease the demand on the heat pump
 
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brandnewb

Solar Enthusiast
3 vs 1 phase is a difficult one. I prefer to 'downscale' to single fase, since thats easier to handle (just add an inverter in parallel if you need more power). With 3-phase, its always a PITA to make a decent separation between the phases without overloading one.
You might well be right but for now I have put it upon me to get comfortable with 3 phase. I am willing to spend the extra effort getting it under control.
 

A.Justice

Swears he didn't start that fire.
If your roof is already full of panels, and unless you build an additional very large ground mount, as well as add batteries, charge controllers, and associated equipment, the best way to make that work would be to decrease your energy use.

Propane and natural gas are both incredibly efficient at heating, you could have a gas stove and gas heat. Check your insulation in the house, 99% of the time insulation can be added (or repaired / replaced) and drafts can be sealed better than they are currently. There's also other roofing materials available that can reflect or attract heat, depending on what you need. I'm going to sound like a window salesman here, but high quality windows really do make a huge difference in heating and cooling as well.

Do you leave any electronic devices running when they're not needed? My computer draws over 2KW per day just sitting there, and one large TV at idol can be around 1KW. Fans left running, game systems, TV boxes, lights left on, inefficient bulbs, and idle draw can use energy very fast.
 

brandnewb

Solar Enthusiast
Do you leave any electronic devices running when they're not needed? My computer draws over 2KW per day just sitting there, and one large TV at idol can be around 1KW. Fans left running, game systems, TV boxes, lights left on, inefficient bulbs, and idle draw can use energy very fast.
yes, on that front I have a lot of disipline to gain. I can't be sure but they way we live our lives careless and all, we probably waste up to 30% of elec and maybe even 50% of hot water (hmm which needed elec to get warm so now I am not sure regarding percentages anymore ;))
 

billt1827

New Member
The short answer is - forget it.

With your consumption and (presumably limited) amount of panels you will not be able to go off grid and it would be a technically complex and very expensive project.

I wanted to do the same thing (only with more modest consumption) and have a system based on a Sunny Island SB8.0, about 15kW peak of PV panels and 13kW of PV inverters with 15 Winston 400Ah cells and a RECBMS battery management system. 1000Ah cells would have been more suitable, but this is a mad hobby project and the cost was not justifiable.

To design a suitable system you need to know 2 things, your peak power consumption and your average daily energy consumption.

The peak power consumption isn't the sum of your appliance consumption, it will be considerably less. The only way to find that out is to log your actual power consumption. In my case the peak consumption was about 8kW for a couple of minutes. This was in the capabilities of the SI8.0 which is rated at 6kW continuous, 8kW for 30 minutes and 9.1kW for 5 minutes.

You should be able to work out your energy average consumption from your power bills, but if consumption and generation aren't measured separately you are going to have to use the logger to measure that too. Once you know your average consumption you can work out what battery capacity you will need. We average about 14kWh a day, so for 3 days worth of storage we would need about 1,100 Ah of battery capacity at 48V and 80% DOD.

Unfortunately the trouble with solar power in our northern latitudes is that it tends not to produce much energy in the winter, when you need it most, especially if you use electrical heating. You need to go over to PVGIS (https://re.jrc.ec.europa.eu/pvg_tools/en/#PVP). That allows you to get a pretty accurate estimate of the generation capacity of your PV array.

For our system PVGIS gives average daily generation varying from 9.7kWh per day in December to 52kWh per day in June. Unfortunately there is significant winter shading so reality will be worse than PVGIS's predictions. We are at about the same latitude as the north of the Netherlands, so shouldn't be too dissimilar to you, although your weather might be better.

As you are highly unlikely to be able to go off-grid entirely there is also the issue of grid connection. You would need to ensure that the system complies with your network operators rules which adds a further layer of difficulty.
 

brandnewb

Solar Enthusiast
To design a suitable system you need to know 2 things, your peak power consumption and your average daily energy consumption.
peak would be around 15Kw when the car is charging, the heat pump running and cooking electrically.
avg. daily during winter time I do not know yet. I'll be sure to measure that coming winter when it is at it's predicted coldest.

Unfortunately the trouble with solar power in our northern latitudes is that it tends not to produce much energy in the winter, when you need it most, especially if you use electrical heating. You need to go over to PVGIS (https://re.jrc.ec.europa.eu/pvg_tools/en/#PVP). That allows you to get a pretty accurate estimate of the generation capacity of your PV array.
last year my PV array on the main roof reached it's maximum size (no more space to fit extra panels there)
1634872184907.png

I can build a second array with similar size elsewhere on the land.
As you are highly unlikely to be able to go off-grid entirely there is also the issue of grid connection. You would need to ensure that the system complies with your network operators rules which adds a further layer of difficulty
I went through the steps involved to be allowed grid feeding my surplus power.

Especially for winter times, when having 88 panels would also not be enough, especially without a good power storage I am dabbling with
I can install up to 5 of them on my main roof and a couple more elsewhere on my land.

Then I think I am out of options in terms of power generation other than inventing a fusion reactor ;)
 

brandnewb

Solar Enthusiast
Then I think I am out of options in terms of power generation other than inventing a fusion reactor
I just figured I can hook up a threadmil to a generator and get in the best shape of my life. I am actually going to do that now I think of it because then finally i'd have a real good incentive to be more active.
 

brandnewb

Solar Enthusiast
Also I think I should be able to run 20KW constant. The car alone can charge for more than an hour at 11KW. Heat pump I believe can go up to 3KW, but usually only draws around 1.4KW even on cold days. I'd have to double check that.
And kitchen appliances also run for more than a few minutes when used properly. My servers are always on the biggest one can go up to 1.6KW

Yeah I think I need to aim for 20KW continues load for my batteries.
 
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