The winter months are brutal!!!

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J_Mack58

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Joined
Apr 7, 2021
Messages
109
Not really severe weather, but for us DIYers relying on the Sun these cloudy days are like Tornados, Hurricanes, earthquakes,Tsunamis and hail storms all in one. We are in survival mode. 15kWh battery is useless if you can’t charge it. Excuse my rant I installed my system in the summer…. This my first winter. Anyway with 1.2kW worth of panels to charge my Powerwall the panels made 1.06kWh guess we had the equivalent of 1 hour of sunshine. My 2.6kW REC panels grid tied through my SMA inverter made 1.471Wh of power for the day. I remember making 16 -20kWh’s/day this pass summer.
How is everybody else doing?
 

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paddy72

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Joined
Nov 17, 2021
Messages
31
You are still lucky. My PV here in Germany achieves about 3...10 % of its nominal power at the best time of the day in November / December.
In some areas you cant solely rely on PV as your only power source - it simply doesn't make sense. You would have to massively oversize the system and in summer you dont know what to do with all the energy. You have to have a mix of sources, hard if you want to live 100% offgrid in some places.
 

Wolf

Active member
Joined
Sep 25, 2018
Messages
1,652
Well that's the problem when living around the 45th parallel or higher. In the summer we get 15+ hrs of solar and in the winter well not much till the reversal on Dec 21. What to do. The only redeeming factor is when you get those crisp clear days and the panels are cold the production is pretty good although for a short period of time. Other than having a system to track the sun, have the panels attitude virtually vertical with a clear southern exposure (not always possible) there is not much we can do, till the azimuth of the sun favors our latitude again. The only redeeming factor is the amount of energy that we can produce during the "good" times sets off the cost of the "bad" times. I am considering a small wind turbine just for kicks and maybe 500W to 1000W of power when the wind blows. Also probably more hassle than its worth but you never know.
Wolf
 

jdeadman

Member
Joined
Mar 28, 2017
Messages
963
that is the biggest problem with solar. to survive the winter you need about tripple the input for the cloudy days. in my latest design (on paper) I have a expected drain of 15kwh per day, To supply that I want 100KwH of storage, 20Kw of Solar and possibly Wind supplement and if possible offset some of the Solar with Hydro if I get a constant water source.
 

Dr. Dickie

Member
Joined
Sep 23, 2020
Messages
286
Yeah, cold front moved throught yesterday, system almost go to full charge (about 3.90V per pack). Cloudy this morning, packs down to 3.69V, and we currently have about 1 amp coming into the battery. If the clouds don't break soon, no way will it get charged up enough to last the night.
 

OffGridInTheCity

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Joined
Dec 15, 2018
Messages
1,862
Mostly because I'm addicted, but setting that aside, I'm planning to expand my battery bank from 81kwh to 140kwh. Presumably, at 80% DOD, in an emergency, I would have 112kwh of useable power to ration over low dips in power. Setting my recent 11 days in a row and counting aside.

With 112kwh, in theory, I could ration it to say 5 days at 22kwh/day to supplement low solar. But bringing this idea in the real world, I realize there's no algorithm (I'm aware of) to sort of do predictive analysis / intelligently start using the reserve in the battery.

For example, let's say history says on average I could have 3 days in a row of 'below base point' sun... so I use reserve to make up for it. BUT then it goes to 4, 5, 6, days - maybe some algorithm to give 80%, 60%, ... stretch out the reserves based on some parameters.

Part of this should include how much to peal off each day of excess to recharge and/or strategic points of when it's required to run a generator to replenish the battery reserve.

Too much writing - but you probably get what I'm trying to say. To accomplish this, one needs a good discharge curve of the battery bank, the ability to turn on/off loads by voltage or DOD.

Anyone heard of such an algorithm?

I'm not a math guy (to create formulas) but I can millions of loops in computer code to maybe brute force some solutions - thinking about it but the goals/parameters are not well defined in my mind.
 

J_Mack58

Member
Joined
Apr 7, 2021
Messages
109
Well that's the problem when living around the 45th parallel or higher. In the summer we get 15+ hrs of solar and in the winter well not much till the reversal on Dec 21. What to do. The only redeeming factor is when you get those crisp clear days and the panels are cold the production is pretty good although for a short period of time. Other than having a system to track the sun, have the panels attitude virtually vertical with a clear southern exposure (not always possible) there is not much we can do, till the azimuth of the sun favors our latitude again. The only redeeming factor is the amount of energy that we can produce during the "good" times sets off the cost of the "bad" times. I am considering a small wind turbine just for kicks and maybe 500W to 1000W of power when the wind blows. Also probably more hassle than its worth but you never know.
Wolf
I actually built a Vertical Axis Wind Turbine (VAWT) 55 gallon drum and a washing machine motor. It worked! To not draw attention I only raised it at night just above my fence. It would have did better if it was up higher. I plan on getting back to that. I need to make the lift automated and lift the turbine higher. The washing machine motor was 3 phase and I have 3 phase to DC modules laying around. I charged a Capacitor bank to 400 volts. Then use a IGBT Buck circuit to chop the DC to charge my batteries at 52 volts. Then the seasons change, wind stop blowing so much and the sun came out....went back to solar and never looked back. Now I'm looking back. The picture is not mines, mines was DIY so imagine it a little not so professional.
 

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J_Mack58

Member
Joined
Apr 7, 2021
Messages
109
Yeah, cold front moved throught yesterday, system almost go to full charge (about 3.90V per pack). Cloudy this morning, packs down to 3.69V, and we currently have about 1 amp coming into the battery. If the clouds don't break soon, no way will it get charged up enough to last the night.
Hello there Doc. Hope you get some sun soon.
 

Dr. Dickie

Member
Joined
Sep 23, 2020
Messages
286
Hello there Doc. Hope you get some sun soon.
Still complete cloud cover, but currently getting 10 amp into the battery, so all should be good. Well, back to 5 amps and no where near charged enough (3.74V per pack).
It helps that I have (theoretically) a 2.8 kW array.
Pretty tiny for most folks, but enough that if I am not using a lot of power, and it is not raining cloudy, it generates enough to get by.
Hope it all works out for you!
 
Last edited:

J_Mack58

Member
Joined
Apr 7, 2021
Messages
109
Mostly because I'm addicted, but setting that aside, I'm planning to expand my battery bank from 81kwh to 140kwh. Presumably, at 80% DOD, in an emergency, I would have 112kwh of useable power to ration over low dips in power. Setting my recent 11 days in a row and counting aside.

With 112kwh, in theory, I could ration it to say 5 days at 22kwh/day to supplement low solar. But bringing this idea in the real world, I realize there's no algorithm (I'm aware of) to sort of do predictive analysis / intelligently start using the reserve in the battery.

For example, let's say history says on average I could have 3 days in a row of 'below base point' sun... so I use reserve to make up for it. BUT then it goes to 4, 5, 6, days - maybe some algorithm to give 80%, 60%, ... stretch out the reserves based on some parameters.

Part of this should include how much to peal off each day of excess to recharge and/or strategic points of when it's required to run a generator to replenish the battery reserve.

Too much writing - but you probably get what I'm trying to say. To accomplish this, one needs a good discharge curve of the battery bank, the ability to turn on/off loads by voltage or DOD.

Anyone heard of such an algorithm?

I'm not a math guy (to create formulas) but I can millions of loops in computer code to maybe brute force some solutions - thinking about it but the goals/parameters are not well defined in my mind.
I understand you OGITC. I'm looking at more capacity in battery bank so on good days the bank is not drawn low like you said 80% and in bad times I will still have some energy in the bank to cash out. If I could get 3 days I think I would be okay. I have already put normally closed relays in a few house circuits, (Refrigerator and a pump). For months now starting at 4:00pm my refrigerator is off 3 hours and on 1 hour not to be on full time till the sun comes up at 8:00am I have not heard from the wife that food is spoiling so I may stretch that to 4 hours off. The pump is for the "Grey water" system I have collecting bath water and watering the lawn. If my batteries are low I can cut that off altogether. Lights are all LED and use practically no power. I have APC 1400 UPS inverter and 1.5kWh battery dedicated to lights that never charge from mains. I could steal from it if needed. All this managing where power goes during the winter is for one thing.... The Blower Motor on the furnace.
 

J_Mack58

Member
Joined
Apr 7, 2021
Messages
109
that is the biggest problem with solar. to survive the winter you need about tripple the input for the cloudy days. in my latest design (on paper) I have a expected drain of 15kwh per day, To supply that I want 100KwH of storage, 20Kw of Solar and possibly Wind supplement and if possible offset some of the Solar with Hydro if I get a constant water source.
I will always be expanding my battery bank 100kWh will be my goal too. I have no chance on Hydro but I'm trying to make the wind thing a possibility.
 

Oberfail

Member
Joined
Jun 22, 2021
Messages
160
I will always be expanding my battery bank 100kWh will be my goal too. I have no chance on Hydro but I'm trying to make the wind thing a possibility.
Keep us updated, i'm also planning on adding wind power in 2 years or so for the winter months.
 

J_Mack58

Member
Joined
Apr 7, 2021
Messages
109
You are still lucky. My PV here in Germany achieves about 3...10 % of its nominal power at the best time of the day in November / December.
In some areas you cant solely rely on PV as your only power source - it simply doesn't make sense. You would have to massively oversize the system and in summer you dont know what to do with all the energy. You have to have a mix of sources, hard if you want to live 100% offgrid in some places.
I agree the system has to be over sized and I guess I have to do it. I have two systems one grid tied one not. I do this in case the grid go away I can still have power. I have grid when I don't have solar but that defeats the battle to be energy independent. This whole thread made me think.... make it big, make it oversized. Let that extra in the summer get sold back to the utility company on the grid. In the winter I need it all for myself.
 

J_Mack58

Member
Joined
Apr 7, 2021
Messages
109
Well that's the problem when living around the 45th parallel or higher. In the summer we get 15+ hrs of solar and in the winter well not much till the reversal on Dec 21. What to do. The only redeeming factor is when you get those crisp clear days and the panels are cold the production is pretty good although for a short period of time. Other than having a system to track the sun, have the panels attitude virtually vertical with a clear southern exposure (not always possible) there is not much we can do, till the azimuth of the sun favors our latitude again. The only redeeming factor is the amount of energy that we can produce during the "good" times sets off the cost of the "bad" times. I am considering a small wind turbine just for kicks and maybe 500W to 1000W of power when the wind blows. Also probably more hassle than its worth but you never know.
Wolf
I had to check that 45th Parallel wolf. And if all goes well next week I will be a land owner in New Mexico. The state I'm planning on retiring in. Then this battle/hobby to be 100% energy independent starts all over again.
 

Dr. Dickie

Member
Joined
Sep 23, 2020
Messages
286
I had to check that 45th Parallel wolf. And if all goes well next week I will be a land owner in New Mexico. The state I'm planning on retiring in. Then this battle/hobby to be 100% energy independent starts all over again.
Yeah, I saw that and though, I don't live in Korea?
 

J_Mack58

Member
Joined
Apr 7, 2021
Messages
109
LOL changes in latitude changes in attitude...............
Nice definitely better for solar.
So are you going to follow Mike Reynolds the designer of "earthship" passive solar houses?

Wolf
Just checked Mike Reynolds out. I will steal some of his concepts but I think my wife wants a conventional house and you know the saying, "Happy wife, happy life".
 

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