Using excess solar to heat house

[shavermcspud]

Around that time of the year, the sun is really bright and the sky is very clear and clean, and it seems that with the coldest days the rays are strong, please note I said it starts mid January to have better solar charging. So it climbs up eventually more and more every day when it's sunny,of course.

I've got a few pictures that shows that 15, and 16 days from today (so on February 12-13) I made 43 kw, and 42.5kw in those two days. A lot of days of 20-30 kw. Middle picture shows 10.4kw at 156 VDC max pv day 10, so yes it's doing better than in the summer months with all the haze in the air.

If you have enough panels and sun, power is there to be used, unless you can sell back to the utilities company. Not my case. Hope this clarifies any doubts, and I'm happy to share. Thanks

Edit: controllers are stacked, so CO1 AND CO2 HAVE TO BE ADDED on pictures taken, magnum data don't go over 25 kwh for each controller. PT-100

Confused, your 3rd screen shot shows 110.4kW for day 10, not 10.4kW as you have stated, how is that even possible on a 10kW array in Ontario with 7 hours max sunlight for that day? even at full tilt that could theoretically be maximum 70Kwh or am i missing something here?

 

[shavermcspud]

If op is already producing excess. I don't understand why so many people want to say that he can't.

Re-read the original post, it hasn't been installed yet, its due later this month. Reality vs expectations can be huge, I'm in the same country as the OP and I know first hand.

 

[timselectric]

Re-read the original post, it hasn't been installed yet, its due later this month. Reality vs expectations can be huge, I'm in the same country as the OP and I know first hand.

My mistake.
This has been going on for so long, I guess I forgot where we started. lol

 

[shavermcspud]

My mistake.
This has been going on for so long, I guess I forgot where we started. lol

I know what you're saying

 

[Swing]

@shavermcspud and

A problem specific to the OP is the location, Scotland, where the average winter sun output is only 10% of the summer.
Even 10% would be useful for lights and other small loads but not for heating.

Why continuing with this black and white discussion about summer versus winter? It is not helping to answer the OP.

I have a 5kWp system with 10kWh, grid connected. And they are only at 8 degrees tilt, so pretty much flat.

Yes, the month of the shortest daylight, solar production is a fraction of high summer output. However, it doesn't matter. There are still enough months that there is excess energy while heating a room is still required. That is very clear, and I am withnessing this, for example past week most of the days were like that.

And I am already running an AC system, so I am already using solar energy to heat my house. I didn't do that in December, because yes there wasn't enough solar. But I am doing that end of February, and probably will for a few months. So those months might not be self supporting, but solar power is used to heat my house nonetheless.

Edit: and on top of that, there are sometimes and will be a lot of occurences where I run the AC for heating on battery power from yesterdays solar.
During the day the heating might not be necessary anymore (because of sun and higher temperatures).

 

[Denis]

Confused, your 3rd screen shot shows 110.4kW for day 10, not 10.4kW as you have stated, how is that even possible on a 10kW array in Ontario with 7 hours max sunlight for that day? even at full tilt that could theoretically be maximum 70Kwh or am i missing something here?

Please don't be confused, I said it was 10.4kw on that one moment in time, but I know it fluctuate, I was just showing that it can be achieved in February. No mention of 70kwh.???
Magnum displays it like that, if it's 9.9kw there's no 1 in the front, but if it goes over thats how it shows.
The on time is 10.1 hours right now.
Thanks for your interest.

 

[Swing]

Basically, an important design choice (or in fact realization) is to decide if you are going to electrify everything, including heating and driving your car.
If you do that, you could complain that there is a point that you don't produce enough solar anymore, whereas you could be "offgrid" without this further electrification. But in fact, you are just using more of your own solar energy than before, and have further reduced your dependency on fossil fuel / gas. And probably bringing the cost down as well, depending on where you live.
Especially true for grid-connected locations. For pure off-grid you still need a backup.

 

[shavermcspud]

Basically, an important design choice (or in fact realization) is to decide if you are going to electrify everything, including heating and driving your car.
If you do that, you could complain that there is a point that you don't produce enough solar anymore, whereas you could be "offgrid" without this further electrification. But in fact, you are just using more of your own solar energy than before, and have further reduced your dependency on fossil fuel / gas. And probably bringing the cost down as well, depending on where you live.
Especially true for grid-connected locations. For pure off-grid you still need a backup.

I honestly wish the OP the best of luck with his plans but speaking from experience and others around me in the UK who I know well and do live practically off grid, this just isn't feasible especially in the northern hemisphere of the UK region, trying to run an electric inline 12kWh water heater from 5kWp of PV and a 7kWh battery for central heating purposes in the colder months, whilst also trying to charge a 7.2kW battery pack and run the base load of a house. Simple math dictates that in the winter ( at a stretch you could say from October to March) in the UK you need heating the most. Example....Two hours of heating, that's 24Kwh used, that's your battery empty after 40 minutes if already charged , and you have also exceeded your PV capacity (during the daylight) already and you're back to grid draw to supplement, you might as well have saved the £900 + fitting, plus rewire costs to support a 12kW load and just used the gas boiler you already have in place, Yep its not as green or environmentally friendly, but neither is chucking a load of money at somthing which you wont be able to run off grid ever with your current planned PV system?

 

[robby]

I honestly wish the OP the best of luck with his plans but speaking from experience and others around me in the UK who I know well and do live practically off grid, this just isn't feasible especially in the northern hemisphere of the UK region, trying to run an electric inline 12kWh water heater from 5kWp of PV and a 7kWh battery for central heating purposes in the colder months, whilst also trying to charge a 7.2kW battery pack and run the base load of a house. Simple math dictates that in the winter ( at a stretch you could say from October to March) in the UK you need heating the most. Example....Two hours of heating, that's 24Kwh used, that's your battery empty after 40 minutes if already charged , and you have also exceeded your PV capacity (during the daylight) already and you're back to grid draw to supplement, you might as well have saved the £900 + fitting, plus rewire costs to support a 12kW load and just used the gas boiler you already have in place, Yep its not as green or environmentally friendly, but neither is chucking a load of money at somthing which you wont be able to run off grid ever with your current planned PV system?

I am so glad that I listened to a number of posts like yours when I was planning my system or I would have been horribly disappointed. After learning a lot of stuff I calculated that I could cut off 50% of my Utility bill with the system I was going to buy and made sure that I could get 100% free of the Grid if I added more batteries. We got almost exactly a 50% reduction and with some fine tuning of the system and changing our laundry times I got it up to 60%. I added another battery and we are now up to 75% reduction in the winter months with no real life style changes. I am really looking forward to seeing how it will perform in the summer.

 

[Swing]

I honestly wish the OP the best of luck with his plans but speaking from experience and others around me in the UK who I know well and do live practically off grid, this just isn't feasible especially in the northern hemisphere of the UK region, trying to run an electric inline 12kWh water heater from 5kWp of PV and a 7kWh battery for central heating purposes in the colder months, whilst also trying to charge a 7.2kW battery pack and run the base load of a house. Simple math dictates that in the winter ( at a stretch you could say from October to March) in the UK you need heating the most. Example....Two hours of heating, that's 24Kwh used, that's your battery empty after 40 minutes if already charged , and you have also exceeded your PV capacity (during the daylight) already and you're back to grid draw to supplement, you might as well have saved the £900 + fitting, plus rewire costs to support a 12kW load and just used the gas boiler you already have in place, Yep its not as green or environmentally friendly, but neither is chucking a load of money at somthing which you wont be able to run off grid ever with your current planned PV system?

So nothing is ever possible? The sun never shines when you need heat?

Of course, taking an electric 14kW heater on a 5kWp and 7kWh storage system isn't the best option, and it is going to empty the batteries fast.
But, this is a forum, and we can discuss what is a good option.

There will be lots of days he can use excess solar energy for heating. Preferably through a heat pump system.

So yes, it is an option to use solar energy for heating, I am already doing that. There is no use in shutting down the discussion when people are certainly using solar energy to heat their house. You can keep repeating that it will not work on the shortest day of the year, but that is not the point.

Today is another sunny day where my batteries will be charged and my house will be heated by the sun. And the AC system only cost me 1500 euro.

For people living in Europe and UK, a heat pump system makes sense for more reasons then only using more of your solar setup.

 

[robby]

I guess why so many of these post go sideways is because of differences of interpretation of what is said. You have a lot of engineers on here and when we hear statements like: “ could significantly reduce gas or oil use for central heating.” Our minds interpret the word “significantly” a lot differently than you might.

 

[Swing]

I guess why so many of these post go sideways is because of differences of interpretation of what is said. You have a lot of engineers on here and when we hear statements like: “ could significantly reduce gas or oil use for central heating.” Our minds interpret the word “significantly” a lot differently than you might.

Well you can discuss it and discuss if it is cost effective or not. Or you can shut the whole thing down by saying it isn't possible and no further discussion.
Which is completely ridiculous since people are doing it already.

For us, we are a family with a grid connected home. We are basically looking at a shortage of 1000kWh in the winter.
But that means is the rest of the time we can rely on our own solar (and we are exporting much more into the grid)
And 1000kWh isn't very much considering we do everything electrically, heating and hot water as well.

Coming from October into November, it was pretty dramatic, directly needing the grid to heat the house because it become cold and dark for a longer time. But now in Spring season, it is very different. Sun is higher, heating has already run directly on solar power quite some days and this is just the start.
As I am writing this, solar is taking over the heating power load in my house this morning.

 

[Ralphloren]

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[Aussie_Pete]

I honestly wish the OP the best of luck with his plans but speaking from experience and others around me in the UK who I know well and do live practically off grid, this just isn't feasible especially in the northern hemisphere of the UK region, trying to run an electric inline 12kWh water heater from 5kWp of PV and a 7kWh battery for central heating purposes in the colder months, whilst also trying to charge a 7.2kW battery pack and run the base load of a house. Simple math dictates that in the winter ( at a stretch you could say from October to March) in the UK you need heating the most. Example....Two hours of heating, that's 24Kwh used, that's your battery empty after 40 minutes if already charged , and you have also exceeded your PV capacity (during the daylight) already and you're back to grid draw to supplement, you might as well have saved the £900 + fitting, plus rewire costs to support a 12kW load and just used the gas boiler you already have in place, Yep its not as green or environmentally friendly, but neither is chucking a load of money at somthing which you wont be able to run off grid ever with your current planned PV system?

I didn’t say I was going for a 12kwh water heater (even I know that’s not going to work), it was primarily about an electric flow heater, which can be as low as 2kwh. That said I take your point and will see how I get on, if indeed I do anything at all

 

[copec]

You should check out https://sahp.info/ they are a UK company. I've had my eye on getting one here from https://www.neshw.com/residential/sahp/ or https://www.theradiantstoreinc.com/solar-assisted-heat-pumps to run only with excess PV (which is ~330 days a year) to heat a thermal storage tank.

 

[Sky Noris]

Defiantly not efficient or probably even a good use of my extra power. But I installed a electric fireplace to help burn off excess production when cold. However it does help with my sanity and mental state ?. In the summer I run several air conditioners.

 

[hclarkx]

Mini-splits are a very efficient way to heat and cool a space.

Indeed. My son has 2 kW of solar on his old motor home, along with a 9,000 BTU-hr mini split (EER=16.5). On sunny days his batteries are usually topped off early enough to get a few hours of heating in before the sun is down. This is in fall and spring on the CA west coast. If the forecast is for sun, he will also run the mini split for night heat (set at 50-55F).

 

[Ralphloren]

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[copec]

Defiantly not efficient or probably even a good use of my extra power. But I installed a electric fireplace to help burn off excess production when cold. However it does help with my sanity and mental state ?. In the summer I run several air conditioners.

I did the same thing with resistance heaters and window AC units until I got a mini-split - now I run that in heating/cooling to assist the central system. Everything in my house runs off-grid except the electric clothes drier and the outdoor central AC compressor. During the summer I'll always have a "cold room" if the main power goes out.

 

[Sky Noris]

Speaking of burning off extra power, I find this shop heater really handy to do that because you can select 3kw, 4kw, or 5kw depending on how much you need to burn in the winter time! Works great.

https://www.amazon.com/Comfort-Zone-Industrial-Electric-Ceiling/dp/B009F1SWH8/ref=sr_1_1?crid=1PQ59L4LNNEFE&keywords=240v+shop+heater+5kw&qid=1646260053&sprefix=240v+shop+heater+5k%2Caps%2C1114&sr=8-1

Nice I could see myself throwing something like this in my garage at some point. I've got a wifi controlled 1.5 KW heater in my shed to keep my batteries warm and love it.