Do you have enough solar to go off grid in winter?

[CrazyRabbit]

Nice job! How hard was it to cut down to the old diodes? What potting compound did you use?

All the best,

BG

RTV11-1P bought at digi-key
Momentive performance materials
Waterford ny
Material 127812

Easy enough to dig out, hard to unsolder. Need big iron. Panels are easy to test, short circuit current and open circuit voltage. For short circuit test you need a dc clamp meter and plug the leads into each other.

 

[dhrivnak]

That is hard to do in NE Tennessee. I will typically pile up some 1800kWh in the spring and fall in my net metering account to get me through the winter slump. That is about 138 PowerWalls needed for our 9.5kW of solar. We have an all electric home with HP heating and cooling and a HP water heater. To be fully off grid in the winter I would need to double my solar and add more than my 27 kWh of storage. But could I get by, sure. I am sure we can stay far more comfortable than the Ukrainians this winter if the gird were not present.

 

[charlesj]

That is hard to do in NE Tennessee. I will typically pile up some 1800kWh in the spring and fall in my net metering account to get me through the winter slump. That is about 138 PowerWalls needed for our 9.5kW of solar. We have an all electric home with HP heating and cooling and a HP water heater. To be fully off grid in the winter I would need to double my solar and add more than my 27 kWh of storage. But could I get by, sure. I am sure we can stay far more comfortable than the Ukrainians this winter if the gird were not present.

Start saving and planning.

 

[DrGriz]

I would love to go completely off grid, but after 4 winters, I can honestly say I would need at least 2 MWh of storage to get through.
I produce enough energy to more than meet my needs with the system I have. More solar panels would not help, because on those days when we don't produce (snow=0 kWh) 0 x whatever is still 0.

I keep hoping one of these falls off the truck when it passes my house (j/k).

 

[charlesj]

I would love to go completely off grid, but after 4 winters, I can honestly say I would need at least 2 MWh of storage to get through.
I produce enough energy to more than meet my needs with the system I have. More solar panels would not help, because on those days when we don't produce (snow=0 kWh) 0 x whatever is still 0.

I keep hoping one of these falls off the truck when it passes my house (j/k).

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View attachment 873948

I want one as well but not sure where to put it.

Oh, wait, the price. Sell everything but then no need for it.

 

[skepticcyclist]

I would love to go completely off grid, but after 4 winters, I can honestly say I would need at least 2 MWh of storage to get through.
I produce enough energy to more than meet my needs with the system I have. More solar panels would not help, because on those days when we don't produce (snow=0 kWh) 0 x whatever is still 0.

I keep hoping one of these falls off the truck when it passes my house (j/k).

View attachment 873932
View attachment 873948

You’re also pretty for north. For those of us in the southern half of the country, such as myself in SoCal, we could easily get through the winter.

 

[DrGriz]

You’re also pretty for north. For those of us in the southern half of the country, such as myself in SoCal, we could easily get through the winter.

Yep. Always wanted to figure out a way, however.

 

[mswlogo]

6 kW system. On sunny winter days we produce 20 to 25 kWh and use 25 kWh with the pool running. We turn off the pool pump we only use about 10-15 kWh for the house.

ETA: Here is our January (the lowest production month) usage and production with the pool running

Get a new variable speed pool pump (Pentair). When I got Solar I became more power usage sensitive. The trick to saving with variable speed pool pump is 1/2 the RPM takes 1/4 the power. So my pool pump now runs 24/7 but it only pulls 80 watts. Which is ~2 KWh a day. That is still fast enough to filter the full volume of the pool twice a day (23k gallon pool).

This power saving is the principle behind lots of new DC motor based systems like new refrigerators (variable speed DC compressors that run constant). Or HVAC heat pump systems too. They run at lower output for longer periods.

 

[zƬesla]

@DrGriz: time to add wind

 

[jboy210]

No way we can go off grid completely from Nov to Feb. Sun is too low, and we have too much shading from trees. Daily solar production or our 12.75 kW roof is down to 10 kWh/day or less.

Fortunately, solar production annually is good enough to cover the power cost and leave us with a few extra credits at the end of the billing year.

 

[skepticcyclist]

Get a new variable speed pool pump (Pentair). When I got Solar I became more power usage sensitive. The trick to saving with variable speed pool pump is 1/2 the RPM takes 1/4 the power. So my pool pump now runs 24/7 but it only pulls 80 watts. Which is ~2 KWh a day. That is still fast enough to filter the full volume of the pool twice a day (23k gallon pool).

This power saving is the principle behind lots of new DC motor based systems like new refrigerators (variable speed DC compressors that run constant). Or HVAC heat pump systems too. They run at lower output for longer periods.

I do have a Pentair variable speed pool pump. It needs to run at a certain RPM for the vacuum to work. I don't need to turn it down. I just need to run it fewer hours. I now run it only 2 hours a day in the winter, which is plenty enough to keep it clean and clear

 

[h2ofun]

I do have a Pentair variable speed pool pump. It needs to run at a certain RPM for the vacuum to work. I don't need to turn it down. I just need to run it fewer hours. I now run it only 2 hours a day in the winter, which is plenty enough to keep it clean and clear

I use a 2 speed pump for my spa. low speed when not using, high speed when in spa. Can these do "high" speed?

 

[mswlogo]

I do have a Pentair variable speed pool pump. It needs to run at a certain RPM for the vacuum to work. I don't need to turn it down. I just need to run it fewer hours. I now run it only 2 hours a day in the winter, which is plenty enough to keep it clean and clear

You stated 10-15 KWh a day which is awful lot. Does it need to vacuum that often? I do mine with a drop in vacc once a week tops.

 

[DrGriz]

@DrGriz: time to add wind

Believe me, I asked around about that! Trouble is that wind here is not consistent enough.

I do have solar water heater plans. We actually have enough power to cover hot water, but hot water is about the same kWh use as local driving, so it is significant. Hot water can be as much as 50% of our use on any given day, depending on heating, cooling, etc.

Solar water heaters work even if it is cloudy. And I have a perfect place to mount the panels (which can be mounted vertically like on the side of the house). I can probably make much more than our current needs. So should figure out a way to make that extra hot water useful...

 

[skepticcyclist]

You stated 10-15 KWh a day which is awful lot. Does it need to vacuum that often? I do mine with a drop in vacc once a week tops.

We have since turned it down to 2 hours a day.

The vacuum is left in every day. It is attached to an outflow valve. It is an autovacuum. The only way to keep it vaccuumed enough and keep the energy use down is run it as I do in the winter.

 

[nwdiver]

Believe me, I asked around about that! Trouble is that wind here is not consistent enough.

I do have solar water heater plans. We actually have enough power to cover hot water, but hot water is about the same kWh use as local driving, so it is significant. Hot water can be as much as 50% of our use on any given day, depending on heating, cooling, etc.

Solar water heaters work even if it is cloudy. And I have a perfect place to mount the panels (which can be mounted vertically like on the side of the house). I can probably make much more than our current needs. So should figure out a way to make that extra hot water useful...

Have you looked into heat pump water heater? SANDEN makes one that can pull heat out of air that's -20F.

SANCO2™ High-Efficiency Heat Pump Water Heater​

 

[BGbreeder]

Believe me, I asked around about that! Trouble is that wind here is not consistent enough.

I do have solar water heater plans. We actually have enough power to cover hot water, but hot water is about the same kWh use as local driving, so it is significant. Hot water can be as much as 50% of our use on any given day, depending on heating, cooling, etc.

Solar water heaters work even if it is cloudy. And I have a perfect place to mount the panels (which can be mounted vertically like on the side of the house). I can probably make much more than our current needs. So should figure out a way to make that extra hot water useful...

Have you looked into heat pump water heater? SANDEN makes one that can pull heat out of air that's -20F.

SANCO2™ High-Efficiency Heat Pump Water Heater​

@DrGriz You might want to look into more solar PV panels that you then use for heating water, preferably with a heat pump water heater. It gives more flexibility than a dedicated solar heater, typically for less investment.

There are also a outdoor wood fired boilers...

All the best,

BG

 

[DrGriz]

Have you looked into heat pump water heater? SANDEN makes one that can pull heat out of air that's -20F.

SANCO2™ High-Efficiency Heat Pump Water Heater​

I had not and thank you for the link!

So, thinking about it:

Assuming the quoted 5x reduction in energy use, we would save 2320 kWh/year, Our current hot water needs are ~2900 kWh/year of a total of ~13350 kWh/year. So that would be a 17% reduction in terms of kWh.

Of course, on a daily basis, the energy savings are less when the temperatures are colder (like in December) in a heat pump system. So it might not work it's best and most efficient when we need the savings the most, as far as keeping us off-grid. In other words, and I don't really know the number, when it is 0-20 degrees out like it has been recently, the cost to heat water in kWh might be reduced little or not at all.

I am familiar with heat pump systems because we added a mini-split heat pump system to replace baseboard heat a few years ago. The SANCO2 uses carbon dioxide vs the ethylene glycol in our minisplits but the principles are the same. The minisplits struggle to produce heat when it's that cold. It's still much better than the baseboards, of course.

So, I will continue to mull it over. Thanks again for the link!

 

[DrGriz]

@DrGriz You might want to look into more solar PV panels that you then use for heating water, preferably with a heat pump water heater. It gives more flexibility than a dedicated solar heater, typically for less investment.

There are also a outdoor wood fired boilers...

All the best,

BG

Thank you for the suggestions!

The trouble with more solar panels is that solar panels don't work when they are covered with snow. Or even when they aren't but there's heavy cloud cover. Our minimum production on a clear day in late December is 30 kWh, which is adequate to be off grid. But it snows, so that doesn't happen very often. More panels covered with snow doesn't help us.

I will have to look into wood fired boilers. We already have a wood stove which is efficient and provides a lot of our heat.

Thanks again!

 

[nwdiver]

The trouble with more solar panels is that solar panels don't work when they are covered with snow.

What angle are those panels at? I'm helping @outdoors with an off-grid solar project up north also. We chose a pitch of ~40 degrees for the solar array. Hoping that's a sufficient angle that the snow slides off quickly. Another idea is to basically make a solar 'fence' with the panels at a ~90 degree angle so the snow won't stick at all. Not very useful in the summer but will help a lot in the winter.

Building an off grid Solar Powered (EV charging) Campground​