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OffGridInTheCity

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To recap - I have a continued interest in powering my overall home to a livable degree. Last year, the 12.85kw PV array produced 15,000 kwh of useable power. The main problem is *winter*! Nov/Dec/Jan (you can see in previous post) is at 500kwh for the month - just too low to have any chance to 'power the house'. I keep niggling in my mind how to produce 500kwh extra / month for those 3 months so I could have at least 1,000kwh/month to work with.

Producing power is a 'big deal' if you go generator... wood, gasoline, propane, all require a lot of work. And when you think long term (5, 10, 15yrs) its gets daunting. I recently found numbers for Propane in this article - https://preparednessadvice.com/propane-powered-generators-best-choice/ Specifically, this section:

How much propane will my generator burn per hour?
    • It requires 2 horsepower to produce 1000 watts of energy per hour under load
    • Under load each horsepower consumes 10000 BTU per hour
    • Propane contains 92,000 BTU per gallon
    • Propane weights 4.2 pounds per gallon
Using these factors how long can a 5000-watt generator run on a 500 gallon propane tank at 50 capacity.
    • 10 horse power at 50% would use 5 HP to generate 2500 watts of electricity
    • 5HP X 10,000 BTU would consume 50,000 BTU per hour
    • 500 gallons X 92,000 = 46,000,000 BTU of energy in a full 500 gallon tank
    • 46,000,000 BTU divided by 50,000 BTU = 920
    • A 500-gallon tank that is full would run a 500-watt generator at ½ capacity for 920 hours.

Doing the math I get 4.6kwh / gallon of propane. To do 1,500 kwhs for Nov/Dec/Jan I'd need 326gallons of proane! just for 1 year, not to mention burning up a generator. Agh - it seems like its so much fuel to produce electricity. And the $... a tank is at least $1000, and the fuel is 326gal * $3.00'ish is at least a $1000 and the generator. So $3000 just to think about it and for only 1 year.

SO I'm back to a stock of emergency solar panels to store under the house and to deploy them in the yard if an emergency/winter. I found 40 x 285w 9yr old SunTechs for $73 each. This should produce close to the extra 500kwh/month in winter I'm looking for. I'll let you know how they measure up when I get / test them.

I'm going to test each one against an unused 3yr-old SolarWorld 285w panel to verify they have 80%+ power generation left.

You can look at it either way - 1) its annoying that 'fuel' (like propane)/generator is so costly to create kwh or 2) that panels do such a great job in terms of quiet, no maint, etc.

I think for me, panels are how I'm going to fill that 'itch' in my head for a whole house backup generator :)
 
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texfixdfw

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Feb 9, 2021
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i admire anyone who attempts to go off grid. its rewarding if you can get past the hurdles involved. remodeling a city house is cost prohibitive for most so your creativity is crucial. staying in your tow-along during coldest days will put hair on any chest. respect for your commitment!
Any possibility of mounting beer can/ solar pool heater style furnace on south side of house to supplement daytime heating? im building ground up so im able to use geothermal, thermal mass walls, rocket mass heating, radiant floor, etc. ive built a soda can furnace to heat a medium sized room during the day. a standard city dwelling needs a retrofitted thermal mass to be effective. id consider insulating a small closet or room and stacking rain barrels or even cinder blocks filled with dirt packed into the openings. run a hot air/water/ glycol coil through it during day to store heat and vent it out at night. it will take a few sunny days to warm it up to be usable. the more dense the longer to charge it up. if this works, you can do a more permanent solution. check with local engineer for permanent solution. idk the effects of massive weight on foundations. for a more elaborate solution you can use geothermal to cool during summer. its worth a shot for low cost experiment. i can send you a sketchup file of the idea if you have any interest.
 

OffGridInTheCity

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i admire anyone who attempts to go off grid. its rewarding if you can get past the hurdles involved. remodeling a city house is cost prohibitive for most so your creativity is crucial. staying in your tow-along during coldest days will put hair on any chest. respect for your commitment!
Any possibility of mounting beer can/ solar pool heater style furnace on south side of house to supplement daytime heating? im building ground up so im able to use geothermal, thermal mass walls, rocket mass heating, radiant floor, etc. ive built a soda can furnace to heat a medium sized room during the day. a standard city dwelling needs a retrofitted thermal mass to be effective. id consider insulating a small closet or room and stacking rain barrels or even cinder blocks filled with dirt packed into the openings. run a hot air/water/ glycol coil through it during day to store heat and vent it out at night. it will take a few sunny days to warm it up to be usable. the more dense the longer to charge it up. if this works, you can do a more permanent solution. check with local engineer for permanent solution. idk the effects of massive weight on foundations. for a more elaborate solution you can use geothermal to cool during summer. its worth a shot for low cost experiment. i can send you a sketchup file of the idea if you have any interest.
Appreciate the suggestions and yes, I noodle on these things - including wood based Stirling engine/generator, and outdoor boilers. Soda can 'panels' are still panels... and I'd personally love to add more panels (soda can, water circulation, solar) but its a matter of being smack in the middle of a neighborhood that objects to 'highly visible' things and I've already taken up what space I can with 45 panels.

I also don't have any wind. That's another thing - it takes a LOT of physical force (engine, wind) to produce even modest power.

I have a rainharvest system - with 7,500 gallons of water in 3 x 2,500gal tanks that range from 90F/32C summer and 45F/7C winder. I wonder if I could do some level of heat pump using this water store... but I suspect its not suited (as it is) for enough heat transfer to be meaningful and then we're back to radiator/panels again. Also this would have to be DIY as the city would never approve of non-standard HVAC... heck they won't even allow mini-splits as its against code.

One time I even calculated storing power in lifting these 2,500gal tanks up 6 ft and then let them lower to generate electricity and the numbers are dismal - like 1000w of storage. A flywheel sounds so cool but for meaningful power storage its dangerous because of rotational speeds needed.

Generating energy and energy storage are indeed challenging in a neighborhood setting for sure. :)
 
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texfixdfw

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Appreciate the suggestions and yes, I noodle on these things - including wood based Stirling engine/generator, outdoor boiler. Soda can 'panels' are still panels... and I'd personally love to add more panels (soda can, water circulation) but its a matter of being smack in the middle of a neighborhood that would object to 'highly visible' things and I've already taken up what space I can with 45 panels.

I do have a rainharvest system - with 7,500 gallons of water in 3 x 2,500gal tanks that range from 90F/32C summer and 45F/7C winder. I wonder if I could do some level of heat pump using this water store... but I suspect its not suited for heat transfer and then we're back to radiator/panels again.
 

texfixdfw

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Feb 9, 2021
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that may be an option. super insulate the water containers if above ground or bury them if possible and insulate. you could solar heat the water storage and circulate it through a small room. not sure how effective it would be for a large room. would work well for your camper. whichever way you go, the most efficient way is to store it in a "battery" for night time use. ill be posting my results of storing heat in ibc totes in my greenhouse in a few weeks. im in texas so i dont have nearly the challenge of heating that you do. my greenhouse is 350sf, insulated north wall, south facing, rammed earth west wall, with around 800 gallons of water stored inside. ill be staying in this for a few months while finishing the house. youre not alone in the struggle!
 

OffGridInTheCity

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Have you looked into evacuated tube solar water heaters? I hear they work much better in the winter than other solar systems. Doesn't generate electricity though, and competes with PV for space.
Thanks for the thought. I looked at them (and general water based panels) early on but went PV in the place that I put them. I built some DIY copper pipe (with T-s) and used glass in 4 x 8 boxes some number of years ago and it was always a battle of leaks. This and other plumbing experiences lead me to strongly prefer wire to pipes :)
 

texfixdfw

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do you have a fireplace? if so you could build in a rocket heater to burn super hot with much higher efficiency. store the heat somehow without burning a ton of wood.

 

OffGridInTheCity

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do you have a fireplace? if so you could build in a rocket heater to burn super hot with much higher efficiency. store the heat somehow without burning a ton of wood.
We live in Southern OR which is smack in the middle of 100s of miles of trees - e.g. much wood... and they are popular so we had a couple of vendors out. Unfortunately a fireplace cannot reasonably be installed in our house. The contractors we invited to bid just shook their heads and mumbled - don't do it as to be 'up to code' we'd have to rebuild the roof, rebuild the wall where the fireplace would replace a gas/fake fireplace... we're talking $15-20k.
 

floydR

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If the gas fireplace has a flue of 3-4 inches you might be able to have a pellet stove. A multi fuel pellet stove can burn corn, fruit pits, plus the standard pellet fuels.

Later floyd
 

OffGridInTheCity

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If the gas fireplace has a flue of 3-4 inches you might be able to have a pellet stove. A multi fuel pellet stove can burn corn, fruit pits, plus the standard pellet fuels.

Later floyd
Unfortunately no - according to the wood stove (including pellet stoves) contractors. In addition, this entire 45deg wall (floor to ceiling) would have to come out at least 2-3feet (for code clearances against the back wall) and then it would cover the window on the left and woodwork on the right. Behind this wall is a 10ft deck - so the roof extends 10ft beyond the window which means a 90deg elbow thru the wall is not OK. The chimney/piping has to be redone and perhaps even stick up beyond the chimney façade on the outside.

There isn't any other location available due to windows and walls. Its doable but not at a reasonable price. I think a water boiler in the yard ($6000) with piping / heat exchanger ($3000?) in place of the gas fireplace would cost way less. :)

Here's a pic of the fireplace and existing chimney from google earth - you can see the chimney façade 10ft in from the edge of the roof - the fireplace is right under it.

1612985916721.png
1612986408913.png


I'm just grateful I have room for 45 panels... that don't intrude on neighbor's views / not in anyone's 'face' with the panels. I'm amazed at how many people really hate to see panels - maybe as much as 40%. .
1612986848821.png
 
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OffGridInTheCity

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Messages
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My deficit is Nov, Dec, Jan, Feb - where my power production falls to 500kwh/month. I need 1000kwh/month to have a chance at keeping the house habitable! So I need 2000 extra kwh during winter.

If my match is correct, it would take aprox 400gallons of propane to produce 2000kwh of power + burn up a X thousand $ generator + noise. I live in a heavily forested area with wood available - but its a lot of work and would need several cords of storage no matter if it was boiler, steam, gasifier, or stirling.

So panels it is - will just store them under the house and they will be my 'backup generator' for 'the big one'!. I just got in 40 x 285w used Suntech panels. They are 9 years, $56/panel (from ebay) and appear in good shape. I'm hoping for 90% power levels which would get me close to that 500kwh/month in winter.
1614358038385.png

I'll measure them against a know good panel and see how they actually stack up. They are longer and heavier than I was expecting - interesting.
1614358376608.png
 

dali1972

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Sep 11, 2020
Messages
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To recap - I have a continued interest in powering my overall home to a livable degree. Last year, the 12.85kw PV array produced 15,000 kwh of useable power. The main problem is *winter*! Nov/Dec/Jan (you can see in previous post) is at 500kwh for the month - just too low to have any chance to 'power the house'. I keep niggling in my mind how to produce 500kwh extra / month for those 3 months so I could have at least 1,000kwh/month to work with.

Producing power is a 'big deal' if you go generator... wood, gasoline, propane, all require a lot of work. And when you think long term (5, 10, 15yrs) its gets daunting. I recently found numbers for Propane in this article - https://preparednessadvice.com/propane-powered-generators-best-choice/ Specifically, this section:

How much propane will my generator burn per hour?
    • It requires 2 horsepower to produce 1000 watts of energy per hour under load
    • Under load each horsepower consumes 10000 BTU per hour
    • Propane contains 92,000 BTU per gallon
    • Propane weights 4.2 pounds per gallon
Using these factors how long can a 5000-watt generator run on a 500 gallon propane tank at 50 capacity.
    • 10 horse power at 50% would use 5 HP to generate 2500 watts of electricity
    • 5HP X 10,000 BTU would consume 50,000 BTU per hour
    • 500 gallons X 92,000 = 46,000,000 BTU of energy in a full 500 gallon tank
    • 46,000,000 BTU divided by 50,000 BTU = 920
    • A 500-gallon tank that is full would run a 500-watt generator at ½ capacity for 920 hours.

Doing the math I get 4.6kwh / gallon of propane. To do 1,500 kwhs for Nov/Dec/Jan I'd need 326gallons of proane! just for 1 year, not to mention burning up a generator. Agh - it seems like its so much fuel to produce electricity. And the $... a tank is at least $1000, and the fuel is 326gal * $3.00'ish is at least a $1000 and the generator. So $3000 just to think about it and for only 1 year.

SO I'm back to a stock of emergency solar panels to store under the house and to deploy them in the yard if an emergency/winter. I found 40 x 285w 9yr old SunTechs for $73 each. This should produce close to the extra 500kwh/month in winter I'm looking for. I'll let you know how they measure up when I get / test them.

I'm going to test each one against an unused 3yr-old SolarWorld 285w panel to verify they have 80%+ power generation left.

You can look at it either way - 1) its annoying that 'fuel' (like propane)/generator is so costly to create kwh or 2) that panels do such a great job in terms of quiet, no maint, etc.

I think for me, panels are how I'm going to fill that 'itch' in my head for a whole house backup generator :)
The main problem is *winter*! Nov/Dec/Jan

Its really interesting project this one...Im gutted that ive missed the worst months for mine...strange saying that but i really wanted to see the output during the winter ...i know im gonna be OK in the summer.

Im also looking at heat pumps...
 

OffGridInTheCity

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Im also looking at heat pumps...
I've become a huge fan of 'heat pump' technology as a way to get heat from electricity....
- Hot Water - We have a Rheemes 50gal hybrid (heat pump + regular elements) water heater which is mainstream/good-prices from Home Depot and very efficient in heat pump mode and maxes out at 450w (smaller inverter).
- Forced Air, whole house heat pump - We have a 4ton Lennox heat pump that works down to 30F/-1C with a max draw of 5000w (at 25F) - but typically runs around 3500-4000w while heating 2600sq ft house.
- Mini-splits are cool - I have a 9,000BTU on the trailer and it 'sips' power and is whisper quiet.
- Clothes Dryers - I have read about heat-pump clothes dryers. They max out at only 1,000w instead of the 4,500w of a normal dryer and 'reportedly' use only 1/3 the overall power of a regular dryer.
 
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Cheap 4-life

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I gotta say my wood boiler cuts my power usage more than anything. It only uses 400w. That’s a blower and water pump. For your size house you would need a slightly larger blower. I used to cut my wood myself.. that’s until I found out that saw mills will give you cutoffs and bark slabs for next to nothing. That takes almost all the work out of it. I fill my truck up with a chord and they only ask for $15. I burn 5 chords every winter. That’s only $75 for the winter. But more importantly my power usage is lowest in the winter due to the boiler. I’d certainly think about it some more before dismissing the boiler option. I installed-built it myself. Repurposed an old heavy duty wood stove. Roughly a week to do it. Only cost me $750 total. I attached the heat exchanger (radiator) to the heat pumps duct work.
 
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Cheap 4-life

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Also must mention that a wood boiler works very well when it’s really cold unlike a heat pump. I can’t wait till they come up with some kind of way to cool a house for close to the same power usage that the wood boiler uses to heat.
 

Solardad

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I've become a huge fan of 'heat pump' technology as a way to get heat from electricity....
- Hot Water - We have a Rheemes 50gal hybrid (heat pump + regular elements) water heater which is mainstream/good-prices from Home Depot and very efficient in heat pump mode and maxes out at 450w (smaller inverter).
- Forced Air, whole house heat pump - We have a 4ton Lennox heat pump that works down to 30F/-1C with a max draw of 5000w (at 25F) - but typically runs around 3500-4000w while heating 2600sq ft house.
- Mini-splits are cool - I have a 9,000BTU on the trailer and it 'sips' power and is whisper quiet.
- Clothes Dryers - I have read about heat-pump clothes dryers. They max out at only 1,000w instead of the 4,500w of a normal dryer and 'reportedly' use only 1/3 the overall power of a regular dryer.

+1 on heat pumps.
I have the same water heater - love it and it provides for our family of 5. Just need to enforce “7 min” showers with the teenagers...
Also installed a couple diy pioneer mini split systems and they work great
 

Solardad

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...so @OffGridInTheCity not looking to open the pandora's box but I reminded myself of your current charge controllers and inverter...
You could make a dent in your winter gap by upgrading your hardware and purchasing the Sol-Ark 12k. Just the inverter side is more than 10% more efficient. The MPPT controllers are rated up to 450v vs the 150v or so for the midnites - higher voltage = less voltage drop. ;-)
 

OffGridInTheCity

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...so @OffGridInTheCity not looking to open the pandora's box but I reminded myself of your current charge controllers and inverter...
You could make a dent in your winter gap by upgrading your hardware and purchasing the Sol-Ark 12k. Just the inverter side is more than 10% more efficient. The MPPT controllers are rated up to 450v vs the 150v or so for the midnites - higher voltage = less voltage drop. ;-)
Yes - the SolArk is very attractive. I'd need 2 of them to get the 24,000w inverter power I have now....
Efficiency (loss) is annoying. For example, my Midnites reported 18,030kwh in 2020 but I was only able to consume 15,013 - that's a 16.6% loss of 3000kwh. 3000kwh - yikes. On the other hand - the system works pretty well and as people sometimes point out - if one has space, one could add a few more panels for less $. That would be 7 panels for 16% more than the 45 I have now. I do try to keep my OCD at bay and look at the glass being 84% full :)
 

Solardad

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Yes - the SolArk is very attractive. I'd need 2 of them to get the 24,000w inverter power I have now....
Efficiency (loss) is annoying. For example, my Midnites reported 18,030kwh in 2020 but I was only able to consume 15,013 - that's a 16.6% loss of 3000kwh. 3000kwh - yikes. On the other hand - the system works pretty well and as people sometimes point out - if one has space, one could add a few more panels for less $. That would be 7 panels for 16% more than the 45 I have now. I do try to keep my OCD at bay and look at the glass being 84% full :)
Yikes... I did not know the midnites were so crummy... Just thought of another idea... I know you just bought that pallet of used cells but I noticed that you have a ground mount setup. Why not update the panels on the ground mount with some 'newer' ones like 380-420w 72 cell? you might have to buy new/longer rails but it appears you have the ground clearance to get another row also in landscape orientation. Could be a 50% bump from what you have for that one array.
 
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