Adding solar to an old on grid homestead

[Bacpacker]

My 2 cents would be for separate units. Much easier to find spares as separate pieces and more cost effective. JMHO.

 

[Mountain trapper]

One piece of equipment that I would highly recommend for any kind of solar system is an Auto Generator Start, AGS. I think I paid around $100 for mine. You'll need a generator with electric start and an auto choke for it to work. They automatically start the generator based on battery voltage, or other parameters that you choose, such as; temperature, SOC (state of charge) etc. I have mine programed through the remote control on the inverter to start the generator at 23.8 volts and shut off at Float, or 3.5 hours. My system is 24 volts made up with 12 - 2 volt batteries.

 

[viking]

The reason we went with an inverter/charger was because I wasn't going to be able to build the solar array right away, the charger in our inverter has a very good system as does our solar controller, they both start on Absorption Stage and as the batteries become more charged the charging current tapers down until the batteries become fully charged and then the charge goes into the Float Stage, there is also an Equalize Stage for clearing sulphate build up on the battery plates, with the inverter/ charger that can be forced or set for a particular monthly day, the solar controller does this once a month, the inverter/ charger I'll only use as the batteries get older when they get more prone to plate build up.

 

[Mountain trapper]

We use slightly more power than just the sun alone can provide, especially during winter. That's the reason for the auto generator start, so I don't have to keep track of the battery voltage or get up at 2am to start the generator manually. This time of year the sun provides about 99+% of our power needs. The new panels will easily provide 100% of our power over most of the year. We'll still have to depend on the generator make up for any shortage on cold, cloudy days in winter.
Other than replacing our old battery bank, this system has been virtually trouble free.

 

[UrbanHunter]

I installed the new 4000 watt inverter at the battery bank outside, and moved the 2000 watt inverter to the battery bank in the basement. So here is my wiring logic. According to the Kill-a-Watt meter the highest draw has been 1250 watts so I decided to use the 2000 watt inverter and put the 3000 watt unit into reserve.

The outdoor battery bank 12, 12V, 100AH Flooded Lead Acid, it charged by the solar panels (3 small arrays with 3 charge controllers), and is connected to the 4,000 watt pure sine inverter by 00 cables. The inverter feeds a timer circuit that supplies 120V to a single circuit automatic transfer switch (with inverter dominance and grid backup), which feeds the indoor smart charger and single circuit automatic transfer switch (grid dominance/inverter backup) which is connected to the old 2000 watt pure sine inverter which is connected to 4, 12V, 100AH LiFePo4 batteries via #2 cables. The final load supports a refrigerator, 2 freezers, and a sump pump.

So in the daytime the solar panels charge the flooded batteries, and their inverter provides power to the smart charger (for the LiFePO4 batteries) and the final load. It will continue in this mode unless the lead acid battery voltage drops below 11V, then it switches to Grid input.
The goal is to use solar to provide 90% of the power to this load and only rely on the grid for about 10%.
If the grid is down and the Lead Acid battery voltage is below 11V, the load is transferred to the emergency inverter power using the LiFePO4 batteries.

According to my calculations in this configuration, if the batteries are full and we are in heavy cloud cover with the grid down, I can go for about 48 hours before I need to dig out the generator.

Note, I have a 1000 watt and a 1500 watt inverter/charger that do not recognize AC line voltage and do not charge, but the inverters are fine. I think I am going to tape their manuals to the top and give them to charity.

I also learned that some of the "nicer" inverters with the built in GFCI capabilities do not play well feeding the single circuit automatic transfer switches.

 

[Mountain trapper]

Here's our electrical room, with battery bank, inverter, charge controller, auto start and 12kw generator. Not shown is a 55 gallon day tank, parts cabinet, electric panel and other miscellaneous tools.

 

[Neb]

Here's our electrical room, with battery bank, inverter, charge controller, auto start and 12kw generator. Not shown is a 55 gallon day tank, parts cabinet, electric panel and other miscellaneous tools.
View attachment 115467

Can you please show more details and speak about the exhaust?

I have a utility room I would like to use for my generator and the exhaust challenge is something I have to work out.

Ben

 

[Mountain trapper]

Can you please show more details and speak about the exhaust?

I have a utility room I would like to use for my generator and the exhaust challenge is something I have to work out.

Ben

I have 2 mufflers on this generator. One is inside the building, just above the generator. The other is outside where the exhaust goes up and above the roof. With this configuration I can't hear the generator running from inside the house. Our generator shed is maybe 100 feet from the house.
For some reason I can't send any pictures right now. I'll try again later.

 

[Mountain trapper]

 

[DrJenner]

@Mountain trapper that's a lot of amp hours on that system. Are these the type of batteries that water levels have to be filled every so often?

 

[Mountain trapper]

@Mountain trapper that's a lot of amp hours on that system. Are these the type of batteries that water levels have to be filled every so often?

These batteries are lead acid. I installed them 1 year ago in August and haven't had to add water yet. Since they are 2 volt batteries, there is only one cell to fill, when water needs to be added. So far maintenance on these batteries have consisted only of checking the water lever and brushing off the cables.

 

[DrJenner]

These batteries are lead acid. I installed them 1 year ago in August and haven't had to add water yet. Since they are 2 volt batteries, there is only one cell to fill, when water needs to be added. So far maintenance on these batteries have consisted only of checking the water lever and brushing off the cables.

That's pretty decent.
Edited to add: my husband wants to know how many watts you use on average in a 24 hour period (running on pure battery power when it's cloudy).

 

[Mountain trapper]

That's pretty decent.
Edited to add: my husband wants to know how many watts you use on average in a 24 hour period (running on pure battery power when it's cloudy).

Good question. I'm not sure that I'm smart enough to figure it out.
We're currently running on 10 - 295 watt panels. With the 10 panels on cloudy days our generator starts every other day and runs for 3.5 hours. It's programed to start at 23.8 volts and off at float. Our battery bank is 12 - 2 volt batteries @ 1169 ah each.
The new panels that I just installed are 4 split panels at 405 watts each. I figure that when these additional panels are online, the generator shouldn't need to start at all, at least not until a long cloudy spell in winter.
Last year with our old battery bank the generator averaged about 6 hours run time per day over a 12 month period. With our new battery bank, we're averaging about an hour and a half per day on the generator.

FYI, our system runs the house, shop and fur shed. We have all conventional appliances; washer/dryer, 2 freezers, 2 refrigerators, 5 TV's and 1800 sqft house.

 

[viking]

Mountain trapper is your MagnaSine inverter the stackable one, I originally bought a stackable inverter and a router that was needed for adding up to three more inverters, four stacked inverters can provide up to 17.6 KW of 120/240 VAC, but we found that we can get by very well with just 4,000 watts, powered by six battery banks of 24VDC each. As an interesting aside, when I updated my battery wire connecters, 2/0 jumpers and 000 battery to inverter wires cost just over $300 the 4/0 wire cost $9.00 a foot. Our system has very little electrical loss because I used large wire sizes and shortest possible distances from batteries to inverter and the solar array to the controller and controller to the batteries. I did as the owners manual says to do.

 

[UrbanHunter]

This week I got a new larger smart charger for one of my backup stations. The original one was only 20AMP/12Volt and it took too long (20 hrs) to recharge the batteries for the oxygen machine backup using AC from the solar inverter. The new smart charger is 35AMPs and can recharge them in 12 hours so I could theoretically charge the pack each day and keep everything working.

The current solar array is not able to keep up with everything for 24 hours, if I allow my system to deplete the lead acid batteries I could cover 16 hours a day, but I am not willing to do that. So I am using timers to only use the solar power for about 8 hours a day so the batteries end each day with a full charge.

Dropping all this into the old spreadsheet tells me that I will need to increase my battery capacity 1600 amp hours and the solar arrays to 3000 watts to keep up with just my basic equipment needs.

So Looking at it a little closer, if I only run the freezers and fridge 5 hours a day my battery bank and my existing array could just cover my needs. If I could just add 600 watts to my existing array I could cover a full day. All this is assuming 6 hours of solar availability per day. In the summer I would have a surplus but in the winter I would be pushing it....

 

[Bacpacker]

Nice upgrade Urban

 

[Mountain trapper]

Just got the new solar panels wired together. Right now they are putting out 176 volts. Next step will be to connect them in to the combiner box and then wire up the new charge controller. But first we're taking the rest of the day off and going swimming.

 

[UrbanHunter]

Last night I made the last measurements for the new solar array frame, not a complex structure but it has taken me a while to get it finished (I hope to cut the last lumber tonight after work). I did get the new charge controller for them installed and connected to the battery bank and leads to the solar panels so once the frame is finished it will only take about an hour to install all the new panels and have them connected to the system. This will complete my distributed solar array plans.

This will put me up to 2,200 watts of solar and 24,000 watt-hours of energy storage. I still need to install some disconnects between each solar array and its charge controller, I have them in a box but ran out of ferrules, the plan is to install each disconnect just below the charge controller to keep the runs short. I am currently using the solar during the daylight hours to run all my food storage freezers and the wife's AC so I am starting to get some payback. Once it turns a little cooler I will switch it over to power the greenhouse heating and lighting instead of the wife's AC. Currently, 9,600 watt-hours of the energy storage are LiFePO4s that are indoors and kept in reserve for emergency backups (that was the original plan for the first solar array) and the rest are flooded Lead-Acid units that are in the greenhouse/charge-controller/battery-bank area and they cover daily supplemental requirements.

 

[UrbanHunter]

I finished the frame and installed the last of my panels today. It was 5:30 and overcast by the time I finished but it was charging. I think the stuff I needed to install the disconnects arrived today, that will finish my solar projects for this season.

I got my power bill today, the temperatures are the same as last year, the wife is keeping the house cooler, and we used 13% less power (before these upgrades). So I am thinking that we are moving forward.

My emergency planning hat says that I need 450 watts for the bare minimum, and experience says that I need about 5 times that to account for bad weather days. All said and done I think I have done all I can do..... Well I guess I could start planning an energy storage upgrade for the lead acid battery bank. I think that the batteries are fine, I just don't have enough of them.....

 

[UrbanHunter]

Today we are totally cloud covered with heavy rains, I am still getting about 100 watts going into the batteries, so this is a big improvement. But this is another reason why I try to keep my batteries at 90% at the end of the day.

 

[UrbanHunter]

I had been using analogue timers to turn things on and off, switching between inverter and grid.... but they were bad at losing time and just became a pain...I purchased some digital timers and discovered that they had their own internal battery, so no more losing time and they timers keep time even when there is no power being supplied to them.. It solved a lot of my problems.

Yesterday, I checked the battery room at about 4PM and noticed that all the charge controllers were flashing (The solar was providing more power than the the system could store), the batteries were 100% and the inverter was powering the wife's AC and the freezers! Because I had surplus power I added the growing station lights to the inverter load... Being able to balance your load with your capacity can be a little tricky. We are still having days in the mid 80s (F), and the wife's sitting area still runs hot. We are expecting the highs on Sunday to drop into the 60s, which should allow me to winterize her AC unit.

 

[Mountain trapper]

Since we've had snow, fog and clouds for several days now, we're getting very little power from our solar panels. The backup generator is running for about 4 hours a day now to keep the battery bank charged.

 

[viking]

My son uses a propane, on demand water heater for his trailer, he really likes it because it is very efficient, the only problem is it's mounted on the outside of the trailer and can't be used on freezing days, he told me that he is considering getting a small on demand unit that will fit where the original propane fired water heater is mounted, the only issue he said is that that unit is rather costly, he'll probably get it anyway so that they have hot water available in freezing weather. I will say one thing about having enough solar panels for low sun days, I kind of wish I had bought a pallet of the 195 watt panels to have on hand for enlarging our existing array, it seems that Grape Solar no longer has those panels and the reason I like them is because they are made with a higher count of cells and provide over 36 VDC per panel, running them in a series of two per bank they consistently give over 80 volts, often even on cloudy/rainy days, I've even had a coating of snow on them and they still put out over 70 volts, so running through an MPPT solar controller they still give adequate solar charging of the batteries, however an additional 1,560 watt array would certainly help.

 

[Aerindel]

My son uses a propane, on demand water heater for his trailer, he really likes it because it is very efficient, the only problem is it's mounted on the outside of the trailer and can't be used on freezing days, he told me that he is considering getting a small on demand unit that will fit where the original propane fired water heater is mounted, the only issue he said is that that unit is rather costly,

Well, I don't know what rather costly is for you, but I've been heating all my water for years with an on demand heater from amazon that cost about $300. The double wall stainless chimney I had to buy to vent it was pretty expensive though.

 

[DrJenner]

Since we've had snow, fog and clouds for several days now, we're getting very little power from our solar panels. The backup generator is running for about 4 hours a day now to keep the battery bank charged.

Same here
We’ve been trying to conserve fuel

 

[viking]

Well, I don't know what rather costly is for you, but I've been heating all my water for years with an on demand heater from amazon that cost about $300. The double wall stainless chimney I had to buy to vent it was pretty expensive though.

It's rather costly for my son, but like many other things he's had to do to have an affordable living place, he'll probably put it on his credit card, he's already $30,000 in debt on cards, largely due to getting he and his girlfriends travel trailer set up for long term living on our property, due to the pretty much the unavailability of any affordable property, hemp growers and pot farmers have really messed with the prices of even raw land here in southern Oregon.

 

[Aerindel]

Seems like at that point he should just go bankrupt.

I've never done it myself, not even possessing a credit score, so impossible for me to get in debt through conventional means.

But everyone I know says its the best thing they ever did. (most of them do it every seven years) I don't understand it myself, but they say that people who have just gone bankrupt are extremely desirable to credit companies and they fall over themselves to lend you money the day after you go bankrupt.

 

[UrbanHunter]

My little solar array was initially designed for emergency backup but the more I could use it, the more I wanted to use as much of it as possible (only to get a payback). So now it is winter and overcast a lot and I have been running into problems trying to balance the battery bank and the grid utilization. I had tried cutting off the DC power to the inverter, but that in itself draws a lot of current. I tried digital timers, but the clouds, rain, and snow are not on a regular schedule. So I started thinking photo-cells and using daylight to control things, but most of those are designed to turn off the load in the daylight, which is just the opposite of what I needed.

This is where Rube Goldberg came into play... I have a voltage controlled dc switching circuit, I have a couple of photo-cell switching AC devices, and a couple of automatic transfer switches... I purchased a 3 watt dc reading lamp and tested to see if it could trigger the photo-cells, yes... on to next step. I made a "black box" that contains my solar cells for switching the grid supplied current to my single circuit automatic transfer switches, and the 3 watt reading light connected to my voltage controlled DC switch. When the battery bank gets fully charged (above 12.8 Volts) the light turns on and the grid supplied AC turns off, so everything runs off the inverter until the voltage drops to 12.1 Volts at which point the light turns off and the Grid takes over the load. I wish I were an electrical engineer as I know that this type "circuit design" should be very easy for any college level electrical engineering student to create. Anyway, my Rube Goldberg improvised system seems to be working, the voltage on my battery bank is staying above 12 volts, the standby load on the battery bank is 30 watts, this is the inverter, the DC voltage controlled switching circuit, and the DC reading light. I have been watching the overnight battery bank voltages when the grid is fully powering the load and the battery bank voltages have been hovering around 12.3 volts (+/-0.3 volts).

So now, when I have sufficient power in the battery bank the inverter powers my loads, when the battery bank is lower than 12.2 volts everything switches to the grid, and when the grid goes down the loads all switch to the battery bank regardless of their state of charge. This should allow me to maximize the utilization of available excess solar power and keep my emergency backup solar power online and at the ready when I need it.

FYI - My controller is truly a "black box" because all the wires go in and the magic happens when the box is all closed up to control light exposure..

 

[UrbanHunter]

So today we are having a mixed bag, with some snow, lots of wind, and some sun. The solar isn't putting out a lot but it is putting out enough to get the battery voltage up to 13.2 (no load) before the "black box" kicks the load onto the inverter and then the batteries are pulled back down to 12.2 V fairly quickly, but during that time I am getting some usable power. Not a lot mind you, only 0.5kwh in 3 hours of observation, but we are talking a partly cloudy day with snow.... That is only about 10% of what I view as my maximum capacity and it is 19% of my connected load... But, usable power is money saved, so I'm happy. Now I just need to clean up my wires a bit and move to the next project.

 

[UrbanHunter]

Well the first day of using the new control system is over (it's sunset here right now), although we have had an overcast day I was able to utilize 2kWh's and the battery bank is still at 12.6 Volts. According to my Kill-a-watt meters the maximum load that I had on the inverters was just under 3kW, I think the average load was closer to 1000 watts. The most in-put that I saw from the solar charge controllers to the battery bank today was about 700 watts, so the system is doing what I wanted, it is allowing me to get some usable power even when the arrays can't provide enough power to meet all my needs... I would call that a win.

The other nice thing is that because I am removing the load before the inverter reaches that low voltage warning, I don't get those annoying low voltage alarms. This control system should help me maintain my batteries for a longer time to....