Solar Projects the good, the bad, the cutting edge, the starter system,

Rebecca,
Very impressive and I must say that a part of me would really like a job like yours, teaching HS in the Himalayas, just wow! I really want to ask you about solar heat. That water heater set up looks interesting, if that's what it is, I don't understand how it works. I'm not familiar with any solar to heat options for heating a home. So many questions.

Mary Haasch wrote:Rebecca,
Very impressive and I must say that a part of me would really like a job like yours, teaching HS in the Himalayas, just wow! I really want to ask you about solar heat. That water heater set up looks interesting, if that's what it is, I don't understand how it works. I'm not familiar with any solar to heat options for heating a home. So many questions.

Yes, the photo is the solar water heater. It's sold here in India, was being subsidized in my region and was installed by some local guys who'd made a business of it. The glass vacuum tubes are from China but I think the rest of it is made in India. The photo is of the 200 liter tank that holds the water, and the wonky insulation we'd wrapped around the outlet pipe where it traverses until it enters the wall of the house.

The house is passive solar heated, by a seasonal greenhouse attached to the downstairs, (I've posted it elsewhere here) and by half-trombe walls upstairs. Other systems might make the house warmer, but I love having the attached greenhouse all winter.

Rebecca Norman wrote:Hi David! I'm enjoying this discussion that you started, though I don't understand the technical bits.

I live in one of the most solar-friendly places on the planet, high desert at 10,500 feet in the rainshadow of the Himalayas.

I got my house built 5 years ago. I decided to use the abundant sun for passive heating of the house, and for water heating, and not (yet) for electricity. Grid connection was basically free for me, though it took a year or so to get them to put the poles up. Until then, we had an insulated wire lying on the ground, from a stolen connection from the nearest pole. (Rules are um... loser here in India)

If one of your big energy uses is heating the house or water, it's much better to use the sun's energy directly for heat rather than involving electric. Solar heating is much more efficient than converting the sun's energy to electricity, converting that to chemical energy for storage in a battery, converting it back to electricity to travel to the heating device, and then converting it to heat. Each of those transitions is not very efficient. You'd need at least ten times the area of solar collection to get the same amount of heat from solar electric than from any solar thermal method. (David or anyone, please correct me -- I'm guessing it might be 50 times the area, but panels and batteries are getting more efficient so maybe not)

The solar water heaters sold here in India are amazingly effective. They are glass vacuum tubes. You know those Chinese thermoses with a double-walled glass inside, that keep water boiling hot overnight so you can steep tea in the morning? Yeah, same stuff but 6-foot tubes. I sprung for the bigger model, 200 liter tank with electric backup. It's on my flat (desert) roof.  So far, wonderful, but the day one of those tubes breaks or leaks, my entire 1000 liter cold water storage tank will drain out onto the earthen roof and it's gonna be a huge problem.

Now that I'm settled in and living in the house for 5 years, I'm thinking I should add solar electric as well. Until now, I just have 2 big batteries (150 amp hours?  not sure) and an inverter tied to the grid, because the grid goes down for an hour or so a few times a week, and for whole days at least once or twice a year. I had two separate circuits installed to all the rooms: one circuit for lights and chargers on the inverter, and one circuit that is mains only, for the heavier devices and water pump. Especially in winter, the voltage is rarely high enough to run the pump, so I have to keep an eye on the voltage ,and quick run the pump when the voltage is 200V or above (Voltage is nominally 220-240V here. Ha!) I have 1000 liters of storage tank in the top of the house so can go a few days without a refill, if we're careful.  

I'm not at home and sorry, I don't have a photo of the whole water heater, only a snapshot we took of our half-assed pipe insulation job.

What a great addition thank you for the post. So while I agree that solar heating is much better accomplished passively and through solar heating there is a limit. Solar thermal is much more efficient then solar electric so for each sq metre of solar heating you would require 3.5 sq metres of solar electric panels if all you cared about was heat. Conversion losses would only occur if you stored the electricity and are on par with the losses you get when you store heat in water. Personally I think you are doing it perfectly for your area and needs. My lived experience is different as here solar hot water would require 1) a sealed glycol loop due to cold, 2) a circulator pump, 3) a heat exchanger into a tank 4) a differential controller, 5) a dump load for all the excess heat it produces 6) Extra insurance as insurance companies usually have special waivers for solar hydronic. (not making that up my insurance for solar install specifically states that I will not do any solar hydronic work). Your power situation reminds me of the back story for one of the most successful inverters of all time the Trace DR series. It was named the DR for "Dominican Republic" as it was used for backing up a grid in residential homes when the grid went down... Great unit.  picture is my DR2412 in probably 2007
Cheers,  David

These glass thermos tubes are pretty damn good despite cold. We have about 6 to 8 weeks of pond hockey, normal minimums of -20C (-4F) most nights of January and the occasional -26C (-15F) and the frost line is roughly 3 feet. People are also using the same heaters in colder places in the region.

These glass vacuum tubes and the insulated tank have no trouble with it. Even in the morning the water is nice and hot. We taped the cold inlet pipe and the hot outlet pipe together, so running a little hot water downstairs fills the hot water pipe, which runs next to the cold water inlet inside a nice big wad of foam. Even if we forget to run a little in the night or early morning, it doesn't freeze, as long as my cobbled-together insulation stays intact. If I left the house empty through the winter without anyone to use hot water or trickle it in the night, the pipes connecting it to the house might freeze, and the rumor is also that the glass tubes could boil dry and crack.

It's rare to have 12-month running water in my region, so most people have these heaters not plumbed in to the house, but freestanding outside, and they pour a bucket of cold in one end and catch the bucket of hot that comes out the other.

Rebecca Norman wrote:These glass thermos tubes are pretty damn good despite cold. We have about 6 to 8 weeks of pond hockey, normal minimums of -20C (-4F) most nights of January and the occasional -26C (-15F) and the frost line is roughly 3 feet. People are also using the same heaters in colder places in the region.

These glass vacuum tubes and the insulated tank have no trouble with it. Even in the morning the water is nice and hot. We taped the cold inlet pipe and the hot outlet pipe together, so running a little hot water downstairs fills the hot water pipe, which runs next to the cold water inlet inside a nice big wad of foam. Even if we forget to run a little in the night or early morning, it doesn't freeze, as long as my cobbled-together insulation stays intact. If I left the house empty through the winter without anyone to use hot water or trickle it in the night, the pipes connecting it to the house might freeze, and the rumor is also that the glass tubes could boil dry and crack.

It's rare to have 12-month running water in my region, so most people have these heaters not plumbed in to the house, but freestanding outside, and they pour a bucket of cold in one end and catch the bucket of hot that comes out the other.

that makes sense. It would be the inlet and outlet that would be susceptible to freezing. There is no reason about half of the US couldn't use a solar hot water heater. It's due for a rebirth I think. I would still do a glycol loop pump and heat exchanger here if I was doing it professionally since western homes have grown soft and like their devices to run untended for decades.

Mary Haasch wrote:I'm living in a small cottage with a 50 yo in the wall electric furnace (not used much until the last 2 years) and I'd like to add solar electric. I've preliminarily spoken to two different companies, not sure what I think of either one, but both think putting panels on the roof is cheaper than putting panels on the ground in the open area. The cottage roof panels would require new roofing which has about 5 - 7 years of expected life and cutting down the trees which have grown up close to the building. While both things would need to be done eventually, the open area installation seems more immediately cost and effort effective. In addition, the ground-based system in the open area could be used to power the workshop, the garden shed and the eventual small barn planned for the open area (the workshop and garden shed are existing). Any words of wisdom?

It's a very common ploy to say that you need a new roof before they can install the panels, but the good news is that they just happen to know a local roofing company who can give you a good estimate. Get a second opinion on the condition of your roof.
Ground mount is in my mind far superior especially if you will be doing a DIY install. I used 250 watt panels because of their size and weight, or rather lack thereof. Even with those smaller panels climbing a ladder and carrying them up to the roof in even a moderate breeze is not something to be undertaken lightly.
I just don't bounce as well as I used too after falling off things

Been doing solar since pre-Y2K.  And those panels are now 30 years old still putting out the same power since the day they were installed.
4X Uni-Solar 21W flat panels
1X SolarCon 280W flat panel
4X Thunderbolt 25W panels (Harbor Freight)
1X Renology Charge Controller 30A
1X MorningStar Charge Controller 10A
(464W total on 2 systems).  

This system isn't to power an entire hose, rather it's a system to take care of the farm where it's not practical to run power out into barns and pastures.
Fence energizers, barn lights, dairy building power, bug zappers and water heaters.  I charge all of my lithium power tool batteries and other batteries too, including the farm radios.  At times, I'll take the RV 12VDC coffee maker and make a few pots as well.  

A tiny house couple in the area runs a single 320W panel for all their tiny home needs.  Most of their setup is all 12VDC, including the small fridge and water pumps.  They have a VAWT that churns out about 180W on average 10mph or better wind at night.  It looks very home brewed.

Some of those systems in this thread look very slick and well outside my budget.  Glad others can manage a good payback and upkeep over time.  I just can't climb on roofs anymore.

Neil Bendy wrote:
It's a very common ploy to say that you need a new roof before they can install the panels, but the good news is that they just happen to know a local roofing company who can give you a good estimate. Get a second opinion on the condition of your roof.
Ground mount is in my mind far superior especially if you will be doing a DIY install. I used 250 watt panels because of their size and weight, or rather lack thereof. Even with those smaller panels climbing a ladder and carrying them up to the roof in even a moderate breeze is not something to be undertaken lightly.
I just don't bounce as well as I used too after falling off things

Needing a new roof is my idea based on the expected lifetime of the roof that is on the place. To their credit, neither of the companies tried to sell me any roofing.

I appreciate your thoughts on the ground mount and the size of the panels you used. Do you have any system of realigning the panels for the change in the position of the sun?

Mary Haasch wrote:

Needing a new roof is my idea based on the expected lifetime of the roof that is on the place. To their credit, neither of the companies tried to sell me any roofing.

I appreciate your thoughts on the ground mount and the size of the panels you used. Do you have any system of realigning the panels for the change in the position of the sun?

When I first researched how to mount the panels I looked at motorized mounts that would track the sun, but for the extra power generated vs. the cost the numbers didn't add up for me.
The best compromise would be the ability to manually move the panels every few months as the sun's path changes.
But others who are far more knowledgeable also believe that the benefits don't justify the cost and extra maintenance of a motorized system.
https://www.solarreviews.com/blog/are-solar-axis-trackers-worth-the-additional-investment
https://unboundsolar.com/blog/should-you-buy-solar-tracker

Neil Bendy wrote:

Mary Haasch wrote:

Needing a new roof is my idea based on the expected lifetime of the roof that is on the place. To their credit, neither of the companies tried to sell me any roofing.

I appreciate your thoughts on the ground mount and the size of the panels you used. Do you have any system of realigning the panels for the change in the position of the sun?

When I first researched how to mount the panels I looked at motorized mounts that would track the sun, but for the extra power generated vs. the cost the numbers didn't add up for me.
The best compromise would be the ability to manually move the panels every few months as the sun's path changes.
But others who are far more knowledgeable also believe that the benefits don't justify the cost and extra maintenance of a motorized system.
https://www.solarreviews.com/blog/are-solar-axis-trackers-worth-the-additional-investment
https://unboundsolar.com/blog/should-you-buy-solar-tracker

seasonally adjusted manual mount will give you about 50 percent of the gain you get from trackers. The motorized trackers are just not worth it especially in snow country.

Sometimes I get to visit some really cool places. This one is a biodynamic farm in central Ontario who's main house is over 140 years old. There has never been power pole near it so there is generations of off grid infrastructure built into the place. the well is actually in the basement so it had a hand pump.  At first it had a 12 volt only system for a few basic lights usually with batteries recharged mostly from a generator. Then came the solar revolution and the rise of the first charge controllers and inverters.  Small arrays by today's standards but there are 2 60 amp charge controllers on the wall most likely for the wind turbine as they are much too big for the old array. Notice the analog meters on the wall to keep track of solar production wind production battery gain or drain etc; someone put a lot of love into that wiring. Next the previous owners invested in one of the first trace inverters the black ones that looked like an amplifier but it eventually died. Next came the true workhorse of the older off grid world; the venerable DR2412 inverter. There are still a lot of these kicking around but this one while still running when replaced is more of a tribute to the house's past now. There was an owner built wind turbine and an impressive tower in place but the turbine shook itself apart years ago. The current owners inherited a lot of this stuff when they bought the place but kept up the systems already there. They moved over to a 24 volt outback system a number of years ago and a 2kW array but still run all the 12 volt systems in the house via a 24 to 12 volt converter newly installed to replace a very inefficient AC 12 volt power supply pictured below; that alone is probably saving them 300-500 watt hrs per day which is huge on a small system. The hand pump moved to an ac pump, the gas fridge moved to an electric one. The gear gets better and more affordable as time goes by. There is life after 12 volts even if you have invested heavily over the years in it. I just have a lot of fun in these ones trying to make things work without bankrupting people or tearing everything out. Thanks for walking through my off grid historical tour!
Cheers,  David

I have not been great at posting systems I've worked on recently. So the current one is a bit of a throwback but still viable and bullet proof. The high frequency all in one inverters have taken over but a component based transformer based system is still bulletproof. One of the issues I had was the newer panels have gotten so big that I had to build myself a hoist to get them up the rack. also with all the new restrictions around batteries and living spaces a shed was constructed to take all the gear.

This system:
Magnum 4448PAE
Midnite solar Classic 150
19.6 kWHrs of AGM battery
4.4kW of solar array
Cummins standby propane generator 13kW

[youtube]https://youtube.com/shorts/n0bpxO8o0dM?si=X-uK42103Xp2qMsu[/youtube]

Cheers,  David