Questions about starting small - 1kW

vinn · 01-10-15, 02:41 PM

We purchased our home 6 years ago and have been remodeling it. Since then, we've replaced all of the appliances with pretty efficient models. Our primary heat source is a wood burning stove. In other words, our energy use is ok - we're about 15000kW a year. The vast majority of that is in the winter because we use electric heat to supplement the wood stove. It's not ideal, but it's working

Our furnace in the house isn't usable and would need to be replaced before even considering using it. If so, we'd replace it with a propane model (most likely). Anyway, the cost of all that would likely approach $8,000. I'd much rather invest that money into a PV system and just forget about the furnace altogether and keep doing something similar to what we have.

Now, I'm fairly handy and I've even done some small off-grid solar installations in the past (for radio installations, etc). We live in a very rural area and the few people who work with PV here are in no way interested in even interested in this. They'd much rather try to sell me a $1000 survey that consists of a lot of things I've already done myself (NREL calculations, etc) and then sell me a $30,000 PV system. Also, we're a bit backwards where in rural Montana and everyone I've talked to has told me microinverters suck and to not use them - that raises a bit of a flag for me because everything I've read tells me that's exactly what I want.

So here's what I want to do, someone tell me if this is a terrible idea:
1. Put in a very small system - 4 panels of Astronergy 305W with 4 Enphase M250 microinverters. I'm going to have a lot of hoops to jump through for the installation - namely, finding an electrician than can wire the grid-tie, getting the net metering set up with the local electric company, etc. I suspect it's going to take me longer than I think and I don't want 16 panels sitting around going unused for what might even be a year. I also want to learn how to do the mounting myself, so I'm going to start with small size.

2. Microinverters will let me expand later and I'd like to phase this system in over about 5 years. The Enphase M250 is new enough that it will likely still be available for purchase and I can match similar enough panels with it.

3. The other reason I want to phase this in is because I need to verify my mounting option is viable... the only place I have to mount these panels is a slightly tilted westerly (270 degree) angle. I'm sure that just raised a red flag, so here's the NREL calculations compared to optimal conditions (180 degrees):

kWh / m^2 / day (yearly average):
180 degrees, 40 degree tilt: 4.73
270 degrees, 5 degree tile: 3.92

Ok, so my mounting option is only 83% as efficient as the optimal configuration. I can live with that. We're fairly sunny here, so hitting 4 kWh/m^2 is pretty good.

4. Eventually I'd like to build this out to about a 5kW system. I'm not in a rush, maybe it'll take a few years. I'm sort of betting that panel prices will come down and efficiencies will go up.

Bad idea? Should I focus on something else?

where2 · 01-10-15, 05:14 PM

I'd say: Do it, and don't look back... (but I might be biased)

The only part of the 4.4kW array on my roof that was farmed out for hire was the structural engineering to keep the array on the roof in a 3-second gust of 170mph (required by the local building department). I drew the three line electrical diagrams, I obtained the state certification on the system (basically a $250 charge to review my three line diagram to be sure the system design meets or exceeds NEC 2011), I pulled the structural and electrical permits, I did the install, I did the hookup to my service entrance panel, I passed all my in-progress and final inspections. I signed off with the power company and showed them my passing final electrical inspection to get the net meter installed. It's my house, and my building department is fine with owners doing modifications to their own home with proper permits as long as the work meets or exceeds the current local building codes. (must be owner occupied, cannot be rental property).

You're probably thinking: Where2 must work for an electrical contractor or something? The answer is: ~sorta. I have a bachelor of science in Surveying and Mapping, and I'm a licensed professional surveyor & mapper in two states. At the moment, I work for a low voltage electrical contractor designing show control systems, audio & video systems for theme parks, cruise ships, and an occasional mega-yacht. The only part of working for the low voltage contractor that came in handy was having a copy of NEC 2008 around (since NEC 2011 wasn't a complete re-write). I use AutoCAD all day, so whipping together a three line diagram took a few evenings of my time (a good portion of the time was actually figuring out where the WEEB grounding clips belong, and showing how the whole racking system is grounded).

If you have questions, feel free to ask. I'm already working on my design for PV system #2 for a property my wife and I recently bought at 45.8°N. Before we made an offer on the property, I went to the town office and asked what modifications to the building would require permits, and if anything was off-limits to home owners who pulled permits and had their work inspected. Now that I have one complete design drawn, #2 is going to be much easier! If you're thinking the enphase system is pretty simple, you would be correct. There are twenty M215's on my roof. I collected 17.8kWh today.

I called one structural engineer (referred by a friend from college who is a local architect), the guy actually tried to talk me out of designing and installing my own PV system! Fortunately, I was able to locate a structural engineer I had previously used (he had since moved his family to Colorado when the economy tanked), who retained his license in FL and was more than willing to work with me and cash my check. The structural engineer I used now has a PV system on his own house outside Boulder, Colorado.

I will say this: Item #3, that 270° facing roof with only a 5° tilt may be a bummer. How much snow do you get? A ground mount facing 180° with the proper tilt may justify the added expense of the ground mount. It also makes it easier to rake the snow off and get back into production in winter (or so I hear, it was 74°F at my house today). The property I'm designing PV system #2 for has a 100PSF ground snow load. I'm still debating if I want another 4 pounds per square foot (~solar array) on my roof in addition to the heaps of snow, especially if I'm not there to rake it. Ground mount with adjustable tilt is looking better and better. I just need to get it high enough to stay above the drifting snow banks!

where2 · 01-10-15, 05:42 PM

I don't see an Astroenergy 305 on the Enphase compatibility list. http://enphase.com/global/files/Enph...ility_List.pdf

The info I find on Wholesale Solar indicates the Astroenergy CHSM 6612P-305 is a 72 cell panel. Did you run the numbers from the spec sheet on the 305 to verify compatibility using this website:
Module Compatibility Calculator - Enphase Energy

I can certainly see where having an oversized PV module for a particular inverter when it's mounted at a less than ideal direction and tilt may work to your advantage. I've always been amazed that my 220W panels rarely approach 220W in my climate on my installation. My array is rotated 16°W of South, and not at a tilt optimized for my latitude.

vinn · 01-11-15, 11:44 AM

Thanks for the encouragement! You're right on the Astronergy panels, but the idea is the same - use an oversized PV panel so I can eek out a bit more from it.

Quote:

Originally Posted by where2

The only part of the 4.4kW array on my roof that was farmed out for hire was the structural engineering to keep the array on the roof in a 3-second gust of 170mph (required by the local building department).

I think inspections and such are the hardest hurdle for most people - here in rural Montana it's really not a factor at all. I think contractors in the rest of the country would be shocked and horrified by the near non-existence of building codes and permits needed here. For example, I've done most of my own wiring in my house as we've remodeled and brought in an electrician on the trickier bits.

Having said that, I will do it all properly just like you did. I have friends who are structural engineers, electricians and such. Northwestern Energy used to pretty much require that only a qualified installer could connect up via net metering. Now that's only a requirement if you go through their grant program.

So, in the end I'll just need an electrical permit and no building permit.

Quote:

Originally Posted by where2

If you have questions, feel free to ask. I'm already working on my design for PV system #2 for a property my wife and I recently bought at 45.8°N.

So that's pretty close to our latitude.

Quote:

Originally Posted by where2

I will say this: Item #3, that 270° facing roof with only a 5° tilt may be a bummer. How much snow do you get? A ground mount facing 180° with the proper tilt may justify the added expense of the ground mount.

We live in town and have a small yard. Even if we did have room somewhere in the yard, the trees across the street would shade a lot of it. By getting it up high I can avoid that. (Another reason for the microinverters - one of my own trees is just tall enough that I might get a tiny bit of shade on the one corner where I want to install it in the early morning hours.)

With regards to snow, surprisingly we don't get that much on the roof - it's dry almost all winter. We have pretty high winds (which is something I'll have to design for - the roof mounts will have to be bombproof and preferably not allow wind to get under the panels, although I do think I need some air circulation to vent excessive heat for the three months of the year it gets hot.) The wind blows most of it. It does get warm enough where we are that it typically melts off in between storms. (It's 36 degrees right now and we don't have much snow around.)

Now, the surface I want to mount this on, since it's kind of flattish, potentially I could build some kind of structure to get the 180 degree orientation. However, the tilt involved on it would catch the wind - I think making it structurally sound enough is way out of my league. The sustained winds regularly destroy things around here, so I think it needs to be mounted flush.

where2 · 01-11-15, 11:25 PM

If microinverters have issues, I expect I'll find them on the upper row of panels at the house in Florida. Looking through my historical graphs, the inverters on the upper row are running 136°F at mid-day in August. An identical inverter on the lower row of panels is running 123°F. I intentionally mounted the inverters along the rail closest to the edges of the array, in the event I had any issues. Heat is not the friend of electronics.

The modularity of microinverters was one of the things that sold me on them. Initially, I wanted to do the sort of phased system you envision. In the end, the permitting hurdles and extra costs of doing a multi-phase install pushed me to delay my installation and wait until I could do it as one big job.

I've got 528 days running days on my system to date. After 528 days, I'm averaging about 0.79kWh per day per panel. Although at first glance it looks like I have a spectacular view of the southern sky, I get random bits of shade from trees in the neighbors yards (and one of my avocado trees). At an average of 15.7kWh per day from my 4.4kW array, I still have an electric bill. I just don't give as much to the power company as I used to...

NiHaoMike · 01-11-15, 11:53 PM

If the main use is heating, it would probably make more sense to go with a solar thermal setup. Also look into DIY wind turbines.

stevehull · 01-13-15, 06:01 AM

I agree with Mike on using other ways for heating.

I have used PVwatts for calculations and being slightly off due south is only a 5% loss. But the BIG loss is your tilt with your almost flat roof. And the sun has a low angle in the winter so you would need to tilt them up.

All that said, using electricity for winter heating is very inefficient as you can use those construction $ to buy/build a geothermal heat pump (GTHP). That would be where I would concentrate rather than PV to run electric resistance heaters.

A GTHP can extract 4-5 times the amount of heat from the ground with one unit of electricity. In other words, you run the GTHP to leverage FAR more heat out of the ground so it is 400-500% efficient. Or another way to look at it is that your annual heating costs are 1/4 to 1/5 with GTHP compared to resistance heat. Not 20 to 25% less but 75 to 80% less.

That is what I would do with your money rather than use PV panels to make electricity that is very inefficiently used as a resistance heater.

Or get a propane heater and use the PV panels to decreasing your electricity consumption for lights, etc. A four panel system (1 kW) would do a LOT!

Steve

Steve

vinn · 01-13-15, 02:22 PM

Quote:

Originally Posted by stevehull

All that said, using electricity for winter heating is very inefficient as you can use those construction $ to buy/build a geothermal heat pump (GTHP). That would be where I would concentrate rather than PV to run electric resistance heaters.

Interesting. I really hadn't considered that because everyone I know that's done anything like that has had TERRIBLE luck. Still though, I'm not sure if it's an option. I'm a TERRIBLE plumber (partly because I absolutely hate it), so it's probably not something I can do myself. Or is there some kind of DIY info out there I haven't seen?

Wind isn't an option for us - our wind speeds are crazy and the air is very turbulent. I've actually done some small scale installations and there's very few products on the market that'll hold up. I have a pile of destroyed blades to attest to that. Considering we live below a bench and have a lot of two story buildings around, I'd have to put up a 100' pole just to get to the good wind.

I think I still like the idea of PV because it's within the realm of something I can accomplish on my own. Our electric heating costs, not including our hot water heater, in the winter are a max of $70 /month. That's about 1/3 of our usage, max. So, there's still something to be gained by putting in PV even if I solve the heat later.

pinballlooking · 01-13-15, 02:47 PM

I was going to start smaller and grow the solar array. But once I looked at the extra money and work needed to do it. I decided not to do go small.

My electric company wants a $100 fee every time you make a change. (This really adds up)

You have to have change docs and drawings each time you make a change.

It has to be inspected every time you make a change. (Permit fees and inspections you need to be there for)

I went with Enphase microinverters you need one Envoy for 1kW or 20kW or more.

Panels are much cheaper by the pallet. 5 panels cost almost the same to ship as 20 panels.

You would still need to put in large wiring in for where you wanted to be in the end.
So wiring cost is the same if you go small or bigger.
The racking is long and needs to be trucked shipped. All this cost adds up.
Taxes would need to be done each year to get a tax credit.

You get the point…

I am not saying it can’t be done but just some things to think about.
If you know a solar installer you can Maybe buy some stuff From A big job he had. You might be able to keep the cost down some.

My array
http://ecorenovator.org/forum/solar-...lar-array.html

check out Where2 array it is closer to what you are looking at.
http://ecorenovator.org/forum/solar-...tandard-3.html

where2 · 01-13-15, 09:22 PM

Thank you Pinball, I'd forgotten I had a link with the install photos floating around on ecorenovator.

01-10-15, 02:41 PM	#1
vinn Lurking Renovator Join Date: Jan 2015 Location: Montana Posts: 3 Thanks: 0 Thanked 0 Times in 0 Posts	Questions about starting small - 1kW We purchased our home 6 years ago and have been remodeling it. Since then, we've replaced all of the appliances with pretty efficient models. Our primary heat source is a wood burning stove. In other words, our energy use is ok - we're about 15000kW a year. The vast majority of that is in the winter because we use electric heat to supplement the wood stove. It's not ideal, but it's working Our furnace in the house isn't usable and would need to be replaced before even considering using it. If so, we'd replace it with a propane model (most likely). Anyway, the cost of all that would likely approach $8,000. I'd much rather invest that money into a PV system and just forget about the furnace altogether and keep doing something similar to what we have. Now, I'm fairly handy and I've even done some small off-grid solar installations in the past (for radio installations, etc). We live in a very rural area and the few people who work with PV here are in no way interested in even interested in this. They'd much rather try to sell me a $1000 survey that consists of a lot of things I've already done myself (NREL calculations, etc) and then sell me a $30,000 PV system. Also, we're a bit backwards where in rural Montana and everyone I've talked to has told me microinverters suck and to not use them - that raises a bit of a flag for me because everything I've read tells me that's exactly what I want. So here's what I want to do, someone tell me if this is a terrible idea: 1. Put in a very small system - 4 panels of Astronergy 305W with 4 Enphase M250 microinverters. I'm going to have a lot of hoops to jump through for the installation - namely, finding an electrician than can wire the grid-tie, getting the net metering set up with the local electric company, etc. I suspect it's going to take me longer than I think and I don't want 16 panels sitting around going unused for what might even be a year. I also want to learn how to do the mounting myself, so I'm going to start with small size. 2. Microinverters will let me expand later and I'd like to phase this system in over about 5 years. The Enphase M250 is new enough that it will likely still be available for purchase and I can match similar enough panels with it. 3. The other reason I want to phase this in is because I need to verify my mounting option is viable... the only place I have to mount these panels is a slightly tilted westerly (270 degree) angle. I'm sure that just raised a red flag, so here's the NREL calculations compared to optimal conditions (180 degrees): kWh / m^2 / day (yearly average): 180 degrees, 40 degree tilt: 4.73 270 degrees, 5 degree tile: 3.92 Ok, so my mounting option is only 83% as efficient as the optimal configuration. I can live with that. We're fairly sunny here, so hitting 4 kWh/m^2 is pretty good. 4. Eventually I'd like to build this out to about a 5kW system. I'm not in a rush, maybe it'll take a few years. I'm sort of betting that panel prices will come down and efficiencies will go up. Bad idea? Should I focus on something else?

01-11-15, 11:53 PM	#6
NiHaoMike Supreme EcoRenovator Join Date: Oct 2008 Location: Austin, TX Posts: 1,154 Thanks: 14 Thanked 257 Times in 241 Posts	If the main use is heating, it would probably make more sense to go with a solar thermal setup. Also look into DIY wind turbines. __________________ To my surprise, shortly after Naomi Wu gave me a bit of fame for making good use of solar power, Allie Moore got really jealous of her...

01-13-15, 06:01 AM	#7
stevehull Steve Hull Join Date: Dec 2012 Location: hilly, tree covered Arcadia, OK USA Posts: 826 Thanks: 241 Thanked 165 Times in 123 Posts	I agree with Mike on using other ways for heating. I have used PVwatts for calculations and being slightly off due south is only a 5% loss. But the BIG loss is your tilt with your almost flat roof. And the sun has a low angle in the winter so you would need to tilt them up. All that said, using electricity for winter heating is very inefficient as you can use those construction $ to buy/build a geothermal heat pump (GTHP). That would be where I would concentrate rather than PV to run electric resistance heaters. A GTHP can extract 4-5 times the amount of heat from the ground with one unit of electricity. In other words, you run the GTHP to leverage FAR more heat out of the ground so it is 400-500% efficient. Or another way to look at it is that your annual heating costs are 1/4 to 1/5 with GTHP compared to resistance heat. Not 20 to 25% less but 75 to 80% less. That is what I would do with your money rather than use PV panels to make electricity that is very inefficiently used as a resistance heater. Or get a propane heater and use the PV panels to decreasing your electricity consumption for lights, etc. A four panel system (1 kW) would do a LOT! Steve Steve __________________ consulting on geothermal heating/cooling & rational energy use since 1990 Last edited by stevehull; 01-13-15 at 06:06 AM..

01-13-15, 02:47 PM	#9
pinballlooking Super Moderator Join Date: Jun 2013 Location: SC Posts: 2,923 Thanks: 172 Thanked 564 Times in 463 Posts	I was going to start smaller and grow the solar array. But once I looked at the extra money and work needed to do it. I decided not to do go small. My electric company wants a $100 fee every time you make a change. (This really adds up) You have to have change docs and drawings each time you make a change. It has to be inspected every time you make a change. (Permit fees and inspections you need to be there for) I went with Enphase microinverters you need one Envoy for 1kW or 20kW or more. Panels are much cheaper by the pallet. 5 panels cost almost the same to ship as 20 panels. You would still need to put in large wiring in for where you wanted to be in the end. So wiring cost is the same if you go small or bigger. The racking is long and needs to be trucked shipped. All this cost adds up. Taxes would need to be done each year to get a tax credit. You get the point… I am not saying it can’t be done but just some things to think about. If you know a solar installer you can Maybe buy some stuff From A big job he had. You might be able to keep the cost down some. My array http://ecorenovator.org/forum/solar-...lar-array.html check out Where2 array it is closer to what you are looking at. http://ecorenovator.org/forum/solar-...tandard-3.html Last edited by pinballlooking; 01-13-15 at 09:25 PM..

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01-10-15, 05:14 PM	#2
where2 DIY Geek Join Date: Apr 2013 Location: Sunny Florida Posts: 401 Thanks: 74 Thanked 83 Times in 73 Posts	I'd say: Do it, and don't look back... (but I might be biased) The only part of the 4.4kW array on my roof that was farmed out for hire was the structural engineering to keep the array on the roof in a 3-second gust of 170mph (required by the local building department). I drew the three line electrical diagrams, I obtained the state certification on the system (basically a $250 charge to review my three line diagram to be sure the system design meets or exceeds NEC 2011), I pulled the structural and electrical permits, I did the install, I did the hookup to my service entrance panel, I passed all my in-progress and final inspections. I signed off with the power company and showed them my passing final electrical inspection to get the net meter installed. It's my house, and my building department is fine with owners doing modifications to their own home with proper permits as long as the work meets or exceeds the current local building codes. (must be owner occupied, cannot be rental property). You're probably thinking: Where2 must work for an electrical contractor or something? The answer is: ~sorta. I have a bachelor of science in Surveying and Mapping, and I'm a licensed professional surveyor & mapper in two states. At the moment, I work for a low voltage electrical contractor designing show control systems, audio & video systems for theme parks, cruise ships, and an occasional mega-yacht. The only part of working for the low voltage contractor that came in handy was having a copy of NEC 2008 around (since NEC 2011 wasn't a complete re-write). I use AutoCAD all day, so whipping together a three line diagram took a few evenings of my time (a good portion of the time was actually figuring out where the WEEB grounding clips belong, and showing how the whole racking system is grounded). If you have questions, feel free to ask. I'm already working on my design for PV system #2 for a property my wife and I recently bought at 45.8°N. Before we made an offer on the property, I went to the town office and asked what modifications to the building would require permits, and if anything was off-limits to home owners who pulled permits and had their work inspected. Now that I have one complete design drawn, #2 is going to be much easier! If you're thinking the enphase system is pretty simple, you would be correct. There are twenty M215's on my roof. I collected 17.8kWh today. I called one structural engineer (referred by a friend from college who is a local architect), the guy actually tried to talk me out of designing and installing my own PV system! Fortunately, I was able to locate a structural engineer I had previously used (he had since moved his family to Colorado when the economy tanked), who retained his license in FL and was more than willing to work with me and cash my check. The structural engineer I used now has a PV system on his own house outside Boulder, Colorado. I will say this: Item #3, that 270° facing roof with only a 5° tilt may be a bummer. How much snow do you get? A ground mount facing 180° with the proper tilt may justify the added expense of the ground mount. It also makes it easier to rake the snow off and get back into production in winter (or so I hear, it was 74°F at my house today). The property I'm designing PV system #2 for has a 100PSF ground snow load. I'm still debating if I want another 4 pounds per square foot (~solar array) on my roof in addition to the heaps of snow, especially if I'm not there to rake it. Ground mount with adjustable tilt is looking better and better. I just need to get it high enough to stay above the drifting snow banks! Last edited by where2; 01-10-15 at 05:21 PM..

01-10-15, 05:42 PM	#3
where2 DIY Geek Join Date: Apr 2013 Location: Sunny Florida Posts: 401 Thanks: 74 Thanked 83 Times in 73 Posts	I don't see an Astroenergy 305 on the Enphase compatibility list. http://enphase.com/global/files/Enph...ility_List.pdf The info I find on Wholesale Solar indicates the Astroenergy CHSM 6612P-305 is a 72 cell panel. Did you run the numbers from the spec sheet on the 305 to verify compatibility using this website: Module Compatibility Calculator - Enphase Energy I can certainly see where having an oversized PV module for a particular inverter when it's mounted at a less than ideal direction and tilt may work to your advantage. I've always been amazed that my 220W panels rarely approach 220W in my climate on my installation. My array is rotated 16°W of South, and not at a tilt optimized for my latitude.

01-11-15, 11:25 PM	#5
where2 DIY Geek Join Date: Apr 2013 Location: Sunny Florida Posts: 401 Thanks: 74 Thanked 83 Times in 73 Posts	If microinverters have issues, I expect I'll find them on the upper row of panels at the house in Florida. Looking through my historical graphs, the inverters on the upper row are running 136°F at mid-day in August. An identical inverter on the lower row of panels is running 123°F. I intentionally mounted the inverters along the rail closest to the edges of the array, in the event I had any issues. Heat is not the friend of electronics. The modularity of microinverters was one of the things that sold me on them. Initially, I wanted to do the sort of phased system you envision. In the end, the permitting hurdles and extra costs of doing a multi-phase install pushed me to delay my installation and wait until I could do it as one big job. I've got 528 days running days on my system to date. After 528 days, I'm averaging about 0.79kWh per day per panel. Although at first glance it looks like I have a spectacular view of the southern sky, I get random bits of shade from trees in the neighbors yards (and one of my avocado trees). At an average of 15.7kWh per day from my 4.4kW array, I still have an electric bill. I just don't give as much to the power company as I used to...

01-13-15, 09:22 PM	#10
where2 DIY Geek Join Date: Apr 2013 Location: Sunny Florida Posts: 401 Thanks: 74 Thanked 83 Times in 73 Posts	Thank you Pinball, I'd forgotten I had a link with the install photos floating around on ecorenovator.