My Solar Panel Power Project

[Rob-D]

Pete,
Nice set up and great documentation! A couple of things some folks might not know. First, panels are rated for 20 or 25 years but in truth they put out useable power for two to three times that. It does drop but not more than 10 to 20 percent. The point is you still keep getting a benefit and there are 50 year old panel still putting out power.

The tracking debate is an interesting one. I want to build a tracker for my panels but right now I'm happy to have them supplying power. I like panels on the ground even in my northern location. You get to site them exactly south, they're easy to clean the snow off and when it comes time for a new roof you're not dealing with panel removal.

Right now I'm running only eight 175 watt panels 48 volts into two Outback 3648 inverters. One runs everything and the other kicks in when it's needed. I'm on a coop grid here, incentives are low so I'm not intertie. I have Rolls batts coming off and MX60 with another one dedicated for my homemade windmills and probably another for my microhydro power that I'm also developing. I want the microhydro to help with the heat in the winter so things will be on a dump load with blowers after the batts reach 100% charge.

Great to see people putting systems together and as fuel prices rise payback time drops.

I just saw in one of my trade magazines that a company has just developed a see through glass solar panel. Also, there's a lot of design work going into high efficiency power circuits and chips. Thanks to the MOSFET we're all getting 95+ % efficiency in our pure sine inverters today. I remember 25 years ago a 1500 watt mod sine inverter cost 5k and was the size of a large suitcase. Things have sure changed, my Outbacks are a thing of beauty!

Rob

 

[eepete]

I wish I could still edit the post, that must time out after some amount of time. Was also kicked by pasting in the descriptions, the single quote kicks in some sort of font change under the "right" (really wrong) circumstances.

OK on the life. in 50 years I'll be at zero percent output with slight fertilizer residual value :laughing:. The typical longer life you mention does suggest that roof mount systems might collide with roof replacement down the road. I have a metal roof, so nothing is going up on that (it has a 50 year life in theory). I do plan on covering the wires as they run between the panels with black nylon spiral wrap so that the wires will last as long as the aluminum, glass, and silicon. That will probably be a change every 10 years based on other places I've done that (such as the indoor thermostat wire that the HVAC guy used outside at the old house).

The Fronious inverter has 3 stages that can be kicked in, so the efficiency is across the entire operating range. High power, high voltage P channel MOSFETs sure do help. I'd love to take the skin off and look, but don't want to risk wrecking the inverter or warranty. I got the 10KW inverter so I could take the DC array up to 10 KW if I wanted to. Will probably be limited by if I can get the same size panels or not. If not, I'll have to take it all apart and intermix the "new" panels into the existing strings. But that's a problem for another day after the financial dust has settled and I have a better feel for performance.

Your system sounds great, too bad the incentives aren't there for grid tie. Batteries definitely up the cost a bit.

Pete

 

[Rob-D]

Your system sounds great, too bad the incentives aren't there for grid tie. Batteries definitely up the cost a bit.

Pete

The up side is that I own it. We get power failures here throughout the winter and that's when it shines. Also I'm planning on an electric car that will charge from my system. I'm not jumping into the first phase of electrics coming out now. My hats off to those folks who get the ball rolling but the second generation will be much better and cheaper.

The nice thing about the Outback system is that I can hook anything I want to it from my own windmills to microhydro, all I have to do is tie in another Mx60 charge controller.
What I'm doing now is working to get my power usage down as much as possible. I'm starting to go to laptops for almost everything now even running my small CNC lathes. My range is gas and I have oil hot water which sips fuel although I want to go to on demand hot water.

The other thing I built into the house was radiant floor heat that runs my boiler at 110 degrees. I'll be tying electric elements into it that run off my stream to reduce my oil consumption. Land is power!

Rob

 

[saltman]

Wow, what a system. I Have an off grid 1,700 square foot home with 9- 215 watt panels and make twice as much power than I will ever need.

Why so many panels? What are you running there a 10 ton AC unit?

Your like the Jay Leno of home owners with all those panels.

My system can make all the power I need here in Southern CA in about 3- hours of full sun. I just finished it in May but anticipate the winter will be the same since I will not be running my ceiling fans.

You obviously have a handle on Solar and I appears yours is about buy back where mine is just about making power for myself.

Everyone has their objectives, but I think if people get their electrical use in order first and then look at what they really need to run an efficient home then Solar would be much more appealing.

No way would the power company here buy back very much power. They only encourage solar because they are forced to but they do it in a discouraging way if that makes any sense. They are all about making big money and selling power not trying to use alternative energy.

Having said that I run everything a normal house would have, Full size Kenmore Fridge, 52 inch flat screen, LG Washer and Dryer, just no AC.

Great System!

 

[Inland NW]

I used to live in Southern California. I put 30 PV panels on my roof at an intial cost of around 45K. The company that installed them projected my ROI at 10 years. I got a refund from the utility (SCE distributed the refund) of 11k making my out of pocket 34k. You can spend more for an "islanded" system that can run without your intertie to the utility but I did not choose this option due to increased cost and ROI. There is a switch in the inverter that senses a hot line, if that switch does not sense a hot line (power outage) the inverter cannot send the converted DC to your AC panel. This is a safety feature to protect line workers (no back feed). My experience was that the real hot days were not the best for generating power because the PV panels lose efficiency in the heat. February was the best month for generating on PV panels due to relative low ambient temps and sunny days. Shortly before I sold my home and moved to Spokane Washington, California changed the net metering laws and I would have started making money for the excess I generated, but did not use. Charges were.12/KWH(Tier 1) to .28/KWH(Tier 5) in Ca when I left. I liked knowing that I was a little more self sufficient and felt less guilty when running my AC during the dog days of Summer. Now I am in Spokane Washington and my home is served by a Rural Cooperative. Due to the lower cost of electricity and no incentives, PV solar panels are not even a consideration. Reading this thread sure made me miss my PV panels.

 

[BillG_in_TX]

Inland,

How much value do you think you recovered on that installation when you sold your house?

 

[Inland NW]

I would say that the solar panels were a definite selling feature for my house. My realtor seemed to think we could get more for the house due to the PV solar panels. I ended up getting within 10k of my asking price, but it is all a matter of opinion if I made my money back or not. I did manage to make money on my house which I first purchased in 1999 and sold in 2010. Then you start adding up all the improvements you made to the home and you start to realize maybe you didn't make as much as you thought you did. Long story short I came to Spokane and put down a large down payment on my home here. I have 10 acres of treed land, no neighbors in site(from my house), and it only takes about 25 minutes to get to work. So far I think I have made a good move. If I had to sit down and crunch the numbers maybe I didn't make my money back, but my quality of life has improved dramatically.

 

[Inland NW]

Maybe I went off on a tangent in previous post. You asked how much value I recovered.... I had the PV solar panels installed in the Summer of 2008 and sold my house in April 2010. In roughly 2 years I did not pay for electricity, but never received any credit for the excess I generated. If my ROI was 10 years as the company predicted then I should have received $3,400/yr in value in those two years. I am not sure that I would have paid that much for electricity in two years, but the way prices were going on electricity in California it probably would have been close.

 

[eepete]

Why so many panels? What are you running there a 10 ton AC unit?

Having said that I run everything a normal house would have, Full size Kenmore Fridge, 52 inch flat screen, LG Washer and Dryer, just no AC.

It's all about the HVAC. The weather extremes in San Diego vs. North Carolina is the difference. We're having a record number of days over 90 this year. You're close on the tonnage, I have a 5 ton and two 3 tons. But they all run at half speed and are all geothermal. They account for about 60 percent of our power usage. From May to September, the geothermal units make all the hot water we need when we're cooling. They help al little bit the rest of the time, mostly they can maintain temperature once it's been reached using the electric heaters in the hot water heaters. The hot water heaters run the most during the spring and fall when there is little HVAC activity. But this is all the stuff I want to monitor and look at.

The inverter is a 10KW, so if I wanted to add 12 more panels I could max it out. But that would cost about $10K to do that, so I'll wait until I have more data on how it's all working.

Pete

 

[BillG_in_TX]

I think if people get their electrical use in order first and then look at what they really need to run an efficient home then Solar would be much more appealing.

Saltman,

I agree with your premise, and I know from reading his posts that Pete is on board, too, but not everyone can live in beautiful SoCal and not need heating and AC to survive. My parents grew up in Beaumont TX without AC, but they both said they don't know how they did it.

We bought our 1970's era 3500 sf home in early 2007, and the previous owners had averaged 3100 kWh per month in the year before we bought the house. That actually killed the deal for me, despite my wife's love affair with the house, and we backed out of the contract during the inspection period. However, the sellers came back with some cash for energy upgrades and lowered the asking price, and we finally did close on the property. We're very happy in the house now, although bringing a 35 year old house up to today's energy efficient standards is nearly impossible.

We immediately replaced one of the HVAC systems that was original to the house, added six inches of insulation, and did a few more things to make the house "tighter". We also replaced an old water heater with a new tankless electric model. Our first year in the house, we averaged 1630 kWh per month - a reduction of 47%. The second year, we replaced 24 single pane windows with Energy Star rated windows and reduced our electricity usage to 1380 kWh per month. At the beginning of our third year, we added the solar PV system and that has reduced our monthly average to a net 900 kWh.

That may be as low as we can go, realistically. Some months our net demand has been as low as 250 kWh, but in the summertime, the AC and the pool pump kicks it up to about 1800 kWh. I can live with that, especially considering the alternative when it's 105 outside (and that's NOT a "dry" heat). Congratulations to both you and Pete on your design efficiencies.

 

[Rob-D]

I agree 100% Saltman!

Get your power down. People want to run Chicago on a solar system. Leaving lights on, etc. Clean up your electric usage, all CFLs, efficient thermostats, etc.

Rob

 

[eepete]

Started this house in Dec 2005, finished in Oct 2007. I did the AC wiring, that was in Oct 2006. I put in a lot of can lights with the air tight trim kit. Then put CFLs in them. Only the 13 watt (60 watt equivalent) work. The larger sizes overheat and the case turns brown. Can lights have all the heat up high with the electronics. While there are differences in brands, it's basically a problem. LED lighting will have the same problem. As long as the light comes out the bottom and the electronics are in the top, the can light is a problem. I just had bad timing on the can lights, if I were doing it again every room would have a few sconces in them.

I did put in a number of sconces for bathroom mirror lights and also in locations where they would be on a lot such as halls and up high in the TV room. The bulbs are either "upright" (bulb up, electronics down) or horizontal. There, CFLs work great. So there is a big gap right now in fixture design and bulbs with electronics. I did have to change out the 12 bulbs in the kitchen from 23W CFLs to 60W Halogens. The kitchen/great room is where the window budget was blown, so we don't use them in the summer but do for dinner in the winter.

The key will be lights with electronics that let you remove the trim kit for a 5" can and put some thing in there. You might need to put a hole in the can to get a vent for cooling. I've seen a LED product for can lights like this, and at some point I'll check it out.

Home is set up for per-room HVAC control, as automation progresses that will happen. House has foam insulation (Selection 500), conditioned attic spaces, metal roof, 12 percent fenestration ratio, four foot overhangs and square sides with good compass orientation.

I've got two 40 amp 1000 to 1 CTs on the solar panels. I suspect that only one is needed since the currents _should_ be the same, that's all part of the learning curve. That's the first picture.
I've got 200 amp CTs on each leg of my breaker boxes, I'll have to make more of these PCBs to get that going so I can measure the power use in the house.

Tonight I just finished firing up a new cut of a PCB that does true RMS to DC conversion for the CTs. That's the second picture. 1 volt RMS in yields 4 volts DC out, true RMS, crest factor of about 3, frequency response good to over 1 KHz. Core part is a Linear Technology LTC1966. The PCB has 3 converters on it, they come out on a CAT5 which also has input power of 6-18 volts DC. With 12 volts for power, the board draws 5 mA including the LED.

All the wires have been run from the solar array to the house, all CAT5, connectors on. Tomorrow I should finally be able to take some readings .

This is right up there with trying out a new implement for your tractor....:laughing:

Pete

 

[Redneck in training]

Costs:

Cells, rails, hardware: 31,700
10 KW inverter: 5900
Wire, conduit, panels: 565
Shed: 1000 (need to go through invoices and get that nailed down better, lots of Lowes trips....
Concrete & labor: 450 (I hired a local group to help with labor- a good idea)

Total: $ 39,615

After Fed and State tax credits, it should be about $20K. I'm not including my labor.

I have a contract to buy $1669 worth of power each year, which in the narrowest sense of "payback" means 12 years. The system has a 20 year life, where that means it outputs 90% of it's original capacity.

Most discussions of payback have subtle biases built in. I'll bet very few tractor owners can come up with a payback time for their equipment. So payback times tend to be things people manipulate to justify what they wanted in the first place. Seems unlikely I'm that objective and an exception to the rule.

Things that modify the payback time are:
Future cost of electricity and if a time of use billing goes into effect.
Cost of lost opportunity of money (think "If I had left that money in a money market or bond fund, would I be better off in 20 years?")
Is your labor really free? Cost of lost opportunity for my time.

So if power cost don't increase, and interest rates or bond rates go back up into the 5-7 percent range, I should have kept my money. If this area went to a 30 cents per KWH time of day use (like some parts of California) and the interest rates and bond rates stay below 2.5%, I look like a genius with a 6 year payback and making about $2700 per year or so.

If you look at this from a strictly economic point of view, you can't justify it. But by the same stringent rules, I couldn't justify my tractors (vs. hiring the big jobs out). At this point in the solar game, people playing have justifications beyond the simple economics.

As for the tracking system and panel angle, this fixed array is certainly the simplest thing to do in terms of moving cost and semi-anual maintenance. It is probably representative of what you would see in a residential environment. Which leads me to part of the why:

I was ready to launch a home automation product in 2009 that is best for new residential construction in the 3000 to 6000 sq foot home size. Yeah, I can call them all right :laughing:. But there are lots of people spending $10K to $100K on solar panels. With no new software or sensors, I can monitor all that stuff so they can look at their energy use and generation from the house or office. And then after that there's a "Oh yeah, it also does home automation too" moment. So this will let me learn all about this sort of thing and help me start up a new business.

In my county in NC alone there are 46 small PV installations, and over 330 in the state. Another part of "why" is because it is an interesting project and I enjoyed doing it. Being an early adopter is usually tricky and expensive. I know people who paid $5K in 1985 (or about $15K in todays dollars) to by a IBM PC with a _full_ 620K (or so) so they could type letters and write programs. I spent $2K in 1983 for an 8 Mbyte hard drive for my home computer I built. I spent $2.5K in 1971 for a used PDP-8 computer. All that paid of handsomely as time marched on. If I had waited for computers to become economically viable, the catch up game on the technology would have been too much.

I mentioned at the start of this post about biases, I want mine to be clear and fully admit that on economics alone, solar PV is not there.

I'm going to do about 3 posts next with a thought on solar PV power. A heads up to the monitors of the site, if it's too off topic or deemed political nuke it and there will be no hard feelings. I think there are some interesting aspects to solar PV down the road that are worth thinking about. Lets NOT have a thread about global warming, energy tax subsides, and the like. Those have been beaten to death already. I'm just trying to explain what I did, give some of my thoughts as to why I did it, and then get people to think about what (if any) role solar PV might have for the U.S.

Pete

What justification? People by Porsches when Yaris would do. I rest my case.

 

[saltman]

Yes I will admit SD County has weather that will permit low power use and still enable you to be in comfort but I am about 70 miles east of the ocean so it does get warm in the summer and cool in the winter. Nothing like NC or Texas but we do have four seasons at 3,300 feet that far from the Ocean.

I had the house built with a 30 foot roof, used metal reflective roofing and R-30 in the attic, 2x6 walls with r-19. The house stays cool once it's cooled and I suspect ( just finished in May) that it will stay warm as well once warmed.

Our climate allows me to open all the windows at night, which get's it down to 70 or so at night and then I close it up during the day and maintain the 20 degree difference during the day. M

 

[saltman]

Sorry, I got carried away and then posted before I was done. What I was trying to say is yes my climate is ideal for low power use and solar but most climates could use solar if they built the home efficiently and conserved.

In California people have no clue and try to run hot tubs, ac units, and track lighting with Solar, then think they are saving the planet because they are only using 1200kwh a month!

 

[Rob-D]

Sorry, I got carried away and then posted before I was done. What I was trying to say is yes my climate is ideal for low power use and solar but most climates could use solar if they built the home efficiently and conserved.

In California people have no clue and try to run hot tubs, ac units, and track lighting with Solar, then think they are saving the planet because they are only using 1200kwh a month!

I saw this clip with the actor Larry Hagman bragging about how his yearly bill is only 12 bucks or something. His solar system costs 750 grand with about half of it covered by incentives. What?? Someone shake this guy to see if he's breathing!

Rob

 

[eepete]

Update:

I have a months worth of solar panel data. We've made 1.8 MegaWatt hours of power, worth about $200 :dance1:. The panels provides about 47% of the power the house needs, with that percentage getting larger as we head into cooler weather. At that 47% level, our electric bill is more than cut in half (get more $ for power we make than $ we pay on a per KWH basis).


Still waiting for a net-zero day...

Pete

 

[sodamo]

Awesome!!!!!!!

 

[Loren49]

I just found this thread - interesting projects - we each have an opinion on what is a conservative setup vs what is extravagant. I've had a standalone system since 1982 in northern NY. (about 50 miles south of Canada) Used to rely more on wind but for the past 15 years mostly solar. I have 10 panels @ 85 watts and store in lead acid batteries. (1200 amp-hr) I have found that having the panels in a vertical position over the winter months is much more useful. With the amount of snow we get (and freezing rain/sleet) it simplifies life. The noon sun is low enough in the sky that there is little decrease in output. My home is a distance from the grid so I went standalone.

Loren

 

[Rob-D]

I just found this thread - interesting projects - we each have an opinion on what is a conservative setup vs what is extravagant. I've had a standalone system since 1982 in northern NY. (about 50 miles south of Canada) Used to rely more on wind but for the past 15 years mostly solar. I have 10 panels @ 85 watts and store in lead acid batteries. (1200 amp-hr) I have found that having the panels in a vertical position over the winter months is much more useful. With the amount of snow we get (and freezing rain/sleet) it simplifies life. The noon sun is low enough in the sky that there is little decrease in output. My home is a distance from the grid so I went standalone.

Loren

Loren, I'm south of you at about the 42 lat here and I set my panels on homemade supports. The angle I used is around 23 degrees, pretty verticle. I set them for optimum winter power. These panels put out about 1400 watts but more panels to come along with a couple of windmills in the front field and a small hydro.

Pete, impressive!

Rob