My Solar Panel Power Project

[Lt CHEG]

Excellent project. I'm hoping to see more of these projects so that the unit prices will decrease. I don't think that I can justify the cost of one of these systems myself at this time but perhaps in the future. I'm thinking that when we start building our new place I will probably spend a little bit extra in the beginning to make it easier to add a PV system of some sort in the future rather than spending more to replace stuff later on. Honestly I'm more of a fan of wind power and prefer the looks of a windmill to the looks of a PV array, but after doing a little research in some books and on the internet my area is not particularly suited to wind power. Actually it looks like we'd be better off with PV as far as alternative energy is concerned but at this point in time, with us being as far north as we are the costs are just too high. I applaud you for taking underaking this project and I truly wish that more people would follow suit. If a lot more people undertook this sort of project and economies of scale kicked in, I might be able to justify a PV system if it was about 25% less.

 

[eepete]

Tom, glad your battery storage system is working for you. It is quite a task to figure out which way to go regarding mounts, tracking, number of panels, simplicity/reliability.

Lt., I hope the price comes down too. A big part of the problem is a lack of standard panel sizes between manufactures. They don't want to be generic and interchangeable, but that is what it takes to get the price down. The rail system could be a much better design, but I suspect the company in Utah that makes it can't afford a re-tool due to the volumes. The design they have takes a little more labor and thinking than I'd like. I do like that the silicon came from Japan but the mounts (aluminum and glass) are made in Tennessee and the mounts are made in Utah. Wire was all made in US, as was the DC combiner. At least the project has some US content, and maybee even an appropriate amount for a global economy.

The Fronious brand inverter I have is a top of the line, 96% efficient, unity power factor, and low harmonic distortion. But it has a common base for all the sizes from 2500 to 14000 KW. So there is a price to pay at the low end. If there was some clear high volume size (say the 2000 or 2500 watt system) the inverter could be tailored specifically to that size and it's cost would come down. I'd love to rip the skin of and look inside, but I don't want to void the warranty. That's an expensive but well thought out piece of equipment. It reminds me of what the U.S. used to be able to design.

There are some pieces missing regarding tying up the cables and the solar combiner. So anyway, with a mix of volume and smaller number of design sizes, and more standard mounts the price of the equipment and installation could come down.

We also need installers who won't just blindly double the cost of the hardware on all systems. If you've got $40K of hardware, maybee the markup could be "only" $15 for what the installer with no stock ordered. A lot of the installer base reminds me of the old home satellite days. Early installers had outrageous mark-ups. But with volume and competition, capitalism will deal with this. Many installed prices did not come down when the tax credits came along. Short term greed holds back long term progress.

One thing I found about wind systems is many are not very good with lightning. The one I looked at was made in some part of the west where there were few thunder storms. A small wind turbine design needs some sort of big post/shaft coming through it that the lightning can hit without taking out the unit.

Pete

 

[sodamo]

Great series of articles Pete and a really great project. Super job on the explanations and pics. I am a tad envious of your capacity versus cost.

We live totally off grid. Our system is also 36 panels at 125 watts each - 4.5 kw. These are arranged in 9, 4 panel arrays, roof mounted at fixed angle/orientation. Last year our system produced an average of 14.8kw per day, but that ranged from a low of 1.1kw to 27.5 kw. On the low days we had to supplement with our diesel generator - for a total of 310.4 hours. We have a 48 volt battery bank of Rolls Surettes (1350ah) and Outback FX3048 Inverters and MX60 charge controllers.

System ran about $60K installed, but that was 4 years ago. That cost doesn't account for my labor contribution. PV prices have come down a lot and I think tax incentives are better. We went off grid solar as there really was no cost effective alternative. I wasted almost the cost of 2 PV panels on a small wind generator on another (smaller) system on the property. We do have a small year round stream that teases my thinking about hydro, but it would be a major effort. To have hooked to the grid would have involved easements to run the poles and lines and besides not being cheap would have just bought me an ever increasing electric bill for the rest of my life.

Our house (4000sf) is "normal" electrically - standard sears appliances, plasma TV's, beer tap in addition to other refrigeration, and I run power tools. We also have a swimming pool. We do NOT have A/C or any HVAC for that matter. That said, we do live a bit differently in electrical usage than in our connected days. Example, would probably not run dishwasher, washing machine, or other high usage items at night unless generator happened to be running. In other words, more electrical intensive options are used on sunny days. Our usage was about 600kw per month last year. What that would translate into grid $$,I don't know, but grid power is very expensive here in Hawaii. I do know that we don't suffer outages in storms etc.

While it has been a learning experience, we are very happy with our system and glad we have it.

Perhaps in your future posts you'll write more about your monitoring system. As for me, every morning I walk out to my setup, record the numbers, then enter into a spreadsheet - not very high tech, but within my budget.

Thanks again for sharing.

 

[eepete]

David, thanks for the information on your off grid battery system!

In addition to the changing prices on the panels, adding the batteries and generator definitely ups the costs, but as you point point when there is no economical alternative what can you do? Living off grid in an area where there is no need for HVAC sounds pretty nice.

I had about 2500 pounds of batteries that I got used that ran a repeater site I used to have. The life of those NiCads was about 16 years. Can't remember the amp hour rating.

I'm fired up to get something going on logging energy usage, I'll post as it happens but it might be a while.

Pete

 

[seca111]

I've thought about this alot lately, my biggest hang ups, is my utility is a COOP so they offer no incentives, so I just have the Fed ones. They are still alot but its frustrating that if I was 20 miles to the north, I'd recoop alot more.

One thing I've always thought about is I like the grid tie in system idea, however we loose power a few times of the year due to heavy spring snow.
my understanding is for lineman safety they have to be wired such that if the incoming feed from the grid goes down, that your system shuts down also so you are not feeding watts back down the line. Is that correct? I think I'd be very frustrated if I had a Solar set up, its sunny outside, and I'm still without power because of a line break miles away.

I can't believe there isn't some kind of switch that would switch to a local circuit only (not feeding down the grid) if the incoming drops. that way you could still use the power you are making, and when the incoming feed came back up it would sense this and reconnect the outgoing.

 

[eepete]

When NC got a net metering law, and a target goal for some percent of green energy, things changed. North Carolina also has a tax credit for installing lots of energy stuff, so that plus the Feds makes it possible.

With a grid tie system, the inverter shuts down if there is no commercial mains. It has to in order to get the required UL listing. That's fine, good feature, safety first.

I would love to have a way to tell the inverter that "I'm on my own". I am guessing that the problem is how to co-ordinate that with a mechanical switch (or electro-mechanical switch) so that you can not backfeed the grid.

There is also the problem of what happens when the power output of the array goes down? Do you risk damaging your compressor? How do you manage your load in a changing supply environment?

So I think what you want is doable, but suspect that the additional cost of some sort of inverter-controled electromechanical transfer switch would be a big expense in a low volume market. The low volume would come from the varying output of the cells during the day. You'd have to be a pretty savvy user to work with that.

For what it's worth, I did not connect the PV system after my transfer switch (on the same side as the generator). I'm pretty sure it wants to "push around" the grid and counts on that being an "immovable object". If the inverter was "pushing around" the generator, I think things would be unstable. The inverter has some pretty stringent requirements regarding the AC line frequency, and might also be unhappy if the frequency changed a bit on the generator as more load (like a heat pump kicking on) was added. It would be interesting to know if anyone has tried this, but I don't want to be the test case due to the cost of all the stuff I could blow up :laughing:.

Pete

 

[BillG_in_TX]

Pete,

That's a nice setup you have there. I have a 4.6 kW array on my roof that was installed in May of 2009. I used microinverters from Enphase that constantly report production to a control box in the house, which in turn is connected via the internets to the mother ship in California. You can see my installation here. My array faces SE and they are installed at a 26 degree pitch. I found this chart online which indicates that I'm not losing a lot compared to the optimum orientation (S) and tilt (33 deg).

The microinverters convert DC to AC at the panel, which eliminates high voltage DC runs through my attic. The system is described here. There are advantages and disadvantages to the system, and I'm not sure I would use the microinverters again if I was deciding today, but it does give you all of the instant feedback and history you could ever want - down to the individual panel.

My system had a gross cost of about $7.00/watt ($32k) and a net cost after electric company rebates and federal tax credits of about $2.50/watt ($11.5k). In the first year, the system generated about 17kWh/day and I used about 10.5 of that and pushed the other 6.5 out to the grid. I pay about .09/kWh for incoming and sell my excess for about .065/kWh.

Even with all of the incentives, if electricity prices don't rise it will take about 20 years to break even. However, I don't think it's necessary to recoup all the costs with electricity savings, since the system probably added about $10k to the value of the house. That's based on annual operating cost savings of at least $500 times 20. I don't know if that's actually backed up with empirical evidence, or if it's just a marketing ploy, but I do think it does add value to the house, like high efficiency replacement windows would.

 

[eepete]

Nice setup bill :thumbsup:.

With my open field, the micro inverter approach is not as beneficial as residential with trees that might shade part of the array. I'm not smart enough to know which system (single inverter vs. micro inverters) will win or even if there will be a winner. The reliability and aging characteristics of the panels will determine if per-pannel information is worth the cost.

I found a site that did an annual output vs. tilt angle, so even though I'm at a 36 degree latitude, my array is at 30 degrees. This maxed out the annual production (for a fixed angle array).

The Enphase stuff is pretty nice. I wanted a more open system, and all the stuff I'm working on for monitoring will be open. I see a lot of the energy aspects of a house tying into the home automation parts. The ability for the user (or a systems integrator) to select what is graphed and monitored might find some interesting thing that would be missed with a more targeted (albeit nicer looking) approach.

Tnx for your cost numbers too. The "dollar a watt" dream point of pricing is a ways off, and I suspect that increases in electric costs and billing structures might push that to $2/watt as the point where things are more viable. If you're going to be an early adopter, you are also taking some risks with the economic side.

As for what value does PV add to your home, in time it will be like a heat pump or furnace. You have infrastructure in your home (wiring, meters, support structures) and it is understood that you change out the guts (panels and inverters) every 20 years or so.

Pete

 

[BillG_in_TX]

Pete,

I see where Enphase is now offering a thermostat that is connected wirelessly to the Envoy. You can control your thermostat by logging in to your Enlighten web page. At $350 each (I would need two) plus monthly monitoring fees, I'll pass for now.

I have a "smartmeter", which measures incoming and outgoing energy and communicates with the transmission company's computers for remote monitoring and billing. I'm guessing you have a similar or identical meter? In Texas, we have a portal where you can monitor your incoming electricity in 15 minute increments. You can also add up to 5 HAN (Home Are Network) devices to your smartmeter account. I'm not sure about the capabilities of this site, i.e. whether you can control those HAN devices, or just monitor them. This sounds like the type of program that you are looking into for your installation, yes?

 

[eepete]

That's the same Landis+Gyr meter I have. Too bad it's made in Mexico and not back in Lafayette, IN anymore .

It is read via RF on the power lines. No portal, that's OK. I have two CTs on the lines to the inverter, that's how I'll measure the output power. I have 8 CTs on my breaker boxes to measure power I've used.

The $350 thermostats are OK. The problem in a very general sense is that by the time a house has all these various gadgets, the time to maintain them all is high and the interoperability is low. So reduce it all to simple sensors, web based or app based displays (like a program that runs on you Apple platform), and a single machine to run it all.

The incremental pain of running all these single purpose devices can soon outweigh the individual advantages. Well, the PV array is another step to figuring all this out.

The new meters with Zigbee/2.4GHz RF interfaces will also be interesting. It will let people read how much power they have used without having to retro fit CTs into their wiring. This is how Google does it's power monitoring service. There are just too many things going on in this area at once. Something goods got to emerge from it.

Pete