Low cost Solar electric panels

News is news when it comes to solar and polysilicon:

http://www.bloomberg.com/news/2011-11-08/solar-shakeout-could-soon-reach-china.html


93% reduction in price. Hmmmmmm. How many trees can I cut down?

Hi,
If you use the micro-inverters (one per panel) like the Enphase ones, then losing a panel or two and replacing it with a different brand is something the micro-inverters take in stride. You can also add new panels later of a different brand if you want to expand the array.

Gary

BeGreen said:

GaryGary said:

Hi,
If you use the micro-inverters (one per panel) like the Enphase ones, then losing a panel or two and replacing it with a different brand is something the micro-inverters take in stride. You can also add new panels later of a different brand if you want to expand the array.

Gary

Click to expand...

We considered Enphase, but I am still skeptical about the longevity of a cheap inverter being placed on the back of a hot solar panel on a hot roof. The capacitors in them should have a lifespan of about 3-5 years. The only have been on the market for 3+ years now. How they stand up may be tough to determine. Enphase got pretty aggressive last year about suppressing further discussion on this topic. We are coming up on year 4 of this product being on the market. Years 5-7 will be interesting. Locally, I know of two Enphase failures, but they happened within the first year of operation.

http://peswiki.com/index.php/Talk:Directory:Micro-Inverter_System_by_Enphase_Energy
http://www.solardave.com/index.php/failure-rate-enphase-micro-inverters-video/
this is cached, they were made to pull it down: http://tinyurl.com/87hsphq
http://www.solartown.com/blog/2011/03/enphase-microinverter-warranty-claim-causes-heartburn/

Click to expand...

Hi,

I guess time will tell, but it seems like anytime a new product comes out there will be folks who think that it will have a fatal problem.

Back when bought our first Prius, there were well qualified very serious people saying that there was no way a battery pack could last anywhere near the life of the car an and to be ready for semi annual $5000 battery pack replacement bills. This seems a little comical now, but it nearly kept us from buying the car. Any new product will attract some people who just don't think it will work -- sometimes they are right

Bottom line is any new product has some risk, and you have to weigh that against the benefits.

I really have to differ with the last link that throws rocks at Enphase customer support. I have found their customer support to be exceptional. They always answer the phone, they know their product, and, it seems to me, they go the extra mile to make you happy. And, this is how they treated a home owner like me who they know is not going to be buying systems routinely. I've talked to others who have Enphase systems, and they feel the same way about the customer support. Its a bit ironic that the failure they were talking about was the EMU and not one of the inverters.

One aspect of the micro inverter approach is paying off for me. We are going to expand the size of our system (about double). With the micro inverters, I just add a new string of panels, and even though I can no longer get the same panels we did the first system with, its not a problem.

All that said, there are pros and cons to each approach, and both systems work well.

I just put up a couple new pages on my system:
How much do you save installing your own PV?: http://www.builditsolar.com/Projects/PV/EnphasePV/DIYSaving.htm
Update after two full years of operation: http://www.builditsolar.com/Projects/PV/EnphasePV/2YearUpdate.htm

Also had a fun time yesterday. It was the first test of using our ElecTrak tractor to power our home during power failures, AND to charge the ElecTrak battery pack from our grid-tied PV array. Worked like a champ.

Gary

So, to do grid tie you need to use certified installers in NY. What is the idea with DIY? You install the system, run DC in the house for whatever you can and then charge the batteries when you don't have enough sun with power from the utility? Or do you go off grid and then make up for the low periods with a generator? When I look at the solar analysis of my site, I would need some big damn batteries to store the power I generate in July to use in January?

SolarAndWood said:

So, to do grid tie you need to use certified installers in NY. What is the idea with DIY? You install the system, run DC in the house for whatever you can and then charge the batteries when you don't have enough sun with power from the utility? Or do you go off grid and then make up for the low periods with a generator? When I look at the solar analysis of my site, I would need some big damn batteries to store the power I generate in July to use in January?

Click to expand...

Hi,
My system is a regular grid-tie system. I did the install, but it was under a permit and inspected and signed off. The utility then installed a new net meter. So, its just like any professionally installed system. Montana (and I think most states) does not require a certified installer.
The installation is very straight forward if you have done much of any wiring before.
The system is described in mind numbing detail here: http://www.builditsolar.com/Projects/PV/EnphasePV/Main.htm

As you know, when there is a power outage, a regular grid tied system goes down and does not provide any power even if the sun is shining. The grid tie inverters test for the presence of the grid power all the time, and if its not there they shut down until the grid comes back. This is required to get the UL approval for a grid tied inverter. There are grid tied systems that provide battery backup during power outages, but they add a fair bit of cost, and you have to maintain a battery pack that just about wipes out any savings the system might generate.

What I am trying strictly for power outage emergencies is to basically rewire some of the PV modules in my grid tie system to drive a normal charge controller, which charges the batteries in my ElecTrack electric tractor. I've added a combination charger/inverter to the ElecTrack, so that we can get 120VAC power from the ElecTrack battery pack in power outages. The advantage of this over just getting a grid tie system with battery backup is that I don't have to maintain an expensive battery pack that is only used during very rare power outages. I can just use the pack in the ElecTrack. I use the ElecTrak for mowing, snowblowing, ...

For a power outage, the way the sequence goes is: 1) I throw the PV system AC disconnect (so the PV system is completely isolated from the grid), 2) I cover the PV panels with a tarp, 3) I rehook 6 of the panels into 2 strings of 3 panels, 4) I hook the two strings to an Xantrex MPPT 150 charge controller (which I bought just for this purpose) - at this point, the PV panels are charging the ElecTrak pack, 5) plug the inverter into the battery pack, and 6) run extension cords to key loads that we need during an emergency (fridge, ...). I figure this will give us about 5 KWH a day no matter how long the power outage goes -- 5 KWH is plenty for the stuff we really need. The ElecTrak battery pack is six 220AH Trojan 105's (just like a lot of golf carts).

This is all easier to do than it sounds -- partly because the panels are on the ground. The rehooking is quite fast because the MC4 connectors are easy to connect and disconnect. Basically the only cost over what I already had for the ElecTrack was the new Xantrex charge controller and some wire -- about $500 total. I do have to admit that part of the appeal was just to see if I could make it all work

If you want to see how addictive these ElecTraks can be, have a look at George's collection: http://www.myelec-traks.com/

---
On the other question about cost of the micro inverters. I've found the same higher prices when you buy only the inverter, but (at least at WholeSale Solar where I buy stuff), the equivalent packages with the micro inverters are actually a little less than the same package with the string inverter. Have no idea why this is true.

Gary

Off topic a bit
But Gary or others BeGreen with solar panels
Any plans to combine with Electric Car or Chevy Volt ?

Tom

macmaine said:

Off topic a bit
But Gary or others BeGreen with solar panels
Any plans to combine with Electric Car or Chevy Volt ?

Tom

Click to expand...

Hi Tom,
I'm thinking about the Prius Plugin Hybrid.

The 15 miles electric range is short, but it actually matches our run into town driving pretty well. The thing I like about it is that once you are off electric mode, the on gas mode is 49 mpg -- nearly as high as the regular Prius Hybrid. I'm told that the Volt all on gas mpg is 37 mpg, and I'd really like more than that. We do the trip into town (which could be all electric) on most days, but when you add up our end of year total miles driven its more than 2/3rds long highway trips (the grandkids are in CA). So, I think, the Prius Plugin would suit us pretty well.
It looks to me like the gov tax rebate will be available for some time after the plugin comes out, so I think we will be waiting to see how the first plugins do.

After I expand the PV array, it will be able to provide a lot of the juice for the Plugin.

Gary

I'd buy a plug in in a heartbeat if our electric rates weren't so high and net metered PV wasn't so high. Driving our hybrid is a gas and it would be that much better if we could generate the power for it.

Interesting times to have some choices other than going to the gas station

BG: I too worry about cold weather driving and may see how winter of 2011 changes attitudes
Gary great to have the juice waiting for the car!
Solar/Wood: Yea tough to justify electric fuel with electricity rates so high; the total cost of ownership (no oil changes, fuel pumps, etc etc ) is low due to the simple design of electric cars.

You all might like this link on contest for best slogans for electric cars

http://www.plugincars.com/one-liners-plug-vehicles-contest-results-110158.html


No Drilling no spilling no filling was the winner by Rich Evans


"
Rich Evans, a CPA from Pennsylvania, who (while then living in Florida) was a leading member of the Prius user discussion groups that came together to "unearth" and promote the fact that U.S. models of the 20004 Prius had an "EV mode" that could be enabled by simple wiring changes. CalCars published the manual for that (still found at http://www.calcars.org/priusplus.html), which led to the first experimenter adding additional batteries and then to the pioneering CalCars PRIUS+ conversion. (For that story, see and Sherry Boschert's book, Plug-In Hybrids: the Cars That Will Recharge America." Rich still drives his 2004 Prius with the EV Button."

Food for thought for any Prius owners who are electronic geeks to boot ie Gary

Tom

I'm starting to get curious about a grid-tied system. I'd prefer a ground-level installation so I could do it myself (and fix it) but any suitable spot is about 250' in any direction. I could put it in the middle of the lawn but there isn't full day sun without cutting down every tree and completely clear-cutting.

From what I can figure/guess the grid-tie panels run at a higher voltage, some up to 600V. This would definately help in my situation if I had to pull conduit 200'-300' away. 4/0 copper is about $5/foot!

Hi,
There is a wire size calculator here:
http://www.electrician2.com/calculators/vd_calculator_initial.html

The grid tie systems with string inverters do have fairly high voltages -- I think that around 300 V might be typical. I think that they are legally limited to 600V or less under the most adverse conditions (like a cold sunny day).

The micro-inverter systems would be sending 240VAC from the array to the house, which is also a pretty good voltage.

If you use 240 volts, 250 ft long for a 4000 watt system, the amperage would be about (4000/240) = 17 amps.
The calculator says that 8 gage wire would give you a 2.8% voltage drop, and 6 gage would get it below 2%.

For such a long run it might be worth looking at aluminum -- not sure what the price dif would be, but 4 gage alum would get you below 2% drop.

Gary

You will want to size your wires as large as you can justify. The voltage drop that you will see with smaller conductors will be costing you lost production when the system is operating at its peak performance. I believe that on SMA's website, they say to keep voltage drop to 1.5% or less.

Copper is definitely more expensive than aluminum, but it also will have a lower voltage drop and higher conductivity for the same size wire. Generally, if you need a certain size wire in copper, you will need the next size larger in aluminum to be able to handle the same amperage.

Aluminium is cheaper vs copper, but 2" conduit is a heck of a lot easier to run than 3" or even 4". It may make more sense to pay for copper if the conduit fill becomes an issue, but usually not when you're building from scratch. The same size aluminium is easier to pull than the same size copper. Lots of trade-offs. Also, you're equipment lugs must be rated for the conductor material. Often not an issue but still something to think about.

GaryGary said:

Hi,
There is a wire size calculator here:
http://www.electrician2.com/calculators/vd_calculator_initial.html

The grid tie systems with string inverters do have fairly high voltages -- I think that around 300 V might be typical. I think that they are legally limited to 600V or less under the most adverse conditions (like a cold sunny day).

The micro-inverter systems would be sending 240VAC from the array to the house, which is also a pretty good voltage.

If you use 240 volts, 250 ft long for a 4000 watt system, the amperage would be about (4000/240) = 17 amps.
The calculator says that 8 gage wire would give you a 2.8% voltage drop, and 6 gage would get it below 2%.

For such a long run it might be worth looking at aluminum -- not sure what the price dif would be, but 4 gage alum would get you below 2% drop.

Gary

Click to expand...

So, on this example, if you went from 8 gage to 6 gage it would take the voltage drop from 2.8% down to 1.8%.
This would give you about a 1% increase in energy generated.

A 4000 watt system will probably make about 6000KWH a year depending on where you are, so 1% of that would be 60 Kwh over one year -- worth about $6 at 10 cents a KWH. You could compare that to the extra cost of the 6 gage vs the 8 gage and see how many years the 6 gage would take to payback the extra initial cost.

If the power from the array to the house is transmitted as 240AC as it would be for the micro inverter system, it would arrive back at the net meter about 2 volts less with 8 gage than with 6 gage. I wonder if the meter is smart enough to pay you less for 238 volts vs 240 volts? That is, for the power you deliver to the grid, do you really gain anything for the larger gage on a micro inverter system? Anyone know?

I will say that I wish I had put in 1 gage heavier than I did on my system as I now want to expand it, and if I don't change out the wire from the array to the house, the voltage drop will be up toward 3% -- so, think about expansion.

Gary

A lot of times it will depend on the market at the time of install. I've seen a roll of MC rise/fall 50 bucks in a few months. You only have to install wire once.