Grid-tied solar

[Redneck in training]

Dan,
the key is DIY. Or at least most of it. Then get home low interest equity loan. We got 25k loan zero interest from from Iowa Alternative Revolving loan program. I think most states have similar program. Then we borrowed 30K at 5%. So together it is 3.7% on 55k. Iowa tax rebate is 30% or 3000 dollars whichever is less. I will say it again you have to have interconnection agreement before you spend you crusty hard earned money.

 

[dmccarty]

Dan,
the key is DIY. Or at least most of it. Then get home low interest equity loan. We got 25k loan zero interest from from Iowa Alternative Revolving loan program. I think most states have similar program. Then we borrowed 30K at 5%. So together it is 3.7% on 55k. Iowa tax rebate is 30% or 3000 dollars whichever is less. I will say it again you have to have interconnection agreement before you spend you crusty hard earned money.

What equity? We had some equity but we don't have much equity now according to the appraisals and the bank...

There could be a low interest loan but I can't afford a loan due to other bills. The only way I can swing this is if certain events go far better than expected, and towards the end of the year, to carry part of the loan for a few months. Even that is doubtfull and depends on certain things happening that are out of my control.

I don't think I can DIY from what I read in previous years and qualify for the NC refund. Getting the refund is a big part of the payback and at the present time we would be limited in getting the money back. Even if I could DIY, when do I find the time since I am already booked up? We are not burning wood right now because I did not have enough time to split wood that was ready for splitting...

I have no spare time or money...

Later,
Dan

 

[dmccarty]

I was able to sign up for the PC class starting tomorrow. I thought I had a conflict but I don't. Thankfully the class is nearby and only two hours each day so I can still have a chance of doing other chores before and after class. Sounded like if I did not sign up for the class, and today was the last day to sign up, the class would have been canceled. From reading up on the instructor, he seems like he will know what he is talking about.

Last night I pulled up a spreadsheet I did on PV two years ago. I was surprised it was from two years ago, and at the time, I figured PV cost was $8 a watt. I went back to some Internet sites and the prices sure have dropped as Ladia said. I have been tracking our power cost and usage since we moved into the house so last night I looked at the spreadsheet a bit more carefully. Basically we are using 41ish KWH a day on average. A 10,000 KWH system would just cover our average power use. If we put up a solar water heater we would have excess power but those heaters seem complicated...

Looking at the details of power company subsidy, it sure has some gotches. Looks like you have to sign up for a time of use tariff. :shocked: If I am reading it right, there are two time periods during the year and on peak power costs $5.02 or $3.73 a KWH!!!!!!!!!! :shocked::shocked::shocked: Our current cost is 10 CENTS per KWH. The company pays you $4.50 for each PV KWH but the time period they use for peak time includes after night fall so the cost/benefit analysis is just a wee bit complicated. One is locked into a five year period with this peak time tariff and the $1,000 per KWH has to be considered as well. Net metering is a bit odd as well, as the way I am reading it, any surplus production is given to the power company at the end of a period of time.

The class should cover these details, and if not, there are some NC state resources I know about.

One of the problem's with PV is that there are a huge number of suppliers. Which has the best quality, best price, best warranty and will the be around to honor the warranty?

While we do not have the time or money to do this today, if we did have time and money, the right time to install is at the end of the year so one only has to wait a short amount of time for tax season. Taking the class and doing the research now would allow us to install if we found the money and/or time. If it makes money sense and the prices now certainly seem to make money sense.

Later,
Dan

 

[dave1949]

We only have a net-metering arrangement here. I cannot "sell" power to the utility. It is very simple and has no effect on the rates, there are no contract periods, etc.

I have two meters, IN and OUT. At the end of the month the change on those two meters from the previous month-end readings are used to determine my net usage. If the IN is higher than the OUT, I pay for the difference on my electric bill. If the OUT is higher than the IN, I get a credit toward future usage--good up to one year later after which it is tossed out. A grid-tied net metering system here should always be sized to supply no more than you use over a year's time since you will receive no benefit for the excess production. You would end up giving free power to the utility.

In any case, I always pay the minimum $8.91 monthly connection fee which also includes my first 100 kWhs of service (delivery), but not generation, charge.

 

[dmccarty]

We only have a net-metering arrangement here. I cannot "sell" power to the utility. It is very simple and has no effect on the rates, there are no contract periods, etc.

I have two meters, IN and OUT. At the end of the month the change on those two meters from the previous month-end readings are used to determine my net usage. If the IN is higher than the OUT, I pay for the difference on my electric bill. If the OUT is higher than the IN, I get a credit toward future usage--good up to one year later after which it is tossed out. A grid-tied net metering system here should always be sized to supply no more than you use over a year's time since you will receive no benefit for the excess production. You would end up giving free power to the utility.

In any case, I always pay the minimum $8.91 monthly connection fee which also includes my first 100 kWhs of service (delivery), but not generation, charge.

It appears that the NC net metering is similar. I THINK/HOPE that surplus power is rolled forward until the end of the time period/year at which point the power company gets the surplus. And as you say, you don't want to over build the PV system because only the power company will reap the reward.

The contract was for getting the $1,000 per KWH subsidy. This was the confusing part because they would pay the $4.50 per KWH each month but then put one on the expensive time tarriff. I had never heard of such a think in NC. If one does not get the power company subsidy, then you would just use net metering. It appears that one can do both net metering and sign the contract for the power company subsidy.

Net metering seems to have changed for the better in NC. I thought once upon a time the NC power company paid the PV owner wholesale rates when they were producing excess power. Looks like it is now evened up.

Later,
Dan

 

[buckeyefarmer]

Dan,
let us know how the PV class goes. I would like to do solar next. I did my Geo as a DIY, after taking the accreditation class.

 

[dmccarty]

Dan,
let us know how the PV class goes. I would like to do solar next. I did my Geo as a DIY, after taking the accreditation class.

:laughing::laughing::laughing: Good timing! I just got back to this thread to mention the glass.

Figured I should just add my comments to this thread since we have been discussing the issues of PV.

The class is good. The teacher is an old guy, , who used to be a builder. My guess is that he retired to the teaching job. He built quite a few solar houses and was on the committee pushing renewable energy issues in NC. He seems to know what he is talking about though I asked some questions which surprisingly he did not have answers. He talked a bit about net metering and for NC, he was saying it was not worth the effort and cost. From my recent reading, my interpretation was that net metering in NC was know paying retail price for when one over produced. The teacher said that was not the case. The other issue was about the Time of Use Tariff and getting the power company subsidy. This subsidy pays a $1 a watt or $1,000 for a KWH of PV but you have to sign up for the tariff which looks like it charge $3-5 per KWH for the power one uses! The teach said to contact the NC Solar Center which I already knew to do. The NC Solar Center is a great resource in NC. It is up there with the NC Extension office. :thumbsup:

One of my unanswered questions was can a homeowner DIY project still get the NC state subsidy. I will have to ask the solar center.

The class only has 10-11 people in it and I was the second youngest and I am not a spring chicken. :laughing::laughing::laughing: The class is aimed at people who know little to nothing about PV. I know more than a little but the class already made the time and cost well worth it. :thumbsup: The people in the class are trying to learn the basics and at least two couples and one other person where looking at PV for a new home while another guy was interested in providing emergency power. One guy's church is looking to install PV and then there was me and another couple who were looking to install on an existing house.

The two big things that I learned yesterday was that the teacher REALLY likes microinverters and thinks they are the future of PV. I think he is right. I had not heard of these microinverters until Ladia mentioned them and I have been reading ever since. :laughing::laughing::laughing: The teacher mentioned Solar Bridge Our Solutions | SolarBridge Technologies and Enphase is the company I have been reading up on, Enphase Energy.

Apparently Solar Bridge is trying to team up with panel builders to package the microinverters on the panels. If this happens, Enphase better be very careful. On problem I see with PV, is figuring out which suppliers to use. There are a large number of panel makers and many of them are going to go out of business. Having a warranty of 20, 30, 30+ years does not do you much good if the company is gone. The Journal of Light Construction's Feb 2013 issue has a good article on PV installation's with microinverters. They used Enphase but did not mention the panel maker. I could just make out the name from one photo and Googled. They were using a panel from a Spanish maker and it looks like they are leaving the US market and I wonder if they are gong out of business...

One of my big questions has been about PV efficiency. I had read in a PV magazine that one lost 35% of the power produced on the panels by the time the power was at the AC outlets. That number just seemed very high and is a vast hidden cost to PV. The answer in yesterday's class was that the number was 77%. This was on a slide and we only saw the slides for a few minutes. Hopefully the teacher will pass out the Power Point presentation because the table that calculated the 77% number was interesting and I wonder if it applies to microinverter systems. The 77% value is used by default with the PCWatts calculator.

Other links that are interesting:

• PV-Tech Looks like it covers the PV industry.
• SolarIndustryMag.com: Solar Power News, Analysis and Renewable Energy Information This looks similar to PV-Tech and was mentioned by the teacher. He said you could get the paper magazine for free.
• https://enlighten.enphaseenergy.com/public_systems This is a VERY cool link. It allows you to see how much power is being generated by some Enphase installations. You can see when clouds pass over the installation due to the drop in power. :shocked::laughing::laughing::laughing:
• NREL: Renewable Resource Data Center - PVWatts We looked at this in class and I think it is what was mentioned early in this thread. This allows you to see PV potential of your specific site.

I am sure I learned more in the three hours class but these were the biggies. The class is really 2.5 hours but we went over by 30 minutes. :thumbsup::laughing::laughing::laughing:

Later,
Dan

 

[Redneck in training]

Enphase is also working with PV panel makers to embed the microinverter in the panel. The beauty of microinveters is high efficiency, redundancy and easy and safe DIY without being killed in the process or burn and/or damage the equipment. When the panels are illuminated they are ON unless covered. When you string them and the parallel the strings for single inverter there will be 300 - 400V and possibly 10 - 25 A. That is a lot of power when you touch it or short something. Microinverters work with about 30 V and about 8 A. The AC side is off until connected to the grid. So even though they increase cost about 10% they are way to go for DIY. They also offer better performance when some panels are shaded. The shade affects only the particular panel instead whole string.
I estimated the efficiency by measuring voltage and current when the inverters are maxed out at 215W each and it looks like the efficiency at peak power is rather better than 86% (perhaps closer to 90%) at the meter. The AC side losses about 9V at 79A so the peak loss is about 3.5%. The inverters are about 96% efficient (manufacturer claim) except full power when they limit output to 215 W . The AC loss will be proportionately smaller at lower power. I am currently out of home. I will do more precise measurement when I get home and will report what the results are.

 

[dmccarty]

Enphase is also working with PV panel makers to embed the microinverter in the panel.

That is good to know and I would have thought they would be trying to work with the panel companies. It just makes sense to gain market share.

If there are only two microinverter companies, they will likely thrive and stay around. I am more worried about the panels makers.

Measured my roof today to see how much area I have and it was as expected. Forgot to measure the slope while I was up there. DUH! It should be around 35% which is what I need for optimum solar gain. That was the design point and what was on the blue prints but I have never checked to see if they design matched what was built. It "looks" right but I need to check, though at this point it is what it is, but using PVWATTS would be a bit more accurate with the correct tilt.

On Edit. Just found out that Canadian Solar has a microinverter...

Later,
Dan

 

[aczlan]

Now, am I correct in thinking that the micro-inverters work by sensing power through their connection to the house and syncing to that. As such, if they dont detect power, they dont put out power?
As such, could they be connected to a subpanel (say the 100 amp panel in the barn) and provide power back to the house?
Also, would they work if (for example) I were to have the line going to them as one of the circuits powered by a backup generator?

Thanks

Aaron Z

 

[dmccarty]

Now, am I correct in thinking that the micro-inverters work by sensing power through their connection to the house and syncing to that. As such, if they dont detect power, they dont put out power?

Correct. Just like a single inverter, this is done to prevent back feeding the grid.

As such, could they be connected to a subpanel (say the 100 amp panel in the barn) and provide power back to the house?
Also, would they work if (for example) I were to have the line going to them as one of the circuits powered by a backup generator?

Thanks

Aaron Z

Those last two questions the wifey were discussing today but I don't know the answer.

Are you trying to figure out how to get the panels to provide power when the grid is down and the PV system is without batteries? I know I am. :laughing::laughing::laughing:

We are talking about the possibility of having enough battery backup to power the fridge, freezer, study and well pump. Those are our major concerns in a power outage and we could run the generator to recharge the batteries if the PV panels were not keeping up for some reason.

One of the nice things about the microinverters is being able to add a few PV panels at a time when you have money which is problematic with a single inverter.

Later,
Dan

 

[aczlan]

Those last two questions the wifey were discussing today but I don't know the answer.
Are you trying to figure out how to get the panels to provide power when the grid is down and the PV system is without batteries? I know I am. :laughing::laughing::laughing:

I am wondering if the power from a small inverter generator or the large UPS would be enough to fool the PV panels into thinking that power was on and let me have (for example) 5kw of solar to add to the 1600w genset. Would be a whole lot cheaper than fuel for a larger genset.
Another possibility would be to pickup a small diesel genset (was a 3KW one on Craigslist a few months back for $300 that would have been perfect)

Aaron Z

 

[Redneck in training]

Grid commutated inverters will not work with a generator or battery powered inverter. Reason being that they will try to push all available generated power to the grid. To do so they will increase voltage. If the "grid" is made by small generator and the demand is less than the PV generation they will increase voltage to about (262 V) and shutdown. I am not sure at this point how the shutdown is reset but I can speculate that you would have to turn the power completely off or they reset at night. They have also low voltage and high/low frequency shut off.
In other words they would work only if the battery or another type of storage (in example electric hot water tank) would be able to absorb all generated power.

 

[aczlan]

Thanks.

Aaron Z

 

[dmccarty]

Grid commutated inverters will not work with a generator or battery powered inverter. Reason being that they will try to push all available generated power to the grid. To do so they will increase voltage. If the "grid" is made by small generator and the demand is less than the PV generation they will increase voltage to about (262 V) and shutdown.....

In other words they would work only if the battery or another type of storage (in example electric hot water tank) would be able to absorb all generated power.

I was looking at batteries to provide some backup but them danged things really add to the cost and complexity of a system. It seems that trying to use batteries puts you back to using a large inverter to converted from the battery DC to AC.

Later,
Dan

 

[Redneck in training]

You can store energy as in example hot water in the winter or chilled water in the summer. The complicated part is the controller that would control the load (storage ) such a way that you would store only enough energy not to have an excess. That is what I am thinking about. I could install large no pressure tank in the garage and use excess generated energy to heat it in the winter and chill it in the summer. That could be interesting retirement project.

 

[aczlan]

That could be an option if we go with a water mass storage tank, just put in bungs to install several hot water heater heating elements and figure how to tell the system that if the voltage gets above (say) 124 volts per leg, turn on the heating elements. That could then be used to heat the mass storage tank and provide domestic hot water...

Aaron Z

 

[aczlan]

Perhaps something like Single Phase Monitor | Phase Monitor | ICM Controls could control a relay to either charge a battery bank or heat water when the line voltage is over a certain voltage.

Aaron Z

 

[Redneck in training]

power usage monitor that communicate with an electric meter - Google Search

Connected Home Manager, Energy Monitor | GE Nucleus

http://www.ekmmetering.com/?gclid=CIqk7Mmd9bUCFU566wodLk0A9Q

Google smart meter

 

[dave1949]

You don't want to over-think setting up a grid-tied solar system to be tricked into functioning when the grid power is out. It won't do anything during the night time hours which is 50% of the time on a yearly average, and if your power is out because it is stormy, you may not have that much sun to work with anyways.

If you must have power overnight, then you will need a generator in any case. Or, install an off-grid system with enough battery capacity. That will cost more than a generator, needs a dedicated battery area that doesn't get too hot or cold, and requires some maintenance. The hybrid grid-tied/off-grid systems with some minimal battery capacity are also expensive.

There is a KISS element to it.