solar PV energy

[PG1995]

Hi

Q1:
I got hold of an electricity bill of a consumer and need your help with this query.

Q2:
I see that more and more people are using solar PV energy. It means that the grid is gradually getting closer to zero net energy consumption. I believe that electric utilities such as SMUD wouldn't have any problem with this because it is a publicly owned utility but I don't think PG&E will be very happy with this because, naturally, such utilities always aim for profits. By producing more and more energy, you are aiming for zero net energy and therefore you are simply using the utility's infrastructure for your own benefit and this doesn't really profit the utility.

Could you please tell me that what benefits utilities such as PG&E drive from encouraging consumers to install photovoltaic panels? Someone was telling me that most of profit for many utilities come from industrial and commercial sectors and therefore encouraging residential consumers to install PVs would let the utilities to generate electricity at cost-effective rates during high-demands hours, i.e. during the daytime. Thank you.

Regards
PG

 

[gary350]

Here in Arizona the electric power company started charging customers a $50 fee for having Solar panels. The power company claims it costs them money to buy the excess power, they have to pay employees to deal with this, it is not free. Solar companies here will install the solar panels on your house FREE. Your roof is a place for the solar company to keep their panels. To make a long story short solar companies make it sound good to the customer but in the end the customer does not get much out of this deal. So now with the power company charging a $5o fee I know 3 people that have changed their mind about having solar on their roof.

I bought 9 small panels on my own 135 watts set up to power lights only after dark. If I save $5 a month it will take about 9 years to break even. Solar electric are not as efficient at solar hot water panels. You get 200 BTUs per sq ft of heat from the sun. NO way you can get close to 200 BTUs with electric panels.

Solar City offered to put FREE solar panels on my roof, 7600 watts of panels. Solar city gets the government rebate, they get all the electricity $$$ the power company buys from the panels. Only thing I get is free electricity from what they call, excess power. The people that live 3 houses over from me have panels by Solar City, their system quit working after 18 months, now 3 years later Solar City still has not come repair the system. It appears Solar City was only interested in the rebate $$$ and small profit from 18 months of electricity now it is money out of their pocket to repair the system. I did an online search and found this is common practice for other solar panel companies once they get all their money up front and a small profit they abandon the customers. Now the neighbors house is For Sale but they cannot sell it because the solar system does not work. Legal contract says, the home owner can not remove the solar panels from the roof.

 

[Tony Stewart]

Looks like a 1 yr deferred cost bill.

Too much power consumed at peak price as well, could use better insulation.

Infrastructure costs are based on peak capacity. This may help reduce their peak demand but savings to you look doubtful unless you capitalized using only off peak power.

 

[KeepItSimpleStupid]

The biggest plus for PV panels is local power factor correction which is often overlooked and demand side management. Air conditioning runs when the sun is shining, so the utility does not have to build infrastructure to meet the peak demand. PV also credits against the carbon footprint.

Somebody makes it sound good for the residential user. I don't think it is.

First: The utility typically buys power at the wholesale rate and a typical consumer is working during the day. If they were home or running the AC so their dog was more than comfortable, maybe.

Second: The rebates are the incentive, Every 25 years or so, you might have to replace the panels. What about the labor involved of removing the panels to re-shingle the roof?

So, now outfits like Solar City, make it appear to be no or little cost up front, but based on #1 most of the time, it's not cost-effective. Batteries add another dimension and with a grid-tie inverter you don't have power when the utility grid is out.

While we're at it:

Wind has to be used when available and it's very variable. WInd turbines can overspeed. Hydro is relatively cheap, but not everyone has the luxury of hydro power.
It's relatively easy to throttle but not instantaneous. Nuclear is hard to throttle and therfore has to provide the bulk of the average power. Gas generators are extremely quick to throttle production.

The utility has to regulate the power produced based on the demand. The ability for them to actually turn off your devices reduces the demand.

So, PV basically reduces the peak demand somewhat. PV farms require Real Estate which is typically expensive.

I can see a bigger payback for businesses than I see for residential use because they can use the energy the panel produces at the time of production.

With and without incentives, payback is long and eventually you have to start over, but it's good for the utility.

Going off the grid is a another story: See https://www.homepower.com/

 

[PG1995]

Thank you, everyone.

I had grid-tie inverter system in mind because I believe that the concept of reverse metering makes it batter than a solar PV system with battery backup.

Here in Arizona the electric power company started charging customers a $50 fee for having Solar panels. The power company claims it costs them money to buy the excess power, they have to pay employees to deal with this, it is not free. Solar companies here will install the solar panels on your house FREE. Your roof is a place for the solar company to keep their panels. To make a long story short solar companies make it sound good to the customer but in the end the customer does not get much out of this deal.

In California, as I have heard, things are quite different. I think that in California the consumers with PV panels will benefit because of reverse metering. For example, their solar panels will produce electricity during the day and it will reverse the meter reading. Suppose that you used 10 units during the night and during daytime you also generated 10 units then overall you consumed 0 units. Please note that I don't really know how utility buys electricity from a consumer in California. Anyway, someone told me that generating more electricity than you consume on monthly basis wouldn't benefit you. For example, if you consume 100 units in a particular month and also generated 150 units during the same month then the extra 50 units wouldn't really account for anything.

You get 200 BTUs per sq ft of heat from the sun. NO way you can get close to 200 BTUs with electric panels.

"200 BTUs per hour per sq. ft"?

On a bright sunny day, you might get 1000 W/m^2 (or, 92 W/sq. ft) but I believe that this figure is rather optimistic. Anyway, there are 1055 joules in 1 BTU. 92 (1/1055)*3600/hr./sq. ft. = 314 BTU/hr./sq.ft. I hope that I have it correct.

Solar City offered to put FREE solar panels on my roof, 7600 watts of panels. Solar city gets the government rebate, they get all the electricity $$$ the power company buys from the panels. Only thing I get is free electricity from what they call, excess power.

I would request you to clarify the points above. I believe that you are saying that Solar City gets the government rebates and can buy solar equipment such as solar panels at cheaper prices but I don't get why Solar City gets all the income/benefits generated using those panels. What is that "excess power" which you can get for free?

Now the neighbors house is For Sale but they cannot sell it because the solar system does not work. Legal contract says, the home owner can not remove the solar panels from the roof.

Why can't your neighbor sell their home with their existing dysfunctional solar system?!

Looks like a 1 yr deferred cost bill.

Perhaps, it got deferred to facilitate the installation of solar panels.

Too much power consumed at peak price as well, could use better insulation.

Were you referring to this? Please let me know.

Thanks a lot, KISS. I wouldn't make any further queries about your posting because I believe that I have already made enough queries above and you can guide me with them. Thanks.

Regards
PG

 

[KeepItSimpleStupid]

I'll add something though.

There was announcement from Tesla about batteries (Powerwall 3 kW and 7 kW) which they claim could change the game, because you can generate during the day (when rates are lower) and use the power later. This has to assume that you have peak metering.

In other words, it's possible to become self-sufficient. They claim at that point, the utilities could go bankrupt. They also said that some utilities and they named a state that want to charge fees up to $50/month (Wisconsin) if they use solar energy. Arizona approved ~$183/yr and Hawaii is fighting for the same fees.

California is like another country. They are just "different" than the rest of the US. At one time, we had "emissions" and "California emissions" which were stricter. California has the "net-metering" policy according to the article which means the utility has to buy back the excess power.

It's, sort of, like what has happened with gasoline. cars got more efficient, used less gas and now all of the highway departments don;t have enough money. (Tax/gallon). So, you use less and someone else gets hit. OPEC has increased production and prices of gasoline has rapidly fallen in the US and there have been massive layoffs in production workers.

It seems like a double-sided sword.

The AM (Air Mass) 1.5 Global spectrum is 100 mW/sqcm

For example, if you consume 100 units in a particular month and also generated 150 units during the same month then the extra 50 units wouldn't really account for anything.

In California, the utilities would pay you for the extra -50 (your excess power) that you produced as my article by Vivek Wadwah states, so you make money.

Some utilities would buy back at the wholesale rate and not the retail rate which is not "net-metering". Without government regulation, e.g. net-metering, you would be offsetting your used power and, your right - it would be less beneficial.

 

[Tony Stewart]

Thank you, everyone.

I had grid-tie inverter system in mind because I believe that the concept of reverse metering makes it batter than a solar PV system with battery backup.



In California, as I have heard, things are quite different. I think that in California the consumers with PV panels will benefit because of reverse metering. For example, their solar panels will produce electricity during the day and it will reverse the meter reading. Suppose that you used 10 units during the night and during daytime you also generated 10 units then overall you consumed 0 units. Please note that I don't really know how utility buys electricity from a consumer in California. Anyway, someone told me that generating more electricity than you consume on monthly basis wouldn't benefit you. For example, if you consume 100 units in a particular month and also generated 150 units during the same month then the extra 50 units wouldn't really account for anything.



"200 BTUs per hour per sq. ft"?

On a bright sunny day, you might get 1000 W/m^2 (or, 92 W/sq. ft) but I believe that this figure is rather optimistic. Anyway, there are 1055 joules in 1 BTU. 92 (1/1055)*3600/hr./sq. ft. = 314 BTU/hr./sq.ft. I hope that I have it correct.



I would request you to clarify the points above. I believe that you are saying that Solar City gets the government rebates and can buy solar equipment such as solar panels at cheaper prices but I don't get why Solar City gets all the income/benefits generated using those panels. What is that "excess power" which you can get for free?



Why can't your neighbor sell their home with their existing dysfunctional solar system?!



Perhaps, it got deferred to facilitate the installation of solar panels.



Were you referring to this? Please let me know.

Thanks a lot, KISS. I wouldn't make any further queries about your posting because I believe that I have already made enough queries above and you can guide me with them. Thanks.

Regards
PG

I think KISS's estimates are valid, just need to multiply by PV efficacy of 15% to 22% depending optical bandwidth if it includes IR and steerable PV * number of sunhours per month.

Yes the overcharge above 1500kWh goes from 10 to 18 cents per kWh and that bill was more than 50% surcharge, so the power use was excessive, hence more insulation needed. i have R50 -R90 in attic DIY rental blown fiberglass 7x compressed batts and added 1-2feet with leaf blower extension tube. Ventilation to attic is critical. So added ride vents and continuous open screen soffit vents. cost 800$ payback 2 yrs

Our bill is only $150/mo now with gas furnace and TIme of day rates in the range of 8-14 cents/kWh...not sure.

 

[gary350]

Thank you, everyone.

I had grid-tie inverter system in mind because I believe that the concept of reverse metering makes it batter than a solar PV system with battery backup.



In California, as I have heard, things are quite different. I think that in California the consumers with PV panels will benefit because of reverse metering. For example, their solar panels will produce electricity during the day and it will reverse the meter reading. Suppose that you used 10 units during the night and during daytime you also generated 10 units then overall you consumed 0 units. Please note that I don't really know how utility buys electricity from a consumer in California. Anyway, someone told me that generating more electricity than you consume on monthly basis wouldn't benefit you. For example, if you consume 100 units in a particular month and also generated 150 units during the same month then the extra 50 units wouldn't really account for anything.



"200 BTUs per hour per sq. ft"?

On a bright sunny day, you might get 1000 W/m^2 (or, 92 W/sq. ft) but I believe that this figure is rather optimistic. Anyway, there are 1055 joules in 1 BTU. 92 (1/1055)*3600/hr./sq. ft. = 314 BTU/hr./sq.ft. I hope that I have it correct.



I would request you to clarify the points above. I believe that you are saying that Solar City gets the government rebates and can buy solar equipment such as solar panels at cheaper prices but I don't get why Solar City gets all the income/benefits generated using those panels. What is that "excess power" which you can get for free?



Why can't your neighbor sell their home with their existing dysfunctional solar system?!



Perhaps, it got deferred to facilitate the installation of solar panels.



Were you referring to this? Please let me know.

Thanks a lot, KISS. I wouldn't make any further queries about your posting because I believe that I have already made enough queries above and you can guide me with them. Thanks.

Regards
PG

The contract is written in a way that all the power that is sold to the power company pays for the cost of the home oweres free solar panels. That is how Solar City can afford to give you solar panels installed FREE. I can not remember the details I threw away the contract that I never signed. Home owner gets enough power durning the day to run every thing in the house, all the excess power is sold to the power company. NO power goes into storage batteries. During the day is PEAK power and according to the Utility bill peak power is about 3 times more expensive than after dark when power rates drop 66%. The home owner gets free electricity during the day, all excess power is sold and that pays for the $40,000. worth of inflated price solar panels. According to the math Solar city claims free power 12 hrs a day reduces your electric bill 75% because rates are lower after dark and outside air temperature is lower so your AC unit runs less after dark and used less power than it does during the day. A lot of what Solar City claims is unknown until the system has been installed and tested. Solar city gets the rebate and the home owner gets FREE solar panels and 75% reduce in the electric bill so they claim.

People 3 houses up from me say that is not how it really turns out home owner gets a whole lot less than what Solar City claims and now there system has not been working for 3 years they get nothing. Now the people are getting charged $50 a month by the power company for having solar panels that do not work. As long as the panels are on the roof power company will charge them a fee. Attorney told them they could get sued if they remove the panel without solar city permission. Last thing I heard from the neighbors attorney has given solar city a dead line, get those solar panels off the roof or we will remove them and send you the bill.

 

[Tony Stewart]

No such thing as a free lunch, if you agree to free $50k installation, then it must be maintained at your expense, unless you prove defects. Otherwise you pay later in legal costs and aggravation.

 

[gary350]

No such thing as a free lunch, if you agree to free $50k installation, then it must be maintained at your expense, unless you prove defects. Otherwise you pay later in legal costs and aggravation.

Solar Company contract says, they will maintain the system free. Part of what they claim makes this deal good is, it costs the home ower NOTHING to get solar on their house. The home owner is providing a roof for solar company to keep their solar panels. Home owner allows solar company to put solar panels on the roof, the home owner gets some of the electricity free. There are 5 companies doing this solar panels give away in the Phoenix area.

Something is going on at the neighbors house this morning. Workers showed up at 7am with a large black trash dumpster trailer parked in the driveway. They threw all the solar panels in the trash dumpster. Workers removed the roof clay tiles, now they are replacing the felt paper that covers the plywood roof. Looks like roof repair. I need to talk to the neighbor again this evening to see what is going on. I wish I could have gotton those panels before they were all trashed.

**broken link removed**

 

[Tony Stewart]

Ah too late,

free maintenance, so why not working?

Save em anyway.

We are destroying our planet with oil fracking and cheap disposable goods from China.

Its about time, we focus on renewable energy and conservation.

 

[PG1995]

Hi

This discussion is about a grid-tied PV system in the state of California.

Q1:
Someone was suggesting to me that microinverters are a lot better than string/central inverter. All the webpages below say nice things about microinverters and they do make you think that microinverters are way better than string inverters even if there are few cons associated with them. Personally, I'm not in favor of microinverter although I have never installed or worked with any solar PV system. They cost you quite more than string inverter(s) for a system as I have read. They make the system complex. They are relatively new entrants to the market. On the other hand, if you make sure that you install the panels such that shading by trees and other structures is avoided and the panels don't become too dirty and the panels are located adjacent or close to each other then it makes string inverter more feasible. Besides this, you can always opt for more than one string inverter for a system. For example, if you have a pitched roof facing east and west, then you can have two separate string inverters for east and west sides. (I believe that some string inverters already comes with dual MPPT functionality.)

Solar tracking really make a PV system efficient; actually it increases the efficiency more than MPPT does. But still having solar trackers makes the system costly, complex and require regular maintenance, especially for small systems.

a: What is your informed opinion about microinverters when compared to a string inverter?

b: Further, I believe that if you are into the business of installing solar PV system then, in my humble opinion, string inverters would suit you better from financial and business point of view because you want to increase your profit as much as you can and still provide the customer with something reliable and efficient. For example, if you can install 1 kW system for under $5000 compared to $7000 with microinverters then the customer would be more interested into $5000 deal and at the same time you can get string inverters at reasonable rates. Do you agree?

1: **broken link removed**
2: http://blog.gogreensolar.com/2014/0...ween-microinverters-and-string-inverters.html
3: http://energyinformative.org/are-solar-micro-inverters-better-than-central-inverters/
4: **broken link removed**
5: This video tries to help you figure out if you need microinverter or string inverter.
6: http://en.wikipedia.org/wiki/Solar_micro-inverter

Q2:
A DC optimizer is basically an MPPT unit which is connected close to each solar panel/module so that the panel can operate at its optimum power point. But it's just a DC-DC converter which means you still need an inverter to convert DC to AC as is explained in the links below.

Now the question is that most inverters come with already having MPPT feature so if we are using a DC optimizer along with an MPPT inverter, would it create issues between the two units?

1: **broken link removed**
2: This video discusses DC optimizer and microinverter.

Q3:
I was looking for the information on allowable types of mounting/racking systems and maximum allowed load per sq. foot of a roof in California but couldn't find any good resource. Could you please point me to some resource?

Q4:
I have seen at some places where inverters being used were from either SMA Solar Technology and Fronius. It looks like Morningstar is also somewhat popular. I don't really know if these are popular here in the US. What are popular manufacturers in the US which make reliable, efficient and not very expensive inverter units?

Thanks a lot for the help.

Regards
PG

Helpful links:
1: This video shows you how to install a PV system.
2: http://www.nabcep.org/wp-content/up...nstaller-Resource-Guide-August-2012-v.5.3.pdf (general guide about installing PV system)

 

[KeepItSimpleStupid]

Q2: There may not be one. You generally have to support the weight of the roof itself, wind and snow loads. I doubt people add the weight of solar panels yet. https://qcode.us/codes/placercounty/view.php?topic=15-15_04-15_04_135 I did these calcs in a Building structures" class.

I could see a clear advantage to microinverters if:
1) You were storing power
2) You had shading issues.
3) You were operating entirely off the grid.

I had not heard of mico-inverters before.

 

[Tony Stewart]

https://en.wikipedia.org/wiki/Solar_micro-inverter

 

[PG1995]

Could someone please help me with the queries from post #12? Thanks.

 

[Tony Stewart]

The benefits of microconverters are when they are integrated into each panel.
The cost differentials are getting smaller but one should put more weight on reliability with 10 yr warranties and brand name quality.

MPPT is essential when no intermediate DC storage is not available at 78 to 82% of the Voc value which is when MPPT is not needed as this is the optimal voltage.

 

[KeepItSimpleStupid]

Q2: I don't see any issues. The MPPT would see max power no matter what it does.

Q4: Xantrex is a high end manufacturer. See: https://www.wholesalesolar.com/products.folder/inverter-folder/xantrexxw6048.html