Solar Energy International Grid-tied Training

[SegDog]

Hello,

Recently, I attended the 5-day SEI training. Slightly basic for working electricians, but learned a lot anyway. I'm not a tree-hugger, but wanted to learn as much as possible. Of course, there's a new module coming out soon that has a micro-inverter attached that, effectively, makes it an AC source, not DC. Still good to know about DC inverters.

The instructor was biased toward grid-tied only, as opposed to battery back-up, and the other night our neighborhood lost power due to the excessive heat. Glad I'm a back-up type. I like to sleep through blackouts.

My nightmare has been earthquakes. It's still possible to have a good one. The way people go nutz-o over the price of gas, what would happen if we didn't have any utilities for months. Got to stock-up on self-defense gear...

 

[gar]

080612-2134 EST

SegDog:

Some information on what you learned would be useful.

For example: If you are tied directly to the grid and no batteries, then is all power that you generate and you use at the time of generation free to you?
Or does all power you generate go to the grid and then come back to you? What happens is going to depend upon on how the power metering is done.

I have never seen any economic analysis that shows solar to be less expensive in our area, $0.11 per KWH, than our coal supply. Did you get any real valid information on this part of the subject?

.

 

[dsiu]

commercial systems

commercial systems

does anyone know who or where we can get information on installation methods for medium to large solar systems?

 

[SegDog]

top ten things learned (learned properly)

top ten things learned (learned properly)

10. magnetic declination and proper (compass) interpretation of "true South"

9. site analysis (orientation, shading, cleaning)

8. path of the Sun and possible, regional atmospheric interference

7. benefits of battery back-up; even a small back-up is good (importance of residential load analysis, and identifying critical loads)

6. selling power back to POCO in net metering states (various meter schemes)

5. NEC 690

4. modules are more efficient (productive) under 77 degrees F (solar heating and voltage -Temp relationships)

3. general electrician concerns; wire, system, inverter sizing, type, selection, routing, location, UL listing, bonding/grounding problems with aluminum framing members, mounting and mechanical decisions for safe installation.

2. selling a system that costs 25X more than a generator, but is quiet, clean, life-long, little maintenance, works only when the Sun is shining, can add value....

1. the new micro-inverter (AC) modules are coming, and are worth waiting for, and Thermal water-heating is a much easier sale.


Grid-tied systems were the ones given the rebates, when there were rebates. G-t (only) inverters are less (relatively) expensive than some other inverters. Net meter states are required to cooperate with solar customers, and purchase their excess, with limits set by the legislature. Some states required utilities to credit their solar customers, but can put limits on carry-over to succesive years (I believe; sort of like cell phones). Buying solar is like new car MPG, and you must explain to the customer that the advertised ratings are severely effected by conditions, and are often not attainable.

A balanced approach is the way to go.

 

[hillbilly1]

The PoCo usually will only pay you wholesale for the electricity you sell them, so it's considerally less than what you are paying them for a KWH.

 

[newenergy]

gar,

Unless you're in the Wisconsin Public Power, Inc area, you don't seem to have much in the way of incentives in Michigan. Couple that with not having much sun up there and even though PV systems last a long time and don't require much maintenance you're not going to save money until your electrical prices go up and/or PV prices come down.

dsiu,

There are large roof mounted systems, but most utility sized systems are ground mounted. Unirac and Prosolar both have ground mounting equipment, but most very very large jobs are some kind of custom mounting system.

hillbilly1,

Net metering laws vary by the state, but many of them simply install a meter than spins backwards when you provide more power than you use and credit those kwhs right to your account. So, you sell for exactly the price you buy.

 

[SegDog]

all good points...

all good points...

for discussion. My goal is to share basic information about what's available to fellow tradesmen, and not be "put-off" like I was by area installers. It took a few years to figure-out that they felt threatened by me asking questions. I was not brought-up in the "school of ignorance", and I, always, believed that helping fellow electricians promoted more business; not take-away. (off soap box)

The discussion about "not enough sun" is a good place to start when sizing and understanding the importance of good design/installation. People in Canada and Alaska have good results with their solar, but they, also, have wood stoves and other contingency plans for bad days.

Understanding your limitations and boundaries is a good starting place for any system. How you explain these may keep you from killing a deal. Government rebate programs are one of the few things government seems to do right, depending on whether you're the recipient or have a big tax bill.

 

[SegDog]

pole mounts

pole mounts

The pole mounted arrays got my attention because they are really a good way-to-go if you have a little clear area, and have orientation and other obstacles for roof-mount. (you can take your gear with you when you move)

The Power Fab brand (not an endorsement) that I've seen are engineered to be balanced and custom made for different maunufacturers. The modules are bolted-on. Not every module maker has bolt holes, so you have to do research.

What I learned, is that when you get your poles for putting in the ground, you weld a couple horizontal stakes (rebar) for the part that goes below surface, in order to prevent the poles from twisting in the wind. The poles will spin, even in concrete, under wind-load. Second thing, you run your conduit up to the pole before you pore concrete. Saves you the embarassment later of running your conductors in "Rube Goldberg" fashion.

 

[switchleg45]

newenergy,
You sound pretty knowledgeable in the subject of PV. Tell me, how can we expect the avg citizen, especially in light of current economic conditions, to afford solar systems at 25-50k and up? It seems to me that the 1% of the population that control 50% of the countries wealth is certainly not going to make any effort to change the status quo. There coffers are still filling up quite nicely...don't you think?

 

[DownRiverGUy]

My calcluations for PV Return on Investment

My calcluations for PV Return on Investment

So I've studied PV for quiet sometime and I have come up with these calculations to figure out ROI for a PV system...

Let me guys know what you think!

First off to find out the power we can produce we need accurate solar data for your site

http://rredc.nrel.gov/solar/old_data/nsrdb/redbook/sum2/state.html

Say hello to the motherload.

Attached is a PDF file that shows the data and process to calcluate PV ROI. I cannot attach the excel file in the forum

The pdf is a work in progress so it's VERY sloppy and most of the stuff in there is just data. Let me know if this helps anyone and I may post other things like this.

 

[dereckbc]

I have been designing Off-Grid systems for a few years now and can answer quite a few of the questions.

The most important one folks need to ask is payback time, and replacement cost, because they are not as maintenance free as the indistry leads you to believe.

ROI is a factor of where you live, and unless you live in southern California or Arizona where there is plenty of sun, stiff competition, with high tiered utility rates, and your neighbors picking up a large portion of your investment cost, there is never a return on the investment. Your grand children will still be paying for it when they die.

As for the maintenance issue, don't believe it. The systems I installed 5 years ago, about 50% of the panels have failed. They are not the cheap unknown brands, I am talking about BP and kyrocera.

The killer is heat. The panel effeciency ranges from 10 to about 18%. The 90 to 82% missing is turned into heat, and heat destroys the delicate silicon P-N junctions and the wire connection to the panels.

The manufactures counter this argument with their warranty. But you had better look closely what the warranty is. For example BP has the best called 25-12-5 which appears confusing but here is what it means
25 years the panel will produce at least 80% of its rated power
12 years the panel will produce at least 90% of its rated power
5 year, this is the big one. Limited warranty of material and workmanship.

Well if the module fails after 5 years, tuff-luck, you get to buy a new one. If before 5 years it is pro-rated like tires or batteries.

Don't get me wrong I am all for alternative energy, but until PV installation cost come down to $1 per watt, don't need my money to install one on my neighbors house, and work out the technical problems I just don't see any real application as of now.

Well there is one exception. Remote locations where POCO power is not feasible like cell tower sites where I have been using them.

 

[petersonra]

the reason they push grid tied systems is because batteries are expensive. i have read it can cost 25-50 cents to store a single kw-hr.

 

[JeffD]

A rough study I did figuring an average of 4.25 hours of sunlight a day gave me a payback of around 45 years. Not as detailed as the previously posted study though and does not take into account losing efficiency. Also as noted pv has life spans. The concensus is around 20 years. So a pv system will never pay itself back. The above does not include batteries.
I had a friend who was doing research with NASA and he said until they find a way to convert solar energy like plants do it will be hard to make it economical.

 

[Sierrasparky]

I have been designing Off-Grid systems for a few years now and can answer quite a few of the questions.

The most important one folks need to ask is payback time, and replacement cost, because they are not as maintenance free as the indistry leads you to believe.

ROI is a factor of where you live, and unless you live in southern California or Arizona where there is plenty of sun, stiff competition, with high tiered utility rates, and your neighbors picking up a large portion of your investment cost, there is never a return on the investment. Your grand children will still be paying for it when they die.

As for the maintenance issue, don't believe it. The systems I installed 5 years ago, about 50% of the panels have failed. They are not the cheap unknown brands, I am talking about BP and kyrocera.

The killer is heat. The panel effeciency ranges from 10 to about 18%. The 90 to 82% missing is turned into heat, and heat destroys the delicate silicon P-N junctions and the wire connection to the panels.

The manufactures counter this argument with their warranty. But you had better look closely what the warranty is. For example BP has the best called 25-12-5 which appears confusing but here is what it means
25 years the panel will produce at least 80% of its rated power
12 years the panel will produce at least 90% of its rated power
5 year, this is the big one. Limited warranty of material and workmanship.

Well if the module fails after 5 years, tuff-luck, you get to buy a new one. If before 5 years it is pro-rated like tires or batteries.

Might I ask what is failing. When I hold one of these panels in my hand My first thought is "this sucker cost 800 bucks what a cheap piece of crap" I am not a fan of the quality of the product for the price. Then there is the fact that we are told that wafers are so expensive. Yeah right. when they have the same desnsity as a Intel processor then I might belive. I hope this guy I saw on TV the other day that is making a film that looks like it rolls out of a printing press seems promising.

 

[SegDog]

Good discussion...

Good discussion...

and thanks to the many responders. Not enough healthy (understandable) skepticism is around for the average tradesman to make good decisions.

Like most people, the fact that NASA (others) use PV to power their satellites leaves a subconscious image of confident usage of a technology. One poster mentioned failures and manufacturer warantees of their product. This is one reality-check that an EC has to be prepared to answer. Only once do I remember NASA replacing modules. It would be interesting to know their failure rate and reason. Outer-space is cold and would, also, effect joints and other material.

My storage batteries have bailed me out of more than one jam. Although relatively expensive (inverters), I would rather have them than not. Keeping them charged is one of my hobbies.

My goal is, always, to be knowledgeable of safety, wiring, fusing, common-sense usage...having fun while filling a need.