Solar 101....

[Bryan Couch]

Well here it is. I've been reading "solar" (which when I started meant solar power) almost every chance I get and I've also started in on some offshoot topics like passive solar heating, domestic hot water heating, ground source heat pumps, ground source air heating and structural insulating panels, insulated concrete forms and the like.

I just realized the thread name might be a little misleading... I'm not giving the "101"... I'm asking for it! Lol

There are so many things to think about when it comes to "solar". I was under the impression, as I assume many are, that you just screw a bunch of panels on your roof and make electricity! (Ok, I knew there was a little more to it than that but I had no clue how much!) I'm starting to get a feel for the terms but I'm still not finding some of the info I'm looking for so here are some questions.

What is the "real" difference in ratings and manufacturers? I've read the manufacturer info and everyone's PV modules are "the best". How do I know? What do I look for?

What's the difference between a mono and a poly PV module?

What about power ratings? I know that when I'm comparing them the conditions of testing make a difference but what's the difference between 250W, 300W and 350W, what is it actually telling me? Is it a case of more power from the same surface area (I have noticed that some of the sizes are different but others are not)? If so my next line of thought is...

If space isn't a concern then I can match module size to production needs (assuming under ideal conditions a 250w panel will give me 250 watt/hour, 300W=300w/h etc). If space IS a concern then how could I even guess at how much power I would need, especially for a house that isn't built yet?

I hope the members here don't mind all the questions and I'd like to thank everyone for the info I've got from other threads here. I'm hoping that I can use this thread to learn a little more and verify what I "think" I've taught myself! I'm a little distrustful of salesmen and experts (no offence to anyone on this site) I've been burnt too many times by someone who didn't quite tell me the whole story.

I'm sure I'll have more questions soon! Thanks in advance!
Cheers!

[Rob Beckers]

Hi Brian,

Well here it is. I've been reading "solar" (which when I started meant solar power) almost every chance I get and I've also started in on some offshoot topics like passive solar heating, domestic hot water heating, ground source heat pumps, ground source air heating and structural insulating panels, insulated concrete forms and the like.

I just realized the thread name might be a little misleading... I'm not giving the "101"... I'm asking for it! Lol

There are so many things to think about when it comes to "solar". I was under the impression, as I assume many are, that you just screw a bunch of panels on your roof and make electricity! (Ok, I knew there was a little more to it than that but I had no clue how much!) I'm starting to get a feel for the terms but I'm still not finding some of the info I'm looking for so here are some questions.

What is the "real" difference in ratings and manufacturers? I've read the manufacturer info and everyone's PV modules are "the best". How do I know? What do I look for?

The ratings are standardized, so it's pretty easy to compare between manufacturers. When they say a panel is rated at (say) 250W, it means the same for every manufacturer; they shine a light with a similar spectrum as sunlight on it with an intensity of 1000 W/m^2, and the panel is at 25C.

In the real world panels will rarely actually produce rated output. But at least it does make for something that can be used to select panels and compare between producers.

There are differences between manufacturers in terms of quality, durability, and if their warranty is worth anything (most of these companies will be long gone by the time the standard 25 year warranty runs out). Stick with a major brand.


What's the difference between a mono and a poly PV module?


These days there's no real difference any more. In practice they work the same, last the same time etc.


What about power ratings? I know that when I'm comparing them the conditions of testing make a difference but what's the difference between 250W, 300W and 350W, what is it actually telling me? Is it a case of more power from the same surface area (I have noticed that some of the sizes are different but others are not)? If so my next line of thought is...


See my earlier answer.
300W+ panels are generally larger than the 'usual' 240 - 270W panels. Those around 250 Watt are made from 60 cells, the 300W panels are made from 72 cells. Different voltage because of that too (each cell is about 1/2 Volt).


If space isn't a concern then I can match module size to production needs (assuming under ideal conditions a 250w panel will give me 250 watt/hour, 300W=300w/h etc). If space IS a concern then how could I even guess at how much power I would need, especially for a house that isn't built yet?


A 250W panel will not steadily produce 250 Watt-hour. It will produce zero energy at night, ramp up during the day to some maximum (generally less than rated output power), and ramp down again. How much energy it produces during an average day is a function of the number of (average) sun-hours for your location and time-of-year, and then there's efficiencies of inverter, wiring losses etc.


I hope the members here don't mind all the questions and I'd like to thank everyone for the info I've got from other threads here. I'm hoping that I can use this thread to learn a little more and verify what I "think" I've taught myself! I'm a little distrustful of salesmen and experts (no offence to anyone on this site) I've been burnt too many times by someone who didn't quite tell me the whole story.

I'm sure I'll have more questions soon! Thanks in advance!
Cheers!

-RoB-

[Joe Blake]

Hi Bryan,

Welcome to the forum. Rob has covered pretty much all the bases by the look of his posting. Just to give you some figures from my own system as to what you can possibly expect. I live in Perth, Western Australia, which is at roughly 32 degrees south, and generally pretty sunny in summer. In Jun 2009 I installed 1,000 watts worth of PV. A few months later I installed a further 600 watts. (This made it a total of 8 physical panels). Then in Jul 2013 I installed a second similar sized system, taking my total generating capacity to 3,200 watts. (This consisted of 6 physical panels, though larger in area). Because my northern roof face is covered by a solar hot water system, I had the first system installed on the Western side of the roof. The second system was placed on the Eastern face. (All the panels were rated between 250-260 watts each.)

The first graph shows a month by month plot of power generation from Jun 2009 to Oct 2013. The graphs are a bit small so I'll say that the Y axis goes from 0 to 280 kWh.

http://i82.photobucket.com/albums/j245/saxeharp/general9/solargraphs_zpsfa48168c.jpg (http://s82.photobucket.com/user/saxeharp/media/general9/solargraphs_zpsfa48168c.jpg.html)

The second graph shows the day by day percentage of power generated over 12 months. The percentage indicates how much of my household consumption comes from the rooftop system. The Y axis peaks at 325%. The red line is the current year.

The third graph shows the power generated daily over the past 12 months, and peaks at 20 kWh. Again the red line is the current year. You will notice that even though my initial system was rated at 1.6 kW, I never exceeded 10kWh in a single day. It's still not high summer yet, so I can't comment on the total generating capacity of my system, but maximum generation (so far) is 16 kWh in a single day.

This quick graph shows the effect of having the panels on the west (red) versus the east roof face (blue). There is a very tall tree on the eastern side which casts shade on the roof until about 9:00 am, then the output kicks up very quickly.

http://i82.photobucket.com/albums/j245/saxeharp/westveast_zps628f06b5.jpg (http://s82.photobucket.com/user/saxeharp/media/westveast_zps628f06b5.jpg.html)

Hope that is of some assistance to you.

Joe

[Bryan Couch]

Thanks for the information Rob and Joe it's a great help. I guess I should have qualified my statement on sizing the system to my usage based on unlimited space. I've seen more than once an estimate of 77-78 percent of the system rating being supplied with the rest lost to the system. I'm still thinking in a basic sense, not factoring in variables, just an ideal day I guess.

As an easy math example...
I have a due south oriented roof and mount 40-250W panels at an angle equaling my latitude in my case 50 degrees, giving me a total of 10kW rated capacity.
If the system produces 75% of its rating my system is capable of 7.5kW actually seen in the house after an hour of sun hitting the panels at 90 degrees.
This number would obviously decrease the closer you are to sunrise and sunset and with cloud cover.
How do I estimate the production through the day? For example the sun is directly south east (45 degrees east of my panels orientation) at an elevation of 25 degrees to the horizon (25 degrees lower than my panel angle). This would allow me to calculate my perfect sunny day production for any time of the year.

I really like the graphs Joe, numbers and stats are my kind of thing! Lol
It looks like your addition is producing about the same amount as the 1st phase so far. What are you using to track all of the stats and graph them?

[Rob Beckers]

Hi Brian,

Unless you want to actually learn how to calculate this from the basic numbers (which would be a much longer story), the short answer is that an ideal south-facing roof in your area will produce 1140 kWh per kW of solar PV in an average year.

'Ideal' in this context is perfectly south facing, no shading, with about a 40 - 50 degree pitch.

So, 10kW of panels would be expected to produce around 11,400 kWh a year on average.

-RoB-

[Joe Blake]

I really like the graphs Joe, numbers and stats are my kind of thing! Lol
It looks like your addition is producing about the same amount as the 1st phase so far. What are you using to track all of the stats and graph them?

I use an alarm clock to get out of bed early to read the meters before the sun starts to generate power.:D I usually read everything at about 6:30 am in summer and 7:30 am in winter. I get the import/export figures from the digital meter supplied by the utility. I'm on SmartPower, which gives different costs depending upon the time of day, then I read my two inverters, from which I only take the total cumulative generation. I then feed the figures into a Quattro Pro spreadsheet while I eat my breakfast. The figures translate into Microsoft Excel, but the graphs don't convert very well. I'm not a great fan of Microsoft, so I've never bothered generating the graphs in XL.

If you'd like a copy of the spreadsheet so you can copy all my formulae and apply them to one of your own, send me an email address and I can attach a copy of the document.

Joe

[Andy Rhody]

Bryan, a lot of those questions are things that I always wanted to know but was afraid to ask LOL: (and I just put in a solar set-up last month).

Not to be too forward or anything but if I were you with your conditions and with the price of solar being down, I'd just go for it. Rob can make it happen.

[Bryan Couch]

Bryan, a lot of those questions are things that I always wanted to know but was afraid to ask LOL: (and I just put in a solar set-up last month).

lol. I've learnt in the last few years that these forum boards can be a huge source of info if you ask! (I bought a truck and dove deep into diesel repair based on forum and internet knowledge!). I know, well knew, pretty much nothing before I found this place and it seemed like there were a few friendly guys here with some good knowledge of this stuff. I'm doing my best reading and learning for myself but I like to verify what I've learned with "those who know". :)

Not to be too forward or anything but if I were you with your conditions and with the price of solar being down, I'd just go for it. Rob can make it happen.

The more I look into it the more I'm interested in it. In our current house it's not an option right now. My money would be better spent on leaky doors and poorly designed heating. Our second floor only has one cold air return (the size of a regular heat vent) and 3 heat vents, not enough for 1250 sqft... 4 bedrooms and a bathroom. If the house was energy efficient I'd be in without a doubt! The other issue is whether or not we'll be in this house in a few years. With the good possibility of a gold mine we could be moving the house or building new. We should hear more about this in the 1st quarter of 2014 but I like to research and plan for things so I can make the most informed decision possible. IF we build there will be solar. IF our house is moved we'll see how it works out. IF things stay as is we'll be doing some fixing and eventually solar. So basically right now I'm in research mode...find out everything I can about all of the possibilities and we'll see what happens in a few months.

Right now we use an average of 9 kWh for the summer and 35 kWh in the winter. I could easily cover my summer usage and with a 10 kW MicroFIT I think I would be making what I use in a year. What I'm wondering though is during the dark of winter how much power would that 10 kW system be producing? The days get pretty short up here!

This brings me back to the calculations. If it's not too much trouble Rob I would actually LOVE to know how to figure it out from the basic numbers.

As an aside... This is where I'm hooping my knowledge is taking me... My wife has been asking about the possibility of going off grid! I told her a while back I didn't think it would be a option up here without some big expenses, lifestyle changes and issues to work around but now I'm starting to wonder. If we end up building it would be pretty easy to incorporate passive solar heating, ground source heating, solar hot water and solar power on a new build. Everything could be designed to work a well as possible together right from the start. January is the issue though. 5 hours or so of sun means we need lights for a good portion of the day and don't have a lot of time to produce power and -30C to -40C puts a pretty big demand on our heating system. I do love a challenge though and a family of 8 (plus 2 dogs) living off grid sounds like a pretty big challenge! :oh:

[Rob Beckers]

Hi Bryan,

I've got a little time before I have to put my 4-year old in bed, so here goes:

Starting with the off-grid; it's certainly possible to go off-grid. However, certain things are better done non-electric in that case, because it's just very difficult to generate enough of it in winter to run those. In particular, space heating (including a heat-pump, even if they are efficient, they are very hard to run), cooking, A/C, and a laundry dryer. All the other regular stuff can be done, though keep in mind that no matter how you slice it, making your own electricity is quite a bit more expensive than buying it from your local electrical provider.

As it happens, we're in the middle of installing all the equipment for a house to take if off-grid. This is a large one, as off-grids go, with an estimated monthly use of 300 kWh/month, including winter. This particular house was never meant to be off-grid, but it turned out that connecting it would cost $100,000+, and so we're taking if off-grid for about half that money. That meant doing away with the A/C, and switching to propane for a number of items though (and severely economizing on use with many other items).

Keep in mind that the average Canadian household uses 1,000 kWh/month. Contrast that with a large off-grid using 300 kWh/month and you start to get the idea...

Winter is the hard part; the sun just doesn't provide much in late November and December, but the system has to be sized for this (which makes the summer very easy, there will be more than enough power at that time). We are installing a backup generator to till the home owners over for those periods when there's just no sun, though running a genset on propane is not cheap!

MicroFIT is not related to what you use yourself, you just sell all the electricity you produce directly to the grid, and get paid for that though a 20-year contract with the OPA. So, it comes down to how much space you have on the roof (that faces somewhat south and isn't shaded). MicroFIT has a maximum size of 10kW.

I'll write a separate post about predicting output vs. location and month.

-RoB-

[Rob Beckers]

Now to PV array size vs. output power:

The starting point is a table with daily sun-hours for your location. For Canada a good one is http://pv.nrcan.gc.ca/index.php?n=1830&m=u&lang=e, and I've already selected Geraldton, ON. What you need is the last table in there, insulation in kWh/m^2.

What's listed in that table is how many kWh of sunlight fall on a square meter of PV panels at a given tilt angle. So, to take "south facing latitude +15" for November; it has only 2.6 kWh per square meter, per average day for that month, for panels mounted at an angle of about 50+15 = 65 degrees tilt. This is also named sun-hours, since each 'hour' in there is the equivalent of 1,000 Watt (1kW) on a square meter, and doing so for 2.6 hours on an average day in November (making for that same 2.6 kWh).

As it happens, PV modules are rated at sunlight with an intensity of 1000 Watt/m^2; that means a 250 Watt PV module will produce an output of 250 Watt when the sun shines on it with that 1000 Watt/m^2 (and the module is 25 Centigrade in temperature).

That makes for a convenient conversion from sun-hours to kWh produced: Those 2.6 sun-hours in essence means that the sun shines for 2.6 hours a day, with an intensity of 1000 W/m^2 on that 250 Watt panel mounted at 65 degrees. That will produce 2.6 * 250 = 650 Watt-hour, or 0.65 kWh. One 1kW of solar panels (or 4 of those 250 Watt panels) will therefore produce 4 * 0.65 = 2.6 kWh. Each average November day.

This is what would come out of the panels if there were no losses anywhere along the line, and if those panels are 25 degrees Centigrade. In reality there are inverter losses, wiring losses, dirt on the panels, temperature losses etc.

For a grid-tie solar installation a reasonable efficiency is 75%. So that 1kW of panels will make about .75 * 2.6 = 1.95 kWh per day, or 30 * 1.95 = 58 kWh for November.

For an off-grid installation things get a little worse. The inverters are not as efficient as grid-tie, and batteries take more energy to charge than they will release. The efficiency also depends (greatly) on the use of an old-fashioned PWM-type solar charge controller, vs. a more efficient MPPT-type charge controller. A reasonable overall efficiency number for a PWM controller with batteries and off-grid inverter would be 44%, while the efficiency with an MPPT controler would be 52%. Quite a bit worse than simple grid-tie.

So, that 1kW of panels used off-grid with an MPPT charge controller would deliver about .52 * 2.6 = 1.35 kWh per day, or 40 kWh for the month of November. To make, say, 300 kWh for that month would require 300 / 40 = 7.5 kW of solar panels. Keep in mind that this doesn't take any shading into account and assumes those panels face perfectly south!

You can do this for every month and get a total for the year. Or you can use the overall average yearly sun-hour number: It's listed at 4.2 sun-hours per average day for the year, for panels mounted at an angle equal to the latitude (or about 50 degrees). That means 1kW of panels used for grid-tie would make about 4.2 * 0.75 * 365 = 1,149 kWh per average year. Compare this to the first table on that Web page; it did the calculation for you, and shows that same 1,149 kWh annually!

And there you have it...

-RoB-

[Peter Klaassen]

Hi Rob,
I see your calculations for inverter inefficiencies for off grid. Where do you get those percentages? I was not aware of the loss at that level. For our system (1.35 kW array and Outback equipment) we get the batteries up to float in the summer. On average it seems we are using 6 kWh per day here. The charging input goes down as the batteries become full. Is this what you are referring to in the loss? Also there is gassing of the batteries and inefficiencies within the flooded batteries. I am guessing that the same would apply to the wind turbine input amount?
I still don't like Ontario Hydro and I am glad to be clear of them even if grid tie would improve my power production.
Pete

[Rob Beckers]

Hi Peter,

The numbers come from the following: Off-grid inverters (Outback, Xantrex, Magnum) are around 85% efficient (depends a bit on load etc., but it doesn't get much more than that). Funneling energy through a battery nets you around 80%. This is because of gassing, and heat generated mainly during absorption stage. Those two make for .85 * .80 = 68% efficiency.

For the charge controller side take a look at the panels vs. batteries: For a 12V system a 36-cell panel is used, which would run at just about 18V MPPT. That is not how it's used with a PWM controller though, where the panel runs at battery voltage, which is about 14.5V during much of the charging. The current of that panel won't change much, the voltage does though, making it about 80% efficient just because of that mismatch. Then there's the usual losses due to temperature (most of the time the panel is warmer than 25C), line losses, regular losses in the charge controller that have nothing to do with the voltage mismatch etc, much like a grid-tie inverter's losses this part ends up around 80%. That's how it is just about 65% efficient overall for a PWM charge controller.

MPPT controllers do better, they don't have that 20% loss due to panel mismatch. They get 77% efficiency overall, very much like a grid-tie inverter would from panel rating to power into the grid.

So, multiply it all out: For PWM you get 0.68 * .65 = 44% overall. For MPPT you get .68 * .77 = 52% overall.

Now, I'll grant you that these are somewhat pessimistic numbers. A lightly loaded inverter will do a little better than 80%. Lightly cycled batteries could do better than 80% (especially if you don't charge them fully, since most of the losses are at the end of the charge cycle, but that carries the risk of sulfating). Some of the energy goes straight from charge controller to inverter, not being involved in charging/discharging the batteries. From a design perspective I can't really go with 'best case' though, or I would have very unhappy customers. Keep in mind too that these numbers do not take shading into account at all yet, and there is no such thing as a horizon-to-horizon unobstructed view just about anywhere (and why is it that off-grid people always seem to live in the middle of a forest?! :blink:).

-RoB-

[Bryan Couch]

Thank you Rob for the numbers and examples! :) I'm getting a hold of the basics now for sure and really finding this very interesting.

Now if I use a 10kW example and we use December numbers since I tend to use the most power from November to January, around 1000 kWh/month (and I thought my family was anything BUT average!! lol)...

In an average December my system produces,
75% * 3.0 kWh/day * 10 kW (system size) = 22.5 kWh/day or 697 kWh for the month grid-tied.
OR
52%*3.0*10=15.6 kWh/day or 483 kWh for the month off-grid.

How's my math? :)

If I were to go off-grid I would need to reduce my electricity usage by more than 50% and even then I would be on a generator when it was cloudy for at least November, December and January. Off-grid is never going to be an option with the house I'm in now.
However if I design and build for off-grid it remains a possibility but the variables are still a little overwhelming right now! I've added gensets to my list of research items along with appliance usages. :nuts:

I just had a thought...
If I were grid-tied and on net-metering instead of MicroFIT could I set up a system to connect and feed into the grid only when I wanted to? What I'm thinking is that the above system would be providing hydro with free power on net-metering because I use around 8800 kWh a year and would produce around 11,400 kWh. But if I could disconnect and dump my excess power into DHW (or ???) I could use the grid to "store" my power from the summer for use in the winter and end up net 0 over a year. No hydro bill AND no production wasted to the grid. Or maybe two separate systems, one grid-tied and the other off-grid. Hydro probably has rules to avoid this. :suspicious:

I guess I've got some more to look at before moving on to passive and active solar heating and solar domestic hot water.

[Rob Beckers]

Bryan, the math is correct (assuming that December has 3.0 sun-hours per average day for the tilt-angle you looked at, I didn't check).

Net-metering works as you describe, it is annual: You can 'bank' the excess from summer to use up in winter, and still come out at zero for the entire year. They won't pay for any excess annual production though, you end up giving that away to your LDC.

Keep in mind though that you will still get a monthly bill with all the fixed fees Hydro has. They don't stop that just because you're net-metering.

Another option is to be (partially) off-grid, but keep the grid-tie connection and sell-back any excess energy to the grid (as net-metering). So, you would have batteries and all that good stuff, make your own power, and if the grid goes down you would still have power (either partial or whole house depending on setup). It can all be done. Not cheap though for something the size of a regular house.

-RoB-

[Bryan Couch]

Well after reading, reading and more reading, searching the net and looking out the window I've learned a lot. I've also spent some time watching the family power usage over the last month and I've come to some small conclusions.

1. Kids waste a TON of power no matter how many times you tell them to turn it off when their done! It seems I may have been misinformed all these years... when you turn on the TV, a light or anything else that uses electricity it CAN NOT be turned off!!

2. November is really cloudy here in Geraldton. We're half way through the month and we've probably only seen a total of 10 hours of sun. The number posted above from Rob of 2.6 sun hours a day for the month is high so far this month. I'm looking forward to the rest of the month being sunny to make up for the first half! lol

3. It's really NOT windy here. I had originally thought wind would be good to offset the solar through the winter. Then I did some reading on it here and over the rest of the net and was thinking it probably would not work well. Then I found this site (http://weatherspark.com/averages/28254/Geraldton-Ontario-Canada) and got a pretty good idea of the average weather etc for Geraldton. It seems pretty accurate and I really like the graphs. :) At 3 or 4 m/s wind is out. :(

4. Back to solar, a lot of what happens here will depend on prices and locations but I'm pretty sure net metering is out. Why give my power generation away for free? Hydro One would NEVER do that for me!! Completely off-grid is out. As awesome as it would be I just can't see it being a good financial decision. We have a big family and because of that a fairly big house. If being tied to the grid is an option it will happen. Maybe partly off-grid, maybe MicroFIT, FIT, maybe just SDHW and floor heat, maybe some combination I haven't thought about yet.

We'll see what happens as I find out more about where we'll be and what our house will look like. Thanks to all of you for the help in understanding this and the extra info! I really appreciate it!

Now I'm shifting my focus to heating, hot water and passive house design. This is really interesting stuff! I'm starting to wish I could get into designing and building energy efficient houses as a second career! Maybe I'll start reading up on that too! :smile1:

[Karen Dick]

Hi all,

We have a solar system on our cottage that is getting old - almost 20 years. Increasingly we have to rely on the generator to back up the water pump and power.

Wondering if anyone has good leads on a trusted solar battery retailer in Ontario?

Also, any consensus on top notch systems out there?

I bought the place 13 years ago with not much knowledge of how it works and never having to replace anything. Just want to shop around and find the best upgrade.

Thanks all!

Karen

[Rob Beckers]

Hi Karen,

Welcome to the forum!
At the risk of sounding forward, my business sells RE supplies (we install them too), so you could talk to me. E-mail is Rob@solacity.com, or give me a call, 613-686-4618.

-RoB-

[Ralph Day]

See this thread for instance:

http://www.greenpowertalk.org/showthread.php?t=19149

If I had to do it again...

Ralph