Thread: Solar power

Hi Bob,

I just finished posting a long winded post about my recently installed 3.5kw system on the renovations forum. There is good advice on Whirpool, but you also need to filter the responses from those just trying to justify the decision that they made to make them feel better, and also the installers trying to push their business.

My 3.5kw system with an SMA inverter and Canadian (Chinese made) panels came in at $1833/Kw. From my research the Canadian are in the upper end of the middle bunch of panels and the SMA inverter is at the top. I also looked at QCell (German panels) however this would have been around $2140/Kw which was getting a little pricey for my likes.

Without knowing the full details on the panels you had quoted I would think your price is pushing the higher end of the range. I would think around $9k for a higher end middle ground system would be more realistic. For the $11-12k I would be expecting the higher end quality range. The SMA inverter is a good unit and I don't think you will go wrong requesting that.

We have gone an east + west split (7 panels on each). The system hasn't been in long enough to determine a real pattern but the production seems better in the afternoon so far but it may be different closer to winter. The east + west split will give you a good coverage throughout the day (which is good when you are home on the tools), and also offers some protection should you have an overcast morning or afternoon. If you do all east and it is overcast until afternoon you will not generate much for that day. At the moment we are averaging about 15kwh/day but I would expect to see a significant drop over winter.

If you are doing half east and half west it may be worth looking into a smaller inverter. Lets say you have 2.5kw of panels on the east and the same on the west, it is unlikely that at any time in the day you will be generating 5kw (the inverter maximum). When accounting for system losses you may peak at lets say 4kw (12pm-1pm) and as such you can get away with a slightly smaller inverter (saving a few $s). If you get a 4kw inverter and your system has a great day (hour or so) and peaks at 4.5kw then the 0.5kw will be clipped and discarded as your inverter cannot handle it. From what I understand the SMA will have no problem with this, and despite being rated at 4kw can take slightly more. These are just rough figures to give an example. My 3.5kw east + west system peaks at around 2500w from about 1pm and then a slow fall away ..... much less than the 4kw inverter I have.

Your quote also mentions an estimated generation of 7,000kwh/pa. This is around 19kwh/day. You need to consider that this is the average and you will obviously generate more in the summer than winter. If 19kwh is your daily average you will be generating more than this in the summer. The excess that you generate during the summer will be sold back to the grid at a lower rate than you buy from the grid. In the winter then you will be generating less than 19kwh/day and as such be buying power for more than it costs you to generate. Ideally the money you make in the summer will offset your expense in the winter, leaving you square by the end of the year with any luck.

The return on investment is a tricky one and there are calculators online to assist. It helps if you have a few past bills to monitor your fluctuating usage through the year. For our system I was told we only needed 3kw, I wasn't particularly concerned about the return on investment and had a rough idea of what I was happy to outlay for solar, this is why I went for 3.5kw as it was around the figure I was happy to spend. Based on the very early results of around 15kwh/day in summer we easily cover our 8kwh/day usage in the summer, however I think it will be line ball if we cover our 13kwh/day usage in winter. I think in retrospect I perhaps should have gone 4kw however the feed in tariff I am currently on will stop in 2016, at which point the best return is to just have your system covering you day time usage, which I think the 3.5kw will do in summer and winter. Bloody tricky trying to find the balance!

The installation should be to Australian Standards, so leaving out the actually quality of the work, I wouldn't get too hung up on the technical inclusions, it looks like marketing spin. I would be more interested in the electrician taking pride in their work and doing the best job for the site, not necessarily the easiest one to meet the regulations.

At this stage I would recommend you get a few more quotes based on what you have so far. I don't pass myself off as an expert in these matters, just somebody who has recently been down the same path you have taken. Only time will tell if I have taken the right turns on that path!

Cheers

Stinky

Here are some thoughts - more general than specifically anwering your question....
They are suggesting setting up two "strings" - east and west. Sounds like the inverter is capable of processing 2 strings independently. That's good.
Half your panels are producing peak power for half the daylight hours - the other half the rest of the daylight hours. That means you will never get peak power from your entire array. Have they factored that in when they quote you an estimate of 19.3kWh/day? If not, then your amortisation time os longer than quoted....
Secondly, do you have any shadow falling on any of the proposed installation position at any time of the year?
It is worth knowing that the maximum output of all the panel in a string is limited by the output of the LEAST producing panel. That means if just one of the panels gets a shadow and produces say only 50%, the ENTIRE string will only produce 50%. They don't tell you that unless you ask specifically.
In the US and Europe, they are starting to install panels with integrated inverters in EACH panel for that very reason. When one panel get a shadow and only produces 50%, all the other panels can still produce maximum output. I like that and might wait until they are approved here befor expanding my 1kW system. I have some large trees around here.... The other reason I like this idea is that all the wiring is 240V AC - there is no separate DC wiring or fusing required at all. In some countries you can even install them yourself - because each panel can come with a plug on the end and you just plug it into a waterproof powerpoint you have installed for the purpose. Sounds good to me....

Hi All,
Hey, at 68, you can get a lot of Power for your $20000.
My guess wood be that, it wood see you out.
A bit different for Sir Stinkalot, being a younger person.
Might as well spend it on something else, & have some good times with it.

G'day Bob,

That system sounds pretty much what I have, although I only have a 3kw of panels. I went for the 3kw panels and a 4kw inverter, but what was delivered was a 5kw inverter.
The reason I went 3kw with a 4kw inverter was a future plan for upgrading with another 1kw down the track. As it turns out, I probably won't upgrade, but the interesting thing is that the panels will often push nearly 4kw as they are. The most I've seen on the inverter has been a surge of 3.9kw
Matched inverter and PV sizes will be current limited to whatever the inverter rating is... If I had a 3kw inverter, that's all I'd ever get out of it and the extra input would be lost, so the inverter pushes out whatever the PV's are pushing in.

I have an SMA 5kw TL inverter with 16 Suntech 185W monocrystaline panels. All up (around January 2011) it was nearly $19k with $6.3k REC discount for a grand total for me of $12.6k

My panels all face North, so I get a good chunk of sun during the day. During the longer summer days, I start generating at around 6:30am and finish at around 8:30pm, a good long stretch and I can produce 24kwh+ in that time, but usually around 20 to 22.
Winter is the killer and I have generated down to 3kwh in a day, but that's a dismal Melbourne full of clouds and rain. As you're in Brisbane, you should get a better exposure to the sun than I do, although, the PV's work best in full sun on a cold day.

You're correct in saying there's two channels in the inverter. I think the 3kw SMA's and up have 2 channels (mine does) so it's electrically easy to connect panels to it. I only use the one channel, so the other one is left idle.

As Joe mentioned, everything depends on full production of each panel, and because of that, I often get up and wash the bird crap off the panels. I've now run a fishing line across the highest point at the ridge line of the roof, and that seems to have stopped them pooping on the glass.
Another thing to watch is that the power companies (bless their little socks, my favorite organisation!) will charge you extra for Time Of Use Kwh because you have solar. I used to pay .22 per Kwh, but now it's .36 per Kwh, but I also get .66 per Kwh feedin tariff.

So far, I'm not in front and I doubt ever will be (my dad makes 8 cents a day on his system). I've reduced my winter bill from $900/quarter to about $350/quarter, so that was my plan all along.
So far, I've generated over the last 2 years, nearly 9,000kwh of juice.

Hope this helps

Hi John,

Could you please clarify the peak output of your system. From the sounds of it you are saying that you have had a peak generation of 3900w from 2960w worth of panels??? A 25% increase over the panel capacity (whilst ignoring system losses) is huge. The system must be very happy as it seems to be pulling some big numbers, especially in Melbourne. I know north facing is ideal and it is interesting to see real life results. (By the way you did a great job on that brass stamp that was posted on the forums the other day!)

It is interesting to note how the cost of the system seems to be directly related to the feed in tariff available at the time. Your system is now a touch over two years old and it was costing $4,200/Kw, however you got the impressive $0.66/kwh feed in tariff. As I mentioned my system purchased late last year is around $1,800/Kw, although I only have a $0.26/kwh feed in tariff. For the sake of simplicity I have not really taken into consideration different locations and brands used. Whilst I am sure that the cost of panel manufacturing would reduce over time, and panels should become cheaper with higher quantities, that is a huge drop ($2,400/Kw) that seems to align with the reduction in feed in tariff. I noticed a similar trend when researching on Whirlpool. Shortly following the reduction, or any change, in the feed in tariffs, the cost of the system also took a big drop.

There are many variables when trying to calculate the return on investment, but the current trend with the lower feed in tariffs is to just get a system to cover your daytime usage as there is little point paying big dollars for additional panels only to be able to sell back to the grid at $0.08/kwh. The new recommendations are to only size your system to cover your day time use, shift as much energy consumption (washing machine / dishwasher etc) to the time of day when you are producing your own power, in an attempt to reduce how much power you are buying at night.

With the higher feed in tariffs the recommendation was to go as big as you can due to the good price you were getting selling back to the grid during the day, on the understanding that you could generate the equivalent of your full days usage during the daylight hours, covering the cost of the power drawn from the grid at night. In theory this all sounds good, until you factor in what was an unknown at the time, the huge reduction in upfront system cost when the tariffs were reduced.

It would be interesting to go back and run the ROI figures on those who choose to put in the very costly (sometimes up to $20k) systems to try and claw as much back with the FIT, against those with the lower FIT but the significantly cheaper upfront system cost.

There are companies around here currently offering higher feed in tariffs, more than the standard Government grants. Its not until you read the conditions that you find you are either paying too much upfront for your system, for the benefit of a higher trickle back return, or the company is taking a chunk of what your system is producing so you may only get the higher tariff on half of your daily generation ...... all just scams to try and muddy the water.

No real point to my ramblings except perhaps that with these rebates and schemes it is difficult to tell what you are actually paying for and if you are getting value for money.

Just a few things,
1. If you ever meet someone from Inspire Solar, tell them to go to hell, and never ever deal with them
2. Sunnyboy inverters are good inverters
3. It means very little whether they give you 10 yrs, 25 yrs or even 100 yrs warranty. The question is will they still be in business next year
4. How the hell do you use 20kwh a day? I have 3 kids and we use less than that.

How do I know all these? See pt 1.

Originally Posted by Sir Stinkalot

Could you please clarify the peak output of your system. From the sounds of it you are saying that you have had a peak generation of 3900w from 2960w worth of panels??? A 25% increase over the panel capacity (whilst ignoring system losses) is huge. The system must be very happy as it seems to be pulling some big numbers, especially in Melbourne.

Yeah, I'm pretty happy with the system in general, but if/when I move from here, I'll probably look at wind generation instead.
I confirm those numbers. The only way I can see it happening is the PV cells are rated at X watts for Y lumens (lux, brightness units.. whatever) of the sun, so when it exceeds the rated conditions, you can get a little more. It's most noticeable on patchy clouds in the day. When the sun first winks out from the clouds, there's a big surge, but only for a couple of seconds. Everything still averages out as under the 2.9kw ratings over time, but it's interesting to watch the LCD readings on the inverter go sky-high for an instant.
And as Wongo said, the SMA's are good inverters. Europe have put a lot of tech into this sort of stuff, and they've got everything pretty good now. Another good thing with SMA's (maybe others too, I don't know) they're on blue tooth, so you can hook up and get all the data from the computer.

I was speaking to the electrician that came out to see my installation before the system went in, and he was saying that in Germany, there's houses where the roof is made entirely of panels! That's some serious power generation!

(By the way you did a great job on that brass stamp that was posted on the forums the other day!)

Thank you

I am frankly amazed by the entire complexity of these adventures. Seriously.
Why are you doing these things? I hope that it is more than just a Greenie Get Off The Grid thing. If you live outside the grid, so be it.

I need 1kW for possibly 10 hrs as we can have as many as 60 power interruptions per day (the girls in the grocery store quit counting at 60.)

I have one 75W panel and 4 x 6VDC deep cycle batteries. Ganged up properly, that's 12VDC to drive my 120VAC inverter. My compressed wood pellet stove eats maybe 500W and the 3 motors are very fussy to eat pure sine wave. I discovered that a fast cycle charger was better than a bunch of solar panels which do not work well for me at night.

Originally Posted by Robson Valley

I am frankly amazed by the entire complexity of these adventures. Seriously.
Why are you doing these things? I hope that it is more than just a Greenie Get Off The Grid thing. If you live outside the grid, so be it.

I need 1kW for possibly 10 hrs as we can have as many as 60 power interruptions per day (the girls in the grocery store quit counting at 60.)

I have one 75W panel and 4 x 6VDC deep cycle batteries. Ganged up properly, that's 12VDC to drive my 120VAC inverter. My compressed wood pellet stove eats maybe 500W and the 3 motors are very fussy to eat pure sine wave. I discovered that a fast cycle charger was better than a bunch of solar panels which do not work well for me at night.

Well, I'm not sure about everyone else, but when my power bill is around $1200+ per quarter, I figure maybe I should try and reduce it some more. I suppose I could use the wood burner for heating again, but at $190 per meter, and using up to 10 meters per winter, it's pretty expensive too.
And before anyone picks me up and says to use off peak, etc... I already do as much as possible. Unfortunately, dinner time is on peak rates and I like to eat at dinner time. Work time is during peak time too, so with two machines, lights, 2 compressors, 3 vacuums and various other things running, it all adds up too.
Ah, and I use gas for the stove top and HWS... at $200 a bottle, 4 - 5 bottles a year, it gets up in cost too.

$1200+ per quarter! What about reducing it by using less?

Originally Posted by Wongo

$1200+ per quarter! What about reducing it by using less?

Sure... I could turn off the fridge and freezer, shut down the septic system, work in the dark downstairs. I could even turn off the one and only light I have on at night while I watch TV.. hey, I could turn off the TV too, that's not worth the trouble of hitting the remote.
The computer is on all day because I need it for my work... usually shut down at 7pm or so.

Unfortunately, I'm at a bare minimum at the moment without going to the equal of living in a tent. As I say, there's 3 motors in the septic system, a fridge/freezer plus an extra freezer in the laundry. Interestingly, it costs $150 a year to run smoke alarms!
We run the dish washer at 5 in the AM (off peak time), the washing machine mainly on the weekends (off peak time) and the lights in the workshop are on a PIR so they turn on when I'm there and off again when I leave.

The oven sucks up a chunk of power, but good food comes out of it
The reverse cycle heater takes about 2 to 3 amps to run during winter, so it's also a big user.

It is what it is... that's why I got a chunky PV system

I just did the maths on usage for the septic... $200 a year JUST to run the control panel without the motors ever coming on...

Sure.

We have a fridge, we don’t work in the dark, we have a TV and a remote control. We have an oven. We have a computer on around 10 hours a day. We have 5 members in the house. We live comfortably and our bills are only around $400 per quarter. How do you explain that?

Originally Posted by Wongo

We have a fridge, we don’t work in the dark, we have a TV and a remote control. We have a computer on around 10 hours a day. We have 5 members in the house. Our bills are around $400 per quarter. How do you explain that?

I can't, but if you can... I'm all ears
You get no argument out of me on my usage, it's big... That's why I went with a PV. Not because I'm green (which I am a bit) but because my 3 phase costs a bomb to run and the kwh charges seem to go up every time I sneeze.
I was just answering the question asked of why bother - that's why I bother

Originally Posted by Robson Valley

I am frankly amazed by the entire complexity of these adventures. Seriously.
Why are you doing these things? I hope that it is more than just a Greenie Get Off The Grid thing. If you live outside the grid, so be it.

Now while I may or may not think solar is the smartest thing in the world and I do wish the goverment would stop kicking in so much of "my money". "I" effectively have solar as "I" paid for half of my neighbors....... though any return will go to him . lol*
Would you be happier if they spent their money on an new 4x4 or big screen tv?

As I understand it these systems can't island** so they wouldnt solve your problems anyway.

I doubt it will really paid for itself in 7 years Bob. Report back


Stuart

*granted the subsidies arent nearly as generous as they once were.

**its not that it cant be done. I believe islanding has been excluded from the subsidies.(anyone?)