Fill and Albie's Grid-Connect Photovoltaic Array

(Generating electricity from the sun)

PV Array

Generation Summary:   (Updated 14 March 2014)

Turn-on Date:
1 March 2012
Total Energy production:
15887 kWh = $3,972                       
Average production per day: 
21.4 kWh (Target: 20 kWh)
Maximum produced in 1 day:
36.4 kWh
Highest peak power:
5.1 kW

See Graphs of results here:

Hourly output compared for 5 selected days in March 2012

Daily output for 2012 Daily output for 2013 Daily output for 2014

Daily Output Graphs for each month separately:

January 2013 848
January 2014

February 2013 771
February 2014
March 2012 657
March 2013 693
March 2014

April 2012 698
April 2013 511

May 2012 552
May 2013 480

June 2012 384
June 2013 400

July 2012 420
July 2013 555

August 2012 441
August 2013 438

September 2012 637
September 2013 674

October 2012 796
October 2013 701

November 2012 863
November 2013

December 2012 810
December 2013

Comparison from year to year

Project Started: November 2011:  (For Latest Posting,  click HERE)

We've been thinking about this for some time now, and the last time we looked at it, it was FAR too expensive.  But prices have come down now, and we thought it was worth looking at again.

We've done an investigation, and you can look at the document HERE
There's also a spreadsheet with some calculations HERE

This is all to do with Ethical Investment of our money.  We could put $25,000 in the bank, where we would earn around 5% interest, but who knows what the bank will invest it in! (Arms? Coal-mining? Factories in China?...)  A solar electricity generation facility, on the other hand, seems to be an environmentally positive scheme to put some of our money into.

We would most likely use a "ground-mount" system, with 26 solar panels (190Watts each), giving us a total of around 5kW generating capacity.  Assuming 4 hours of good sunshine per day on average, that's 20kWh (20 "units") of electricity generated per day.  (5kW x 4hrs = 20kWh)  As a comparison, we currently use around 15kWh per day.  (...currently....  haha)

We've decided to use local people for building the array, connecting to the electricity grid, and generally getting everything up and running. (Rather than getting an Auckland company to do the whole thing for us in one fell swoop).  The idea is to find out what is involved in doing this, and to share our experience with others who are interested in doing something similar.
Our overall Project Manager is Paul Stocker (Azimuth Renewables), Electrician Rainer Huebler, and Builder Keith Patchett.  I (Albie) have been seconded onto the team as chief hammer-and-nails passer and general dogsbody.

What we've found out so far: (November 2011)
Update December 2011
The Specifications are finalised!
Update January 2011
Holes, holes, and more holes!  Some of our friends at a hole-digging party!  There were 24 holes to dig, as well as a 17 metre trench, 600mm deep.  There were some seriously sore hands and muscles afterwards.


Nothing much happened for a couple of weeks, then it was all go....  Concrete mixed, posts dropped in place, beams bolted on, rafters nailed and Z-nailed on.

Here are our main helpers: (Rhiannon and Charlotte)


The rafters go on:   (The panel in the background is for our Cottage Central Heating project, which you can find HERE.)

...and now the Grace Solar mounting rails for the panels.

Grace solar rails

We've also made a change to the wiring arrangement.
The current thought is to have FOUR strings of 7 panels each (28 panels, as before), but with all four strings wired in parallel.
This gives us a single pair of output wires carrying 20 Amps at a voltage of between 270 and 320V.  There will now be only one cable in the trench instead of two, which will be cheaper.  The cable is 10mm sq. cross section per conductor.
You can see a circuit diagram of this arrangement HERE.

Update 1 February 2012:
The inverter hasn't arrived yet.  Hope it comes soon!  The structure is almost ready for the panels and wiring.
We've received approval from Network Tasman to connect to their network, and we've booked a technician to install the Import/Export meter on 1 March (or earlier, if we're ready and the technician is available).  We hope to have all the panels and wiring installed this month.

Update 4 February 2012:
The panels are up!  (That's Russell looking very pleased!)


A view of the reverse side.  There's lots of airspace to keep the panels cool.  They work better that way.

Panels (reverse side)

While this structure was being erected (Brian Leetch calls it our "huge erection"), we've started building our new hot water system for the house.  We've called it "Hot Water 4", and you can find it if you go back to the main page of projects HERE.

Update: 23 February 2012
Pause for thought........
A number of folk have passed through here in the past month or so, looking at what we've done so far, and passing comment (mostly good).  A common theme, though, has been a sort of uncomfortableness at the length of time it will take for the system to "pay back" a reasonable return on the investment.  It is a 40-year project, after all.  I explained that we were doing it not for ourselves, but for our future generations, but that didn't entirely put away the disquiet for some people, I could see.  But then one person said "why do you expect any return on investment at all? Shouldn't you be doing this anyway, regardless of whether it pays back or not?", which turned on a little light somewhere in my head!
(If you'd like to read my subsequent thoughts on this, you can find them HERE.)

Update: 26 February 2012:  Council determines structure "Not a Building"
We applied to the TDC for an "exemption from building permit", and we've just received word that we don't need a building permit, nor do we even need to apply for an exemption!  The paper says that if it were a building, it would comply because we have built everything to the NZS 3604 building code standards.  However, they don't have a building defined which looks anything like the structure we've built, so we can't (and don't need to) apply for an exemption from the building permit process either.  The Building Consent Officer has recommended refunding the fee we paid for the application for exemption.
Isn't that fantastic?  So it seems that the onus is on us to ensure that the structure is strong enough to support our solar panels, and not be blown away by the wind.  NZS 3604 building code standards are more than sufficient to ensure this.
To summarise the materials used in the post-and-beam structure: (You can see photos of the structure above)
- Posts are 100x100mm H4 treated, concreted into the ground in holes 600 deep, 410x410 wide. 12mm reinforcing rod bored through the posts in the concrete, so that they can't pull out.
- Beams are 200x50 bolted to the posts with 2 x 10mm galvanized bolts at each post.
- Rafters are 150x50, Z-nailed to the beams with 2 Z-nails at each end
- Diagonal stays are 150x50, one at each end of the structure.
- Durability of structure is greater than 50 years.

Update:  1 March 2012:  Turn-On!!
Everything was ready, the sun was shining, and the inspector from Vircom arrived to install our import/export meter, check the system, and give us the go-ahead to turn the inverter on for the first time.
He was most impressed with the quality of the workmanship (he said this a number of times!), and it all passed inspection with flying colours.  Good work, Paul, Rainer and Keith!  (and Albie too - I passed the right nails and hammers at the right times!)

Here's our quality controller (Fill) looking pretty pleased with the inverter, secretly hoping that Albie isn't going to press a button that he shouldn't....

Fill, Albie and Inverter

On this first half-day of operation, the peak power went all the way up to 4kW, even though the sun was well past the midday peak.  All looks good.

Update: 2 March 2012:  I spoke too soon!
We can't make our datalogger work.  It's a Delta Solivia Gateway device, which is supposed to connect between the inverter and our computer via an ethernet cable (so the blurb-sheet said.), and tell us everything we need to know about how much energy is being produced, with graphs and so on to prove it.  It turns out that it isn't designed to connect to a stand-alone computer, but rather via a broadband router to an internet "Cloud Database", and then we can look at the data using any internet connected computer anywhere in the world.  Fancy, huh!  Trouble is, we don't have broadband here, only dialup.  And another little hitch is that the computer you use to view your data on the "cloud" needs to have Microsoft Silverlight installed, or else it won't work.  That rules out most internet cafes, all Mac computers, and all Linux computers.  So there.
So we contacted Solivia who were very helpful, and suggested that we purchase a Solar-Log 200 datalogger, which they assured us would do the job.  Trouble was, it was going to cost us $500!  So we decided that in the meantime, we would look at the Inverter display ourselves once a day, and write down how much electricity it had produced in that day.  Thus saving ourselves rather a lot of money.

Now we'll let things settle in for a while, and then give you some details on how the beastie performs.

Update: 10 March 2012:  We're an Electron Factory!
Everything is looking very good.  Our 25c datalogger has been working flawlessly, and will continue to do so until it runs out of ink, or we run out of enthusiasm for writing down a couple of numbers every day.  :)
Here is a spreadsheet showing the hourly Power (in kW) for a few days in March.
Here is a spreadsheet showing the Total Energy produced (in kWh) for each day in March.
Pretty cool, huh!

Update: 14 April 2012: First MegaWattHour generated
We've just done 1000kWh - that's MEGA! (after just 45 days)
Isn't it strange how 1MegaWattHour sounds so much more impressive than 1000KiloWattHours?
That's about 2 minutes' worth of the Cobb Power Station we've saved.  Actually, that's quite impressive - have you ever stood next to the pelton wheel runners at the Cobb while they're full on?  You can hardly hear yourself think!

We've also had another "First"! - Our first NEGATIVE electricity bill arrived, with a credit balance of $75 on it.  This is after paying our line charge as well, so we're pretty chuffed!  (Meridian asked us how we wanted it paid - we chose direct credit into our bank account.  Perhaps we should have asked for a cheque, then we could have framed it!)

Update:  22 May 2012:  This is NOT "FREE" electricity!

A few people have said to us how lucky we are, to have all this FREE electricity for years to come! (and to be able to use as much as we like and not bother about the cost...)  And, to be absolutely honest, we have caught ourselves once or twice being a little less than frugal because we're generating it ourselves...
In fact, it's more like a "Pre-pay" system.  We've pre-paid $25,000 for our future electricity requirements.  (And we've withdrawn that money from our term deposit, so we're losing interest on the deal too.)
If we're frugal with our electricity use, then that $25,000 will last for many years' worth of electricity use, but if we're not, it will get used up quickly.  So generating our own electricity does NOT remove our responsibility to use electricity wisely.

Footnote:  Meridian Energy have abandoned their plans to dam the Mohikinui river (YAY!)  But what is annoying is that they give "opposition to the dam" as the reason for doing so.  In fact, they should (could?) have said that they are abandoning the project because of potential damage to the unique environment and animal life there. (That's why there has been so much opposition in the first place!)  Meridian have missed a great public relations opportunity.  Pity.

Further footnote:  If everyone in NZ turns off lights and other appliances when they aren't needed, the electricity saved will be more than enough to compensate for the Mohikinui dam! (I read that somewhere.. I wonder if it's really true?)

Update 26 August 2012:  We've generated 3MWh!
We've just passed the 3MWh mark, and it feels pretty good.  Winter hasn't been wonderful for generation, really, so this milestone took a long time coming.

Our August figures show an average of less than 15kWh per day, but we still think we're on track for 20kWh per day when we've had spring and summer sunshine.  We'll see.

Update 10 October 2012: 4MWh generated.
We've passed 4MWh now, and that's about $1,000 worth of generation.
The system has performed flawlessly so far, except that we still don't have an automatic data-logging system.  We rely on the 25c ballpoint pen which we use to record daily output.  We'll have to find a way of logging on a PC sometime soon.

Latest Posting:

Update 23 July 2013: 10 MWh generated.
Quite a lot has happened since October last year!

Meridian energy have changed their buy-back rates from 25c per kWh to a tiered rate.  As from December 2013, they will pay us 25c for the first 5 kWh per day that we sell them, and 11c for anything above that.  For us that works out at an average of around 17c per kWh.  Bummer!  It seems that they are discouraging people from generating any more than they consume.  The more you generate and sell, the less you get paid per unit.

Of course, this makes it more complicated to work out the financial viability of the project, because the income per unit varies depending on how many units you sell.  But if you're not too worried about "payback" (see my earlier note on 23 February 2012 ) then as long as the cost of production is no  more than the export rate per kWh, it's fine - you're still doing a very good thing for the planet without making an actual financial loss.

Cost of Production - what's this?
It's quite interesting to look at the project from the other way round; i.e. to see what it's actually costing to produce each unit of energy, based on the purchase cost and loss of interest cost, over the lifetime of the project (around 30-40 years). 
The purchase price of our system was $25,000. 
For a term of 35 years, that's a cost of $714 per year.
Interest:  Say you took out a loan of $25,000 for a period of 35 years, at 4% interest per annum.
This means you'd pay 4% of $25,000 (=$1000) interest in the first year
and you'd pay 4% of $24,000 (=$960) interest in the second year
and you'd pay 4% of $23,040 (=$922) interest in the third year..... and so on.
The total loss of interest on the capital thus works out to around $19,000 (I worked this out on a spreadsheet)
Thus the total cost of the system, over 35 years, is $25,000 + $19,000 = $44,000
That's $1,257 per year.
Now, if we produce 20 kWh per day (which seems very likely), then that comes to 7,300 units per year.
Therefore the cost of production per unit is $1,257 divided by 7,300 units, which equals 17c per unit.
But 17c per unit is TERRIBLE!! ..... isn't it?  Well, no, it isn't really.
At the moment, with Meridian paying us 17c per unit (is there a coincidence there?) we're not making any profit on what we sell them.  But for every unit that we consume from our own generation, the price is fixed at 17c for the next 35 years - and we can't say that about the retail cost of electricity in the next 35 years, can we?
So we're still all smiles.

Alan's amazing DataLogger!
Our friend Alan Mulholland has made us a little interface box which goes between the USB port of our computer and the RS-485 port on the Delta Inverter, and has written a little program which talks to the inverter and downloads all the data in it's memory.  Then it stores the data in the form of an Excel CSV spreadsheet on the computer.  Now I can run that program any time I like, to record what the Inverter is doing.

The computer I use for this has a neat little feature which lets me tell it to start itself up at a particular time every day, so I've set it to do this at 4pm.  And I've put Alan's little program in the Startup folder of the computer, so his program runs automatically when the computer starts up, and records the data.  After this, the computer shuts itself down automatically, and another timer on the mains socket turns the computer off completely. (Until 4pm the next day...)

Then, once a week or so, I collect all the data together, and update the graphs and summary up at the top of this page (HERE)  Do have a look at the new graph, at the bottom of the list of graphs, called "Comparison from year to year" - it's looking quite interesting.

CU next time!

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