3kW Grid Tied Solar PV: Watts and Warts.

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135 posts

Master Geek

#1435251 26-Nov-2015 14:30

My 4kW system was switched on and the end of June, and has generated 2.03MWh since then, an average of 13.4 kWh per day. Not too bad for Christchurch.

You can check out the performance here:
https://enlighten.enphaseenergy.com/pv/public_systems/WbyY671422#.VlZJ__Ezhqs

I went with micro-inverters as I have 3 phase-power and this allows the 15 panels to be split over the 3 phases.
Enphase are launching battery storage soon, I am quite keen on this.

Jase2985

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#1435317 26-Nov-2015 15:47

what sort of temps can you go to in your HWC? i know most of the thermostats go up to 70deg but if using a separate supply from your solar can you get them hotter?

SumnerBoy

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#1435324 26-Nov-2015 15:53

My element thermostat is set to 60 (i.e. electric boost element in the middle of the cylinder to only heat the top half - only two of us in the house). The PV diverter will heat until the cylinder is 65 (via the element in the bottom of the cylinder to ensure the whole cylinder is heated). And the solar HWC controller (via evacuated tubes) will heat it to 80 before shutting off the circulating pump.

After this hot weather in ChCh the cylinder is currently sitting at 79 degrees, top to bottom!

Jase2985

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#1435346 26-Nov-2015 16:27

so you have PV and Solar water :)

so i guess you could use the solar PV to heat the tank to 80 instead of importing power to do it

SumnerBoy

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#1435387 26-Nov-2015 17:00

Yeah I did consider that but decided I would be better off exporting any excess and get the credits, albeit reduced, rather than heat the cylinder beyond what I would be heating over night.

Jase2985

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#1435396 26-Nov-2015 17:12

yea, and you you have both it makes sense

if you were to start from scratch would you do both or just pick PV?

mattwnz

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#1435404 26-Nov-2015 17:27

Jase2985: yea, and you you have both it makes sense

if you were to start from scratch would you do both or just pick PV?

I was told that the new pv panels and reduced cost, of them, that it is now cheaper to use PV panels. Especially as some of the solar water panels have a limited life. I was told this by a company selling PV panels that were hooked into a hwc, so how correct that is I don't know. The other way you can store electricity as heat without using a hwc, is having electric in a concrete floor slab, and the slab releases the heat during the night to heat the home.

SumnerBoy

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#1435407 26-Nov-2015 17:33

Yep I was told the same thing by the guys who installed my PV. And I would definitely drop the solar hot water if I had my time again. The circulating pump will fail eventually and will be a pain to replace, cos of where it is. PV is nice and simple, just cabling. And as Matt mentioned you can use it for all sorts, rather than just hot water.

Porboynz

110 posts

Master Geek

#1435412 26-Nov-2015 17:47

k1wi: Hey Porboynz,

It's now two years since your installation and another winter since your last update. How are things going with your set up?

It seems to be pretty common for people to start out full of gusto with their solar set up, but less common for them to continue with long term updates. I guess that's largely because things get a little cyclical after a 12 month period, but the scientist in me would really appreciate another check in with how things are going!

Have you made any further changes or adaptations? Is this year's production pretty much in line with last years, or has there been a substantial variation year-on-year (climate or hardware related)? Any hardware failures or maintenance requirements?

A non-profit committee I'm on is shortly going to be voting on what will likely be a 30KW array, complete with federal subsidies and state SRECs (it's located in the US, but at a similar corresponding lat), so I'm especially interested in longer term experiences.

Thanks in advance!

You are right, some apathy has set in as the PV solar birthday of 14th October came and went and I did not notice, probably because everything just works. No issues or failures but yes I have made a modification same as SumnerBoy in response to the slashed export rates now available. I fitted a PV Router about 6 months back that diverts any surplus generation into my HWC. This increases my daytime usage and acts as a sort of aqua-battery.

I have not compared my power bills this year as yet but here are a few updated facts after last years 1st 12 month report:

Situation:

3kWh PV array consisting of 12 x 250 W Renesola panels
3kW Enasolar Inverter, Made in NZ and recommended
North facing concrete tile garage roof at 17 degrees pitch
Owl Intuition power monitoring web connected gateway
Kiwibank Renewable Energy loan for $12k, got my first $800 rebate last month (Received 2nd $400 rebate in Oct 2015)
Existing 2 flat collector solar hot water panels and 310 litre HWC
Understanding wife (still!)

Data:
12kWh Average daily generation to Oct 2014, 11.8kWh Average overall to Nov 2015
4409kWh generated during 4124 hours of sunshine to Oct 2014, 9187kWh generated during 8807 hours of sunshine to Nov 2015

I'll try and post some more results when I get some more time.

mattwnz

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#1435437 26-Nov-2015 19:02

Does anyone have any experience for PV Laminates, such as the one on this page, and how efficient and durable they are? http://www.metalcraftgroup.co.nz/products/solar-panels/products/pv-laminates/

Aredwood

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#1435691 27-Nov-2015 00:19

richms: Im about to pull the trigger on a solar city install at home. Paying outright for it not the one where I just buy the power.

Anyway, this is in the terms and conditions.

11. CARBON
.1 We retain the rights to any carbon credits accrued through our providing
Services or Goods to you, whenever they arise during the lifetime of those
Goods.

Which seems odd since I am buying outright. Is this the norm for solar installs? Whats the downside?

This sums up everything that is wrong with carbon emissions trading. As that company will probably just add up the amount of solar power generated from all of their installs. And them claim that that power represents electricity that was not generated by fossil fuels. And then try to sell carbon credits based on that.

Yet in NZ the amount of fossil fuels used for generating power varies all the time. So that combined with the varying solar output makes it almost impossible to calculate how much carbon was prevented from being emitted. And the there is the emissions caused my making the panels, transportation, and installation. How long will that take to be "paid back"?

mattwnz

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#1435693 27-Nov-2015 00:24

Aredwood:
richms: Im about to pull the trigger on a solar city install at home. Paying outright for it not the one where I just buy the power.

Anyway, this is in the terms and conditions.

11. CARBON
.1 We retain the rights to any carbon credits accrued through our providing
Services or Goods to you, whenever they arise during the lifetime of those
Goods.

Which seems odd since I am buying outright. Is this the norm for solar installs? Whats the downside?

This sums up everything that is wrong with carbon emissions trading. As that company will probably just add up the amount of solar power generated from all of their installs. And them claim that that power represents electricity that was not generated by fossil fuels. And then try to sell carbon credits based on that.

Yet in NZ the amount of fossil fuels used for generating power varies all the time. So that combined with the varying solar output makes it almost impossible to calculate how much carbon was prevented from being emitted. And the there is the emissions caused my making the panels, transportation, and installation. How long will that take to be "paid back"?

I wonder how they could do that, because surely they would have to prove that the system is still working and generating power. Also they would have to know how much power it was actually generating. The only people who would know that would be the home owner, unless they are feeding back the logs back to the installation company. IMO, the homeowner should be getting the benefit of the carbon credits, as they are the ones who purchased the system outright, are housing the system on their property, and are covering any associated costs with it, including covering depreciation , repair and replacement costs in the future.

wellygary

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#1435719 27-Nov-2015 06:54

yeah, although the numbers will be pretty small,

I saw a paper that estmated NZ's electricity carbon intensity is 100gm per KWh ( over a year),

So for example SQLgeek's 4KW install that generated 2MWh over 5 months, would generate 200Kg of carbon savings over that time.
Even if you triple it for the annual amount you are at 600Kg or less than one Carbon credit per year ( I think credits are currently about $8NZD each )

richms

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#1435721 27-Nov-2015 07:07

The thing is most of their installs are the free ones where you buy the power off them at a rate that is actually more than I'm paying at the moment. But they say is fixed when grid power will be going up.

Also means that I would get nothing out of it for unused power whereas at least owning it I would get a tiny amount from selling it to the power co. They have a monitoring thing that charts performance etc of it.

Reason it concerns me is that if ever I wanted to claim a carbon neutral business etc I can't if they are already claiming the credits for something I own.

There's a few other things in the terms that are clearly for the solar zero plan but I can't get it looked at for a while so may just get a price from vector.

Richard rich.ms

fortydayweekend

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#1436125 27-Nov-2015 15:38

richms: The thing is most of their installs are the free ones where you buy the power off them at a rate that is actually more than I'm paying at the moment. But they say is fixed when grid power will be going up.

Also means that I would get nothing out of it for unused power whereas at least owning it I would get a tiny amount from selling it to the power co. They have a monitoring thing that charts performance etc of it.

Reason it concerns me is that if ever I wanted to claim a carbon neutral business etc I can't if they are already claiming the credits for something I own.

There's a few other things in the terms that are clearly for the solar zero plan but I can't get it looked at for a while so may just get a price from vector.

Whichever way you go, don't count on the variable price necessarily being 25c and going up - the EA has just said they want fixed charges to be higher and variable costs lower. The example they used a couple of weeks ago was more like 17c / kWh.

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