How best to gain from our PV generation?

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HarmLessSolutions

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#270618 18-May-2020 17:14

Having read detailed inputs on Geekzone regarding Paladin diverters I figure here is the plae to go to for advice on them. We live on a rural property and are planning to install 3kW+ of PV in the near future. We had a 6kW set-up at a previous property but even with purchasing a Nissan Leaf we struggled with self consumption of our generation.

So, we have a 3 year old 250L Rinnai Duplex (twin element) HWC, logfire heating (no wetback) and two 700L chest freezers in our household of two adults. We also have a Nissan Leaf EV with a Juicepoint 7kW charge unit (limited to ~3.3kW due to the Leaf's charge input limitations). The Juicepoint EV charger is on a timer to make best use of Ecotricity's off peak rates from midnight to 7am but as my partner is currently working online from home which is looking like becoming the new normal daytime charging of the EV will probably become the norm. Our current electricity useage amounts to about 700-800kWh/month (~$200/month)

The PV installation will again be more or less ground mounted. Our previous set-up: https://www.harmlesssolutions.co.nz/index.php?route=module/blog/view&blog_id=7

My questions are: Is 3-3.5kW of PV a reasonable and most economically viable size for our situation? How are we best advised to configure the PV/HWC/EV charger to gain maximum consumption of our generation?

The one variable is that a second EV is likely within a few years, probably with higher charging input capabilities, but this could well result in upscaling the EV at that time.

https://www.harmlesssolutions.co.nz/

HarmLessSolutions

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#2488988 21-May-2020 22:53

This video is the case in point where subject matter on EVs morphs into PV (storage) , and back again. Some pretty interesting future technological advances.

Battery Day is Coming!

https://www.harmlesssolutions.co.nz/

HarmLessSolutions

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#2691191 12-Apr-2021 09:41

We're moving towards installing about 5kW of PV as mentioned earlier. This video popped up via a Twitter post this morning which others might find interesting. It pretty much confirms what my research has shown in regard to PV vs solar hot water panels vs heat pumps vs solar diverters. The info is Aussie-centric but still very relevant for NZ.

https://www.harmlesssolutions.co.nz/

traderstu

332 posts

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#2691413 12-Apr-2021 13:48

Thanks for this. Not a lot to add but just wanted to post so that you know that you're not just talking to yourself.

We are embarking on another new build and we hope this will be the last. We have a delay waiting for title so plenty of time to give plenty of thought to solar and plan accordingly. We will be watching this thread with interest.

You touch on the disparity between the prices when buying from the grid compared to selling back to the grid in your blog. If the genius's in Wellington were looking to future proof our electricity supply, in a very green way, they should be regulating the discount that the generaters apply when buying back electricity. There are very good arguments that would suggest this should be a 1:1 ratio. I wonder if they have already figured this out, but are reluctant to implement it because of the backlash they will receive from the generators. The hypothetical Tesla proposal outlined in Battery Day clip (skip to 11.10 for the VtoG stuff) would turn the power supply industry on it's head. Bring it on, I say

Sorry if I have wandered off topic.

afe66

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#2691428 12-Apr-2021 14:06

Also off topic but will get backlash from those who bought electricity shares under previous national coalition.

Mandating 1:1 pricing would result in drop in share price and queue media moaning reports....

Personally I would have though mandating minimum pricing would be great idea.

timmmay

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#2691441 12-Apr-2021 14:13

The per-unit rate a power company pays fluctuates, and I assume it covers all sorts of things like metering not just the power. Agree that a better buy-back rate would encourage uptake.

darkasdes2

429 posts

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#2691508 12-Apr-2021 15:57

timmmay:

The per-unit rate a power company pays fluctuates, and I assume it covers all sorts of things like metering not just the power. Agree that a better buy-back rate would encourage uptake.

Flick's home harvest plan allows you get get the wholesale power rates for the power you feed into the grid. Been great for my parents at the moment with the current wholesale prices.

timmmay

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#2691514 12-Apr-2021 16:04

darkasdes2:

Flick's home harvest plan allows you get get the wholesale power rates for the power you feed into the grid. Been great for my parents at the moment with the current wholesale prices.

That's good. The downside of Flick, as many found a couple of years back, is when there's a water shortage power prices can spike for extended periods.

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darkasdes2

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#2691614 12-Apr-2021 16:53

timmmay:

darkasdes2:

Flick's home harvest plan allows you get get the wholesale power rates for the power you feed into the grid. Been great for my parents at the moment with the current wholesale prices.

That's good. The downside of Flick, as many found a couple of years back, is when there's a water shortage power prices can spike for extended periods.

They have a fixie plan so you can go on that and pay a fixed generation rate but still get the wholesale rate when selling back to the grid.

HarmLessSolutions

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#2739701 6-Jul-2021 13:45

darkasdes2:

timmmay:

That's good. The downside of Flick, as many found a couple of years back, is when there's a water shortage power prices can spike for extended periods.

They have a fixie plan so you can go on that and pay a fixed generation rate but still get the wholesale rate when selling back to the grid.

I had this link included in an email reply I received from PowerSwitch recently in answer to questions I raised in respect to their lack of functionality for EV and PV owners. Some inaccuracies I suspect as we are with Ecotricity - Eco Saver plan (for their off-peak rates for EV charging) and they have quoted us 10.8c/kWh Buy Back rate.

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kotuku4

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#2739713 6-Jul-2021 14:10

You could contact Ken at paladin for advice, and use of PV controller to manage ev charging.

I can see two freezers drawing a fair bit of power.

HarmLessSolutions

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#2739718 6-Jul-2021 14:23

kotuku4: You could contact Ken at paladin for advice, and use of PV controller to manage ev charging.

I can see two freezers drawing a fair bit of power.

Been there, done that, in contact with Grant. We have a Paladin on backorder.

Rearranging our usage to best maximise our consumption during generation will improve the system's ROI. Also juggling items between our three phase supply is planned. Being rural we have a pumped water system so another factor into the mix.

https://www.harmlesssolutions.co.nz/

tripper1000

1619 posts

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#2739728 6-Jul-2021 14:40

We seem to be a more enlightened and technical audience at Geekzone, so you fella's should appreciate this, and understand the flaws in our power system a bit better and ask the people in power the right questions in future.

Regarding buy back rates and whole sale prices, the biggest problem is not with the retailers or Gentailers share holders, it is with Transpower, a Govt owned entity.

The problem is that there is no truth in lines charges with regard to Transpower pricing, and it is causing economic and environmental problems and greater imbalances in the power system.

Line charges are a key component of electricity pricing. Transpower needs to upgrade the grid to handle growing peak demand however it is not billing those causing the peak demand, it is charging on and off peak users equally, encouraging the problem to get worse, because there is no incentive to move consumption from on peak to off peak.

Furthermore lines chargers are also based on consumption quantity and not the amount of infrastructure need to deliver the power. This means that someone in Taupo pays the same lines charges for power being generated 10km away as an Aucklander using South Island power generated 1200km away.

These two problems translates into lousy solar buy back prices because your neighbour buying your power is paying the same lines charges and subsidising the other neighbour buying power from 1,200km away.

If your power company was free to buy your power and sell it to a near-by customer without paying all the lines charges, your solar power would be more valuable.

If Transpower charged truthful on and off peak transmission prices, it would make you solar power even more valuable still.

The net result would be that the free market would encourage solar (without Govt intervention) and that users (domestic and industrial) would start taking common sense steps to move consumption off peak reducing our reliance of fossile fuel powered peaking generators, and reducing N.Z.'s carbon footprint.

This is what is driving Tiwai out of N.Z. - once they pay their lines charges, they are not getting cheap power at all contrary to popular rhetoric. They are paying 14% of all the lines charges in N.Z. despite only using 250km of power lines. Yes they are getting cheap wholesale per KW prices, but they are subsidising Aucklanders lines charges. Meridian can't sell the power to anyone else because the grid can only take the power to Tiwai and not export the power to other consumers so Meridian either gives it to Tiwai cheap, or moth-balls Manapouri. Their shareholders would rather Manapouri earn something than nothing. The Govt does not need to give Tiwai hand-outs, and Meridian doesn't need to give them cheap power - what needs to happen is Transpower just needs to bill per kw per km - or fairly for the amount of network used and the cost to maintain it.

Fair billing by Transpower would encourage solar, reduce N.Z.'s carbon foot print and keep Tiwai working.