Solar options for home in 2022.

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212 posts

Master Geek

#3283334 17-Sep-2024 21:24

dantheperson:

Yeah, that's real missed opportunity. Some jurisdictions did standardise a communication standard, so you can buy home energy monitors and the like that talk to the smart meter to get realtime data. The greens were pushing for that here when the smart meters were about to rollout, but of course our solution was that 'the market' was best placed to make any decisions about that.

Yes, our power system is yet another market failure.I threw some old paper work out the other day including power invoices from pre millenium: 12 cent peak and 4 cent off peak ! And no power cuts !

The ghosts of 1984 cast a long shadow - without proper regulation markets deliver poor outcomes as we repeatedly see here in NZ (think power, food, banks, transport etc), failing to deliver innovation or low prices.

Unfortunately I've had to pay to get my own metering gear installed, which is undoubtedly not as accurate as the certified meter which is used to bill me. However I really like having access to the realtime data, which I'm now starting to use to move some loads to better parts of the tariff for my plan. I've discovered OpenHAB, which has some very cool integrations.

If you are interested in the meters then head over to iammeter.com

The other gear I'm looking at is Velbus for automation. Interestingly in Belgium where they are based, the tariff you pay within a month is based on the maximum power drawn in that month (to a 15 minute window). I can see why the grid operators want this to smooth out demand, but without decent automation this would be crippling for most consumers.

(Edited to add notes re market failures.)

Otautahi Christchurch

mentalinc

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#3283342 17-Sep-2024 21:59

I've found a house nearby has a weather station that is reporting the "solar radiation in w/m²"

If I work out the planned panel count and the area of each panel, do I multiple those together then the 22% efficacy to get a real world expected solar production?

e.g.
24 panels, 1757mm x 1134mm (so call it 1.99m² per panel) so 47 m² of panels..

Then the hourly w/m² x 0.22 to get the expected watts x 47?

Does this work out right?

So 10am today had 752.7 w/m² at a reading at a point (reading every 5 mins), so end up with 7,782 watts? 7.7 Kwh?

Does this makes sense?

I can then take this and apply it to the wider data set to get an expected generation per day?

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fastbike

212 posts

Master Geek

#3283359 17-Sep-2024 22:59

mentalinc:

I've found a house nearby has a weather station that is reporting the "solar radiation in w/m²"

You need to account for time of year, azimuth/north orientation, and panel tilt.

I used the Niwa Solarview website which gives an average of the insolation per sq m over the last ten years for a given location/azimuth/tilt. This gave me figures for each of the 12 months which I could use to estimate a likely 12 month insolation per sq metre.

I then calculated this for a 49 sq metre array (26 panels) and multiplied by an estimated efficiency (16.4% based on theoretical production times actual insolation). This gave me an annual total of around 12MWh p.a.

Later modelling based on an actual installation close by (adjusted for azimuth/tilt/size) showed actual production for the last 12 months of ~ 14MWh p.a. This equates to around 18% efficiency.

So to cut a long story short, get the 12 month cummulative figures from Niwa for your site, add them up. Divide by 12 and then multiply by 365 to get a daily average. Then multiply by the efficiency and the size in sq m of your array and you will be in the ball park.

The interesting bit starts with figuring out what you self consume - thus saving imports - and what you export. Power plans and tariffs are helpful here plus usage at various times of the year. All sites are so different.

I can share my modelling if you are interested.

Otautahi Christchurch

fastbike

212 posts

Master Geek

#3283360 17-Sep-2024 23:05

mentalinc:

If I work out the planned panel count and the area of each panel, do I multiple those together then the 22% efficacy to get a real world expected solar production?

Not quite, the 752 w/m2 is an instanteous flow. If - and a big if (no clouds etc) - it was kept up for one hour then you get 47 m2 x 0.752kW which gives ~35kW of insolation. You will not get 22% efficiency, that is at a standardised test condition. Realistically use 16-18%, which would show around 5-6 kWh for that one hour.

NB: This varies throughout the day, see my earlier post.

Otautahi Christchurch

Jase2985

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#3283371 18-Sep-2024 05:35

I peaked yesterday at 1415 with 6.9kW in Auckland, with East and West facing panels, .8kW from the east and 6.1kW from the west. That was 80% of what my west panels were rated at.

mentalinc

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#3283374 18-Sep-2024 06:25

@fastbike yes that would be helpful if you've already built the model to save me reproducing.

Thanks for some recent real world numbers @jase2985

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SumnerBoy

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#3283389 18-Sep-2024 08:21

fastbike:

I've discovered OpenHAB, which has some very cool integrations.

I was an openHAB user for years, but recently switched to Home Assistant. They are both good, but one thing I have been very impressed with HA is the energy dashboard. If you have sensors monitoring house usage, site import/export, solar and/or battery generation, and individual device monitoring you can get a pretty impressive representation of your usage.

This is my dashboard so far today, it even pulls in PV forecasting data to show what it thinks your PV generation will be today. I have a water meter on my water main so it will track that as well.

Then the lower half of the dashboard shows a more detailed breakdown, by hour, of individual devices. The more you can monitor the better.

I find this a very good tool for monitoring my overall usage, generation and what is using the most energy. The default is this daily view but you can quickly switch to showing monthly or even yearly summaries, with all the same information, just aggregated over a longer period.

dantheperson

174 posts

Master Geek

#3283512 18-Sep-2024 13:06

fastbike:

The interesting bit starts with figuring out what you self consume - thus saving imports - and what you export. Power plans and tariffs are helpful here plus usage at various times of the year. All sites are so different.

One thing i didn't account for is how much effect clouds have, generation is constantly jumping up and down. Check out my production yesterday, this is pretty common. the classic bellcurve you see is rare (though i haven't had a summer with them yet)
https://pvoutput.org/intraday.jsp?id=121065&sid=104930&dt=20240916&gs=3&m=1

So if you've got any large loads, you are gonna be pulling from the grid allot. Makes the hotwater and EV diverters worthwhile investments, or a small battery. I'm probably going to go a medium batter over diverters as it has the added benefit of load shifting morning/evening peaks.

SumnerBoy

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#3283515 18-Sep-2024 13:10

dantheperson:

So if you've got any large loads, you are gonna be pulling from the grid allot. Makes the hotwater and EV diverters worthwhile investments, or a small battery. I'm probably going to go a medium batter over diverters as it has the added benefit of load shifting morning/evening peaks.

I have been running a PV diverter for years in my old house (with solar but no battery) and it was definitely worth it. However after building this new place and installing a Powerwall I have come to the same conclusion as you, a diverter is not really necessary if you have a battery. The additional benefits such as load shifting and outage protection add to the appeal.

Here is a thread where I have been discussing this topic in depth with some clever chaps from the UK which you might find interesting...

https://community.openenergymonitor.org/t/solar-pv-battery-do-i-need-a-diverter

fastbike

212 posts

Master Geek

#3283670 18-Sep-2024 17:35

mentalinc:

@fastbike yes that would be helpful if you've already built the model to save me reproducing.

PM sent with a link.

Otautahi Christchurch

fastbike

212 posts

Master Geek

#3283764 19-Sep-2024 06:57

SumnerBoy:

Here is a thread where I have been discussing this topic in depth with some clever chaps from the UK which you might find interesting...

https://community.openenergymonitor.org/t/solar-pv-battery-do-i-need-a-diverter

I followed this project a few years back - they had a DIY power monitor kit IIRC. I'll take a look at what they're up to now.

The cost of energy has really spiked in the UK from when I lived there 25 years ago. But then technology has presented a whole new range of solutions if you are positioned to take advantage of them. Although many people for reasons beyond their control are unable.

Otautahi Christchurch

fastbike

212 posts

Master Geek

#3283766 19-Sep-2024 07:05

dantheperson:

One thing i didn't account for is how much effect clouds have, generation is constantly jumping up and down. Check out my production yesterday, this is pretty common. the classic bellcurve you see is rare (though i haven't had a summer with them yet)
https://pvoutput.org/intraday.jsp?id=121065&sid=104930&dt=20240916&gs=3&m=1

Thanks for the interesting link. The local site I have been monitoring rarely shows a bell curve - which corresponds to my anecdotal view out of the window :)

I've got meters from a crowd called iammeter, they are prototyping a wifi controlled variable power controller, a bit like a light dimmer but capable of controlling bigger loads up to 3.7kW. I think they're targetting a price around USD100 so this would be ideal to control a HWC element with some automation sitting between figuring out how much power is available real time, clouds included, to avoid drawing from the grid.

https://www.iammeter.com/products/wifi-power-controller

Otautahi Christchurch

mentalinc

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#3285218 22-Sep-2024 20:39

Anyone know why the genless website would show such a large afternoon drop (for 2 hours) then goes back up again? before the expected drop as night falls?

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HarmLessSolutions

969 posts

Ultimate Geek

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#3285220 22-Sep-2024 20:49

mentalinc:

Anyone know why the genless website would show such a large afternoon drop (for 2 hours) then goes back up again? before the expected drop as night falls?

I'm a little confused as to what that data relates to. Solar drop for a period during the day is typically due to a shading issue if it occurs every day, or cloud cover if not daily. The time scale is a bit questionable as solar (at least currently in NZ) is well done generating by around 1800hrs currently.

Perhaps some more background information would be helpful?

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

Chewbacca

5 posts

Wannabe Geek

#3285383 23-Sep-2024 10:25

After reading all 48 pages of this thread and I am getting closer to actually getting a system

So ideal system for ROE is 5kw with lets say 7kw of panels (but also looking at larger systems). I can only export 5kw at a time, as i believe i only have a single phase (looking at the meter outside it says single phase, my switchboard isolator is two wide)

On some earlier post, someone indicated that the cost of a bigger inverter may only be a few hundred dollars. So why wouldn't i go for the same 7kw of panels on a say a 6.5 kw inverter. As in the middle of summer i am there will be periods i cant use all my power generation (via use or export), does this become an issue?

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