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[jojo69]

Instead you want 1/3 pointing south east and 1/3 pointing south west and 1/3 south.  This allows you to pick up the early morning sun and the late afternoon sun which is much more valuable than the midday sun.  

  

no offense, but the way I parse this is that your battery is undersize

[1713415077]

1713415077

[1713415077]

1713415077

[HairyMaclairy]

You are correct, it’s undersize.  But in economic terms, the grid is a much cheaper and bigger battery for normal everyday household consumption given current feed in tariffs.  

The battery is more about energy security.  Keep in mind most solar will be cut off when the grid goes down. People won’t be able to generate at all because the utility shuts down their solar remotely to stop them exporting.   The Tesla has a gateway to allow you to generate behind the battery.

[jojo69]

fair enough

[HairyMaclairy]

https://twitter.com/hmichellerose/status/1233578788228943873?s=20

Probably I would order this one for damn sure

Hell yeah that sounds delicious

[vapourminer]

Yes in an emergency we would loose the beer fridge, which should significantly reduce our load.  As you point out, aircon is the real killer.  Our system draws at least 6kw so would be a definite no.

A key is not to fully optimize your panels, don’t point them all due South because that will give you a weak feed on the shoulder periods and a big spike in the middle of the day when you just have to dump it on the grid. 

Instead you want 1/3 pointing south east and 1/3 pointing south west and 1/3 south.  This allows you to pick up the early morning sun and the late afternoon sun which is much more valuable than the midday sun. 

Battery is a Tesla Powerwall 2 with 13.5 kWh with 5% capacity reserved for intermittent grid trips - it comes on in less than a second. Sometimes you actually get more than 13.5 out of it in a day if there is a storm and you draw down and then recharge in the afternoon

Other days it doesn’t get a full charge if it is cloudy and we are running the aircon non-stop - household consumption can peak around 70kw/h per day which exceeds panel capacity even in full sun if we abuse aircon, run the stove, dishwasher, clothes dryer.

Panels cost very little these days, they seem to be halving in price every five years.  If you put your system in awhile ago, you might try and see if you can economically add more panels.  Of course you will need a converter but if your string inverter doesn’t have enough capacity you could consider adding microinverters which allow you to add panels piecemeal. 

solar trackers.

not very portable though plus high upfront cost.

[bitserve]

You are correct, it’s undersize.  But in economic terms, the grid is a much cheaper and bigger battery for normal everyday household consumption given current feed in tariffs.  

The battery is more about energy security.  Keep in mind most solar will be cut off when the grid goes down. People won’t be able to generate at all because the utility shuts down their solar remotely to stop them exporting.   The Tesla has a gateway to allow you to generate behind the battery.

Is that legal somehow? How does it work? Does it inject to a completely different line in your house or is able to somehow isolate from the grid so that no electricity is injected back?

Have you considered installing one of those cheap small aircon split unit (one with 1kw max) in at least one room, ie the bedroom, so in case of a blackout you have some air conditioning at least? Obviously your 7kw central unit is a no-go without the grid and that is probably the only thing missing in your nice setup.

[fillippone]

Very interesting.
I think I can play bingo reading  any random Italian newspaper.
Any hint of this in the WO?

[lightfoot]

This Covid-19 shit is starting to become a pandemic.

Absolutely surreal watching a game of Plague Inc. play out in real-time.

I'm starting to get the fear. Supposed to be traveling to Amsterdam, and Ireland in April.

For me it's like seeing "On the Beach" play out in real time. Yep, Oregon just went dark, party on!

[lightfoot]

You are correct, it’s undersize.  But in economic terms, the grid is a much cheaper and bigger battery for normal everyday household consumption given current feed in tariffs.  

The battery is more about energy security.  Keep in mind most solar will be cut off when the grid goes down. People won’t be able to generate at all because the utility shuts down their solar remotely to stop them exporting.   The Tesla has a gateway to allow you to generate behind the battery.

Ok, so you're grid-tied with the ability to run your own power island if things go down off the batteries. My system is tied into a Sunny Boy 1800 for the grid which can be manually switched into a MPPT converter that can feed the battery bank in the event things go odd. Manual, but works. The batteries are in my work shed, which has about 320 watts of solar directly connected to it to keep the shed running and the batteries peaked.

I have thought about getting a Sunny Island or a Trace SW4024 so I can automatically switch between grid and solar, but another option would be to just break down and put the Matrix in the house and wire it up to a subpanel that runs the fridge and other stuff. I'll think about that, but a 700 watt inverter is enough to run the critical stuff including the microwave.

Solar panels *are* cheap these days, I bought mine at about $2 a watt used for the single crystal ones. Modern polycrystaline are a bit less efficient (take up more space and are *heavier*) but that's not too big of a deal. Will think about it.

[jbreher]

the lithiums have made impressive strides in energy density, outpacing your Trojans by a fair bit

that said, and I am quite aware of the dangers inherent in H2SO4, if I had one of those power walls it would be installed in an airtight bunker some distance from the dwelling...

when lithium decides to do the bad, it is really bad

True. For a house system weight and energy density aren't as big a problem as in a car (where you have to like move it). So L16 or T105 batteries can get you a lot of power for a reasonable price without the major fire problem of lithiums.

As for hydrogen I've never seen issues with lead, however I guy I knew did blow the bed off his battery powered truck with flooded NiCD batteries. Those last forever but really can gas hydrogen on charge. Oh well.

100ah AGM batteries are quite nice as well but a bit more pricey per AH. Any way you go, you need to figure out how much power you need per day, then build your solar panels to put that much power back in 1/2 day (factoring in cloudy days) with a battery capacity of at least 3-4 times your load for rainy days and the like. Thus if you want to run the fridge (200 watts*24=4.8kw) some lights (about 1kw a day) and a toaster (1,500 watts for an hour a day) you're at 7kw. Thus a 28kw battery pack and 14kw of solar will do it. Assuming 5 hours of sun per day (and you factored in the 2x oversize for solar) and you're talking a ~2kw array and if the batteries are 48v then a 500ah battery pack or 16 T105's.

Takes more power than you think.

Thanks for the info. But you have a unit problem.

Watts != Watt-Hours

[HairyMaclairy]

Uh we paid US$259 per panel for Hanwha Qcells @ 340 watt each. Need to double the cost to account for microinverters, installation and electrical work.

So that’s about $520 for 340 watt which is $1.52 / watt for a large install (scale pricing).  You can then take off any government incentive schemes which would reduce the price.

The 340 watt panels seem to peak out around 1.2 kw/h per day.  

Edit:  1.2kwh is wrong. They peak at 1.85kw/h per day.

Back of the envelope calculation, one panel produces on average about $0.25 worth of electricity per day at 25 cents / kw/h tariff.  0.25 x 365 = $91.25 per annum so a touch more than 5 years to pay off. 

Our ROI was much faster because we had government subsidies which brought the cost down by a third.

[lightfoot]

You are correct, it’s undersize.  But in economic terms, the grid is a much cheaper and bigger battery for normal everyday household consumption given current feed in tariffs.  

The battery is more about energy security.  Keep in mind most solar will be cut off when the grid goes down. People won’t be able to generate at all because the utility shuts down their solar remotely to stop them exporting.   The Tesla has a gateway to allow you to generate behind the battery.

Is that legal somehow? How does it work? Does it inject to a completely different line in your house or is able to somehow isolate from the grid so that no electricity is injected back?

Have you considered installing one of those cheap small aircon split unit (one with 1kw max) in at least one room, ie the bedroom, so in case of a blackout you have some air conditioning at least? Obviously your 7kw central unit is a no-go without the grid and that is probably the only thing missing in your nice setup.

Actually a small window AC unit (5000 BTU) can be installed with only a few hundred watts. That can keep a room cool and since it's only for a few hours a day it's not as bad as the damn fridge.

[lightfoot]

the lithiums have made impressive strides in energy density, outpacing your Trojans by a fair bit

that said, and I am quite aware of the dangers inherent in H2SO4, if I had one of those power walls it would be installed in an airtight bunker some distance from the dwelling...

when lithium decides to do the bad, it is really bad

True. For a house system weight and energy density aren't as big a problem as in a car (where you have to like move it). So L16 or T105 batteries can get you a lot of power for a reasonable price without the major fire problem of lithiums.

As for hydrogen I've never seen issues with lead, however I guy I knew did blow the bed off his battery powered truck with flooded NiCD batteries. Those last forever but really can gas hydrogen on charge. Oh well.

100ah AGM batteries are quite nice as well but a bit more pricey per AH. Any way you go, you need to figure out how much power you need per day, then build your solar panels to put that much power back in 1/2 day (factoring in cloudy days) with a battery capacity of at least 3-4 times your load for rainy days and the like. Thus if you want to run the fridge (200 watts*24=4.8kw) some lights (about 1kw a day) and a toaster (1,500 watts for an hour a day) you're at 7kw. Thus a 28kw battery pack and 14kw of solar will do it. Assuming 5 hours of sun per day (and you factored in the 2x oversize for solar) and you're talking a ~2kw array and if the batteries are 48v then a 500ah battery pack or 16 T105's.

Takes more power than you think.

Thanks for the info. But you have a unit problem.

Watts != Watt-Hours

I hate screwing that up, but I think the math holds. watt hours is what everything should be measured in with watts alone just used for peak demand calculations.

[bitserve]

You are correct, it’s undersize.  But in economic terms, the grid is a much cheaper and bigger battery for normal everyday household consumption given current feed in tariffs.  

The battery is more about energy security.  Keep in mind most solar will be cut off when the grid goes down. People won’t be able to generate at all because the utility shuts down their solar remotely to stop them exporting.   The Tesla has a gateway to allow you to generate behind the battery.

Is that legal somehow? How does it work? Does it inject to a completely different line in your house or is able to somehow isolate from the grid so that no electricity is injected back?

Have you considered installing one of those cheap small aircon split unit (one with 1kw max) in at least one room, ie the bedroom, so in case of a blackout you have some air conditioning at least? Obviously your 7kw central unit is a no-go without the grid and that is probably the only thing missing in your nice setup.

Actually a small window AC unit (5000 BTU) can be installed with only a few hundred watts. That can keep a room cool and since it's only for a few hours a day it's not as bad as the damn fridge.

Yup, small aircons are currently *very* efficient. In fact, even already having a central unit (which is way less efficient) it makes some sense to have one individual unit in the more used room:

1) If you have been away for long, you run both and help cool/heat the room way faster.
2) If you often only stay in that room, maybe you can just go with it, with a great cost saving instead of running the central unit.
3) In the case of a solar installation and a blackout, the small unit might be reasonable to use, while the central unit is way too much. Better some than nothing.

Maybe that is not really a critical thing in the case of a big blackout, but I don't think some added comfort, if possible, is gonna hurt.

[jojo69]

solar trackers.

I don't want to come off as snarky, I know I can be an ass sometimes...

System complexity, in my experience there are exactly two kinds of trackers; those being installed, and broken ones...

I have heard rumors of there being a brief intermediate state of "working tracker", but I have never encountered it in the wild.

[jojo69]

... somehow isolate from the grid...

OK, I'm going to just give up and be snarky, it is an AMAZING new technology



BUT WAIT, THERE'S MORE!

THEY ARE CONTROLLED BY ROBOTS NOW!!!



living in the future man

[goldkingcoiner]

Very interesting.
I think I can play bingo reading  any random Italian newspaper.
Any hint of this in the WO?

Fascinating ways you can use these as psychological weapons against people,if you are talented, I imagine.

[bitserve]

... somehow isolate from the grid...

OK, I'm going to just give up and be snarky, it is an AMAZING new technology



BUT WAIT, THERE'S MORE!

THEY ARE CONTROLLED BY ROBOTS NOW!!!



living in the future man

That's funny... But what does the Tesla exactly do differently so that it is LEGAL to run an on-grid solar installation during a blackout while other systems do require to be automatically shut down on blackout? It's not that those could not have a relay to cut from the grid until the power comes back.

[vapourminer]

solar trackers.

I don't want to come off as snarky, I know I can be an ass sometimes...

System complexity, in my experience there are exactly two kinds of trackers; those being installed, and broken ones...

I have heard rumors of there being a brief intermediate state of "working tracker", but I have never encountered it in the wild.

no, not snarky at all.

there is a manual override mode. manually set it to  table mode or wjatever angle you want and lock it.

so fail safe = manual grunt. or just leave at optimum angle.

so when it does work its more efficient.

[HairyMaclairy]

You are correct, it’s undersize.  But in economic terms, the grid is a much cheaper and bigger battery for normal everyday household consumption given current feed in tariffs.  

The battery is more about energy security.  Keep in mind most solar will be cut off when the grid goes down. People won’t be able to generate at all because the utility shuts down their solar remotely to stop them exporting.   The Tesla has a gateway to allow you to generate behind the battery.

Is that legal somehow? How does it work? Does it inject to a completely different line in your house or is able to somehow isolate from the grid so that no electricity is injected back?

Have you considered installing one of those cheap small aircon split unit (one with 1kw max) in at least one room, ie the bedroom, so in case of a blackout you have some air conditioning at least? Obviously your 7kw central unit is a no-go without the grid and that is probably the only thing missing in your nice setup.

The gateway sits between the battery/solar and the meter.  So the meter never sees electricity which is produced by the panels and stored by the battery or consumed by the house. In a power cut the gateway closes, and production can continue behind the gateway.  

It’s signed off by the installer and inspected by the utility so completely legal (although US may be different).

I don’t understand air conditioner ratings. Our main system is rated 1800 watt but pulls 6kw.  Wtf?  Can someone with more electrical knowledge than me explain how this works?

We have a few smaller splits but they aren’t that small. They will still pull 2 - 3kw each.