Grid Connect- Peak/Offpeak Load Shifting

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7circle
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Grid Connect- Peak/Offpeak Load Shifting

Post by 7circle » Mon, 07 Jun 2010, 08:35

Weber wrote:link...only one with the "load shifting" add-on for maximising the Net FiT
Won't the supplier complain that your putting power pack into the grid during the day even if your average power use is positive. The TOU meter will show the times of dat that it is negative.

As it's not part of the PV grid system any credit you generate will not result in a cash credit. They don't have to reimburse credit as cash since the connection is NOT qualified as a generator. The PV is signed up as small generator so it has its own metering system, even if it is part of a "SMART" meter that includes TOU (time of use).

So did that client have to get a special contract to get cash credit?
(re NET FiT)

So hopefully the retailers are ready for this.
The metering data stored for your home is going to have 30min blocks for the day. Thats 48 meter readings from smart TOU meter.

Is anyone being billed with a TOU meter?
Do they provide you on the bill with the daily 1/2hr accumulated averages?
Maybe its only available online for your bill.
Anyone with experience?

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weber
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Grid Connect- Peak/Offpeak Load Shifting

Post by weber » Mon, 07 Jun 2010, 15:27

7circle wrote:Won't the supplier complain that you're putting power back into the grid during the day even if your average power use is positive. The TOU meter will show the times of day that it is negative.
No. Why would they care? That's when PV systems normally put power back into the grid.
As it's not part of the PV grid system any credit you generate will not result in a cash credit. They don't have to reimburse credit as cash since the connection is NOT qualified as a generator.
It is only the PV system that is generating the credit. You're right that the rest of the system is separate from the PV system. It's essentially a UPS, but with the added feature that if the grid goes down the PV array is automatically switched over to charge the UPS battery instead of feeding the grid.

But when the grid is available, the customer runs their house off this UPS during the middle part of the day so their consumption is zero and they export all their PV energy.

This will be under the Queensland Solar Bonus Scheme whose details are given here:
http://www.cleanenergy.qld.gov.au/solar ... scheme.cfm

In particular:
"If the Solar Bonus payments are greater than the total grid-connected electricity consumption charges over a 12-month period, the customer is entitled to have this balance refunded, rather than maintaining an ongoing credit."

I understand this is pretty much a copy of the South Australian scheme, but other states may vary.
The PV is signed up as small generator so it has its own metering system, even if it is part of a "SMART" meter that includes TOU (time of use).
You seem to be contradicting yourself re whether it is considered a generator or not, by the network. I don't know, and it doesn't really matter for payment purposes as there is specific legislation for it, as described above, as there is in other states too.
So did that client have to get a special contract to get cash credit?
(re NET FiT)
No, it's just the normal Solar Bonus Scheme arrangement.
So hopefully the retailers are ready for this.
Sure. They have to be. It's Queensland law.
The metering data stored for your home is going to have 30min blocks for the day. Thats 48 meter readings from smart TOU meter.

Is anyone being billed with a TOU meter?
Do they provide you on the bill with the daily 1/2hr accumulated averages?
Maybe its only available online for your bill.
Anyone with experience?

As far as I know, in Queensland at least, the TOU information isn't even read. "Smart meter" is a misnomer. It's an "interval meter". You don't get "smart metering" until the network owner adds two-way communications to it, presumably via the mobile phone network or WiMax.
One of the fathers of MeXy the electric MX-5, along with Coulomb and Newton (Jeff Owen).

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Grid Connect- Peak/Offpeak Load Shifting

Post by 7circle » Tue, 08 Jun 2010, 09:21

Sorry Weber
I realised the system you decribed only feeds the battery inverted power to the house only, not to the grid via the peak reading meter.

I understand this system described is only maximising PV power to the grid by diverting power to the battery inverter so there is no house load during sunlight.

My questions relate to if you were just load levelling the grid. Storing say 20kWh during the off peak as 11c/kwh and shoving back during the day at 22c/kwh. Thats $20/day 90% efficient. Leaving the PV feed seperate.
(Edit - Oops that should be $2/day)

As this is what is being suggested for EV battery packs, I was hoping one of the states power retailers was allowing it with cash benifits to the customer.

I realise the 2:1 between peak/off peak is not as good as 6:1 for PV.
But youve built a UPS that can nearly do it!

I guess that to keep the UPS feature fot most of the day the remaining battery power to 20% SOC at 8pm could be off-loaded to the grid before 11pm. Then recharge back to 100% in off peak as it does now. I guess this might not be good for the grid if the everyone did it.

Just trying to imagine the future with EV's on a green SMARTIE grid.

Looking at the "Automatic AC Transfer Switch" from Latronics, its a priority change over switch. It doesn't operate like the grid fail detection in GRID feed Inverters. I think these stop the inverter and check for mains within the 50Hz.

I had a look at the latronics inverters but they only offer the "Automatic AC Transfer Switch" as an option.
I thought there might be a change over output that meets the standards for "islanding" (is that the correct term).
Looking at the paralleling feature on some inverters on EM, most wouldn't meet the same specification standard the GRID feed detecters have.
(ie I can't find one that does)

Simpler to just buy an extra 3kW PV grid feed 48V inverter for $4000 to the battery linked a up to the SOC monitor and a timer. And guess what the PV grind feed inverter hooked up to the PV meter is not doing much between 8pm and 11pm . Image
But its circuits are untouchable.

Sorry for the huge rant.
Weber's link - QLD Solar Bonus Scheme wrote:The Queensland Government Solar Bonus Scheme (the Scheme) pays households and other small customers for the surplus electricity generated from roof-top solar photovoltaic (PV) panel systems, which is exported to the Queensland electricity grid."
But I think the question still remains.
Can you get paid for a negative power bill if you don't have PV Solar,
From just peak levelling?

(Edit - Oops that should be $2/day)
Last edited by 7circle on Tue, 08 Jun 2010, 19:45, edited 1 time in total.

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Grid Connect- Peak/Offpeak Load Shifting

Post by weber » Tue, 08 Jun 2010, 16:12

7circle wrote:My questions relate to if you were just load levelling the grid. Storing say 20kWh during the off peak as 11c/kwh and shoving back during the day at 22c/kwh. Thats $20/day 90% efficient. Leaving the PV feed seperate.

As this is what is being suggested for EV battery packs, I was hoping one of the states power retailers was allowing it with cash benifits to the customer.
OK. Sorry I didn't understand.

I think it may just barely be possible to get network and retailer agreement to do this now, but you'd have to negotiate it yourself. Clearly you're not going to get any Solar Bonuses. You would probably only get paid the standard tariff rate for what you export.

They would be very worried that you might just pull power in through the off peak meter and feed it straight back out through the normal meter again at the same time, not using your batteries to delay export to peak times. I don't know how you'd convince them you weren't able to do that.

When you apply for the Qld Solar Bonus Scheme they ask if you have batteries in your system. You can't get it if you do, for the very reason I mentioned above.

Yes. The networks are definitely interested in using vehicle batteries for peak load shaving, and paying for it. But it's early days for that. Still being worked out. There is a conference on it in Brisbane in October.
I realise the 2:1 between peak/off peak is not as good as 6:1 for PV.
But youve built a UPS that can nearly do it!
2:1 is so not-as-good that it would be uneconomical, except possibly on a large scale using flow batteries (Zinc/Bromine or Vanadium/Vanadium).
I guess that to keep the UPS feature for most of the day the remaining battery power to 20% SoC at 8pm could be off-loaded to the grid before 11pm. Then recharge back to 100% in off peak as it does now. I guess this might not be good for the grid if the everyone did it.
I certainly wouldn't be discharging lead-acids to 20% S0C every day. They don't last very long if you do that. To keep the 10 year warranty on my lead-acids I have to have an average daily discharge no lower than 67% SoC, and other limitations.
Looking at the "Automatic AC Transfer Switch" from Latronics, its a priority change over switch. It doesn't operate like the grid fail detection in GRID feed Inverters. I think these stop the inverter and check for mains within the 50Hz.

I had a look at the latronics inverters but they only offer the "Automatic AC Transfer Switch" as an option.
I thought there might be a change over output that meets the standards for "islanding" (is that the correct term).
"Anti-islanding" is what grid inverters have to do. They must meet AS 4777. The list of approved inverters is on the Clean Energy Council website. I think the Selectronic SP PRO series are the only ones that might do what you want.
Looking at the paralleling feature on some inverters on EM, most wouldn't meet the same specification standard the GRID feed detecters have.
(ie I can't find one that does)
If it's not on the abovementioned list, you can't connect it to the grid in Australia.
Simpler to just buy an extra 3kW PV grid feed 48V inverter for $4000 to the battery linked a up to the SOC monitor and a timer. And guess what the PV grind feed inverter hooked up to the PV meter is not doing much between 8pm and 11pm . Image
But its circuits are untouchable.

As I mentioned in response to a question of acmotor's in the other thread, the Latronics GC inverters have a DIP-switch-selectable mode where they will operate off a battery instead of MPPTing a PV array. But they will not discharge that battery below float voltage (54 V or 108 V).

However, there is bound to be a resistor voltage divider that the microcontroller uses to sense the input voltage, that could be modified to fool it, and cause it to discharge the battery to a lower voltage. But obviously all warranties are off in that case.
One of the fathers of MeXy the electric MX-5, along with Coulomb and Newton (Jeff Owen).

7circle
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Grid Connect- Peak/Offpeak Load Shifting

Post by 7circle » Wed, 09 Jun 2010, 05:30

Thanks again Weber.
After looking at the acredited list and other web info it looks like suitable off the shelf UPS inverters for isolating grid connection are not generally availble. The selectronic SP Pro does stand out as the only product to have a charger and grid interactive system and it comes with a PV MPPT too.
I'll have to dig around to find out what could be done at a lower cost than $8000 for 4000W charger/inverter grid tie system system.

I was hoping to find a box that just monitor the grid interface with current and voltage sensors, but it looks like it needs power electronics too.

And Oops $20/day should be $2/day, I had $600 per year in my head which roughly makes sense. That could pay off $1800 of equipement if the battery economics allows for it too.

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