Energy Matters Forums

[MichaelB]

Electricity distributor SP AusNet yesterday announced its partners in the rollout of more than 680,000 Landis+Gyr 'smart meters' to homes and small businesses across eastern and north eastern Victoria.

Read more:

http://www.energymatters.com.au/index.p ... cle_id=637

[Tracker]

According to the SP AusNet web site, smart meters will empower electricity customers to better manage their energy needs, cut carbon emissions and will help increase retail competition.

What crap ! They will enable exotic Time-Of-Day charges , that will cause customers to turn off appliances in peak periods..
If that is how you cut Carbon Emissions, then perhaps they are right !

[MichaelB]

I've also heard rumours that these smart meters won't have net metering capabilities; so if you have one of these installed and then go solar, you'll need yet another meter.

I've contacted the company for clarification - like I said, it's just a rumour and I haven't been able to find anything definitive stating they do/don't support net metering. I'll update this post when I have heard back from them.

[karlajensen]

I was out in sunshine / ST albans the other day and they are in fact getting type 5 bi directional meters.
they are doing it street by street..

[ElectricEd]

[quote="MichaelB"]I've also heard rumours that these smart meters won't have net metering capabilities; quote]

I think you mean Gross. They can do net and do a "modified gross" where they total all of the power going out to the grid.

[Sojin_Muneshi]

All Smart Meters are designed to be capable of bi-directional measurement, not all of the Networks have that capability in their meters at this time.

Net and Gross is a function of the configuration, not the meter itself.

Gross requires two meters, with one dedicated to the generator output, it is an inefficient way to provide a subsidy to the customer.

Net Metering in Victoria's PFIT pays the customer for energy delivered to the grid net of their own consumption. NSW has a Gross PFIT Scheme.

regards

Sojin

[ElectricEd]

... Gross requires two meters, with one dedicated to the generator output, it is an inefficient way to provide a subsidy to the customer....

Not so. Net metering can be done with one meter. It just requires the meter to have a second input connected directly from the solar inverter. Meters used in some places overseas do this.Currently under the AS3000 rules the inverter is connected to the customer side of the meter via a circuit breaker, so true gross metering (as you mention) cannot be done without a second meter that is between the inverter and the circuit breaker.
If the our illustrious gubbmnt haven't specified the the new smart meters to have a second input for this purpose then yes, a very inefficient way to provide a subsidy to a customer. Going by their performance in other areas you can probably assume that they haven't.
They have however specified a second output for sheddable high power loads such as air conditioners so that these can be turned off rather than cutting power to an area.

[Sojin_Muneshi]

.

Not so. Net metering can be done with one meter. It just requires the meter to have a second input connected directly from the solar inverter. Meters used in some places overseas do this.Currently under the AS3000 rules the inverter is connected to the customer side of the meter via a circuit breaker, so true gross metering (as you mention) cannot be done without a second meter that is between the inverter and the circuit breaker.

Yes you are correct, "Net" metering not only can be, but must be always done with one meter, it is claimed that Net metering can be done with multiple meters and subtractive calculations however this is incorrect, the mathematical results do not equate.

However I was talking about the requirement of Gross metering that requires "two" meters.

I suspect your reply was actually in response to my statement about "Gross" metering which you quoted I "think" you actually may have meant to say "Gross" metering can be done with one meter, referring to a meter with a second input, however this is called a "Two Element" meter and is effectively two electronic meters in one box, it is only available in single phase and is the engineering equivalent of two meters, in multiphase there is no choice but to use two meters.

Gross metering requires the meter to be somewhere between the generator and the eventual load or grid, it is usually on the supply side of the circuit breaker, with the generator on the other side in compliance with AS3000 and any state based Service and Installation Rules.

Gross Metering requires two seperate metering circuits being measured independantly, (whereas Net Metering requires a single metering circuit.)

This should not be confused with a bi-directional meter that measures energy flows in and out of the same circuit idependantly. Net meters are bi-directional, Gross meters need not be bi-directional although most have the capability.

Two element meters have been in use in Victoria for over 20 years, with most hotwater customers on the winner tariff having one, however most of these are typically not suitable for use with generation as they are not bi-directional, and Gross is not available in Victoria in anycase.

A Net meter is always a bi-directional meter, and measures energy flows in both directions, it is NOT netting off the generation from the consumption as sometimes mis-understood, the description as NET relates to the meter only measuring the "surplus" generation energy not utilised by the customers own loads.

It needs to be wired into a metering configuration consisting of only one meter (and a single element meter) to avoid other customer loads such as Slab heating etc being supplied in a partial gross arrangement, this is why many customers moving to PFIT encounter further metering work, even if they already have an SFIT bi-directional meter.

As an example:

GROSS Metering has at least two meters M1 measuring all of the customer's generation. and M2 measuring all of the customer's consumption (or a two element meter wired to achieve the same thing).
The customer will be paid for 100% of his generators output at the PFIT ie 1kW unit will produce 1KWh over 60 minutes, customer gets paid 60c/kWh. However at the same time (ie the same hour and perhaps concurrently) the customers house may be consuming load at 1.5kW, ie consuming 1.5kWh and being charged 23c/kWh - he is paid 60c but all of his 1.0kWh generation actually supplied his own loads none was delivered to the grid, and required another 0.5kWh to be delivered from the grid to feed his 1.5kWh of load, which has cost a total of 34.5c (23c x 1.5)

Nothing was supplied to the grid, but he was paid for 100% of his generation and made a profit of 25.5c.

NET metering has a single meter M1, measuring all of the customers energy delivered to the grid, and all of the customers energy delivered from the grid. If the same situation of above occurs, the 1kW output of the customers generation is consumed directly by his 1.5kW loads, and over an hour he consumes 0.5kWh from the grid to meet his remaining load.

Nothing was supplied to the grid, and he is charged for the 0.5kWh delivered from the grid at 23c/kWh ie he pays 11.5c

Of course those who own PV units much prefer Gross, however as the PFIT payment is coming from all other customers as a subsidy it doesnt seem equitable or fair.

In another example the customers Generator output exceeds his load

Generation = 1.5kWh (1.5kW generated over 1 hour)
Load = 1.0 kWh

GROSS Metering - M1 measures 1.5kWh generated and credits the customer with 90c (60c x 1.5), the load is measured on M2 as 1.0kWh and charges the customer 23c.

The customer makes a profit of 67c, yet 66% of his generation is used by himself and only 33% of his generation or 0.5kWh was delivered to the grid.

NET Metering , the M1 meter measures the 0.5kWh delivered to the grid and credits the customer with 30c (60c x 0.5), as the customers load was supplied internally by the customers own generator there is no delivery from the grid and no charges for the energy consumed by the load as it did not pass through the meter.

The customer makes a profit of 30c, and pays nothing for the energy consumed as he generated it himself.

The Victorian PFIT subsidy from all other customers is paying the PFIT customer for the energy he delivered to the grid, not what he used himself.



Regards

Sojin

[ElectricEd]

Oops, I should have written "Gross metering can be done with one meter."
I take on board all that you mentioned, an amendment to AS3000 would be required to use one meter in Australia.
It's no great difficulty having multiple measuring elements, it just requires an extra toroid ring and a mosfet switch for addressing each. A single processor can read at least a dozen circuits and come nowhere near impacting on the resolution of the readings.
On an aside issue, the new smart meters talk to the base via a low power mesh radio network and 3g, sending data every 30 minutes. This means that you could get a 'sort of' hybrid net/gross reading which would come close to full gross for the typical household which is empty during daylight hours and only starts using electricity in the evening. The only thing to muck up this would be items using standby power and the typical refrigerator. A really well insulated fridge should not cycle too often once it is down to the required temperature.
With this system you'd be getting the full 60c for all of the KWHs generated and be paying only 23c for power that you use in the evening.
In reality it will be used to charge us variable rates depending on the time the power was used. The consumer needs to be smart about using power to take advantage of these rates.

[bpratt]

In reality it will be used to charge us variable rates depending on the time the power was used. The consumer needs to be smart about using power to take advantage of these rates.

The biggest catch of all of this is that with TOU metering, is that the elderly, infirm, young families, and others like them don't get much say in when they use the power.

Most of these people are in a position where they can't wait to do all their housework of a night time, and the majority of their power usage is after 9am.

A Net FiT means they get little to nill credit on their solar because of their usage patterns.

As you said the consumer needs to be smart about using power to take advantage of TOU rates, but sadly these people have issues that prevent them from doing so.