Measuring current direction plus more

[MikeSolar]

OK, I am surprised I haven't found this on here yet. I want to find an inexpensive way to determine whether I have an excess of power from the solar and to be able to control that power (AC or DC and apart from any inverters or charge controllers) to shunt it where ever I want (or just turn it off). With some utilities wanting big bucks just to reprogram the meter to flow both ways, I'm looking for a completely behind the meter, guerrilla solar method to do this. I don't want to give them 1 watt of power and currently, they are charging $1500 just for the privilage of net metering. Any ideas?

[Sunking]

OK, I am surprised I haven't found this on here yet. I want to find an inexpensive way to determine whether I have an excess of power from the solar and to be able to control that power (AC or DC and apart from any inverters or charge controllers) to shunt it where ever I want (or just turn it off). With some utilities wanting big bucks just to reprogram the meter to flow both ways, I'm looking for a completely behind the meter, guerrilla solar method to do this. I don't want to give them 1 watt of power and currently, they are charging $1500 just for the privilege of net metering. Any ideas?

Yeah forget about it. They make Hybrid Grid Tied Inverters that do that. But once you understand the economics, you will give up that idea. It cost you $5 to generate power power to save $1 or sell to the POCO. Only Democrats spend $5 to sell at $1. That is why they got thrown out of every office at every level. However if you insist, Dan be along shortly to take your money and help you.

Pure off grid systems do have controllers with Dump Loads mostly used for wind turds so they do not self destruct when the batteries are charged up and the controller shuts off. A dump load is a heater to dump excess energy as waste heat outside or in a tank of water.

[Mike90250]

So, I'll assume you are on-grid. I'm surprised at the amount of the net-meter fee, is that one-time, monthly, or annual ? Do you know what rate they pay you? (6

[MikeSolar]

Yes, this is for on gird. The utility charges $1500 (it's one time, often more due to some stupid formula they won't disclose) and it doesn't matter what size of system it is. In the city, where the roof is often too small for more then a couple kw, it makes little sense for some people to go above board. I just want to have something up my sleeve for these types. I'm looking for something that is not integrated into an standard inverter like the grid tie sunits with battery backup. I'll ignore the sunking partisan comment as it is not relevent, haha

[SunEagle]

Yes, this is for on gird. The utility charges $1500 (it's one time, often more due to some stupid formula they won't disclose) and it doesn't matter what size of system it is. In the city, where the roof is often too small for more then a couple kw, it makes little sense for some people to go above board. I just want to have something up my sleeve for these types. I'm looking for something that is not integrated into an standard inverter like the grid tie sunits with battery backup. I'll ignore the sunking partisan comment as it is not relevent, haha

Will you share which POCO charges you that much for a solar grid tie connection? It seems very high and a little strange to me.

Of course if you really don't want to send the POCO any of your power generation you can always just disconnect and go off grid.

[jflorey2]

OK, I am surprised I haven't found this on here yet. I want to find an inexpensive way to determine whether I have an excess of power from the solar and to be able to control that power (AC or DC and apart from any inverters or charge controllers) to shunt it where ever I want (or just turn it off). With some utilities wanting big bucks just to reprogram the meter to flow both ways, I'm looking for a completely behind the meter, guerrilla solar method to do this. I don't want to give them 1 watt of power and currently, they are charging $1500 just for the privilage of net metering. Any ideas?

It is doable but not easy. You have to measure current in both conductors (assuming a standard 120/240VAC service) and the voltage on both. The relative phase of the current and the voltage will determine whether you are producing or consuming power. Several semiconductor companies make chipsets (intended for smart meters) that implement these sorts of measurements. You'll end up with two clamp-on ammeters and two voltage sense points.

That's part one. Part two is using the power. You need a very fast reacting resistive load, one that can be switched in at different load levels. (No, a dimmer won't work to control this.) For example, a set of hot water heater elements that are rated for 100 - 200 - 400 - 800 - 1600 watts would give you a 100 watt resolution. Note that you will invariably end up using more power than you used to, because you will not be able to zero it out exactly and thus will always have to err on the side of taking more power.

I'll ignore the sunking partisan comment as it is not relevent, haha

That is wise.

[dennis461]

OK, I am surprised I haven't found this on here yet. I want to find an inexpensive way to determine whether I have an excess of power from the solar and to be able to control that power (AC or DC and apart from any inverters or charge controllers) to shunt it where ever I want (or just turn it off). With some utilities wanting big bucks just to reprogram the meter to flow both ways, I'm looking for a completely behind the meter, guerrilla solar method to do this. I don't want to give them 1 watt of power and currently, they are charging $1500 just for the privilage of net metering. Any ideas?

You are in Canada, right?

All you really need to do is keep track of your meter readings on a sunny day.
If it runs backwards, you do not need a NET meter.

Is you system 240VAc with center tap ground? Meaning, 240VAC to electric range and 120VAC wall outlets.

Most US analog meters were capable of running backwards.
Pick up a used one from e-bay and install it in line with the regular meter.

http://www.ebay.com/itm/New-Landis-G...0AAOSw8aNXGODY

Is the question you posted for your system or customers?
Meaning, do you need a solution for one system or many?
".... I just want to have something up my sleeve for these types...."

[Sunking]

YI'll ignore the sunking partisan comment as it is not relevent, haha

Haha, no problem. PC is much easier than facing the truth, taking responsibility, and solving problems. Haha!.

But the facts and bottom line are I am right, what you want can be done if money is no object my friend. Trust me it is not going to happen. Does not matter if you like it or not, or PC. That is real.

[DanS26]

I thought Schneider/Conext made an inverter that you could program to not send any power into the grid.......maybe requires a battery or batteries but worth looking into.

If you designed a minimal battery system...ie not designed to provide any more than negligible power into your home, it could be financially feasible but highly unlikely. The only way would be to design and build all DIY. Even then it would be a long payback. But if you are that PO'ed over your POCO you could do it for spite ignoring the costs.

[Mike90250]

The Schneider/Conext XW inverters have a grid support mode, where they "support the grid" but don't backfeed. The inverter has all the power steering sensors internally, and a transfer switch. The only catch is, they need a decent size battery bank to support the inverter, or AC ripple starts showing up on the DC bus. That battery bank every 5 years, is going to cost way more than the savings from the grid fees.

And you will still have visual solar panels on the roof, which the power company is eventually going to figure out when they research why your usage dropped from it's norm.

[MikeSolar]

Will you share which POCO charges you that much for a solar grid tie connection? It seems very high and a little strange to me.

Of course if you really don't want to send the POCO any of your power generation you can always just disconnect and go off grid.

The utility was forced into accepting solar so they try to discourage it when possible. The cost of admission is just one thing. There is a huge amount of paperwork too.

[MikeSolar]

You are in Canada, right?

All you really need to do is keep track of your meter readings on a sunny day.
If it runs backwards, you do not need a NET meter.

Is you system 240VAc with center tap ground? Meaning, 240VAC to electric range and 120VAC wall outlets.

Most US analog meters were capable of running backwards.
Pick up a used one from e-bay and install it in line with the regular meter.

http://www.ebay.com/itm/New-Landis-G...0AAOSw8aNXGODY

Is the question you posted for your system or customers?
Meaning, do you need a solution for one system or many?
".... I just want to have something up my sleeve for these types...."

Canada is just like the States and we chare a lot of power pack and forth so from a technical point of view it is all the same. Although, I want to try it on my new house, I have customers that want it too but I never had a reasonable solution for them. I should think it would not be that difficult although I know it may be hard with a continuously variable house load.

[MikeSolar]

It is doable but not easy. You have to measure current in both conductors (assuming a standard 120/240VAC service) and the voltage on both. The relative phase of the current and the voltage will determine whether you are producing or consuming power. Several semiconductor companies make chipsets (intended for smart meters) that implement these sorts of measurements. You'll end up with two clamp-on ammeters and two voltage sense points.

That's part one. Part two is using the power. You need a very fast reacting resistive load, one that can be switched in at different load levels. (No, a dimmer won't work to control this.) For example, a set of hot water heater elements that are rated for 100 - 200 - 400 - 800 - 1600 watts would give you a 100 watt resolution. Note that you will invariably end up using more power than you used to, because you will not be able to zero it out exactly and thus will always have to err on the side of taking more power.

That is wise.

I totally understand that this is not a financially viable idea in that there will be times when the PV system will be off (just to spite the utility) but people still ask me for it so I will try to figure out something that doesn't include batteries. How yet, I have not much of an idea.

[MikeSolar]

The Schneider/Conext XW inverters have a grid support mode, where they "support the grid" but don't backfeed. The inverter has all the power steering sensors internally, and a transfer switch. The only catch is, they need a decent size battery bank to support the inverter, or AC ripple starts showing up on the DC bus. That battery bank every 5 years, is going to cost way more than the savings from the grid fees.

And you will still have visual solar panels on the roof, which the power company is eventually going to figure out when they research why your usage dropped from it's norm.

Yes, the battery bank is something i wish to avoid. It appears that something bespoke is needed and that may be out of my depth. We shall see.

[SunEagle]

The utility was forced into accepting solar so they try to discourage it when possible. The cost of admission is just one thing. There is a huge amount of paperwork too.

I can understand not wanting to pay a huge fee just to connect a solar pv system to the grid. But unfortunately the only options not to send them any of your power will cost a lot more in equipment to avoid the problem.

Remember without being totally off grid, most people still need to use the power the POCO provides. They should pay for that power along with helping to keep the distribution system working which comes with the catch of having to pay what they ask for, reasonable or not.

If cost is not a problem then the options are many. But if the motivation is to save money I would say in the long run paying the connection fee (as painful as that seems) will be less costly.

There are many "expenses" I really do not like to pay like medical insurance. But just because I feel the price is unrealistic does not make sense for me to go without that insurance. So if people don't like paying the fees their POCO requires doesn't mean the best plan is to avoid that cost.