Chi Meson's Home Solar System Success Story

[OmCheeto]

Nice, now all you have to do is get a car like the Nissan Leaf and you can be almost entirely energy independent.

I think I posted an email from our local EV club to that effect a while back:

7/20/2012
Greetings,
I finally got all the inspections and approvals today and am now generating electrons.
Whoo hoo

7/23/2012
Congrats! I turned on my system in March and it is totally cool to see my meter putting energy in the grid on a sunny day AND be able to charge my Leaf at the same time . . . charging my car on sunlight

 

[nsaspook]

I've just found out that the grid inter-tie will prevent me from using solar during an area blackout. The inverter is very, very sensitive, and can only switch on after analyzing the incoming grid for 5 minutes (it's got to be synchronized precisely). I'm wondering if I can trick it by plugging in a gas generator.

It's possible but you need a dump load (a large battery bank can save the energy) to absorb power as the grid-tie inverter functions as a current source and will increase voltage to the trip-point of the generator (functioning as a voltage source) or inverter unless there is a load equal to the power output of the panels. There are hybrid grid-tie inverters that also have battery backup and allow the panels to generate power during a blackout but it's usually more cost effective just to run the generator.

 

[Ms Music]

Is it even legal for you to be able to disconnect from the grid in a black out?

It has been several years since I had to abandon the solar idea, and I know much has changed since then, but if I remember right I would not have been able to have a system that could disconnect from the grid. I think I remember that it was possible to do easily, but it wasn't allowed. It never made sense.

 

[russ_watters]

As a safety matter, any house can be disconnected from the grid. The issue must be either a matter of the electronics of the inverter due to load sharimg or seamlessness of the changeover. Such issues don't exist for home generators because they don't parallel the grid and turn on well after a power failure.

My guess is that to save money, the inverter doesn't come with a separate automated disconnect switch. It may also have to do with difficulty matching the load and capacity - not sure what happens if your AC asks for 5 kW and the array is only providing 3.

 

[mheslep]

Nice, now all you have to do is get a car like the Nissan Leaf and you can be almost entirely energy independent.

Unlikely, not without adding batteries to his residential installation, or working a 3rd shift job or at home.

And even with the battery backup he'll be grid dependent in the winter, especially at Connecticut latitudes.

The panels are up. 7kW system will be 110% of our electrical needs. Grid intertie, no batteries,...

...

Batteries are not only unnecessary, they are "negatively beneficial" if talking 'bout environmental concerns OR financial concerns. The price of small inverters has come way the **** down, so it is much better to tie the solar output directly to the grid through the electric meter. When the panels crank out the kilowatts (mine is optimized for summer sun), the meter runs backward, and I get credit for the electricity I provide to the grid. At night, and in cloudy weather, the grid supplies electricity to me.

Received solar radiation kWh/M^2/day, Hartford, CT, flat plate tilted at latitude:
June: 5.3 avg, 6.2 max
Dec: 2.7 avg, 2.0 min

http://rredc.nrel.gov/solar/pubs/redbook/PDFs/CT.PDF

 

[russ_watters]

Mheslep, the concept here is "net zero" energy...

 

[Chi Meson]

There was a state/utility grant that paid about 1/3 of the cost and it was required to be for a "Net Zero" system. An additional panel was put in with the expectation that our use would increase as our 3 kids became 3 teenagers.

Not to mention, a missing panel would have been silly-looking (see first post).

But the panels are producing more this (dry) summer than the original estimates. Also, there's that thing about losing 10% of efficiency in the first 2 years. I don't think we'll maintain a net surplus for long.

 

[Ms Music]

Pardon me, I just re-read what I typed... I edited heavily before posting, and went too far. Didn't even realize I was completely wrong. Twice.

What I *MEANT* to say was that when the power went out, the system would automatically disconnect from the grid (so that electricians working on the lines would not get electrocuted) but that I couldn't use the power generated because of the way the disconnect works.

... I would not have been able to have a system that could disconnect from the grid...

Should have read "I would not have been able to have a system that could use generated power while disconnected from the grid." It wasn't legal with the current company and current local codes at the time. Is it the same for you?

(Sorry, communication is not my strong skill anymore!)

 

[mheslep]

Mheslep, the concept here is "net zero" energy...

Yes I know Connecticut and most states support net metering. Is that the same thing as being "energy independent"?

 

[mheslep]

Pardon me, I just re-read what I typed... I edited heavily before posting, and went too far. Didn't even realize I was completely wrong. Twice.

What I *MEANT* to say was that when the power went out, the system would automatically disconnect from the grid (so that electricians working on the lines would not get electrocuted) but that I couldn't use the power generated because of the way the disconnect works...

Yet there are commonly available disconnect systems that switch automatically (or manually) from the grid to alternative power (generator, whatever), protecting utility lineman.

 

[Ms Music]

Yes, I would have had to have a generator for when the grid went down.

I've just found out that the grid inter-tie will prevent me from using solar during an area blackout. The inverter is very, very sensitive, and can only switch on after analyzing the incoming grid for 5 minutes (it's got to be synchronized precisely). I'm wondering if I can trick it by plugging in a gas generator.

This is what I am trying to understand, is it a legality thing, or an inverter thing? Is it something that can be changed to where you can use solar power during grid failure?

 

[mheslep]

A transfer switch, typically supplied with standby generators, that completely disconnects the residence from the grid would be required. Without a backup generator it is likely a different inverter (from the one Chi Meson describes) is needed that will free run without a grid voltage present.

 

[nsaspook]

Yes, I would have had to have a generator for when the grid went down.
This is what I am trying to understand, is it a legality thing, or an inverter thing? Is it something that can be changed to where you can use solar power during grid failure?

It's an inverter thing as the grid-tie inverter designers make several assumptions about the AC power line connection. The primary one is that it assumes the grid is a infinite load sink that can take all the power the inverter can deliver so the control feedback loop parameter is inverter current (maximizing output) as the grid controls the voltage stability.

 

[Ms Music]

Ahhh, I see!

Thanks to both of you.

 

[Cerlid]

Interesting I am seriously considering this as an investment, I live in the UK, and it is sometimes sunny so it may just work. Of course it's not the tropics, or Arizona or Southern Spain. But I think solar power is a good idea, I am just dithering over the initial cost. We used to have subsidised power ie we got a nice little bonus for installing, unfortunately the Conservatives got in and even though this will supply power to the national grid in the long run, it won't make many rich people richer in the short term; so they got rid of the incentives. However this thread has kinda inspired me to dig deeper than idiots with a will to remove concessions, to long term strategies, because they want to appeal to morons with a will to buy more yachts. I thank you. I'm not a communist, but the conservatives really piss me off atm. I didn't vote for the con/lib idiots. I applaud your will to become more than just a number. :)