Energy Matters Forums

[Jehu]

Hi all.

I'm new to this forum so I thought I might introduce myself with a question. I have been doing research on alternate energy for about the last 5 years now so I'm fairly cluey on the theory but there are a few questions I haven't found an answer to....yet. So here goes.

My family and I want to get a grid connect system for our home. We want solar and wind and we know that's all well and good but we want a little extra. Is there any issue with the feed in tariff and laws with connecting a biodiesel generator to the system to maximize the amount of power we can pump into the grid?

We figured that if we could get enough WVO from the local chip shops, this could be a way to earn a bit more money out of our energy supplier, that is if they will pay us. Since WVO is a waste product and it comes from a renewable source, it is technically carbon neutral so that really shouldn't be a problem pollution wise.

So, does anyone know anything about this? Would it work?

Also when they say that the system can only be a 10kW system, are they basically saying that we could theoretically produce 240kWh per day at 10kW per hour x 24 hours?

[Tracker]

Is there any issue with the feed in tariff and laws with connecting a biodiesel generator to the system to maximize the amount of power we can pump into the grid?

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The most obvious fact is that playing with any part of the PV system requires appropriate qualifications...
Therefore undertaking what you are thinking would be "Illegal"

Otherwise it's another 64K$ question which many have asked in various forms.
The problem is that the Inverter NEEDS some special limits on Voltage and Current, and impedance..

I suspect that no one will comment on your idea/question, because we would be afraid to try it.
Blowing a GCI trying, would be a big price to pay.

To undertake what you are thinking , you would have to rectify the AC.. The DC voltage would likely be within range for many inverters. but would the current ratings of the inverter be exceeded by the generator??
Who knows how the GCI would react to the heavy ripple on a supposed raw DC supply from PV Panels..
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[Jehu]

Well in regards to rectification, that is exactly what I had in mind. You have to do the same thing with a wind turbine so naturally the generator would have to output in DC, at the systems correct voltage and be regulated and filtered to provide nice clean ripple free power.

One of the things that got me thinking about this is on a form from Integral Energy http://www.integral.com.au/wps/wcm/connect/697ad80040f09a26ae6fbec60749251d/FPJ+7000+-+Application+for+Connection+of+a+Generator+June+2010.pdf?MOD=AJPERES

What if this 'addition' was installed by someone with the appropriate qualifications? And what side of the PV system does this apply to? Would you really need to get a licensed installer to put up a few more panels after the original system was installed? From memory, you do not need to have any qualifications to work on something if it is under 50V DC or 110V AC. Ok, the currents are pretty high but if you follow the standards for isolating circuits it's pretty safe.

I suppose the question is would an energy supplier actually pay out if you pumped into the grid 10kW per hour, 24/7/365?

[Tracker]

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You have to do the same thing with a wind turbine so naturally the generator would have to output in DC

1 -- But the WTG is a naturally current limited device
2 -- A WTD would normally be connected to a different Inverter
3 -- The voltage would be higher than ELV - Typically 150 to 400V
4 -- The System would be initially specified and approved.. After-changes would need to be approved..
5 -- They might become suspicious about PV generation after dark.

6 -- You have convinced yourself so go for it and good luck.. but the GCI will not be covered under warranty.
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[Jehu]

Humm, ok. Your answers raise more questions for me.

1. how is a WTG naturally current limited? Is it because it is usually based on a permanent magnet generator?
2. true but there are many on the market now that have multiple inputs so as to accept PV and wind on the same inverter.
3. ??? On the AC side yes but I can't see how anything will reach those levels on the DC side. Or are you saying that it can't be worked on because the low voltage DC is connected to mains voltage through the inverter? That would make sense.
4. That makes sense too but do you know of a link to this legislation?
5. Yeah, that was what I was worried about however isn't that one of the ideas of wind power in general in the first place? Power when the sun is not available?
6. Actually I'm far from convinced of it yet....in practice. In theory, yes, IRL, not quite yet. That's why I'm asking as many questions as I can from people who have done grid connect systems before.

[Tracker]

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I don't want to be responsible for convincing you that you are right on any point.
It would be silly to suggest that a generator was not any more than a petrol-driven-WTG.. . . A WTG is generically a smaller device than a Generator, and it's power will be limited to what the wind allows, and normally, has a protection device that dumps power, should the wind blow too fast.
WTG's are usually 3 phase, whereas a generator would be single phase
A 5Kw generator connected to a 2Kw GCI could be a small issue = A totally feral wtg...
A 2 Kw generator connected to a 5Kw GCI... Hmmm ... You can't get blood out of a stone !
Of certainty, I can say that the voltages we are talking about are NOT elv and hence require correct handling to remain legal.. It is a requirement of the local supply authority to approve of any grid-connected devices.
Not much else to comment upon.
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[Jehu]

Yeah, I understand what you mean about convincing me on any point. It's hard giving advice on the net and who knows what could come back and bite you if something went wrong. For that, I don't blame you in the least mate, lol.

So what dump load system do WTG's use now? Do they actually route power through a resistive load in a controller or does it just adjust the field strength of some of the stator coils to create a large enough Back EMF to slow the turbine down, like in the short the winding method to cause it to lock up?

A 5Kw generator connected to a 2Kw GCI could be a small issue = A totally feral wtg...
A 2 Kw generator connected to a 5Kw GCI... Hmmm ... You can't get blood out of a stone

Umm, Sorry, I don't quite understand what you are getting at there.

And BTW, what are you referring to when you say ELV?

So if the local grid authority has to inspect every grid connected device, does that mean if I wanted to make a diy wtg, I would have to get it inspected before I hooked it up to my system?

[Inspector]

What if this 'addition' was installed by someone with the appropriate qualifications? And what side of the PV system does this apply to? Would you really need to get a licensed installer to put up a few more panels after the original system was installed? From memory, you do not need to have any qualifications to work on something if it is under 50V DC or 110V AC. Ok, the currents are pretty high but if you follow the standards for isolating circuits it's pretty safe.

Of certainty, I can say that the voltages we are talking about are NOT elv and hence require correct handling to remain legal.. It is a requirement of the local supply authority to approve of any grid-connected devices.
Not much else to comment upon.

I was going to say exactly the same thing. Any more than one 170W+ panel and you're over the 50VDC value. I'm not 100% sure on the specifics of the DC voltage limits before it changes from ELV to LV but I could easily look it up in the AS3000 definitions but I left my copy at work.

As for adding extra panels, EA's ES1 document clearly states that 1. Alterations or additions to a generator are required to be submitted for approval prior to being undertaken (same form as used for the initial application) and 2. To be elligible for Solar Credits (ie: minimum 60c/kwh)
the system needs to be installed by a Clean Energy Council accreditted installer using approved panels and inverter(s). It might be that the inverter you'd need to use (for three sources) may not even be approved for use in Australia. I only know of two similar inverters - Sunny Backup which provides UPS-style backup when the grid fails, and Latronics I believe have an inverter which accepts wind and solar inputs on the one device.



Onto some of your other queries...

My family and I want to get a grid connect system for our home. We want solar and wind and we know that's all well and good but we want a little extra. Is there any issue with the feed in tariff and laws with connecting a biodiesel generator to the system to maximize the amount of power we can pump into the grid?

<snip>

Also when they say that the system can only be a 10kW system, are they basically saying that we could theoretically produce 240kWh per day at 10kW per hour x 24 hours?

I'm surprised Tracker didn't ask what state you're in as different states have different legislation. Assuming NSW, and in EA's area, you would not be permitted to have both wind and solar generation and still be elligible for gross metering. Alternative generation types may be acceptable, however EA's ES1 document only elaborates on the requirements for solar generation when net or gross metered. One of the other conditions is a limit of 10kw generator size. This is the NSW legislation (I don't have a link to it from home so you'll have to wait until I email it to my home email from work as I've cc'ed the link to numerous installers and customers) and EA's ES1 document implies the limit is an instantaneous output (ie: maximum peak of the inverter(s)). I believe they also keep an eye on the total panel kw but have not seen any that have 10kw inverter total and >10kw panel total... yet. My system inspection work instruction gives some examples of what is and isn't permitted, so you'll have to wait until Monday before I can make reference to it too. Interestingly, Integral Energy seem to be permitting systems with >10kw inverters (two 6kw) but up to 10kw of panels...

Then again, alot of what I've mentioned may not be relevant if you're in a different state or distribution area...

[Jehu]

<slaps forehead> Yeah probably should have mentioned that earlier. Yes I am in NSW. So no gross feed in for dual generation systems. Grrr, why do they have to muck us around all the time?

I do know that I can get a system that can do PV, wind and battery backup. We went and had a talk to the Solar Shop mob in Fyswick and they said that we can get a UPS style grid connect system through them that would do PV and wind.

Also why does an inverter have to have different inputs for PV and wind? Is it just an inverter thing that it can only handle so much current or is there something in the AS3000 about the limit that one circuit can run? I knew I should have brought one on that student special.

Because this is the thing that gets me. If the system is all running at the same voltage and everything is connected in parallel with blocking diodes and regulation, the inverter shouldn't know the difference weather it's PV, wind, generator, hydro or me peddaling a dynamo on a bike! Ok, the last one might not be such a good idea but I think you get the point. Why does it need multiple inputs?

[Inspector]

I'm not sure as I've never inspected a dual-source inverter before. Perhaps look up Latronics website and it might be explained there? They're an Australian company and locally built I think.