Simple Solar & Grid Tie Inverter

NiJK_2

Hi,
I have an Owl Energy Meter on the main supply for the house which seems to work fine.
I've also got a single 180W solar panel going through a cheap grid tie inverter and an Efergy meter. This seems to work fine too and indicates a power reading that seems reasonable.
However, I'd expect that turning off the inverter should cause the reading on the Owl to jump up by the same amount as the reading on the Efergy ie. with the inverter off, I should be drawing more power from my supply.
That doesn't appear to be the case. The Owl meter doesn't change. Is this low wattage (less than 100W) too low for the Owl to read properly?
I suppose what I'm asking is if the energy I appear to be generating is truly being exported to the house.
Anyone any experience of a simple setup like this?

Dave_Fowler

NiJK wrote: »

Hi,
I have an Owl Energy Meter on the main supply for the house which seems to work fine.
I've also got a single 180W solar panel going through a cheap grid tie inverter and an Efergy meter. This seems to work fine too and indicates a power reading that seems reasonable.
However, I'd expect that turning off the inverter should cause the reading on the Owl to jump up by the same amount as the reading on the Efergy ie. with the inverter off, I should be drawing more power from my supply.
That doesn't appear to be the case. The Owl meter doesn't change. Is this low wattage (less than 100W) too low for the Owl to read properly?
I suppose what I'm asking is if the energy I appear to be generating is truly being exported to the house.
Anyone any experience of a simple setup like this?

I find with my system that the Owl on the 'import side' never reads below 270W. If say it is reading an imported base load of 500W and the panels start to generate, the reading slowly drops to 270W as generation increases. It languishes at this reading for some time and then increases slowly as it starts to read the exported current.

Whilst it is around the 270W mark, turning on the computer (150W) usually has no effect on the reading. However when the reading is over 500W, turning on the computer causes the reading to change by 150W (either up or down depending on if importing or exporting at the time). I expect that if you have a reasonable load such as a heater which causes the Owl to read a kW or more, turning the panel inverter on or off should cause the reading to change. At low loads, the Owl is reading a load of spikes on the mains caused by SMPS which are at a low power factor. I suspect adding a pure sine-wave (pf = 1) from the inverter will just move the power factor without causing any change to the current being sensed by the Owl.

Dave F

NiJK_2

Thanks, Dave.
I was watching the meter yesterday and it was pretty much stopped with almost everything off and the panel in full sun. So I'm pretty confident it's working as I'd exepected and, as you say, it's the Owl meter that's not reading properly.
Your idea of having a larger load is a good one. I'll try that too.
Do you turn off your inverter overnight? Just wondering if there's any way power can flow the other way when the panels aren't generating.

EricMears

NiJK wrote: »

Do you turn off your inverter overnight? Just wondering if there's any way power can flow the other way when the panels aren't generating.

No need to turn inverter off overnight (In June you might have to do that after 10pm and be up again around 4am to turn it back on !)

There may be a very small current drawn when inverter in standby mode but it will be milliamps rather than serious current.

NiJK_2

That's good to know. I was thinking about putting it on a timer but, if I don't need to, leaving it on all the time is just a bit easier!

sunny900

Do these 'cheap grid tie invertors' work? i have recently bought one off ebay and connected it to a 40W solar panel. Am i right in saying any excess power will be perceived by the power company as being used by me and i will get billed for it?

EricMears

sunny900 wrote: »

Do these 'cheap grid tie invertors' work? i have recently bought one off ebay and connected it to a 40W solar panel. Am i right in saying any excess power will be perceived by the power company as being used by me and i will get billed for it?

Most meters would just stop when electricity is being exported. A few (e.g. look up threads about Siemens A2S) might perceive export as 'tampering' and would indeed charge you for exported power.

But you haven't got a lot to worry about with a 40W panel. Chances of your whole house consumption ever being less than 40W are very slim !

sunny900

Thanks, thinking about expanding the number of solar panels gradually over the next few months so just wanted to check

rogerblack

Is there any legal reason one can't connect up panels, and feed in to the grid?
Is it actually required legally to get approval to connect a (say) 300W grid-tie inverter?
(The idea would be to cover daytime baseline load, but clearly at times supply would exceed demand)

Clearly there are issues if your meter runs backwards - but if not, what possible problems could there be? (assuming that the meter will set an anti-tamper flag, what would the result of an investigation into this be)

Martyn1981

rogerblack wrote: »

Is there any legal reason one can't connect up panels, and feed in to the grid?
Is it actually required legally to get approval to connect a (say) 300W grid-tie inverter?
(The idea would be to cover daytime baseline load, but clearly at times supply would exceed demand)

Clearly there are issues if your meter runs backwards - but if not, what possible problems could there be? (assuming that the meter will set an anti-tamper flag, what would the result of an investigation into this be)

I can try to hunt down the official rules if you like, but here are my guesses:

1. The inverter needs to be certified for UK (EU?) use. The cheaper Chinese E-bay jobs, might not be. I think this can be checked by googling the inverter make and model, then looking for the tech/data/spec sheets and looking for the certificates. There should be scanned signed certificates available to view.

2. I think in the UK any GTI has to be hardwired into the consumer unit, many of the smaller ones might just plug into a socket.

3. The DNO has to be notified of any SSEG's (small scale electricity generator) and their approval sought.

Appreciate that this might appear incredibly pedantic for a 40W SP. Sorry!

Edit: The meter might (note I say might) not report the export. Meters show rEd to identify that reverse energy has been detected, so the meter reader knows something unusual has happened. But the point at which rEd appears (and stays permanently) will vary with meters, but may be around 10A.

Mart.

rogerblack

Martyn1981 wrote: »

I can try to hunt down the official rules if you like, but here are my guesses:

1. The inverter needs to be certified for UK (EU?) use. The cheaper Chinese E-bay jobs, might not be. I think this can be checked by googling the inverter make and model, then looking for the tech/data/spec sheets and looking for the certificates. There should be scanned signed certificates available to view.

2. I think in the UK any GTI has to be hardwired into the consumer unit, many of the smaller ones might just plug into a socket.

3. The DNO has to be notified of any SSEG's (small scale electricity generator) and their approval sought.

Appreciate that this might appear incredibly pedantic for a 40W SP. Sorry!

Edit: The meter might (note I say might) not report the export. Meters show rEd to identify that reverse energy has been detected, so the meter reader knows something unusual has happened. But the point at which rEd appears (and stays permanently) will vary with meters, but may be around 10A.

Mart.

1. - CE marking is one thing I do know about - it is not an offence to operate a non-CE marked appliance, only to sell it to customers. The importer would in principle be liable for fines/... - but if it's shipped direct from china...

2. 3. Is this an actual requirement for anything other than FIT/RO though?

I happen to have read the manual for my (new this year) meter, and it will start complaining about reverse energy at very small wattages - 20W comes to mind.

Oh - I quite understand the regulations are insane for small non FIT panels.
I was just wondering - not to put too fine a point on it - if you do it - what are the possible legal consequences.