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Forum Index : Solar : Solar Rebates
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raymond thomson Newbie  Joined: 19/09/2013 Location: AustraliaPosts: 36 |
A few months ago the Treasurer asked why the electricity bill was creeping up and why we were no longer getting rebates for our Solar contribution. This prompted me to pop the quarterly billing data into a spreadsheet and sure enough the average number of solar units credited took a noticeable dive in May 2013. The average for eight periods prior was 776 units and for seven periods since is 555 units, about 70%. I enquired of our installer and was told that our usage pattern had probably changed but did get to download the data from the Sunny Boy inverter which he thought would satisfy me! I also read the meters daily and plotted our day/night usage for a month to fully understand where the watts were going. It didn't answer the question. However while browsing the BS contributions recently it occurred to me that our neighbour installed a 5kw system on the adjacent untenanted property and I have just confirmed that our drop-off coincides with that installation coming on-line. We are at the end of a line and sharing a small transformer on the pole. So is it a coincidence? Is the energy company "refusing" to accept power, or perhaps limiting the amount of power that is available to them? Has anyone experienced this or have any ideas? Thanks Raymond. |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Hi Raymond I suspect its because the grid voltage is high. The grid connected inverters need to pump amps back into the grid to wind the power meter backwards. They do this by raising their output voltage above the grid voltage, so current flows back into the grid. In effect, this raises the grid voltage a little. But the inverter can only raise the grid voltage so far, if the grid voltage is already high then the inverter cant feed as many amps back into the grid. If you neighbour is also feeding back to the grid, then yep, its raised the grid voltage, and therefore your system cant feed as many amps as it once did. So during the day your feeding less power out, but at night using the same power in as before, therefore your bill has gone up. No easy solution, it was one of those situations that was bound to happen as more and more people install grid connect solar. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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yahoo2 Guru  Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
If it really is high voltage then it should be fairly obvious. The mains voltage rises till one inverter trips out and tries to reconnect repeatedly. out of the factory I think a SMA inverter is usually set to 265 volts trip point. If you are using the sunny explorer software on a computer(with Bluetooth) it is not hard to see the trip outs on the graphs (production drops to zero) and I think they should be logged as an error as well. I'm confused, no wait... maybe I'm not... |
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Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
Its been a while since i have poked around with the software settings of a sunny boy but i think you can increase the maximum output line voltage in software for a SMA inverter. SMA is one of the few inverters that allow software changes to be made, if you have bluetooth installed in the inverter. The required program to access it can be downloaded from SMA, but the catch is ...... you need an installer code to access the internal software, thats not a problem, the problem is once an installer code is entered only that installer code will work there after, no other installer code will be excepted. For this reason i write the code used inside the cover with a texta pen. In most cases the installer code has never been entered and just the factory settings remain, so you might be lucky and can access the software. The only other way to gain access is to get a replacement eeprom chip from SMA and make a fresh start, as i have also done several times. Or switch the breaker off on your neighbour's system for a few weeks and see if your feed in increases. Pete. Sometimes it just works |
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| yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
I would probably check off a few other possible reasons for the drop in exported production first. the DC volts and amps on the sunny boys LCD should add up to close to the panel specs at max power point when it is a sunny afternoon. it shouldn't be hard to work out if you know how many panels are in each string. this time of year the peak watts should also go close to matching the rated size of the system. you can look at the inverter output AC voltage and compare it to the voltage from a socket in the house. compare it to your neighbours inverter on the same transformer and the next house on a separate transformer. a significant difference in voltage would indicate an AC wiring or connection fault or perhaps a sick transformer. you can tap the sunny boy lcd screen and get the daily graph up on a good sunny day (assuming the panels are facing north) it should have a nice bell shaped curve. if there is a flat section maybe the inverter is getting hot and clipping the power. perhaps the airflow is blocked around the heatsinks or the fan doesn't function. the older sunny boy inverters dont hold monthly or yearly yield data, makes it pretty hard to calculate the household total power usage if you haven't written it down each month. The newer ones do, so it is possible to use the inverters monthly yield numbers in 3 month blocks and subtract the exported power (on the bill)add the power consumed from the mains to get a total for household use. I'm confused, no wait... maybe I'm not... |
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| raymond thomson Newbie Joined: 19/09/2013 Location: AustraliaPosts: 36 |
Hi Guys Thankyou all for your inputs. I get your argument, Glenn, and it seems most likely. I will get to look again at the data from the Sunny Boy to see if there is any sign of the cut-back or any errors. Not sure I want to investigate the software - a bit beyond me these days - and I can't see any prospect of Ergon Energy coming to the party  . As to switching off the neighbour's connection I am not sure that is a goer  !
Thanks again Raymond |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Here's a conspiracy theory for you... If the power company where to increase the grid voltage slightly, people with grid feed inverters would have to pay more on their power bills, giving said power company a boost in income. The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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