Excess Solar generation - not grid connected (G-59)

If the PV system is grid-tied, then it's normal to export any excess electricity.  But if export is forbidden because the local substation couldn't cope with export, then the only option would be to reduce the output of the inverter.  If this happened, the excess electricity would be lost within the panels.  Any electrons generated within the panels, and not pulled out by the inverter, would re-combine into the silicon without going anywhere.


It's common for micro-generation schemes to have no export meter.  My little system of solar panels on the roof has a generation meter for FIT purposes, but nobody is measuring what I export.  That doesn't stop it exporting any electricity I'm not using.  I am given a "deemed" payment on the assumption that I export about 50% of what I generate.

Did we really have any serious problems years ago with a 60 Watt bare filament bulb on a bathroom ceiling held by a "Home Office Skirted" lamp holder? 


Shocks, explosions, fires or world society meltdown?


Z.


Gremlins! This was not posted here.

Isn't it the case that excess generation not required by any load or battery is only really excess potential energy. - not actual energy...the voltage will be there at the PV output and inverter input but no current drawn off by the grid or any load so therefore no energy loss....just potential energy loss.


There is a potential at all socket outlets....but no power until something is plugged in and draws current.

Export in principle seems best idea providing local switchgear can support, i image power will fluctuate , perhaps suggest the power genrated is profiled , then connectivity sized for maximum input . ie; transformers and power factor correction, which may need to be investigated how the co it may only be 100 KvA swich gear for example  . When I did multicycle stuff for a  HVDC  import experiments  and conversion to AC from France  many years ago the industrial connectors overheated and it was rendered unusable ie; it blew up.  The other possibility is to work with a water company to pump water for storage , relatively complex numbers but currently battaerise require mainetnace every 3 - 5 years very poor in my personal opiniion.

Grid tie inverters can be configured in two ways;


1. Without Export Limitation: Here, whatever power the Solar PV panels generate, is converted to synchronised AC and fed into the power system of the building, irregardless of the building load. Therefore the building load is NOT monitored, and thus the inverter system operates in OPEN LOOP. Therefore any power generated by the inverters is either fed partially into the building load (if building load is more than generated Ac Power), or partially fed into the grid (If building load is less than the generated AC Power). In other words, the building load sees a mix of Grid power and PV power (When load demand exceeds PV generation), and the excess balance is fed into the grid (When load demand is below PV power generation). This happens dynamically with changes in irradiance, and building load. Its here that one earns from a FIT arrangement by earning from exported Energy.


2. With Export Limitation: Here, the building load is monitored, and Solar PV power generation is monitored. If export is to be curtailed to zer0, then the controller processes the Building AC load, and Inverter AC output, and thus controls the inverter output not to exceed the building load. If there is generation potential from the PV modules (full irradiance), and there is little or no load demand from the building, then the DC side of the inverter (Internal Power Electronics connected to the AC side of the inverter internally) will use the MPPT to control the PV array output dc current, and pull just exactly what's required (There is no really wasted power, its just not converted to begin with, otherwise if this was allowed, the panels would heat up unnecessarily and this would cause other problems as you can imagine). Therefore in this mode, the Inverter operates in CLOSED LOOP. With this technique, no power is exported to the grid, and all generated power is consumed by the building load. Therefore this method is used when there is no FIT contract and you are not allowed to feed into the grid for whatever the reason (Weak grid, no FIT etc).


How fast the control loop reacts to changes in load current, such as to maintain zer0 grid export, is a story for another day....

Thank you All for your responses.


So to summarise, it seems like the inverters are operating in "Open Loop" mode as the sites are generating excess solar which is not used by the buildings' energy demand. Also the excess solar is being measured through an "export channel" as the buildings do not have a G-59 connection in place.


So, does this excess solar still end up being exported into the grid?


Thank you!