I would try and convince western power that if the installation was passed with a 6KW wind turbine, then the addition of 2KW of pv is of no consequence.Janco2 wrote:A very interesting thread, especially the informative data.
We have had a grid connected 6kW wind turbine for 2 years and although this generates twice as much electricity as we use, we still find we need to import half of what we use due to the intermittent nature of wind.
Consequently we have been trying to add a 2kW array of solar PV to our system in order to reduce our import from the grid.
After originally being given a verbal go ahead by Western Power, this has now been retracted
'due to length of ug service cable from local transformer'
'source impedence is circa 0.48ohms thus 6+2kW of export would create 32A x 0.48ohms = circa 16V rise and probably trip G83OV protection'
'To reduce source impedence would need existing ug service cable to be overlaid with a larger cable at a cost of £6,600+VAT' to be paid by us!
A data logger (recording voltmeter) has now been installed on our premises to record what is happening now.
We are not in a position to pay out this extra cost.
Has anyone any ideas as to how to proceed. Could it be worthwhile having a bank of batteries with less solar PV? If so how can this be used in a power failure? Would we need a separate system?
Any other suggestions or thoughts would be appreciated.
Although they allow for the worst case, I dont believe that full PV and full wind power prduction will EVER co-incide in the UK.
Have you ever seen strong wind and bright sun at the same time? (thats probably 60 mph wind and full steady bright sun)
If they wont accept this, then approach the suppliers of the grid tie inverters, to see if the total output of the two inverters can be restricted to 6KW, with the surplus being dumped. Although this sounds wastfull, I doubt in practice if any energy would actualy be dumped.
A backup battery is allways desirable in case of grid failure, but wont help re this "excessive" backfeeding, since the battery might be already fully charged at the time of surplus production.
Another option would be to inquire if any device can be installed to monitor the net outflow of energy from the house, and energise a dump load if this eceeds 6KW.
For the reasons given above, production is unlikely to exceed 6KW, net outflow is even more unlikely to exceed 6KW since some power would be being used at the time.
I presume that this is a single phase service? if two or three phase, then connecting the two grid tie inverters to different phases should be no problem.
