UKH

We are a community owned hydro scheme 425Kw and are being charged £3K+ year in various standing/capacity charges for our import power supply. I am looking at installing PV/battery/backup alternator to cover us over dry times when we are not generating (parasitic load < 5kw) . My question is do I need an external import power supply? 

In terms of power:

• Do you have data on import loads over the last few years?  How did the periods of drought affect your supply?  You need to model the size of PV/battery/generator needed and to consider their reliability.  With PV + battery you can tolerate generator servicing etc and make more efficient use of a smaller generator by load smoothing a bit with the batteries.

In terms of system stability:

• Does the external power supply also absorb surplus power that will regularly occur as an export?  If so, how are you going to manage excess power when in island mode?  Will you need to intelligently limit the hydro flow rate, or the power taken out by the hydro connected generator/alternator, or use diversion control to a very large thermal diversion bank?   Or some mix of the above.

I manage a small solar/generator system that uses ohmic diversion control when in island mode (as in-band signalling to the inverter to demand limit would require parameters being set outside of the relevant grid code and it's not practical to reconfigure it between grid- and island- modes).  It's a PITA.   

Yes have usage figures for past year, max load is 0.9 Kw. With May 23 driest month total usage 316 KwHrs.

We have a 450 Kw grid connection but our max power output is 425Kw. This is regulated via govener on turbine / spear open positions admitting water to turbine. Also by G59 protection/ACB settings.

If we get a grid fault and cannot export then system trips and after 3 start retries must be manually reset.

I am not an electrical engineer but we do have one on our board, if accepteable to yourself I can arrange a teams meet to (virtually) show you our scheme. Send me an email.