Hybrid without batteries or grid tied with Auto transfer switch? Will it work?

[barnaby91]

I am in the process of designing a system for deployment in Southern Africa and looking for some help/input from fellow solar installers and enthusiasts. Their grid is somewhat hopeless and is often turned off due to lack of supply - load shedding. I am looking at the possibilities I have ahead of me, I understand a hybrid inverter and PV system tied to batteries would provide backup power when the grid will be out but I was wondering if there is another option with the use of an automatic transfer switch in association with a grid tied PV system. Solar + Storage is still very expensive (even more so in Africa) and the majority of households will be unable to afford the extra cost of batteries.

If an automatic transfer switch was fitted to a grid tied PV system with no batteries, is there a way of disabling the anti-islanding or enabling backup power on standard grid tie inverters. Or are there any inverters that have this option. The majority of installed PV systems will not be large enough to allow off-grid, but most of the load-shedding takes place in the afternoons or when sun is usually out and shining, hence my question of getting the grid tied solar to keep producing to tie the households over for the couple of hours of load shedding.

I'm aware that most of the earthing arrangements are TNCS systems, so a local TT system will have to be installed for safety.

Does anyone know if a hybrid inverter will perform to the use I need without batteries attached? Also, what it the switchover time of a hybrid battery system/automatic transfer switch - is it quick enough not to disrupt electrical equipment (similar to UPS)

When selecting automatic transfer switches, what sort of specs are needed for domestic with regards to poles and amp ratings. Does it need to be sized to the incoming grid supply or the loads in the household? Most incoming main feeds will be 100A 240V, but I imagine in most households they will be using a lot less than that.

To make use of any energy generated if there isn't a demand for draw in the household I was thinking maybe a dump load or immersion heater similar to the solar iboost could be used? Any experience with them, and would they be suitable for my idea. Can they be daisy chained for system sizes greater than the 3kW?

Many thanks in advance, Barns

 

[Worcester]

Loads of info take a look at Victron https://www.victronenergy.com give the guys at Wind and Sun http://www.windandsun.co.uk/ or Hollybrook Power Supplies http://www.hollybrookps.co.uk/

 

[Gavin A]

no, you'll not be able to do it without batteries, the inverters won't cope with the fluctuations in power requirements and generation properly IMO.

Even a 120Ah leisure battery would provide buffering to level out this variability and allow for higher peaks eg when fridge / air con compressors start up.

 

[sgt_woulds]

I agree that a small battery bank is required to smooth things out. The trouble is that a small battery would cycle so often it would be scrap in no time.

That is a major problem in Africa I understand; there are no battery recycling facilities.

Friends who have worked on charity trips have reported piles of dead LA batteries left in the open and leaching into the ground.

I believe a few charities have started to require Nife batteries for this very reason - upfront cost is enormous but you then have a battery for life and one that is very robust.

I'm sorry this doesn't answer your immediate question, but I would suggest contacting SolarAid ( http://www.solar-aid.org ) as they have many years experience with solar on the African grid.

Or you could try Renesola Micro inverters - my ones keep generating even when there is a power cut for up to 10 minutes - guess how I found that out! They do stop when you flick on a kettle though...