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Solar (thermal) HWS vs PVs

Posted: Wed, 11 Sep 2013, 17:44
by Tritium_James
Sounds like a nice system would be an electric HWS you can run from the ~600V DC coming off the PV, so that the excess electrical capacity can be used, but without having to have a larger inverter to go with it.

Solar (thermal) HWS vs PVs

Posted: Wed, 11 Sep 2013, 18:18
by Vectrix150V
I wonder how you would go doing this - some sort of an MPPT reg would work well here for efficiency, you might be surprised how little power you would dissipate into the HWS when you are that far from the peak power point of those panels.

You would be better off (efficiency wise) running a grid tie inverter to do the MPPT function and running the HWS off that (although this really isn't possible with off-grid)

Solar (thermal) HWS vs PVs

Posted: Wed, 11 Sep 2013, 21:13
by Richo
Solar->MPPT reg->Battery->Phat Inverter->House->**MODULE**->HWS
**Module would need check Power in/power out and adjust PWM to suit so house and batteries has priority power and surplus goes to heating - same could be said for water pumping etc.
For off grid applications the inverter is already there so there is no reason to tie PV DC straight to HWS.
Different story for grid tie tho.

Solar (thermal) HWS vs PVs

Posted: Wed, 11 Sep 2013, 21:58
by offgridQLD
For off grid applications the inverter is already there so there is no reason to tie PV DC straight to HWS..

There is if you don't want to load your inverter up to much powering a element.


You would be better off (efficiency wise) running a grid tie inverter to do the MPPT function and running the HWS off that (although this really isn't possible with off-grid)

You can use a MPPT grid tie style inverter off grid. You just need a unit like the selectricics sp pro I linked to earlier that can do AC coupling.

kurt

Solar (thermal) HWS vs PVs

Posted: Thu, 12 Sep 2013, 14:40
by antiscab
I have thought for a long time about making a common DC bus between the internally MPPT in my grid tie inverter (which sits at around 390vdc), the dc bus on my split system aircon, a big 400v battery and the dc bus on my EV's charger

you add a heat pump HWS to that DC bus

I did see a bunch of heat pump HWS for sale for ~$1200, I'll have to dig it up again

Solar (thermal) HWS vs PVs

Posted: Thu, 12 Sep 2013, 14:45
by antiscab
here we go, it was these guys:

heat pump hws

same guys that are selling the 2.5kw grid inverters for $100

Solar (thermal) HWS vs PVs

Posted: Thu, 12 Sep 2013, 15:43
by Vectrix150V
Those 2.5Kw grid connect inverters are actually illegal to use unfortunately, their anti-islanding function locks out for 30 seconds, not 60 (and they are transformer based and really, really heavy) and have some serious reliability issues.

Great to put a chain on and use as a boat anchor though :)

Motowizza (sellers) got popular bringing in those Chinese 66cc and 50cc frame mount 2 stroke engines for bicycles.

They seem to sell anything and everything these days though.