I would like to share few inputs regarding solar DC and AC water pumping with the forum here; This explains why is it better to convert existing pumps to run on solar;
Factor Solar AC water Pumping Solar DC Water Pumping Cost Less when compared to DC High Capacities Available From Indian manufacturers 0.5Hp - 25Hp Max 2 or 3 hp Ability to run on Mains During night/ when solar absent Yes No Installation, maintenance & servicing Easy Difficult Available applications Submersible/monoblock/open-well Mostly submersible only Reliablity Good Poor
Since solar DC water pumping is predominantly in nascent stage and being mostly imported the cost of such pumps are high when compared to solar AC water pumping.Because of this servicing becomes a major issue in case of downtime.
Next, the solar DC pumps do not have a option to connect/run on AC power supply. In case of solar non-available/weak there is no contingency available making it extremely evasive.
The Solar DC pump’s are unreliable basically due to non-availability/rare availability of spare parts/replacement parts and last but not the least, solar DC pumps can be used only for submersible borewell applications unlike the AC counterparts.
Any local mechanic will rewind motor winding or troubleshoot AC pump, but expecting such luxury with DC pumps, especially in India will take time.
Last but not the least, MNRE has ammended the benchmark costs vide No. 5/23//2009-P&C (Pt. III) on 30th May 2013 for FY 2013 - 2014 for solar water pumping @ Rs.190/wp for Solar DC pumping & Rs.161.50/wp for Solar AC pumping both for capacities upto 5Hp.([url=http://mnre.gov.in/file-manager/UserFiles/amendmends-benchmarkcost-aa-jnnsm-2013-14.pdf]http://mnre.gov.in/file-manager/UserFiles/amendmends-benchmarkcost-aa-jnnsm-2013-14.pdf[/url])
Lets take a example of both the cases @ 2Hp
Basic Cost of Solar DC pumping will be 2000watts * Rs.190 = Rs.3,80,000 after 30% subsidy - Rs.2,66,000
Basic Cost of Solar AC pumping will be 2000watts * Rs.161.50 = Rs.3,23,000 after 30% subsidy - Rs.2,26,100.This gets cheaper by roughly 10 ~ 15% more if you already have the AC pump
So here’s the bottomline;IMHO If you choose solar for water pumping;
a)Converting your existing AC pump to run on solar is cheap and effective among options
b)Erecting a new AC pump and converting it to run on solar is next best
c)Erecting DC pump is the above two options are unavailable
You may all correct me if am wrong.
Hope this helps!
Greencurrent Solar Energy Systems