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  • C M Varughese 

Solar Power Systems | Some Key Facts

Solar Power Systems – Facts to be known :


  • Solar PV System generate 4kWHr DC Power (4 units )/Kw average per day at PV end in Kerala .On conversion to AC the yield is 3 to 3.5 units per day .Average 100 units per months per Kw ,on higher kWs yield increases proportionally .

  • Space requirements- 100 sq.ft per Kw and increases proportionally as Kw increases .Space should be south oriented in Kerala ,without shade .

  • Standard mounting on flat roof at 10-11 deg centigrade south oriented , Possible to mount on inclined roof ,tiled roof as well as sheet roof ,also above car porch and ground mounted .

  • Type and Selection of Solar PV Systems - Off Grid (with battery ) :


  1. Useful for areas where mains failures and fluctuations are frequent .Battery per Kw 4x150AH C10 Tubular for residential and 2x150AH for office ,day time use .

  2. Load be distributed to contain PCU rating and PV generation ,say 3-3.5 units per Kw .

  3. Priority load shall be Lights,Fans ,TV etc .

  4. PCU (Solar Inverter ) rating 1Kva o.k if the Fridge-285L/DL is inverter type ,other wise 2Kw may be needed .

  5. For AC ,1.5T AC of inverter type can be connected on 3Kva PCU ,other type AC of 1.5T may need 6/7.5 Kva PCU . 1.5 T AC ,average energy consumption 8Hrs may be 8 units .

  6. On maximum energy conservation and Energy Efficiency exercise only go for Solar ,limit 80% of energy consumption on solar and balance on Mains on an average .

  7. Avoid connecting high surge loads (low duration running ) like motors on Solar if possible .

  8. Advantage OFF GRID-Give a steady , stable ,Clean power 24Hrs (depending connected load rating )


  • Type and Selection of Solar PV Systems - Grid Connected


  1. Good for mains stable steady

  2. Just generate energy and get bill reduced through Net metering

  3. Power Quality same as mains

  4. Good for large commercial complexes ,Hospitals ,Institutions etc where own substation available with less fluctuations and failures .


  • Pricing at an average :


  1. Off Grid 1Kw-10Kw with 4x150AH C10 battery/Kw –Rs.1.3 to 1.5L /Kw depending BOQ and higher kWs price increases almost proportionally as Battery and PVs Nos increase straight up which are major price part of the systems .

  2. On Grid -1-5Kw Rs.90k to Rs.3.5L ,5-10KW Rs.3.5L to Rs.6.5 L .Per W price reduces as rating goes up .

  3. Above prices for standard items and may vary depending change in roofing ,cable length etc


  • Maintenance –


  1. Cleaning the PVs once in a month with clean water a must , birds drops shall be cleared as soon as located .

  2. Battery top up shall be checked once in 6 months .

  3. Take readings of the system from the display once in a month-W ,kWHr ,AC voltage , Load % ,Frequency ,Battery Voltage ,charging current , PV Current etc during sunny hrs as well as during night peak .

  4. Life of Solar PVs aprox 25 Years ,Battery 7-8 Years and PCU 15 Years on right selection ,usage and maintenance .

  5. Pls be reminded battery life is number of charge discharge cycles with ref to depth of discharge ,for above application and life solar batteries are designed for 50% depth of discharge .


  • Solar PVs –


  1. Mono crystalline and Polycrystalline PVs are generally used and Mono is having 1.5% conversion efficiency over Poly but price almost 5% more .But yield for a particular Wp panel same irrespective of Mono or Poly ,difference is mono need little space less for mounting and so advantageous on large plants by space .

  2. MPPT Charge controller yield average 20% energy more over PWM charger and available as inbuilt with PCUs ,shall not be there for single battery single PV system .

  3. As solar Off Grid systems generally work at 20-30% load normally the efficiency at low load is important than full load .


  • BOS –Balance of Systems ,even though cost share small BOS important to keep the system protected ,keep system running without failures .


  1. Mounting structure shall be GI for long life without rusting .

  2. Cable sizes shall be for <3% drop in PV side and shall be UV protected .

  3. SPD (Surge protection device ),shall be used in SPV System

  4. DC MCB for PV isolation shall be used

  5. Earthing shall be done as per standard

  6. And Lightening arrestors shall be used as part of SPV systems


  • Net Metering and Connectivity :


  1. Net Meter Available from EB on rent and shall be replaced for standard meter on Grid connected PV system and Grid connectivity on Inspection and approval by KSEB and Inspectorate . Up to 10Kw only KSEB inspection.

  2. Rs.1000 for for feasibility study and Rs.1000 per Kw on Grid connection fee as of now

  3. Generation based incentive Rs.1.0 /unit available for OFF Grid System from KSEB .


  • Energy Conservation -the habit by which we reduce energy consumption by reducing consumption:


  1. ELCB must for all electrical circuits

  2. Keeping lights and fans off on not in use

  3. Use lower rated lamps or reducing light intensity etc as required

  4. Switch off standby devices not in use


  • Energy Efficiency ,using equipments and devices of higher efficiency :


  1. Fluorescent tubes and CFL bulbs be replaced with LED tubes and LED bulbs of 50% power rating keeping the lux same.

  2. Replace old fans with BLDC fans

  3. Replace old Fridges and ACs with 5 Star rated Fridges and ACs

  4. Replace the Motors with energy efficient motors .


Compiled by :

C M Varughese 

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