Three phase Solar Pump 1. Description: Our renewable energy team at Whirlybird Electronics Pvt. Ltd has developed VFD based solar pumping solution for 3hp and higher capacity which are currently deployed across Bihar. Since past 8 months we have been working on a smaller Type-I pump as per MNRE guideline to meet following requirements: Water flux: 40,000 Liters per day from 30 meter head Shutoff head: 50 meter PV modules: 1200 watts having efficiency better than 14%. We have developed a customized 3 Phase inverter which works with low DC input voltage to run custom made 3 phase submersible pumps. Appendix-I describes reasons for custom design of Inverter and pump. 2. Details of prototype: 2.1 The Pump: We use a custom made 1 hp submersible pump which has been manufactured by Mahavir submersibles as per our specs. It pumps 4K to 5K LPH from 30m depth. 2.2 The Inverter: We have designed a multipurpose power converter which takes DC input from PV modules (100-150V DC) and converts it to 50V AC three Phase. An additional 14V DC @ 20A output has been provided to charge lead acid battery for household use. This inverter can run on single phase mode using 2 of its 3 IGBT pairs. We offer a 1KW step up transformer to boost 50V AC to 230VAC so that it can be used for home appliances. Multipurpose power converter Low voltage, 3 phase pump 220 vac for home appliances 1200W PV Modules DC/DC 3 phase, 50 vac for irrigation pump 12V battery charger for DC home appliances like LED lights etc Inverter cum charger prototype
2.3 Structure for PV modules: A pair of PV modules will be mounted on a foldable structure for easy transport over cart or solders. To setup pump, unfold modules and put it on ground adjusting elevation by supporting bar provided for this purpose. Kindly refer to following diagrams. Estimated weight of each pair is around 65-70 Kg including structure. Lock two modules together Ready for transport Unfold 2 pairs and connect them to power converter and pump Transport them on cart or on solders depending on terrain 3. Testing of prototype: We have tested this prototype as per MNRE guidelines in controlled environment. Water flow was regulated through valve to pressure head, magnetic flow meter was used to measure water flux and a pyranometer was used to measure sun irradiance. 3.1 Test conditions: PV modules: Pump type: Solar Irradiance: Water head: 1200 watt (4 modules of 300 watt each) 1 hp 3 phase, 50V AC 800 Watt/sqr meter 30 meter 3.2 Test results: Power from PV: 900 watt Inverter output: 820 watt Inverter efficiency: 91% Water Flux: 74 LPM or 4500 Ltr/ Hr Pressure head: 29.5 meter Screenshot of pump testing instrumentation
3.3 Capability: A PV based system can never beat a diesel pump-set in terms of upfront capital required. What we are trying to do here is to make a solar pump with reasonably good efficiency, ruggedness and diversified utility within a cost budget of INR 100,000/-. 3.4 Viability: We wanted to make system in hand as versatile as possible. So when solar pump is not in use, it can be used as an off-grid inverter with 220V AC @ 1000 Watt output. It could be also be used to charge a 150 to 200 AH lead acid battery to run some of DC based house appliances like LED lamps etc. 220V AC home appliances including 0.5 hp single phase pump will run during day time through direct power conversion without backup A 200 AH battery could be charged for DC loads like LED lights etc. 3.5 Affordability: The estimated cost of complete system including PV modules, Submersible Pump, Inverter and Structure is INR 80,000/-. Refer Appendix-II for cost breakup. 3.6 Feasibility: We have completed design and prototype testing. We need to implement safety and protection features like over load and over temperature protection etc to make it rugged. Active cooling of power converter is also an issue of concern, we want to make it more efficient >= 95% so that the heat can be managed by passive cooling. 3.7 Portability: Complete system is divided in 3 components. Solar modules with supporting structure having weight around 120 Kg in two sets of 60 Kg each for easy transport and handling, a submersible or surface pump of 20-30 Kg and Inverter around 5 Kg. unfold PV modules, connect 2 wires to inverter and 3 wires to pump, unit is up and running. 3.8 Robustness: PV modules and Inverter are two most fragile components, the support structure for PV modules could be design in a way to strengthen the modules apart from serving as mounting base. Passive cooling will allow us to make fully enclosed inverter which meet IP55 rating and dust and splash resistance.
4. Team and relevant work experience: Year 2011 we started development of solar pumping system. Early deigns were based on COTS VFD, we implemented a close loop control method to keep PV modules at maximum power point by controlling the RPM of pump. It is a very common and robust method to run a three phase pump from PV modules. There has been a demand for smaller (1 to 2 hp) solar pump, which people can afford without government subsidy. At whirlybird a dedicated team of 3 has been working on solar pumping solution and 1 hp system is our top priority right now. Pump controller supplied to Claro Energy in Bihar around 50 installations of 7.5hp each Remote monitoring of pump performance over GPRS network 5hp and 10 hp solar pump controller based on Toshiba VFD. Already Deployed in Bihar on commercial scale.
Appendix-I Typically 1 HP pump meets type-i requirement of water flux and head. If we choose to use a COTS three or single phase pump we need 400 to 600 VDC input on inverter s input side to meet correct AC output levels. There are two main issues which we have faced to meet above voltage level. 1. To generate 400 or 600 VDC out of 1200W PV modules we would require many PV modules of small wattage (less than 100W) in series. Standard 300W modules are cheapest because they are used in mass scale, smaller modules are more expensive, a 50W module may be 1.5 times more expensive than 300W on per watt basis. 2. High DC voltage in a portable system raises safety concerns where things are wet all around So we decided to develop a low voltage 3 phase AC pump with input voltage 50VAC and input current 20A. There are 2 main drawbacks in this pump: 1. Any COTS VFD (3 phase inverter) will not meet these voltage and current requirements; hence we were forced to make one of this kind. 2. Repairing this pump locally needs some special care. Appendix-II The cost estimate given here are for production version of minimum 100 units per lot Component Cost (INR) PV modules 1200W @ INR 40/watt 48,000/- 1 HP submersible Pump 15,000/- 3 Phase Inverter with MPPT and 20A battery charger 8,500/- Structure for PV mounting 5,000/- Total 76,500/- Optional 500W off-grid inverter 3,000/- Total 79,500/-