Solar pumps are commonly being used for irrigation water pumping applications and the common capacity being 1 hp to 10 hp. Solar micro pumps of 0.25 and 0.5 hp are being used for drinking water application. A solar micro pump of 200 W, 24 V DC, BLDC motor, 5800 rpm, 16 lpm, 15 m total head surface pump with 250 W solar panel and controller was tested and the results are analysed in this article.
Two tests were carried out. One test through a solar array simulator for a standard daily radiation of 7.15 kWh/m2 day with summer radiation profile. Another test directly thought the solar PV module on normal sunlight and the results are presented.
Hot profile: The pump was installed over a water sump with piping and instrumentation to maintain a constant head. Through the simulator, the standard summer hot radiation profile and solar PV module parameters were applied and the resultant DC power was fed to the controller and then to the motor. The variation of input power and water discharge from the pump for a constant head of 15 m with time is plotted in Figure 1. The hot profile ran for 9 hours and the pump ran from 60 W to 200 W and the flow was 2 lpm to 16 lpm. The variation of solar radiation and Maximum Power Point Tracking (MPPT) with time is plotted in Figure 2. The motor-pump operated between the radiation of 300 W/m2 to 900 W/m2. The MPPT varied from 88.5 to 98%. The water discharge was 6,680 litres/day.
Realisitc profile: The solar PV module was kept in direct sunlight and the power generated was fed to the controller and then to the motor. The variation of solar radiation with time is plotted in Figure 3. The motor-pump operated between the radiation of 300 W/m2 to 820 W/m2 (available on the particular day). The variation of input power and water discharge from the pump for a constant head of 15 m with time is plotted in Figure 4. The realistic profile ran for 7 hours and the pump ran from 75 W to 180 W and the flow was 3 lpm to 15.8 lpm. The water discharge (extrapolated to 7.15 kWh/m2/day) was 6,750 litres/day.
The shut off head of the pump was 26 m and the all-day water to wire efficiency was 17.8 %.
A 200 W solar micro pump was tested with simulation and also with realistic profile and the results are presented. Hot profile MPPT varied from 88.5 to 98 %. The water discharged per day was 6680-6750 litres at a constant head of 15 m and the all-day water to wire efficiency was 17.8 %.
Jothibasu has B. Tech in Mech. Engg. and M.Tech in Thermal Engg. He is presently working as Joint Director with Central Power Research Institute, Bangalore. He has been taking care of Solar Pump Testing and also providing Energy Audit service to Process industries, Buildings, Hydro, Gas, DG & Thermal power stations. He has 40 technical papers to his credit. He is a certified & accredited Energy Auditor of BEE, New Delhi, and a Life Member of SEEM.