Date: 4-2-2017 Solar water pumping system Goulds, 0.75HP 230Vac, 120psi Test Report - This report quantitatively documents the tested performance of a solar submersible water pumping system consisting of a specific submersible AC pump powered by solar PV panels in conjunction with a PicoCell controller. Solar PV panels are the DC input for the PicoCell controller and the single phase submersible AC pump is connected to the PicoCell s output, as shown in Figure 1 below. Solar PV panels are connected in series in order to provide the required DC solar power to the PicoCell controller that is generating the appropriate AC output for a specific AC pump. The PicoCell controller can be used for running any AC pump from solar PV independent of phase, voltage and frequency. For a given AC pump specification, PicoCell is capable of generating a true sinewave with a variable frequency range of 30-60Hz. By varying the frequency, PicoCell controls the pump s speed in the range between 50 and 100% of rated speed, depending on the power availability from the solar panels (PV input). Figure 1: Solar AC pumping system diagram In this particular setup, a 0.75HP, 230Vac, 60Hz, single-phase (2-wire) submersible pump was tested with the PicoCell controller powered by 7-10 common (60cells, 230-270W) PV panels wired in series. The technical specification of the AC pump is provided in the table 1. Table 1: Technical specification of tested AC pump: Submersible pump: Goulds 10CS07412CL Power: 0.75HP Voltage: 230V Current: 6.8A Frequency: 60Hz Pressure: 120psi Max flow: 16 gpm Speed: 3450rpm MFG# G1644106 SunTech Drive, Inc. www.suntechdrive.com 5485 Conestoga Court, Suite 250, Boulder, 80301, Colorado
The Goulds submersible AC water pump was tested for several different pressures (heads) versus flow, and it s nominal pump curve (for 60Hz) is shown in figure 2. At low back pressure of the pump (60 psi) the flow is above 16gpm. Once the pressure starts rising, the flow drops, so for 110psi the flow drops to just above 8gpm. Figure 2: 0.75HP, 230Vac solar submersible water pump specification water flow vs. head When the pump is controlled by the PicoCell, which is connected to the solar PV panels, the PicoCell will run the pump at different speed frequency range: 30-60Hz, and hence the pump will generate variable flow at variable available solar PV power, for the same head (pressure setting). In order to start the pump at 30Hz, at any head, it takes 200W from solar PV panels. To run the pump at nominal 60Hz, it takes 1400-1500W, depending on the actual head (lower the head more power required). Figure 3: Power requirements of 0.75HP, 230Vac solar submersible water pump 2
Depending on the location where this solar pumping system is installed, it will require more or less total PV capacity to achieve these results. There are 6 solar zones that are shown in Figure 3. Zone 6 has the most solar insolation (6-7 kwh/m 2 /day), zone 5 is in the solar insolation of 5-6 6-7 kwh/m 2 /day, while zone 1 has the least amount of sun (1-2 kwh/m 2 /day). The highest solar insolation is to be expected in Sahara region of Africa, South Africa, Australia and Caribbean part of South America. On the other hand, least amount of solar insolation is found in northern parts of Europe and Russia, North America, Greenland, and most southern tip of South America figure 3. Figure 3: Solar insolation zones in the World Figure 4-9 present solar AC pump hours of operation for all six zones respectively, for various pressures. Each of the lines is based on the solar PV installed capacity, so that a customer at a given zone of interest can choose the correct amount of solar PV panels solar PV capacity. Furthermore, each figure shows accumulative, daily flow for the given zone, for various heads and chosen solar PV capacity (right graph). Hence, the customer can not only choose the solar PV capacity based on the operating time per day for the given pump, but even more convenient, based on the total daily flow required at the given location. For example, if a customer has a site at zone 4, for a given head of 75psi (170 ft well depth), and required 5000 gallons of water (figure 6), the solar pumping system will require 2250W of solar PV capacity (9 standard 250W PV panels) and as a result will operate around 7 hours per day. 3
Figure 4: Operating hours and daily flow of solar powered submersible Goulds pump for Zone 6, for Figure 5: Operating hours and daily flow of solar powered submersible Goulds pump for Zone 5, for Figure 6: Operating hours and daily flow of solar powered submersible Goulds pump for Zone 4, for 4
Figure 7: Operating hours and daily flow of solar powered submersible Goulds pump for Zone 3, for Figure 8: Operating hours and daily flow of solar powered submersible Goulds pump for Zone 2, for Figure 9: Operating hours and daily flow of solar powered submersible Goulds pump for Zone 1, for 5
Figure 11: Daily pump operation of 1HP pump for different solar PV panel capacities Figure 11 above shows how increasing solar PV capacity affects duration of operation of solar pumping system. Time 1 is the duration of operation for 900W pump when powered by 1000W solar PV panels. If additional 250W panel is added, same 900W pump will be supplied with 1250W of solar PV power, and therefore duration of operation - Time 2 will be significantly higher, as shown in the figure. Increasing the solar PV capacity continues increase in duration of pump operation, but not linearly. Therefore, adding more solar PV capacity will provide diminishing returns after a certain point until it does not make economical sense anymore. Moreover, it is possible to extend the duration of operating hours of the same AC pump if a battery bank is added to the system, as shown on the figure 12 below, especially if nighttime operation is critical. The battery bank can be designed and sized for different AC load to extend the operation for a desired amount of time. For a given 1/4HP, 1/2HP or 1HP AC pumps, the table below shows battery bank sizes for different night time operation. Table 1: Battery bank configuration for 1/4HP, 1/2HP and 1HP AC pumps for different nighttime operation durations in addition to normal solar irradiance hours 3 hours 5 hours 8 hours ¼ HP AC pump 6 x 35Ah, 12V batteries 6 x 55Ah, 12V batteries 6 x 85Ah, 12V batteries ½ HP AC pump 6 x 55Ah, 12V batteries 6 x 85Ah, 12V batteries 6 x 115Ah, 12V batteries 1HP AC pump 8 x 75Ah, 12V batteries 8 x 85Ah, 12V batteries 8 x 115Ah, 12V batteries 6
Figure 12 below shows typical system installation for solar AC pump with battery back-up. Battery and solar PV got connected to the battery box, which is then connected to the PicoCell that runs the AC pump. The battery box leverages the embedded intelligence of the PicoCell and provides hardware protections for the batteries as well as the PicoCell. It can also be used to power an auxiliary cooling for the enclosure housing the batteries themselves. Figure 12: AC pump driven by PicoCell powered by solar and battery bank system 7