The drip irrigation finally arrived after being shipped to us from Brown! We set up the system at the Student Experimental Farm! We tested our pump one last time with solar panel and then attached it the brown system. All testing went well!
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We collaborated with students from Pete's "Energy, Society and the Environment" course to test the pump we just ordered. We wanted to understand the voltage our pump required and did multiple tests to understand it. We ran a total of ten timed pumping test under various sunlight conditions to determine what power the solar panel were able to produce and how the pump performed under these various conditions. We had the pump hooked up directly to the solar panel and we measured the voltage drop across the pump, the amperage through the pump, the flow rate of water and the pressure produced by the pump. Our direct pump system efficiency averaged 17% at the various sunlight conditions. We met this week to work with and understand the solar panel systems provided to us by the BRAE department on campus. We tested volt readings and amp readings. Our goal with prototyping is to discover if it is possible to run a pump using direct photovoltaic power (no controller) under variable load conditions. We decided to meet at another time earlier in the day to do further testing.
Our procedure for this next step is as follows: 1. Wait for a sunny day. 2. Hook PV panels in parallel to the operating amperage of the pump (if necessary). 3. Hook up electrical system to a data acquisition system to measure voltage (V) and amperage (A) in the circuit. 4. Run the pump with suction and return to the same bucket and minimal loading conditions. 5. If pump runs smoothly, add hydraulic resistance by throttling down the return valve. The graphic below (on the right) shows how we will do this testing. Using the design from the Brown Team for the drippers, we laser cut acrylic models and tested the flow of water through clear 3/16” vinyl tubing. We found that acrylic wasn’t the best material for the drippers and broke easily when the tubing was pushed through the opening. With an appropriate model size, with the opening tapering from 0.06” to 0.08”, we were able to test the flow of water. Unfortunately, while we did have a flow, the rate did not vary widely as the opening narrowed. What we learned: The flow rate depends on the water pressure, and pressure at which the water is entering the tubing. This rate will depend on the height of the storage tank, which affects how fast the water will come down. Although cheap, acrylic is not the best building material for the drippers. (An interactive version of the design for the Brown dripper can be found here.)
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