Intro: Solar Powered Water Pump With Speed Control Via Computer.
As part of my solar powered home, I have a potable water pump to provide water when our water utility is not available. I also implemented speed control of the pump to adjust the flow to allow energy efficient pump operation depending of the battery bank voltage.
Before we continue, take a read of my instructable detailing my solar battery bank.
Please Note that this instructable is what I have done for my application. It fulfills my needs and if your application is different then you must do your research and design. Everyone will have different ideas and that is good. If you feel strongly about your view then please post your instructable for the world to see.
Let's proceed to how I implemented my system.
Step 1: Using an Energy Efficient Pump for My Application.
I originally had a 120 volt AC pentax pump for several years. I worked great but for a solar setup it is not efficient and it's power demand is high (approximately 480watt). I needed a pump capable of running off dc and using far less power.
My choice is the jabsco par max 4 marine pump. It accepts 24volt and is compatible with my battery bank voltage. It's maximum power draw is 75 watts. Typically it uses 45 watts due to my speed control algorithm in my home automation pc.
My Home is single story and this pump gives me enough head and pressure to run all taps and shower really well. If your application needs higher head then you need to research for a suitable pump.
Step 2: Power to the Pump.
In terms of powering the pump via photovoltaic panels, know the watt hour energy requirements of your pump per 24 hour period. Assume 4 hours of usable sunlight and size your panels based on this. You can make different design assumptions to vary your cost should you wish. Also you will need a charge controller and battery bank (having a watt hour rating of at least your pump watt hour demand).
My charge controller is an outback flexmax 80amp mppt.
I used a 10amp single pole circuit breaker to power and protect my pump.
Keep in mind that the number of panels and batteries I have installed is not for my water pump alone. This solar setup is for the entire home and powers almost every load including one of my air conditioning units.
Step 3: Speed Controller for Flow Control and Soft Start/stop.
I used a pwm controller to adjust the speed of the pump motor. Dc motors respond very well to pwm as a means of speed control.
From Amazon I got a 15 amp pwm controller. Yes I know it's oversized for my application but I want long service life out of the controller.
The potentiometer gives 0 to 5 volt to directly control the pwm output. 0 volt being no rotation and 5 volt being almost full rotation!
I wanted soft start and soft stop to prevent a blast of water from an open tap and also to reduce startup wear on my pump/motor. In the sketch attached, I had included a resistor and capacitor between the control input of the pwm controller and the DAC output of my labjack u3. Anytime I request to pump to turn on, it gradually ramps up in a 8 second period to deliver full flow. Also when I request it to turn off its ramps down. Very very cool!
An important note here. Pwm controllers produce alot of electrical noise. I learned this the hard way when due to cross interference, my home automation system began to malfunction at times. Only through testing with my oscilloscope I traced the problem. Always keep the cable to the pump either shielded or at least 18inches away from electronic wiring.
Step 4: Computer Control of the Pump Speed.
Since the pwm controller output is directly proportional to the 0 to 5v output from the potentiometer, my labjack u3 has DAC outputs that can do exactly that!
I used FLOWSTONE to create the software for controlling this pump and the rest of the home. The speed control is used to reduce the speed of the pump during night. The more drained the battery bank is, the lower the speed. I used a base of 22volt as 0rmp and 25.6v as maximum rpm. Values in between are calculated and applied to the pwm controller.
In the screenshots of the GUI of the compiled software, you can see the section for the water pump. Immediately on the left is a 4 led bar graph to visually let me know the speed of the pump. During day time the bar graph is full, at night it will vary depending on the battery voltage.
Another reason I prefer computer supervision of the pump is that when I need the dog water bucket filled, the software module for dog food/water will request the pump to turn on then off for the time period I have programmed into that module.
Step 5: Enjoying My Green, Energy Efficient Water Pump!
My pump and home Controller has been in service since mid 2013. Thus far it has all performed admirably.
I hope this instructable has been informative and read my instructable detailing the rest of my solar powered home: