I want to connect a 140 Watt Solar panel to a 12 Volts pump. Panel output voltage in full sun is 17 Volts. Do I need a 12 Volts regulator to reduce panel voltage to 12? I prefer not to charge a battery and use the battery for driving the pump. Any solution.
You should notice the volts drop when you connect directly to the pump (i.e. with load). How big (watts) is the pump? If I was you I would just try it with and without water pumping. Measure the volts while hooked up. pumps should be able to handle a little overvoltage. Better to be over than under.
17V is the floating voltage without load. Connecting it to and inductive load will drop the voltage. Pump is a dirty load, so regulation may not be critical. However, keep in mind that sunlight level (as a source) is non-predicatable, so a margin for your solar capacity (or load reduction) should be heavily considered. This is essence of battery storage to keep the extra juice for application predictability.
Were I you, I'd put a rechargeable battery inline to smooth and regulate the voltage to the pump. Let the solar panel keep the battery topped up.
You never know when you'll need to run the water pump at night, and for that you need stored charge.
750 watts is 1 HP.....figure your draw based on the HP of the motor and check the output of your solar panel to get an idea of if and how long
the solar panel will power the pump.
You will certainly have to have something to buffer the panel from the motor - probably a dc-dc converter and a battery.
There were a number of interesting talks at the InterSolar conference in San Francisco on battery and super-cap buffering of solor panels. If you know anyone that kept their badge from the conference, the # on there lets you look at the proceedings on line at http://conference.intersolar.de/cgi-bin/x-mkp/visitors/vac.pl?language=1&eve_id=7.
There is a new white paper from Avnet on ElectronicProducts.com that is very interesting.
the solar panel may not be able to provide the inrush current for the pump.
I would use many millifarads across the panel, and an electronic switch that turns on the motor only when the solar voltage is > 16V open voltage.
the big capacitive buffer will provide the insruch current. at least 50mF and a 25A fet switch say a10 mohms Nfet on the negative line of the motor.
Some of the posts are confusing DC pumps with AC pumps. DC pumps are not damaged by operating them with lower than optional voltage. They just run slower. Over current/voltage may cause the pump to overheat however. The current is porportional to the applied voltage and load. If you just want to run it during the day such as for irrigation, A solar panel system matched to the load/pump works very well and does not need regulation.
General speaking there are some main points you must consider before using solar panel:
> Is this pump doing a critical pump? The question in another form, do you think if the pump didn’t work for a while it will be a disaster or it should not ever stop? Do you will use the pump at night?
In daily life applications, the solar panel is not considered a reliable source of power. The generated electric power by the solar panel is not stable; it depends on the brightness of sky, and the direction of sunrays.
To be able to decide if this solar panel is reasonable to your application or not, you must think about the supplied current. What is the maximum current this solar panel can
supply at certain voltage.
It would be preferable to power the pump by a fixed power source, if this option is not available think about long life batteries, you can use Lithium Thionyl batteries (write on google saft batteries). Final solution use chargeable batteries charged by a solar panel.
People who are intending to use solar panels for their applications; they must first check the weather forecast to be able to sit the expected highest, average and lowest generated powers.
In large systems which depend on solar panels; the solar panel must be cleaned several times a day to keep its maximum production. In dust storms the solar panel systems could be completely out of service.
You do not need batteries unless pumping is needed at night. Batteries are expensive, will not last long, and will reduce performance compared to the following alternative.
Use a PV pump controller such as
These controllers are basically a DC-DC converter that converts the essentially constant voltage (as the sunlight varies) output of your photovoltaic (PV) module to constant current at the rating of your pump. This means that as the sun comes up in the morning, the pump will start to run earlier in the day, but at a slower rate, than if the PV module was connected directly. As the sun increases the pump will run faster because the voltage on the pump will increase. The pump is also protected from transients with good controllers.
This is the proper way to operate a DC pump from a PV module. There are many such controllers on the market. If your pump is in a remote area or requires reliable operation, use the SunPumps controller.
Do not worry about dirt in most areas. I have seen very dirty PV modules still provide 75% of their clean output.