What devices can run directly from Solar Panels?

[john95]

Hello,

Is there a way that we can run some devices without using a Solar Charge Controller, Batteries and Inverter?
For instances a 12v vacuum, a 12v drill, car radio/CD player, a 12v Fan, a 12v TV, etc. Devices that are used only for a few minutes.

[SunEagle]

There are some loads that can work directly wired to solar panels. DC fans and pumps are probably the most common but you have to make sure the voltage and amp output of the panels is matched to the load.

The problem with other DC loads like a drill, vacuum or TV is that they can draw more power then the panels can provide and also require a constant voltage to work. Pumps and fans can be built to run at different speeds which is what you will get depending on how much sun is hitting the panels.

[john95]

Let's say that I want to run a 16" 12v 80watts 12.70 Amps draw directly from a solar panel:
Which panel will be more suitable for this load, a 12v 100watts panel or a 12v 160watts panel?

The 160watts panels is 13.3 Amps and the 100watts panel puts only 8.33 Amps.
Is this the way how you can tell a panel produces its Amps? Or what else dictates the amount of Amps of a panel? Thanks.

[sensij]

Is this the way how you can tell a panel produces its Amps? Or what else dictates the amount of Amps of a panel? Thanks.

The amount of direct sunlight on the panel determines the maximum current it can put out.

You need to look at the IV curve for your solar panel and make sure that your load will be ok at any point on it. If the panel is capable of producing more current than your load needs, what will happen? A fan or pump will usually just spin faster.

[SunEagle]

Let's say that I want to run a 16" 12v 80watts 12.70 Amps draw directly from a solar panel:
Which panel will be more suitable for this load, a 12v 100watts panel or a 12v 160watts panel?

The 160watts panels is 13.3 Amps and the 100watts panel puts only 8.33 Amps.
Is this the way how you can tell a panel produces its Amps? Or what else dictates the amount of Amps of a panel? Thanks.

The panel wattage is calculated by multiplying the Vmp x Imp = watts. The problem with connecting a DC load that is much bigger than the panel wattage along with not being able to handle variations in voltage and amps that the panel puts out makes it hard to keep it running. That is why you really need a battery in between the panels and load.

So even with that 160watt panel I seriously doubt you will be able to run that 80watt 16" (I assume TV).

[john95]

Sorry I meant a 16" Fan, not a TV.

[john95]

The panel wattage is calculated by multiplying the Vmp x Imp = watts. The problem with connecting a DC load that is much bigger than the panel wattage along with not being able to handle variations in voltage and amps that the panel puts out makes it hard to keep it running. That is why you really need a battery in between the panels and load.

So even with that 160watt panel I seriously doubt you will be able to run that 80watt 16" (I assume TV).

What about using a big capacitor or many capacitors that would work as a "buffer" to save the necessary amount of electricity for the device to work. If this can be done like in a car with a power hungry amplifier, we don't need batteries, charge controllers, inverters or any other middle man between the solar panels and the device.

[john95]

The amount of direct sunlight on the panel determines the maximum current it can put out.

You need to look at the IV curve for your solar panel and make sure that your load will be ok at any point on it. If the panel is capable of producing more current than your load needs, what will happen? A fan or pump will usually just spin faster.

I got you. So, even if the panel is rated to produce 320 watts 24 v, if the sun is not shining enough light, then it may be producing half of what is rated. In this case assuming that is producing only half, then it will be producing 160/24= 6.6 Amps. Which is not enough to run the Fan that draws 12.70 Amps.

[Sunking]

John it can be done, but it is not easy or straight forward as you may think.

If you look at say the largest 12 volt battery I know to be 190 watts which has an Imp of roughly 10 amps only produces maybe 9 amps, at solar noon with the panel facing directly into the sun, and that is just for a few minutes around noon, and the voltage if matched with the device will be 18 volts, not 12. So if your motor is rated 12 volts at 5 amps would likely burn the motor up. If you used say a 72-cell 24 volt panel will definitely burn the motor up.

You really need what is called a Current Booster which is a lot like a MPPT Charge Controller with an over sized panel. Say your motor is rates 12 volts @ 5 amps or 60 watts is to use a 200 to 300 watt panel. But there is still limitations, like will only work 3 hours before noon to 3 hours afternoon. The other 18 hour hours the day you are SOL.

They also make motors, or I should say pumps that will work longer but power aka speed depend son time of day. Morning and afternoons slow, fast around noon hours. That is fine for say a water well pump filling a cistern. In that case a wind mill works better.

[john95]

Thanks for your explanation. So what components would you suggest me to run this fan that is 16" 12 volts @12.70 Amps?
I want to install it on the attic or a window.

[SWFLA]

I have a solar turntable that rotates a small plant.

[SunEagle]

Thanks for your explanation. So what components would you suggest me to run this fan that is 16" 12 volts @12.70 Amps?
I want to install it on the attic or a window.

To get the fan to run at full speed you will need more than 12.7amps from the source. But if speed does not matter you can use that solar panel that generates at least 10 amps and you should get some amount of movement out of it but the more amps you can send it the more CFM it will produce. Just be careful the motor can handle low voltage because if it goes too low you then get what is called a "brown out" due to low voltage which can damage some DC motors.

I had a couple of attic fans that ran off a 10 watt panel. I do not remember what the DC motor amp rating was but it did move a lot of air considering it only get 10watts of solar to power it. I am sure the motor was designed to run at different speeds based on the amount of sunlight hitting the panel.

Oh. As for a capacitor. That works keeps the voltage up for a brief time but I would not expect it to work unless you can recharge it quickly.

[AzRoute66]

When quail hunting down here I often run into pump installations (as described by Sunking) with the wire from the panels directly to the pump with nothing in-between. Pumped water slowly runs into a large (16' diameter x 5' deep) storage tank. The storage tank fills slowly enough that the rancher must just disconnect them when they approach full as there isn't even a simple float switch to shut them off.