By: Josh King
How to power a controls device, no matter where, with the power of the sun.
Sometimes, powering remote devices can be a challenge. In the past, if you wanted to remotely power any I/O, it involved the additional expense and labor of burying cable. To bypass the cost and hassle of cable, we have developed and deployed systems powered by solar modules and batteries. As long as the application is outside, and receives at least a few days of sun every week, the solar module powers the devices with no problem.
Here’s how we do it.
How to power remote devices using a solar panel
The five factors to consider when designing a system like this are:
- Power consumption of devices
- Solar module
- Charge controller
Because this application involves a solar powered device, there are a few outside factors you’ll have to consider. The sun rises in the east, and sets in the west, so your solar panel needs to be set up facing south at a 45-degree angle for maximum sun. Otherwise the battery might not get the charge it requires to power your device.
In the location you’ve chosen, you’ll also need to search for any possible nearby shading sources, such as trees or a utility pole with an attached transformer box. Shading on the module will prevent the battery from charging because the solar module won’t be producing the power it should be.
2. Power consumption of devices
A lot of specifications will ride on the total power consumption of all your devices. I’ve thought of an example to use throughout this post that includes these three devices:
- Adam I/O Module
- Red Lion Data Station Plus
- Sierra Wireless RV50 cell modem
Find the data sheets for the devices you’re using, and locate the paragraph about power consumption.
Write down how many watts each device takes.
- Adam I/O Module (2.7W @24V DC)
- Red Lion Data Station Plus (24 W @24V DC)
- Sierra Wireless RV50 cell modem (1W @24V DC)
The next step is to add up the total power your devices require to determine total load of the application.
Our application has 27.7 W of total load. We’ll come back to this number later.
The battery is what stores the energy to power our system.
Because all our devices are 24V DC, our application requires a 24V battery. We’ve decided to use two 12V batteries connected in series instead, and then connect them to the charge controller input.
You shouldn’t just use any old battery for this application. Because the system will be outside in the elements, we recommend lead acid, gel, or absorbent glass mat (AGM) batteries. These battery types don’t require any maintenance and give you flexibility when mounting. Because there is no free acid in the battery, they can even be mounted upside down. In addition, these batteries can be deep cycled. This means if the sun is absent for many days (due to rain, clouds, or an extra-long eclipse) the battery should be able to handle those situations (depending on its amp hour rating, of course.)
4. Solar module
The solar module is what gathers power for our system.
You’ve got to look at the wattage rating on the back of the solar module and compare it to your total load.
The one in our example is rated for 20 watts. That means it’s not powerful enough to power our 27.7W load. We need to look for something a little more powerful.
It’s important to account for a little buffer room between the total load and the module’s max wattage. We’d probably specify a new module around 40W, as long as the voltage matches our charge controller voltage input range and the current (Imax) matches the controller input current range.
5. Charge controller
The charge controller is what ties our system together. The charge controller regulates the voltage and current coming out of the battery, to your devices.
Connected to the charge controller is the solar panel input, battery input, and total load. In our example, our charge controller is rated at 12/24V DC with a discharge current of 5 amps.
The charge controller will have a rated voltage input range, and a current input. The electrical parameters from your solar module will need to fit within those parameters.
In case of a large discharge or short, it’s a good idea to add a fuse between the load and charge controller.
Affinity Energy’s Solar String Analysis is a great example of a remote, solar-powered system. This is a mobile system we can set up anywhere, as long as we have sunlight, and it will power the devices inside the enclosure. In fact, we can leave it for weeks on end.
Inside the enclosure, you can see a charge controller and battery (they’re actually the same device, a Campbell Scientific data logger). And at the top, you can see the solar module.
The battery is a 12-volt battery, because the devices are 12 volts. The input comes through a fuse from the solar panel and goes straight into the charge controller. The output from the charge controller is 12 volts, and is rated for 15V to 40Vdc at 3.6Adc typical current.
Our solar panel is rated for 17.8 vdc at 2.8 amps, and fits just fine within our charge controller’s specifications.
I hope this has helped you understand how to power devices remotely using solar! If you have any more questions, contact us and we would love to help you out!
Joshua King is an Application Engineer at Affinity Energy with responsibility for installing hardware, integrating Modbus networks, setting up site local area networks, configuring remote access connections, programming data loggers and other I/O devices, coding alarming logic, and integrating full remote monitoring systems at industrial-scale solar farms.
After building and testing a colored dye solar cell in high school, and graduating with a B.S. in Electrical Engineering at Clemson University, Joshua knew he would pursue a career related to solar power. With a strong educational background in solar and renewable energy, Joshua joined Affinity Energy in 2015.
His contributions include major enhancements to the remote monitoring systems at 20MW Gates County Solar Farm, 3MW Tolson Solar Farm, and 5MW Rockwell Solar Farm. Joshua is a classically-trained violin player, but really enjoys playing the fiddle. He played in a bluegrass band called Slim Pickens for three years.