How to setup an UP board powered by the sun.
We are very excited about the launch of the new UP Board, now we have a very powerful Intel Atom x5 Quad Core x86-64 system in a credit card sized form factor. As the UP Board is Atom based, it is electrically power efficient, so we started to ask ourselves if it’s possible to power the board using it on an off-grid solar powered system. Powering the UP board using only a solar panel, without needing access to the electric network, is a very attractive project. It will allow us to use ubiworx™ enabled IoT systems in many new fields, like volcanology, environmental data capturing, remote weather stations, etc.
Basic design
Our off grid solar powered system consists of five parts that need to be properly calculated, allowing the system to work without interruptions 24/7.
- Solar panels
- Batteries
- Batteries charger controller
- Power supply (12V to 5V)
- Consumer system (UP Board and peripherals)
If we do not calculate the specifications of all parts before buying and integrating them, our system may not work properly and we may need to replace the miscalculated parts, losing money and time. So let’s start doing some basic calculations.
Calculating the needed power
Firstly, we need to know how much energy our system will need, so we should start measuring the power consumption of the entire system while it is in operation. A good way to do this is to connect the UP Board to a 5V laboratory power supply and take notes about the real consumption of the system with its peripherals.
When we have measured the electrical current (Amps) that our system consumes we can calculate the required power by multiplying it by 5V.
As an example, we will use the image values (located at the bottom), so our system is requiring about 0.5 A at 5 V, that means a power consumption of 2.5 W
We know that our system needs 2.5 W to work, but this is an instant power unit (Watts). We also need to know how much energy our system requires to work all day (Watts per hour per day). Calculating the Wh/day for our system is quite easy, you only need to multiply the system consumption by the number of hours that our system will be working, on any given day.
For this example, we will take it that we want to have it working all day, so applying the top formula, our system requires about 60 Wh/day.
Warning: Be careful configuring/selecting and wiring your power supply, a bad voltage/wiring may burn the board.
Sizing the power supply
As we now know the power requirements for our system, we can use this value directly for the power supply.
For this example, we will use a DC-DC 12V to 5V at 3A Buck power supply that gives us an efficiency of more than 90%.
This efficiency modifies the real system power requirements, because we are losing about 10% of energy into the power supply.
So, applying the formula, we obtain that the real power consumption goes to 2.7W or 64.8 Wh/day.
Selecting the battery charger controller
The charger controller is a very important part of the system, because it is the component that will store all the solar panels’ energy into the batteries, so the efficiency of this component will define the sizing of the solar panels.
PWM charger controller
It guarantees that the charging voltage is equal to the current battery voltage, while dropping down the solar panel voltage.
The main disadvantage with this device is that, if our solar panels give us the maximum power at 17 V, we will never be able to use it, because our battery will never go to that voltage (for a 12V battery we will go from 11.7V to 14.7V).
These kinds of controllers are good for use in warm places, where the temperature does not allow the solar panel to work at high voltage and where the sun light hours are generous.
MPPT charger controller
This device tries to use all power of solar panels in all situations, converting the solar panel voltage to the battery voltage, separating both sides and allowing the solar panels to work at the maximum voltage and current possible.
We should use this kind of device for cold places and where the sun light hours are very short. Using this controller in warm places will not mean a lot of improvement against a PWM controller, because the solar panel voltage decreases when it’s hot and the voltage difference between the panel and the battery will be very small.
As we are in Northern Europe, a cold place with limited hours of sunlight, we will use an MPPT charger controller for our system; you should realise what is appropriate for your situation.
Calculating the battery capacity
The batteries are meant to power the system while the solar panels are not generating enough energy. Therefore, we need to think about the maximum number of days that we expect to be without enough solar energy.
For calculating the battery size, we can use the following formula:
Where C is the battery capacity, E is the Wh/day needed, t is the autonomy time we want (in days) and V is the nominal batteries voltage.
The constant 0.85 is our taken batteries charging efficiency and 0.6 means that we do not want to discharge our batteries behind 60%, in order to guarantee a longer battery life.
For our example we want autonomy of 3 days using 12V batteries, so applying the formula we get that we will need a capacity of about 32Ah.
Sizing the solar panels
The last thing we need to calculate is the solar panels size. It will depend on the geographic position, that will condition the number of hours of sunlight, our system power requirements, what we already have, and the efficiency of the charger controller.
As we are going to use a MPPT charger controller, we can take an efficiency of about 90%, if we were using a PWM charger controller it would be about 60%. So we will use the following formula for estimating the solar panel size.
So, as we are in Northern Europe and only have about 2 hours of sun per day, we apply the formula and get that we will need a solar panel of about 36 W for powering our system.
Enclosure
As it is an off grid system, a proper enclosure is very important. We suggest using a weatherproof (IP67), large enough to hold all components with space for air to circulate for some cooling as well.
If we are going to add any kind of wireless communication system, we should avoid metallic enclosures, because it may act as a Faraday cage, limiting or avoiding radio signals transmission/reception.
In order to avoid water and bugs going inside the enclosure, we should try to make as few holes as possible, preferably at the bottom of the box, and seal them properly. If the box is big enough, we do not need to worry about ventilation holes, at least for the UP Board refrigeration anyway.
To improve refrigeration, is a good idea to locate the enclosure on a shadowed zone, in order to avoid direct sun rays. For example, if we are going to use a pole, a good location would be behind the solar panel.
Improving UP Board consumption
As you can see at the beginning, the UP Board may require a lot of energy to work, taking into account that it needs 2.5W in an idle state. But don’t panic, there are many ways to improve it and get it to acceptable values.
We should not forget that we are in front of a very powerful board with a lot of sub-systems, which we will not need for our project. It would be great to be able to disable the unneeded parts, don't you think? Well, that's possible.
In the BIOS Engineering menu, we can find these useful functions that allow you to Enable/Disable some parts in order to enhance power consumption.
- CRB Advanced / CPU Configuration
◦ Power technology: It allows you to switch between “Disable”, “Energy Efficient” and “Custom”. If you keep at “Custom” you will be able to set up these options:
▪ Turbo: It allows you to disable “Turbo”, limiting peak consumption.
▪ Package C state limit: It allows you to change how deep the CPU can sleep.
- CRB Chipset / North bridge
◦ Intel IGD Configuration: Disabling the “GOP Driver” and “Integrated graphics D” allows you to disable the graphic card; this can be an important improvement.
- CRB Chipset / South bridge
◦ USB configuration
▪ XHCI controller: It allows you to disable USB 3, recommended if you are not going to use it.
▪ HSIC Port 2: It allows you to disable USB 2, you probably don't want to disable this.
◦ LPSS & SCC Configuration: This menu allows you to disable many of the sub-systems.
▪ SCC eMMC Support: Disabling eMMC may not be useful unless, for example, you are booting from USB (Live).
▪ SCC SDIO Support
▪ LPSS I2C #- Support
▪ LPSS HSUART #- Support
▪ LPSS PWM Support
▪ LPSS SPI Support
◦ PCI Express Configuration
▪ PCI Express Port 1: Disabling this option, will disable the LAN port. If you are not using it, don't hesitate in disabling it.
Calculating Power Consumption
The power measured in the image is only valid as an example. The measurement shown is for the board in an idle state.
Sun Levels per Country
This image tells us that we get roughly 2 to 3 hours of sun per day.
Enclosure
This is what the recommended enclosure looks like.
For more details, take a look at the attached BIOS screenshots and visit UP Board Community.
Note: BIOS engineering menus need a password (that can be obtained from AAEON).
Warning: Randomly touching BIOS engineering settings can finish with a non-booting board. If this occurs, unplug the power supply and the battery for 5 minutes and then plug them in again to reset BIOS settings.