Designing a solar system that can power a laptop and a fan involves a few steps:

1. Determine the power requirements of the laptop and the fan: Firstly, you need to find out the power consumption of your laptop and the fan, which is usually measured in watts (W) or ampere-hours (Ah). This information can be found on the label on the back or bottom of the devices, or in the user manual.
2. Choose a solar panel: Next, you need to select a solar panel that can generate enough power to meet the requirements of the laptop and the fan. The solar panel’s wattage rating should be higher than the total power consumption of your devices to ensure adequate power generation.
3. Select a charge controller: A charge controller is necessary to regulate the power output of the solar panel and ensure that the battery is not overcharged or undercharged. Select a charge controller that can handle the output of your solar panel and the capacity of your battery.
4. Choose a battery: Select a battery with a capacity that can store enough power to meet the requirements of your laptop and the fan. Consider the battery’s voltage and amp-hour rating when selecting a battery, as well as its chemistry and size.
5. Choose an inverter: An inverter is necessary to convert the DC power generated by the solar panel and stored in the battery to AC power that can be used by your laptop and fan. Choose an inverter with a sufficient power rating to meet the requirements of your devices.
6. Install and test the system: Finally, you need to install the solar panel, charge controller, battery, and inverter, and test the system to ensure that it is working properly. Make sure to follow the installation instructions provided by the manufacturers and take necessary safety precautions.

By following these steps, you can design a solar system that can power your laptop and fan using renewable energy from the sun.