To automatically switch between mains electricity and photovoltaic (PV) power generation, you can use an electrical device known as an Automatic Transfer Switch (ATS) along with a charge controller and an inverter for the PV system.

1. Install the Automatic Transfer Switch (ATS): The ATS should be rated to handle the capacity of your PV system and be capable of managing the switching process smoothly.
2. Connect the PV System: Properly connect the PV system, including the solar panels, charge controller, and inverter, to the ATS. Ensure that the connections are secure and follow the electrical code and safety standards.
3. Connect to the Mains Electricity: Connect the mains electricity to the ATS. Make sure that the connections are done by a certified electrician and comply with all safety standards and regulations.
4. Set the Switching Parameters: Configure the ATS to automatically switch to the PV system when the mains electricity fails. Set the parameters to define the conditions under which the switch should occur, such as voltage thresholds or outage duration.
5. Test the System: After installation and configuration, thoroughly test the system to ensure that it functions as expected. Simulate both mains electricity failure and recovery to verify that the ATS operates reliably under different conditions.
6. Regular Maintenance: Perform regular maintenance checks to ensure that the ATS, PV system, and associated components are in good working condition. This includes cleaning, inspecting connections, and identifying any potential issues or faults.

Moreover, it’s essential to comply with all safety regulations and electrical codes during installation and operation. Consulting a professional electrician or an expert in renewable energy systems can provide valuable guidance and ensure that your setup meets the required standards and regulations.