Solar energy as part of the renewable energy sources is a good alternative to fossil fuels. The sun's energy reaches a daily average intensity of around 165 W/m² on the earth's surface. This can be used directly with photovoltaic systems. In Germany, the annual radiation output (GHI = Global Horizontal Irradiation) is about 1,056kWh/m² and in my adopted country of Thailand it is around 1,800kWh/m² per year. This data can be found in GLOBAL SOLAR ATLAS.

In addition to the fact that there is enough solar energy here in Thailand for use, the reliability of the local power supply (grid) leaves a lot to be desired. The electricity is often cut off for a few hours in heavy rain or when repair work is being carried out. Stupid because our water pump also needs electricity. The greatest possible independence from the grid would be a clear gain in convenience. There is (so far) no reimbursement system like in Germany here in Thailand. The roofing of the carport was the third argument. After all, it rains heavily here or in the blazing sun the (black) car roof reaches a temperature of over 80°C.

What are the key points for the new solar system:

• the PV panels should span the carport as best as possible and be rainwater-proof
• A battery unit is required to bridge the night and cover power supply in the event of grid failures
• the inverter can be off-grid (without feedback) and should automatically switch between the energy sources (solar, battery, grid) as needed.
• the solution should support DIY, to be able to be integrated in Home Assistant and remain affordable.

An important parameter is the required power that the new solar system should provide. To estimate one should roughly know the consumption values of your own household. In PowerMeter I have already described how to record the power consumption. Here is an example of the daily consumption in our house:

In addition to the air conditioning, the main consumers are of course thecirculation pump of the pool. The total consumption of this sample day was 18.8kWh. Typically, our daily consumption is between 15kWh and 25kWh. Almost half (45%) of this amount is at night (6:00 a.m. to 6:00 p.m.). The current maximum power requirement is around 5kW. In the worst case, however, this can go up to over 10kW if all 4 air conditioning systems, the pool and dwell pump, washing machine, water heater, etc. are in operation at the same time. However, 14.5kW is the maximum anyway, since the house is only connected to the grid with single phase and maximum of 63A.

For electrical autonomy, the planned PV system should therefore be able to deliver around 25kWh and the battery at least 11.25kWh.