This solar system is designed to interface with a hydronic boiler. The hydronic boiler (Electric or Gas) will act as backup when the solar energy is insufficent to heat domestic water or the heating loop. There are also two tanks - one tank has a double heat exchanger, which take the heat from the solar panels and from the boiler when the tank temperature falls below a certain set point. The Buffer tank is used to store excess solar energy for later use.
Please note: that when using solar for domestic water only - you can achive close to 100% of your domestic needs with the proper amount of panels (Generally 40 to 60 Solar Evacuated Tubes) and storage. However, you will always need a back up for when there is insufficient solar energy. You can use many different heat sources - such as electric storage tank, gas storage tank, tankless water heater or boiler like we've shown below. However, when using solar for space heating - you will proably want to use an efficent gas or electric boiler. Why? Well - solar for space heating may give you up to 30% of your heat so you will have to heat the other 70% with something else. Also, you will generally have at least 120 to 180 Tubes Evacuated Tubes or more for solar heating systems.
All systems are different - so contact one of solar specialist for a detailed system design for you residential or commercial location.
This is only an example. Actual layouts vary from job to job.