Project: Change the loading pump of the hot water solar system to PV electricity. Insel operation 12V
, From Yue Wu, 2 min reading time
My goal was to completely convert the charging pump of the solar hot water system to solar power. Obviously, if hot water is generated by the solar system, enough power must also be generated for a circulation pump.
For testing purposes, I connected three 90W PV modules to an MPPT controller and stored the generated energy in a Power Queen 12.8V LiFePO4 100Ah battery. A 600W inverter then supplies the charging pump with approximately 100W of power (230V AC).
However, when the system is idle, no unnecessary power should be drawn from the battery. Therefore, the inverter, which is switched on by my freely programmable heating control system, is controlled via two additional relays. First, the inverter is connected to the battery, and then the second relay (with a delayed response) switches the inverter on.
If the battery is empty despite everything, the pump will continue to be operated with mains power via an additional relay control.
As an additional task, I modified my heating distribution board so that in the event of a power outage, the inverter also switches on automatically, allowing the heating controller to continue working. A small UPS system supplies power to the heating controller and other connected devices between switchovers from the mains and emergency power.
Because when switching between the two voltages (mains and emergency power supply from the inverter) you have to pause for a few seconds so that the two voltages do not come together.
Another task can then logically be added. I had to classify my system into important and unimportant consumers. In the event of a power outage, only the solar charging pump and the associated diverter valve (switching between charging the boiler and buffer storage) should remain in operation to avoid unnecessary strain on the battery. The other pumps used to heat the conservatory don't need to operate in the event of a power outage. After After some mental work and a good circuit diagram, I was finally able to complete this satisfactorily. A power distribution board supplies the important and unimportant devices with power.
It would also be possible, should the inverter of the 12V system fail, to immediately switch to a second system. But only manually. I also have a 24V PV system with a 25.6V LiFePO4 battery from Power Queen. This, of course, also supplies other devices and pumps with solar power.
So I can already say that I'll be able to survive without grid power for some time. Of course, the PV system will be expanded, and a second (super) battery from Power Queen will also be purchased.
(c) 2022 VoWa Jan.023
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