Project: Convert the charging pump of the hot water solar system to PV electricity. Island operation 12V
, by Yue Wu, 2 min reading time
My goal was to completely convert the charging pump of the hot water solar system to solar power. Since it is clear that if we generate warm water via the solar system, it must also be possible to generate enough electricity for a circulation pump.
To test, I connected 3 90W PV modules to an MPPT controller and stored the energy gained in a Power Queen 12.8V LiFeP04 100Ah battery. The charging pump is then supplied with energy (230V AC) via a 600W inverter with an output of approx. 100W.
However, no unnecessary electricity should be drawn from the battery when the system is at a standstill. Therefore, the inverter, which is switched on by my freely programmable heating control, is controlled via two additional relays. First the inverter is connected to the battery and then the inverter is switched on with the second relay (delayed on pick-up).
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 converted my heating distributor so that in the event of a power failure, the inverter is also switched on automatically, and so the heating controller can continue to do its job. A small UPS system supplies the heating controller and other connected devices with power between switching from the mains and emergency power.
Because you have to pause for a few seconds when switching between the two voltages (mains and emergency power supply from the inverter) so that the two voltages don't 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 failure, only the solar charging pump and the associated switch valve (switching between charging the boiler and buffer storage) should remain in operation in order not to put unnecessary strain on the battery. The other pumps that are used to heat the winter garden do not have to work in the event of a power failure. After some mental work and a good circuit diagram, I was able to do this satisfactorily. The important and unimportant devices are supplied with voltage via a plug-in distributor.
It would also be possible, if the inverter of the 12V system is defective, to immediately switch to a second system. But only via manual operation. Because I still have a 24V PV system with a 25.6V LiFeP04 battery from the Power Queen. Which of course also supplies other devices and pumps with solar power.
So I can already say that I will be able to make ends meet without mains 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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