Solar Solar powered hot tub

[bernhard]

G'day,

In order to lower my electricity bill, I want to use the power of the sun to heat my hot tub. The setup is the following:

A 100W solar panel is driving a raspberry pico microcontroller which is measuring the temperature of the water in the hot tub. If the water is below 40C=105F it will start a 70W pump. Water will be pumped through a hot water collector and outputting warm water into the hot tub. The microcontroller will stop as soon as the target temperature is reached. I want to connect this directly, meaning I do not need a battery because if there is no sun, there is no need for pumping water anyway.

My setup is the following:

Solar Panel 100W 18V connected to a 8-40V/12V 10A DC-DC Converter. Now I get out nice 12V. Those are connected to a 12V/5V DC-DC Converter for the microcontroller. The pump is connected via a 10A relay of the microcontroller to the 12V. I am not going to go into detail for the microcontroller and all the sensors, display etc.

What do you think about this setup? Am I missing something? Is there something I could do smarter? I also thought about a charge controller which has also a load output and comes with a USB plug. That would be much easier for the microcontroller.

Looking forward for your thoughts,
Bernhard

 

[James]

I would do away with the microcontroller
when the sun shines, the pump will run
i doubt you will ever have a problem with overheating the tub but if it is an issue, just put a thermostat on the pipe that draws water from the tub.

kis (keep It Simple)

 

[bernhard]

I would do away with the microcontroller
when the sun shines, the pump will run
i doubt you will ever have a problem with overheating the tub but if it is an issue, just put a thermostat on the pipe that draws water from the tub.

kis (keep It Simple)

Fantastic idea! I just had a look at thermostats and it is basically exactly what I need. Thanks, I will skip the microcontroller and get a thermostat right away. I hope to find a thermostat which will keep the settings when disconnected from power. So I can keep the setup without battery. kis, they say.