Two nights ago I had one of those Archimedes moments regarding our DIY swimming pool heater. To recap. I’ve previously mounted two second hand solar water heater panels and a photovoltaic panel on the workshop roof.
The water heater panels are connected to the pool pump with the input immediately after the filter and the output to the return pipe after the chlorinator. Because heat rises the input pipe connects to the bottom of the panels and the output to the top. The strength of the pool pump isn’t sufficient to circulate the water through the panels. Instead the solar panel provides the power to a 12V water pump connected into the input pipe.
The solar panel produces approximately 27V, which is too high for the pump. To rectify this the panel is connected to a small and cheap solar controller. The controller has six terminals. Panel input (+ & –) Battery (+ & –) Load (+ & –). The output from the panel goes to the controller Input and the pump is connected to the Load terminals. But the pump isn’t directly connected to the Controller Load terminals. That would result in the pump running continuously whenever the panel received sunlight. This wouldn’t allow enough time for the solar water panels to heat the water. To solve this, the Load terminals are connected to a digital timer and the timer controls a 12V relay. The latter is required because the digital switch is not sufficiently powerful to accept the required power to run the pump.
The 12V water pump is in the grey box and the controller, timer and relay in the box with the window
The solar controller is the orange box at the top of the window. The timer is displaying 24 minutes until the next pump activation and the red arrow to the relay.
Through trial and error I have identified if the pump runs for a minute every half hour the water in the panels gets hot.
However the system wouldn’t work. I’ve since discovered the solar controller requires a 12V battery to be connected before it will send power to the Load terminals.
My ‘Eureka’ moment was when I realised I might be able to trick the controller into thinking a 12V battery was attached by making one from three of my old lithium cells I recovered from a tool battery I found at the rubbish tip.
I made a temporary system to check my theory. AND it’s currently working! I won’t make the system permanent until I’m satisfied it’s a long term solution.
No comments :
Post a Comment