In April 2012 we took a trip to Mexico City. At a community fair in a local plaza, we came across a group of people who were promoting hydroponics. Their equipment was home made using simple materials like drain pipes, plastic shots glasses and j-cloth. Inspired by what we saw, we decided to make a demonstrator based on these materials, but with a twist. The pumps would be powered by solar power.
The demonstrator was aimed at proving the design and built for exhibition at a local community event. Just like we had seen in Mexico City, we used drain pipes, plastic shots glasses and j-cloths as wicks for the shots glasses. Power would be provided by a 40 watt, 12 volt solar panel, a pump was sourced from a caravan store. There are a range of 12 volts pumps available from auto and leisure vehicle suppliers.
First test showed that extra care is required when connecting the pipe work! Drain pipes are not designed to be water tight, so a second application of sealant was required on some of the joints.
Power management is provided by a commercial solar panel / battery control unit. At this stage the panel needs to be installed on the greenhouse, so for demonstration purposes the system was run from a pre-charged leisure battery.
Some final tweaks:
The size (capacity and power) of the pump proved to be critical. From 12v marine bilge pumps to automotive wind screen washer pumps, there is a wide range of choice. Our challenge will be to get the best balance between water circulation and energy consumption if we are to run a system powered only by a small area of 12 volt PV solar panels. We found that some of the pumps we tried had a more than adequate flow but consumed 30 watts of power.
The next stage will be to install the system with longer runs of drain pipe in our greenhouse. We’ll be posting what happens.