Solar pump - An exploration of off-grid solar

A few weeks back my wife and I bought a couple rain barrels which are working out really well. The problem we found was that unless we wanted to spend an hour watering the garden with a watering can, the water in the barrels was hard to use. The reason for this is because the only pressure you get is from gravity and the weight of the water sitting in the barrel. Don’t get us wrong, this gives you plenty of pressure if you want to fill water buckets, but it doesn’t give you enough pressure if you want to get the water down a hose. Our solution was a small DC pump. Why DC you may ask? Well, one of our reasons for getting the rain barrels was so that we didn’t have to run the main water pump just to water the garden, thus saving wear and tear on the pump and saving electricity. If we ended up getting an AC pump, it would have used electricity and probably more of it then our normal pump since it probably would not have been as efficient. Also, by having it be DC the pump is very portable.

Here are the major components to our solar pump:

- SHURflo On-Demand 12 volt DC pump
- Universal Battery – Sealed AGM
- 2 15 watt Northern Industrial solar panels
- 7 amp solar charge controller

We built the pump and battery into a box along with a simple on/off switch and
fuse. The pump came with standard hose hookups, but it was recommended to have at least one foot of high pressure pipe leading into and out of the pump, so we added that. We also added a simple filter on the input side of the pump so that any debris does not get into the pump. Because the pump is portable, we can set the pump box on top of the water barrels, hook up the hose and turn it on, and start watering with plenty of pressure.

Obviously since this is running off a battery, we needed a way to charge that battery, which is where the solar panels and charge controller come in. We simply mounted the panels on a wood frame made from a slightly modified pallet, hinging them on one side so they could be raised to angle to the sun. We wired these 12 volt panels in parallel so that we could increase the amperage output and decrease the charge time on our battery. The panels are then wired to the charge controller which then can be hooked to the battery to charge it up. When we hooked this up today, it only took about an hour in partial sun to get the battery fully recharged although we don’t think the battery was fully discharged since we hadn’t used it very much. The reason we built the solar panels and charge controller as a separate unit is so that it can be used with future batteries that we may get.

Overall, it was a pretty easy project that took about 3 days to get put together and working. This was a great project for us, because not only was it something we needed, but it also taught us a lot about off-grid solar. Then again, this is life according to Troy.