12V DC Water Pump and Solar

 One of the most visceral applications of solar power is when you watch a solar panel directly power an electric water pump. You can watch when the clouds come over and the flow lessens and then when the sunlight breaks again how it rushes the water with renewed vigor. As fun as it is to watch, let's talk about real world applications and how it might fit into your residential experience.

There are many reasons to pump water. Certainly in the more arid regions of the globe, it helps tremendously. But for the rest of us, it doesn't pay to sit there waiting on the sun to wash dishes or take a shower. Probably the most famous renewable energy application for pumping water is "pumped storage hydro". Again, this isn't on the residential level, but it can be scaled fairly easily.

Most likely, you may have a hydroponic system for growing indoor plants or perhaps an ornamental water fountain in your yard. But let's just take it from the perspective of water pressure and moving water from one elevation to another. 

New York City was famous for this issue as they would have water towers on top of the apartment buildings. This elevation of the water would allow the residents to have the water pressure they needed. In fact they still do use water pressure to move water from reservoirs into the city through underground tunnels.

Using a solar panel that produces ~40W (peak) of power at 12V, I can pump water for about 8-10 hours straight. With that much power I could move about 10 gallons of water every 30 minutes from 0 feet, to 10 feet of elevation. Let's say all that water is shower water. At the end of the day about 16 people could have water pressure for their shower they are going to take that night. And that is just running of 40 Watts of electricity. 

Now the next thing will be, "ok, having water pressure is great, but can it be warm/hot water". So then I have to get a 12V water heater and tell you how that works out and whether 40 Watts of solar panels is enough to provide enough water pressure and heat to take a comfortable shower at the end of the day.

100 Watt Solar Panel (Real Life Experience)

 So I've got a residence now with access to roof space for solar panels. I put my one, 100W solar panel up and ran the wires to my laptop to see how it did.

On a slightly overcast day, a 100W solar panel is not enough to power a ~60W laptop. If the sun was shining directly overhead of the panel, yes, a 100W solar panel would be enough. But this is real life.

Then I hooked up 40 more Watts of solar panel on my roof for a total of 140W of solar panels. That still didn't keep the laptop afloat.

Then however the sun came out, and it wasn't direct sunlight, but it was brighter than before. That was enough to keep the laptop going.

So, what is my real life review? A 100W solar panel is not enough to power a laptop on an overcast day. A 200W panel (or combined panels) would be sufficient. So if you're ever wondering how much solar panel to take with you so you can work on your laptop anywhere (during the day), it will be almost too much for one person to carry (rigid glass enclosed panels).