Short Days and Warm Showers

If you’ve been following my blog, you know I use solar to heat the water I use in my home for washing and bathing. It takes about 3 hours of good sun each day to keep up with all of my hot water needs. When we get a few clear days, the water storage gets hot enough that I can go a couple days with heavy overcast conditions.

This time of year, the sun is only effective for heating from about 09:00 AM until about 3:00PM. That’s not a big window, if the day is partly or mostly cloudy. Furthermore, we seem to get a couple of sunny days, followed by 3 or 4 cloudy days. I gave in and turned on my electric water heater for one day in late December. Otherwise, there are days when I have to take a warm shower, instead of a steamy hot one.

For me, this has sort of become a crusade; to try to get by on what the sun provides. It’s not much of a sacrifice. Most of the year, I have more hot water than I can use. However, these short days, combined with overcast conditions, really do test my resolve. Occasionally, in the summer, we get a week of rainy dark weather and I run out of hot water, but it hardly matters, because I take some of my showers outside in the summer, anyway. Hot showers just aren’t as important to me when it’s 90 degrees Fahrenheit (32C).

I just purchased another photovoltaic panel and a new charge controller so I can add about 300 watts of capacity to my solar electric system. It also suffers a bit when the days are short and overcast. I have batteries to get me through the dark times, but they need time to recharge at least twice a week. I hate to add more batteries, because they have a relatively short lifespan (see my other blog entries on battery woes). I don’t need more photovoltaic capacity in the summer, but I definitely need it in winter. I’ll figure out some way to use the excess power in the summer. I’ve been working up some ideas for a while. One of those ideas is to power the refrigerator off the solar during the day, and let it switch back to the grid at night. That would let me use more energy while the panels are generating it, and not put an additional load on my batteries.

I took the Polar Bear Plunge on January 1st. It’s the 2nd time I’ve done it in North Carolina. It was a good time. The water was 49 degrees Fahrenheit (10C) and the air was about the same. The sun was shining and it wasn’t windy, so it was really a nice day, considering it was January 1st.

Too much hot water!

I’ve had my solar water heating system in operation since May 2011. It works really well. In over a year, I’ve turned my electric water heater on for part of 2 days. Once, we had experienced about 7 heavily overcast days in a row, so I was just running out of hot water. The second time, I had to drain and recharge the collector loop because I didn’t have enough antifreeze in the solution. That means that my electric water heater has been powered up for less than 24 hours in over 400 days. The solar water heater is providing 99.75% of my hot water. I even do some of my laundry in hot water and rinse my dishes in hot water because the heat is free.

solar water heater panel partially covered with a sheetWell, now that summer is upon us, again, I can’t use enough hot water to stay ahead of the sun. The primary tank will reach 185F in a day of full sun. The water is so hot, even with R30 insulation on the tank, it’s heating my utility room.

I can set the pump controller to stop circulating the collector loop once the storage tank reaches the desired temperature, but then the collector gets really hot. It reaches temperatures of 300F, and I am pretty sure that’s not a good thing. So, yesterday I enlisted a friend to help me put a sheet over about two thirds of the panel, to deflect some of the sun’s heat. We had a day of full sun, today, and the sheet worked well at moderating the amount of heat. It’s a good temporary solution, but I’m going to have to work on something more permanent and easy to control. It would be really nice to have an automatic louver system, but I’m not that ambitious, and I’m pretty sure that would cut down on the effectiveness of the panel when I actually need it to work at 100% capacity.


solar panels on custom tower

The Solar Tower

This is my first blog post, so let me get started by introducing my tower. I built this tower from square, steel tubing, anchored in steel reinforced concrete. I installed my solar water heating panel and my photovoltaics on the top of the tower, which is oriented to face due south.

The green box holds batteries, a charge controller, and some other electronics for monitoring and controlling the power generation part of the system. There is also a pressure tank for the rain water pumping system in that box.

Mounted below the green box is a 275 gallon water tank that holds rain water that is funneled into it from the gutters on the house. There is a 12 volt, solar powered pump and some plumbing that connect to a couple of spigots where I can connect garden hoses and an outdoor shower for rinsing off after a hard day, working in the sun.

My photovoltaics charge batteries that power some 12 volt equipment in my house and an inverter that provides 110V AC for powering tools, my electric lawn mower, and other things. The batteries also power my water pump, as previously mentioned.

I’ve always got several projects in the works, and I hope to use this blog to document my progress on those projects.