Our home is continually evolving in it’s energy efficiency, not by itself though. Thankfully for it, I’m always looking for ways to reduce our dependence on natural gas and electricity by making as much use of the sun’s energy as practical. So far I’ve installed a solar hot air system in the master bedroom and a solar hydronic system in the living room. Together these systems have cut our energy consumption by at least 50% overall, but the lessons learned are important. As a result I’m even more motivated to install a completely passive system than ever.
This year Albuquerque has experienced some large temperature swings. Since December I’ve had to go on the roof to cover one of our home’s solar-hydronic panels on several occasions because it was too warm. These panels heat water that in turn heats our living room floor. My problem is that when it gets unusually warm the system brings in too much heat indoors, and makes the room too warm. Also I get concerned that some of the synthetic tubing leading from the panels on the roof and under the tile floor could be damaged, even though it’s rated to handle very hot water.
Solar-hydronic systems are similar to nuclear reactors. They both use a nuclear reaction to produce energy, which in turn heats water. In both cases it’s possible for the coolant to overheat and cause damage to pumps and other components. In my own design, I have not yet found an easy way to moderate the Sun’s output, so I’m left with needing to climb on the roof to put a shield between the Sun and my panels.
As we breach 400 parts per million (ppm) atmospheric CO2 in 2015 and continue higher, I wonder if this will be a more frequent occurrence. Everyone has their climate opinion on this, but CO2 is CO2 at 400 ppm, and CO2 doesn’t care. If climate science has any merit, I suspect I’ll need to build some sort of a louver or sliding screen that can be operated automatically when the weather gets to be too warm. My goal of a simple system with few moving parts may be unrealistic.
Speaking of simple systems, I’m liking more and more the solar hot air system in the master bedroom. This system uses hot air instead of water to transfer heat, and I can turn it off with the flick of a switch. A 40 watt PV panel provides electricity to a 12 volt brushless motor that moves around 150 cubic-feet of air per minute (CFM). There’s no sensors, or control systems, just a solar cell connected to an electric motor and a switch to turn it off in the summer. When the sun goes down, the fan stops. No need to worry about clearing snow of the PV panel to get the pump working as I do on my hydronic system.
I don’t recall when I built this but it was probably around 2007, so if I were to try and figure out how much energy we’ve saved with this system, I’m sure it would be impressive. The air blowing into our master bedroom and master bath is warm enough to make that part of the house comfortable by 10:00 am most days. The only downside, is that it quickly gets cold when the sun goes down.
This is actually what I like most about heating the floors using hot water. The floor in the living room staying warm hours after the sun goes down is worth it, but I wonder where the trade-off is. The moral of the story is simplicity probably beats complexity in the long-run. So, instead of expanding the existing systems as I had planned, my next project will be building a totally passive system called a Trombe Wall instead. Being a techie I may miss the technology, but after all I can always use technology to measure our energy savings and home’s reduced carbon footprint.