For years and years, I've had an interest in green building technology. While the environmental aspect is cool and all, it's the science that really piques my interest. The idea of passive solar heating is interesting because it allows a home to be heated for free using nothing more than angles, positioning, and smart material choices.
Passive solar is based on the idea that the sun's rays enter through windows, warms the interior, then the heat is trapped inside. If you're familiar with solar ovens, it's the same concept. [Sidebar - parents, a solar oven is a fun project for the kids.] The angles come into play between seasons. The house will be designed to limit sunlight entering in the summer and maximize sunlight entering in the winter. It looks like this:
The 'thermal mass' in the picture represents anything that absorbs, stores, and slowly releases energy (heat.) This could be any material, but things like granite tile or an aquarium filled with water works well. The winter sun is angled below the roof overhang (because the sun is lower in the sky in the winter) during the coldest months, which allows the rays to enter the windows and heat up or 'charge' the thermal mass inside the house. When the sun sets, the thermal mass radiates heat into the interior of the house. During the day, the sun itself heats the house. At night, the 'charged' thermal mass heats the house. This process dramatically reduces the need for supplemental heating, thus saving a butt-load of cash. This, of course, is what allows you to comfortably walk around naked, even in the winter.
So How Do I Make This Happen?
Ideally, this concept will be designed into a new house. Here in the United States, the sunny side of the house will be the south side, which would include a lot of windows specifically designed to allow heat to enter but not exit. The roof overhangs would be long enough to block the summer sun in the middle of the day from entering the windows, but short enough to allow the winter sun to enter. Finally, the rooms that receive the light should have enough thermal mass to store enough energy to last throughout the night. A builder or architect versed in green technologies can design these features into any new construction project. Some good resources can be found here.
What if you already own a house, though? Can these ideas still be used?
YES! The principles do not require special equipment as long as you have at least a few south-facing windows. During the summer, window awnings can be used to keep the sunlight from directly entering the house. In the winter, the awnings can be used to allow the sunlight to enter.
Adding the proper windows will also help facilitate this process. The specific windows that will maximize passive solar heating is dependent on several factors, including the geographic area, the orientation of the house on the lot, and if the windows will be used to facilitate heating, cooling, or both. More information on windows can be found here.
Finally, the addition of thermal mass allows that solar energy to be stored during the day to be released after the sun sets. In my own houses and apartments, I've used a variety of objects as thermal mass. I've used a bar with a granite top, a wooden loft (which was a poor choice), a ceramic tile floor, and a giant aquarium for my pet piranha.
That's all it takes. Do these few simple tricks and you'll be well on your way to harnessing the power of the sun to help lower your energy bills. In the near future, I'll explore a few more elements of green building technology you can implement in your home. Stay tuned!