Actively Passive

It may come as a surprise to some now days, but there was a time when “solar” did not mean electricity. In fact it wasn’t too long ago that if you were talking about solar electricity you had to spell it out for people, explain the technology. Back in the old day is only about 10 years ago.

Solar electricity, aka photo-voltaic power has been around since the 1950s. It powered satellites, watches and calculators, but was considered too expensive for mere mortals to use except in very small quantities. Up until a few years ago, that’s the way it stood. At some point the price came down far enough and the lure of eco consciousness strong enough to make Photo Voltaic electricity a viable business concept. It didn’t hurt for countries like Germany to mandate Renewable energy quotas either.

In the bad old days of the first (mid 1970s) oil crisis, when the price of oil increased 3x, solar electricity was not considered an option. To begin with, oil was the problem and oil was not used that much in making electricity. Coal was (and still is) the main source of electricity. However, oil was used for heating purposes (and still is) in the eastern half of the country. Where electricity was an issue, wind power was looked at as a solution and a lot of now defunct companies sprang up only to die shortly after. For heating homes, a now oddly defunct concept, solar heating, came to the fore. Solar heating came in two flavors, active and passive.

Active meant that panels were installed which heated air or water/antifreeze up in the sun. The air or water was then pumped into some kind of storage tank where the heat it contained was siphoned off as needed into the living/working space. It was called active because it required some kind of pumping mechanism or fan to operate.

In a passive system, there was no additional energy expended to move the heat around. It either happened by “thermo-siphoning” or just sat there, absorbing and expelling heat into into and from a “thermal mass”.

There were many “solar houses” built and many active solar heating systems added to existing homes. Many still sit on roofs on homes across the country, although how many still function is anyone’s guess. I personally have purchased old solar heating panels from people who have just wanted to get rid of the things. They are a good source of Aluminum, Copper and safety glass. Sometimes they are still functional if you are so inclined to install this type of system. Unfortunately, many of the old panels were designed improperly. Oh, they will heat water if you pump it through, but they won’t drain back due to the way they are constructed, requiring using a strong antifreeze instead of just water. This results in added expense and complicates the design, installation and functional aspects of the system. In all systems, simplicity is important to success.

While there are elements of passive solar design that may be added to an existing home, passive solar works best when the building is designed and built using passive solar principles from the beginning. These are a few of the basic principles that define passive solar architecture.

  1. Utilization of windows to admit cold season solar heat gain.
  2. Orientation of the windows to maximize cold season solar heat gain.
    1. And reduction of window space on the other side of the building.
    2. Use of multi-paned windows for insulation purposes.
  3. Use of “thermal mass” structures to store cold season heat gain, or warm season coolness.
    1. Trombe walls, concrete or stone floors, “water walls”, swimming pools etc.
  4. Use of lots of insulation in walls, ceilings and covering windows to reduce heat loss.
  5. Use of vegetation (deciduous trees) to shade the building in summer, admit sunlight in winter.

I have not taken any architecture courses in the last 30 years to know to what extent these principles have infiltrated the academic consciousness, but judging from the architecture of the last 30 years, it’s not a whole lot.

A round building is a building crying out for solar heating and cooling components. The shape itself guarantees that some part of the building will always be facing the sun no matter what time of day (not night of course) or year it is. Simple placement of windows on a curved surface will allow for winter sun all day long. This results in a steady solar heat gain as opposed to the few hours around solar noon during which a flat wall will tend to overheat the interior space. Add a few of the other passive solar principles, and you have a very comfortable home.

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