Passive sun & shade harvesting systems do not require manufactured systems that generate or distribute energy in order to operate. They are silent – no humming appliances or equipment. They tend to be simple, working with what is already freely at hand. They can be designed or made in a way that they are not dependent upon imported resources or materials. Passive systems can be understood, collaborated with, designed, and/or maintained by the average child or adult. For how to do so, see chapter 4 and appendices 7 and 8 in Rainwater Harvesting for Drylands and Beyond Volume 1, 3rd Edition.
The best passive systems are alive. They grow and get better with time; generate additional resources/potential like food, fertility, and joy; and they sequester carbon while cleaning our water and air (which they also produce). An example is a “solar arc” of trees planted on the east, west, and winter-shade-side of buildings, gardens, livestock pens, and gathering areas—while no trees shade out access to the winter sun on the winter-sun-side in the direction of the Equator (the winter-sun/Equator-facing-side is the south side in the northern hemisphere, or the north side in the southern hemisphere).
A solar arc of trees shades out the hot summer rising and setting sun for free cooling, while allowing for full winter sun access and free heating and lighting (see illustration below). The trees also cool the area in summer with the evaporation of moisture transpiring from their leaves, and they can further warm us in winter by deflecting winds. The trees and their understory plantings can be freely irrigated with the roof runoff, greywater, and other free on-site waters harvested from the building the trees shelter.
Studies have found this solar arc strategy results in over a 50% energy savings when compared to a similar building without such shade trees.
Some other passive sun & shade harvesting systems include:
Ideal orientation of buildings to the sun
How to choose and size windows to optimize passive heating and cooling
Sun & shade traps
Maintaining winter sun access with winter-solstice shadow ratios and solar rights