Living in Nevada, the sun is an almost constant companion. This gives Nevadans a unique opportunity to use solar radiation powers for good. In April, a tour of southern Nevada homes shed some light on the subject of solar powered homes. Hosted by the American Solar Energy Society, this Nevada branch of the National Solar Tour explored homes that used both passive and active solar power, thermal hot water systems, and other environmentally features. However, unless you're a green technologies expert, or took the tour, you may not know the difference between passive and active solar, or how thermal hot water is different than average. Let me help you understand!
Active solar technology is the one that most people may be familiar with. It involves having a solar panel that collects the sun's energy and converts it into electricity. These have a battery where energy is stored, so electricity can still be used at night, and, to a certain extent, on cloudy days. Solar panels are an excellent way to make electricity, especially in remote areas. While they are moderately costly to set up, and do require some maintenance, they provide reliable and free electricity, even in climates far less sunny than Nevada's.
Passive solar technologies are far older than active ones, and involve utilizing the natural heat and light the sun creates, without converting it in any other way. Have you ever noticed that after a long, hot day, south-facing rocks, pavement or brick and adobe buildings will radiate warmth? They have spent the day passively collecting solar energy, and are releasing it. Some materials are better at absorbing and storing that heat energy than others. For example, wood insulates, meaning it will block temperatures, whereas stone will absorb and release temperatures. Homes that are built to take advantage of passive solar are often constructed of brick, adobe or concrete. Cob is another passive-solar-friendly and ancient building material that is going through a revival of sorts. It is made of sand, clay and straw, similar ingredients as adobe, but adobe is baked into bricks and stacked, whereas cob structures are free-formed while the material is wet. Passive solar homes usually have a lot of windows lining their south walls, and less so their east and west walls, with little to no windows on the colder north sides. These windows do two things. First, they provide natural light inside the home, one aspect of passive solar. Second, they allow heat to come into the home. If the home has a stone tile floor and even walls, that tile will absorb the heat, releasing it later when the outside temperature drops.
Passive solar homes can be designed to be cool in summer while using the sun to warm them in winter. For example, if shutters are closed during summer months, the home will remain much cooler. Also, the height and angle of overhang can be considered to maximize the windows exposure to low winter sun, but minimize exposure to the high summer sun. Alternatively, I saw an interesting example of someone planting deciduous trees on the south side of their home. In the winter, the trees had no leaves and so let in a lot of light and heat. In the summer, their thick greenery provided shade that kept the house cool.
So that is the major difference between active and passive solar technologies. Since passive solar is essentially free, it would be wise for any architect or home designer to take it into consideration when building new homes. Well designed passive solar homes can greatly reduce their electrical energy needs. And while active solar is brilliant technology, it still takes many resources to create. Plus, it may be superfluous in an area with an existing electrical source.
As for thermal water heating, it too is a very simple concept. Home made thermal water heaters can be as simple as an outdoor water tank painted black, but that's a little crude for most tastes. However, there are a variety of styles out there. Some have panels that are metal painted black and enclosed with glass, with copper pipes filled with water running through them. This water will heat, and is then pushed by gravity into an insulated storage tank. Some solar water heaters use a similar set-up but with tubes filled with anti-freeze that are then hooked up to a heat transfer loop, where water in a storage tank is heated. Whatever system you use, thermal water heating is surprisingly affective.
There are a lot of ways to take advantage of the sun and use less electricity. Check out next year's National Solar Tour to see them for yourself.
