The first practical instance of controlling the sun's energy might have been when someone noticed that a magnifying glass, held at the right angle, could set fires and burn ants. And from there, it was practically eons before humans discovered a way to use the sun's rays truly constructively.
The first silicon photovoltaic cell (what we know of as "solar panels") was produced in the United States in 1954. Our current solar panels are a direct descendant of this technology -- they've just been made more efficient over the years.
Over the years, from the 1950s through now, various residential and commercial buildings were developed with different solar priorities. One office building gained recognition for solar water heating. Residential milestones went from sunrooms to hybrid solar/grid systems to standalone fully solar homes (one of the first of which was completed in 1983). In 2000, a Colorado family completed a solar installation that nearly completely powered their home for their eight-member family.
There are other useful innovations besides roof-mounted solar panels, such as a modified version of a radiant heating system. By carefully routing the home's plumbing, water can be heated by the sun and, as it's pumped through the house, that heat can be dissipated to help control the house's temperature. This type of heat won't add to the home's electric consumption. In a nationwide solar home design competition in 2007, a group of students from Santa Clara University in California even figured out how to use a solar radiant heat system to help cool the house, as well as heat it. As appealing as this idea is, it may be particularly difficult to execute; a Tennessee couple who designed a home with a similar system had trouble finding a contractor up to the challenge [source: Lewis]. The Tennessee house, though not part of a competition, evokes the same sense of spirit. It's notable for its use of SketchUp, an architecture and design program from Google. The home's other features include energy-efficient LED lighting and insulation derived from corn.
Some designs give more responsibility and flexibility to the home's occupants. In the 2007 competition, a team from Virginia Tech added weather monitors to the house, which, among other features, would help the residents decide when to open and close insulated window shutters to maintain the desired interior temperatures as efficiently as possible. In 2010, there was a similar competition in Europe. A group of students in England focused on designing a prefabricated house that could be ordered and assembled anywhere -- and they made sure it complied with the country's most restrictive building codes. They hoped to demonstrate that prefab solar houses were an approachable and desirable alternative to custom construction or an inefficient conversion of an existing home. As a bonus, the assembly-line simplicity of prefabrication might negate concerns about wasting energy with new custom construction projects.
Cost, of course, can make or break any initiative. The price of solar technology has held fairly steady from decade to decade, but there were a few notable improvements. Solar cell prices were reduced by about 80 percent in the 1970s, which drastically improved their potential. And in February of 2009, First Solar, a manufacturer of solar panels, announced that the cost to make its wares had dropped to a dollar per watt -- an eagerly-anticipated milestone. Experts say that "grid parity" is the necessary milestone to making solar power really work. Grid parity is achieved when solar power costs the same as conventional power -- without the help of the grants, subsidies and rebates that make it possible for many customers. At that point, the supply probably won't be able to keep up with demand, since some of the solar panels' raw materials are hard to obtain in large quantities [source: Hutchinson].