Category History and Overview of Solar Heat Technologies
One of the important lessons architects and builders of passive homes have learned is not to use the more extreme passive techniques and to use direct gain in moderation. By limiting the solar savings fractions to 25-30 percent, they can make the building look and feel quite conventional. At this performance level, standard building practice seems to provide enough thermal mass to meet diurnal energy storage needs. This is good because adding thermal mass has turned out to be more expensive than originally thought. The other important reason for settling for a modest energy saving is that more aggressive strategies can lead to surume r overheating or air-conditioning energy requirements that offset winter heating energy savings. Daylighting is also tricky...Read More
Just as the main drawback to the use of solar energy for space heating is the mismatch between solar availability and heat demand, the main appeal of solar-driven space cooling is the coincidence between supply and demand. This appeal is heightened by the growing worldwide demand for air-conditioning, and the rising cost of providing electricity to meet the summer peaks of many utilities. But like solar heating, the goal is illusive. In order to produce a cooling effect, solar heat must be used to drive a heat engine (a thermodynamic cycle). Unfortunately, the efficiency of available heat engines and cycles at temperatures compatible with solar collectors is not very high. This means that large collector areas are required to meet given loads...Read More
Unlike solar water heating or swimming pool heating, active solar energy systems for building space heating were rarely used in the United States prior to the energy crisis of 1973. Until then, there were only four known solar houses in the United States: two research houses at MIT, one at the University of Delaware, and the one built in Denver by Active Solar Systems editor George Lof. Because space heating is such a large part of the U. S. energy budget, the government solar energy plans developed in the 1970s placed considerable emphasis on both R&D and demonstration programs for solar space heating.
The gove^rnment demonstration programs and, later, the tax credits stimulated a demand for active solar space heating systems that eventually resulted in the installation of perhaps 40,000...Read More
Solar water heating had flourished twice in the United States prior to the beginning of the large government solar programs: in California just after the turn of the century and in Florida in the 1930s-1950s. The gov – e^rnment efforts in support of solar water heating therefore focused on demonstration, field monitoring, testing and standards, and public information dissemination. Of course, much of the research and development effort in solar collectors, storage, materials, and control was applicable to solar water heating as well as to the less advanced applications.
The single government program that had the greatest impact on the adoption of solar water heating by consumers was, of course, the residential tax credit program, which originally provided a 30 percent federal tax credit...Read More
The most successful application of the active solar technologies from a market perspective was swimming pool heating. Although this application never received federal incentives, and was not officially included in the DOE R&D programs, solar swimming pool heating has been popular in the sunny parts of the country for decades. Swimming pool heating collectors are normally unglazed and often made from inexpensive polymers. Systems require no storage (the pool is the storage element) and are easy to install and maintain.
According to incomplete EIA statistics, 85 to 100 million square feet of low-temperature collectors have been sold in the United States since 1973. These collectors are used almost exclusively for swimming pool heating...Read More
An active solar energy system for a building is generally considered to be any collection of water heating or space heating or cooling equipment that includes a solar collector as one of its elements. Conceptually, at least, active solar energy systems differ from conventional building energy systems only in that the conventional heat source is totally or partially replaced with heat from a solar collector. It is not surprising, therefore, that active systems were considered the most direct and straightforward approach to the utilization of solar energy in buildings and received the greatest attention and funding in the government program that evolved in the post-oil embargo years.
Gove^rnment-supported activities in active systems included R&D, demonstrations, and incentives, for water he...Read More
Passive cooling research was the poor stepchild of passive heating. There was never a coordinated program, but individual researchers did receive support and made important contributions. There were also projects that included passive cooling techniques alone or in combination with heating. The biggest concern about cooling in the passive program was how to limit the need for extra cooling in passively heated buildings (i. e., heat avoidance).
The mechanisms available to the architect or engineer for influencing the comfort of a building in a hot climate are the same heat and mass transfer processes that control solar heating systems (and all thermal systems): radiation, conduction, convection, evaporation, and condensation...Read More
Interest in passive solar heating systems grew rapidly on a national scale following the first Passive Solar Conference in Albuquerque in 1976. This was a landmark event, attended by a strange mix of Washington bureaucrats, national laboratory scientists, and hippies. They did not always communicate well. When an architect was asked how much storage the passively heated house he designed contained, he responded that it was ample: two closets in the master bedroom and a full attic. They seemed to spend more time debating what was or was not “passive” than on understanding fundamentals. Although they were sure that passive heating was economical, no one had any idea what the extra costs really were. But there was excitement. Today, people would call what happened a paradigm shift...Read More