Potential Residential Solar Heating in the Southeast

Abstract

Southeastern Geographer Vol. 21, No. 2, November 1981, pp. 117-129 POTENTIAL RESIDENTIAL SOLAR HEATING IN THE SOUTHEAST Philip W. Suckling Increasing interest in alternative energy sources such as direct solar energy conversion raises questions regarding the actual potential for meeting energy demand by such methods. Direct conversion of solar energy can be utilized for a variety ofpurposes, notably residential space and hot water heating and, where appropriate, space cooling. The potential magnitude ofthe solar energy contribution depends on numerous factors involving climatic, economic, and engineering problems among others. One of the important roles of geographical climatology in the solar energy field is the climate-effect study of solar radiation income and solar-home feasibility. (J) This study will assess the potential for residential solar use from a climatological viewpoint. Long-term mean data will be studied generating a general assessment which may be of use for overall energy planning . Certain house and solar collection system characteristics will be assumed and held constant in order to allow an evaluation of the geographical distribution of the potential for solar energy use in the southeastern United States. Only space and hot water heating demand will be considered. CALCULATION OFENERGY DEMAND. The analysis requires consideration of a residential dwelling with certain assumed characteristics. The house is a three-bedroom, one-story single-family dwelling with a floor space area of 150 m2 (1,615 ft2). Two conventional construction designs from an energy viewpoint are considered. House design #1 is assumed to have a building heat-loss characteristic (HLC) of 234 kj m~2 (0C day)"1 or approximately 11.5 BTU ft-2 (°F day)-1. This is similar to the Colorado State University experimental solar house and represents a home with about 9 cm (3.5") of fiberglass insulation in the walls and 14 cm (5.5") in the ceiling as well as thermopane glass in all windows. Dr. Suckling is Assistant Professor ofGeography at the University of Georgia in Athens, GA 30602. 118Southeastern Geographer (2) Such features are common in modern conventional new house construction in the southeast. House design #2 is assumed to be a more energy efficient home built to the 1975 standards of the Housing and Urban Development Association of Canada. Such a house would have a HLC of about 180 kj irr2 (0C day)1 or 8.8 BTU ft"2 (0F day)1. Features would include 14 cm (5.5") of fiberglass insulation in the walls and 30 cm (11.8") in the ceiling with triple pane glass windows. This latter housing design will further aid in an assessment of maximum potential direct solar energy use combined with a greater degree of housing insulation . In order to ascertain the space heating energy demand, mean monthly heating degree-days (HDD) based on the period 1941-1970 can be used in conjunction with the HLC of the house as follows: Space Heating Demand = HDD ? HLC x A (1) where A is the house floor space area. Heating degree-days are reported with a base of 65°F (18.3°C). The assumption is made that space heating is needed when the average daily temperature drops below this value. In reality, with increases in housing insulation, a lower threshold value may be appropriate. However, the reported values presently use this threshold (3) and these will be used in this study. Assumed monthly values of hot water energy demand were used (Table 1). (4) These values were based on a typical family of four with water source temperature data representative of Nashville. Naturally, values would vary according to family practices and locality where water source temperatures may be somewhat different. For this study, the same values in Table 1 were applied to all sites. Compared to space heating demand in winter, errors in these hot water energy values would contribute a relatively small error to the total energy demand. Thus, the total monthly energy demand (E) is the sum of the space and hot water heating demands obtained from equation 1 and Table 1. ESTIMATION OF AVAILABLE SOLAR RADIATION. Solar radiation measurements are presently being collected by a network of only 39 stations maintained by the National Oceanic and Atmospheric...