Thermal characterization of a passive solar house in Alice, Eastern Cape province, South Africa
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Date
2018-10
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University of Fort Hare
Abstract
A passive solar hoμse was designed and constructed as a prototype low-cost energy efficient house to avert the underperforming low-cost housing plaguing the rural communities in South Africa. Thermal performance characterisation of the passive solar house and developing a thermal load model of a single family house was the aim of this research. The net thermal energy change in the inner space of a house is equal to the difference between the total heat gain and the total heat loss from the inner space. This is given by the first law of thermodynamics and serve as the basic principle of a house thermal load evaluation. To this effect, the various contributors of heat gain and loss of the passive solar house were identified. Typically, heat gain in a house occurs in the form of solar heat gain, heat transmission through the building envelope, ventilation/infiltration and internal heat gain. Whereas, heat loss occurs in the form of conductive (building envelope) heat transfer and ventilation/infiltration. As such, the indoor and ambient weather parameters over a year period were monitored. Monitored parameters include air temperature, global horizontal irradiance, and global irradiance at the various elevations of the house. The surface temperature of the building envelope components such as the floor, perimeter walls (inner and outer surface) and the inner surface of the roof was also monitored. At the same time, the occupancy daily
activities and operation of the house were closely observed. The occupancy activities refer to the number of occupancies, type of appliances used, lighting, time in and out, as well as their operation of the ventilation components.
The measured meteorological parameters were analyzed in term of data integrity, seasonal distribution and thermal implication. It was found that 5% of the total measured data were lost due to the mechanical error of the data acquisition system. The obtained 95% of data was found sufficient to present tangible thermal behavior of the house. Hence, working with the available data, the measured meteorological data were further presented in typical summer and winter days. In term of operations of the house, a typical working-class family was occupying the house during the monitoring period. As a result, the house had a minimum occupancy during the day and maximum at night time. It was also found that during the weekends, the house was usually unoccupied. Also, during the monitoring period," all appliances were located in the living room/ kitchen (zone 1). Although, only the 7.70 kW stove
and 0.78 kW refrigerator were taken into consideration for the internal heat gain analysis. A total heat gain of2.10 kW was obtained with both appliances in used, and the refrigerator alone generates 0.25 kW. The daily cumulative heat energy without the influence of other heat sources or sink was 0.58 kWh/m2. Another aspect of internal heat gain taken into consideration was electrical lighting fixtures. A total of five 11 W CFLs were installed in the house. Three of the installed lamps were located in zone 1. and one each in the north and south facing bedrooms (zone 2 and 3, respectively). The lighting daily cumulative heat energy was found to be 1.33 Wh/m2, 0.71 Wh/m2 and 0.88 Wh/m2 in zone 1, 2 and 3, respectively.
Also, the air exchange rate of each zone with different scenarios of the ventilation components operation was performed upon completion of the house. The findings of the air exchange testing were used to evaluate ventilation/infiltration air heat transfer of the house. The daily cumulative heat energy due to ventilation and infiltration was 0.196 kWh/m2, 0.033 kWh/m2, and 0.080 kWh/m2 in zone 1, 2, and 3, respectively. Based on the indoor and ambient air temperature difference, the said heat energy indicates the amount of heat loss. As such, the daily cumulative internal heat energy in zone 1 was reduced by 0.38 kWh/m2. Transmission heat transfer through the components of the building envelope was analyzed in the form of opaque and transparent components. Opaque components further comprise the walls and roof. The south wall was found to have the maximum heat loss with a daily average of 161.95 Win the summer season and 147.14 Win the winter season. The north wall was found to have the maximum heat gain with 153.43 Wand 201.60 Win summer and winter seasons, respectively. In both seasons, the solar irradiation on the perimeter walls was reduced by more than 95%. Based on the roof design, the house ceiling was classified into crawlspace and skillion ceiling design. Whereby, the skillion ceiling covers the southern floor area, while the crawlspace ceiling dominates the n01ihem floor area. In both seasons, heat loss through the crawlspace ceiling was approximately 54% higher than that of the skillion ceiling. However, the average daily heat loss and gain through the ceiling of the whole
building were 0.19 and 0.45 kW, respectively in the summer season. In the winter season, the daily average heat loss was 0.18 kW and a gain of 0.44 kW.
Description
PhD Thesis
Keywords
Solar energy, Sustainable buildings, Housing
Citation
Ochuko,K.O.Thermal characterization of a passive solar house in Alice, Eastern Cape province, South Africa.Alice.University of Fort Hare.