**2. SolarWatt Park and the passive solar house**

*Wind Solar Hybrid Renewable Energy System*

creating sustainable rural development.

space of a house.

However, the use of improved thermal building envelope, bioclimatic design,

In South Africa, the housing shortage in most rural communities resulted in the mass construction of houses (low-cost) in the Reconstruction Development Program (RDP) in 1994. Since the inception of low-cost housing (LCH), more than 4.9 million households have been accommodated with over 2.3 million backlogs [5, 6]. According to Klunne, LCH are designed with no consideration of thermal energy efficiency, as they cannot utilise solar energy for space heating. He further indicated that uncontrollable heat exchange between the inner and outer space of the house due to openings and cracks on the building envelope leaves the inner space extremely cold in winter [7]. In 2005, Overy also found that the quality of LCH is poor with 90% of newly built houses not conforming to the national norms and standards. In his report, he also eluded that corruption and the use of unqualified contractors (builders) are at the forefront of the nature of the houses [8]. However, LCH dwellers tend to bear the burden as they spend a significant amount of their income to achieve thermal comfort indoors [9]. Most households that cannot afford electrical energy resort to the use of firewood, coal, paraffin heaters, or thick clothing as alternative sources of energy for heating. This results in poor indoor air quality, cold-related illness, early child motility, respiratory diseases, etc. [10, 11]. Needless to say, the provision of LCH is a positive approach to rural development in the country, but incorporating passive solar design will improve the welfare of occupants and energy consumed in space heating as well as cooling,

The ambient weather of a house possesses a significant amount of energy required to naturally heat or cool the inner space at little or no expense. At the same time, the uncomfortable thermal condition indoors is due to the uncontrollable interaction between the indoor and ambient weather factors [12]. Hence, to efficiently utilise the ambient weather energy indoors, a selective thermal exchange between the inner and outer environment is required; this process is known as passive solar or bioclimatic design [13]. A passive solar design uses heat movement such as conduction, convection, and radiation to admit and distribute heat in the inner

On a typical sunny day, heat is transmitted through the windows due to radiation and conduction. The transmitted heat is stored and distributed by furniture and indoor air due to conduction and convection, respectively. Minimum infiltration air heat transfer through enhanced airtightness and controlled ventilation components are among the strategies of passive solar design. Conductive heat transfer through the perimeter walls of a passive solar house is also avoided as it is uncontrollable [14]. Regarding cooling, strategic locating and sizing of windows are used to achieve various airflow indoors. Windows at the windward and leeward side of the

house create pressure difference indoors, resulting in a cross-ventilation [15, 16]. Also, locating windows or vents at significant height results in another form of airflow known as stack effect. Stack effect occurs due to vertical air temperature variation indoor. Therefore, the rate of airflow increases with an increase

In both aspects of passive solar design mentioned above, the windows play a vital role, considering the building envelope components, whereas the sun and wind constitute the ambient weather influencing factors. The windows in a passive solar house are strategically located and sized to take advantage of the

in the height between the upper and lower windows or vents [17].

and energy-efficient appliance, as well as light fittings, has seen the offset of energy demand from floor and population growth in the building sector [3]. Thus, final energy demand in the building sector only rose by 5% between 2010 and 2017. Within the above specified period, a significant decline in space heating was

observed, while improvement in space heating is not visible [4].

**208**

SolarWatt Park is located at the University of Fort Hare, Alice, in the Eastern Cape, South Africa. Alice is classified in the temperate interior (zone 2) climate of South Africa [18]. Typical annual season of Alice is characterised by a hot summer and mild (no snow) winter, with an average dry bulb temperature of 29 and 15°C, respectively. The east wind is predominant in summer, while the winter is dominated by the west wind. An average wind speed of 2.5 m/s is experienced in Alice throughout the year [19]. A climatic map of South Africa [20], the Google earth map of SolarWatt Park and the passive solar house are presented in **Figure 1**.

The site was found suitable for the design and construction of the passive solar house due to its clear north side with no sunrays' obstacle such as tall trees, mountains and high-rise buildings. Therefore, the house was designed with its major glazing area facing north which is by the energy-efficient building design recommendation in South Africa [18, 20]. A simulated daily sun path of the house with respect to its orientation is shown in **Figure 2**.

In the northern hemisphere, north-orientated housing design guarantees optimum sunray penetration in the winter season due to the low-angle sun. The penetrated sunrays, therefore, provide heating and daylighting indoors. However, the 44-cm long eaves are used to prevent overheating indoors during the summer season by blocking direct sunrays. To this effect, the two large north-facing windows (see **Figure 2**) distribute solar radiation to the northern floor area of the house, while the clerestory windows channel solar radiance to the southern floor area. Hence, even solar radiation distribution is achieved indoors.

Meanwhile, the clerestory windows enhance indoor passive cooling due to convectional current and various wind effects through effective operations of the windows [16].

Furthermore, the house is made up of 10 m × 8 m (80 m2 ) floor area and consists of a bathroom, an open plan living room/kitchen and two north- and south-facing bedrooms. The floor area was arranged to ensure optimum and uniform distribution of solar radiation. The floor plan of the house indicating the floor arrangement is shown in **Figure 3**.

The floor plan was virtually partitioned into three thermal zones. Zone 1 marked with blue diagonal cross-hatch lines filled region is the living room/kitchen. The red diagonal up lines filled region used to indicate the north-facing bedroom is zone 2, while the south-facing bedroom is zone 3, represented by the region filled with green vertical lines. The bathroom was not shaded since it is not considered as a thermal zone.

In 2009, the construction of the passive solar house was estimated to be \$36, 579.55 with 1.00 USD equivalent to 11.76 ZAR, while its counterpart cost is \$8505.62 [21]. In spite of the cost margin, passive solar house presents a decent home compared to conventional low-cost house [9, 16, 22].

**Figure 2.** *A 3D view sun path simulation of the house.*

**211**

**Table 1.**

8 μV m<sup>−</sup><sup>2</sup>

*Towards Sustainable Rural Development in South Africa through Passive Solar Housing Design*

The indoor and outdoor thermal condition measurement deals with the air temperature and relative humidity in both environments. Therefore, HMP60 temperature and relative humidity probe were used to measure the indoor as well as the outdoor air temperature and relative humidity of all zones in the house. The HMP60 probe uses a platinum resistance temperature (PRT) detector to measure air temperature, while air relative humidity is measured by capacitive relative humidity sensor [23, 24]. The measurement specifications of HMP60 probe temperature and

Three sets of HMP60 probes were used to measure the indoor air temperature and relative humidity. In each zone, one HMP60 probe was suspended at the height of 0.8 m to ensure that the measured air temperature is nearest to the temperature felt by the occupants. At the same time, the probe does not obstruct the activities of the occupants. The locations of the HMP60 probe in the house and a set outdoor

As shown in **Figure 4(b)**, the outdoor air temperature and relative humidity measuring probe was housed in a 6-plate naturally aspirated radiation shield. The white painted radiation shield enables it to reflect solar radiation. At the same time, the louvre allows natural free flow of air through the shield, thereby keeping the probe as close as possible to the ambient air temperature (eliminating solar effect)

In this study, solar radiation measurements cover ambient global horizontal irradiance (GHI) and global irradiance at the four perimeter walls of the house. Due to atmospheric interference, the sum of direct and diffuse solar radiation reaching the earth surface, excluding albedo, is called global radiation, and it can be observed on vertical and horizontal surfaces. Thus measured global radiation on a horizontal

and a spectral range of 285–2800 nm. Its response time is less than 1.7 s

At 0–40°C and +40°C to +60°C 0–90 5

90–100 5

90–100 7

(63%) and 5 s (95%) [29]. The outdoor weather setup was elevated by 1 m above the roof, to ensure an unobstructed space for the radiometer. The pyranometer's dome was also cleaned twice per week to keep the dome clear of dew, dust,

**Parameters Measurement range Accuracy (±)** Temperature (°C) −40 to +60 0.6 Relative humidity (%) At 0–40°C 0–90 3

At the right-hand side of the outdoor weather monitoring setup in **Figure 4(b)**, the horizontally levelled Kipp and Zonen CMP-11 pyranometer was used to monitor the global horizontal irradiance (GHI). The pyranometer uses a 32-junction thermopile to measure solar radiation with a sensitivity of

*DOI: http://dx.doi.org/10.5772/intechopen.85997*

**3.1 Indoor and outdoor thermal conditions**

relative humidity sensor are given in **Table 1** [25].

weather station are indicated in **Figure 4**.

and water vapour [26].

**3.2 Solar radiation measurements**

plane is called global horizontal irradiance [27, 28].

*HPM60 temperature and relative humidity sensor specification.*

**3. Methods and instrumentation**

*Towards Sustainable Rural Development in South Africa through Passive Solar Housing Design DOI: http://dx.doi.org/10.5772/intechopen.85997*
