5.2 Pilot Study Part 2

Figure 37: Pilot study part 1 results

Note: For all Graphs illustrated as figures in this document, the abbreviation SAH refers to Solar Air Heater.

45 40 35 30 25 20 15 10 Solar Air Heater: Pilot Study

5 0

06:00 08:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 00:00 02:00 04:00 06:00 Outlet of SAH Ambient Temperature

After analysing the data, it is clear that the solar air heater produced sufficient heat when solar energy was available from 8:00 till 16:00, as indicated in red in Table 9. After the solar energy was unavailable from 16:00, the heat generated from the solar air heater simultaneously went down. The airspeed was measured at 2m/s at the outlet of the solar air heater.

5.1.4 CONCLUSION

From the data gathered during part 1 of the pilot study, the solar air heater can generate sufficient heat from solar energy but will require additional heat storage material to provide heat after the solar energy is not available. The solar air heater only discharged sufficient heat for 8 hours of the day at 2m/s.

5.2 PILOT STUDY (Part 2)

Part 2 of the pilot study will focus on the performance of the solar heating system when the rock bed heat collector is connected to the solar air heater. The rock bed heat collector will only be filled with 50% of the required rock to determine the heat storage capacity of the rocks.

5.2.1 EXPERIM ENT M ETHOD

The rock bed heat collector will be filled with 0.125m³ of rock. The solar air heater will be connected to the rock bed heat collector with 2 x 50mmØ U-Pvc pipes at the inlet and 2 x 50mmØ U-Pvc pipes at the outlet. The solar air heater was placed at a 26° angle facing North with full solar exposure.

The experiment was conducted for 72 hours from 8:00 on 1 July 2021 till 8:00 on 4 July 2021 during the winter season.

Four data loggers are used during the experiment, and the results from each will be compared to determine the system’s efficiency. One data logger is placed at the outlet of the solar air heater, one within the rock bed heat collector, one at the outlet of the rock bed heat collector, and one logger is placed on top of the rock bed heat collector box to track the ambient temperatures during the day and night.

Figure 38: Solar heating system front view Figure 39: Solar heating system side view (Author, 2021) (Author, 2021)

5.2.2 RESULTS Figure 40: Pilot study part 2 experiment results – Day 1

Figure 41: Pilot study part 2 experiment results – Day 2

80 Heat storage Day 2

70 60 50 40 30 20 10 0 06:00:00 08:30:00 11:00:00 13:30:00 16:00:00 18:30:00 21:00:00 23:30:00 02:00:00 04:30:00 Amient Temperature 47 Top of SAH Rockbed Outlet

Figure 42: Pilot study part 2 experiment results – Ambient Temperature Day 3

80 70 Heat storage Day 3

60 50 40 30 20 10 0 06:00:00 08:30:00 11:00:00 13:30:00 16:00:00 18:30:00 21:00:00 23:30:00 02:00:00 04:30:00 Amient Temperature Ambient Temperature Top of SAH Rockbed Outlet

The results from the 3-day experiment indicate that the solar air heater generated a maximum of 75°C during the day. The temperature within the rock bed reached a maximum of 40°C during the same time the solar air heater reached its peak. The solar air heater is charged from 8:00 till 16:00 each day. The results indicate that the heat storage from the rock bed heat collector proved to store and discharge sufficient heat, which is 5°C or more, compared to the ambient temperature, from 10:00 till 23:00. From 23:00 onward, the rocks discharged heat which is at 4°C and below, compared to the ambient temperature

The results indicate that the system can generate and store heat sufficiently by making use of solar energy. The system will be tested further during the complete experiment.

5.2.3 CALCULATIONS

The results from Part 1 and 2 of the pilot study will be used to calculate the efficiency of the solar air heater.

By calculating the rate at which the solar air heater can replace the air volume within a room or space, the size and efficiency of the solar air heater can be determined. The following formula is used to calculate the rate of airflow at litre per second.

Total area:

Area = π x r² Area = 3.14 x 55mm² Area = 3.14 x 3025mm² Area = 9498.5mm² Area = 9498.5mm² / 1000 (Con verted to metric scale)

Volume of heated air supply by the solar air heater:

= Area x Flow rate = Litre/second = 0.9498 x 2m/s = 1,8996 L/s

Replacement of air:

1000L of air is equal to 1m³ at 23°C 1000L / 1,8996/s = 526,42 seconds to fill air volume 526.42/ 60 seconds per minute = 8.7 minutes It will take 8.7 minutes/ 526.42 seconds to fill up or replace the air of 1m³.

According to the South African Bureau of Standards: Part O (2011: 17), it is illustrated in table 2 that the number of air changes per hour for a living room situated in a dwelling unit should be a minimum of 2. The calculation results indicate that the system will replace the air within a 1m³ air volume 6,8 times within one hour. The air changes will depend on the air volume of the room/ space and will need to be calculated individually when implementing the system on a housing unit.

5.2.4 ALTERATIONS AND CHANGES

After conducting the pilot study, some areas were identified to ensure the system’s heat storage at an optimum rate. Below is a list of items to improve: • Pipe length between the solar air heater and the rock bed heat collector to be shortened to reduce heat loss. • Insulate all exposed pipes. • Ensure all joints of the solar air heater and rock bed heat collector are sealed.

• The rock bed heat collector is filled to full capacity to store heat for more extended periods.

Figures 43 and 44 illustrate the alterations made to the system. The system was used during the entire experiment in Chapter 6.

Figure 43: Revised solar heating system Figure 44: Insulation over exposed pipes (Author, 2021) (Author, 2021)

5.2.5 CONCLUSION:

From the results in Part 2 of the pilot study, it is clear that the system can store heat for at least 7 hours after no solar energy is available by adding the rock to the solar air heater.

Comparing the results from the calculations with the South African Bureau of Standards, the system achieves the minimum requirement of 2 air changes per hour. The results from the pilot study and the calculations indicate that the system can be tested further through the full experiment in Chapter 6. The alterations to the system were done before conducting the full experiment during the next chapter.