6.3 Full experiment Part 3: Ventilated cooling system

6.3 FULL EXPERIM ENT - PART 3: VENTILATED COOLING SYSTEM 6.3.1 INTRODUCTION

In parts 3 and 4 of the experiment, the possibility of using the solar heating system as a cooling device was tested. Part 3 focussed on a ventilated cooling system, which uses ambient air to cool the rocks of the rock bed. The system provides fresh air 24 hours per day.

Figure 68 illustrates the ventilated cooling system. The system runs for 24 hours per day without any human intervention. The system allows for 50% fresh air, and 50% recirculated air; this will be discussed further under the methodology. Cool ambient air /cools the rocks during the evening. During the day, the warm air flows over the rocks, and the heat is exchanged between the air and rocks, which allows the warm air to cool down. Cool air is supplied through the outlet of the rock bed.

Figure 68: Diagram of ventilated cooling system

6.3.2 M ETHODOLOG Y

The rock bed heat collector is filled to full capacity with 0.25m³ of rock. The outlet solar air heater will be connected to the rock bed heat collector’s inlet with 2 x 50mmØ U-PVC pipes. The system will make use of 50% fresh ambient air, and 50% recirculated air. One outlet pipe of the rock bed and one inlet pipe (50mmØ U-PVC pipes) will be connected, while the remaining inlet and outlet pipes (50mmØ U-PVC pipes) will remain open 24 hours per day. The glazed panel of the solar air heater is covered with a 500mm x 1000mm x 20mm thick chipboard with 50mm thick polystyrene fixed to the timber board, as illustrated in Figure 69.

Figure 69: Solar heating system glazed

panel enclosed ( Author, 2021)

The circulation fan will be powered by a solar panel during the day, 8:00 am till 16:00 pm and after 16:00 pm till 8:00 am; a 5000mah power bank will power the circulation fan. The experiment was conducted for 72 hours/ 3 days from 6:00 am on 10 October 2021 till 6:00 am on 13 October 2021 during the summer season.

Four data loggers are used during the experiment. 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. One logger is placed on top of the rock bed heat collector box to track the ambient temperatures during the day and night.

6.3.3 RESULTS

Figures 70 to 72 illustrate the results from the ventilated cooling system. Each figure illustrates the results for one day from 6:00 am to 6:00 am (24 hours). Figure 73 illustrates the combined results for the 3-day experiment.

Figure 70: Ventilated cooling experiment results – Day 1

Figure 71: Ventilated cooling experiment results – Day 2

40 35 30 25 20 15 Ventilated Cooling Day 2

10 5 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 Rock bed Storage Rockbed Outlet

Figure 72: Ventilated cooling experiment results – Day 3

Figure 73: Combined Results: Ventilated cooling experiment – 3 Days

40 35 30 25 20 15 Ventilated Cooling Day 3

10 5 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 Rock bed Storage Rockbed Outlet