**5. Conclusion**

the bottom plate of the PVT collectors, and the subscripts *conv*, *rad*, *nc*, *wind* and *sky* indicate convective, radiative, natural convective, wind-driven and sky radiative, respectively. More

The coefficient of performance (COP) of the heat pump system with the integrated PVT col-

To evaluate the performance of this system, two cases were designed and simulated under winter weather conditions in Melbourne. In the *baseline* case, only an air source heat pump was used to condition an Australian house. In the *PVT-PCM* case, the air source heat pump integrated with PVT and PCMs was used for space heating. **Figure 19** presents the one-week

**Figure 20** compares the accumulated electricity generation and consumption during the test days and **Figure 21** illustrates the operation status of the heat pump unit under the two test cases. It is worthwhile to note that the PVT direct heating mode was not considered in this study. It can be seen that the accumulated electricity consumption under the PVT-PCM case was 42.3 kWh, which was much lower than the baseline case of 72.0 kWh. In comparison to the baseline case, the electricity saving was 41.1%, which was achieved through decreasing the operating time of the air source heat pump. The total electricity generation of the PV panels was 156.5 kWh under the *PVT-PCM* case. The average COP of the heat pump system with the integrated PCM layers in the building ceiling and PVT collectors for space heating during the selected week was 5.21, which was higher than that of the air source heat pump system in the *baseline* case (i.e. 3.06). The above-mentioned results indicated that this integrated heat pump system with PCMs and PVT collectors can substantially reduce the electricity con-

Time (h)

Solar radiation

Sky temperature

00 12 24 36 48 60 72 84 96 108 1 02 132 144 156 168

Ambient temperature

*EHP* <sup>+</sup> *EPVT*,*fan* <sup>+</sup> *EPCM*,*fan*

. (5)

Total horizontal

solar radiation (W/m2)

details about the PVT model and the model validation can be found in Ref. [41].

where *E* is the electrical energy consumed, and *Qheating* is the heating energy demand.

lectors and PCMs is determined by Eq. (5).

36 Sustainable Air Conditioning Systems

*COP* <sup>=</sup> \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ *Qheating*

winter weather conditions used for performance tests.

sumption for winter space heating.


**Figure 19.** Weather data of a winter week.




Temperature (°C)

0

10

20

Solar-assisted HVAC system with integrated PCMs are a good alternative to conventional fossil fuel-driven vapour compression systems. Due to the intermittency of solar energy, the integration of PCM thermal energy storage units with solar-assisted HVAC systems provides a great opportunity to maximise the utilisation of solar energy and thus to increase the efficiency of HVAC systems. Two different HVAC systems with integrated PCMs and solar photovoltaic thermal collectors were presented, and their performance was investigated. The results showed that the solar thermal contribution for the desiccant wheel regeneration was 96.5% when using integrated PVT collectors and PCMs during the test period. The average COP of the heat pump system with integrated PVT collectors and PCMs for space heating was 5.21 during the test period, which was higher than the baseline case with a COP of 3.06. The results showed that the system performance can be improved through the integration of PCMs. For solar-assisted HVAC systems, control will be essential to ensure that the system can always operate at the optimal performance.
