**Solar-Assisted HVAC Systems with Integrated Phase Change Materials Change Materials**

**Solar-Assisted HVAC Systems with Integrated Phase** 

DOI: 10.5772/intechopen.72187

Zhenjun Ma, Haoshan Ren, Wenye Lin and Shugang Wang Shugang Wang Additional information is available at the end of the chapter

Zhenjun Ma, Haoshan Ren, Wenye Lin and

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.72187

#### **Abstract**

[48] Zouaoui A, Zili-Ghedira L, Ben Nasrallah S. Solid desiccant solar air conditioning unit in Tunisia: Numerical study. International Journal of Refrigeration. 2017;**74**:662-681

[49] Gugulothu R, Somanchi NS, Banoth HB, Banothu K. A review on solar powered air conditioning system. In: Procedia Earth and Planetary Science, editors. Global Challenges, Policy Framework & Sustainable Development for Mining of Mineral and Fossil Energy Resources (GCPF 2015); 17-18-04-2015; Karnataka, India. Elsevier; 2015. pp. 361-367 [50] Hao EKJ, Ghaffarian Hoseini A. Solar vs. conventional air-conditioning systems: Review of LIMKOKWING University Campus, Cyberjaya, Malaysia. Journal of Creative Sustainable

Architecture & Built Environment. 2012;**2**:23-32

20 Sustainable Air Conditioning Systems

Solar-assisted heating, ventilation and air-conditioning (HVAC) systems are receiving increasing attention. This chapter presents the development of HVAC systems with integrated solar photovoltaic-thermal (PVT) collectors and phase change materials (PCMs) to reduce building energy consumption while providing satisfactory indoor thermal comfort. PVT collectors, which can generate both thermal energy and electricity simultaneously, are a promising technology for developing high-performance buildings. As solar energy is intermittent, the integration of phase change materials (PCMs) with PVTdriven HVAC systems can provide an opportunity to effectively utilise solar energy and maximise the performance of HVAC systems. The results showed that the coefficient of performance (COP) of an air source heat pump system with integrated PVT collectors and PCMs was 5.2, which was higher than the use of the air source heat pump only (i.e., 3.06) during the test period investigated.

**Keywords:** HVAC system, photovoltaic-thermal collector, phase change material, thermal energy storage, solar energy, performance evaluation

#### **1. Introduction**

Building heating, ventilation and air-conditioning (HVAC) system is one of the major energy consumers in modern buildings. Promoting the energy efficiency of building HVAC systems is therefore essential to reduce building energy consumption and carbon footprint. Over the last several decades, many efforts have been made for the development of cost-effective HVAC technologies and solutions, including, but not limited to, desiccant cooling, heat recovery, renewable energy integration, optimal design, intelligent control, advanced fault detection and diagnosis and thermal energy storage. Among them, solar photovoltaic-thermal (PVT)

Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons

collectors and thermal energy storage (TES) using phase change materials (PCMs) are receiving increasing attention for developing high-performance HVAC systems.

Solar PVT collector is a combination of photovoltaics and solar thermal systems, which can generate both electricity and thermal energy simultaneously from one integrated component [1]. Compared to the use of separate solar technologies for heat and electricity generation, using solar PVT collectors is more cost-effective [2]. Phase change material (PCM) with a high energy storage density and the capacity to store thermal energy at a relatively constant temperature is being considered as a future technology to reduce building operating cost and provide better indoor thermal comfort [3, 4]. PCM has been used to increase the local thermal mass of building envelopes or incorporated into building HVAC systems to provide functional purposes and enhance overall system efficiency. As solar energy is intermittent and has a low energy density, the integration of PCMs with PVT collectors may provide an alternative solution to effectively use solar energy and enhance the performance of building HVAC systems. For instance, Su et al. [5] investigated the performance of an air-based PVT collector integrated with PCMs using different configurations. The results indicated that by attaching a PCM layer on the upper side of the air channel of the PVT collector, the overall efficiency of the PVT collector can be improved by 10.7% in comparison to the use of the same PVT without using the PCM. The electrical and thermal performance of a water-based PVT collector incorporating PCMs was also studied [6]. The results showed that the energy output of the PVT collector can be maximised by incorporating a PCM layer with a thickness of 3.4 cm and a melting point of 40°C under the weather conditions in Nanjing, China.

The performance of air-based PVT collectors is highly influenced by the factors such as solar irradiation, air flow rate, the slope and the orientation of the collectors. **Figure 3** shows the measured solar irradiance, ambient air temperature, the inlet air temperature and outlet air temperature of a PVT collector tested in a laboratory-scale test rig (**Figure 4**) under the two summer test days in 2014 with a fan operating frequency of 10 Hz (i.e. ~50 L/s). It can be seen that, during the daytime, a maximum temperature rise of 14.0°C was achieved when the air flowed through the PVT collectors. During the night-time, a reduction in the air temperature of 1–2°C was achieved in the two test days through night-time radiative cooling. **Figure 5** illustrates the instantaneous thermal energy collected, electricity generated and the electrical efficiency of the PVT collectors under the two summer test days. There was a slight delay between the electricity generation and thermal energy generation due to the low response of temperature to the changes in solar radiation. The maximum instantaneous thermal energy collected from the PVT collectors and the maximum instantaneous electricity generation in the two summer test days were 840 W and 408 W, respectively. The electrical efficiency of the PV cells was relatively stable except during the morning of the first test day due to large

Solar-Assisted HVAC Systems with Integrated Phase Change Materials

http://dx.doi.org/10.5772/intechopen.72187

23

The above-mentioned results showed that, besides electricity generation, a substantial amount of thermal energy can also be collected. The thermal energy collected during the winter daytime can be directly used for space heating, and the thermal energy collected during the summer night-time can be directly used for space cooling. However, the thermal energy collected during the summer daytime cannot be directly used for space conditioning unless it is used to drive air conditioning systems such as rotary desiccant cooling

**Figure 2.** Air-based PVT collectors implemented in a net-zero energy office building.

variations in solar irradiance.

**Figure 1.** Illustration of an air-based PVT collector.

systems.

This chapter is structured as follows. Section 2 presents a brief introduction to solar PVT collectors and PCMs. Section 3 provides an overview of solar-assisted HVAC systems with integrated PCMs. Section 4 presents the development of two HVAC systems with integrated PVT collectors and PCMs. Section 5 provides a summary of this chapter.
