Comparative study on performances of a heat-pipe PV/T system and a heat-pipe solar water heating system

ABSTRACT

The heat-pipe solar water heating (HP-SWH) system and the heat-pipe photovoltaic/thermal (HP-PV/T) system are two practical solar systems, both of which use heat pipes to transfer heat. By selecting appropriate working fluid of the heat-pipes, these systems can be used in the cold region without being frozen. However, performances of these two solar systems are different because the HP-PV/T system can simultaneously provide electricity and heat, whereas the HP-SWH system provides heat only. In order to understand these two systems, this work presents a mathematical model for each system to study their one-day and annual performances. One-day simulation results showed that the HP-SWH system obtained more thermal energy and total energy than the HP-PV/T system while the HP-PV/T system achieved higher exergy efficiency than the HP-SWH system. Annual simulation results indicated that the HP-SWH system can heat the water to the available temperature (45°C) solely by solar energy for more than 121 days per year in typical climate regions of China, Hong Kong, Lhasa, and Beijing, while the HP-PV/T system can only work for not more than 102 days. The HP-PV/T system, however, can provide an additional electricity output of 73.019 kWh/m², 129.472 kWh/m², and 90.309 kWh/m² per unit collector area in the three regions, respectively.

KEYWORDS:

• Efficiency
• heat pipe
• photovoltaic/thermal
• simulation
• solar system

Additional information

Funding

The study was sponsored by the National Natural Science Foundation of China (51308342), the Shenzhen Research Foundation of Science & Technology (JCYJ20140418182819191 and JCYJ20130329113322731), the Key Laboratory of New Lithium-ion Battery and Mesoporous Materials (20120208), and the Key Laboratory of Efficient and Clean Energy Utilization of Guangdong Higher Education Institutes, South China University of technology (KLB10004).