Performance of a collector-storage solar air heating system for building mechanical ventilation preheating in the cold area

Abstract

The application of solar thermal energy to preheat cold fresh air for mechanical ventilation could save a lot of energy and ensure the stable operation of the ventilation system. In this paper, a kind of collector-storage solar air heating system (CSSAHS), in which the thermal storage unit (TSU) is characterized by a dual S-channel for heat transfer, is proposed and the mathematical model for the integrated system was established. The model including the TSU, solar air collector, heat recovery device, and the fan was verified by an experimental study set up in a typical cold city in China. The model has been verified by experiments. The simulation results demonstrate that fresh air is the most important factor affecting storage/release efficiency. The increasing rate of heat release efficiency in the range of fresh air temperature -6–18°C is about 1.58%/°C. The solar heat collector area and the size of the TSU suitable for representative cities in cold regions are optimized based on multi-condition simulation analysis. The CSSAHS can preheat fresh air for 5 h after heat storage and the release efficiency is between 52 and 74%. Compared with other systems, the energy-saving rate of the CSSAHS is 26.5–33.3% in cold winter, and the heat supply ratio of the TSU is 24.4–35.1%.

Keywords

• Phase change energy storage
• Air convection
• Parameter optimization
• Fresh air heating