The aim of this study is to address the lack of comprehensive analysis methods for multi-functional Trombe wall systems. The objective is to establish an integrated evaluation system that assesses thermal, purification, and power generation performance. This study introduces a novel multi-objective analysis method coupling energy and exergy efficiency for three types of Trombe wall structures: traditional, thermal-catalytic (TC), and TC–photovoltaic (TC-PV). This study simultaneously monitors heat transfer, formaldehyde degradation, and photovoltaic power generation performance. A key novelty is the introduction of a quantitative index for “purification efficiency” and the revelation of the co-evolution law between PV (photovoltaic) coverage and the three types of efficiency for the first time. This study evaluates three cases: traditional, TC, and TC-PV Trombe walls. The results show that the thermal efficiencies of the three Trombe walls are 47.2%, 41.9%, and 51.7%, respectively, with corresponding thermal exergy efficiencies of 0.59%, 0.49%, and 0.63%. The TC and TC-PV Trombe walls achieve purification efficiencies of 57.0% and 53.0% and purification exergy efficiencies of 2.53% and 2.42%, respectively. The TC-PV Trombe wall has electrical and electrical exergy efficiencies of 16.0% and 12.84%, respectively. System structure optimization analysis indicates that the system achieves the best exergy efficiency when the solar irradiation is 400 W/m² and the air channel thickness is 0.05 m. Additionally, the purification exergy efficiency increases with higher formaldehyde concentrations, while thermal, purification, and electric exergy efficiencies all increase with greater PV coverage. Exergy loss analysis reveals that the TC layer and heat-absorbing plate are major sources of loss. Therefore, developing catalytic materials with high absorptivity and high catalytic activity could enhance the system’s exergy efficiency.

Traditional rooftop greenhouses offer a promising solution for urban vegetable supply but have the disadvantages of overheating during the daytime and supercooling during the nighttime. To address these issues, a novel solar greenhouse system using nanofluid spectral splitting and phase change materials (NSS-PCMs) was developed. In this study, a 75-day thermal environment test experiment was conducted on the novel solar greenhouse, and the growth status and nutrient composition of three typical plants were evaluated. By optimizing the greenhouse structure parameters through the model, over 80% of 300–800 nm wavelengths for vegetable photosynthesis were transmitted to the greenhouse, while the remaining spectrum was used for heat storage to maintain warmth during nighttime. The novel solar greenhouse reduced daytime temperatures by 5.2 °C and increased nighttime temperatures by 6.9 °C, reaching a maximum thermal efficiency of 53.4% compared to traditional greenhouses. The 75-day temperature detection showed that optimal temperature ranges were maintained for approximately 60 days, both during daytime and nighttime, with an 80% assurance rate. The growth rates of three vegetables in the novel solar greenhouse improved by 55%, 35%, and 40%, and the nutrient composition doubled compared to the control group.

A Trombe wall is a widely applied heating system that has a single function. An interesting thing is that both the solar heat and UV light received by a Trombe wall have an air sterilization effect. Here, the air sterilization and thermal performances of a Trombe wall in different cities were investigated based on an established heat and mass transfer model. The main results were as follows: (1) UV dose accumulation and high temperature were the most important factors that affect the UV and thermal sterilization performance, respectively. The Trombe wall had the thermal characteristics of high accumulation of UV doses in the morning and afternoon and a high temperature level at noon, which was a good match with the UV and thermal sterilization process. (2) A typical sterilization process in a Trombe wall was divided into three areas: the UV inactivation area, UV and thermal inactivation area and UV inactivation area. (3) The weather conditions played an important role in the sterilization performance. UV sterilization was dominant in cloudy weather, and thermal sterilization was dominant in sunny weather. (4) In Nanjing, Shanghai, Xining and Guangzhou, the average daily clean air volumes in heating months were 39.4, 33.5, 32.2 and 39.8 m³/m², respectively. (5) When the wall height increased from 1.5 m to 3.5 m, the average daily clean air volume in heating months increased from 31.7 to 43.6 m³/m².