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In this paper, a simple model is proposed for predicting the thermal energy requirements of greenhouses in Europe. The model estimates the annual heating requirements and the maximum required heating power, along with the corresponding heating and zero-energy operating periods. It is based on the greenhouse technical data (the overall heat loss coefficient, cover transmission, sensible absorbance), the cultivation conditions (temperature range), and the meteorological data (solar radiation and ambient temperature) according to the site characteristics (longitude and latitude). The model results can be obtained using a hand calculator. The model results are compared with those of a detailed model simulating a greenhouse's thermal performance and they agreed with real data from the literature. Moreover, a model sensitivity analysis revealed the effect of various factors on the greenhouse's energy requirements. The results proved that the most significant factor affecting heating requirements, the maximum heating power, and heating periods is the latitude of the greenhouse site, whereas zero-energy periods are primarily influenced by the plant cultivation temperature range and then by the latitude. According to our findings, in lower latitudes (40 to 50 degrees), heating requirements range from 250 to 430 kWh/m2/y, whereas, in higher latitudes (50 to 60 degrees), heating needs range from 430 to 650 kWh/m2/y. [ABSTRACT FROM AUTHOR]

Exposure to polycyclic aromatic hydrocarbons (PAHs) may lead to adverse health risks. To understand the potential sources and carcinogenic risks of PAHs in Tangshan, 40 PM 2.5 samples were collected for analysis of eighteen PM 2.5 -bound PAHs during non-heating period and heating period. The results display a significant variation. The median concentration of ∑ 18 PAHs during the heating period (282 ng/m 3 ) was higher than during the non-heating period (185 ng/m 3 ). Especially, the median concentration of Benzopyrene (BaP) during the heating period (61.6 ng/m 3 ) was 16.9-fold that during the non-heating period (3.64 ng/m 3 ). It exceeded BaP annual average limit of China (1 ng/m 3 ). Diagnostic ratios (DRs) and principal component analysis (PCA) both indicated that vehicle emissions and coal and biomass combustion were the dominant contributors of PAHs pollution in Tangshan. The incremental lifetime cancer risk (ILCR) of three age groups (children, teenagers, and adults) ranged from 2.56 × 10 -6 to 5.26 × 10 -5 during the entire sampling periods. The 95% risk values of adults exceeded 10 -4 during the heating periods, indicating a potential health risk from PAHs., Competing Interests: The authors declare no conflict of interest.