科研之友
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摘要
Three luminous efficacy models namely Perez model, Muneer-Kinghorn model, and Littlefair model have been evaluated against measured solar illuminance and solar irradiance at New Delhi. Both these quantities are measured simultaneously, every half an hour, on a horizontal surface, in clear sky as well as intermittent sky. Among three models, Perez model has been found to perform best, with minimum mean bias error and minimum root mean square error. Experimental results also reveal that diffuse luminous efficacy has higher values as compared to global luminous efficacy and beam luminous efficacy. Further, Perez model has been used to assess daylight availability in summer, winter, and monsoon seasons at six Indian stations: New Delhi, Jodhpur, Pune, Kolkata, Shillong, and Leh, covering all climatic conditions in India. This model is used to obtain hourly values of solar illuminance for both global and diffuse components, in a typical meteorological year for each of the six stations. Analysis also shows that Indian climates have clear or intermittent skies for 60%-80% of day-time in a typical year, revealing immense potential for daylight exploitation for energy conservation. Solar global illuminance level assumes the highest value in summer months of April and May, whereas it becomes lowest in winter month of December. In monsoon season, solar illuminance is around 60-65 klx. It is also found that cumulative frequencies for global illuminance increases linearly with solar illuminance, in the range of 0-100 klx. Cumulative frequency for diffuse illuminance increases exponentially with solar illuminance, in the range of 0-60 klx.
- 出版日期2013-11
