Measurements of the angular distribution of diffuse irradiance

AbstractAdvanced solar resource assessment and forecasting is necessary for optimal solar energy utilization. In order to investigate the short-term resource variability, for instance caused by clouds it is necessary to investigate how clouds affect the solar irradiance, including the angular distribution of the solar irradiance. The investigation is part of the Danish contribution to the task 46 within the International Energy Agency and financed by the Danish Energy Agency. The investigation focuses on the distribution of the diffuse solar irradiance and is based on horizontal measurements of the solar irradiance from 8 different parts of the sky as well as horizontal measurements of the total beam and total diffuse irradiance

Calculated thermal performance of solar collectors based on measured weather data from 2001-2010

AbstractThis paper presents an investigation of the differences in modeled thermal performance of solar collectors when meteorological reference years are used as input and when mulit-year weather data are used as input.The investigation has shown that using the Danish reference year based on the period 1975-1990 will result in deviations of up to 39% compared with thermal performance calculated with multi-yearmeasured weather data. For the newer local reference years based on the period 2001-2010 the maximum deviation becomes 25%.The investigation further showed an increase in utilization with an increase in global radiation. This means that besides increasing the thermal performance with increasing the solar radiation, the utilization of the solar radiation also becomes better