Abstract
A novel combined solar heating plant with flat plate collectors (FPC) and parabolic trough collectors (PTC) was constructed and put into operation in Taars, 30 km north of Aalborg, Denmark in August 2015. To assess the thermal performance of the solar heating plant, global radiation, direct normal irradiance (DNI) and total radiation on the tilted collector plane of the flat plate collector field were measured. To determine the accuracy of the measurements, the calculated solar radiations, including horizontal diffuse radiation, DNI and total tilted solar radiation with seven empirical models, were compared each month based on an hourly time step. In addition, the split of measured global radiation into diffuse and beam radiation based on a model developed by DTU (Technical University of Denmark) and the Reduced Reindl correlation model was investigated. A new method of combining empirical models, only based on measured global radiation, was proposed for estimating hourly total radiation on tilted surfaces. The results showed that the DTU model could be used to calculate diffuse radiation on the horizontal surface, and that the anisotropic models (Perez I and Perez II) were the most accurate for calculation of total radiation on tilted collector surfaces based only on global radiation under Danish climate conditions. The proposed method was used to determine reliable horizontal diffuse radiation, DNI and total tilted radiation with only the measurement of global radiation. Only a small difference compared to measured data, was found. The proposed method was cost-effective and needed fewer measurements to obtain reliable DNI and total radiation on the tilted plane. This method may be extended to other Nordic areas that have similar weather.
Highlights
Energy consumption in the building sector accounts for about 40% of society’s energy consumption in developed countries
The DTU model and RR models were used to calculate horizontal diffuse radiation based on measured global radiation
Model, developed for the plant in Denmark were analysed in this study using an hourly time step
Summary
Energy consumption in the building sector accounts for about 40% of society’s energy consumption in developed countries. Especially solar energy, for heating and cooling in the building sector is a promising way to reduce the fossil energy consumption of buildings [1,2]. Solar thermal energy is one of the most commercial renewable energies in the building sector [3,4]. Large solar heating plants connected to district heating networks have been of great success in Europe, especially in Denmark. Most large scale solar heating plants in Europe, even worldwide, are constructed in Denmark. Denmark is the first and the only country with a mature commercial market for solar district heating plants. By the end of 2016, more than 1.3 million m2 solar heating
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