J. Dragsted1*, J. Fan1 & S. Furbo1

1 Department of Civil Engineering, Technical University of Denmark, Brovej, Building 118, 2800 Kgs. Lyngby,

Denmark

Janne Dragsted, iaa@byg. dtu. dk

Abstract

Evacuated tubular solar collectors have the advantages that they are designed to utilize the solar radiation from all directions, and that the heat loss from the collectors is low. This makes them ideal for Artic regions. This paper presents a theoretical investigation of four Sunda Technology evacuated tubular solar collectors’ thermal performance in the Arctic. Different design parameters for the collectors are investigated in terms of the thermal performance. The investigation shown that with improvements of different design parameters it is possible to reach an increase of the thermal performance of up to 9 %.

Keywords: Evacuated tubular collectors, heat pipe principle, thermal performance, TRNSYS, Arctic regions

1. Introduction

In this paper different designs of four evacuated tubular solar collectors are investigated in order to maximize the thermal performance of the solar collectors especially with the Arctic regions in mind. In the Arctic the reflection from the snow plays an important role for the total available energy from sun. Due to the midnight sun, where the sun stays on the sky all 24 hours of the day, there is a need for a solar collector that can utilize solar radiation from all directions. The collectors in the investigation are therefore placed in such a way that they can utilize solar radiation from all directions. No shadows from the surroundings are assumed. The heat loss from the collectors also plays an important role since the average ambient temperature during periods with the collectors in operation is low, around 0°C.

The evacuated tubular solar collectors have a low heat loss because of the vacuum inside the tubes, making them favourable for the Arctic regions.

The four different evacuated tubular solar collectors investigated are Seido 5-8, Seido 1-8, Seido 10-20 curved and Seido 10-20 flat from the Chinese company Sunda Technology Ltd see Fig 1. Seido 5-8 and Seido 1-8 are collectors with 8 glass tubes where the radius of the tubes is 5 cm. The absorber in Seido 5-8 is a curved absorber and the absorber in Seido 1-8 is a flat absorber. Seido 10-20 curved and Seido

Fig 1. The four collectors from Sunda Technology Ltd.

10-20 flat are collectors with 20 tubes with a radius of 3.5 cm, where curved and flat refers to the design of the absorber. The locations used in the parametric analyse is Nuussuaq which is situated on the west coast of Greenland at latitude 70.4° and Sisimiut also situated on the west coast of Greenland at latitude 66.6°. For comparison reasons the location of Copenhagen, Denmark, is also used which is at latitude 55.3°. The thermal performances are calculated with different designs of the four solar collector types. The parameters which are investigated: The distance between the glass tubes, the design of the absorber, the radius of the glass tubes, and the transmittance-absorptance product. Further, the tilt and orientation of the collectors have been varied as well.