Ulster University Logo

Simulator testing of evacuated flat plate solar collectors for industrial heatand building integration

Moss, Roger, Henshall, Paul, Arya, Farid, Shire, Stan, Eames, Philip and Hyde, Trevor (2018) Simulator testing of evacuated flat plate solar collectors for industrial heatand building integration. Solar Energy, 164 . pp. 109-118. [Journal article]

[img] Text (PDF) - Published Version
Indefinitely restricted to Repository staff only.

1MB

URL: https://www.sciencedirect.com/science/article/pii/S0038092X1830121X

DOI: https://doi.org/10.1016/j.solener.2018.02.004

Abstract

The concept of an evacuated flat plate collector was proposed over 40 years ago but, despite its professed advantages, very few manufacturers have developed commercial versions. This paper demonstrates the reduction in heat loss coefficient and increase in efficiency resulting from evacuating a flat plate collector: it is hoped that these results will stimulate interest in the concept. Evacuated tubes are now mass-produced in large numbers; evacuated flat plate collectors could in principle replace these tubes if the technical difficulties in creating extended metal-glass seals can be overcome. The experimental experiences described here should indicate targets for future research.Two different designs of evacuated flat plate solar thermal collector, each with a 0.5×0.5m flooded panel black chrome plated absorber, were tested under a solar simulator. The cover glasses were supported by an array of 6mm diameter pillars. Inlet and outlet temperatures were monitored via PT100 RTDs and glass temperatures were measured using thermocouples. Inlet temperature was controlled by a fluid circulator connected to a header tank with a Coriolis mass flow meter to measure fluid flow rate. Testing was conducted indoors with and without the use of a fan to cool the top cover glass. The test conditions spanned the range 200<G<1000 W/m2, 0 ⩽ TM ⩽ 52 °C.Evacuating the enclosure reduced the measured heat loss coefficient by 3.7 W/m2 K: this was a close match to predictions and corresponds to an increase in aperture efficiency from 0.3 to 0.6 at TM/G = 0.06 m K/W2 . The poor efficiency under non-evacuated conditions was due to the black chrome absorber coating being less selective than commercial panel coatings. The solder seals were developed from experience with vacuum glazing but the increased gap led to reliability issues. A vacuum pump maintained the enclosures under a high vacuum (<0.1 Pa) during testing. The enclosure based on a thin rear metal tray proved to be more effectively sealed than the more rigid enclosure with glass on both sides: the latter developed leaks as the front to rear temperature difference increased. The biggest challenge in the manufacture of evacuated flat plate collectors is to ensure a long-term hermetic seal such that no pumping is required.

Item Type:Journal article
Keywords:Evacuated, Flat plate, Solar, Collector, Absorber, Efficiency
Faculties and Schools:Faculty of Art, Design and the Built Environment
Faculty of Art, Design and the Built Environment > School of the Built Environment
Research Institutes and Groups:Built Environment Research Institute > Centre for Sustainable Technologies (CST)
Built Environment Research Institute
ID Code:39779
Deposited By: Dr Farid Arya
Deposited On:20 Mar 2018 12:09
Last Modified:20 Mar 2018 12:09

Repository Staff Only: item control page