Abstract
The concept of an evacuated flat plate (EFP) collector was proposed over 40 years ago but, despite its professed advantages, very few manufacturers have developed commercial versions. This situation suggests both technical difficulties in manufacturing a competitively-priced sealed for life panel and a lack of awareness of the benefits of such panels.This paper demonstrates an evacuated flat plate simulation that closely models experimental efficiency measurements. Having established the validity of the model, it compares published data for a commercial EFP collector with predictions for an optimal design to investigate whether any further efficiency improvement might be possible. The optimised design is then evaluated against alternative solar energy devices by modelling a number of possible applications. These comparisons should inform choices about solar options for delivering heat: EFP collectors are well-suited to some of these applications.Evacuated flat plate collectors are a possible alternative to concentrating collectors for Organic Rankine Cycle power generation. The annual output for all the modelled collectors was found to be a quadratic function of delivery temperature: this enabled a novel optimisation of ORC source temperature. Predictions for concentrating and non-concentrating ORC plant are compared with a PV/thermal alternative. The ORC output is significantly less than a PV panel would achieve; applications needing both heat and power are better served by PVT panels. This is an original and novel result.
Highlights
The concept of an evacuated flat plate (EFP) collector was proposed over 40 years ago but, despite its professed advantages, very few manufacturers have developed commercial versions
This paper demonstrates an evacuated flat plate simulation that closely models experimental efficiency measurements
At G = 1000 W/m2 the optimised evacuated panel has higher efficiency than other designs up to TM = 245 °C: beyond this point the parabolic trough collector is more efficient, albeit only in clear conditions when beam radiation is available. At this high radiation level and TM = 60 °C an optimised evacuated flat plate could collect 13% more heat than a conventional flat panel or 32% more than the same area of evacuated tubes; this increases to approximately 50% relative to either flat panel or evacuated tube at TM = 100 °C.The PVT panel in Fig. 7 is a simulation described as “state of the art” by Matuska et al [45] that predicted the performance that should be possible from a single-glazed flat panel collector with PV cells bonded to the absorber surface
Summary
Non-concentrating solar thermal collectors for low temperature applications such as domestic solar hot water (DSHW) conventionally adopt either a flat plate (FP) or evacuated tube (ET) format. CHP DSHW EFP ET FP ORC PTC PV PVD PVT RTD TVP combined heat and power domestic solar hot water evacuated flat plate collector evacuated tube collector flat plate collector (non-evacuated) Organic Rankine cycle parabolic trough collector photo-voltaic panel physical vapour deposition photo-voltaic/thermal panel resistance temperature detector evacuated flat plate collector by TVP Solar combine the high fill factor, ease of cleaning and visual aesthetics of FP collectors with the low heat loss coefficient of ET collectors. They consist of a flat absorber contained within an evacuated enclosure with a top glass cover. Of an improved design, have demonstrated the advantages for DSHW heating under typical UK irradiance conditions and assessed the potential use of an organic Rankine cycle for power generation
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