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. The absorber is a key component of a flat plate collector: in the context of an evacuated panel, absorber design poses a number of technical challenges.A flooded panel absorber has been designed for use in evacuated flat plate solar collectors. The aim was to obtain higher efficiency, in a low out-gassing material, than would be possible using a conventional serpentine tube design.Initial plans for a micro-channel plate were modified when optimisation analysis showed that a flooded panel could achieve as good performance with easier fabrication. The absorber plate is made from hydroformed stainless steel sheets welded together and features an array of through-holes for the glass supporting pillars with the square panel sub-divided into two rectangles connected in series for ease of fabrication and better flow distribution. The coolant flow was modelled in Star-CCM+. FEM simulations based on tensile test data informed the choice of sheet thickness and weld radius around the holes to withstand the 1 bar pressure differential.Hydroforming is an effective method for producing sheet metal components, e.g. plates for heat exchangers or solar absorbers. As a thermal engineering experimental technique, the tooling is significantly cheaper than press tools since the mould does not need a matching die. In a research context, the ability to form plates in-house and explore profile and tooling options at low cost is very useful and might find application in other fields such as experimental heat exchangers.A hydroforming facility was built using 85 mm thick steel sheet and a 25 MPa hydraulic pump. This proved highly effective at forming 0.7 mm stainless steel sheet. A total of eight absorbers were fabricated and successfully leak tested using helium. Two variants were made: one kind for use in enclosures with a metallic rear tray, the other for enclosures with glass on both sides. The collector efficiency factor is estimated to be 3% higher than for commercial tube-on-plate designs.
|Journal||Applied Thermal Engineering|
|Early online date||13 Apr 2018|
|Publication status||E-pub ahead of print - 13 Apr 2018|
Bibliographical noteReference text: References
 Duerr, U., Welding thermal solar absorbers, Industrial Laser Solutions, vol.21, No. 9, Sept 2006, pp12-14 from https://www.industrial-lasers.com/articles/2006/09/welding-thermal-solar-absorbers.html downloaded 30/1/18
 Rüttimann, C., Dürr, U., Moalem, A. and Priehs, M., "Reliable laser micro-welding of copper", Proc. SPIE 7920, Laser Applications in Microelectronic and Optoelectronic Manufacturing (LAMOM) XVI, 792007 (February 21, 2011); http://spie.org/Publications/Proceedings/Paper/10.1117/12.875033 downloaded 30/1/2018
 ETSAP, Solar Heat for Industrial Processes (IEA-ETSAP and IRENA Technology Brief E21), 2015, http://www.irena.org/DocumentDownloads/Publications/IRENA_ETSAP_Tech_Brief_E21_Solar_Heat_I ndustrial_2015.pdf downloaded 30/1/2018
 Moss, R.W., Henshall, P., Arya, F., Shire, G.S.F., Hyde, T. and Eames. P.C. Performance and operational effectiveness of evacuated flat plate solar collectors compared with conventional thermal, PVT and PV panels. Applied Energy, 2018.
 Moss, R.W., Shire, G.S.F., Henshall, P., Eames, P.C., Arya, F. and Hyde, T., Optimal passage size for solar collector micro-channel and tube-on-plate absorbers. Solar Energy, Vol. 153, Sept 2017, pp. 718-731 doi: 10.1016/j.solener.2017.05.030
 Benvenuti, C. and Ruzinov, V., The SRB evacuated flat solar panel, Proceedings of ECOS 2010, pp2-429 to 434. http://infoscience.epfl.ch/record/165003/files/Ecos2010-book2-printing.pdf?version=5 downloaded 30/1/2018
 TVP Solar, MT-30 datasheet, http://www.tvpsolar.com/files/pagine/1508933997_MT-Power Datasheet (v4 SK).pdf downloaded 30/1/2018
 Henshall, P., Eames, P., Arya, F., Hyde, T., Moss, R. and Shire, S. Constant temperature induced stresses in evacuated enclosures for high performance flat plate solar thermal collectors, Solar Energy, Vol. 127, 2016, pp250-261
 Sgobba, S., Materials for high vacuum technology: an overview, CERN (2006)
https://cds.cern.ch/record/983744/files/p117.pdf downloaded 30/1/18
 Klein, A., Oreski, G. and Resch-Fauster, K., Applicability of technical biopolymers as absorber materials in solar thermal collectors, Solar Energy 153 (2017) 276–288
 Koyatsu, Y., Miki, H. and Watanabe, F., Measurements of outgassing rate from copper and copper alloy chambers, Vacuum, Vol. 47, No 6-8, pp709-711, 1996
 Bacher, J-P., Benvenuti, C., Chiggiato, P., Reinert, M-P., Sgobba, S. and Brass, A-M., Thermal desorption study of selected austenitic stainless steels, Journal of Vacuum Science & Technology A 21, 167 (2003); doi: 10.1116/1.1527953
 Coyne, D., LIGO Vacuum Compatible Materials List (LIGO project internal working note) April 2004, https://dcc.ligo.org/LIGO-E960050/public downloaded 30/1/18
 Leisch, M., Hydrogen outgassing of stainless steel our present knowledge, 1st Vacuum Symposium, February 2010, www.vacuum-uk.org/pdfs/vs1/vs1/Leisch.pdf downloaded 30/1/18
 Duffie, J.A. and Beckman, A., Solar Engineering of Thermal Processes, Wiley, 2013.
 Spyrou, L.A. and Aravas, N., Thermomechanical modelling of laser spot welded solar absorbers, ASME Journal of Manufacturing Science and Engineering, Feb 2015, Vol 137, 011016-1:15
 Kuryntsev, S.V., Morushkin, A.E. and Gilmutdinov, A. Kh. Fiber laser welding of austenitic steel and commercially pure copper butt joint. Optics and Lasers in Engineering 90 (2017) 101–109
 Moharana, B.R., Sahu, S.K., Sahoo, S.K. and Bathe, R., Experimental investigation on mechanical and microstructural properties of AISI 304 to Cu joints by CO2 laser, Engineering Science and Technology, an International Journal 19 (2016) 684–690,
 Klimpel, A., Górka, J., Czupryński, A., Kik, T. and Dadak, R. (2012) Research into GTA automatic soft soldering technology for solar energy collector components, Welding International, 26:2, 112-117, http://www.tandfonline.com/doi/full/10.1080/09507116.2010.540854 downloaded 11/8/17
 Klimpel, A., Kruczek, T., Lisiecki, A. and Janicki, D. (2013) Experimental analysis of heat conditions of the laser braze welding process of copper foil absorber tube for solar collector elements, Welding International, 27:6, 434-440, http://www.tandfonline.com/doi/full/10.1080/09507116.2011.606140 downloaded 11/8/17
 Rybaulin, V.M., Skorobatyuk, A.V. and Mikitas, A.V. (2016) Brazing of absorbers of planar solar heating collectors produced from materials of the Cu–CuZn system, Welding International, 30:2, 142-149, http://www.tandfonline.com/doi/full/10.1080/09507116.2015.1036534 downloaded 11/8/17
 Mirski, Z., Granat, K., Drzeniek, H., Piwowarczyk, T. and Wojdat, T. (2013) Soldering of aluminium with copper, Welding International, 27:3, 190-195,
http://www.tandfonline.com/doi/full/10.1080/09507116.2011.600029 downloaded 11/8/17.
 Koholé, Y.W. and Tchuen, G. (2017) Comparative study of three thermosyphon solar water heaters made of flat-plate collectors with different absorber configurations, International Journal of Sustainable Energy, 36:5, 430-449,
 Tsilingiris, P.T., Heat transfer analysis of low thermal conductivity solar energy absorbers. Applied Thermal Engineering 20 (2000) 1297-1314
 Koç, M., Mahabunphachai, S. and Billur, E., Forming characteristics of austenitic stainless steel sheet alloys under warm hydroforming conditions, International Journal of Advanced Manufacturing Technology (2011), https://link.springer.com/article/10.1007/s00170-011-3169-x downloaded 11/8/17.
 Oyinlola, M.A., Shire, G.S.F. and Moss, R.W., The significance of scaling effects in a solar absorber plate with micro-channels, Applied Thermal Engineering 90 (2015) 499-508
 Hermann, M., Development of a bionic solar collector with aluminium roll-bond absorber, BIONICOL Final Report, http://www.bionicol.eu/ downloaded 18/6/14.
 Sun, X., Wu, J., Dai, Y. and Wang, R., Experimental study on roll-bond collector/evaporator with optimized channel used in direct expansion solar assisted heat pump water heating system. Applied Thermal Engineering 66 (2014) pp 571-579
 Do Ango, M., Medale, M. and Abid, C., Optimization of the design of a polymer flat plate solar collector, Solar Energy 87 (2013) 64-75
 Kim, S., Kissick, J., Spence, S. and Boyle, C., Design, analysis and performance of a polymer–carbon nanotubes based economic solar collector, Solar Energy 134 (2016) 251–263
 Verhaege, G., Achieving aerospace-standard porosity levels when welding thin and thick section aluminium using fibre-delivered lasers, EngD Thesis, University of Warwick, 2008,
http://go.warwick.ac.uk/wrap/50485 downloaded 30/1/18.
[32a,b] Arya, F., Moss, R.W., Hyde, T., Shire, S., Henshall, P. and Eames, P.C., Vacuum enclosures for solar thermal panels Part 1: Fabrication and hot-box testing; Part 2: Transient testing with an uncooled absorber plate. (forthcoming)
 Marciniak, Z., Duncan, J.L. and Hu, S.J., Mechanics of Sheet Metal Forming, Butterworth-Heinemann, 2nd edition (2002), Chapter 11 (Hydroforming), ISBN 0 7506 5300 0
 Lei, L-P., Kim, Jeong, Kang, S-J. and Kang, B-S, Rigid–plastic finite element analysis of hydroforming process and its applications, Journal of Materials Processing Technology 139 (2003) 187–194, https://www.sciencedirect.com/science/article/pii/S0924013603002188
 Tondeur, D, Fan, Y., Commenge, J-M and Luo, L., 2011. Uniform flows in rectangular lattice networks, Chemical Engineering Science 66 (2011) 5301-5312
 Young, W.C and Budynas, R.G., Roark’s Formulas for Stress and Strain, McGraw-Hill, Seventh edition,2002
 Stanley torque calculator http://www.stanleyengineeredfastening.com/brands/spiralock/informationcenter/torque-calculator
 Moss, R.W., Henshall, P., Arya, F., Shire, G.S.F., Eames. P.C. and Hyde, T. Simulator testing of evacuated flat plate solar collectors for industrial heat and building integration. Solar Energy, Vol. 164, April 2018,pp109-118, https://doi.org/10.1016/j.solener.2018.02.004
- Solar collector
- flow distribution