analysis of the influences of solar radiation and façade glazing ...

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3.5 Optimization of a solar domestic hot water system 94 Eabs [kWh/period] 400 350 300 250 200 150 100 50 0 annual summer winter 0 10 20 30 40 50 60 70 80 90 Collector angle [deg] Fig. 3.45: Dependence of solar collectors heat transfer energy for cold and warm periods in the year on a collector tilt angle. The results indicate that if we change the collector tilt angle from 25° to 60°, the absorbed solar energy varies only about 10 % in the period of a year. However, applying the extreme angles 0° (a horizontal position) and 90° (a vertical position) leads to a significant reduction of the DHW system’s efficiency. The energy conversion decreases to 70 % of the maximal value in optimal panel position for the angle 0° and for an angle of 90° the same reduction reaches about 50 %. As the simulation results show, the best solar collector tilt angle is 70° for the cold period and 35° for the summer time. If the tilt angel is fixed, the best thermal performance is obtained at 45°. It should be noted that the solar installation will heat water in the winter period but the solar conversion will be about ten times lower than those during the summer time. A simple calculation method for estimating the solar collector efficiency ηSC by EN12975-2 (2007) is described in chapter 1.2.4 of the current work. The value of ηSC varies strongly during the day due to changes in the solar radiation flux as shown in Fig. 3.46.
3.5 Optimization of a solar domestic hot water system 95 η SC [-] 0,60 0,50 0,40 0,30 0,20 0,10 0,00 08/12 01:00:00 08/12 07:00:00 08/12 13:00:00 08/12 19:00:00 08/13 01:00:00 08/13 07:00:00 08/13 13:00:00 Fig. 3.46: Efficiency fluctuation, which is caused by solar radiation vary throughout a day. 08/13 19:00:00 08/14 01:00:00 Another factor associated with the thermal performance of solar panels is the heat loss to ambient air caused by convection, conduction and infrared radiation. This disadvantageous effect can be characterized by a1 and a2 loss coefficients in efficiency Eq. (1.11). VITOSOL 300-T SP3, assumed in simulations, is specified by a1 = 0.9156 W/m 2 K and a2 = 0.003 W/m 2 K 2 . The lowest value of performance variables a1 and a2, as in the current case, leads to the higher efficiency of the DHW system. Fluctuation in a heat loss of the solar panels, presented in Fig. 3.47, strongly depends on ambient air temperature and lasts for over half a year. 08/14 07:00:00 08/14 13:00:00 08/14 19:00:00 08/15 01:00:00 08/15 07:00:00 08/15 13:00:00 08/15 19:00:00 08/16 01:00:00 08/16 07:00:00 08/16 13:00:00 08/16 19:00:00
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ANALYSIS OF THE INFLUENCES OF SOLAR
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than the inner air temperature. It
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4.1 SUMMARY .......................
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Subscripts σ - Stefan-Boltzmann co
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1.1 Introduction 9 Another problem,
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1.2 Background and literature revie
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2.1 Building energy simulation soft
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Page 53 and 54: 3.1 Building description 53 Fig. 3.
Page 55 and 56: 3.1 Building description 55 All int
Page 57 and 58: 3.1 Building description 57 Case B5
Page 59 and 60: 3.1 Building description 59 Of cour
Page 61 and 62: 3.1 Building description 61 Outside
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Page 69 and 70: 3.2 Selection of the optimal glazin
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Page 99 and 100: 4.1 Summary 99 4 Summary and conclu
Page 101 and 102: 4.2 Comments and conclusions 101 So
Page 103 and 104: 4.3 Future research 103 of the annu
Page 105 and 106: References 105 Beausoleil-Morrison,
Page 107 and 108: References 107 Hendron, R., et al.
Page 109 and 110: References 109 Rees, S. and Haves,
Page 111 and 112: References 111 Yohanis, Y.G., et al
Page 113 and 114: Appendix 1 113 Fig. A1.1 VASATI 2.0
Page 123 and 124: Appendix 2 123 !-Generator IDFEdito
Page 125 and 126: Appendix 2 125 0.035, !- Conductivi
Page 127 and 128: Appendix 2 127 , !- Zone Inside Con
Page 129 and 130: Appendix 2 129 Discrete; !- Numeric
Page 131 and 132: Appendix 2 131 Fraction, !- Schedul
Page 133 and 134: Appendix 2 133 Air Conditioner:Wind
Page 135 and 136: Appendix 2 135 , !- Sensible Heat F
Page 137 and 138: Appendix 2 137 281, !- Lighting Lev
Page 139 and 140: Appendix 2 139 OG2 InfilTRATION, !-
Page 141 and 142: Appendix 2 141 OG3, !- Zone Name 16
Page 143 and 144: Appendix 2 143 0.004, !- Zone Heati
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Appendix 2 145 Zone15WindACAirInlet
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Appendix 2 147 0, !- Maximum Flow R
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Appendix 2 149 Zone16WindACOAMixer,
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Appendix 2 151 Zone 9 Outlet Node;
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Appendix 2 153 Stand Alone ERV 16,
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Appendix 2 155 ZoneHVAC:WindowAirCo
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Appendix 2 157 ZoneHVAC:Baseboard:C
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Appendix 2 159 Zone Control Type Sc
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Appendix 2 161 WindACPLFFPLR, !- Pa
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Appendix 2 163 Stand Alone ERV Supp
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Appendix 2 165 0.03001, !- Maximum
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Appendix 2 167 0.81, !- Sensible Ef
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Appendix 2 169 !- == ALL OBJECTS IN
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