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Solar Panel Performance
Compare Saving form Boston, MA - Milwaukee, WI and Las Vegas, NV
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Simulated Performance of Solar Domestic Water Heater Systems
The table below 35 lists the annual solar fraction for various domestic water heating
loads in three different U.S. cities (Boston, MA; Milwaukee, WI; and Las Vegas, NV).
In all cases, the following system assumptions were made:
Closed-loop antifreeze system with heat exchanger effectiveness = 0.50
Collectors face directly south
Collector slope = approximately equal to local latitude
Setpoint temperature for domestic hot water = 120ºF
Cold water temperature = typical of location
Annual solar fractions are given for four daily hot water loads (left column) and
three solar collector area/storage tank volume scenarios (top row).
As would be expected, the larger collector arrays and correspondingly larger storage tanks yield higher solar
heating fractions in all locations. In looking at these results, one might assume the best system is the one
supplying the highest percentage of the load. From a pure energy conservation standpoint, this may be
true. However, the economic viability of the system is a different matter. Systems that supply very high solar
heating fractions may not provide returns on investment as high as systems supplying lesser amounts of the
load. The only way to know for sure is through detailed economic analysis of competing system options. Most
solar system simulation software can also perform an economic analysis of the system.
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Boston, MA.
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40 ft2/60 gal.
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80 ft2/120 gal.
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120 ft2/180 gal.
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40 gal/day
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72%
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91%
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96%
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60 gal/day
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57%
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85%
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92%
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80 gal/day
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48%
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77%
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89%
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100 gal/day
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41%
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69%
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84%
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Milwaukee, WI.
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40 ft2/60 gal.
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80 ft2/120 gal.
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120 ft2/180 gal.
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40 gal/day
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67%
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88%
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94%
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60 gal/day
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54%
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83%
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90%
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80 gal/day
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45%
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74%
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86%
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100 gal/day
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38%
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65%
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81%
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Las Vegas, NV.
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40 ft2/60 gal.
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80 ft2/120 gal.
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120 ft2/180 gal.
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40 gal/day
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94%
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99%
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100%
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60 gal/day
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88%
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98%
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100%
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80 gal/day
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77%
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76%
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99%
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100 gal/day
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69%
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94%
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98%
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