VM Collector Efficiency

Due to the tubular construction of VM tubes, they are strong enough to carry the weight of an average person and the impact of golf size hail storms.

VM collectors are tested by European and North American authorities. The test results of Institute SPF at the Hochschul Rapperswil of Switzerland leads to following thermal performance equations (Test Report No. 264, August 1997):

Efficiency of Collector = 0.84 - 2.02 (Tm-Ta)/G - 0.0046G[(Tm-Ta)/G]**2

Measured Thermal Performance (4286 bytes)

Tests conducted by Florida Solar Energy Center of USA (FSEC Solar Collector Test Report No. 97005, May 1998) is in very good agreement with the performance test reported by SPF Institute:

Efficiency of Collector = 0.82 - 2.19 (Tm-Ta)/G
Efficiency of Collector = 0.81 - 1.23 (Tm-Ta)/G - 0.0122G[(Tm-Ta)/G]**2

Tm = mean collector temperature, (Toutlet+Tinlet)/2 [C]
Ta  = ambient air temperature [C]
G   = Solar irradiance [W/sq m]

These test results are shown in the following graph:
(G= 800 W/sq m)

Thermo Technologies endorses the  following measured efficiency curve of TMA 600 tubes and the VM collector system:

Thermal Performance Curve Measured by Thermomax (3895 bytes)

VM evacuated solar collectors are specifically designed for all-year-round operation in regions with cold winters and also locations with high humidity such as the tropics. The following chart shows a practical approach to find collector tube efficiency for various insolation levels.

Collector Efficiency.gif (6930 bytes)

Collector Temperature of 60 degrees C (140 F) with an ambient temperature of 20 degrees C  (68 F) and insolation of 800 W/m gives a collector efficiency of 69%.


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