Surgery and Healing in the Developing World - Dartmouth-Hitchcock

Establishing Electrical Power in Remote Facilities for Health Care
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Figure 7. Current vs voltage
curves for high and low illumination
levels. The system is
designed to operate near the
maximum power point regardless
of illumination level.
no damage to the module, and it is completely reversible when the module cools
down. But it should be avoided to optimize performance. With this in mind, it is
important that modules not be mounted flush against a roof when deployed in a
tropical location. Even if the ambient air is only 25˚C, the module can easily reach
60˚C due to absorption of the infrared part of the spectrum by the module back
plane (usually rigid polyvinyl fluoride) and the roofing material. For a roof-mounted
array, the installer will always allow at least 10 cm of ventilation space between the
array and the roof. More frequently, an array will be mounted on angle iron or steel
pipes that are fixed in concrete supports (Fig. 8). This assures stability in wind storms
and allows for plenty of ventilation that will keep the array cool.
Figure 8. Modules at a clinic in Sundarbans, West Bengal, India, are fixed to a frame and
anchored in concrete. (Photo by J. Welch, courtesy NREL/PIX.)
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