Thermal Enhancement of PV Modules

10.4.1 Real Operating Cell Temperatures Under Tropical Conditions

To know more about real operating behavior under tropical climatic conditions, specifically about cell temperatures and the output power (at MPP), a module (M55 from SSI) was tested at the PV Labs of the UFRJ in Rio de Janeiro (22°54’ S; 43°13’ W), Brazil during an equinox (9/22/1994). The components of irradiance (horizontal global, direct and diffuse) during that day have been recorded, as shown in Figure 10.14.

Подпись: Д-Д direct irradiance Э-О diffuse irradiance 0-0 global irradance

Fig. 10.14. Horizontal global, direct, and diffuse irradiance at Equinox (9/22/94) in Rio de Janeiro, Brazil (22°54’S; 43°13’W).

Figure 10.15 gives the measured temperature values at an M55 module during that day at almost no-wind conditions. Elevation angle of the module plane was 23°, facing North. The maximum power point was tracked manually by a variable resistor using a digital ammeter, a digital voltmeter and a calculator. Thermal and electrical measurements could be carried out just after 6:45 a. m., due to access-restrictions of the site, and not later than 4:45 p. m., due to partly shadowing of the generator by a neighboring building. The measured electrical energy output of the module was 300 Wh, while a constant cell temperature of 25°C, as requested in the Standard-Test – Conditions (STC), would have caused a 12% higher yield (see Figure 10.16).

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Fig. 10.15. Measured ambient-, and module temperatures at a M55-module during 9/22/1994 in Rio de Janeiro, Brazil, at no-wind conditions.

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Fig. 10.16. Measured electrical power output under real conditions in comparison to the theoretical power output at a constant cell temperature of 25°C (“Maximum – Power-Point" conditions for both curves).

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