Hi mistermj,
I agree, PV is not the optimal solution for the application at hand, i.e., powering Mars rovers, but to call the technology a failure in space ignores decades of success that made the satellite age possible, not to mention myriad other apps.
On earth? Let's be real. I agree wholeheartedly that, to date, pv's use by utilities for base load generation is a joke, as is the case when it's used to supplement large installations, such as Internet data centers, where I tend to view it as an opportunistic, gratuitous solution, at best. What price PR, and its growth agent, social corporate responsibility?
But let's not ignore it's success, and the promise it holds, for billions of inhabitants on the planet whose abodes do not align with current (or even planned) gross national grid transmission and distribution networks. In such situations a small local collector that feeds a battery (and perhaps an inverter) can make the difference between basic electrical needs, including a single light bulb; communicating with the rest if the globe, and utter darkness, both literally and figuratively.
As for the dust storms on Mars, good point. The problem has been recognized for decades, as the abstract below, taken from an IEEE paper written in 1990 demonstrates:
Paper: Design considerations for Mars photovoltaic systems: tinyurl.com
ABSTRACT
Considerations for operation of a photovoltaic power system on Mars are discussed with reference to Viking Lander data. The average solar insolation on Mars is 590 W/m2, which is reduced yet further by atmospheric dust. Of major concern are dust storms, which have been observed to occur on local as well as on global scales, and their effect on solar array output. While atmospheric opacity may rise to values ranging from three to nine, depending on storm severity, there is still an appreciable large diffuse illumination, even at high opacities so that photovoltaic operation is still possible. If the power system is to continue to generate power even on high-optical-opacity (i.e. dusty atmosphere) days, it is important that the photovoltaic system be designed to collect diffuse irradiance as well as direct. Energy storage will be required for operation during the night. Temperature and wind provide additional considerations for array design.
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I've not researched this further, but I would imagine that ultrasonics might be used here to dislodge, or prevent, buildup when dust is detected. Then again, doing so would detract from the existing power budget. Tradeoffs.
A similar problem has existed with the design of free space optical systems following snowfalls, which most vendors now address with heating elements to melt the snow.
FAC
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