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Type 3 (charge rate controlled) Solar Engines
The SE "cutting edge"

Type 3 solar engine designs are charge curve differentiated (i.e., they trigger when the charge rate of the storage capacitor slows down). While theoretically the most efficient, no designs of this type existed until a number were created in just the past few months. This type of solar engine is based on the idea that the solar engine should trigger as soon as the charge-curve slope falls below a certain value (so the "differentiating" is required). If things are done correctly, the resulting trigger point corresponds to the point at which the capacitor "tops off" because the solarcell has done nearly all the charging it can. In bright light that may mean near 3.5V, or 1.2V in dim light. In any case, it should be (at least in theory) the optimum in triggering.

To date I've only seen two type 3 designs presented (and have yet to build either):

  • T3SE
    Wilf Rigter's entrant in the "Type 3 SE sweepstakes."

  • Tritium
    Ben Hitchcock's design.

Note that the T3SE and Tritium are, strictly speaking, actually quasi-type 3 solar engines. Both these designs trigger on charge current, rather than rate-of-change of charge current.

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Page author: Eric Seale
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