A sun-tracking, two-axis motorized mirror redirects daylight (and a modest amount of heat) into a north-facing window that would otherwise receive none, claimed roughly equivalent gain to a same-sized south-facing window, per the source, not independently verified. Genuinely more complex and fragile than anything else in this catalog's daylighting entries: custom electronics (photoresistor sensor board, H-bridge motor driver, hand-soldered), two motorized axes, implied ongoing calibration. Flagged honestly as a poor fit for this project's repairability bar, catalogued as an available option for a specific site condition (a useful north-facing room with no other daylighting fix), not a general recommendation.
Note: Cost, carbon and footprint are rated against the other options for this same need, not in absolute terms.
A north-facing window/room lacking other daylighting options, with space for the mirror assembly
No sizing or quantities: how much a technique yields, and how much a household needs, both depend on the build and the people, so the catalogue compares options rather than dimensioning them. It carries no bill of materials and no build sequence, and it is written for an oceanic, clay-soil climate (Normandy, France). Regulatory notes are indicative and need confirming locally.