We Hit Full Solar Loop — in Winter. CSSGH Is Now a Tiny, Autonomous Micro-Farm.

TL;DR: Our Closet-Size Smart GreenHouse (CSSGH) ran continuously for ~46 days through Belgian early-winter, then we shut it down by choice to avoid freeze damage — with the battery still at 78%. During that run it grew lettuce, cabbage, basil, and kept a 45 L aquatic biome (goldfish, shrimp, snails, Elodea & floaters) healthy, with an average service load of ~1 hour/month.

What we builtA closet-footprint aquaponics stack:

• Ground: 45 L tank (goldfish + shrimp + snails + Elodea + floaters)

• Mid: Papyrus phyto-filter (daytime solar recirculation)

• Upper: Two tray levels for lettuce, cabbage, basil (expanded clay)

• Energy: 200 W foldable PV + CTECHi GT200-3 (~320 Wh)

• Control: Day = solar-only flow; Night = 2.4 W USB pump on intermittent schedule; one LED removed to minimize parasitic draw; smart top-up from a 24–48 h dechlorinated “arrosoir”

How we proved “full loop”

• 06 Oct → 21 Nov continuous operation (≈ 46.4 days).

• Mid-run “OFF” was a crashed USB switch, not a flat battery; a quick reboot restored normal operation.

• We winterized on 21 Nov 16:10 for freeze protection — the power station read 78% SoC.

• In other words, solar IN ≥ system OUT even with short days and cold nights.

👉 Addendum report (ready for your dossiers): on demand

Why it matters

• It’s tiny, affordable (~€750 PoC) and reproducible.

• It produces edible greens while hosting a living aquatic biome — a genuine circular micro-farm.

• It’s ultra-low maintenance: outside of harvests, we averaged ~1 hour/month (quick checks, filter/media swish, trimming).

• It validates the investor thesis: a ~300–320 Wh pack + 200 W PV + smart intermittency is enough for winter-capable autonomy at this scale.

A note on maintenanceFrom our logs: once stabilized, routine interactions were limited to (a) weekly glance at SoC, (b) occasional hose/pump check, (c) plant trimming and outer-leaf harvests. Excluding harvest time, that’s ~15 min/week = ~1 h/month on average. (Spring setup & fall winterization are separate, one-off tasks.)

The castThanks to Coco,Stéphane , Emma , and Jérémy . Academic interest & context: Prof. Mari Sandell (University of Helsinki) and Janne Saariko (LUKE, Finland).

What’s next

• Publish a replication guide (+ materials passport)

• Add a watchdog auto-reboot for the USB switch

• Release an Eco+ / Eco-Pro parts list (recycled HDPE, silicone/TPE, LFP pack)

• Run a school/lab cohort to compare yields (CSSGH vs soil control)

Want one? We can install a CSSGH PoC, train your team, or help you run a replication study.