The Mesh Network

Each unit carries a Wi-Fi hotspot plus a LoRa long-range mesh radio — 8 W average, 190 Wh/day, $151 including its share of PV and battery. Wi-Fi serves the household and its neighbors; LoRa stitches units into a camp-wide mesh with no towers, no SIM cards, and no dependence on carrier coverage or its costs. The first job is boring and decisive: telemetry. In a 10,000-unit deployment, the operator sees which units are down, which batteries are aging, which chlorinator cells need service — the difference between a maintainable fleet and a field of dead hardware, which is how most camp technology actually dies. Camp-wide alerts and distribution announcements ride the same channel, and during epidemics it is the trusted information channel against rumor.

Sensing pairs the TDS/turbidity electronics with DPD chlorine-residual strips and the 35 °C incubator pocket (warmed by electronics waste heat) for overnight coliform presence/absence tests — $46 of instruments that let households verify their own storage hygiene.

Aggregated over the mesh, household test results become a live water-quality map of the settlement. The map then grows a market layer: any water vendor who joins lists their point with its location, its live price, and a verified-safe badge fed by the same instruments. Price visibility routes households to value and disciplines shortage gouging without an administrator setting prices; the badge is the recruitment tool — the Kisumu kiosk owners who bought chlorination hardware with their own money once it won them customers are the demonstrated behavior this scales. Joining vendors get demand routing, chlorine-as-a-service refills at table-salt prices, and a recorded quality-and-price history that works as a business credential with agencies. Latrine operators join the same way: a verified: clean, lit, open badge that routes users and earns after dark.

Fire. Dense camps burn catastrophically — the 2021 Cox's Bazar fire destroyed some 10,000 shelters. SolarHearth attacks the root cause (flameless cooking) and the mesh turns $3 smoke/heat sensors on every unit into a camp-wide early-warning grid: cluster sirens, fire location on the map for responders, negligible energy.

Diarrheal disease. Households report cases with one button on the unit (or a phone short-code); the map overlays case clusters on the chlorine residual and coliform data it already carries. Clustered failures plus rising cases are exactly the early-warning signature agencies want, days before clinic data shows it. Reporting is aggregated by block, never displayed per household. For cholera specifically the claim stays honest — anomaly detection, not diagnosis (Vibrio identification stays with clinic labs) — but the response is built in: cells surge to outbreak dosing and produce 0.2–0.5% surface disinfectant on demand, and cluster kitchens stock oral rehydration solution mixed with verified-safe water.

Theft protection closes the loop from chapter 1: every PV module is network-registered and geofenced, MPPTs accept only registered serials, and a panel that cannot be quietly resold is a panel not worth stealing.

A network that maps water quality, illness reports, and commerce across a refugee camp is holding data about a population with acute reasons to fear surveillance. The design rules are therefore structural, not policy: health reporting aggregates at block level and is never displayed per household; location precision degrades to the cluster for anything tied to a person; vendor listings are opt-in and vendor-controlled; and the mesh carries no identity registry — units, not people, have addresses. Data that would endanger residents if seized must not exist in the system in seizable form. This page states the requirement; a deployment must budget the security engineering to honor it.