Status quo 449 h — Sentinel keeps 487 more hours of Tier 1 and 2 care.
36,159 L burned against 39,000 L — twice the care on less fuel.
ICU, theatres and cold chain never lose power. Status quo: 12 interruptions.
Against a fixed-rule inverter on the identical solar, battery and generator.
On 22 September 2024 insurgents brought down tower 372 on the Gombe–Damaturu–Maiduguri 330 kV line; the city was cut off until 31 October. In December 2022 two Maiduguri hospitals sat dark for days with working generators and empty tanks. This replay runs that 39-day outage, on NASA POWER weather measured for those exact dates, for an illustrative 250-bed referral hospital — four controllers, identical loads, deliveries and failures. Simulation, not measured hospital data.
Replay controls
Every change re-runs 4 × 4,032 steps
Tank starts 60% full; deliveries every 3.5 days. The generator is the same 400 kW set for the hybrid strategies; the status quo gets a larger set sized to the full facility (no PV/battery).
Hour-by-hour service through the outage
Each cell is one hour; the worst quarter-hour sets its colour. Red = life-critical Tier-1 circuits (ICU, theatres, cold chain, oxygen, ED) without power.
Diesel in the tank
Litres on site, sampled every 2 h. Saw-teeth are deliveries; a line on the floor is a dark hospital.
Critical-service hours (Tier 1+2) vs weekly diesel supply
Same outage, same weather, 9 supply levels × 4 strategies (36 full replays). Where fuel is plentiful every option converges; where the supply chain binds, the controller decides who stays powered.
X-axis: litres delivered per week in two drops (tank 10,000 L). The same hospital burns ≈3,360 L/week in a normal year on this feeder (full-year simulation); a line outage multiplies the need roughly fourfold. Honest trade-off: below ~5,000 L/week Sentinel deliberately sacrifices Tier-2 hours to keep Tier-1 (ICU, theatres, cold chain) on — switch to “Tier 1” to see it.
Why Sentinel decided what it decided
Fuel-runway governor log (first entries) — every decision states the arithmetic behind it.
Field channel — works on any phone
Sentinel's alerts as single-segment SMS (≤160 GSM-7 chars) and a USSD status menu for the duty engineer. Generated from the replay; nothing is sent from the prototype.
MedGrid Sentinel ISLAND Gen:RUN Batt 70% (T1 3.9h) Diesel 3015L T1 80/80kW 1 Alerts 2 Runway 3 Ack
How the brief's metrics are computed: critical-service hours = islanded hours in which ≥ 99.5 % of Tier-1 and Tier-2 demand was served (a ≤ 90 s generator transfer break is counted separately as an interruption); diesel litres avoided = status-quo litres − Sentinel litres over the same window. Loads are an illustrative 250-bed referral profile; weather is NASA POWER measured hourly data for Maiduguri (22 Sep – 31 Oct 2024); prices: diesel ₦1,950/L (Oct-2026 retail range). Simulation, not field-measured performance.