Off-grid power doctrine — Demory farm site (Campbell County)¶
Purpose¶
Give canonical planning guidance for SITE_FARM at Demory (Campbell County) when the business plan treats the production parcel as off-grid-first: solar + battery as the default electrical architecture, without inventing array kW, battery Ah, or NEC details — those require local engineering after measured loads .
Doctrine package (full map: tiers, field nodes, WAN deps, degraded modes, stop rules): Off-grid systems doctrine package — Demory.
Sources (provenance): Off-grid power, field RF, and optional WAN — source index (NREL modules 5–6, Victron Wiring Unlimited, captures).
Paired pages: Power domains and battery-backed infrastructure tiers — Demory, Mesh and field networking strategy — off-grid Demory farm, Off-grid farm execution topology — Demory (Mermaid), Connectivity strategy — Claxton & Demory (WAN secondary to local survivability at farm ).
Architectural stance (policy)¶
| Stance | Meaning |
|---|---|
| Off-grid-first | Utility tie is not assumed for core farm loads ; design for standalone PV + storage + optional genset per NREL framing (DC/AC/hybrid coupling choices ) . |
| Solar + battery default | Battery is the energy buffer for night , cloud , and surge loads ; sizing is TBD . |
| Networking is a load | Always-on radios , gateways , and Starlink CPE draw real Wh/day — budget them with other infrastructure , not as “ free ” . |
What we do not claim here: optimal string voltage , BMS SKU , grounding solution — cite NEC / AHJ with a PE .
What should be powered continuously (policy)¶
| Category | Examples (illustrative) | Notes |
|---|---|---|
| Safety / welfare interlocks | Pump controller logic that prevents dry run ; gate fail-safe solenoids where required | Must fail safe without cloud ; may still need local power discipline . |
| Core field gateway “spine” | One MQTT / edge node that aggregates sensors | Define “ minimum uptime ” vs duty-cycled repeaters (see mesh strategy ) . |
| Minimal comms for operator | One mesh or LTE path for Tier-1 alerts (policy ) | Not every sensor — the smallest set that meets coverage matrix . |
What should be duty-cycled or event-driven¶
| Category | Examples | Notes |
|---|---|---|
| Mesh repeaters / Meshtastic nodes | Remote hills / fence line | Power-saving modes , light sleep , solar + small local battery per Meshtastic power docs (source index) . |
| Cameras / NVR | Motion or scheduled recording | Continuous 4K everywhere is a luxury load — match to pilot phase . |
| Starlink / optional WAN | Powered only when egress or admin window needed (policy ) | Treat as sheddable during deep SOC events unless you explicitly classify it as critical (Off-grid degraded modes) . |
| Wi‑Fi HaLow / AP radios | High airtime when no traffic | Design for sleep / beacon interval tradeoffs — see comparison page . |
Solar + battery implications of always-on networking¶
- NREL module 6 emphasizes O&M discipline (inspection , cleaning , fault response ) — telemetry that reduces truck rolls still adds constant draw if always on .
- Always-on IP radios + edge compute compete with water pumps , cold chain , and winter hay handling for the same battery SOC — document priority loads before scaling RF fleet .
- Placeholder :
P_NET_ALWAYS_W= ___ W (meter ) ;E_NET_DAY= ___ Wh/day .
Maintenance burden (operator-real)¶
| Area | Burden |
|---|---|
| Battery / BMS | Cell balance , temp , contactor health — NREL O&M themes . |
| PV array | Soiling , snow , vegetation shading new growth . |
| Inverter / charger | Firmware , wiring torque checks (Victron discipline ) . |
| Field network gear | Firmware churn on mesh ; physical theft / lightning at 120 ac . |
Pilot vs scale¶
| Phase | Power expectation |
|---|---|
| Phase 0–1 (pilot ) | One proven DC bus segment + one gateway + minimal always-on RF ; measure before second array string or second battery bank . |
| Scale | Redundant PV , genset policy , load shedding bus — only after G1 / water / fence gates per business plan . |