Fleet Energy Depot Architecture

This page defines the physical and logical architecture of a Fleet Energy Depot — an integrated energy node that manages utility interconnection, grid-forming storage, operations, and software control for electrified fleets.

FED architecture stack

This section describes the physical and software architecture that distinguishes a Fleet Energy Depot from a conventional charging site.

LEVEL 1 — GRID & INTERCONNECTION LAYER

Where the FED touches the utility

• Utility service entrance
• Medium-voltage (MV) switchgear
• Substation or pad-mount transformer
• Interconnection protection relays
• Revenue-grade metering
• Grid monitoring sensors
• Utility SCADA interface (when required)

Purpose

• Defines maximum import/export capacity
• Establishes interconnection constraints
• Enables islanding and reconnection logic

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LEVEL 2 — MICROGRID CONTROL LAYER

The brain of the site

• Microgrid controller (physical industrial controller)
• Energy management system (EMS)
• Load forecasting engine
• State-of-charge optimization logic
• Grid import/export scheduler
• Black-start coordination logic
• Islanding and resynchronization control

Key point
This is not cloud software alone. It is a hardened industrial control system running locally.

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LEVEL 3 — GRID-FORMING ENERGY LAYER

The most critical FED differentiator

• Grid-forming battery energy storage system (BESS)
• Bi-directional power conversion system (PCS)
• Inverter-based voltage and frequency control
• Synthetic inertia support
• Fault ride-through capability
• Black-start capability

Purpose

• Enables islanded operation
• Stabilizes weak grids
• Buffers fleet demand spikes
• Decouples charging from utility timing

Key point
This is what makes a FED microgrid-native.

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LEVEL 4 — ONSITE GENERATION (OPTIONAL BUT COMMON)

• Solar PV arrays (canopy or ground mount)
• Wind generation (site dependent)
• CHP / gas generators (transition or backup)
• Hydrogen or fuel-based generators (emerging)

Purpose

• Reduces grid dependence
• Supplies energy directly to BESS
• Improves resilience and autonomy

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LEVEL 5 — POWER DISTRIBUTION LAYER

• Low-voltage switchgear
• DC bus architecture (where deployed)
• AC distribution panels
• Protection devices and breakers
• Redundant feeders for critical loads

Purpose

• Routes power dynamically between assets
• Enables priority-based dispatch

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LEVEL 6 — VEHICLE ENERGY DELIVERY LAYER

• DC fast chargers (150–1000+ kW)
• Megawatt Charging System (MCS)
• Pantograph or overhead charging
• Robotic plug-in systems
• Wireless charging (limited use cases)

Key point
Important distinction: Chargers are peripherals — not the core system.

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LEVEL 7 — FLEET OPERATIONS LAYER

• Yard management system (YMS)
• Fleet management system (FMS)
• Vehicle scheduling software
• Dispatch coordination
• Duty-cycle optimization
• Vehicle availability tracking

Key point
This is where energy meets operations.

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LEVEL 8 — EDGE COMPUTE & DATA LAYER

• Industrial edge gateway
• Local compute node (x86 / ARM)
• Real-time telemetry processing
• Protocol translation (CAN, OCPP, Modbus, IEC 61850)
• Latency-critical decision logic

Purpose

• Operations cannot depend on cloud uptime
• Charging control loops must run locally

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LEVEL 9 — INDUSTRIAL INTERNET & CONNECTIVITY

• Private LTE / 5G
• Fiber backhaul
• Redundant WAN paths
• Secure VPN tunnels
• Time-sensitive networking (TSN)

Purpose

• Deterministic communications
• OTA reliability
• Fleet telemetry transport

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LEVEL 10 — SOFTWARE-DEFINED CONTROL PLANE

• Energy orchestration software
• Charger management system (CMS)
• BESS optimization software
• Grid services participation software
• Carbon and energy accounting
• Predictive maintenance analytics

Purpose

• Coordinates all physical assets

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LEVEL 11 — OTA & UPDATE INFRASTRUCTURE

• OTA update server (local or hybrid)
• Vehicle firmware update management
• Charger firmware updates
• BESS firmware updates
• Controller and inverter updates

Key point
Key insight: FEDs increasingly function as OTA hubs, not just power hubs.

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LEVEL 12 — SAFETY, COMPLIANCE & SECURITY

• Electrical safety systems
• Arc-flash protection
• Fire suppression (BESS-specific)
• Thermal monitoring
• Physical access control
• Cybersecurity segmentation (OT/IT)
• NERC / NFPA / UL / IEC compliance

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LEVEL 13 — PHYSICAL SITE & YARD SYSTEMS

• Energy Autonomy Yard (EAY) layout
• Charging islands
• Drive lanes and queue zones
• Vehicle staging zones
• Maintenance bays
• Autonomous navigation markers
• Weather hardening systems

Key point
This is where EAY lives — adjacent, not core.

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LEVEL 14 — EXTERNAL INTEGRATIONS

• Utility coordination platforms
• Market participation systems
• Fleet ERP
• CMMS
• Risk management platforms
• Compliance reporting systems

Key point
This is where monetization software connects.

Depot microgrids, storage, and on-site generation

Battery energy storage systems and local generation turn a grid-connected fleet charing depot into a flexible energy node. Properly sized, these assets can flatten peaks, reduce demand charges, and provide limited backup during outages.

Asset	Primary Role	Design Notes
Battery energy storage (BESS)	Peak shaving, load shifting, limited backup	Capacity sized to cover high-demand charging windows, not full-site autonomy.
Solar canopy or rooftop PV	Reduce net daytime load and provide shade	Generation profile rarely aligns perfectly with charging peaks; pairs well with BESS.
Backup generators or fuel cells	Support critical loads and limited fleet operations during outages	Runtime constrained by fuel logistics and permits; often targeted at priority vehicles.
Microgrid controller	Coordinate grid, BESS, PV, and backup resources	Interfaces with charger controls, EMS, and utility; critical for safe islanding.

Depot Topology and Throughput

The shape and layout of a depot determines how many vehicles can be turned around per hour and how resilient operations are to spikes, delays, and failures.

Key topology archetypes include:

• Linear charging corridors: high-density rows with easy in and out flow, well suited for robotaxis and delivery vehicles.
• Hub-and-spoke layouts: a central Fleet Energy Depot with satellite yards feeding dense urban zones.
• Block layouts with microgrid islands: solar canopies, BESS clusters, and charging lanes arranged around parking bays.
• Mixed-use energy campuses: charging, maintenance, cleaning, teleoperations, and data ingest at one integrated site.
• Heavy-duty megawatt charging zones: dedicated lanes for Class 7 and 8 tractors requiring megawatt-class charging.
• Multi-level depots: vertical structures in land-constrained cities that integrate charging, cleaning, and data offload across levels.

As fleets scale, depot design converges toward throughput metrics similar to airport terminal design: how many vehicles per hour can be safely processed with predictable timelines.

Fleet depot energy stack

The EV fleet depot energy stack links medium-voltage infrastructure, conversion, storage, and control systems into a single architecture.

Layer	Components	Notes
Grid interface	MV service, interconnect, protection relays	Defines maximum import capability and fault behavior.
Conversion and distribution	Transformers, switchgear, busway, rectifiers	Determines efficiency, expandability, and maintenance windows.
Storage and generation	BESS, PV, backup generators or fuel cells	Provides flexibility against tariffs, peaks, and outages.
Control and optimization	Microgrid controller, EMS, charger management	Coordinates dispatch, charge windows, and energy flows.

Charging Levels/Modes at Depots

Commercial depots support multiple charging modes, tuned to the EV fleet mix and duty cycles. Most sites evolve from simple AC overnight charging to mixed DC and megawatt-class systems as fleets scale.

Mode	Power Range	Best For	Notes
Depot AC (Level 2)	11–22 kW	Light-duty support vehicles, pool cars, some delivery vans	Overnight or long dwell; lowest hardware cost and grid impact.
DC fast (Level 3)	50–350 kW	Delivery vans, box trucks, shuttles, buses, robotaxis	Core workhorse for MD depots; supports shift changes and opportunity top-ups.
Megawatt-class (MCS)	750 kW to 1.2+ MW	Class 7–8 tractors, heavy industrial mobile assets	Enables fast turn for long-haul and high-duty HD fleets; drives MV and transformer sizing.
Battery swap	Varies	UAV fleets, eVTOL prototypes, specialized logistics	Moves energy handling off-vehicle; requires tight pack standardization and logistics.
Robotic charging	22–350 kW (LD/MD), 350 kW–1 MW (HD)	Robotaxis, AV delivery, automated yards, humanoid corridors	Automates plug-in; requires precise docking, sensing, and safety envelopes.

Mixed voltage and multi-sector depots

Most depots eventually support assets on different voltage classes. Planning for heterogeneous fleets up front avoids stranded chargers and rework.

Voltage Class	Typical Assets	Planning Notes
400 V	Legacy LD EVs, some MD vehicles, many robotics platforms	Good fit for AC and lower-power DC clusters; suitable for support and early fleets.
800 V	Next-generation MD/HD trucks, high-performance platforms	Enables higher sustained DC power; reduces dwell but increases hardware and insulation demands.
MCS-class HV	Class 7–8 tractors, heavy campus vehicles	Requires HV cabinets, liquid-cooled cables, and careful thermal design around pedestals.

Depot charging layouts

Inside the yard, charger placement and traffic flow have as much impact on throughput as nameplate power. Common depot charging layouts include:

• Linear rows — vehicles nose-in or back-in to fixed pedestals along fences or walls; simple cabling and wayfinding.
• Island chargers — chargers in the center of bays, allowing access from both sides and supporting mixed fleet sizes.
• Pull-through lanes — essential for tractors and trailers; reduce complex maneuvers and congestion.
• Dedicated HD alleys — separate lanes for MCS or high-power DC to isolate heavy vehicles and longer dwell.
• Robotics corridors — dense rows of low-power points for humanoids and AMRs, often indoors and tied closely to compute rooms.

Charging topologies must align with arrival patterns, yard constraints, and safety rules, not just peak kW requirements.

Fleet segments and duty cycles

Duty cycles drive both power level and dwell-time strategies. Depots with mixed fleets typically segment parking and charger types by use case.

Fleet Type	Typical Dwell Window	Charging Strategy
Robotaxis and ridehail	Short, frequent returns	Dense DC arrays; frequent top-ups; high charger utilization during peaks.
Urban and regional delivery	Overnight or clear shift breaks	Mix of AC and DC; predictable kWh per shift; strong fit for BESS load shaping.
Freight tractors	Mid-route and terminal dwell	MCS uplift at depots and corridor sites; turn-time targets dominate design.
Industrial yard equipment	Staging and shift overlaps	Moderate peak power, high concurrency; integration with plant loads and MV backbones.
UAVs and eVTOL	Rapid, high-intensity cycles	Pad-based charging or swap; power density per square meter is the main constraint.
Humanoids and AMRs	Continuous micro-charging	Low per-point power but very high density; charging tightly coupled to compute and workflow.

Autonomous/robotic fleet charging design

As fleets move toward autonomy, depots transition from driver-plugged charging to autonomous docking and robotic connectors. This changes both hardware and yard design.

• Automated parking and staging — vehicles navigate to assigned bays without drivers, relying on mapped lanes and fixed infrastructure.
• Robotic connectors — arms, underbody couplers, or movable pedestals align and connect without human intervention.
• Sensing and guidance — cameras, depth sensors, fiducial markers, and V2X support precise alignment and safety margins.
• Humanoid and AMR corridors — high-density, low-power docks integrated with local compute rooms for logs and OTA.
• Safety envelopes — clearly defined mixed zones where humans, vehicles, and robots coexist with speed and access limits.

In mature deployments, autonomous and robotic charging becomes a core design assumption rather than an optional upgrade.

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