power-assessment

name: power-assessment description: Perform detailed Electrical Power System (EPS) sizing and analysis. Use this skill to model solar array degradation, battery depth-of-discharge, power bus architecture, and energy balance. Trigger this for "solar array sizing," "battery life," "EPS architecture," "power budget," or "energy balance."

Power Assessment Skill (EPS)

Read CONVENTIONS.md at the repo root before proceeding.

This skill performs detailed Electrical Power System analysis. It provides sized solar arrays, batteries, and bus architecture — going beyond the summary-level power budget in systems-engineering-assessment.

Before You Begin

Ask the user (if not already known):

1. What is the primary power source? (Solar, RTG, fuel cells, primary batteries — driven by mission type and distance from Sun)
2. What is the orbit? (Eclipse duration from mission-analysis-specialist is a critical input)
3. What is the mission lifetime? (Drives degradation and cycle-life calculations)
4. What is the bus voltage? (28V regulated is common; ask if there's a heritage constraint)
5. What design phase?

Applicable Phases

• Primary: Phase A (first-order sizing), Phase B (detailed energy balance)
• Supporting: Phase C (power profile verification), Phase D (solar array deployment test planning)

Core Analysis Workflows

1. Solar Array Sizing (BOL/EOL)

• Inputs: Required power ($P_{req}$), solar constant ($1361\ W/m^2$ at 1 AU), cell efficiency ($\eta$), sun incidence angle ($\theta$), degradation rate ($F_d$), mission life ($L$), packing factor.
• For non-Earth missions: Scale solar flux by $1/d^2$ from Sun. Mars: ~589 W/m², Jupiter: ~50 W/m².
• EOL factor: $L_d = (1 - F_d)^L$
• Required area: $A = P_{req} / (S \cdot \eta \cdot \cos\theta \cdot I_d \cdot L_d)$
• If solar is not viable (e.g., outer planets, permanent shadow): Recommend RTG or nuclear and flag for user decision.

2. Battery & Energy Storage

• Inputs: Eclipse power ($P_{ecl}$), eclipse duration ($t_{ecl}$ from mission-analysis-specialist), DOD, battery efficiency, transmission efficiency.
• Sizing: $E_{req} = (P_{ecl} \cdot t_{ecl}) / (\eta_{bat} \cdot \eta_{trans} \cdot DOD)$
• DOD policy:
  • LEO (high cycle count): 20-40% DOD for Li-ion
  • GEO (low cycle count): up to 80% DOD
  • Lunar night (~14 days): batteries alone are typically insufficient — flag this
• Thermal: Battery charge typically 0°C to 30°C — coordinate with thermal-assessment.

3. Power Distribution & Architecture

• Bus regulation: Regulated (28V typical) vs. unregulated (battery voltage varies).
• Peak power tracking: MPPT vs. Direct Energy Transfer (DET).
• Harness losses: Typically < 2% voltage drop budget.

4. Alternative Power Sources

For missions where solar power is insufficient:

• RTG: ~120W per unit, multi-decade lifetime, ~4.8% efficiency. Subject to nuclear safety review.
• Fuel Cells: Short-duration high-power missions (e.g., crewed lunar sortie).
• Primary Batteries: Very short missions only (< days).

Output Format

1. Power Analysis Report (power_analysis.md):
   • Solar array: BOL/EOL power, required area, degradation assumptions
   • Battery: capacity (Wh/Ah), DOD, cycle life
   • 🟢 / 🟡 / 🔴 status
2. EPS Configuration (eps_config.csv): Solar area, battery Wh, bus voltage.

Reference Data

• Solar Flux: Earth/Moon ~1361 W/m², Mars ~589 W/m², Jupiter ~50 W/m²
• Li-ion energy density: 150-250 Wh/kg
• Solar cell efficiency: Triple-junction GaAs 28-32%, Silicon 15-20%, advanced multi-junction >35%

Interface

• Reads from: /requirements/, /analysis/mission-analysis-specialist/ (eclipse duration, solar distance), /analysis/thermal-assessment/ (battery temp limits)
• Writes to: /analysis/power-assessment/
• Consumed by: systems-engineering-assessment (power budget summary), propulsion-assessment (EP power availability), gnc-assessment (actuator power)