What are hotspots in solar modules?

Hotspots arise from cell defects or shading. Individual cells heat up locally to over 150°C and can cause fire damage. Detection via drone thermography (IEC 62446-3).

How does thermal runaway occur in battery storage?

Thermal runaway is an uncontrolled exothermic chain reaction in Li-ion cells from approx. 130°C (NMC). Safety concepts per VDE-AR-E 2510-50 and NFPA 855 prevent propagation to adjacent cells.

Why do battery storage systems lose capacity?

Capacity degradation occurs through calendar and cyclic aging: 2–3% per year. Factors: depth of discharge (DoD), temperature, and C-rate. Assessment via independent state-of-health tests.

How dangerous are arcs in PV systems?

DC arcs at loose connections reach over 3,000°C — a common cause of fire in PV systems. Detection via Arc-Fault Circuit Interrupter (AFCI) per UL 1699B.

Case Studies: PV and BESS Assessments

Praxisbeispiel

01

Yield Assessment

Yield Loss of a 320 kWp Rooftop System – Root Cause Analysis and Assessment

The operator of a commercial rooftop PV system identified an underperformance of approx. 18% compared to the yield forecast over two years of operation. The insurer commissioned an independent expert assessment.

Result: Through IV curve measurement, thermography, and string analysis, defective bypass diodes, faulty MC4 connectors, and suboptimal string wiring were identified as causes. The yield loss was quantified at 87,400 kWh p.a.

DIN EN 62446 IEC 61215 320 kWp

Praxisbeispiel

21

Insolvency Proceedings / Portfolio

Insolvency Proceedings Involving a PV Portfolio of More Than 120 MWp

Expert support in insolvency proceedings covering a portfolio at three stages: project rights under development, projects under construction and PV systems in operation.

Result: Each stage was assessed separately, as project rights, construction sites and operating assets are judged by different standards. The findings served as the basis for realization in the proceedings.

Insolvency Proceedings Project Rights 120 MWp

Praxisbeispiel

20

Feasibility Study

Feasibility Study for a 1.8 MWp Large-Scale PV Project on Industrial Roofs

Assessment of PV layout on 5 commercial roofs: structural analysis, orientation, grid connection, economic viability, and regulatory framework (EEG, tenant electricity model).

Result: 3 roofs immediately suitable (1.2 MWp), 1 after reinforcement (0.4 MWp), 1 unsuitable (asbestos). IRR: 7.8% with self-consumption, 5.2% with full feed-in. Tenant electricity model recommended for 2 buildings.

EEG 2023 Tenant electricity 1,8 MWp

Praxisbeispiel

08

Valuation / Market Value

Valuation of a 180 kWp PV System in a Property Transaction

Determination of the current market value of the roof-integrated PV system (year of construction 2016, EEG remuneration) for buyers and financiers, including remaining useful life projection.

Result: Income approach considering technical degradation and remaining EEG remuneration period. Market value: EUR 187,000 (book value: EUR 124,000). Remaining useful life: 17 years.

Income approach EEG remuneration 180 kWp

Praxisbeispiel

10

Self-Consumption Optimization

Self-Consumption Optimization with Storage Integration for Commercial Operation

Economic viability analysis of various storage configurations for an existing 120 kWp PV system at a medium-sized commercial enterprise.

📚 Scientific basis: Battery Revenue Stacking →

→ Study: System Utility of Large-Scale Batteries

Result: 60 kWh storage as optimal sizing. Self-consumption rate increased from 42% to 71%. Payback: 8.4 years. Peak shaving potential: 35 kW.

Load profile analysis Storage simulation 120 kWp / 60 kWh

Praxisbeispiel

22

Tenant Electricity / Concept and Implementation

Tenant Electricity Project with 150 kWp on 10 Buildings

Design of a tenant electricity model for ten multi-family buildings with a combined 150 kWp. Electricity from the rooftops is supplied to the tenants on site, with the remainder covered by grid supply. The metering concept defines how generation, consumption of each apartment and grid supply are measured and billed. It is coordinated with the grid operator. The rollout of IoT metering equipment enables remote meter reading. During construction supervision, the installation of the PV systems and the metering equipment was monitored.

Result: Concept, metering concept, IoT rollout and construction from a single source. As the meters are read remotely, tenant billing works without manual meter reading.

Tenant Electricity Metering Concept 150 kWp

Praxisbeispiel

02

Fire Cause Investigation

Fire Cause Investigation on a PV System on an Industrial Building

Following a smoldering fire in the junction box area of a PV module, the expert assessor was commissioned by the building insurer for root cause analysis and damage evaluation.

Result: Microscopic examination and arc analysis revealed a serial arc at a poorly crimped cell connection. The damage was documented per VdS 3145 and quantified at EUR 145,000.

VdS 3145 IEC 61730 Arc analysis

Praxisbeispiel

03

Drone-Based IR Thermography

Drone-Based Thermography of a 4.2 MWp Solar Park

As part of a technical due diligence, a full-area IR thermography was conducted using a calibrated thermal imaging camera mounted on a drone.

Result: Of 12,600 modules, 247 showed thermal anomalies (1.96%). Of these, 18 modules with critical hotspots (>30 K overtemperature), 89 with substring failures, and 140 with minor cell anomalies. Claim value: EUR 62,000.

IEC 62446-3 4,2 MWp 12,600 modules

Praxisbeispiel

04

Battery Storage Assessment

Premature Capacity Loss of a 30 kWh Lithium-Ion Storage System

A commercial enterprise reported a capacity loss of 38% after 3 years of operation. The manufacturer denied the defect and attributed it to improper operating conditions.

📚 Scientific basis: Stationary Battery Storage – Market Development and Long-Term Measurements →

→ Study: Changing Battery Chemistries and Critical Minerals

Result: Through capacity testing per VDE-AR-E 2510-50, BMS log data analysis, and cell impedance measurement, a manufacturing defect (inhomogeneous cell chemistry) was verified. Warranty claim confirmed.

VDE-AR-E 2510-50 BMS analysis 30 kWh

Praxisbeispiel

05

Court Reports

Court Expert Report: Defect Assessment of a 98 kWp PV System

The regional court commissioned an expert assessment to evaluate alleged installation defects. The matters in dispute were module mounting, cable routing, and DC disconnect arrangement.

Result: Of 14 reported defects, 9 were classified as standards-relevant (DIN VDE 0100-712), 3 as cosmetic defects, and 2 as unfounded. Defect remediation costs: EUR 34,200 net. Diminished value: 12%.

DIN VDE 0100-712 §404 ZPO 98 kWp

Praxisbeispiel

06

Electroluminescence Examination

Electroluminescence Examination of Defective Solar Modules After Hail Damage

Following severe hail damage, 480 modules were examined using a mobile electroluminescence camera. Objective: differentiation between wear-related degradation and hail-induced cell fractures.

Result: 67 modules with hail-induced cell fractures (star-shaped), 23 with pre-existing micro-cracks, 12 with PID-related degradation. Insurance damage: EUR 89,500.

IEC 60904-13 PID analysis 480 modules

Praxisbeispiel

07

VdS Inspection per Clause 3602

VdS Inspection of Electrical Systems in a Production Hall per SK 3602

Recurring inspection of the entire electrical installation per VdS 3602, including findings report per VdS 2229. Scope: main distribution board, 14 sub-distribution boards, 3 machine groups.

Result: Findings report with 42 defects: 6 Category A (immediate danger), 18 Category B, 18 Category C. Re-measurement after defect remediation with clearance.

VdS 3602 VdS 2229 DIN VDE 0100-600

Praxisbeispiel

09

Overvoltage Damage

Overvoltage Damage from Lightning on PV System and Building Installation

An indirect lightning strike caused damage to inverters and building installation. The insurer commissioned a damage assessment of the claimed EUR 78,000.

Result: Evidence through ALDIS data and damage pattern. Missing surge protection Type 2 (SPD) as contributing cause. Settled damage: EUR 52,300 less deduction for betterment.

DIN EN 62305 VDE 0185-305 SPD Typ 2

Praxisbeispiel

11

Shading Assessment

Shading Assessment with 3D Horizon Analysis in Neighborhood Dispute

Following construction of a new building: measurement-based analysis of the shading situation before and after development, commissioned by the court.

Result: Through SunEye horizon analysis and 3D simulation: additional yield loss of 8.2% (1,640 kWh/a). Capitalized diminished value over remaining term: EUR 14,800.

3D simulation SunEye Monitoring data

Praxisbeispiel

12

Storage Safety Assessment

Thermal Runaway – Safety Assessment for Utility-Scale Storage in Commercial Property

Safety assessment of a 200 kWh storage system following a thermal runaway incident in a comparable system. Cell chemistry, BMS, ventilation, and structural fire protection measures were evaluated.

📚 Scientific basis: Thermal Runaway Propagation in BESS →

→ Study: Fire Safety of Li-Ion Batteries

→ Study: Gas Emissions from Li-Ion Thermal Runaway

Result: Deficiencies in exhaust gas routing and missing propagation barriers identified. Action plan with 8 retrofit items. After implementation: re-assessment with positive result.

VDE-AR-E 2510-50 UL 9540A 200 kWh

Praxisbeispiel

13

Grid Analysis & Power Quality (EMC)

Grid Analysis and Voltage Quality Measurement in an Industrial Facility

Recurring machine failures due to suspected harmonic distortion. 7-day grid analysis at the point of common coupling with a 250 kWp PV system.

Result: THD-U of 12.4% (limit DIN EN 50160: 8%). Main causes: 5th, 7th, and 11th harmonic. Recommendation: active harmonic filter. After implementation: THD-U < 4%.

DIN EN 50160 DIN EN 61000-2-2 7-day measurement

Praxisbeispiel

14

Lightning Protection & Grounding System

Lightning Protection Inspection and Grounding System Assessment per DIN EN 62305

Inspection of the lightning protection system of a logistics center with rooftop PV system: external/internal lightning protection, grounding resistances, and equipotential bonding.

Result: Grounding resistance: 2.4 Ω (standards-compliant). Missing separation distances at 4 locations. Equipotential bonding bar in main distribution board missing. Remediation initiated and accepted.

DIN EN 62305-3 VDE 0185-305 Grounding measurement

Praxisbeispiel

15

DGUV Regulation 3 – Inspection

DGUV Regulation 3 – Inspection of Fixed Installations and Equipment

Recurring inspection of all fixed installations and 340 portable appliances of a production facility with 220 employees.

Result: 14 pieces of equipment immediately decommissioned (insulation faults). 28 defects in fixed installations. Standards-compliant inspection documentation prepared for the professional association.

DGUV Regulation 3 DIN VDE 0105-100 340 pieces of equipment

Praxisbeispiel

16

Arc Flash Analysis

Arc Flash Analysis in a 20 kV Medium-Voltage Switchgear

Root cause investigation following an arc flash event with multi-hour production downtime. Evaluation of protective measures.

Result: Creepage distance undercut due to contamination. Arc duration 340 ms. Recommendation: retrofit arc detection system. Damage amount: EUR 280,000 incl. production downtime.

DIN VDE 0101 IEC 62271-200 20 kV

Praxisbeispiel

17

Glare Assessment (Glint & Glare)

Glare Assessment for an 8 MWp Ground-Mounted PV System Near Transport Infrastructure

Permitting procedure: investigation of potential glare effects on road traffic and residential buildings across all times of day and seasons.

Result: No glare at road level. Temporary glare on a residential building (max. 28 min/day in December). Recommendation: anti-reflective coating on southern module rows. Permit granted.

Glint & Glare 3D-Reflexion 8 MWp

Praxisbeispiel

18

Construction Quality Assurance

Construction-Accompanying Quality Assurance of a 2.5 MWp Large-Scale PV System

Independent monitoring of the installation across 6 site inspections: mounting, cabling, inverters, and commissioning.

Result: Insufficient roof load reserves in 3 areas – structural remediation initiated. At commissioning: 4 of 22 strings with incorrect polarity. Acceptance report per DIN EN 62446-1 prepared.

DIN EN 62446-1 Technical review 2,5 MWp

Praxisbeispiel

19

Insulation Fault Detection

Systematic Insulation Fault Location on a PV Generator with 840 Modules

Wiederkehrende Isolationsfehler (Riso < 1 MΩ) mit Wechselrichterabschaltung. Installateur konnte Fehlerquelle nicht lokalisieren.

Result: Fault located in module with water-ingressed junction box. 3 additional modules with Riso in borderline range (delamination). Module replacement and connector repair carried out.

IEC 62446 Riso measurement 280 kWp

Case Studies from Our Assessment Practice

Yield Loss of a 320 kWp Rooftop System – Root Cause Analysis and Assessment

Insolvency Proceedings Involving a PV Portfolio of More Than 120 MWp

Feasibility Study for a 1.8 MWp Large-Scale PV Project on Industrial Roofs

Valuation of a 180 kWp PV System in a Property Transaction

Self-Consumption Optimization with Storage Integration for Commercial Operation

Tenant Electricity Project with 150 kWp on 10 Buildings

Fire Cause Investigation on a PV System on an Industrial Building

Drone-Based Thermography of a 4.2 MWp Solar Park

Premature Capacity Loss of a 30 kWh Lithium-Ion Storage System

Court Expert Report: Defect Assessment of a 98 kWp PV System

Electroluminescence Examination of Defective Solar Modules After Hail Damage

VdS Inspection of Electrical Systems in a Production Hall per SK 3602

Overvoltage Damage from Lightning on PV System and Building Installation

Shading Assessment with 3D Horizon Analysis in Neighborhood Dispute

Thermal Runaway – Safety Assessment for Utility-Scale Storage in Commercial Property

Grid Analysis and Voltage Quality Measurement in an Industrial Facility

Lightning Protection Inspection and Grounding System Assessment per DIN EN 62305

DGUV Regulation 3 – Inspection of Fixed Installations and Equipment

Arc Flash Analysis in a 20 kV Medium-Voltage Switchgear

Glare Assessment for an 8 MWp Ground-Mounted PV System Near Transport Infrastructure

Construction-Accompanying Quality Assurance of a 2.5 MWp Large-Scale PV System

Systematic Insulation Fault Location on a PV Generator with 840 Modules

Normative Foundations

Similar Case?

Common Damage Patterns in PV Systems and Battery Storage

Further Information