BESS 5 MWH Aux consumption

TECHNICAL REPORT

Auxiliary Consumption Assessment for 5 MWh Liquid-Cooled BESS Block

By Dr. Bhawani Singh Rathore

Global Renewable Energy Project Manager | BESS Specialist | Technical Consultant

1. Purpose of This Report

This report establishes a verified, globally benchmarked and lender-grade auxiliary consumption (AUX) assessment for a 5 MWh liquid-cooled Battery Energy Storage System (BESS) using an externally installed ~1.375 MVA PCS.
All values are validated against global OEM data from USA, Europe, Australia and China to ensure accuracy.

The objective is:

• To define AUX precisely

• To avoid double counting

• To provide climate-wise AUX values

• To ensure alignment with real OEM standards

2. Definition of Auxiliary Consumption (AUX)

AUX includes all parasitic electrical loads required to keep the BESS functional and safe.

AUX Includes – Inside Battery Container

✔ Liquid cooling system (chillers, pumps, fans)
✔ Heating system (anti-condensation, winter control)
✔ Humidifier (if provided by OEM)
✔ Internal air circulation

✔ BMS, rack controllers, sensors
✔ EMS / SCADA / data communication
✔ Fire detection & suppression supervisory loads
✔ Lighting & internal low-voltage panel power

AUX Includes – Outside Battery Container

✔ PCS cooling (air/liquid HVAC)
✔ PCS control electronics, PLC, HMI
✔ ACDB loads
✔ UPS charging & standby
✔ MV/LV panel heaters & control supply
✔ Auxiliary transformer load only (not its core loss)
✔ CCTV, router, networking, metering

3. What Is NOT Included in AUX

To avoid double counting, the following are excluded:

✘ PCS conversion losses (already in PCS efficiency)
✘ Transformer no-load (core) loss P₀
✘ Transformer load losses Pk
✘ Cable losses, harmonic losses
✘ Any loss already part of AC–AC or DC–AC round-trip efficiency

Principle:
AUX = Only electrical input of essential auxiliary systems. Losses remain in efficiency calculations.

4. Verified Global OEM Auxiliary Data (Independent Validation)

4.1 PCS AUX Validation (USA / Europe / Japan OEMs)

Conclusion (PCS):

A realistic PCS AUX for 1.375 MVA = 1–3 kW (hot climates: 2–3 kW).
This is global industry standard.

4.2 Battery Container AUX Validation (5 MWh DC Block)

Independent sources:

• CPS (USA) 5 MWh BESS → 50 kVA aux interface, typical continuous load ≈ 10–15 kW

• Chinese 5.016 MWh system → Reconfirmed reduced auxiliary load per MWh

• Older 2 MWh containers → 30 kVA aux interface, typical ≈ 7–11 kW

• Verified OEM (5 MWh, liquid cooling) →

  • 8.1 kW @ 25°C

  • 9.8 kW @ 35°C

  • 12.5 kW @ 45°C

Conclusion (Container):

Modern 5 MWh container AUX = 8–13 kW depending on ambient temperature.
This matches USA–China–Europe benchmarks.

5. Final Verified Auxiliary Consumption Values (No Double Counting)

We now combine only true AUX components, excluding PCS losses.

6. Final AUX Values – Climate-Wise (5 MWh DC Container + External PCS)

PCS rating reference: 1.375 MVA

Scenario A — Hot Summer + Cold Winter (Jaisalmer-Type)

Ambient: 45–50°C summer, 5–10°C winter

Summer AUX (0.25C Cycling)

• 5 MWh Container AUX: 12–14 kW

• PCS AUX (verified): 2–3 kW

• Other Aux (ACDB, UPS, SCADA, LV panels): 3–5 kW

➡ Total Summer AUX = 17–22 kW

= 1.24% – 1.60% of PCS rating

Winter AUX

• Container heating AUX: 8–10 kW

• PCS AUX: 1–2 kW

• Other Aux: 3–5 kW

➡ Total Winter AUX = 12–17 kW

= 0.87% – 1.24% of PCS rating

Scenario B — Continuous Low-Temperature Climate (Europe / Canada)

Ambient: 0–25°C

• Container AUX: 7–9 kW

• PCS AUX: 1–2 kW

• Other Aux: 3–5 kW

➡ Total AUX = 11–16 kW

= 0.80% – 1.16% of PCS rating

Scenario C — Continuous High-Temperature Climate (Gulf Countries)

Ambient: 35–45°C all year

• Container AUX: 11–13 kW

• PCS AUX: 2–3 kW

• Other Aux: 3–5 kW

➡ Total AUX = 16–21 kW

= 1.16% – 1.53% of PCS rating

7. Final Executive Summary (Use for EPC / Management / Lenders)

For a 5 MWh liquid-cooled BESS block with an external 1.375 MVA PCS:

• AUX is dominated by thermal management of the BESS container

• PCS AUX is 1–3 kW, validated by ABB, SMA, Hitachi, Sungrow

• Container AUX is 8–13 kW, validated by CPS (USA), Chinese 5 MWh systems, older 2 MWh references

• Total AUX of the block ranges from:

• 0.8–1.2% of PCS rating → Cool climates

• 1.2–1.6% of PCS rating → Hot desert / Indian summer

• No double counting: PCS losses & transformer losses are excluded from AUX.

• Values comply with global OEM expectations and international best practices.

8. Final One-Line Statement

“The total auxiliary load for a 5 MWh liquid-cooled BESS block with an external PCS is 11–22 kW (0.8–1.6% of PCS rating), verified against global OEM data (ABB, SMA, CPS, Chinese 5 MWh systems), with container AUX 8–13 kW and PCS AUX 1–3 kW.”