⚡ Off-Grid Hybrid System Design: 2.4MWp PV + 2MW/4MWh BESS + 2×1000kW Diesel Gensets for 24/7 Industrial Production
📋 1. Project Background & Requirements
An industrial facility operates 24 hours a day, 7 days a week, with daytime load of 1,400 kW (10 hours) and nighttime load of 500 kW (14 hours). Total daily consumption is 14,000 kWh during the day and 7,000 kWh at night, summing to 21,000 kWh per day. The site has no grid connection and is currently powered entirely by two 1,000 kW diesel generator sets.
Customer objective:
- Reduce diesel genset runtime and number of starts to lower fuel costs and maintenance
- Integrate solar PV + battery storage to supply as much load as possible
- Gensets remain as backup – only start when PV + BESS cannot meet load
- When gensets are running, they supply the full load while PV power is dedicated to charging the battery
After engineering evaluation, the customer accepted the final design: 2,400 kWp PV, 2,000 kW PCS (two 1,000 kW units), 4,000 kWh battery, with two 1,000 kW gensets retained. The system uses IMAXPWR’s proven 480 kW MPPT + 500 kW PCS + 1,000 kWh battery modules in parallel, with an STS for seamless transition between island and genset-connected modes.
🔍 Application scenario: Off-grid industrial facility · 24/7 operation · Day load 1,400kW / Night load 500kW · PV + BESS + Genset hybrid · Diesel reduction & cost optimization
🛠️ 2. Key Engineering Challenges
Challenge 1 — Sizing PV & Battery for 24/7 Load
Determining the optimal PV capacity and battery size to cover 21,000 kWh daily demand, while ensuring reliable nighttime operation and minimizing diesel runtime.
Challenge 2 — Seamless Genset Integration & STS Logic
Designing EMS strategy to start gensets only when PV+BESS cannot support load, and when gensets run, redirect all PV power to battery charging while gensets supply loads.
Challenge 3 — Parallel Operation of Multiple PCS & MPPT Modules
Scaling up from standard 500kW PCS + 1MWh battery modules to 2MW/4MWh requires precise parallel synchronization, load sharing, and communication redundancy.
📐 3. Engineering Analysis — Why This Design
☀️ PV Sizing — 2,400 kWp
With an effective peak sun hours of 5.8 hours, the PV array generates:
However, using a more optimistic 6 hours full-load equivalent (as accepted by the customer):
Total daily consumption is 21,000 kWh. The PV supplies 14,400 kWh, leaving 6,600 kWh to be covered by battery discharge and genset backup. The 4,000 kWh battery (with 80% DOD = 3,200 kWh usable) can cover nighttime load for about 6–8 hours, after which gensets start and supply load while charging the battery using PV power (as PV is still generating or already stored).
🔋 Battery & PCS Sizing — 4MWh / 2MW
Battery capacity of 4,000 kWh (four 1,000 kWh modules) provides:
- Usable capacity: 4,000 kWh × 80% DOD = 3,200 kWh
- Nighttime support: 3,200 kWh ÷ 500 kW = 6.4 hours of full nighttime load coverage
- Combined with PV generation before sunset, the system can often push diesel start time later into the night, reducing runtime significantly.
The 2,000 kW PCS comprises four 500 kW IMAXPWR MSP500HC units in parallel. This modular approach offers:
- N+1 redundancy: If one unit fails, remaining 1,500 kW can still cover daytime peak loads.
- Scalability: Easy to expand with additional modules.
- Proven reliability: Each 500 kW module is a standard IMAXPWR product with field-proven performance.
🧠 EMS Control & Genset Coordination
The IMAXPWR Energy Management System (EMS) orchestrates the hybrid operation:
- Normal mode (PV + BESS): During daylight, PV powers loads and charges battery. Battery discharges to cover any shortfall when PV is insufficient.
- Genset start condition: When battery SOC falls below a set threshold (e.g., 20%) and PV generation is insufficient to meet load, EMS starts one or both diesel gensets.
- Genset running mode: Gensets supply the entire load. All PV generation is directed to battery charging (via MPPT converters) until battery reaches 100% SOC, then gensets are stopped.
- STS transition: The Static Transfer Switch ensures seamless switching between island mode (BESS forming the grid) and genset-connected mode (gensets forming the grid). The transition is < 50 ms, protecting sensitive loads.
- Priority: Maximize renewable utilization; gensets are the last resort.
🔄 4. System Architecture
Day 1,400kW / Night 500kW
backup / start when needed
< 50ms transition
⚙️ 5. IMAXPWR Engineering Solution
Hardware Configuration
- PV array: 2,400 kWp (customer supplied)
- MPPT: 5 × IMAXPWR 480 kW DC/DC converters (one per PV block)
- PCS: 4 × IMAXPWR MSP500HC 500 kW bidirectional AC/DC converters (total 2,000 kW)
- Battery: 4 × 1,000 kWh LFP battery banks (total 4,000 kWh), 650–900V DC, 80% DOD
- EMS: IMAXPWR Energy Management System with genset start/stop logic and STS control
- STS: Static Transfer Switch for seamless island-to-genset transition
- Cooling: Liquid cooling for PCS units; forced air for battery containers
Control Strategy (EMS logic)
- Solar prioritization: PV supplies load first; surplus charges battery.
- Battery discharge: When PV < load, battery discharges to cover deficit, down to 20% SOC.
- Genset start condition: When battery SOC ≤ 20% and PV is insufficient, EMS starts gensets (one or both depending on load).
- Genset running mode: Gensets supply all load; PV power is fully directed to charging battery (via MPPT).
- Genset stop condition: When battery SOC reaches 100%, EMS stops gensets and resumes island mode.
- STS action: Transfers between island mode (BESS forms grid) and genset-connected mode without interruption.
🛡️ Safety & Reliability Design
- Electrical protection: Overcurrent, overvoltage, underfrequency, anti-islanding, and short-circuit protection.
- Thermal management: Liquid cooling maintains PCS temperature; battery BMS monitors individual cells.
- Redundant communication: Dual CAN/RS485 links between all PCS, MPPT, BMS, and EMS.
- Black-start capability: BESS can self-start from battery to form grid and initiate genset start if needed.
- Parallel synchronization: Droop control ensures stable load sharing among four PCS units and with gensets.
Need a Similar Off-Grid Hybrid System?
Many remote industrial sites rely on diesel gensets – we can help you integrate PV + BESS to slash fuel costs and emissions.
IMAXPWR engineering team can evaluate your:
🔋 Genset coordination logic
🔄 Parallel PCS & MPPT design
⚙️ STS & islanding solutions
📊 6. Engineering Comparison — Design Options Evaluated
| Parameter | Option A (1 Genset + 1.2MW PV + 1MW/2MWh BESS) | Option B (2 Gensets + 2.4MW PV + 2MW/4MWh BESS) — ✅ Selected |
|---|---|---|
| PV capacity | 1,200 kWp | 2,400 kWp |
| PCS capacity | 1,000 kW (2×500kW) | 2,000 kW (4×500kW) |
| Battery capacity | 2,000 kWh | 4,000 kWh |
| Daily PV generation (6h) | 7,200 kWh | 14,400 kWh |
| Nighttime battery support | ~3.2h (at 500kW) | ~6.4h (at 500kW) |
| Estimated diesel runtime reduction | ~40% | ~65% |
| CAPEX | Lower | Higher but better ROI over 5 years |
📈 7. Expected Engineering Benefits
Diesel Fuel Reduction
Operating Cost Savings
CO₂ Reduction / Year
Note: These are expected benefits based on design modeling with 6h PV equivalent and actual load profiles. Actual savings depend on solar irradiance and load variation.
📝 8. Key Engineering Lessons Learned
- PV oversizing pays off in off-grid scenarios. The 2.4 MWp array ensures high renewable penetration even on cloudy days; the extra capacity charges the battery quickly when gensets are running.
- Modular architecture simplifies scaling. Using 480kW MPPT + 500kW PCS + 1MWh battery blocks allowed rapid deployment and future expansion.
- EMS logic must prioritize battery health. The 20% SOC floor prevents deep discharge while leaving sufficient reserve for emergency starts.
- STS transition speed is critical. The < 50 ms switching ensures sensitive industrial equipment does not trip during genset start/stop.
- Communication redundancy prevents single points of failure. Dual CAN buses between all power electronics guarantee reliable coordination.
⚠️ 9. Common Mistakes to Avoid in Similar Projects
- Underestimating nighttime load duration — Battery must be sized to cover the full night or until gensets start; otherwise, frequent genset starts reduce engine life.
- Incorrect PV-to-battery ratio — Too little PV means gensets run longer; too much PV may be wasted if battery cannot absorb surplus.
- Neglecting STS coordination — Improper synchronization can cause blackouts or equipment damage during transition.
- Ignoring genset minimum load — Gensets should not run below 30% load; EMS must ensure sufficient load when gensets are on.
- Overlooking cooling for high-power PCS — Four 500kW units generate significant heat; liquid cooling capacity must match ambient conditions.
Ready to Design Your Off-Grid Hybrid Power System?
Let our engineering team optimize your PV + BESS + genset integration.
Send us your load profile and site data — we’ll deliver a complete system design with EMS logic, equipment list, and ROI analysis.
✓ EMS & control logic
✓ STS & islanding studies
✓ Fuel savings projection
Typical response time: within 24 hours
🏢 About IMAXPWR
ImaxPWR (Imax Power Technology Co., Ltd.) is a national high-tech enterprise specializing in new energy solutions. As an OEM/ODM manufacturer, IMAXPWR focuses on energy storage power conversion equipment, bidirectional PCS, DC/DC converters, V2G modules, energy storage cabinets and integrated microgrid solutions. With professional R&D capabilities and power electronics expertise, IMAXPWR provides reliable and customized energy solutions for global customers in industrial and commercial energy storage, renewable energy integration, smart microgrids and charging infrastructure applications.
📞 Contact IMAXPWR
Ready to Cut Diesel Costs with a PV+BESS Hybrid System?
Contact IMAXPWR technical team for:
⚡ PCS & MPPT parallel design
🧠 EMS & STS solutions
📊 Fuel savings modeling
👨💻 About The Author
This article was reviewed by Ethan Li, an energy storage system specialist focusing on PCS, bidirectional DC/DC converters and microgrid system design.
