Overview#
The Cat G3520E is a 2022 ekW continuous natural gas engine designed for combined heat and power (CHP), distributed generation, and industrial baseload applications. As the V-20 variant of Cat's G3500 gas engine platform, it extends the proven G3516 architecture by four additional cylinders for higher power density.
The G3520E uses ADEM3 electronic controls with integrated air-fuel ratio management, separate-circuit aftercooling (SCAC), and lean-burn combustion to achieve 500 mg/Nm3 NOx engine-out while delivering 41.5% electrical efficiency.
Engine platform#
The G3520E shares the G3500 block architecture:
- V-20 configuration with 11.9:1 compression ratio
- SCAC (separate circuit aftercooling) -- two-stage system with jacket water/oil cooler/first-stage aftercooler on circuit one, and second-stage aftercooler on circuit two
- ADEM3 control system with integrated air-fuel ratio management
- Dry exhaust manifold design
- 2000 m altitude capability at 25C inlet air -- one of the highest in the G3500 lineup
Engine output is 2100 bkW at full load, with generator efficiency of 96.3% yielding 2022 ekW net electrical output.
Efficiency and heat recovery#
At full load (ISO 3046/1):
- Electrical output: 2022 ekW (41.5% efficiency)
- Jacket water heat: 655 kW recoverable
- Lube oil heat: 124 kW recoverable
- Stage 1 aftercooler heat: 402 kW recoverable
- Exhaust heat to 120C: 988 kW recoverable
- Total CHP efficiency: 86.8%
The G3520E's high thermal output -- over 2 MW recoverable heat -- makes it particularly well-suited for industrial process heating and district energy applications.
Emissions profile#
The G3520E is a lean-burn engine with controlled NOx levels:
- NOx: 500 mg/Nm3 (corrected to 5% O2) -- held constant across all load points
- CO: 1153 mg/Nm3 at full load
- Formaldehyde: 250 mg/Nm3
An oxidation catalyst is typically required for CO and formaldehyde compliance in most jurisdictions. The constant NOx level across load points simplifies emissions permitting compared to engines with variable NOx profiles.
Our service experience#
The G3500 gas engine platform has extensive field history in continuous-duty applications. The G3520E's 20-cylinder configuration demands disciplined spark plug management -- with 20 plugs to maintain, a systematic replacement schedule (every 4,000 hours) is essential. SCAC water quality and temperature stability remain critical: inlet manifold temperature must be controlled within +/-5C to avoid detonation. The ADEM3 system requires Cat Electronic Technician (Cat ET) for diagnostics.
