Technical study · Engineering & Design

Megawatt Truck Chargers in Queensland Heat

Site CFD and derating curves for megawatt truck chargers rated to 40°C on a yard that regularly runs hotter, and the layout changes that hold full output on summer afternoons.

Electric truck plugged in to a charger

What the client needed

A charging operator was installing megawatt charging for heavy trucks at a logistics yard in South East Queensland. The vendor datasheet showed full output to 40°C, but the yard is a large expanse of hardstand that regularly goes past 40°C in summer, and the operator's customers expected consistent charge times.

The question they needed answered: How much will the chargers derate in a real Queensland summer, and what can be done about it before installation?

  • 710 kWoutput at 45°C with the vendor's standard layout (rated 1.2 MW)
  • 6 to 8°Cextra intake temperature from cabinets recirculating hot air
  • ~46°Cambient at which the revised design still gives full output

What we did

  • Calculated heat rejection from the power cabinets and dispensers at full output.
  • Modelled the site with CFD, including solar load on the cabinets, radiant heat from the hardstand and recirculation between cabinets.
  • Built derating curves for the vendor's standard layout and for alternative arrangements.
  • Turned derating into charge times for a typical 600 kWh electric prime mover.

What we found

The main problem is recirculation. Cabinets placed back to back against a wall draw in each other's exhaust, so intake air runs 6 to 8°C above ambient and derating starts at about 38°C.

At 45°C the standard design gives about 710 kW instead of 1.2 MW. A 20 to 80% charge on a 600 kWh truck goes from about 22 minutes to over 30.

Hot afternoons are also the busiest time. With each charge taking about 45% longer, the hub can serve roughly a third fewer trucks in the afternoon peak.

A shade canopy, cabinets turned so intakes and exhausts are separated, and the vendor's higher-capacity cooling option hold full output to about 46°C.

Line chart of charger output against ambient temperature for the standard and revised designs
Charger output against ambient temperature. The standard layout derates from about 38°C; the revised design holds full output to about 46°C.

What we recommended

  • Adopt the revised layout and shade structure before civil works are finalised. It costs far less to change on paper than on site.
  • Write a site-specific temperature performance requirement into the supply contract, not just the datasheet rating.
  • Monitor intake temperatures through the first summer to confirm performance and refine the model.

Key assumptions

Converter efficiency 97% at full load. Derating slope based on typical vendor curves. 600 kWh battery charged from 20 to 80%, average power around 85% of peak.

Related work

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