Volvo Construction Equipment has released the "Boom-Energy Harvest" system as an option on its EC230 electric excavator. In electric excavators, the largest single energy consumer is not digging-it is converting electricity into hydraulic pressure for the boom raise, and then simply throttling that same potential energy away through orifices when the boom lowers with a loaded bucket. In a typical loading cycle, a 20-ton machine raises and lowers a 10-ton combined boom, arm, and bucket mass hundreds of times per hour, dissipating megajoules of recoverable energy as heat.
The Boom-Energy Harvest system adds a "Hydraulic-to-Electric Recovery Module" on the boom lowering circuit. The engineering innovation is the "Proportional Regeneration Valve" paired with a bidirectional pump/motor unit. When the operator commands boom lowering, instead of metering oil across the main control valve spool, the controller diverts the cylinder outflow to the recovery pump/motor, which spins as a generator. Critically, the recovered electricity is not fed directly to the battery: lithium cells accept charge relatively slowly, and a fast bucket dump would exceed the charge acceptance window. Instead, the energy lands in a 120-kilojoule "Supercapacitor Bank" mounted beside the inverter.
The supercapacitor is then discharged on the next surge demand-typically the swing motor acceleration at the start of the next loading cycle-where motor inrush current is high. The engineering term for this strategy is "peak shaving": the battery supplies the steady baseline current while the capacitor supplies and absorbs the transients. This has a secondary benefit: by shielding the battery from high current ripple in both directions, the system reduces cell heating and is projected to extend battery service life by 20%. Volvo reports a 12% increase in effective work time per charge in pipe-laying duty cycles, where the boom is cycled almost continuously.
