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Table 2 Case study for the ankle energy harvesting device [14]

From: Harvesting biomechanical energy or carrying batteries? An evaluation method based on a comparison of metabolic power

     Device mass [kg]   
   0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Walking time [hours] 40 −2.0 −4.9 −7.7 −10.6 −13.5 −16.4 −19.3 −22.3 −25.3 −28.3
60 0.5 −2.4 −5.2 −8.1 −11.0 −13.9 −16.8 −19.8 −22.8 −25.8
80 3.0 0.2 −2.7 −5.6 −8.5 −11.4 −14.3 −17.3 −20.2 −23.2
100 5.5 2.7 −0.1 −3.0 −5.9 −8.8 −11.8 −14.7 −17.7 −20.7
120 8.1 5.3 2.4 −0.5 −3.4 −6.3 −9.2 −12.2 −15.1 −18.1
140 10.7 7.8 5.0 2.1 −0.8 −3.7 −6.6 −9.6 −12.6 −15.6
160 13.3 10.4 7.6 4.7 1.8 −1.1 −4.0 −7.0 −10.0 −13.0
180 15.9 13.0 10.2 7.3 4.4 1.5 −1.4 −4.4 −7.4 −10.4
200 18.5 15.7 12.8 9.9 7.1 4.1 1.2 −1.8 −4.7 −7.7
220 21.1 18.3 15.5 12.6 9.7 6.8 3.8 0.9 −2.1 −5.1
240 23.8 21.0 18.1 15.3 12.4 9.4 6.5 3.6 0.6 −2.4
260 26.5 23.7 20.8 17.9 15.0 12.1 9.2 6.2 3.3 0.3
  1. The values in the table are the differences in metabolic power in watts (carrying batteries minus harvesting device scenarios), for given mass and walking times. Positive values indicate that the harvesting device requires less effort than batteries (i.e., energy harvesting is preferred over batteries), negative values (bold) represent combinations were batteries are preferred options. The Italic values refer to the current published device (0.86kg, 220h).