Power Sources - Powering Biomedical Devices - page 17

of two small microwave ovens at full capacity for 1 h). About 20% of
this energy is converted into mechanical work and most leaves the body
as wasted heat (in order to keep the body warm). Therefore, it is not
surprising that research has focused into harnessing energy from either
body activities or heat waste (temperature difference).

Active power generation produces significantly higher power out-
put, as evidenced by bicycle generators powering small TV sets. For
example, an occasional cyclist can produce close to 150 W, but a pro-
fessional can output on average up to 700 W (Flipsen, 2006). Some
studies in this area have covered the power outputs expected from
some activities, such as cranking, shaking, and pedaling, as well as the
comfort of sustained generation. Jansen and Stevels (1999) reported
active power generation levels using lever-driven generators ( B 6 W),
crank-driven generators ( 100 W).

Later work from this group (Slob, 2000) studied the power generation
from sustained one-hand cranking. It was presented that power output
drops close to 40 W from a peak of 150 W after 10 min of continuous
cranking. It was concluded that 28 W on average can be obtained
from sustained cranking for 30 min and that 14 W could be converted
into electricity if assuming a conversion mechanism efficiency of 50%.
Other examples studied include the peak power from cycling and row-
ing as 600 and 800 W, respectively, but they are reduced to near 20%
after 5 min of continuous activity 1 .

21 W), and bicycle pedaling (

B B

One of the first reviews on energy generation from the human body
was made by Starner (1996). The description included analysis for
available power from body heat (0.2

0.3 W on the neck, 0.6 1.0 W

on the head, and 3 5 W on the entire body surface), respiration

( B 1 W for breathing, B 0.8 W from chest movement), blood pressure
( B 1 W), and other activities, such as typing (0.007

0.02 W), bicep
curls exercising ( B 20 W), arm lifting ( B 60 W), and walking ( B 70 W).
Although those numbers and locations represent an expected average
power limit, devices harnessing those power levels could interfere
severely with everyday activities but devices harvesting a small percent-
age of those levels can be a feasible option.

Acceleration and step frequency were evaluated to determine how
much energy can be available at different body locations and at

1 http://web.kyoto-inet.or.jp/people/kazuho/manasle/manasle.htm . Retrieved January 29 2013.