ABSTRACT
We report on the design, fabrication and testing of a
low pressure head Tesla microturbine. We began
developing this technology as a means of scavenging
energy from fluids flows induced in plant-like
evaporative systems. Unlike traditional inertial turbines,
Tesla turbines have high efficiency when driven with low
pressure flows, are relatively simple to manufacture and
scale down very favorably. The 1 cm3 rotor diameter
turbine presented here is, to our knowledge, the smallest
Tesla turbine reported, with an unloaded peak power of
45 mW (12 cc/sec flow, 17% efficiency) and a peak
efficiency of 40% (< 2 cc/sec flow). Moreover, the entire
turbine is built using a variety of modern commercial
rapid prototyping methods, making its construction
accessible to almost anyone. Beyond applications in
evaporative scavenging, Tesla microturbines may find
use as components in ultrasmall-profile heat engines and
for energy generation from sources of low pressure head
flow.
KEYWORDS
Tesla turbine, viscous turbine, miniaturize turbine,
power MEMS, microturbine.
INTRODUCTION
The cohesive properties of water enable the ascent of
sap to the top of trees against gravity and frictional losses,
driven by evaporation at microscale pores in leaves. For a
100 m tree, this corresponds to a minimum pressure
difference of 10 bars between leaf and root [1], and with a
plant evaporation rate of 5nl/cm2/sec, a power of
15μW/cm2 and an ‘energy density’ of 3 kJ per kg of
evaporated water. Earlier work scavenged energy from
evaporation-induced water flows by charging pumping a
circuit via dielectric-water interface transition between
capacitor plates [2]. In this work, we present a
microturbine which can be driven by evaporative flow
(Figure 1).