RENEWABLE ENERGY FROM EVAPORATING WATER

1. Presented by
JAISY VARGHESE
S7 E
Roll No: 24
1

2. 1) Introduction
2) Evidence from nature
3) Conversion
4) Bacterial spores
5) Challenges
6) Evaporation driven engines
7) HYDRAs
8) Oscillatory engine
9) Rotary engine
10) Advantages and Disadvantages
11) Conclusion
12) Future scope
2

3.  Evaporation – dominant form of energy transfer in earth’s
climate.
 Evaporation ⇒ liquid phase → gaseous phase
 Large intermolecular force in water due to H-bonding.
 To break it, large amount of energy required.
 Sun provides energy.
 Energy can neither be created nor destroyed.
 After evaporation, where is this energy?????
3

4.  Ascent of sap in plants
 Opening of pine cones
 Travelling of water from the earth to the top
of the tallest redwood.
 Delivery of snow to the top of the Himalayas.
4
Fig.1 Pine cones

5.  Hygroscopic materials
 Mechanical force in response to changing relative humidity
 Contracts when dry
 Expand when wet
 Volume of water less ⇒large pressure change
 Nanoscale confinement of water induces large pressure
 Here we use bacterial spores
5

6.  Tough and non-reproductive structure produced by certain
bacteria
 Resistant to environmental stress and difficult to destroy.
 Bacillus subtilis – found in soil
6
Fig.2 Bacterial spores

7. 7

8.  Time scale of wetting and drying depend on the square of
travel distance of water
 Spore layer can’t exceed micrometre range
 Slow rate of change of relative humidity in environment limits
power output
8

9. 1. The oscillatory engine
2. The rotatory engine
 They start and run autonomously when placed at air-water
interfaces
 Both used hygroscopy - driven artificial muscles or HYDRAs
9

10.  Bacterial spores deposited on thin plastic films
 Films change curvature as a function of relative humidity
 Alternating sides of longer tapes coated with spores to make
overall movement linear
 Several tapes assembled as stacks with gaps between layers
 Layered architecture maximizes surface area for evaporation
 Small thickness of spore layer reduces travel distance of water
10

11. 11
Fig.3 HYDRAs

12.  Evaporation rate controlled by shutter mechanism
 Spore coated films coupled to shutters and load spring
 Shutters are connected to bistable beam
 Allows and blocks evaporation in cyclical fashion
12
Fig.4 Oscillatory Engine

13. 13
Fig.5 Working of oscillatory engine

14.  Four stages of the oscillatory motion
 Stage I: When the shutters are closed, the relative humidity of
the chamber increases, causing HYDRAs to expand.
 Stage II: As HYDRAs expand towards the right, they force
the buckled beam to switch its position.
 Stage III: Shutters open and let the relative humidity of the
chamber recede, causing HYDRAs to contract.
 Stage IV: Contracting HYDRAs pull the buckled beam and
force it to switch its position which then closes the shutters
and brings the system back to stage I.
14

15.  Oscillatory engine is coupled to a generator
 When water is poured in the engine, LEDs glow
 Power provided ≈ 60µW
 But still significant , when small area of water covered by
HYDRAs (9.6cm × 7.6cm) is considered
15
Fig.6 Oscillatory Engine Demonstration

16.  Moisture mill
 Two structures
 HYDRAs are assembled around two concentric
rings
 Four or five such structures are connected in
parallel via a central axis
16
Fig.7 Assembling HYDRAs

17. 17
 The structure then inserted half way into an enclosure
whose walls are lined with paper
 Driven by water evaporating from wet paper
Fig.8 Moisture Mill

18. 18
Fig.9 Working of rotary engine

19.  Wet paper provides the humidity gradient
 Induces different degrees of curvature in
spore-coated films
 Horizontal shift in the centre of mass of the
entire structure
 Creates torque that causes the rotational
motion
 Blue plastic blocks attached to HYDRAs
increase positional shift of M
19

20.  EVA- first evaporation driven car
 Miniature car of 0.1 kg
 Engine is placed above a frame attached to two pairs of wheels
 Engine’s rotation is coupled to the front wheels with a rubber
belt
 As the water evaporates from wet paper, the car moves
forward
20Fig.10 EVA

21. 21

22.  Renewable energy
 Ubiquity of evaporation in nature
 Low cost of materials used
 Bacterial spores are resistant to temperature, stress etc.
 Engine stops beyond certain relative humidity
DISADVANTAGES
22

23.  A new source of energy
 Nanoscale energy conversion mechanism is scaled up
to create macroscopic devices
 Evaporation-driven car and the powering of LEDs
highlight the energy from evaporation
 The engines presented here may find applications as
energy sources for a wide range of off-the-grid
systems that function in the environment
23

24.  Electricity from giant floating power
generators that sit on reservoirs
 Electricity from huge rotating machines
similar to wind turbines placed above water
bodies.
 Engines without fuel and battery, that use
the mechanical energy stored in spores to
propel a full-sized vehicle.
24

25. [1] Xi Chen, Davis Goodnight, Zhenghan Gao, Ahmet H.
Cavusoglu, Nina Sabharwal, Michael DeLay,Adam Driks&
Ozgur Sahin “Scaling up nanoscale water-driven energy
conversion into evaporation-driven engines and generators.”
Nature Communications [doi:10.1038/ncomms8346] ,volume 6,
16 June 2015.
[2] Chen, X., Mahadevan, L., Driks, A. & Sahin, O. “Bacillus
spores as building blocks for stimuli-responsive materials and
nanogenerators”. NatureNanotechnology., volume 9, 2014.
[3] www.nature.com
[4] www.extremebio.org
[5] www.sciencedaily.com
25

26. 26
Any Questions