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RENEWABLE ENERGY FROM EVAPORATING WATERPresented by JAISY VARGHESE S7 E Roll No: 241

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IntroductionEvidence from natureConversion Bacterial sporesChallengesEvaporation driven enginesHYDRAsOscillatory engineRotary engineAdvantages and DisadvantagesConclusion Future scope

CONTENTS2

Evaporation dominant form of energy transfer in earths climate.Evaporation liquid phase gaseous phaseLarge 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?????

INTRODUCTION3

Ascent of sap in plantsOpening of pine conesTravelling of water from the earth to the top of the tallest redwood.Delivery of snow to the top of the Himalayas. EVIDENCE FROM NATURE

4Fig.1 Pine cones

Hygroscopic materialsMechanical force in response to changing relative humidityContracts when dryExpand when wetVolume of water less large pressure changeNanoscale confinement of water induces large pressureHere we use bacterial spores CONVERSION5

Tough and non-reproductive structure produced by certain bacteriaResistanttoenvironmentalstressanddifficulttodestroy.Bacillus subtilis found in soil

BACTERIAL SPORES

6Fig.2 Bacterial spores

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Time scale of wetting and drying depend on the square of travel distance of water

Spore layer cant exceed micrometre range

Slow rate of change of relative humidity in environment limits power output

CHALLENGES8

The oscillatory engine

The rotatory engine They start and run autonomously when placed at air-water interfaces

Both used hygroscopy - driven artificial muscles or HYDRAs

EVAPORATION DRIVEN ENGINES9

Bacterial spores deposited on thin plastic filmsFilms change curvature as a function of relative humidityAlternating sides of longer tapes coated with spores to make overall movement linearSeveral tapes assembled as stacks with gaps between layers Layered architecture maximizes surface area for evaporationSmall thickness of spore layer reduces travel distance of water HYDRAs 10

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Fig.3 HYDRAs

OSCILLATORY ENGINEEvaporation rate controlled by shutter mechanismSpore coated films coupled to shutters and load springShutters are connected to bistable beamAllows and blocks evaporation in cyclical fashion

12Fig.4 Oscillatory Engine

WORKING

13Fig.5 Working of oscillatory engine

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.

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Oscillatory engine is coupled to a generatorWhen water is poured in the engine, LEDs glowPower provided 60WBut still significant , when small area of water covered by HYDRAs (9.6cm 7.6cm) is considered

DEMONSTRATION

15 Fig.6 Oscillatory Engine Demonstration

Moisture mill Two structuresHYDRAs are assembled around two concentric rings Four or five such structures are connected in parallel via a central axis

ROTARY ENGINE16

Fig.7 Assembling HYDRAs

17The 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

WORKING18Fig.9 Working of rotary engine

Wet paper provides the humidity gradientInduces different degrees of curvature in spore-coated filmsHorizontal shift in the centre of mass of the entire structureCreates torque that causes the rotational motionBlue plastic blocks attached to HYDRAs increase positional shift of M19Contd..

EVA- first evaporation driven carMiniature car of 0.1 kgEngine is placed above a frame attached to two pairs of wheelsEngines rotation is coupled to the front wheels with a rubber belt As the water evaporates from wet paper, the car moves forward DEMONSTRATION

20Fig.10 EVA

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Renewable energyUbiquity of evaporation in natureLow cost of materials usedBacterial spores are resistant to temperature, stress etc.

Engine stops beyond certain relative humidity

ADVANTAGESDISADVANTAGES22

CONCLUSIONA new source of energyNanoscale energy conversion mechanism is scaled up to create macroscopic devicesEvaporation-driven car and the powering of LEDs highlight the energy from evaporationThe engines presented here may find applications as energy sources for a wide range of off-the-grid systems that function in the environment23

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.

FUTURE SCOPE 24

[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

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