23 may 2019 - uib
TRANSCRIPT
D epa r tm en t o f P hy s i c s a nd Tech no l og y
Lars Egil Helseth
Department of Physics and Technology
23 May 2019
Nanotechnology
D epa r tm en t o f P hy s i c s a nd Tech no l og y
Outline of this talk
âWhat is nanotechnology? Benefits and challenges
âNanotechnology for harvesting electrical energy
âNanotechnology for storing electrical energyâ Batteries
â Supercapacitors
D epa r tm en t o f P hy s i c s a nd Tech no l og y
0.1 nm
1 nm
10 nm
100 nm
1000 nm
10000 nm
100000 nm
Water
molecule
Red
blood
cell
DNA
Hair
strand
What is nanotechnology?
Study and construct technology based on
structures with at least one dimension
between 1 nm and 100 nm
D epa r tm en t o f P hy s i c s a nd Tech no l og y
We are self-assembled nanotechnology!
⢠DNA and other biopolymers in the
body
⢠Motorproteins for cleaning
(kinesin) or actuation (myosin)
D epa r tm en t o f P hy s i c s a nd Tech no l og y
Why nanotechnology?
⢠Quantum effects become
important at small scales.
Examples: New light sources
(lasers,labels, etc), data storage and
communication technology.
By changing the dimension of the quantum well you may change
the energy levels and therefore also the colors of the emitted light!
n=1
n=2
n=3
electron
D epa r tm en t o f P hy s i c s a nd Tech no l og y
Why nanotechnology?
⢠Surface features become more important
Examples: self-cleaning surfaces
1 mm
Nature Made by reactiveion etching at UiB
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Why nanotechnology?
⢠Fluctuations and cluster formation becomes more important.
Example: Gluing soft tissue (for example wounds)
Glue tissue using nanoparticlesGlue tissue using pH-
controlled chitosan
D epa r tm en t o f P hy s i c s a nd Tech no l og y
Solution: Everyone should drive
a nanocar.
(only 0.014 mm/hour)
Why nanotechnology?
⢠New and unexpected solutions to current problems
Example: Bompengesituasjonen
D epa r tm en t o f P hy s i c s a nd Tech no l og y
http://wumo.no/2012/06/08/
⢠We do not know enough about how the nanoparticles
influence the environment and our health
Challenges: Environmental threats
D epa r tm en t o f P hy s i c s a nd Tech no l og y
Challenges: Environmental threats
NaClO
+
Carbon nanotubes
CO2
CSIRO
â > 100 companies and hundreds of tons produced annually.
How to deal with the waste?
â Carbon nanotubes are known to influence cell growth and may
produce asbestos-like pulmonary response.
D epa r tm en t o f P hy s i c s a nd Tech no l og y
How can nanotechnology contribute to renewable electrical energy sources?
D epa r tm en t o f P hy s i c s a nd Tech no l og y
All activity requires energy
⢠Deleting 1 bit on a computer harddisc leads to a heat loss of kBT â10-20 J
⢠One search using Google is estimated to require about 1 kJ (1/4
Wh). Google report more than 40 000 searches per second.
Unit: Joule (J) or Wh (=1 W x 3600 s = 3600 J)
Power = Energy/time (unit: Watt = Joule/second)
â˘Minimum power needed to run all searchs: 40 MW
D epa r tm en t o f P hy s i c s a nd Tech no l og y
How much electrical energy do humans use?
⢠A normal heating oven may consume 1 kW electrical power. In one hour the energy used would
be 1 kWh = 1000 W¡3600 s=3.6 MJ. In one year this becomes 365¡24¡1kWh â 9 MWh
⢠If a household consumes 16 MWh electrical energy per year it will cost 9120 kr if the price per
kWh is 0.57 kr (16000 kWh * 0.57 kr/kWh = 9120 kr)
⢠One could use this electricity to heat the home, or do 16 MWh / (0.25 Wh per search) = 64
million Google searches
D epa r tm en t o f P hy s i c s a nd Tech no l og y
Use of electrical power Power = Energy/time
(unit: Watt)
D epa r tm en t o f P hy s i c s a nd Tech no l og y
Energy demand
Renewable energy sources Why
Large scale(>> 1 kW)
Sun farms(photovoltaic or photothermal), windfarmshydro power plants, geothermal power plants, etc
Reducedependency onoil
Small scale
(< 10 W)
Use sunlight, vibrations, rain, temperature differences, etc
Run smallcomputers, sensors and actuators; democraticdistribution ofelectrical energy?
The distribution of
electrical energy is not
democratic!
Can a better
distribution give rise to
less conflict?
Large versus small units
D epa r tm en t o f P hy s i c s a nd Tech no l og y
Small units needed to power IoT
Node
Sensor1
Sensor2
Aktuator1
Aktuator2
⢠Internet of Things (IoT).
⢠If each node uses 1 W, one needs
at least 20 GW (175 TWh over
one year) to power IoTâŚtoday
mostly with batteriesâŚ
⢠In 50-100 years we may have
20¡1012 nodes, demanding 20 TW.
Where should all this energy come
from?
⢠Today there are > 20¡109 nodes (mobile
phones, smartwatches, traffic and
environmental stations, etc)
D epa r tm en t o f P hy s i c s a nd Tech no l og y
How to develop future energy sources?
Need to consider:
1) Democratic and easy distribution
2) Life cycle analysis (no net waste)
D epa r tm en t o f P hy s i c s a nd Tech no l og y
Nanotechnology for harvesting electrical energy
âSolar cells
âTriboelectrical nanogenerators (contact electrification)
D epa r tm en t o f P hy s i c s a nd Tech no l og y
Solar cells based on nanotechnology
- Increased âcaptureâ of sunlight
using nanostructures as
compared to flat surfaces
- There is a great hope of
cheaper production
- Increased thermal management
(heat lead away more efficiently)
-Self-cleaning surfaces that reduce
absorbtion of sunlight
D epa r tm en t o f P hy s i c s a nd Tech no l og y
Contact electrification for energy harvesting
Electrostatic charging occurs when two materials are contacted or rubbed
and then separated
Contact
+ + + + + + + - - - - - - -
No contact No contact
+ + + + + + +
- - - - - - -
For an insulator, the charge may remain at the surface for a very long time (many decades), whereas for a metal the charge may quickly move away ifit has somewhere to go (e.g. an external wire).
D epa r tm en t o f P hy s i c s a nd Tech no l og y
RL
I
Metal
- - - - - - - - - -Dielectric
RL
+ + + + + + + + + +
- - - - - - - - - -
+ +
I
+ + + + + + + + + +
- - - - - - - - -
RLRL
+ + + + + + + + + +
- - - - - - - - - -
+ + + + + + + + +
- - - - - - - - - -
+ +
- -
Metal
+ + + + + + + + + +
Triboelectrical nanogenerators: principle
D epa r tm en t o f P hy s i c s a nd Tech no l og y
Triboelectric nanogenerators powered by humans
Mechanical energy is
transformed into
electrical energy
D epa r tm en t o f P hy s i c s a nd Tech no l og y
Examples of systems benefitting from nanotechType Principle Power density Advantages Disadvantages
Solar cell Photovoltaic effect 10-100 mW/cm2 Long lifetime, high power
density, continuous
current, mature
technology
Does not work at night,
needs cleaning, low
voltage
Rain cell Contact charging 10-100 mW/cm2 Made of flexible
materials, can be mounted
on any infrastructure, can
be combined with solar
cells
Only works when there
is rain, low power
density, discontinuous
current, immature
technology.
Thermoelectric cell Thermoelectric
effect
10-100 mW/cm2 Long lifetime, continous
current
Needs temperature
differences, low power
density, immature
technology
Vibration cell Piezoelectric or
triboelectric
nanogenerators
(contact charging)
1-100 mW/cm2 Small, flexible, high
power density
Needs vibrations,
discontinuous current,
immature technology
D epa r tm en t o f P hy s i c s a nd Tech no l og y
Nanotechnology for storing electrical energy
âLi-ion rechargeable batteries
âSupercapacitors
D epa r tm en t o f P hy s i c s a nd Tech no l og y
Working principle of modern Li-ion batteries
Convert chemical energy to electrical energy.
Polymer Reviews 51(3):239-264 ¡ July 2011
https://www.youtube.com/watch?v=VxMM4g2Sk8U
D epa r tm en t o f P hy s i c s a nd Tech no l og yT
emp
eratu
re(°
C)
Safe operation
2 4 6 Voltage (V)
100
Danger: LiFePO4 breaks
down and releases oxygen
200
300
Warning: electrolyte
decomposition;
destruction of electrode
protection layers
Danger: Overcharge;
formation of dendrites,
short circuit
Limits of modern Li-ion batteries
D epa r tm en t o f P hy s i c s a nd Tech no l og y
Example: An AA battery has charge capacity 2500 mAh (=2.5A x 3600s =9000 C).
How long time does it take to discharge it using a current of 100 mA?
How much charge can a battery store?
đ = đđ ⢠Q=charge, I=charging/discharging current, and t is the
time needed to discharge/charge the battery.
Answer: đĄ =2500đđ´â
100đđ´= 25 h
D epa r tm en t o f P hy s i c s a nd Tech no l og y
How much energy can you expect from a battery?
D epa r tm en t o f P hy s i c s a nd Tech no l og y
Batteries versus gasoline
⢠Gasoline has an energy density of 12.5 kWh/kg.
⢠A car using 1 liter bensin per 10 km, consumes 3.6 MJ per km =
1kWh/km.
⢠400 km therefore requires 400 kWh. If the
the car is to drive 400 km it has to use 40
liter bensin (=40 liter ¡ 0.8 kg/liter = 32 kg).
⢠Li-ion batteries have specific energy density of about 1 kWh/kg.
http://www.tu.no/industri/2014/03/27/denne-bussen-har-fire-tonn-batterier
⢠This requires Li-ion batteries of mass 400
kWh/(1 kWh/kg)= 400 kg. More work is
needed to reduce weight of batteries!!
D epa r tm en t o f P hy s i c s a nd Tech no l og y
Can we make lighter Li-ion batteries?
â˘Can we find another easily accessible
element with large ability to store
charge? Yes: Si
â˘Li4.4Si has the largest charge capacity of
4212 mAh/g (15 163 Coulomb/gram) and
gives 8.5 kWh/kg.
Possible anode materials
D epa r tm en t o f P hy s i c s a nd Tech no l og y
â˘Si has the largest capacity of the easy
available materials.
â˘Si films or bulk cracks in use due to large
internal stress. Solution: nanostructured anode!
Nanostructuring increases the battery charge capacity
â˘Problem: Si- nanostructures detach from
the metal electrode.
D epa r tm en t o f P hy s i c s a nd Tech no l og y
D epa r tm en t o f P hy s i c s a nd Tech no l og y
Electrical energy can be stored in capacitors
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/capac.html#c1
đ =đ
đđđđ
D epa r tm en t o f P hy s i c s a nd Tech no l og y
Ordinary capacitors versus supercapacitors
+ + + + + +
- - - - - -
d
Solid state capacitor (d>1mm)
+ + + + + +- - - - - -
+ + + + + +- - - - - -
d
Electrolyte capacitor (d<10 nm)
++++++++++++++--------------------
++++++++++++++--------------------
Supercapacitor (d<10 nm and A large)
d-Uses nanocarbon to create
large A (> 1000 m2/g) and small
d (< 1 nm). This gives >10F/g.
-Capacitances up to about 5000
F available
C<1 mF C<1 F
D epa r tm en t o f P hy s i c s a nd Tech no l og y
Appearance of a supercapacitor
L. Zhang et al., Renewable and sustainable energy reviews (2017)
D epa r tm en t o f P hy s i c s a nd Tech no l og y
How much charge can a supercapacitor store?
đ = đđ ⢠Q=charge, V is the largest available voltage
determined by the electrolyte and C is the capacitance.
Example: A supercapacitor a rated capacitance of 5000 F and maximum voltage 2.7 V.
What is the charge that this supercapacitor can store?
Answer: Q = 5000F Ă 2.7V = 13 500 C
D epa r tm en t o f P hy s i c s a nd Tech no l og y
How much energy can a supercapacitor store?
Example: A supercapacitor a rated capacitance of 5000 F and maximum voltage 2.7 V.
What is the energy that this supercapacitor can store in Wh ?
đ =đ
đđđđ
⢠Q=charge, V is the largest available voltage and
C is the capacitance.
Answer: E =1
2Ă 5000 Ă (2.7V)2= 18 225 J â 5 Wh
D epa r tm en t o f P hy s i c s a nd Tech no l og y
Charge-discharge of 400F supercap
Time (s)10 0005 0000
Vo
lta
ge
(V
) 2
1
0
-Ideal supercapacitors should charge at constant current with voltage V=It/C and
remain at the same voltage when the current becomes zero.
-Real supercapacitors show self-discharge due to unwanted leakage currents and
redistribution of charge
-Real supercapacitors cannot be used to rectify ac currents at frequencies > 10 Hz
Limits of modern supercapacitors
D epa r tm en t o f P hy s i c s a nd Tech no l og yT
emp
eratu
re(°
C)
Safe operation
2 4 6 Voltage (V)
100
200
300
Warning: increased
leakage currentand and
possible electrolyte
decomposition
Danger: Overcharge;
gas formation
Limits of modern supercapacitors
D epa r tm en t o f P hy s i c s a nd Tech no l og y
Battery vs capacitor107
101
104
Capacitor106
105
103
102
1
0.01 0.1 1 10 100 1000
Supercapacitor
Battery
Fuel cell
Sp
ecif
icp
ow
er(W
/kg)
Specific energy (Wh/kg)
D epa r tm en t o f P hy s i c s a nd Tech no l og y
Applications of supercapacitors
D epa r tm en t o f P hy s i c s a nd Tech no l og y
Thank you for not falling asleep!