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University of Ljubljana, Faculty of Mechanical Engineeringdr. Andrej Senegačnik

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Biofuelsand their role in world energetics

dr. Andrej SenegačnikUniversity of Ljubljana

Faculty of Mechanical engineering

Energy department

July 16, 2019


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- energy and human

- world fuels (energy) statistic

- heat engines – basic

- basic fuel properties

- combustion and emissions

- biofuels

- energy storage systems

- future energetics

- discussion

Lecture topics


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Energy and human

One of the greatest challenges facing humanity during the twenty-first

century must surely be that giving everyone on the planet access to

safe, clean and sustainable energy supplies. (Introduction from the book "Energy systems and Sustainability", Oxford, 2003)

What is energy?

There are many different definitions and forms of energy. Einstein said that

"energy" phenomena can not be clearly defined (E=mc2).

Simplification – ability to perform something – mechanical work, heat up,…


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Energy and human

What kind of energy human needs to stay alive?

Heat: to replace our heat loses to the environment, cooking, metals melting,

construction material,…

Mechanical work: prepare tools, farming, transportation, materials

treatments,…

Light: to see, plants,…

Sound: to communicate

Electricity?in public use last ~130 years (Nikola Tesla, AC, Niagara Falls – Buffalo, NY,

USA, 1897)


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Energy and human

- food: 2000 kcal/d = 2.3 kWh/d

- continuous power ~50 W, 10 h/d 0,5 kWh

- bicycle racer at the race ~400 W

- 1 kWh = 100 kg lifting at speed 1 m/s, 3600 s = 100 kg 3.6 km higher

- 1 kWh = ~1 cycle of washing or dishwasher machine, 1 day of refrigerator

3.6 MJ = 1 kWh


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Energy and human

Why we have problems with energy?

Slovenia ~16 EURc/kWh – tax incl.


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Energy and human

What we use energy for?primary delivered useful energy


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Energy and human

World population?

now ~7.7 billion people


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World energy/fuels consumptionTPES - Total Primary Energy Supply


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World energy/fuels consumptionTPES - Total Primary Energy Supply


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World energy/fuels consumptionFossil fuels production


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World energy/fuels consumptionElectricity generation


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World energy/fuels consumptionRenewables


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World energy/fuels consumptionEmbodied energy, energy per value added


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World energy/fuels consumptionPrices


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Heat enginesbasic principle

Hot body

Heat engineMechanical

work

Hot body

Heat

engine

Mechanical

work

Cold body


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Heat enginesCarnot principle

T

[K]

T0

0

TH

Qin

TC

Qou

tW

I. Law of thermodynamic

U = Q – W

II. Law of thermodynamic

S = gdQ

T

hC = 1 -___TH

TC


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Heat enginesother engines


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Basic fuel properties

Three "combustible" elements:

Carbon – 33 MJ/kg

Hydrogen – 120 MJ/kg

Sulphur – 10 MJ/kg

Water, oxygen and mineral compounds

Also important:

amount of ash, water, other unwanted heavy metals, Hg, V, and other

poisonous elements, Cl, F, Na,…., grindability, surface tension

(atomizing), viscosity, volatility, "storage" pressure, durability, …. ect.


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Basic fuel propertiesHeating value

• Natural gas – highest amount of hydrogen, 25 %, CH4, ~50 MJ/kg (13,8

kWh/kg)

• gasoline, diesel, 13-15 % H, rest carbon, 40-42 MJ/kg (11,4 kWh/kg)

• fresh wood, 8 MJ/kg (2.2 kWh/kg)

• air dry wood, 15 MJ/kg (4.2 kWh/kg)

• hydrogen, 120 (142) MJ/kg, 33 kWh/kg (40 kWh/kg)

• ethanol 26,8 MJ/kg (7.4 kWh/kg)

• methanol 19,7 MJ/kg (5.5 kWh/kg)

• biodiesel 38-40 MJ/kg (10,8 kWh/kg)


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Basic fuel propertiesEmissions

Complete combustion (of natural fuels)

C CO2, H H2O

In air we exhale the concentration of CO2 is ~4 vol. %. Emissions from

complete combustion are “not problematic”.

Emissions of uncomplete combustion are far more problematic. Real

combustion processes are sources of all kind pollutants (also from

biofuels):

• unburned volatiles (organic matter)

• PAH polycyclic aromatic carbohydrates (benzene clusters)

• dust particles PM10, PM2.5

• nanoparticles (PM0.01) – still not discussing about them, because we are

not able to measure or control them…more problematic than PM2.5

• mercury Hg, other heavy metals

• NOx, CO

• SO2 – now mostly under control with desulfurization units

• in case of waste burning the input is less known so the harmful emissions

can be higher


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Basic fuel propertiesEmissions

Damage costs EUR/kg

pollutant


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Biofulesgenerations

1st generation: from food – wheat, corn, rapeseed, soybeans, sugar

cane, palm oil,…

2nd generation from crop residues, bio waste, BMW – Biodegradable

Municipal Waste

3rd generation: from other things which are not competing for arable

soil, algae

4th generation: second generation of 2nd and 3rd generation


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Biofulesgenerations

4th generation: second generation of 2nd and 3rd generation


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BiofulesCO2 emissions of biofuels

Why biofuels – to reduce CO2 emissions?


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BiofulesCO2 emissions of biofuels

Why biofuels – to reduce CO2 emissions?

Slovenia farmer’s earn for wheat in 2019 – 180 EUR/t


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Biofulesto reduce global CO2 emissions!


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ERoEI or EROIEnergy Recieved over Energy Invested or Energy Returned On Invested

Common food production ERoEI ~4!


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Renewable EnergyTransition main obstacles

Is there enough renewable energy (RE) sources on the World?

YES

World consumption in 2015 was ~574 EJ (1 EJ = 1018 J), Sun delivers on

Earth 5.000.000 EJ/year. We need "just" 0.012 % of this?

Main obstacle is that we are not able to store the solar energy for

seasonal periods. Most energies we need (work, heat, light,…) are

“transitional” energies and should be made in real time from some

other energy!


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Renewable EnergyEnergy storage systems


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Renewable EnergyEnergy storage systems


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Renewable EnergyBiofuels production


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Renewable EnergyBiofuels production


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Renewable EnergyBiofuels production in EU

Other liquid biofuelsBiodieselBioethanol

Germany – biodiesel from

rapeseed

France – bioethanol from

grape

500 PJ = 0,5 EJ ~12 Mtoe

this is 23,5 kg of oil equivalent

per European (population in

EU-28 is 507 M)


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Renewable EnergyVision – 100 % transition to RE

Is possible complete transition to RE?

With present technologies probably not? We need radical new

technologies. In a case of renewables we should take care about:

1. the scale of plants,

2. the EROEI,

3. LCA,

4. Is the limit case reasonable/sensible? Or we should drastically

reduce our energy greed?


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Is possible complete transition to RE?

- Wind turbines, large PV fields, large pumped hydro plants – will be

this solutions public acceptable, especially the price of energy

from this plants?

We have the idea how to build large RE (and human controllable

power) heat engine on the heat from surroundings, everlasting

ships,…, but there is always one very high (actualy to high)

"fence" to jump over…


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Are biofuels sensible?

In limited amount – if the EROEI, LCA,

scale of occupied land are sensible, not

competitive with food production, for

advanced scientific research,…


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Will such a transition with high energy prices occur in EU time frame

2055 – abandon of fossil fuels?

Probably not, because the economy growth will stop earlier.

To widen the view of "general" driving forces in thermodynamic

and economic sense, two articles are strongly recommended:

Adrian Bejan: Why we want power: Economics is physics, International Journal of Heat and Mass Transfer, 55 (2012), pp. 4929–4935

Antonio Garcia-Olivares, Jordi Sole: End of growth and the

structural instability of capitalism - From capitalism to a

Symbiotic Economy, Futures, 68 (2015), pp. 31–43


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Momentarily the transition to "green future" is pointed to the economy

growth than to Earth rescuing!


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Biofuels

Discussion


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dr. andrej senegačnik - best ljubljana · dr. andrej senegačnik 5 /44 energy and human - food:...

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