Energy Management :: 2007/2008
Class # 2P
Energy Transformation
João Parente
[email protected]
Energy Management
Types of Energy
The energy transformation processes are countless and there are several energy sources
and types.
Within this course we propose to divide the energy in four main types, based on the energy
t
transformation
f
ti chain:
h i
‰ Primary energy
‰ Final energy
‰ Useful energy
‰ Productive energy
Class # 2P :: Energy Transformation
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Energy Management
Types of Energy
Primary Energy
The primary energy can be defined as the “real” source of energy - before any transformation by
mankind. Primary energy can assume the shape of renewable energy, fossil energy, or result from the
use of residues (e.g., solar energy, oil, natural gas, ...).
Taking the final energy as a reference point, the primary energy results from the summing up to the
fi l energy off allll energy “l“loses”” (d
final
(degradation)
d ti ) associated
i t d tto th
the process off ttransformation
f
ti off primary
i
energy into final energy.
EPrimary = EFinal + ETransformation + ECapital
TOE (Tone of Oil Equivalent) Primary Energy Unit
Th tone
The
t
off oilil equivalent
i l t (toe)
(t ) is
i the
th world
ld reference
f
primary
i
energy unit,
it as it is
i th
the JJoule
l (J) ffor th
the
final energy.
conversion to tep = (Primary
(
Energy / Final Energy))
Considering that the reference technology is based on crude oil. In practice, toe corresponds to an
hypothetic crude oil that during combustion releases a corresponding heat to 10 Gcal/ton (41.9 GJ/ton;
0,086 kgep/kWh).
Class # 2P :: Energy Transformation
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Energy Management
Types of Energy
Final energy
Final energy is defined as the commercial form of energy, in the way that this is available to the
final consumer (e.g., gasoline, electricity, hydrogen, ...). Final energy is obtained through the
transformation of primary energy resources.
Although
g the reference unit for final energy
gy is Joule ((J),
), the pphysical
y
unit for final energy
gy used in
practice depends on the form that the final energy assumes - kWh for electricity, litres for
gasoline, m3 for natural gas, kg for fuel-oil, ...
Conversion to Joule (J)
For the electricity the amount of final energy can be obtained by a direct unit equivalence:
1 kWh = 1 k(J/s)* h = 1 k(J/s) * 3600s = 3600 kJ
In fuels, the final energy is evaluated based on the energy released in the combustion of that fuel,
i.e., based on the heating values of the fuel. Whenever the fuel contains hydrogen (as in all
hydrocarbons) two heating values are usually presented in literature: the Higher Heating Value
((HHV),
), and
a d the
t e Lower
o e Heating
eat g Value
a ue ((LHV).
) For
o ppropane
opa e wee have
a e LHV = 46000
6000 kJ/kg
J/ g and
a d HHV =
50400 kJ/kg.
Class # 2P :: Energy Transformation
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Energy Management
Types of Energy
Useful Energy
Useful energy is directly related to the way that the consumer assimilates the final energy, and it
is the result from the transformation of the final energy into an energy service.
service (e
(e.g,
g lighting,
lighting
heating, transport, communication…).
For example, useful energy can assume the following forms: light, heat, movement, …
Productive energy
The productive energy corresponds to the portion of useful energy that is actually used by the
final consumer, i.e., the concept of productive energy reports directly to the efficiency of the
energy use.
It should be highlighted that the concept of productive energy is somehow subjective, and closely
related to the concepts of productivity/comfort.
Class # 2P :: Energy Transformation
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Energy Management
Energy transformation
Sankey Diagramm
Supplly
Energy Transformation:
Primary energy
ƒ Dams, thermal power stations, wind mills, ...
ƒ Refineries,
R fi i …
ƒ Fuel transport, electricity networks, …
Primary energy degradation
Energy conversion:
Final energy
gy
ƒ Internal combustion engines, ...
ƒ Lamps, …
ƒ Heaters, …
Demand
Final energy degradation
Energy use
Useful energy
Waste energy
Productive energy
Class # 2P :: Energy Transformation
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Energy Management
Energy transformation
Example – Reading light
Supplly
Energy transformation:
100%
Natural gas
ƒ Drilling
ƒ Combined
C bi d cycle
l
ƒ Electricity transport
45%
Heat, …
Energy Conversion:
Electricityy
55%
ƒ Lamps
90%
Demand
Heat, invisible radiation
Energy use
5,5%
Light
50%
Light absorbed by the walls
2,75%
Class # 2P :: Energy Transformation
Reading light on the book
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Energy Management
Energy Transformation
Example – Transport from home to IST
Supplly
Energy transformation:
100%
Oil
ƒ Extraction
ƒ Refinery
R fi
ƒ Fuel transport
5%
Heat, …
Energy conversion:
Gasoline
95%
ƒ Internal combustion engine
70%
Demand
Heat, …
Energy use
66%
Movement
20%
Trafic jam, …
13%
Class # 2P :: Energy Transformation
Transport from home to IST
Slide 8 of 53
Energy Management
Types of Energy
Examples of conversion coefficients to TOE
Electricity
0.29 kgoe/kWh
Thick fuel-oil
0.969 toe/ton
Propane
1.140 toe/ton
Natural gas
0.82 toe/103 m3
Diesel
0 872575 toe/m3
0.872575
Marginal
g
Consumption
p
Concept
p
The concept of marginal consumption implies that the increment in the energy demand (ΔE) is supplied by the
power source with the lower energy conversion efficiency
efficiency, since remaining power sources are already in used at
maximum supply rate to fulfill the actual energy demand (E).
Class # 2P :: Energy Transformation
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Energy Management
Energy transformation
Examples of efficiency values in the transformation of final into useful energy
Production
Consumption ‐ Degradation
η=
=
Consumption
Consumption
ƒ
ƒ
ƒ
ƒ
ƒ
ƒ
Electrical resistence
Electric motor
Boiler
Fluorescent lamp
Internal combustion engine
g
Incandescent lamp
Class # 2P :: Energy Transformation
~ 100%
~ 90%
~ 85%
~ 50%
~ 35%
~ 5%
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Energy Management
Energy transformation
Examples of efficiency values in the transformation of final into useful energy
HEAT PUMP
Oil
Heat
COP =
Electricity consumptio n
COP – Coeficient of Performance
Elect
Elect.
Heat
• Industrial heat pump COP ~ 5
• Residential heat pump COP ~ 3
Class # 2P :: Energy Transformation
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Energy Management
Energy transformation
Problems
Class # 2P :: Energy Transformation
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Energy Management
Energy transformation
PROBLEM 01
Considering that the Portuguese electricity production sector is characterized by the following data:
1)
2)
3)
Electricity losses in the network ~ 10%
Efficiency of the worst power plant (gas turbine) ~ 33%
Average effiency of the thermal power stations ~ 45%
Determine the conversion coefficient form final energy
energy, in the form of electricity
electricity, to primary energy in the
units of kgoe/kWh, considering:
1) average values for the electricity production
2) the concept of marginal consumer.
consumer
Source
Hydro
23.38%
Thermal
70.47%
Wind
5.96%
Geothermal
0.17%
Photovoltaics
0 01%
0.01%
TOTAL
Class # 2P :: Energy Transformation
Contribution
100%
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Energy Management
Coeficientes de conversão para tep
SOLUTION P02
1) Marginal consumer:
Th transformation
The
t
f
ti efficiency
ffi i
off primary
i
energy iinto
t final
fi l energy iis:
ηG = ηPS * ηEN = 33% * (100% - 10%) = 30%
Considering 1kWhFE of final energy (elecricity):
Æ Primary energy = 1 / ηG = 3,33 kWhPE (or 0,3 kWhFE/kWhPE )
= 3,33 kWhPE * 0,086 kgoe/kWhPE = 0,28 kgoe
((1 kgoe
g = 41,9 MJ = ((41,9*103 kJ)) / ((3600 kJ/kWh)) = 11,64 kWh => 0,086 kgoe/kWh)
g
)
Æ Conversion coef. = PE / FE = 0,29 kgoe / 1 kWhFE = 0,29 kgoe/kWhFE
FE – Final Energy; PE - Primary Energy
Class # 2P :: Energy Transformation
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Energy Management
Coeficientes de conversão para tep
SOLUTION P02
2) Using the average production efficiencies:
The transformation efficiency of primary energy into final energy is:
ηG = ηTPP * ηEN = 45% * (100% - 10%) = 40% - for thermal power plants
ηG = ηREN * ηEN = 100% * (100% - 10%) = 90% - for renewables
Considering 1kWhFE of final energy in both cases:
Æ PE = 1 / ηG = 2,5 kWhPE * 0,086 kgoe/kWhPE = 0,22 kgoe - for thermal power plants
Æ PE = 1 / ηG = 1,11 kWhPE * 0,086 kgoe/kWhPE = 0,095 kgoe - for renewables
Æ Conversion coef. = PE / FE = 0,22 kgoe / 1 kWhFE = 0,22 kgoe/kWhFE - for thermal power plants
Æ Conversion coef. = PE / FE = 0,095 kgoe / 1 kWhFE = 0,095 kgoe/kWhFE - for renewables
Æ Average
A
conversion
i coef.f
Class # 2P :: Energy Transformation
= (0,095*29,5%)
(0 095*29 5%) kgoe/kWh
k /kWhFE + (0,22*70,5%)
(0 22*70 5%) kgoe/kWh
k /kWhFE
= 0,183 kgoe/kWhFE
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Energy Management
Energy transformation
PROBLEM 02
Considering that you need to heat a house, and that you have 3 different solutions available.
1)
2)
3)
Electric heating by Joule effect;
Propane Boiler central heating;
Air heating using an heat pump;
Consider: 0.075 €/kWhe, 0.5 €/kgpropane, PCIpropane = 46 MJ/kg
Determine the ranking list for these solutions in terms of: Final energy consumption, Primary energy
consumption and cost. Support your calculation with the Sankey diagram.
Class # 2P :: Energy Transformation
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Energy Management
Energy transformation
SOLUTION P02
Supplly
Energy transformation:
ƒ Electricity 0.29 kgoe/kWh
ƒ Propane
P
11.14
14 kkgoe/kg
/k
x1 kgoe
x2 kgoe
x3 kgoe
100%
Transformation losses
Energy conversion:
ƒ Electrical resistances η = 100%
ƒ Boiler η = 85%
ƒ Heat pump COP = 3 (η = 300%)
x1 kWh (electricity)
x2 kWh (p
(propane)
p )
x3 kWh (electricity)
Demand
Conversion losses
Energy use:
1kWh of heat (for 1,2 e 3)
ƒ Heating
Losses trough the building envelope…
Useful area at the confort temperature (T = 21ºC ?)
Class # 2P :: Energy Transformation
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Energy Management
Energy transformation
SOLUTION P02
For all solutions: EU = 1 kWhth
1)
Electric heating by Joule effect: η ~ 100%, EF = 1/η = 1 kWhe/kWhth
EP = EF * 00.29
29 kgoe/kWh
k /kWhe = 1 kWhe/kWhth * 00.29
29 kgoe/kWh
k /kWhe = 0.29
0 29 kgoe/kWh
k /kWhth
Cost = EF * 0.075 €/kWhe = 1 kWhe/kWhth * 0.075 €/kWhe = 0.075 €/kWhth
2)
Propane Boiler central heating: η ~ 85%, EF = 1/η = 1.18 kWhp/kWhth
mp = EF / LHV = (1.18 kWhp/kWhth * 3600 kJ/kWh) / 46 000 kJ/kg = 0.092 kg/kWhth
EP = mp*1.14 kgoe/kg = 0.092 kg/kWhth * 1.14 kgoe/kg = 0.10 kgoe/kWhth
Cost = 0.5€/kg * mp = 0.5€/kg * 0.092 kg/kWhth = 0.046€/kWhth.
3)
Air heating using an heat pump: η ~ 250%, EF = 1/η = 0.4 kWhe/kWhth
EP = EF * 0.29 kgoe/kWhe = 0.4 kWhe/kWhth * 0.29 kgoe/kWhth = 0.12 kgoe/kWhth
Cost = EF * 0.075 €/kWhe = = 0.4 kWhe/kWhth * 0.075 €/kWhe = 0.03 €/kWhth
Prefernce in terms of Final
Energy
Class # 2P :: Energy Transformation
Prefernce in terms of
Primary Energy
Prefernce in terms of
Energy Cost
1st Heat Pump
1st Boiler
1st Heat Pump
2nd Eletric resistances
2nd Heat Pump
2nd Boiler
3rd Boiler
3rd Eletric resistances
3rd Eletric resistances
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