Primary Energy Demand of Renewable Energy Carriers
Part 1: Definitions, accounting methods and their
applications with a focus on electricity and
heat from renewable energies
Primary Energy Demand of Renewable Energy Carriers – Part 1:
Definitions, accounting methods and their applications with a focus on electricity
and heat from renewable energies
A cooperation of:
April 2014, commissioned by the European Copper Institute
Authors:
Alexander Stoffregen
Dr. Oliver Schuller
Hauptstraße 111 – 113
70771 Leinfelden – Echterdingen
PE INTERNATIONAL AG
2
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Fax
+49 711 341817 – 0
+49 711 341817 – 25
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www.pe-international.com
1
Introduction
Energy related discussions and policy making, such as defining energy saving targets or energy
efficiency measures, are often based on primary energy values. These values express the energy
consumption of a country, or the energy demand of a system, service or product in primary energy units. They are often published by international and national energy statistics, energy scenarios/outlooks, or environmental assessments, however there is a potential for inconsistency in how
these primary energy values are determined.
Primary energy values taken from different energy statistics and studies may sometimes be compared without considering possible influences from different definitions and methodologies used
for primary energy. Recent studies have raised awareness about the influence of different methods to determine primary energy consumption from renewable energy sources in energy statistics. In Moomaw (2011) and Macknick (2011) the differences in energy statistics and energy outlooks/scenarios that occur, due to the different methods and definitions, are highlighted as well
as the challenges faced in comparing these different accounting methods. In addition, Harmsen
(2011) investigated the impact of different methods on energy saving targets in Europe.
The method for calculating the primary energy of fossil fuels is clear and consistent (as described
in chapter 3). In contrast, primary energy factors for electricity or heat generated from renewable
energies, waste, nuclear energy, or imported electricity are not calculated according to a single
consistent methodology. Instead, several approaches are available and used in practice. Figure 1
presents an overview of the different energy sources used to generate electricity. Waste is a
unique case as it can be considered to be either a renewable energy source, a fossil energy
source, or a mixture of both depending on its specific characteristics. Heat generation uses the
same energy sources as electricity generation, with the exception of hydro and wind energy.
Non-renewable energy sources
Combustibles
•
•
•
•
•
•
•
Hard Coal
Coal gases
Lignite
Peat
Oil based fuels
Natural gas
Waste (fossil part)
Renewable energy sources
Non-combustibles
•
Nuclear
Combustibles
Non-combustibles
• Biomass (solid,
liquid, gaseous)
• Waste (biogenic
part)
• Hydro (storage, runof-river, tide, wave
and ocean)
• Wind
• Solar (photovoltaic,
solar thermal)
• Geothermal
Figure 1: Renewable and non-renewable energy sources used for electricity generation (not
exhaustive)
This paper is the first part of a two paper series commissioned by the European Copper Institute.
It addresses the different primary energy definitions, accounting methods, and their applications
with a focus on electricity and heat generation from renewable energy. In addition to renewable
energy sources, primary energy factors for electricity from waste, nuclear, and imported electricity are also discussed as these can be calculated in different ways. In the second part of the study,
“Primary Energy Demand of Renewable Energy Carriers – Part 2 Policy Implications,” conducted
by ECOFYS (2014), the application of primary energy factors (PEF) in the three EU Directives - Energy Performance of Buildings Directive (EPBD), Energy Efficiency Directive (EED) and Renewable
Energy Directive (RED) is discussed.
3
2
Definitions
In Nakicenovic (1996), primary energy is defined as:
The energy that is embodied in resources as they exist in nature: the chemical energy embodied in fossil fuels or biomass, the potential energy of a water reservoir, the electromagnetic energy of solar radiation and the energy released in nuclear reactions.
Similar or adapted definitions of primary energy can be found in publications dealing with energy
statistics, energy economics, or environmental assessments. They all define combustible fossil
fuels such as coal, oil, and natural gas extracted from a stock of finite resources, as primary energy.
The conversion efficiencies for steam power plants, heat plants, combined heat and power (CHP)
plants, or residential heating systems using combustible energies are determined based on the
ratio between produced electricity and/or heat, and input of energy (amount of fuel multiplied
with calorific value) as outlined in Formula 1. In the context of renewable energy carriers in energy statistics, the expression primary energy equivalent is used instead of efficiency.
Formula 1: Calculation of power plant efficiencies using combustibles
𝑬𝑬𝑬𝑬𝑬𝑬𝑬𝑬𝑬𝑬𝑬𝑬𝑬𝑬𝑬𝑬𝑬𝑬𝑬𝑬 = 𝑪𝑪𝑪𝑪
𝑶𝑶𝑶𝑶𝑶𝑶𝑶𝑶𝑶𝑶𝑶𝑶𝒕𝒕
𝒇𝒇
𝒙𝒙 𝑰𝑰𝑰𝑰𝑰𝑰𝑰𝑰𝑰𝑰𝒇𝒇,𝒕𝒕
CF f = calorific value of a fuel
Input f, t = Input of fuel per operation time
Output t = Output of electricity and/or heat per operation time
Hence, primary energy factors are the quotient of primary energy input to energy (electricity/heat) output, i.e. the reciprocal value of the conversion efficiency as shown in Formula 2.
Formula 2: Calculation of primary energy factor (PEF)
𝑷𝑷𝑷𝑷𝑷𝑷 =
𝑪𝑪𝑪𝑪𝒇𝒇 𝒙𝒙 𝑰𝑰𝑰𝑰𝑰𝑰𝑰𝑰𝑰𝑰𝒇𝒇,𝒕𝒕
𝑶𝑶𝑶𝑶𝑶𝑶𝑶𝑶𝑶𝑶𝑶𝑶𝒕𝒕
CF f = calorific value of a fuel
Input f, t = Input of fuel per operation time
Output t = Output of electricity or heat per operation time
These definitions are relatively straightforward to use if the primary energy demand or primary
energy factor (PEF) of a fossil power plant needs to be calculated for the supply of secondary energy, e.g. electricity. Assuming a conversion efficiency of 40% for a fossil power plant, 2.5 MJ of
primary energy is needed to provide one MJ of electricity (PEF = 2.5). Similarly, for electricity from
biomass and waste, the primary energy factor can be calculated in the same way as for fossil
fuels.
For electricity and heat from non-combustible renewable energy or nuclear energy, several methodologies to account for primary energy and to calculate the primary energy factors have been
developed and applied. These are listed in Table 1. The same holds true for electricity and heat
from co-generation, as the primary energy has to be partitioned (allocated) to two different products (heat and electricity) for which different methodologies exist.
4
Table 1: Options to account primary energy for electricity and heat generation from noncombustible energy sources
No.
Option
Type of primary energy
1
The primary energy factor for electricity or heat from non-combustible renewables (hydro, wind, solar, geothermal) is accounted as zero by definition, e.g. 0
MJprimary energy per 1 MJelectricity
Primary energy equivalents are used to calculate the primary energy of noncombustible energies (renewable energies excl. biomass) and the special case
of nuclear energy.
The primary energy factor for electricity or heat from renewables only accounts the fossil primary energy that was necessary to produce construction
materials for the infrastructure (e.g. hydropower stations, wind turbines,
photovoltaic cells, solar thermal power plants, and geothermal power plants)
including fuels for transport and auxiliary materials during operation. For
electricity from nuclear energy, the consumed fuel is also accounted as nonrenewable primary energy using a technical conversion efficiency or a primary
energy equivalent.
The primary energy factor is split up into fossil primary energy (e.g. infrastructure, conversion of nuclear energy) and renewable primary energy using primary energy equivalents or efficiencies for the conversion of renewable energy sources into electricity or heat.
Not applicable
2
3
4
Accounting for (total) primary
energy
Split up into non-renewable
(fossil) and renewable primary
energy.
Accounting for non-renewable
(fossil) primary energy ONLY
Split up into non-renewable
(fossil) and renewable primary
energy.
Accounting for non-renewable
(fossil) AND renewable primary
energy.
The methodology for Option 1 is straightforward, as the primary energy is, by definition, always
zero for non-combustible, renewable energy sources. Option 2 uses so-called primary energy
equivalents to calculate the primary energy of the generated electricity or heat without further
differentiation into renewable or non-renewable (fossil) primary energy.
For Options 3 and 4, the system boundaries are different compared to Options 1 and 2, as the
primary energy that is needed, for example to produce and transport construction materials or
auxiliary materials, is included. In these cases, electricity or heat from non-renewable or renewable combustible energy is considered, as well as the primary energy necessary to extract, cultivate, transform, and transport the fuels. The enlargement of the system boundaries takes into
account that, depending on the energy source, the build-up of infrastructure and the supply of
fuels may be of relevant from an environmental perspective.
A second aspect considered within Option 3 and 4, is that the usage of renewable energy sources
for electricity or heat supply should be assessed, or accounted in a different way than finite, nonrenewable energy sources. An aggregated primary energy factor that includes renewable and
non-renewable primary energy has no value for the assessment of the consumption of finite energy resources. A comparison of such primary energy factors may even be misleading, as the absolute magnitude of primary energy factors, especially for electricity from renewable sources, can
be much higher due to lower technical conversion efficiencies or assumed primary energy equivalents.
For that reason, Options 3 and 4 split primary energy into primary energy from renewable sources
(e.g. hydro, wind, solar, geothermal and biomass) and non-renewable sources (nuclear and fossil
fuels). For municipal solid waste, energy statistics often account 50% of the primary energy that is
converted in the waste incineration plant as non-renewable (fossil) energy, and 50% as renewable
primary energy. In addition, primary energy associated with the construction of the incineration
5
infrastructure and the production of operating materials is accounted for as non-renewable (fossil) primary energy.
In Option 3, only the non-renewable (fossil) primary energy that is needed to supply the necessary
infrastructure to produce electricity from renewable sources or to produce biomass (e.g. diesel
for machinery or energy for infrastructure) is accounted for by standardized methods following a
life cycle thinking approach, such as life cycle assessment (ISO 14040/44). Numerous studies and
databases exist, from which the primary energy demand can be taken.
Option 4 also includes, in addition to Option 3, the primary energy of the renewable sources
themselves that are used to generate the electricity, i.e. primary energy equivalents or conversion
efficiencies are used to determine the renewable primary energy for electricity generation from
renewable energy sources. For biomass, the calorific value is used to determine the renewable
primary energy of the combusted fuel, i.e. photosynthesis of solar energy into biomass is not accounted for (as in all options and methods described within the paper). In the case of nuclear
power, the primary energy is accounted for as non-renewable (fossil) primary energy. Finally, for
electricity from waste, the primary energy is often accounted with the 50:50 approach for the
conversion as described above.
Unlike biomass plants where the input of fuel and the generated electricity are measured similarly
to fossil fuel plants, only the output of electricity is measured in non-combustible power plants
using renewable energies (e.g. hydro power stations, wind turbines, photovoltaic cells etc.) or
nuclear energy. In theory, the primary energy equivalence for electricity from technology such as
wind turbines can be determined by using a technical conversion efficiency for the generator that
converts the kinetic energy of the wind into electricity. In practice, several conversion efficiencies
would have to be determined for renewable energy carriers and nuclear energy that would depend upon climatic conditions, technologies used, and overall system integration. Instead, standardized (not technology, climate specific etc.), primary energy factors are used for electricity or
heat generation. The methods for the conversion from primary energy to electricity are described
in the following chapter.
6
3
Methods to calculate primary energy equivalents or conversion
efficiencies
Various methods are available to account for the primary energy of renewable energy sources
and nuclear energy in national, and international, energy statistics, politics, and regulations. In all
methods the primary energy for electricity generation from combustible fuels, such as biomass
and waste, is calculated based on the calorific value of the fuel and the amount of fuel required to
generate a given unit of electricity or heat (analogous to fossil fuels). The approaches differ in
how they account for the primary energy of non-combustible energy sources.
Zero equivalent method
Although rarely used in practice, it is thinkable to account no primary energy at all for the generation of electricity or heat from renewable energy sources, i.e. 1 MJ of electricity from wind equals
0 MJ of primary energy. This approach is sometimes used if renewable energy carriers are recovered from residues, such as sewage gas or landfill gas (AGFW 2010). Consecutively, this approach
is called the “zero equivalent method” in this paper.
Direct equivalent method
The direct equivalent method uses a primary energy equivalence of 100% between primary energy
and electricity or heat for all non-combustible renewable energy sources (e.g. hydro, wind, solar,
geothermal) and nuclear energy, i.e. 1 MJ of electricity from wind equals 1 MJ of primary energy
from wind energy (Grubler 2012). The same holds true for heat, i.e. 1 MJ of heat from solar thermal or geothermal energy equals 1 MJ of primary energy. For all combustible renewable energy
sources, e.g. biomass or waste, the direct equivalent method is not applied, as the primary energy
necessary to produce a unit of electricity or heat can be directly accounted for by measuring the
input mass and calorific value of the biomass or waste.
Physical energy content method
The physical energy content method is based upon the definition that primary energy “should be
the first energy form downstream in the production process for which multiple energy uses are
practical” (IEA 2004). For biomass, which can be used in multiple forms (e.g. conversion to biofuels, food, and firewood) the primary energy to produce electricity can be directly accounted for by
measuring the input mass and calorific value of the biomass. For energy sources such as wind and
hydro (including storage, run-of-river, tide, wave and ocean) the first practical use is the electricity
itself. As a consequence, an efficiency of 100% is assumed for these energies. The same applies
for electricity from solar photovoltaic.
For those energy sources that are first transformed to heat, the heat is defined as the first usable
energy, and therefore the energy content of the heat needed to produce a unit of electricity is
accounted as primary energy. Examples of these energy sources include geothermal, nuclear, and
solar thermal. The conversion efficiencies used for the transformation of heat into electricity may
vary among energy statistics that use the physical energy content method. For example, the physical energy content method for geothermal energy distinguishes between heat as a primary energy taken from the environment and heat as a secondary energy carrier that is available for final
use. The difference is determined by a conversion efficiency, or primary energy equivalent in the
same way as for electricity. However, in cases such as statistics from the International Energy
7
Agency (IEA) or Eurostat, this conversion efficiency is five times higher in value, i.e. 50% for heat
compared to 10% for electricity from geothermal. Electricity or heat from a geothermal CHP plant
would be considered in the same way.
Substitution method
In the substitution method, as it is used by the U.S. Energy Information Administration (EIA), primary energy is defined as “energy in the form that it is first accounted for in a statistical energy
balance, before any transformation to secondary or tertiary forms of energy” (EIA 2013A). In contrast to the definition of primary energy in the physical energy content method, a determination
of the required kinetic energy per MJ of electricity from a wind turbine would be necessary under
this definition. To avoid the challenges of determining the technical conversion efficiencies of
non-combustible renewable energy sources, the substitution method uses the conversion efficiencies of the fossil fuel plants that were substituted by the electricity from renewable energies
or that would be required to replace the electricity (Grubler 2012). In the case of heat production,
similarly to electricity generation, the conversion efficiency of the fossil fuel heat plant is used
that was substituted by the heat from renewable energies. In the case electricity and heat are
produced from co-generation, the individual conversion efficiencies of the substituted electricity
and heat are used in the same way.
Technical conversion efficiencies
Technical conversion efficiencies provide a further method for determining the primary energy of
electricity generation from non-combustible energy sources. A method to calculate technical conversion efficiencies for electricity generation is defined by the VDI standard 4600 (VDI 1997) for
cumulative energy demand calculations. In this standard, primary energy is defined as the “energy
content of energy carriers that have not yet been subjected to any conversion”. As a consequence,
the cumulative energy demand method uses the technical conversion efficiency between energy
source and generated electricity or heat, to calculate the primary energy demand per unit of energy generated. Table 2 summarises the calculation approach for technical conversion efficiencies
for electricity generation according to VDI 4600.
Table 2: Calculation of technical conversion efficiencies for electricity generation in VDI 4600
Energy source
Calculation of conversion efficiency
Hydro
Ratio of net electricity generated to potential energy of water defined by height of fall and
amount of water used per time period.
Wind
Ratio of net electricity generated to kinetic energy that passes the rotor area per time period.
Solar photovoltaic
Ratio of net electricity generated to the solar energy radiated on the gross area of the photovoltaic modules per time period.
Waste
Net calorific value of waste and amount of fuel used to calculate conversion efficiency (analogous to fossil fuels).
Biomass
Net calorific value of biomass and amount of fuel used to calculate conversion efficiency (analogous to fossil fuels).
Nuclear
33% used as default value (German average).
8
The calculation of technical conversion efficiencies for non-combustible energy sources depends
on a multitude of factors, such as applied technologies and climatic conditions. Last but not least,
it also depends on the availability of data and assumptions. For wind power, as an example, the
efficiencies for the rotor, gear, and generator assemblies, which depend on technology and local
conditions, have to be combined to give an overall conversion efficiency. The technical conversion
efficiency for heat from solar thermal can be calculated as the ratio of usable heat generated to
the solar energy radiated on the gross area of the solar collector.
Primary energy factors for heat or electricity from co-generation using technical conversion efficiencies can be calculated by several approaches. The simplest way is the proportionality approach used by the IEA (2013B). The approach assumes the conversion efficiency for heat and
electricity to be the same, which leads, especially if the CHP plant has a high heat share, to an
overstated efficiency for the electricity production and an understated efficiency for the heat
production. The fixed-heat-efficiency approach tries to overcome this shortcoming by using a
fixed efficiency for the produced heat in a CHP plant, for example 90% (IEA 2013B). By subtracting
the necessary primary energy for the heat, using the fixed efficiency, from the overall primary
energy input, the efficiency for the electricity generation can be calculated.
A further method to account primary energy for heat and electricity production from cogeneration using technical conversion factors, is the usage of allocation as often used in life cycle
assessments (ISO 14040 and ISO 14044 2006). The primary energy (and the resulting environmental impacts) are portioned between the electricity and heat based on allocation procedures “that
reflects the underlying physical (or other) relationships between them” (ISO 1044 2006). These
relationships may be the calorific value of the products (which would result in the proportionality
approach), exergy content, or economic value. More information on the different approaches is
given in (Fritsche 2008, EC 2010, IEA 2013B, Mauch 2010).
The applied methods for the different options are summarised in Table 3 below.
9
Table 3: Methods used to determine the primary energy factors for electricity generation from
different energy sources
Option 1
Type of primary energy
Methods for primary energy factors
(Total)
primary
energy
System boundary
Energy
conversion
only
NonCombustibles n.a.
renewable (e.g. coal, oil)
Noncombustible
(e.g. nuclear)
Option 2
Option 4
(Total) primary energy
Non-renewable Non-renewable and
primary energy renewable primary energy
Energy conversion only
Entire supply
chain
• Technical conversion
efficiencies
Supply of fuels/infrastructure based on life cycle
approach. For conversion:
• technical conversion efficiencies
Supply of fuels/infrastructure based on life cycle
apprach. For conversion:
• technical conversion efficiencies
• physical energy content method
Primary energy equivalents:
• direct equivalent
method
• physical energy content
method
Renewable Combustibles Zero equiva- • Technical conversion
(e.g. biomass, lent method efficiencies
waste)
Non –
combustible
(e.g. hydro,
wind, solar,
geothermal)
Option 3
Primary energy equivalents:
• direct equivalent
method
• physical energy content
method
• substitution method
10
Supply of fuels/
infrastructure
based on life
cycle approach.
Entire supply chain
Supply of fuels/infrastructure
based on life cycle approach.
For conversion:
• technical conversion efficiencies
Supply of fuels/infrastructure
based on life cycle approach.
For conversion:
• technical conversion efficiencies
• physical energy content
method
4
Application of methods in practice
As stated in Chapter 3, the method to use zero as the primary energy factor for electricity from
renewable energy has no practical relevance but is sometimes used to calculate primary energy
factors if heat is generated from residue based energy carriers (e.g. sewage gas or landfill gas).
The direct equivalence method, the physical energy content method, and the substitution method
are all used to calculate primary energy equivalents in energy statistics and fall under option 2 of
the methods for calculating primary energy factors for electricity generation from noncombustible energy sources. The direct equivalent method is used by statistics of the United Nations, UN statistics (2013) and reports of the Intergovernmental Panel on Climate Change (IPCC)
dealing with future energy and climate scenarios. The physical energy content method is used in
energy statistics of the International Energy Agency (IEA), Eurostat and the Organisation for Economic Cooperation and Development (OECD) (IEA 2004). An estimated average conversion efficiency of 33% between heat and electricity for nuclear power station is used (IEA 2004 and
2012A) and refers to the average European plant. For solar thermal electricity technologies, a
global efficiency of 33% is used for the transformation of heat into electricity, a 10% conversion
efficiency for electricity from geothermal energy and a conversion efficiency of 50% for usable
heat from geothermal energy (IEA 2012A and 2013B).
The substitution method is applied by the U.S. Energy Information Administration (EIA 2013), the
Netherlands (Te Buck 2010), and BP (BP 2013). The EIA uses the conversion efficiency of the average fossil-fuel power plant to determine the primary energy of electricity from non-combusted
renewable energy sources.
For electricity imported to a country, all considered energy statistics use a primary energy equivalent of one MJ primary energy per imported MJ of electricity (IEA 2012B, EIA 2013A), even though
they apply the different accounting methods for domestic electricity production.
Technical conversion efficiencies for non-combustible renewable energy sources as described for
option 4 are often applied in life cycle assessments (LCA) analyses. The concept of LCA is widely
used internationally and within the European Commission to assess the environmental impacts of
products, processes, and services along the life cycle. The supply of electricity or heat is an important factor in many LCAs, as electricity or heat consumption of manufacturing processes or
products’ use phases (e.g. driving a vehicle) can be a major contributor to the overall environmental performance of a product or service. Typically within an LCA, emissions released, waste generated, and resources consumed (including primary energy demand) are analysed. In contrast to
energy statistics, in which energy consumption is calculated for entire countries or regions and
disaggregated into sectors, a LCA focuses on a product, process, or service. This includes the entire supply chain of a single product such as electricity or heat; including, extraction and transport
of fuels, manufacturing, and installation of transformation infrastructure (e.g. hydro power stations, wind turbines, photovoltaic cells). The ISO standards on Life Cycle assessment (ISO 14040
and ISO 14044 2006) provide a widely accepted methodology and additional guidance is given in
the ILCD handbook (EC 2010), co-developed and published by the European Commission. In LCA
studies, in addition to the technical conversion efficiency method, as described in VDI 4600, the
physical content method, as recommended in the ILCD handbook (EC 2010, chapter 7.4.3.6.1) is
also used. The method in the ILCD handbook only differs from the physical energy content method as applied by IEA or Eurostat energy statistics in that no default values are given for solar
thermal and geothermal electricity generation, as described above.
In LCAs, no distinction is normally made between the primary energy equivalence for domestically
produced or imported electricity. In both cases the above described approaches are used to calcu11
late the primary energy for the supply of electricity. For imported electricity from unspecified
energy sources, the energy mix of the exporting country is used to determine the primary energy
for imported electricity. This leads to more precise results, especially for small countries importing
significant amounts of electricity.
Although no guidance for outlining the primary energy values is given in ISO 14040 or 14044 and
VDI 4600, it is common to split this into renewable primary energy and non-renewable primary
energy. This simplifies the understanding and interpretation of results and avoids misunderstandings, since two different quantities (limited availability of non-renewable or fossil primary energy
and unlimited availability for renewable primary energy) are presented side by side.
A summary of primary energy equivalents for electricity generation applied in the different methods, as well as exemplary technical conversion efficiencies used in LCA, are given in Table 4. It
should be noted that all numbers refer to gross production and direct electricity production.
Combined heat and power is not considered here (see Chapter 2), as the allocation of primary
energy between electricity and heat includes a further dimension that would complicate and obscure the discussion of the main topic.
Table 4: Primary energy equivalents and conversion efficiencies for electricity generation (gross
production) of renewable energy sources
Energy Source
Zero equivalent method
Direct equivalent method (as
applied by UN
statistics)
Physical energy
content method
(as applied by
Eurostat and IEA)
Substitution
method (as applied by US EIA)
Technical conversion efficiencies (as
applied in LCA
databases , e.g.
(GaBi 2012)
Hydro
n.a.
100%
100%
39.7%3
85%
Wind
n.a.
100%
100%
39.7%3
40%
Solar (photovoltaic)
n.a.
100%
100%
39.7%3
13.4%
Solar (thermal
electric)
n.a.
100%
33%
39.7%3
12.4%
Geothermal
n.a.
100%
10%
39.7%3
22.4%
Biomass (solid)
n.a.
28.6%1
Biogas & Bioliquids
n.a.
26.2%1
Waste
n.a.
17.7%2
Nuclear
n.a.
100%
33%
33%
33%
Imported electricity
n.a.
100%
100%
100%
source specific.
i.e. country
specific
1average
European gross efficiency for biomass powered electricity plants (IEA 2012B), reference year 2010
European gross efficiency for municipal solid waste incinerators, producing electricity only (CEWEP 2012)
3substituton via average European fossil power plant for non-combustible renewable energy sources (gross efficiency), calculated by
PE International based on IEA (2012B), reference year 2010
2average
12
5
Example primary energy factors using different methodologies
Based on the various options and methods for calculating primary energy factors for renewable
energy sources, as well as nuclear energy, waste, and imported electricity, Table 5 illustrates the
resulting factors per energy source. All data refer, for better understanding, to gross production
with no downstream losses (transmission and distribution).
Table 5: Primary energy factors for renewable electricity, nuclear electricity, and electricity from
waste following different accounting options (1-4) and calculation methods
Option
1
MJprimary energy /
MJelectricity
System boundary
Zero
equivalent
Option 2
2a Direct
Equivalent
2bPhysical
Energy
Content
Option 3
2c Substitution
Option 4
Only nonrenewable
primary
energy
4a- Technical Conversion Efficiencies
4b - Physical Energy
Content
Nonrenewable
primary
energy
Nonrenewable
primary
energy
(Total)
primary
energy
(Total) primary energy
Nonrenewable
primary
energy
Energy
conversion only
Energy conversion only
Entire
supply
chain
Renewable
primary
energy
Renewable
primary
energy
Entire supply chain
Hydro (storage
power station)
0
1.0
1.0
2.5
0.00355
0.00355
1.2
0.00355
1.0
Hydro (run-ofriver power station)
0
1.0
1.0
2.5
0.0105
0.0105
1.2
0.0105
1.0
Wind
0
1.0
1.0
2.5
0.0325
0.0325
2.5
0.0325
1.0
Solar
(photovoltaic)
0
1.0
1.0
2.5
0.155
0.155
7.5
0.155
1.0
Solar (thermal
electric)
0
1.0
3.01
2.5
0.116
0.116
8.1
0.116
3.01
Geothermal
0
1.0
101
2.5
0.00485
0.00485
4.5
0.00485
101
Biomass (solid
biomass fired
power plant)
0
3.52
0.185
0.185
4.02
0.185
4.02
Biomass (biogas
fired gas turbine)
0
3.82,3
0.185
0.185
112,3
0.185
112,3
Waste
n.a.
5.64
3.24,5
3.24,5
2.94
3.24,5
2.94
Nuclear
n.a.
3.15
3.15
0.0
3.11,5
0.0
1.0
3.01
3.0
1default
primary energy equivalents from IEA (2012A) used for physical energy content method
average European efficiency for biomass or biogas powered electricity plants (IEA 2012B), reference year 2010
3in Option 2 the net calorific value of the biogas is used, in Option 4 the net calorific value of the biomass used to produce biogas is
used
4aveage European efficiency for municipal solid waste incinerators producing electricity only (CEWEP 2012), 50% of fuel (waste) accounted as renewable and 50% as non-renewable primary energy
5Primary energy factors for fuel supply and infrastructure taken from the professional Life Cycle Assessment (LCA) database, developed
and annually updated by PE International (GaBi (2012)),
6Heath 2011
2
13
Where primary energy factors are calculated based on primary energy equivalents (option 2), as
used in energy statistics, some misleading interpretations could result if electricity supplies from
different energy sources are compared. Electricity from biomass and, within the physical energy
content method, also renewable energy sources that derive electricity from heat (e.g. geothermal
and solar thermal) have, by definition, primary energy factors that are several times higher than
those associated with electricity from wind, hydro or photovoltaic generation. Also, as no differentiation is made between non-renewable and renewable primary energy, electricity from biomass would, in most cases, have a higher primary energy factor than electricity from fossil fuels,
due to its lower conversion efficiencies.
The values for the non-renewable primary energy factors for option 3 and 4, presented as an example in Table 5 and 6, are taken from the professional Life Cycle Assessment (LCA) database,
developed and annually updated by PE International (GaBi (2012)). For electricity from renewable,
non-combustible sources, like wind or hydro, the non-renewable primary energy factors contain
the non-renewable primary energy that is necessary to supply the construction materials and to
build-up the infrastructure (e.g. diesel for transport and construction machinery), also referred to
as embedded or embodied energy. For electricity from biomass, the factors contain the primary
energy for cultivation and harvesting (e.g. diesel, fertilizer etc.). For electricity from nuclear energy, the non-renewable primary energy factors contain not only the primary energy to produce the
construction materials, the fuel rods and any auxiliary materials during operation, but also the
consumption of the nuclear fuel itself, calculated based on a technical conversion efficiency or
primary energy equivalent of 33%. For option 3, the selection of the accounting method for primary energy consumption in the conversion process is only relevant for nuclear power. For the
method using technical conversion efficiencies and the physical energy content method, the same
efficiencies have been assumed, therefore no distinction between the two methods has been
made for option 3. For electricity from renewable, non-combustible sources the method is not
relevant, as renewable primary energy is excluded. Finally, for combustible fossil fuels the technical conversion efficiencies are used.
The renewable primary energy factors in option 4 are based on the primary energy equivalents for
the physical content method or the technical conversion efficiencies taken from the professional
Life Cycle Assessment (LCA) database, developed and annually updated by PE International (GaBi
(2012)) as illustrated in Table 4. They also contain a very small part of renewable primary energy
from the production of construction materials and fuel supply chains, in the case renewable electricity or biofuels are used. The separation of primary energy into non-renewable and renewable
components, as done for option 3 and 4 is especially useful when comparing primary energy factors for renewables with those for fossil fuels.
Table 6 presents primary energy factors for average, country-specific electricity supplies. The following countries have been selected as examples:
• Norway – high share of renewable energies for electricity generation (95.9% in 2010
(IEA 2012B))
• Poland – high share of combustible fossil fuels for electricity generation (92.7% in 2010
(IEA 2012B))
• Spain – diverse grid mix (20.5% nuclear power, 33.2% renewables, 46.3% combustible
fossil fuels (IEA 2012B))
Primary energy factors have been calculated for these three countries using all options and methods identified previously. In addition, the primary energy factors for electricity imported from one
of these countries by a neighbouring country are listed. Whereas for option 3 and 4 the factors for
the grid mix and the imported grid mix are identical, under option 2, imported electricity is always
accounted with a primary energy factor of 1.
14
Table 6: Primary energy factors for renewable electricity, nuclear electricity and electricity from
waste following different accounting options (1-4) and calculation methods
Option 1
MJprimary energy /
MJelectricity
System boundary
Imported electricity
– Hydro electricity
Option 2
2b- PhysiZero
2a - Direct
cal Energy
equivalent Equivalent
Content
Option 3
2c - Substitution
Nonrenewable
primary
energy
Option 4
4a- Technical Conversion Efficiencies
(Total)
Primary
energy
(Total) primary energy
Nonrenewable
primary
energy
Energy
conversion only
Energy conversion only
Entire
supply chain
0
1.0
0.00351,2
0.00351,2
1.22
0.00351,2
1.02
0.0861
0.0861
1.25
0.0861
1.1
0.0861,2
0.0861,2
1.252
0.0861,2
1.12
3.01
3.01
0.21
3.01
0.19
3.01,2
3.01,2
0.212
3.01,2
0.192
2.01
2.01
0.83
2.01
0.35
2.01,2
2.01,2
0.832
2.01,2
0.352
Grid mix Norway
n.a.
Imported grid mix
electricity from
Norway (high share
of hydro)
n.a.
Grid mix Poland
n.a.
Imported grid mix
electricity from
Poland (high share
of fossil fuels)
n.a.
Grid mix Spain
n.a.
Imported grid mix
electricity from
Spain (renewables
and fossil fuels)
n.a.
1.2
1.2
1.9
1.0
2.9
2.9
3.0
1.0
1.7
2.1
2.5
1.0
Nonrenewable
primary
energy
4b - Physical Energy
Content
Renew.
primary
energy
Nonrenewable
primary
energy
Entire supply chain
Primary energy factors for fuel suppy and infrastructure taken from the professional Life Cycle Assessment (LCA) database, developed
and annually updated by PE International (GaBi (2012)),
2 It is assumed for demonstration propose that the transmission losses of a grid mix are equal with transmission losses of an imported
grid mix
1
15
Renew.
primary
energy
6
Conclusions
The paper has summarised the existing definitions for primary energy, efficiency and primary energy factors, as well as the different options to account for primary energy in energy statistics,
environmental assessments or other applications. The usage of different types of primary energy— total primary energy, non-renewable (fossil) energy, or the division of non-renewable and
renewable primary energy— is important to understand because of the effect different options
and methods may have on statistics and policy targets. All commonly used accounting methods to
calculate primary energy equivalents or efficiencies have been discussed, including the impact of
different methods on the calculation of primary energy factors.
There are different ways to account for primary energy which makes it difficult to compare primary energy values or primary energy factors. Depending on the type of primary energy and the
method, which mostly depends on the type of application and the publishing institution, primary
energy factors can distinctly vary for the same renewable energy source. As shown in Moomaw
(2011), Machnick (2011) and Harmsen (2011), the primary energy consumption of a country or a
system is influenced by the accounting method. A distinction between renewable and nonrenewable primary energy, as normally used in life cycle assessments (LCA), could avoid misleading interpretations of energy consumption over time. This distinction has the advantage that finite
energy sources are not added with infinite energy resources. Life cycle assessment and the division of primary energy into renewable and non-renewable sources is therefore, a robust and suitable way to understand the energy consumption of a system or country.
Nonetheless, a distinction of primary energy does not necessarily reveal the energy efficiency of a
system or product. The electricity consumption of a system, supplied by a renewable source with
a high primary energy factor (e.g. solar photovoltaic), can be explicit lower although the overall
renewable primary energy consumption is higher than for an alternative system supplied by e.g.
hydro power.
The separation of primary energy into non-renewable and renewable components is therefore
especially useful when comparing primary energy factors for renewables with those for fossil
fuels.
The non-renewable primary energy necessary to generate electricity from renewable sources
gives a clear understanding of the energy intensity of the manufacturing, installation and operation of the infrastructure (hydro power station, wind turbine, photovoltaic cells etc.). Results can
be compared between electricity from different renewable energy sources but also with electricity generation from fossil fuels.
In the second part of the study “Primary Energy Demand of Renewable Energy Carriers – Part 2
Policy Implications” the use of primary energy factors in EU legislation is presented. The impact of
primary energy factor calculation on greenhouse gas mitigation targets and renewable energy
targets is discussed, and possible policy outcomes of using different primary energy factor calculation methods in three different policy areas - Energy Performance of Buildings Directive (EPBD),
Energy Efficiency Directive (EED) and Renewable Energy Directive (RED) - are provided.
16
7
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