Finnish method

The Finnish method (also referred to as the reference efficiency method , English alternative generation method ) is a method for calculating the savings in primary energy in the case of the joint electrical energy and heat obtained in combined heat and power generation (CHP) compared to the separate or uncoupled production of electrical energy and heat in one Reference system. It is used both when calculating energy balances for entire economies and for assessing individual CHP systems (e.g. thermal power stations ).

Description of the method

First, a thermal efficiency η _{th, CHP} and an electrical efficiency η _{el, CHP are} determined for the CHP systems via the annual thermal work W _{th, CHP} , the annual electrical work W _{el, CHP} and the total annual fuel consumption W _{Br, CHP} :

${\displaystyle \eta _{\mathrm {th,KWK} }={\frac {W_{\mathrm {th,KWK} }}{W_{\mathrm {Br,KWK} }}}}$

${\displaystyle \eta _{\mathrm {el,KWK} }={\frac {W_{\mathrm {el,KWK} }}{W_{\mathrm {Br,KWK} }}}}$

Together with the thermal and electrical efficiencies of the reference system η _{th, Ref} and η _{el, Ref} , the primary energy savings PEE compared to the reference system can then be determined:

${\displaystyle PEE=\left(1-{\frac {1}{{\frac {\eta _{\mathrm {th,KWK} }}{\eta _{\mathrm {th,Ref} }}}+{\frac {\eta _{\mathrm {el,KWK} }}{\eta _{\mathrm {el,Ref} }}}}}\right)\cdot 100\,\%}$

Note: Since 100% = 1, the formula can alternatively be shown without the term “ 100%”. ${\displaystyle \cdot }$

The entire fuel input W _{Br, CHP} can then be divided into a fuel input for heat generation W _{th, Br} and a fuel input for electricity generation W _{el, Br} via the primary energy savings and the degrees of efficiency :

${\displaystyle W_{\mathrm {th,Br} }=W_{\mathrm {Br,KWK} }\cdot (1-PEE)\cdot {\frac {\eta _{\mathrm {th,KWK} }}{\eta _{\mathrm {th,Ref} }}}}$

${\displaystyle W_{\mathrm {el,Br} }=W_{\mathrm {Br,KWK} }\cdot (1-PEE)\cdot {\frac {\eta _{\mathrm {el,KWK} }}{\eta _{\mathrm {el,Ref} }}}}$

The thermal and electrical annual work in relation to the respective fuel consumption results in the effective efficiency of the sub-process.

${\displaystyle \eta _{\mathrm {th,eff} }={\frac {W_{\mathrm {th} }}{W_{\mathrm {th,Br} }}}}$

${\displaystyle \eta _{\mathrm {el,eff} }={\frac {W_{\mathrm {el} }}{W_{\mathrm {el,Br} }}}}$

Derivation of the primary energy savings

The primary energy savings PEE compared to the reference system η _{th, Ref} and η _{el, Ref are} based on the following. Combined heat and power is used to generate electrical energy from a fuel unit η _{th, CHP} units heat and η _{el, CHP} units. If these useful energies had been generated uncoupled from the respective reference technologies, the following fuel consumption W _{Br, Ref} would have been necessary:

${\displaystyle W_{\mathrm {Br,Ref} }=\left({\frac {\eta _{\mathrm {th,KWK} }}{\eta _{\mathrm {th,Ref} }}}+{\frac {\eta _{\mathrm {el,KWK} }}{\eta _{\mathrm {el,Ref} }}}\right)\cdot W_{\mathrm {Br,KWK} }}$

The primary energy saving is the difference between the fuel requirement of the uncoupled reference system W _{Br, Ref} and the joint production W _Br , based on the reference system.

${\displaystyle PEE={\frac {W_{\mathrm {Br,Ref} }-W_{\mathrm {Br,KWK} }}{W_{\mathrm {Br,Ref} }}}=1-{\frac {W_{\mathrm {Br,KWK} }}{W_{\mathrm {Br,Ref} }}}=1-\left({\frac {\eta _{\mathrm {th,KWK} }}{\eta _{\mathrm {th,Ref} }}}+{\frac {\eta _{\mathrm {el,KWK} }}{\eta _{\mathrm {el,Ref} }}}\right)^{-1}}$

Note: The fuel allocation W _{Br, th} and W _{Br, el} distributes the primary energy savings equally to the electricity and heating side.

Applications and delimitation

The Finnish method is used in the preparation of energy balances , but competes with other methods. For example, the Finnish method is used in the energy balances drawn up by the Arbeitsgemeinschaft Energiebilanzen for Germany, with reference efficiencies of η _{th, Ref} = 80% and η _{el, Ref} = 40%. The energy balances of the German federal states are also determined using the Finnish method, but with reference efficiencies of η _{th, Ref} = 90% and η _{el, Ref} = 40%. In contrast, e.g. B. International Energy Agency (IEA), Organization for Economic Co-operation and Development (OECD) and Eurostat use a different method.

According to the European CHP Directive 2004/8 / EG, the use of the Finnish method for determining the primary energy savings of individual CHP systems was prescribed. This guideline was replaced by the Energy Efficiency Directive (EED) 2012/27 / EU, in which, in Appendix II, the primary energy savings (PEE) are to be calculated using the same formula.

In addition to the Finnish method, there are other methods for calculating primary energy savings and the allocation of fuel inputs (and thus also of CO ₂ emissions ) to electricity and heat.

Advantages and disadvantages

According to VDI guideline 4661, “there is no method that would have to be applied as a whole, ie according to thermodynamic, economic and ecological criteria”. It must be checked in each case whether the Finnish method or another method is "better or worse suited for the case under consideration and the resulting statements".

The advantages of the Finnish method are stated:

• The fuel savings are not overestimated.
• It is not only the CHP system under consideration that is assessed, but also its energy savings for uncoupled electricity and heat generation.

In addition, the following disadvantages are indicated:

• It is relatively complex.
• Assumptions have to be made regarding reference systems and thus reference efficiencies. The reference efficiencies can vary over a wide range and therefore have a strong influence on the result.

See also

• Carnot method
• Residual value method
• Equivalence digit method

Individual evidence

1. ↑ ^{a b} State Working Group on Energy Balances (Ed.): Glossary on the energy balances of the federal states . March 2014 ( lak-energiebilanzen.de [PDF; 252 kB ; accessed on January 18, 2015]). Online as PDF ( Memento of the original from March 4, 2016 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  
2. ↑ ^{a b c d} Arbeitsgemeinschaft Energiebilanzen e. V. (Ed.): Foreword to the energy balances for the Federal Republic of Germany . August 2010, 3 Allocation of fuel use to the products of electricity and heat according to the Finnish method , p. 10 ( ag-energiebilanzen.de [PDF; 161 kB ; accessed on January 18, 2015] Methodological description of the official energy balances in Germany).
3. ↑ ^{a b c d e f g} Wolfgang Mauch, Roger Corradini, Karin Wiesemeyer and Marco Schwentzek: Allocation methods for specific CO ₂ emissions from electricity and heat from CHP systems . In: Energy industry issues of the day . tape 55 , no. 9 , 2010, p. 12–14 ( ffe.de [PDF; 2.3 MB ; accessed on January 18, 2015]).
4. ↑ ^{a b c} DIRECTIVE 2004/8 / EC OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of February 11, 2004 on the promotion of a combined heat and power generation based on useful heat demand in the internal energy market and amending Directive 92/42 / EEC (PDF; 269 KiB ) , Annex III: Procedure for determining the efficiency of the cogeneration process . The German Combined Heat and Power Act referred to the appendix to this directive in Section 9a (2) No. 8.
   
5. ↑ International Energy Agency (IEA), Organization for Economic Co-operation and Development (OECD) and Eurostat (ed.): Energy Statistics Manual . 2005, p.  48 and 147 ( iea.org [PDF; 1.9 MB ; accessed on January 18, 2015] Methodical description of international energy balances).
6. ↑ DIRECTIVE 2012/27 / EU OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 25 October 2012 on energy efficiency, amending Directives 2009/125 / EC and 2010/30 / EU and repealing Directives 2004/8 / EC and 2006/32 / EG (PDF; 1.15 MB) , Annex II: Procedure for determining the efficiency of the CHP process . The German Combined Heat and Power Act refers in Section 31 (2) No. 13 to the appendix to this directive.
   
7. ^ Association of German Engineers (ed.): Guideline VDI 4661 Energy parameters: Definitions - terms - methodology . September 2003, p. 27 .
8. ↑ ^{a b} Gerald Kalt: Primary energy factors of fossil and renewable energy sources, electricity and district heating in the period 2000 to 2011 . Partial report of the project "Extension of the monitoring methods within the meaning of RL 2006/32 / EG by primary energy savings as well as calculation of the primary energy effects of the goals of the Energy Strategy Austria with regard to the draft of the Energy Efficiency Directive of the European Commission COM (2011) 370 final". Ed .: Austrian Energy Agency. Vienna June 2013, p. 7th f . ( bmwfw.gv.at [PDF; 965 kB ; accessed on February 23, 2015]). Online as PDF ( Memento of the original from July 4, 2014 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.