UDK 62(05):86210:30 CODEN STJSAO rssN 0s62-t887 · 2019. 1. 30. · UDK 62(05):86210:30 CODEN STJSAO rssN 0s62-t887 Casopis za teoriju i praksu u strojarstvu : Journal for Theory

UDK 62(05):86210:30 CODEN STJSAO rssN 0s62-t887

Casopis za teori ju i praksu u strojarstvu : Journal for Theory and Appli-cetion in Mechanical Engineering = Xypna.n Anfl Mrruf,f ,ocrponre.lrnoiTeopf,f , r trprrcrf,rcf, = Zeitschri f t zur Theorie und Praxis des Maschinenwesens

Godi5te (Volume) 49

zx47an320-1326Zagreb, studeni-prosinac (November-December) 2007.

Broj (Number)

Stranica (Page) 405492

SadrZaj

Dana5nja i bududa uloga plina u energeticiRePublike llrvatske

M. sunii

Odabir optimalnog pristupa odredivanjumetodologije Tarifoog sustava za toplinarskedjelafirosti (1320)

E. Banovac, Z. Bogdan i I. Kuzle

Metodologij a utwdivanj a naknade prikljudenja natoplinsku mreZu (132L)

M. Klepo, M. Kostelac iA. Curkovii

Model za odredivanj e pokaz atelja pouzdanostidistribucij ske mreZe za razliEite scenarij etoancij skih ulaganja (1322)

V Komen

Parametri Ena analiza ko- generacij sko g sustava s astirlingovim motorom ( I 323)

U. Stritih, G. Zupan i V Butala

Poveianj e energetske efkasnosti ugradnj om novihplinskih uredaja (1324)

M. Sunit i N. Kutatlj

Aktualno stanje ADRIA LNG projekta (1325)S. Kojundiit iAndreja Ana Lopac

Stanj e i rcnr oj pravno-institucij sko g ofu ta zapoticanje obnovljivih izvora energije (OIE) ikogeneracije u Republici Hrvatskoj (1326)

I. Raguzin 469

rN MEMORTAM 477; OSVRTT r MTSLJENJA 479;ZBIRNI SADRZAJ 480

431

409

421

44r

461

Contents

PresentAnd Future Role of Gas in EnergyIndustry of the Republic of Croatia

M. Sunic

Choosing the OptimalApproach to Defoe theMethodology of a TariffSystem for ThermalEnergy Activities ( 1 320)

E. Banovac, Z. Bogdan and I. KuzleMethodology of Charges for Connection to ThermalNetworks (1321)

M. Klepo, M. Kostelac andA. Curkovic

A Model for Determination of DistributionNetwork Reliability Indices for DifferentFinancial Investment Scenarios (1322)

V Komen

Parametrical Analysis of Cogeneration SystemWith Stirling Engine (1323)

U. Stritih, G. Zupan and V Butala

Energy Effciency Increase by Using New Gas-Fired Equipment (1324)

M. Suni6 andN. Kulqrlj

ADRTA LNG - Current Situation (1325)S. KojundZit and Andreja Ana Lopac

State and Development of Legaland InstitutionalFramework for Promotion of Renewable EnergySources and Cogeneration in the Republic ofCroatia (1326)

I. Raguzin 469

N \fE\IORL{\{ 477; VIEWS ANDRETROSPECTIO\S 479: CUMULATIVE SUMMARY 480

42r

431

441

46t

Igor KuzleHighlight

CODEN STJSAO ISSN 0562-1887

Casopis za teoriju i praksu u strojarstvu in Mechanical Engineering )KypHaJ1 npaKTHKII ~ Zeitschrift zur Theorie

- --.----------"-,---"- .. -----,

~ Journal for Theory and Application )l.J1l1 und

M3111UHOCTpOlfTeJlHOH Teopnn n

Praxis des Maschinen wesens

GodiSte (Volume) 49

ZX47011320-1326 Zagreb, studeni-prosinac (November-December) 2007_

Broj (Number) 6

Stranica (Page) 405-482

UrcdniStvo i uprava (Head and Editorial Office): Bcrislaviccva 611,10000 Zagreb, Republic of Croatia; Tclcfon/tc1cfaks +385 (0)1 4872497, www.hsbis.hr;E-posla:[email protected]

Osnivac i izdavac (Founder and Publisher): Hrvatski slrojarski i brodogradcvni inzcnjcrski savcz (Croatian Union of Mechanical Engineers and Naval Architects)

Glavni urcdnik (Editor-in-Chiel): Bernard FRANKO VIC Urcdnistvo casopisa Strojarstvo, Bcrislaviccva 6, HR-10000 Zagreb, tclcfon/lclcfaks +385 (0) 1 4872497 E-po.sla: [email protected]

lIrednici rubrika (Contributing Editors): Ivo ALF/REV/C, Zvonko BENC/C, Zarko BUR/C', Bemard FRANKO-VIC, Aleh~mdar GREGUR/C, /vica LIBR/C', Zelimir ORSAN/C, /:..:,~r SUTLOV/C i/and Srei·ko TUR/NA

Urednicki odbor (Editorial Board): /1'0 ALFIREV/C' (Zagreb), Mirko BUTKOV/C (KarlovaL), Vladimir JARIC (Zagreb), Branimir 1"1ILCIC (Zagreb) iland Andrija MULe (Za-greb)

Mcdunurodno urednicko vijece (International Editorial Board): Vafros/av GRUBfSIC (Fraunhoficr Institllt - Danwitadt, NjefTl~cb), L)'gmunt HADUCH SUSKl (1..}niversidad de Monterrey - Monterrey, Meksiko), Branko KATALlN/C (Tehnisehe Universitiit - Wien, Austri-ja), Elso KULJANlC (University of Udine - Udine, ltalija, & Tchnicki fakultct - Rijcka, Hrvatska), Adolf SOSTAR (Tehniska fakulteta - Ma-ribor, Slovenija) i/and Ruman WlELGOSZ (Po!iteehnika Krakowska -Krakow, Poljska)

Savjet casopisa (Journal Council): Fakultet elektrotehnikc, strojarstva i brodogradnjc SveuCilista u Splitll

Split (Dinko BEGUS/C, Ljiljana PfUC-RABADAN); Fakultet stro-jars,tva i brodogradnjc SvcuCilista u Zasr

Strojarstvo 49 (6) 409-420 (2007) Eraldo BANOVAC et. ai., Choosing the Optimal Approach .. 409

CODEN STJSAO ZX4701I320

ISSN 0562-1887 UDK 621.311:620.9:657.474

Choosing the Optimal Approach to Define the Methodology of a Tariff System for Thermal Energy Activities

EraMo BANOVAC I), ieljko BOGDAN '>' Igor KUZLE J)

1) Hrvatska energetska rcgulatorna agencija (Croatian Energy Regulatory Agency), Koturaska 51 HR-I 0000 Zagreb, Republic of Croatia

2) Fakultct strojarstva i brodogradnje Sveuciliste u Zagrebu, (Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb), Ivana Luciea 5 HR-IOOOO Zagreb, Republic of Croatia

3) Fakultct clcktrotehnike i racunarstva Svcucilistc 11 Zagrebu (Faculty ofEJectricai Engineering and Computing, University of Zagreb) Unska 3, HR-I 0000 Zagreb, Republic of Croatia

[email protected]

Keywords Methodology [{uHf elements TarffJ·\}"stem Thermal energy Usability degree

Klj ucne rijeci wfetodologija Swpanj iskorisfivosli Tarifnf elementi Tarifnf su.slav Toplinska energija

Primljeno (Received): 2006-05-12 Prihvaceno (Accepted): 2007-02-5

1 Introduction

Original scientific paper

Research of elements important for defining the methodology of a Tariff system for thennal energy activities is outlined in this paper. The transparent matrix of tariff models is defined. Original equations for regulating the annual revenue and calculating the monthly account for delivered heat by using tariff elements such as provided power, delivered heat energy and monthly fee, are shown in the paper. Special attention is paid to the choice ofrnethods for approving consumption of fuels that are used in heat generation and the criterion for technical losses, i.e. for referential degrees in heat distribution and heat generation where technical losses depend on used fuel type.

Odabir optimalnog pristupa odrcdivanju metodol(!gijc Tarifnog sustava za toplinarske djelatnosti

Izvomoznanstvcni clanak

U radu je istrazen znacaj odredivanja metodologijc Tarifnog sustava za top!inarske djelatnosti. Odredena je razvidna matrica tarifnih modela. Izvcdenc su izYome fonnule za regulaciju maksimalno dozvoljenog prihoda i izracun mjesecnog racuna preko tarifnih elemenata za ispomcenu energiju, snagu i mjesecnu naknadu. Poseban osvrt danje na izbor metode za priznavanje utrosenog energetskog goriva i postavljanje kriterija za tchnicke gubitke, tj. za referentne stupnjcve iskoristenosti kod distribucijske mreze i proizvodnje toplinske energijc gdjc tehnicki gubici ovisc 0 vrsti energctskog goriva.

Croatian energy legislature [1-3] defines the rules for devising the methodology of a Tariff system for thern1al

energy activities. The Croatian Energy Regulatory Agency (in further text: the Regulator) passes the methodology,

or tariff system without the amounts of tariff elements, after it receives a prior opinion from energy undertakings that periorm energy activities for which a tariff system

applies and from the Ministry of Economy. In fact, a tariff system consists of a prescribed methodology for defining tariff elements and their amounts. The Government of the

Republic of Croatia defines the amount of individual tariff clements in the tariff systems, upon the proposal of the

Ministry of the Economy (further in text: the Ministry).

An energy undertaking that performs the activities to

which a tariff system applies shall submit a proposal to

the Ministry, which shall then obtain the opinion of the

Regulator.

Choosing the right approach to determine the

methodology is an important problem, because the consequences of a wrong concept could be serious.

Use of tariff system will determine the business of the thennal energy sector in Croatia in the following years essentially and enable its imperative development. The thennal energy sector is very important for the functioning of society, because thermal energy is lIsed

for heating, sanitary water heating, or for technological

usage in production. The usage level of thermal energy

410 Eraldo BANOVAC et. aI., Choosing the Optimal Approach ...

Symbols/Oznake

c,

CGA ,

CPI,

!1ClIslOlners

F

G

G,

II .1.1

- monthly bill submitted to each customer, HRK

- mjesecni racun koji dobijc potrosae

- real energetic fuel price, HRKlkg, HRKlmJ

- stvarna cijcna energetskog goriva

- amount for covering fixed costs in year I-I, HRK

- iznos za pokrivanje fiksnih troskova u godini I-I

- amount for covering costs of spent energetic fuels in year I, HRK

- troskovi potrosenog cncrgetskog go-riva u promatranoj reguJacijskoj godini t

- unit price of concrete fuel from this purchase i, HRKlt, HRKlkg, HRKlmJ

- jcdinicna cijena pojcdinog goriva za odrcdcl1u nabavu i

- amount for covering variable costs in year I, HRK

- iznos za pokrivanje varijabilnih troskova u godini t

- adjusting factor due to increased number of customers, HRKJcustomer

- poddavajuci faktor uslijcd porasta broja kupaca

- index of customer prices in ycar t - indcks potrosackih eijena u godini t

- sales price in year t, HRK - prodajna cijcna u godini t

- difference in number of customers - godisnja razlika broja kupaca

- fees amount for stimulating renewable sources and cogeneration usage, regulatory activities and stranded costs, HRK

- iZllos naknada za poticanje obnovJjivih izvora cncrgije i kogeneracije, obavljanje poslova regulacije energetskih djclatnosti i naslijedene troskove

- consumption, t, mJ

- potrosnja

- unit quantity of each fuel at onc purchase i, t, kg, m3

- jcdinicna koliCina pojedinog goriva po jednoj nabavi i

- lower calorific value of fucl,kJ/kg,kJ/mJ - donja ogrjcvna vrij:::dnost goriva

- lower calorific value of each fuel i, MWh/kg, MWh/m J

- donja ogrjcvna vrijednost goriva i

I

I

I,

KC,

N

P

P,

fl.P)

R

RF,

Strojarstvo 49 (6) 409-420 (2007)

- index which marks hour in calculated period

~ indeks koji oznacava sat u obracunskom razdoblju

- inflation index - indeks inflacije

- index of customer prices - indeks potrosackih cijena

- factor of price correction in year t, HRK - faktor korckcije cijene u godini t

- index which marks total hours number of heating in calculated period

- indeks koji oznacava ukupan broj sati grijanja U obracunskom razdobljll

- price, HRKlt, HRKlmJ

- cijena

- price in year t, HRK - cijena u godini t

- Price-cap component, HRK - Price-cap komponcnta

- total thermal energy at disposal for consumption in observed year t, MWh

- ukupna toplinska encrgija raspo101:iva za potrosnju u godini t

- delivered heat in year t, MWh - godisnja predana toplina

- monthly delivered heat, MWh - mjesecna predana toplina

- total technical losses in boiler, MWh - ukupni tehnicki gllbitci II generatom

pare

- total technical losses of hcat in distribution network, MWh

- ukupni tehnicki gubitci toplinske energije u distribucijskoj mrcii

- total sum of generated and purchased quantities of heat, MWh

- sumanla ukupna kolicina proizvedcne i kupljene toplinskc energije

- rcvenue in year t, HRK - prihod u godini t

- contribution of regulated funds in year I,HRK

- prinos od reguliranih sredstava u godini t

- monthly revenue of a regulated company, HRK

- mjesecni prihod reguliranc tvrtke

- maximal annual revenue in year t, HRK

- rcgulirani maksimalni prihod 1.1 godini t

Strojarstvo 49 (6) 409-420 (2007) Eraldo BANOVAC et. aI., Choosing the Optimal Approach ... 411

R, - authorized revenue amount of regulated company in year t, HRK

- autorizirani iznos prihoda regulirane tvrtkc u godini t

R,IS, - revenue per customer in year t, HRK - prihod po kupcu u godini t

Sshc - standard specific heat consumption, kJIMWh

- standardni specificni utrosak topline po jcdinici proizvcdcne toplinske energijc

SSC""",.(ud - standard specific cost of energetic fuel for a certain plant i, HRKlMWh

- standardni specificni trosak energetskog goriva za neko postrojenjc i

- observed (current) year - promatrana (tekuta) godina

t /lil/h,,.,,,.; - temperature of environment according to informations of Hydrorneteorologic institute for each hour in month, °C

- temperatura okoline prema podacima Hidrometeoroloskog zavoda za svaki sat u mjesccu

t a",/,,,'n'.I"jer{

412 Eraldo BANOVAC et. aJ., Choosing the Optimal Approach ... Strojarstvo 49 (6) 409-420 (2007)

and technologically, as well as cconomically, especially concerning existing limitations which are the results of an old distribution network and oflong existing treatment of heating price as a social category. Using the methodology of a Tariff system for thermal energy activities has to initiate development and facilitate modernization of the existing energy infrastructure of a thermal energy sector and this will have an influence on increasing energy efficiency and decreasing specific business costs.

2 Determination of possibility for initiative regulatory acting

Rate-of-return (ROR) and Price-caps regulation (RP-X) are two basic forms of economic regulation nowadays. Both forms are oriented (considering theoretically) to achieving the same aims, but in different ways. The aims presume efforts of a regulatory body to limit the strength of natural monopolies, impede realization of extra-profits by regulated power companies, and prevent unjustified increase of energy prices as well as prices of related services. Rate-of-return regulation is an older form of economic regulation, very often llsed for regulation of public services, primarily in the USA. It is also called Cost-of-service regulation, because the regulatory body recognizes only costs that are necessary to offer customers good quality service. The principle of this regulation is simple, because costs recognized by a regulatory body are added to the energy basic price. When a certain capital investment level is achieved, a regulatory body determines an acceptable return rate of invested capital on the basis of which a regulated power company realizes adequate profit. Regulated companies are allowed to realize profit to cover business expenses increasing with fixed profit rate on invested funds - which corresponds to capital expense. Consequently, covering business costs increased by a reasonable profit rate determined by a regulatory body should be accepted. It is clear from the preceding explanation why this fom1 of regulation is also called "regulation by return rate". The main objection to regulation by return rate is that it does not give enough initiative for regulated companies to decrease their costs more significantly. Furthermore, another objection is the lack of initiative to improve business efficiency. It is overcome successfully by using the so-called PBR regulation (Performance Based Regulation), which means using difTerent Price-caps/Revenue-caps equations and represents a successful newer fonn of regulation used by the majority of regulatory authorities worldwide. A lot of papers lrom this field have been published'. The roots of this form of regulation date lrom the eighties of the twentieth century, when the British Government realized

I Valuable titles to access the field of PBR are [4-(lJ.

efficient privatization of companies which carried out the most important public services'- Soon after establishing Price-caps/Revenue-caps regulation it was detennined that regulated power companies accept the advantages of a regulatory realized benchmark which had been used during specific regulatory period over years. It manifested itself in such a way that this approach resulted in decreasing business costs, particularly operational costs. Power companies decreased costs essentially and realized financial savings. That regulation was used mostly by the regulator for regulating the energy activities which were considered as natural monopolies, or which were carned out as public services in Great Britain, the innovator of the previously-mentioned regulation. It related to regulated companies which had been the owners of transmission or distribution networks in electricity power sector as well as electricity supply for tariff customers. A typical Price-cap equation directed at price maximization has the following form:

maxC, = (I + CPI, -X,)-maxC,_, - KC, (I)

In (I) t is observed (current) year, and t - I is the previous year, in a regulatory period which usually covers a period of three, four or five years. Further, max C

t is

sales price in year t, max Ct

_1 is sales price in previous

year t - 1, CPlt is index of customer prices in year t, X, is

efficiency coefficient in year t, and KC, is factor of price corrcction in year t which is added because of calculation of those costs on which regulated power company can not influence.

Revenue-cap equation, with which observed year level is determined R - authorized revenue amount , of regulated company, starts from realized revenue In previous year R

t_

1 and has a general form as follows:

R, = {[ R,_, + (CGA,' LlCustomers )J(I + I - X)} ± Z (2)

where t is observed (current) year, and /- I is previous year, in a certain regulatory period. CGA

I is the adjusting

factor due to increased number of customers (HRKI customer), f:..CustomersJ is difference in number of

cllstomers, 1 is inflation index, Xis efficiency coefficient determined by the regulatory body, and Z is correction for non-planned events·!.

1 Those companies arc: British Telecom (1984) in the field of te-lecommunications; British Gas (1988) in the field of natural gas; National Grid, Regional Electric Companies and Scottish Po\ver & Hydro (1990) in the field ofdectricity power.

J Definition !1Cuslomers according source 171. ~ That could be tax increase, rcstmcturing costs arising from re-alization of law duties, duties arising fr0711 change of legislature conccming environment protection, etc.

Strojarstvo 49 (6) 409-420 (2007) Eraldo BANOVAC c1. ai., Choosing the Optimal Approach ... 413

It is possible to change Price-cap equation into Revenue-cap equation. The general fonn of hybrid C combined) Revenue-Price cap equation is as follows:

P"., =(w)f(p)+(1-w) ;' , (3)

where PI + 1 is price in year t + 1, P, is price in year t, fCP,) is Price-cap component, w is relative ponder to

component Price-cap and Revenue-cap, and l\1 is revenuc per customer. 5,

There are mathematical possibilities to create combined Revenue-Price cap equations. Such equations are as follow:

I) For prices, Price-cap equation in fonn P = f(P,_,) and . . R . .

Revenue-cap equatIOn In fonn P = - gIve the folloWIng S

combined Revenue-Price cap equation;

(4)

2) For revenue, Price-cap equation in fonn R = p. S

and Revenue-cap equation in form R = f( R1_1) gIve combined Revenue-Priee.cap equation;

Table 1 Matrix of tariff models

Tablica 1. Matrica tarifnih rnodela

R = (I - w)· p. S +( w)· f(R,_,) (5) In (4) and (5) P is price in year t,p,.] is price in previous

year 1-1, R is revenue in year I, Rr_] is revenue in previous year t-1, S is sale in year t, and w is relative ponder to component Price-cap and Revenue-cap. Regulatory authorities detennine the values of relative ponder w and its amounts [0,1]. w= 0 in case when considered mathematical forms tum into Price-cap equation, or w= 1 when they tum into Revenue-cap equation.

By means of different Revenue-cap equations the regulatory authorities can detennine maximal allowed revenue of regulated companies in the energy sector. This method regulates maximal revenue which could be realized by a regulated company in certain year of regulatory period. It should be pointed out that Revenue-cap is simpler to detenninate and control than Price-cap fonn. Revenue-cap is compatible with accounting standards which are usually used and follows demands of regulatory authorities well. Therefore, it would be efficient for considered methodology to use the method of maximal allowed revenue of thermal power company. This method detennines suitably the revenue amount in observed year t for which regulatory authorities allow according to realization of each thennal energy activity. Respecting justified business costs, each company is

~----.-- ... _--- -- -'."--'-- -----

ups Tariff gro (eonS\lm,~lion KategorlJa po

category) trosnjc T"

-----------"

try and T -Indus bi;~iness ell lndustrija i p

stomers oslovni

potros: lei

_.

eholds T - rlous at'--------~- --_.- -----~ --~~------- --- --- - -------~. .. .. \

T T T ! ," .72 .7:; I HRK/kWh HRK/kW HRK ,

I ,

T T.~2 T i ,"

414 Eraldo BANOVAC et. aI., Choosing the Optimal Approach ... Strojarstvo 49 (6) 409-420 (2007)

allowed reasonable and socially acceptable funds return invested in business.

3 Matrix of tariff models

Elaboration of methodology for generation, distribution and supply of heat should be started with creating a matrix of tariff models (further in text: matrix). One of the matrices appropriate for use in the Croatian thermal energy sector is presented in table L Tariff elements in this matrix are financial amounts given in HRK for energy, power unit and fixed monthly fee, and are determined according to the categories of consumption. The categories of consumption are the following tariff groups: T" for industry and business customers, T

g, for households at centralized heat system

and TgJ

for households at decentralized boiler houses. Tariffelements in the matrix are: 7'" for energy (delivered heat), 'Z, for abounded power according to the pennission for thermal energy production and 7',3 for fixed monthly fee5 • In fact, tariff elements in the matrix are financial amounts given in HRK for delivered energy, power and fixed monthly fee, which along with the methodology form a Tariff' system for thermal energy activities.

By using the tariff elements given in the matrix, it is possible to make the following equation:

(6)

where B""""" is monthly bill submitted to each customer, Q"c"""""';m"lIfllh is monthly delivered heat, »:,bmmd,'" is abounded po\vcr according to the permission for thermal energy production, and ~'i are tariff elements. Furthermore, it is possible to express monthly revenue R"'''''I'' of a regulated company as the sum of amounts of all the bills issued in one month:

k

RIII'I/I'" = I 8/1/(111111(/) i=1

where k is number of customers.

(7)

Finally, equation for R - annual revenue (concerning each year of regulatory period) has form as follows:

I.' II 12 IJ

11= " "0 . Tdl"'l+ " "lV""""",{,.,,' .L..- L _dcl""'rcd,""/llh(fIIl) L L ",=-1 [=1 mool,,,,,1

" . 7:'2(111) + I k", I .. 3(",) (8)

",=1

There is a mle that the Regulator has to determine R - maximal annual revenue of company which

",,,,If)

'< Fixed momhly fce refers to capability of heat generation system, maintenance nnd inmeasuring of heat meters in heat distribution and costs of calculating service in heat supply.

carries out generation, distribution or supply of heat for tariff customers. Hence, the condition R -S Rm,ur'i has to be fulfilled.

4 Possibilities for calculating cost of fuel

Cost offuel is absolutely dominant in the category of business costs of thermal power companies. It amounts to about SO % of b'usiness costs in the developed countries in Europe. It reaches 60-70 % in Croatia because of price increase of fuels over the last two years and prices of delivered heat have not changed during this time. Therefore, an equation for regulating maximal allowed revenue should comprise this cost as a separate factor. COst of fuel is a function of generated heat, used fuel types and technical as well as technological characteristics of plants. SSCener.fuel is standard specific cost of fuel for a certain plant i, given in HRKlMWh. It is calculated as:

sse e ( S"" ) f'l!er.r"c/ =

Strojarstvo 49 (6) 409-420 (2007) Eraldo BANOVAC et. aI., Choosing the Optimal Approach ... 415

The second onc is technically orientated and stimulates introduction of criterion of efficiency for thcse costs.

4.1 Cost approach towards covering costs of spent fuels

When C~":I (I) i.e. amount for covering costs of spent fuels in year t is calculated, it is necessary to take into consideration as follows:

I. Total installed power; it means power registered and being in evidence, from contracts concluded between suppliers and customers.

2. Fuel quality, certified by attests for lower calorific value Hd and quality of chemical composition of fuel.

3. Outer project temperature for certain locality.

4. Technical losses in heat generation and heat distribution (distribution network), defined by regulatory authorities.

Costs of fuel purchase are defined on the basis of: a) fuel quantity spent for generation of heat, measured

and given to heat meter of distribution network, taking ::.t:::: considaration lower calorific value for used fuel as well as for approved technical losses in generation, depending on type of used fuel according to following criteria: up to 150/0 for natural gas, up to 20% for masut, up to 20% for coal, up to 35% for biomass, biofuel, biogas or waste,

b) enclosured documentation of realized fuel purchases (sales contracts, invoices, warehouse receipts, quality attests with defined lower calorific value).

In case that regulatory body chooses the described method of approving costs of fuel, higher purchase price of fuel than that which was valid on the market during the observed period should not be approved. It means that regulatory authorities have to monitor all business activities ofthennal power companies and state in market of oil and oil derivatives too, according to regulatory monitOl ;Jlg rules described in [8]. (;''''1(1'- amount of costs for total purchased quantity of different fuels in year t is calculated as the sum of amounts of purchases of each fuel type (suIr, uf individual purchases, or product of quantities and unit prices for each fuel type) following the equatIOn:

n "

Crlle/(l) = I,C'(iiW) ' c,(g,,'1 + I Gt!U1!) 'Cd",1) + '00) ,0,) ,

Il "

+'G ·c ,+'G ·cr

· L ,(co,,!) ,(",,,I) L 1(1,,,,) ,b'",1 (l I) ,=) ,=)

where Gi

is unit quantity of each fuel at one purchase (t, kg or 111 3), and c, is unit price of concrete fuel from this purchase (I'IRK/t, HRK/kg or HRK/m').

In the event that one part of fuel quantity was purchased at foreign currency clause, foreign currency should be converted into HRK according to the exchange rate which was valid when relevant fuel quantity was paid.

4.2 Technical approach towards covering costs of spent fuels

Fuel costs Cpwl(

416 Eraldo BANOVAC et. aI., Choosing the Optimal Approach ... Strojarstvo 49 (6) 409-420 (2007)

where Gi is the quantity of each fuel spent during year (t, kg or m').

For geothermal and solar energy as well as for purchased energy

if> = Q, (16) I Qddi"

Strojarstvo 49 (6) 409-420 (2007) Eraldo BANOVAC et. aI., Choosing the Optimal Approach ... 417

Table 3 Technical approach to fucl expenses valuation

Tablica 3. Tehnicki pristup pokrivanju troskova za gorivo

Consumption Price Fuel

Gorivo Potrosnja Cijena

G p

Heating oil 20,500 t 1200 HRKlt

Loi ulje

Gas 92,117 103 m 3 0,80 HRKlmJ

Plin

Total Ukupno

'7

0.8

0.85

In order to evaluate error influence in this evaluation on revenue, realized by producera, sensitivity analysis has been done which is shown in Figure 1. From Figure 1 it could be calculated that an error in evaluation of heating oil part in fuel mix of 1 % influences revenue in amount of 0.315 %, which can be acceptable.

--~--.~---

Gro ..... th 30%),----.------------,

of

;lpprovcd

fuel

costs I

I'rirast

pri1.natih

troskova

goriva

L.... ___ _

• 25%+-------------~.~----

2~"D1----- • •

15%-------- ---.-------\ • 10%t--- •

5% -.---~--.-------~---------

-5%-

• 0.2 . .::O~.4'___...::.O"'.6 _ __"OJl ___ ... ~ _ __"

Approved part of heating oil in fuel mix I

Priznali udio loz-ulja II miksu goriva ~~~-

Figure 1 Approved fuel cost increase as a function of approved heavy oil share in fuel mix

Stika I. Prirast priznatih troskova za gorivo u zavisnosti od priznatog udjcla loz ulja u miksu goriva

5 Losses in heat generation and heat distribution

For defining criteria of losses in systems for heat generation and heat distribution (which is needed to be defined by the methodology) it should start with data presented in table 4. From the table, it is obviolls that these losses9 are several times bigger in transient

418 Eraldo BANOVAC et. aI., Choosing the Optimal Approach .. Strojarstvo 49 (6) 409-420 (2007)

Table 4 Losses in heat generation and heat distribution

Tablica 4. Gubici u proizvodnji i Jistribuciji toplinskc cncrgije

CHARACTERISTICS: Unit consumption of heat and

typs oflosscs Unit

ZNACAJKE: lcdinica

Jedinicna potrosnja top line i (I)

vrste gllbitka . -_ .. _ .. _ .. _._--_.-

Heat consumption (annual energy consumption!

heated space) kWh/m J

Potrosnja topline (godisnja potrosnja encrgijcl

grijani prostor)

% of delivered Distribution losses heat Gubici distribucije % ispomcenc

topline

Number of water rcfillings (annual number of water ref!llings/watcr volume in

Fillings in year network)

Pllnjcnja godisnje Broj izmjena vode

(godisnji volumcn nadopllnal volumen vode u mrczi)

Generation losses % () f fuel energy Gubici proizvocinje % encrgijc goriva

Table 5 Referential usability degrees for separated heat generation

Tablica 5. Refcrentni stupnjcvi iskoristivosti odvojenc proizvodnje toplinske energije

Middle and East Europe and ex

USSR West Europe Proportion Srednja i Istocna Zapadna Europa Omjer Europa te bivsi (3) (2/3)* 100

SSSR (2) .. _--_ .. _--_.

---~--

70- 90 45·- SO 168%

x~ 80 x~7,5

IS - 25 5 - 10 267 % -

x~ 7,5 x ~ 20

10-30 I ~ 5 -

x~3 667 %

x ~20

IS - 40 5 - IS 275 %

x ~ 27,S x ~ 10

Industrial Regional

stearn healing Separate heating

In an analysis made with the purpose of an defining acceptable level for approved losses (which should

be regulated by the methodology) infonnation about referential usability degrees of separate heat generation in European couiltries are used. It is foreseen that referential values will be stipulated a.s an addition to Directive 2004/8/EC [9] on the promotion of cogeneration. Actual ~uggestion of working group is shown in table 5.

Fuel plants

Encrgctsko gorivo Indus!rijska Podrucno

Posebne top lane par::! grijanJc

'% %, % ........

Pit-coal

Kameni ugljen 88 83' 86 '4

Natural gas 91 85' 'If) 88

Prirodni plin

Lignite 88 83' 86 ~4

Lignit

Healing 011 09

Loz ulje ):I..)' 88 86

Bi()JIlas~

Blomasa " 80 79 Industrial g;ls (refineries,!

coke pl;lrl!~) 88 S:t " 85 Industrijski rim I

(r;!llilerije. koksare) I ,. Thl,; rcfercmiOlI \Isability dcgrces of i ndu~lry stearn general ion afC shown according 10 sugg~'slion of eEFle mlcres! gwup'lliotl.

... geferentl1l 51upnjevi iskoristivosti proi;;vodnjc industrijske pare prema prijedlogu CEFle illtereSIlC grupaciJe.

As oppos~d to plants for separate generation of electricity power, the age of plants for separate generation of heat, was not consideretl lillhe suggestion of referential values because technical development in this field was not significant ov('[ the last decade. Referential values suggested for generation of industrial steam are rated as too high in the report [10] of groups CEFIC and IFIEC". and reduction of values was suggested, as shown in table 5. Suggested smaller value ofinclustrial steam generation of 85 'io, in boilers heated by natural gas, is based on statistic data from the Netherlands. usability of 82')(, for

12 CEFIC and IFlEe arc important interest grouratioll because they represent companies in which over 60 % of Eurorean industl)1 co-g.cneration capacities are installed.

Strojarstvo 49 (6) 409-420 (2007) Eraldo BANOVAC et. ai., Choosing the Optimal Approach .. 419

boilers which use fuels produced in industry processlJ is explained with in appropriate composition of "waste fuels". Suggested referential values of usability degrees for boilers heated by coal and heating oil are based on the fact that combustion of hard and fluid fuels is less efficient than combustion of natural gas.

In practice, real usability degrees can vary from values declared by equipment producers significantly, which depends mostly upon number of operation hours, management of operational plant, starting and return temperatures, quantity of return condensated substance, frequency of loading changes, as well as upon length of operation lasting at loadings which are lower than nominal. Lower values than those declared by equipment producers are used for definihg savings index for primary energy in analysis of Austrian cogeneration potentionals too, which is presented in table 6. Different categories of plants for separate heat generation are shown in the table. Values in table 6 indicate that production of dry-saturated steam is less efficient than production of heating water. Efficiency of small heating systems is lower as well as plants heated by biomass or waste.

Table 6 Referential efficiency for separated heat generation (Austria)

Tablica 6. Referentnc cfikasnosti odvojene proizvodnjc topline (Austrija)

I Referential SEPERATED HEAT GENERATIONS degrees ODVOJENE PROIZVODNJE TOPLINE Rcfcrcntni

-- __ ~pnjcvi Hard fuci, high temperature boilers> 1 MW

0.85 Kmta goriva, visoko tcmpcratumi kotlovi > I MW

Fluid fuels, high temperature boilers> 1 MW 0.90

TckuCa goriva, visoko tcmpcratumi kotlovi > I M W

(ias fuels, high temperature boilers> 1 MW 0.90

Plinska goriva, visoko tcmpcratumi kotlovi > I MW

Boilers for generation of dry saturated steam (all fuels) 0.80

Kotlovi za proizvodnju suhozasiccne pare (sva goriva)

Small heating systems 0.75

Mali sustavi grijanja

Industrial gases 080

lndustrijski pJinovi

Biomass and waste 0.75

Biomasa i olpad

I.l Those boilers use refinery gases, cracking gases.

In connection with "approved technical losses" which should be defined by the methodology, for referential usability degree of distribution network IJd" ~85 % can be used. That means that the Regulator should approve technical losses in a distribution network up to IS % of total thermal energy measured on entrance of the network. These losses would be smaller gradually, so values of approved losses will be adjusted to actual EU values after 2010. Technical losses in heat generation depends on type of used fuel and could be approved up to 15 % for natural gas, up to 20 % for masut, up to 20 % for coal and up to 35 % for biomass, biofuel, biogas or waste.

6 Conclusion

Methodology of a Tariff system for thermal energy activities is necessary after analysis of conditiona in the Croatian thermal energy sector has been made by the Regulator. This paper has shown the way how to connect a matrix of tariff models consequently with maximal approved revenue in observed year I of regulatory period placed in relation to the total revenue calculated by using tariff elements from the matrix. Two possible approaches for approving the costs of uscd fuel are elaborated for heat generation as the most cost-intensive thermal energy activity, i,e. costs approach and technical approach. As shown, it would be optimal to choose a technical approach, because it stimulates energy efficiency, taking into consideration usability degree for combustion of each fuel type.

Based on the analysis that is macIe in the paper, and starting from actual condition in the Croatian thermal energy sector, it follows that it is necessary to define an adequate transitional period, during which higher "approved losses"l4 of heat generation and heat distribution will adjust by time 10 the EU referential values. Thus, the energy undertakings that carry out thermal energy activities should have explicit obligation to invest in system modemization over the next years,

I~ The level of losses is defined in the paper.

420 Eraldo BANOVAC c1. aI., Choosing thc Optimal Approach ... Strojarstvo 49 (6) 409·420 (2007)

References

[1] Law on Energy, Official Gazette of the Republic of Croatia, Nos. 68/01 and 177/04, Zagreb 2001 and 2004.

[2] Law on production, distribution ond supply of thermal energy, Official Gazette of the Republic of Croatia, No. 42/05, Zagreb 2005.

[3] Law on regulation of energy activities, Official Gazette of the Republic ofCraatia, No. 177/04, Zagreb 2004.

[4] NAVARRO, P.: Seven Basic Rules for the PBR Regulator, The Electricity Journal 9( 1996)3,24·30.

[5J KAHN, A.: The Economics of Regulation: Principles and Institutions, Cambridge, MA: MIT Press, 1988.

[6] COMNES, G. A.; STOFT S.; GREENE N.; HILL L.: Six Use/ill Observations lor Designers of PBR Plans, The Electricity Journal 9( 1996)3, 16·23.

[7] ROTHWELL, G.; GOMEZ, T.: Electricity Economics: Regulation and Deregulation, IEEE Press, 445 Hoes Lane, Piscataway, NJ 08854, PI'. 85·87, 2003.

[8J BANOVJ\C, E.: lvlonitoringgrllndlagen der kroatischen Regulierungsbe!J6rde jiir Ellergie, E\V - das Magazin fUr die Energie Wirtschaft 103(2004)1.2, [4·16.

[9] Directive 2004181EC of fhe European Parliament and of the Council on the promotion of cogeneration hased 011 a useful heat demand in the [mernal enClgy market and amending Directive 921421EEC, Official Journal of the European Union L 52/50, 2004.

[I OJ CEFIC, CEPI, COG EN, IFlEC, Joint statement on the CHP directive, 5 August 2005. \Vw\V.cogcn.orgl Down loadablcs/Publicationsl]oint _Statement on _the CHP _ Directive.090805.pdi'

480 Sadržaj za 2007. = Contents for 2007.

Časopis za teoriju i praksu u strojarstvu = Journal for Theory and Application in Mechanical Engineering = Журнал для машиностроителной теории и практики = Zeitschrift zur Theorie und Praxis des Maschinen wesens

ISSN 0562-1887 CODEN STJSAO UDK 62(05)=862=20=30 ZX 470/1281-1326

GodinaVolume 49 (2007) BrojeviNumbers 1− 6

Zagreb (Republic of Croatia)

Zbirni sadržaj

Konferencija KONSTRUIRANJE 2006 - I. dio M. M. Andreasen, H. Birkhofer, U. Lindemann, D.Marjanovići M. Mekhilef 4

Strategija preslikavanja konstrukcijskog procesa u primjenjiva programska rješenja - primjena CBR metodologije pri automatizaciji konstrukcijskog procesa (1281) M. Cederfeldt 7

Određivanje, vrednovanje i optimiranje parcijalnih rješenja pomoć faktora sličnosti (1282) M. Deimel i H. - J. Franke 15

Modeliranje i izrada krila vilinog konjica kao temelj bioničkog istraživanja (1283) T. Deubel, S. Wanke, C. Weber i F. Wedekind 25

Proto-teorija konstruiranja: metoda analize antičkih matematčara (1284) L. Koskela i M. Kagioglou 31

Od pogrešaka do mogućnosti - računalni sustav praćenja pogrešaka u praksi (1285) S. Möhringer 39

Podrška konstruktorima u procesu konstruiranja (1286) S. Ahmed 47

Konferencija KONSTRUIRANJE 2006 - II. dio M. M. Andreasen, H. Birkhofer, U. Lindemann, D.Marjanovići M. Mekhilef 54

Ontologija razvoja proizvoda u okruženju za implementaciju sljedljivosti (1287) N.Pavković,M.Štorga i N.Bojčetić 57

Unaprijeđivanje timskog inovacijskog proces podupiranjem refleksije (1288) KostanijaPetrović,A.Mueller i Britta Herbig 65

Značaj korisnosti informacija - percepcija konstruktora (1289) J. Restrepo 69

Metoda prilagodbe vrijednosti (1290) T. Sakao, Y. Shimomura, M. Comstock i E. Sundin 77

Sustav simuliranja okoliša za ekološki osviješteno konstruiranje proizvoda (1291) K. Sakati i T. Mori 85

Prijedlog metode za profiliranje inženjerske dokumentacije (1292) P. J. Wild, S. J. Cullez, C. A. McMahon, M. J. Darlington i S. Liu 91

Dan Frana Bošnjakovića A.Galović 112

Eksperimentalna studija spremnika sunčeve energije (1293) A. Can, B. Karacavus i E. Buyruk 115

Eksergijska i entropijska analiza adijabatskog miješanja dviju struja istih idealnih plinova različitih temperatura i okolišnjeg tlaka (1294) A.Galović,S.Risović i MarijaŽivić 125

Numerička analiza prijenosno toplinskih karakteristika orebrenih površina (1295) D. Kaya, E. Buyruk, A. Can i A. Fertelli 137

Numeričko određivanje temperaturne raspodjele u segmentu konstrukcije broda za prijevoz asfalta (1296) IvankaBoras,S.Švaić i I.Gospić 145

Numerički pristup procjene karakteristika strujanja u pločastim izmjenjivačima topline (1297) D.Dović i S.Švaić 151

Primjena ugljičnog dioksida kao radne tvari u transkritičnom rashladnom procesu (1298) D.Hrastović,V.Soldo i M. Grozdek 161

Trodimenzionalna numerička simulacija stvaranja dušičnih oksida pri izgaranju mazuta u ložištu (1299) M.Vujanović,N.Duići A.Galović 169

Obnovljivi izvori energije u Hrvatskoj B.Franković 182

Sprječavanje pregrijavanja u zgradi male energetske potrošnje korištenjem tehnike slobodnog hlađenja (1300) C. Arkar i S. Medved 185

Sadržaj za 2007. = Contents for 2007. 481

Tehniči status mikrogeneracijskih uređaja s vodikovim gorivnim ćelijama (1301) M. Firak 193

Kondenzacija kod pločastih izmjenjivača topline zavarene konstrukcije tipa Exel (1302) S. Meziani, M. Altazin, R. Jurkowski i A. Bailly 207

Potencijal za primjenu PV sustava na hrvatskim otocima bez struje (1303) M.Rakić,DunjaDesnica-Franković i U.V.Desnica 217

GENHEPI koncept: Nova metodologija za obnovu zgrada sa malom potrošnjom energije i demonstracijski program (1304) L.Sarrade,A.Manificat,D.Corgier i F. Burgun 225

Analiza ukupne učinkovitosti solarne dimnjačne elektrane (1305) S.Nižetić i N.Ninić 233

Analiza prijenosa topline u brodskim tankovima tereta (1306) B.Jandrijević,T.Mrakovčić i N.Račić 241

Numerička simulacija tvorbe čaže u dizelskom motoru (1307) T.Senčić,O.Bukovac i V.Medica 249

Nuklearna energija, da ili ne? Osvrt na glavna pitanja (1308) V.Knapp 261

Studij rada - jučer, danas, sutra D. Taboršak 280Približna rješenja teorije ljusaka u proračunu čvrstoće sfernih tlačnih posuda (1309) P.Baličević,D.KozakiI.Samardžić 281Klasifikacija čimbenika organizacije (1310) M.Ikonić,T.MikaciI.Veža287

Eksperimentalna studija topografije površine izrađene abrazivnim rezanjem vodenim mlazom(1311) S. Hloc, J. Valíček,I.Samardžić,D.Kozak, J. Mullerová i M. Gombár 303Utjecaj starenja na mehaničke karakteristike smolasto vezanih brusova (1312) A. Matavz, J. Krope, D. Goricanec i N. Gubeljak 311Provjera konstrukcijskog oblika i zamorne čvrstoće koljenastog vratila rednih i V brodskih dizel motora (1313) N.Vulić,A.ŠestaniV.Cvitanić 317

Eksperimetalno određivanje značajki uređaja sa zvonom (1314) T.Stašić,N.Degiulii L. Grgec Bermanec 333Neke posljedice hrvatske šutnje I.Čatić 350Numeričke simulacije strujanja u vodotocima sa slobodnom površinom (1315) S.Družeta 351Kvantifikacija čimbenika organizacije (1316) M.Ikonić,T.MikaciA.Vuković 361Ergonomski stresovi varioca (1317) J.Horvat,I.Polajnar,M.Čudinai Raja Gošnak-Dahmane 377Numeričke simulacije strujanja hidrauličkih tranzijenata u cijevima s primjenom u hidroelektranama (1318) J.Škifić 383Spektroskopska analiza X zrakama za predmete kulturne baštine (1319) V.Desnica,S.Fazinić,Ž.PastulovićiM.Jakšić393Današnja i buduća uloga plina u energetici Republike Hrvatske M.Šunić408Odabir optimalnog pristupa određivanju metodologije Tarifnog sustava za toplinarske djelatnosti (1320) E.Banovac,Ž.BogdaniI.Kuzle 409Metodologija utvrđivanja naknade priključenja na toplinsku mrežu (1321) M.Klepo,M.KostelaciA.Ćurković421Model za određivanje pokazatelja pouzdanosti distribucijske mreže za različite scenarije financijskih ulaganja (1322) V.Komen 431Parametrična analiza kogeneracijskog sustava sa stirlingovim motorom (1323) U.Stritih,G.ZupaniV.Butala 441Povećanje energetske efikasnosti ugradnjom novih plinskih uređaja (1324) M.ŠunićiN.Kukulj 449Aktualno stanje ADRIA LNG projekta (1325) S.KojundžićiA.Lopac 461Stanje i razvoj pravno-institucijskog okvira za poticanje obnovljivih izvora energije (OIE) i kogeneracije u Republici Hrvatskoj (1326) I. Raguzin 469

Cumulative ContentsDESIGN 2006 Conference - Part I M. M. Andreasen, H. Birkhofer, U. Lindemann, D.Marjanovićand M. Mekhilef 3

Towards a Strategy for Mapping of Design Problems to Suitable Solutions - a Case of Design Automation Using CBR (1281) M. Cederfeldt 7

Using Similaritz Rations for Finding, Evaluating and Optimizing Principle Solutions (1282) M. Deimel and H. - J. Franke 15

Modelling and Manufacturing of a Dragonfly Wing as Basis for Bionic Research (1283) T. Deubel, S. Wanke, C. Weber and F. Wedekind 25

482 Sadržaj za 2007. = Contents for 2007.

The Proto-theory of Design: the Method of Analysis of the Ancient Geometers (1284) L. Koskela and M. Kagioglou 31

From Design Errors to Chances - a Computer-based Error Tracking System in Practice (1285) S. Möhringer 39

Prompting Designers to Design (1286) S. Ahmed 47

DESIGN 2006 Conference - Part II M. M. Andreasen, H. Birkhofer, U. Lindemann, D.Marjanovićand M. Mekhilef 53

Product Development Ontology in Tracebility Implementation Framework (1287) N.Pavković,M.Štorga and N.Bojčetić 57

Improving the Product Innovation Process ina Teams by Supporting Reflection (1288) KostanijaPetrović,A.Mueller and Britta Herbig 65

Assessing Relevance: Designers' Perception of Informaton Usefulness (1289) J. Restrepo 69

A Method of Value Customization (1290) T. Sakao, Y. Shimomura, M. Comstock and E. Sundin 77

Environmental Simulation System for Enviromnentally Conscious Product Design (1291) K. Sakati and T. Mori 85

Towards a Method for Profiling Engineering Documentation (1292) P. J. Wild, S. J. Cullez, C. A. McMahon, M. J. Darlington and S. Liu 91

Fran Bošnjaković's Day A.Galović 111

An Experimental Study on Solar Energy Storage (1293) A. Can, B. Karacavus and E. Buyruk 115

Exergy and Entropy Analysis of Adiabatic Mixing of Two Streams of Identical Ideal Gases at Different Temperatures and Environmental Pressure (1294) A.Galović,S.Risović and MarijaŽivić 125

Numerical Study of Heat Transfer Characteristics of Extended Surfaces (1295) D. Kaya, E. Buyruk, A. Can and A. Fertelli 137

Numerical Determination of Temperature Distribution at Asphalt Carrier Ship Structure (1296) IvankaBoras,S.Švaić and I.Gospić 145

Computational Approach to Evaluation of the Flow Characteristics in Plate Heat Exchangers (1297) D.Dović and S.Švaić 151

Application of Carbon Dioxide in a Transcritical Refrigeration Cycle (1298) D.Hrastović,V.Soldo and M. Grozdek 161

Three-dimensional Numerical Simulation od the Nitrogen Oxides Formation in an Oil-fired Furnace (1299) M.Vujanović,N.Duićand A.Galović 169

Renewable Energy Sources in Croatia B.Franković 181

Overheating Prevention of a Low Energy Building Using Free Cooling Technique (1300) C. Arkar and S. Medved 185

Technical Satus of the Micro-Cogeneration Units with Hydrogen Fuel Cells (1301) M. Firak 193

Condensation in Brazed Plate Heat Exchangers Exel (1302) S. Meziani, M. Altazin, R. Jurkowski and A. Bailly 207

Potential for off-grid PV Applications on Croatian Islands (1303) M.Rakić,DunjaDesnica-Franković and U.V.Desnica 217

GENHEPI Concept: A new Methodology for Low Energy Consumption Building Renovation and Demonstration Program (1304) L.Sarrade,A.Manificat,D.Corgier and F. Burgun 225

Analysis of Overall Solar Chimney Power Plant (1305) S.Nižetić and N.Ninić 233

Analysis of the Heat Transfer in the Ships' Cargo Tanks (1306) B.Jandrijević,T.Mrakovčić and N.Račić 241

Numerical Simulation of Soot Formation in Diesel Engine (1307) T.Senčić,O.Bukovac and V.Medica 249

Nuclear Energy, yes or no? Comments on the Main Issues (1308) V.Knapp 261

Work Study – Yesterday, Today and Tomorrow D. Taboršak 279The Approximate Solutions of the Theory of Shells in Calculating Strength of Spherical Pressure Vessels (1309) P.Baličević,D.KozakandI.Samardžić 281Classification of Organizational Factors (1310) M.Ikonić,T.MikacandI.Veža287Experimental Study of Surface Topography Created by Abrasive Waterjet Cutting (1311) S. Hloc, J.Valíček,I.Samardžić,D.Kozak, J. Mullerová and M. Gombár 303The Impact of Ageing on Mechanical Characteristics of Resin Bonded Wheels (1312) A. Matavz, J. Krope, D. Goricanec and N. Gubeljak 311Verification of Crankshaft Design and Fatigue Strength for in-line and v-type Marine Diesel Engines (1313) N.Vulić,A.Šestanand V.Cvitanić 317Experimental Characterisation of a Bell Prover (1314) T.Stašić,NastiaDegiuliand L. Grgec Bermanec 333Some consequences of the Croatian silence I.Čatić 349

Sadržaj za 2007. = Contents for 2007. 483

Numerical Simulations of Free Surface Flow in Open Channels (1315) S.Družeta 351Quantification of Organizational Factors (1316) M.Ikonić,T.MikacandA.Vuković 361Ergonomic Stresses of Welders (1317) J.Horvat,I.Polajnar,M.Čudinaand Raja Gošnak-Dahmane 377Numerical simulations of hydraulic transients in pipelines with application to hydroelectric power plants (1318) J.Škifić 383PIXE Spectroscopy for Analysis of Cultural Heritage Objects (1319) V.Desnica,S.Fazinić,Ž.Pastulovićand M.Jakšić393Present and Future Role of Gas in Energy Industry of the Republic of Croatia M.Šunić407Choosing the Optimal Approach to Define the Methodology of a Tariff System for Thermal Energy Activities (1320) E.Banovac,Ž.Bogdanand I. Kuzle 409

Methodology of Charges for Connection to Thermal Networks (1321) M. Klepo, M. Kostelac andA.Ćurković421A Model for Determination of Distribution Network Reliability Indices for Different Financial Investment Scenarios (1322) V.Komen 431Parametrical Analysis of Cogeneration System With Stirling Engine (1323) U. Stritih, G. Zupan andV.Butala 441Energy Efficiency Increase by Using New Gas-Fired Equipment (1324) M.Šunićand N. Kukulj 449ADRIA LNG – Current Situation (1325) S.KojundžićandA.Lopac 461State and Development of Legaland Institutional Framework for Promotion of Renewable Energy Sourcesand Cogeneration in the Republic of Croatia (1326) I. Raguzin 469

Zbirno kazalo autora i rubrika (polumasno otisnuti brojevi označavaju početnu stranicu izvornog recenziranog rada a podvučeni početnu

stranicu uvodnika)

Cumulative Author and Heading Index (The numbers printed in bold mean the inital page of original reviewed paper and the underlined mean

the initial page of leading article)

Ahmed, Saeema 47Altazin, M. 207Andreasen, M 3, 4, 53, 54Arkar, Ciril 185

Bailly, A. 207Baličević, Pavo 281Banovac, Eraldo 409Birkhofer, H 3, 4, 53, 54Bogdan, Željko 409Bojčetić, N. 57Boras, Ivanka 145Bukovac, Ozren 249Burgun, Françoise 225Butala, Vincenc 441Buyruk, Ertan 115, 137

Can, Ahmet 115, 137Cederfeldt, Mikael 7Comstock, Mica 77Corgier, David 225Culley, S. J. 91Cvitanić, Vedrana 317

Čatić, Igor 349, 350Čudina, Mirko 385

Ćurković, Ante 421

Darlington, M. J. 91Deimel, Markus 15Degiuli, Nastia 333Desnica, Uroš V. 217Desnica, Vladan 393Desnica-Franković, Dunja 217Deubel, Till 25Dović, Damir 151Družeta, Siniša 351Duić, Neven 169

Fazinić, Stjepko 361Fertelli, Ahmet 137Firak, Mihajlo 193Franke, Hans-Joachim 15Franković, Bernard 181, 182

Galović, Antun 111, 112, 125, 169

Gombár, Miroslav 303Gospić, Ivan 145Gošnak-Dahmane, Raja 385Goricanec, Darko 311Grgec Bermanec, Lovorka 333Grozdek, Marino 161Gubeljak, Nenad 311

Herbig, Britta 65Horvat, Jožef 377Hloch, Sergej 303Hrastović, Dario 161

Ikonić, Milan 287, 361IN MEMORIAM 101, 177, 271, 343, 401, 477

Jakšić, Milko 361Jandrijević, Bojan 241Jurkowski, R. 207

Kagioglou, M. 31Karacavus, Berrin 115

484 Sadržaj za 2007. = Contents for 2007.

Kaya, Derya 137Klepo, Mićo 421Knapp, Vladimir 261 Komen, Vitomir 431Koskela, Lauri 31Kostelac, Milan 421Kozak, Dražen 281, 303Krope, Jurij 311Kolundžić, Stevo 461Kukulj, Nenad 449Kuzle, Igor 409

Lindemann, U. 3, 4, 53, 54Liu, S. 91Lopac, Andreja Ana 461

Manificat, André 225Marjanović, D. 3, 4, 53, 54Matavz, Albin 311McMahon, C. A. 91Medica, Vladimir 249Medved, Sašo 185Mekhilef, M 3, 4, 53, 54Meziani, S. 207Mikac, Tonči 287, 369Mori, T. 85Mrakovčić, Tomislav 241Mueller, Andreas 65Mullerová, Jana 303Möhringer, Stefan 39

Ninić, Neven 233Nižetić, Sandro 233

OSVRTI I MIŠLJENJA / VIEWS AND RETROSPECTIONS 346, 392

Pastuović, Željko 361Pavković, Neven 57Petrović, Kostanija 65Polajnar, Ivan 385

Račić, Nikola 241Raguzin, Igor 469Rakić, Mario 217Restrepo, John 69Risović, Stjepan 125

Sakao, Tomohiko 77Sakita, K. 85Samardžić, Ivan 281, 303Sarrade, Laurent 225Senčić, Tomislav 249Shimomura, Yoshiki 77Soldo, Vladimir 161Stašić, Tomislav 333Stritih, Uroš 441

SKUPOVI / CONFERENCES 269Sundin, Eundin 77

Šestan, Ante 317Škifić, Jerko 383Štorga, M. 57Šunić, Miljenko 407, 408, 449Švaić, Srećko 145, 151

Taboršak, Dragutin 279, 280

UDRUGE / ASSOCIATIONS 344, 403

Valíček, Jan 303Veža, Ivica 287

VIJESTI SA SVEUČILIŠTA / NEWS FROM UNIVERSITY 403

Vujanović, Milan 169Vuković, Aleksandar 369Vulić, Nenad 317

Zupan, Gregor 441

Živić, Marija 125

Wanke, Sören 25Weber, Christian 25Wedekind, Frank 25Wild, Peter J. 91