Ioan Giurca

In the paper are presented the economic criteria on the basis of which the choice of selection of energetics modernization measures of existing buildings is made. The paper describes a synthesis of economic criteria from Romania and abroad on the basis of which the choice of technical solutions concerning the energetics modernization of existing buildings is made. Based on the article’s conclusions, one can make proposals aimed at improving the legislation presently in force in this field.

In this paper we analyze the way of choosing the technical solutions concerning the supply of thermal energy for residential groups of buildings, using the Multicriterial Ordinal Ranking Model, the Relative Distance Comparison model in relation with the maximum performance and the Relative Distance Comparison model in relation with the average performance.  The paper ends with the presentation of the numerical results and a few conclusions. The models proposed may be used in practice in case of feasibility studies, for master degree theses as well as for Ph.D. theses.

The present article presents the methodology for establishing the performances of central heating installations for residential buildings. The presented method can be used for performance evaluation of materials, equipments, boilers, heating stations, heating networks, indoor central heating systems, or even for an entire central heating system. This article has been written in light of underlining the methods for establishing the performances of central heating systems using the “performances global evaluation method”. This work is among the first of this kind in Romania. The research methods employed are: deduction and analysis. Through analogy, the method can be used for establishing the performances of other type of installations for constructions.

Presently within International Auctions, in choosing the equipments to be installed for heating systems, the Product Life Cycle Value Evaluation Method is being used in Romania, this method is poorly known and seldom used in the field of installations for constructions. Based on sustainable development, this work tackles the possibility of using Green Public Procurement in the field of central heating systems installations. The optimum solution will be the one with the minimum investment and operating costs. The method presented in this article can be used for choosing the next equipments for the installations for constructions: boilers, pumps, fans, blowers, compressors. Considering the above, we suggest using this method in choosing the equipments to be fitted in installations for constructions.

In this paper, there is presented the choice for optimum method as concerning boilers, by using global evaluation of performances. In the end there is made a comparison of the results obtained by the author in contrast to those obtained by other authors as a conclusion under the supervision of Electre method. On the base of this study it is clearly presented the choice of technical solution that can be influenced by: chosen Mathematical pattern, type of chosen scale for quality features, importance criteria given to the decisional criteria.

This paper synthetically presents the steps and the main elements to be taken into account by construction installation engineers when they design circulation pipes for domestic hot water. By this paper, we propose a new method concerning the calculation of the domestic hot water circulation pipe. Basically, after determining the circulation flow, the diameter of the circulation pipe is determined based on the economic speed of the most disadvantaged section, and for the remaining sections, the diameters are determined depending on the pressure available at the branch points. The method proposed by the author in this article may be used in order to design domestic hot water circulation pipes, in case of secondary thermal networks made with pre-insulated pipes directly embedded in soil.

This paper analyses the selection of radiators using the method of the degree of belonging to the optimal variant. This paper is among the first tries of this type from Romania. A case study shows the practical application of this algorithm. The paper ends with the presentation of the numerical results and a few conclusions. The models proposed may be used in practice in case of feasibility studies, for master degree theses as well as for Ph.D. theses. The method of degree of belonging to the optimal variant can also be used for the selection of other types of materials for the installations related to the constructions.

This paper represents a synthesis of the legislation, of the Romanian and foreign scholarly literature related to the selection of hot water boilers, as well as of their respective burners. This paper is among the first tries of this type from Romania. The conclusions of this paper are useful both for the designers as well as for the beneficiaries, in order for them to choose hot water boilers, and their respective burners. The proposed method has a practical use in case of feasibility studies, master degree theses, as well as of Ph.D. theses.

This paper represents a synthesis of the legislation, of the Romanian and foreign scholarly literature related to the output of hot water boilers. This article proves the existence of different output values both in relation with the Romanian prescriptions as well as in relation with various European prescriptions. The conclusions of this article are useful for the designers as well as for the beneficiaries, in order for them to choose hot water boilers.

In this paper, we will discuss how to choose heating units using the Electre function. Chapter 2 presents the computation methodology. A case study underlines the way in which one can apply the mathematical model into practice. This paper presents outline and results of these calculations.

In this paper we analyze the priorities concerning the sewage network rehabilitation using the  Onicescu method. The paper ends with the presentation of the numerical results and a few conclusions. The  method proposed may be used during the feasibility studies for the sewage networks. The method proposed  may be used during the feasibility studies for the sewage networks. 

The article presents aspects related to the calculation of heat loss through the pipes of the interior central heating system. The purpose of the article is to detail the local heat losses in case of central heating systems. Based on the conclusions of the article, we propose the modification of the calculation methodology related to the building energy audit.

In this paper, we will discuss how to choose heating units using the utility function. This paper is conceived as a detailed continuation of the analysis made by the authors in their doctoral thesis. This paper is among the first tries of this type from Romania. A case study shows the practical application of this algorithm, and the results obtained were compared to the results obtained by other authors. The paper ends with the presentation of the numerical results and a few conclusions. We are also presenting several directions for future research in this field.

The production of renewable energy using the concentrated solar radiation is a field of high scientific level worldwide, while in Romania the research in this field is only in its early stages. In this paper, in order to select the type of photovoltaic system, we suggested the use of multi-criteria methods, where the utilities are determined based on the Neumann-Morgenstern utility theorem, and the importance coefficients are determined based on the Entropy method. According to the elaborated study, we recommend the implementation into practice of the alternative A3, namely the technical solution involving concentrator photovoltaic panels with dual-axis tracker. The conclusions of this study are useful both for the designers of photovoltaic systems as well as for the potential beneficiaries of photovoltaic systems. Obviously, this method can also be used in case of other investment projects from related fields.

The selection of the optimal solution regarding the concentration ratio is a complex process, as it depends on a very high number of criteria. The production of renewable energy using the concentrated solar radiation is a field of high scientific level worldwide, while in Romania the research in this field is only in its early stages. The purpose of this document is to present a classification method for photovoltaic systems taking into account the concentration ration. The paper tries to fill in a gap in the field of choosing the photovoltaic systems from the concentration ratio perspective. Based on the study performed, we recommend using the variant A4, namely the technical solution consisting of a photovoltaic system with a 1000x concentration ratio.

In this paper the technical criteria for choosing the optimal fuel cell for application in stationary field is presented, being developed particularly for application in passive houses domain. In this matter the initial context has been set, respectively the technical characteristics of object to which implementation of a system based upon the fuel cell is wanted, and also the specific characteristics of fuel cells and the decision criteria of the technical solution have been set. In order to choose the right version, two multicriteria methods to rationalise the decision have been applied, after analyzing the existent typologies and establishing the compatible versions with the demands from the stationary domain, and in the end the obtained results have been compared.

Selection and sizing of heating and sanitary hot water solar system for a building always involves determining the optimal rate of heat provided by solar energy conversion. As this rate is higher, a greater amount of fossil fuels is saved and the pollutant emission and greenhouse gases emission decreases. But this may involve, during the summer, the producing of a quantity of heat, greater than heat demand of the building, resulting an excess of heat that involves additional energy management costs with negative impact on the annual energy efficiency of solar thermal system. In the final part of this article, it was presented a case study on the use of an solar system for indirect preparation of sanitary hot water and for supporting the space heating for a building for tourism.

In this article, we study the possibility of using the PROMETHEE method when choosing multi-junction photovoltaic panels. The study performed proves that the PROMETHEE method may be used for selecting technical solutions in case of multi-junction photovoltaic panels, as well as in case of other types of construction installation works. This article fills a void when it comes to choose the technical solutions for construction installation works.

The purpose of this article is to present a method of selecting hydrogen-production systems using the electric power obtained in photovoltaic systems, and as a selecting method, we suggest the use of the Advanced Multi-Criteria Analysis based on the FRISCO formula. According to the case study on how to select the solar radiation hydrogen production system, the most convenient alternative is the alternative A4, namely the technical solution involving a hydrogen production system based on the electrolysis of water vapor obtained with concentrated solar thermal systems and electrical power obtained using concentrating photovoltaic systems.

This article aims to describe a method regarding the selection of technical solutions for thermal and energy rehabilitation and modernization of buildings, for this purpose the TOPSIS method being used. In this article we also included a case study concerning the use of TOPSIS method in case of energy audit for buildings. The article concludes that TOPSIS may be used for energy audit projects for buildings. Based on the article's conclusions, we are making proposals in order to improve the actual legislation in the field of building energy audit.

Abstract
This paper develops for the first time in the field of the solar technologies, the concept of a system that can simultaneously produce more than three types of energy. This is possible due to the modular conception, namely the conception of standardized modules as a solution for attracting and concentrating the solar radiation, but also different depending on the component which converts the energy. The study meets the European Union’s policy whose target is the transition to an economy based on hydrogen produced from renewable sources by the middle of the 21st century. According to this study, starting with 2030 it is possible that the price of hydrogen may be competitive as compared to the price of heavy oil.
© 2016 The Authors. Published by Elsevier Ltd.
Peer-review under responsibility of the “Petru Maior” University of Tirgu-Mures, Faculty of Engineering.

Keywords: photovoltaic energy; photovoltaic systems; hydrogen; technical analysis; financial analysis.

In this paper the authors intend to solve in a scientific way, using the AHP method, a problem faced by companies in the field of water supply in towns, and choosing the technology of pipe rehabilitation in water distribution systems. This paper presents a case study on the selection of the technology for the rehabilitation of domestic water distribution network in Cluj-Napoca. We used the AHP method in order to rank the priorities regarding the rehabilitation of water distribution network. Based on the study performed, we recommend using the Slipline method for the rehabilitation of water distribution pipes in Cluj-Napoca, Romania. The method presented in this paper may be used for the feasibility studies elaborated for water distribution networks. Also, the AHP method may be correspondingly used for the selection of other types of installations for buildings.

This paper presents a case study concerning a plant for hydrogen production and storage, having a daily capacity of 100 kg. The plant is located in Cluj-Napoca, Romania. It produces hydrogen by means of water electrolysis, while the energy is provided using solar energy. We performed the calculations for four different technical solutions used for the hydrogen production and storage plant, and also we considered three scenarios regarding the subsystems of the hydrogen production and storage plant efficiency. The conclusion of this study is that one can maximize the conversion of solar radiation into chemical energy in the form of hydrogen by hybridizing the solar hydrogen production system, namely using both electrical energy as well as thermal energy in the form of steam.

This paper focuses on the selection of number and size of boilers required for the heating units of the residential complexes. In this case study we proposed the selection of number and dimension of boilers for a heating unit of a residential complex located in Tirgu-Mures, Romania. The conclusion of this study is that the operational safety of the heating unit increases once the number of boilers increases, together with the decrease of thermal energy consumption and the increase of investment costs respectively. Based on our calculations, we recommend that the heating unit should be equipped with seven boilers, and should be provided with a controller for managing them in cascade. The method proposed in this paper can be used within the feasibility studies related to heating units of the residential complexes.

This paper analyses the selection of priorities in case of the rehabilitation of water distribution networks. The ranking of the technical solutions was performed using the Leader method. This paper also presents a case study regarding the rehabilitation of water distribution network in Cluj-Napoca, Romania. The result of this study shows that the rehabilitation of water distribution network in Cluj-Napoca, Romania has to begin with the substitution of asbestos cement pipes.