Design and Operation of a Polygeneration System in Spanish Climate Buildings under an Exergetic Perspective

This work defines and analyzes the performance of a polygeneration system in five different locations in Spain to maintain the thermal comfort and air quality of an office building. The facility is based on a chiller and a CHP engine with PV panels that provide almost all the electricity demand of the chiller. According to the energy performance analysis results, the installation working in Bilbao is a full polygeneration system since no electricity needs to be imported from the grid in summer. To quantify the energy savings related to a separated production facility, polygeneration indicators (percentage of savings PES/PExS and equivalent electric efficiency EEE/EExE) have been calculated in energy and exergy terms. The main motivation for using exergy is based on the ambiguity that can arise from the point of view of the First Law. As expected, the exergetic indicators have lower values than the energetic ones. In addition, an in-depth analysis was conducted for the air-handling unit components. The study shows the behavior of components over the year and the efficiency values from both an energy and exergy point of view. From these facts, the need arises to develop methodologies based on exergy

Application of Thermoeconomics in HVAC Systems

In order to achieve a sustainable society, the energy consumption in buildings must be reduced. The first step toward achieving this goal is to detect their weak points and analyze the energy-saving potential. to detect the units with higher consumption and cost. Exergy is very useful for analyzing pieces of equipment, systems or entire buildings. It measures not only the quantity of energy but also its quality. If the exergy is combined with economic analysis, this gives rise to thermoeconomics, and the system can be checked systematically and optimized from the perspective of economics. In this work, exergy methods and thermoeconomic analysis were applied to a building thermal system. Due to its complexity, it is necessary to adapt some concepts to translate the exergy application from industry to buildings. The purpose of this work is to overcome these shortcomings and to deal with energy-saving actions for buildings. To this end, a thermoeconomic study of a facility that covers the heating and domestic hot water (DHW) demands of 176 dwellings in Vitoria-Gasteiz (Basque Country) using two boilers and two cogeneration engines was analyzed. The irreversibility associated with each piece of equipment was quantified, and the costs associated with resources, investment and maintenance were calculated for each flow and, consequently, for the final flows, that is, electricity (11.37 c€/kWh), heating (7.42 c€/kWh) and DHW (7.25 c€/kWh). The results prove that the boilers are the lesser efficient components (with an exergy efficiency of 15%). Moreover, it is demonstrated that micro-cogeneration engines not only save energy because they have higher exergy efficiency (36%), but they are also economically attractive, even if they require a relatively high investment. Additionally, thermoeconomic costs provide very interesting information and underscore the necessity to adapt the energy quality in between the generation and demand

Development of a tool based on thermoeconomics for control and diagnosis building thermal facilities

[EN] This work develops a software to control and diagnose building thermal facilities based on thermoe-conomics. It is tested with the data obtained from three building blocks in the Basque Country (northern Spain) with the aim of detecting the potential energy saving points and mitigating environmental im-pacts. Some obstacles, solved, are related to the insufficient number of probes and the inherent errors of sensors. Besides, new methodologies for performing a thermoeconomic dynamic analysis are described. Apart from this, the inefficiencies of components are quantified, a dynamic cost calculation of all fiows is done and different operation modes are discussed. The outcomes of operation modes are discussed and their exergetic, economic and environmental average unit cost are calculated. In such way, the inter-vention of the control system is analysed and the operation modes with lower and higher fuel con-sumption are detected. The results show that domestic hot water (DHW) production has an average value of 13.72 c euro /kWh and heating of 12.92 c euro /kWh; in addition, boilers have 1,587 MWh of real losses. Besides, the operating modes dynamic analysis opens a new research line for thermoeconomics appli-cations. This information is a key fact for control optimization searching the high performance of buildings.The authors appreciate the financial support provided for this work by the Basque Government through the ERAIKAL 2019 project. The authors also acknowledge the support provided by the Laboratory for the Quality Control in Buildings of the Basque Government

Eguzki-energia termikoa: etxebizitzen eskariak asetzeko erabilera anitzeko iturri-berriztagarria

The aim of this paper is to provide information on the current situation of solar collectors in the building sector. Solar thermal energy is a key for the energy transition, so it is necessary to know the technologies of exploitation of the source and its operating ranges, taking into account, especially, the current situation of solar energy in Spain and the specific installations in buildings. Although conventional solar systems are currently installed, there are other less common configurations. For this reason, the findings of recent years must be taken into account in order to introduce new materials, geometries and heating fluids for solar collectors. In addition, solar systems can be integrated into architectural elements and solar cooling applications and air conditioning networks can be promoted. Consequently, it is demonstrated that the thermal applications of solar energy are versatile and adaptable for any building thermal demand.; Lan honen helburua da eguzki-kolektoreen egungo egoeraren informazioa ematea, eraikuntza-sektorean. Energia-trantsiziorako giltzarri bat da eguzki-energia termikoa, eta, horregatik, iturria ustiatzeko teknologiak eta horien funtzionamendu-tarteak ezagutu behar dira, kontuan hartuz, batez ere, Espainiako eguzki-energiaren egungo egoera eta eraikinen instalazio espezifikoak. Egun, ohiko eguzki-sistemak instalatzen badira ere, hain ohikoak ez diren beste konfigurazio batzuk ere badaude. Hori dela eta, azken urteen aurkikuntzak aintzat hartu behar dira eguzki-kolektoreen material, geometria eta fluido bero-eramaile berriak ezagutarazteko. Gainera, eguzki-sistemak elementu arkitektonikoetan integra daitezke, eta eguzki bidezko hozte-sistemen aplikazioak eta klimatizazio-sareak ere bultza daitezke. Ondorioz, eguzki-energiaren aplikazio termikoak aldakorrak eta moldagarriak direla frogatzen da, eraikuntzako edozein eskari termikorako

Optimization of the Heating System Use in Aged Public Buildings via Model Predictive Control

This work presents the implementation of a Model Predictive Control (MPC) scheme used to study the improvement of the thermal quality in aged residential buildings without any rehabilitation. The controller manages the heating system of an experimentally characterized model of a residential dwelling in a social block built during the decade of the 1960s located in the neighborhood of Otxarkoaga (Bilbao, Spain), so as to obtain an optimal energy efficiency performance. Due to the characteristics of the construction in those days, this kind of buildings suffer problems related to the use of awkward building materials and inefficient heating systems. A comparison with traditionally used ON-OFF hysteresis control is presented in order to demonstrate the energetic improvement provided by the MPC scheme. Besides, the variation of different parameters of the MPC is also studied to determine its influence over the energy consumption and comfort conditions.The authors would like to acknowledge the collaboration of the Basque Energy Board (EVE) through Agreement UPV/EHUEVE23/6/2011 and the Spanish National Fusion Laboratory (CIEMAT) UPV/EHUCIEMAT08/190. Authors are also very grateful for the partial financial contribution to the UPV/EHU and EJ/GV through projects GIU14/07 and IT987-16, as well as to the FEDER and MINECO through project DPI2015-70075-R

Combination of Diagnostic Tools for the Proper Identification of Moisture Pathologies in Modern Residential Buildings

A study of moisture pathologies in a modern residential multifamily building is presented. The housing block was designed under the regulation NBE-CT of 1979 in northern Spain. After the appearance of some moisture problems in the façades, three complementary studies were conducted to analyze the situation of the envelope and diagnose the best improvement possibilities. First, indoor conditions of temperature and humidity of the apartments with moisture pathologies were monitored. During 40 winter days, the occupancy, heating operation, and natural ventilation were analyzed. Second, the inner and outer surface temperatures of the studied façades were measured. Thermal insulation degree, thermal capacity, and thermal bridge effects were measured to assess the risk of interstitial condensation under the real conditions of use. Third, an infrared thermographic survey was carried out, which allowed the detection of irregularities and the assessment of moisture problems. The wrong interpretations, which would have been made if the complementary studies had not been done, are exposed. The key towards the accurate diagnosis was the combination of tools. Finally, some technical solutions based on ventilation or thermal insulation enhancement are proposed as different ways to reduce the high levels of relative humidity indoors and minimize the risk of condensation in the futur

Instalazio termiko hibrido baten energia- eta exergia-analisi dinamikoa

Climate change is modifying the energy demand everywhere. This influences the way in which energy demand supply systems are sized and how they work, especially in systems designed for the long term. Thus, it is urgent to know the sources of renewable energy to exploit them in a sustainable way and to do so with systems that adapt their exploitation to the requirements of climate change. The system that mixes these two requirements is the heat pump. The heat pump is capable of exploiting energy sources close to the surrounding temperature and is an ideal technology for meeting the energy needs of applications with low thermal requirements. The energy demand of buildings is high, but domestic hot water for buildings and heating have a low thermal demand. Thus, the use of heat pumps in the thermal facilities of buildings ensures the energy transition and the flexibility to adapt to the new climate change scenario. In order to reduce energy demand as much as possible, it is necessary to know the degradation mechanisms of energy resources. Energy and exergy analyses are very useful tools to know the exergy destruction and the energy and exergy efficiency of a system. This paper presents a real hybrid facility containing in the generation block a ground-coupled heat pump and a gas boiler. The facility supplies a building with domestic hot water and heating. The dynamic simulation of the facility has been carried out with TRNSYS software and data for the application of energy and exergy analysis have been obtained. For the first time, a dynamic exergy analysis has been applied to a system consisting of a ground source heat pump and a gas boiler. The results obtained indicate that 71% of the exergy destruction occurs in the boiler and the exergy efficiency of the heat pump is 6%. The results obtained allow to improve the energy performance of this thermal facility.; Klima-aldaketaren eraginez, tokian tokiko energia-eskaria aldatzen ari da. Horrek energia-eskaria asetzeko sistemen dimentsionamenduan eta operazio-moduan eragiten du; batez ere, epe luzerako proiektatzen diren sistemetan. Hala, premiazkoa da jatorri berriztagarria duten energia-iturriak ezagutzea, modu jasangarrian ustiatzea eta ustiaketa klima-aldaketaren eskakizunetara egokituko diren sistemekin egitea. Bero-ponpak bi baldintza horiek bateratzen ditu. Bero-ponpa inguru-tenperaturatik gertu dauden energia-iturriak ustiatzeko gai da eta eskakizun termiko baxua duten aplikazioen energia-beharrak asetzeko aproposa den teknologia da. Eraikinen energia-eskaria handia da, baina eraikinetarako ur bero sanitarioak eta berokuntzak eskakizun termiko baxua dute. Horrela, eraikinen instalazio termikoetan bero-ponpa edukitzeak, energia- trantsizioa eta klima-aldaketaren agertoki berrira egokitzeko malgutasuna bermatzen ditu. Energia-eskaria ahalik eta gehien murrizteko, energia-baliabideen degradatze-mekanismoak ezagutu behar dira. Energia- eta exergia-analisiak oso tresna erabilgarriak dira sistema baten exergia-suntsiketa eta energia- eta exergia-efizientzia ezagutzeko. Lan honetan, sorkuntza-sisteman lurzorura akoplatutako bero-ponpa bat eta gas-galdara bat dauzkan instalazio hibrido erreal bat aurkezten da. Instalazioak ur bero sanitarioz eta berokuntzaz hornitzen du eraikin bat. TRNSYS softwarearen bitartez, instalazioaren simulazio dinamikoa burutu da eta energia- eta exergia-analisia aplikatzeko datuak lortu dira. Lehen aldiz, exergia-analisi dinamikoa aplikatu da. Lortutako emaitzen arabera, exergia-suntsiketaren % 78 galdaran gertatzen da, eta bero-ponparen exergia-efizientzia % 46koa da. Lortutako emaitzek zabaldu egiten dute instalazio termiko honen energia-portaera hobetzeko bidea

Energy Conservation in an Office Building Using an Enhanced Blind System Control

The two spaces office module is usually considered as a representative case-study to analyse the energetic improvement in office buildings. In this kind of buildings, the use of a model predictive control (MPC) scheme for the climate system control provides energy savings over 15% in comparison to classic control policies. This paper focuses on the influence of solar radiation on the climate control of the office module under Belgian weather conditions. Considering MPC as main climate control, it proposes a novel distributed enhanced control for the blind system (BS) that takes into account part of the predictive information of the MPC. In addition to the savings that are usually achieved by MPC, it adds a potential 15% improvement in global energy use with respect to the usually proposed BS hysteresis control. Moreover, from the simulation results it can be concluded that the thermal comfort is also improved. The proposed BS scheme increases the energy use ratio between the thermally activated building system (TABS) and air-handling unit (AHU); therefore increasing the use of TABS and allowing economic savings, due to the use of more cost-effective thermal equipment.This work was supported in part by the University of the Basque Country (UPV/EHU) through Project GIU14/07 and by the Basque Government through Project IT987-16, as well as by the MINECO through the Research Project DPI2015-70075-R (MINECO/FEDER). The work of Bram van der Heijde is funded by the European Union, the European Regional Development Fund ERDF, Flanders Innovation & Entrepreneurship and the Province of Limburg (Belgium) through the project EFRO Project 936 "Towards a Sustainable Energy Supply in Cities". The authors also want to recognize Maarten Sourbron, Damien Picard and Stefan Antonov from The SySis of KU Leuven for their support in the investigation

Mass, energy, entropy and exergy rate balance in a ranque-hilsh vortex tube

<p>The purpose of this paper is to exhibit a laboratory practicum designed for the subject of Thermodynamics at the Department of Thermal Engineering of the University of the Basque Country. With reference to one of the problems stated in the text of Moran, Shapiro, Boettner, Bailey (2012), the balances of mass, energy, entropy and exergy are applied in a particular Control Volume, and the ideal gas model is used.</p> <p>Using a Ranque-Hilsh vortex tube (Ranque, 1934), the division of a compressed air flow into two streams at a lower pressure is achieved; one hot  whose temperature can exceed 100 °C and another cold that can reach temperatures below -40 °C. Therefore an air flow is divided into two, one hot and one cold stream, without any thermal interaction with hot or cold focuses.</p> <p>The vortex tube operation can serve to expose the bases of the first and second law of thermodynamics. Even, this practical lab can be used to give sense to one of the most known theoretical experiments in thermodynamics, such as the one of Maxwell's demon (Lewins &amp; Bejan, 1999; Liew, Zeegers, Kuerten &amp; Michalek, 2012). On the other hand once a compressed air source is provided, the material needed to prepare the lab is simple and affordable and it has a very interesting and suggestive appeal.</p