Experimental characterisation of an indirect evaporative cooling prototype in two operating modes

Producción CientíficaThe present paper aims to describe the experimental study developed to characterize an indirect evaporative cooling system made of polycarbonate, designed and manufactured by the Thermal Engineering Group of the University of Valladolid; as well as to introduce the main results obtained. The prototype is characterized by a total heat exchange area of 6 m2 and is installed in a heat recovery cycle in the experimental setup constructed in the laboratory. This setup mainly consists of: an AHU that enables the reproduction of the different climatic conditions to be tested; a climatic chamber where comfort conditions are to be achieved; a circuit to supply water during one of the operating modes; and the due ducts and measurement probes to properly connect the whole system and register the evolution of the interesting parameters. Two operating modes are performed. In the first one, exhaust air from the climate chamber, in comfort conditions, goes through one side of the heat exchanger, producing heat transfer from the outdoor air stream through the plastic walls of the system. In the second case, an evaporative cooling mode is implemented by supplying water to the exhaust airstream. Results obtained show that heat transfer through the heat exchanger polycarbonate wall improves in the evaporative cooling mode. Furthermore, both cooling capacity and thermal effectiveness of the system also increase in the second case. Moreover, global heat transfer coefficient and cooling capacity are improved by higher outdoor air volume flow rates. Finally, higher outdoor air temperatures imply better cooling capacities and thermal effectiveness.This work forms part of the research being carried out within the framework of the “Reduction of energy consumption and carbon dioxide emission in buildings combining evaporative cooling, free cooling and energy recovery in all-air systems”, project supported by the Ministry of Science and Technology through the call for scientific research and technological development research projects. Reference number ENE2008-02274/CON. Ana Tejero wants to thank the Consejería de Educación of the Junta de Castilla y León for the support provided through the Regional Strategy of Scientific Research and Technological Development of the European Social Fund

Improved performance of a PV integrated ventilated façade at an existing nZEB

Producción CientíficaVentilated façades are among the existing measures to reduce the energy demand in buildings. The combination of this passive heating and cooling strategy with photovoltaics (PV) can drive new buildings towards the current European targets for near or even net zero-energy buildings (nZEB). The present work aims at studying the PV integrated ventilated façade of the nZEB known as “LUCIA” at the University of Valladolid, Spain. First, the transmissivity of the PV façade is measured. Then, the monitoring of the available solar radiation is presented together with the air-dry bulb temperatures indoors, outdoors and inside the ventilated façade. The experimental results permit the validation of a mathematical model that describes the behaviour of the ventilated façade in its current operating modes. The results show that dampers should be closed during winter to let the façade act as a further insulation for outdoor temperatures below 18.4 C to improve energy efficiency. Indoor air recirculation would be helpful during 10% of the winter period.Junta de Castilla y Leon - Fondo Europeo de Desarrollo Regional (project VA272P18)VIPSKILLS (project 2016-1-PL01-KA203-026152 Erasmus +

Experimental characterisation of the operation and comparative study of two semi-indirect evaporative systems

Producción CientíficaThe study described in this paper aims to present the fundamentals in which the operation of two different evaporative cooling systems is based, as well as the experimental results developed to characterise their behaviour in different conditions of outside air. These results will permit to define, according to the ideas of the systems’ operation, appropriate parameters to characterise the heat and mass exchange processes that take place as well as to compare them, like cooling capacity, thermal or energetic effectiveness; and afterwards developing this comparative analysis. The first system consists of a bank of ceramic pipes arranged vertically and staggered acting as a heat exchanger (SIERCP). In the second case an evaporative cooler has been manufactured with hollow bricks filled with still water (SIECHB). Both systems are called “semi-indirect” because they are designed to act as either direct or indirect evaporative systems depending on the relative humidity of the outdoor and return air streams. Results show that parameters related to the air humidity should be considered; and that the second system behaves generally as a direct evaporative cooler and provides a better performance.Dr. Francisco Javier Rey would like to thank the Consejería de Educación, Dirección General de Universidades e Investigación of Junta de Castilla y León for the support given to the Excellence Research Group GR181 within whose framework is being carried out the project “Design, manufacturing and characterisation of a combined system of high energetic effectiveness climatization: semi-indirect ceramic evaporative cooler, air solar thermal colectors, and heat pump”.Ana Tejero would like to thank the support given by the Consejería de Educación through the Regional Strategy of Scientific Research, Technologic Development and Innovation, supported by the European Social Fund

IAQ improvement by smart ventilation combined with geothermal renewable energy at nZEB

Producción CientíficaThe building sector has the responsibility of being a generator of high carbon emissions, due to inefficient energy consumption in the last decades. For the European Union (EU) and the building sector, this pollution has generated a great impact and concern, establishing objectives in sustainability and energy efficiency in the short term. The EU, committed to energy sustainability, has established several guidelines, aiming at reducing carbon emissions. For this reason, European directives have been published to increase energy efficiency and sustainability in buildings, with EPBD 2018/844/EU being the most up-to-date regulation. This directive mainly focuses on reducing carbon emissions and increasing the efficiency of energy systems in buildings, but it also refers to the importance of establishing indoor air quality indices and smart management of ventilation systems. Before this directive was published, many of the implemented ventilation strategies did not consider the indoor air quality (IAQ) in their scope of established comfort parameters. Therefore, this study analyses the performance of the ventilation system, controlled smartly to cover the demand and the established IAQ rates via CO2 ppm, through renewable geothermal energy systems. This study has been carried out at the LUCIA building, a near Zero Energy Building (nZEB), which belongs to the University of Valladolid, Spain. This building stands out for being one of the most sustainable buildings in the world, according to LEED certification, ranking as the most sustainable building in the northern hemisphere. This building to study is equipped with cutting-edge energy systems, with zero carbon emissions. Several parameters have been analysed (air speed, enthalpy, air flow, temperature, humidity, kWh, climate data, etc.) enabling an energy optimisation of the combined systems. All the monitoring data obtained by the smart management have been analysed, providing favourable outcomes, due to the establishment of IAQ levels, according to the EPBD 2018/844/EU. After this study, the smart management of ventilation combined with removable geothermal energy can be exported as a strategy to reach the established IAQ levels through zero carbon systems.Junta de Castilla y León - FEDER (VA272P18

Energy Management by Dynamic Monitoring of a Building of the University of Valladolid

Producción CientíficaThe continuous increase of energy consumption in buildings enhances the importance of implementing energy management systems within the building facilities. These tools allow us to know precisely both energy consumption and use within the building. Monitoring energy consumption provides a clear view not only of the amount, but also of where and when energy is consumed in the building. Besides, a rear analysis of this information allows us to deduce whether there exists an inappropriate consumption, and thus the possibilities of improving building efficiency. A monitoring tool has been implemented within an academic building at the University of Valladolid, applying technological resources of Information Technology and Communication through dynamic monitoring of electrical and thermal parameters. Results obtained are gathered and analysed to directly contribute to improve the use of energy, reduce costs associated with its generation and use, and improve the thermal comfort of the building occupants. Keywords: Dynamic monitoring, energy performances, energy management, reduction of building consumption

modelling the long-term effect of climate change on a zero energy and carbon dioxide building through energy efficiency and renewables.

Producción CientíficaOver the last few years, studies have predicted an increase in the overall air temperature due to climate change. Today’s society is already sensing this change, which could have a negative impact on the envi- ronment and effort s are being made to seek all possible measures to curb it. One of the consequences of this temperature rise would be its effect on indoor comfort within buildings, which may cause higher energy consumption and operational costs, while reducing the useful lifetime of air-conditioning equip- ment. In this paper, an existing zero energy building (ZEB) is being studied to understand the possible effects of climate change on its zero energy status. The building is also a zero carbon building because all of its generated energies come from renewable sources (biomass, geothermal and solar photovoltaic systems). The building LUCIA has the highest innovative technologies in energy systems, design and con- struction elements and is currently considered as one of the top three buildings with the highest LEED certification in the world. According to current European regulations, buildings will tend to become self- sufficient in terms of energy after 2020, and therefore this study will help us to understand the changes in energy consumption within a long-term timeframe, for such zero-energy buildings. With the aid of the Design Builder version 5 software and its EnergyPlus building energy engine, a building model is simu- lated and energy consumption is analyzed for the years 2020, 2050 and 2080 timeframe. The climatic conditions pertain to the city of Valladolid, Spain, which has a continental climate, while the expected changes in climatic conditions have been produced through the methodology developed by the University of Southampton, called CCworldweathergen. Results have shown that the cooling demand would significantly increase for the years 2050 and 2080, while space heating would drop. This will increase the overall demand for burning more biofu- els to cover the added demand in absorption cooling systems. Moreover, the previously excess generated electricity of the building by photovoltaics would then be totally consumed within the building due to increased demand. This implies that the installed systems will operate for longer hours, which will in- crease maintenance and replacement costs. As a result of this study, it becomes possible to quantify the expected changes in energy consumption and prepare preventive actions to anticipate this change, while improving the management and control of both the energy systems and the building

Experimental study on the cooling capacity of a radiant cooled ceiling system

Nowadays, radiant ceiling systems can be considered among the technologies capable of meeting sustainable heating and cooling requirements. In order to adequately address design and simulation issues concerning these systems, correct evaluation of the heat transfer process is needed. The aim of this research is to present further evidence on the cooling capacity and heat transfer coefficients for a cooled radiant ceiling, assuring adequate thermal comfort levels in those possible different operation conditions. An experimental setup into a climate test room was developed and used to derive convenient results. The obtained values revealed that heat transfer evaluations on the basis of operative temperature as the unique reference temperature and corresponding total coefficient are not appropriate in real situations, but considering radiant and convective phenomena separately is strongly recommended.Manuel Andrés-Chicote wishes to thank the Spanish Government for the support given through a FPU (Formación de Profesorado Universitario) scholarship. Reference: AP2010-2449

9th International Conference on Applied Energy, ICAE2017,

The building sector presents considerable potential to have its energy consumption reduced. An alternative of current great interest is taking profit of the thermal inertia of the same structure of the building, through embedded pipes, for storing thermal energy generated when costs are lower and/or efficiency is higher, named “Thermal Activated Building Systems” (TABS). Energy accumulated is then dissipated when demand raises, seeking to ensure stable indoor comfort conditions while reducing the consumption of conventionally generated energy. The behaviour of these systems is determined by a number of operating parameters to be defined to ensure it operates in an optimal way, taking into consideration criteria such as heat flux dissipated, times of charge and discharge of the structure, position of the active slab, temperature of the fluid use inside the embedded pipes and ambient thermal conditions. It has been demonstrated that the study of the thermal behaviour of sand and gravel active slabs can be extrapolated to concrete, real slabs. This paper presents the experimental results obtained in slabs of 15 and 20 cm thickness, charged until reaching steady state. Then the work discusses the thermal behaviour of the slab for different water temperatures supplied to the pipes. Thus, it illustrates the possible experimental study of active slabs to predict the thermal behaviour of TABS in real applications

Influence of constructive parameters on the performance of two indirect evaporative cooler prototypes

Producción CientíficaTwo equally-sized cross-flow heat exchanger prototypes have been designed with a total heat exchange area of 6 m2 and 3 m2 respectively, constructed with polycarbonate hollow panels of different cross-section. They are connected into a heat recovery cycle within the whole experimental setup constructed for the tests, which mainly consists of: an Air Handling Unit to simulate the outdoor airstream conditions, a conditioned climate chamber, and a water circuit to provide the water supply required. They have been experimentally characterised in two operating modes in order to determine how evaporative cooling improves heat recovery in each case, focusing on the influence of modifying the constructive characteristics. To perform the evaporative cooling process, water is supplied to the exhaust airstream. Results are studied considering how constructive issues, outdoor air volume flow rate and temperature, as well as operating mode influence on the performance obtained. An Analysis of Variance shows how outdoor airflow has a key role in the performance of the systems; whereas entering outdoor air temperature determines cooling capacities. Improvements introduced by larger heat exchange areas compensate with their corresponding smaller cross sections, which hinder water-air distribution on the exhaust air side of the heat exchanger. Finally, these small devices achieve cooling capacities of up to 800 W, being able to partly support ventilation load and achieving around 50% of energy saving in ventilation cooling.This work forms part of the research being carried out within the framework of the “Reduction of energy consumption and carbon dioxide emission in buildings combining evaporative cooling, free cooling and energy recovery in all-air systems”, project supported by the Ministry of Science and Technology through the call for scientific research and technological development research projects. Reference number ENE2008-02274/CON.Manuel Andrés-Chicote wants to thank to the Spanish Government for the support given through the FPU (Formación de Profesorado Universitario). Reference: AP2010-2449

Experimental Study and Analysis of Thermal Comfort in a University Campus Building in Tropical Climate

Producción CientíficaThis study presents the evaluation of the performance and acceptability of thermal comfort by students in the classrooms of a university building with minisplit-type air-conditioning systems, in a tropical climate. To carry out the study, temperature and humidity measurements were recorded, both outside and inside the selected classrooms, while the students were asked to complete thermal surveys on site. The survey model is based on the template proposed by Fanger and it was applied to a total number of 584 students. In each classroom, the Predicted Mean Vote (PMV) and the Predicted Percentage Dissatisfied (PPD) were estimated according to Fanger’s methodology, as well as the Thermal Sensation Vote (TSV) and the Actual Percentage Dissatisfied (APD), which were obtained from the measurements and the surveys. The results of this study showed that the PMV values, although they may vary with the insulation of the clothing, do not affect the TSV. Furthermore, comparing PMV vs. TSV scores, a 2 °C to 3 °C difference in operating temperature was found, whereby the thermal sensitivity for TSV was colder, so it could be assumed that the PMV model overestimates the thermal sensitivity of students in low-temperature conditions. In addition, an acceptability by 90% with thermal preferences between 23 °C and 24 °C were also found. These results indicate that it is possible to increase the temperature set point in minisplit-type air-conditioning system from 4 °C to 7 °C with respect to the currently set temperatures, without affecting the acceptability of the thermal environment to the students in the building