Vertical vegetation systems are an innovative passive method for decreasing the thermal energy demand of buildings while increasing the quality of urban life. The main objective of this work is to ...calculate the effectiveness of vegetation in reducing thermal loads analytically. For this purpose, the thermal energy performance of the modular living wall was compared with a traditional double façade construction system to evaluate the influence of vegetation using Stochastic Differential Equations models.
The research was carried out experimentally using a real-scale PASLINK test cell. The thermal behaviour of a double leaf bare wall and the same double leaf wall converted into a modular living wall were calculated for different summertime and wintertime periods. In both studied cases, the temperature of the exterior surface of the bare wall is taken at the same place regardless of whether or not there is greenery system in the energy balance. With this simplification, the effect of the modular living wall can be identified within the estimated coefficients.
The thermal resistance of the conventional double façade increased 0.74 (m2 K)/W over the non-greened wall, which represents a weighted increase of 49%. Additionally, the experimental results showed that the evapotraspiration processes that take place in the living wall lead to an increase in the combined convection-radiation coefficient, which reduces the overheating of the façade. Moreover, the effective solar absorptivity value of the outermost surface of the bare wall has been reduced an 85% thanks to the living wall, which confirms the high capacity of the living wall to reduce solar heat gains.
•Thermal model characterization of PASLINK test cell.•High energy savings in cooling and small increase in heating.•Modular living wall did not provide any thermal benefits in cold winter.•Modular living wall installation may reduce building surface temperature by up to 10 °C in summertime.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
Green roofs are artificial ecosystems that provide a nature-based solution to environmental problems such as climate change and the urban heat island effect by absorbing solar radiation and helping ...to alleviate urban environmental, economic, and social problems. Green roofs offer many benefits in terms of heat and water conservation as well as in terms of energy costs. This work proposes the design of an extensive and environmentally sustainable green roof for the Faculty of Engineering building in Bilbao. The green roof will be made from the composting of food waste generated in the building’s own canteen. Therefore, the main objective of this study is to calculate the solar efficiency of a sustainable green roof, evaluate its thermal performance, and quantify the impact that its implementation would have on energy consumption and the thermal comfort of its users. The results obtained confirm that an environmentally sustainable green roof has a positive effect on summer energy consumption and that this effect is much greater when there is water on the roof, as shown by the difference in energy savings between the dry (−53.7%) and wet (−84.2%) scenarios. The data show that in winter the differences between a green roof and a non-vegetated roof are not significant. In this case, the estimated energy consumption penalty (0.015 kWh/m2) would be 10% of the summer gain.
Sustainable development is essential for the future of the planet. Using passive elements, like ventilated facades based on insulation and air chambers, or living walls, which are solutions based on ...nature, is a powerful strategy for cities to improve their thermal environment, reduce energy consumption, and mitigate the effects of climate change. This approach allows for the quantification of the influence of passive surfaces on energy fluxes compared to bare surfaces. In addition, it delves into understanding how the incorporation of vegetation on building facades alters surface energy fluxes, involving a combination of physical and biochemical processes. This comprehensive investigation seeks to harness the potential of passive and natural solutions to address the pressing challenges of urban sustainability and climate resilience. This research uses a surface energy balance model to analyze the thermal performance of two facades using experimental data from a PASLINK test cell. This study uses the grey box RC model, which links continuous-time ordinary differential equations with discrete measurement data points. This model provides insight into the complex interplay among factors that influence the thermal behavior of building facades, with the goal of comprehensively understanding how ventilated and green facades affect the dynamics of energy flow compared to conventional facades. The initial thermal resistance of the bare facade was 0.75 (°C m2)/W. The introduction of a ventilated facade significantly increased this thermal resistance to 2.47 (°C m2)/W due to the insulating capacity of the air chamber and its insulating layer (1.70 (°C m2)/W). Regarding the modular living wall, it obtained a thermal resistance value of 1.22 (°C m2)/W (this vegetated facade does not have an insulating layer). In this context, the modular living wall proved to be effective in reducing convective energy by 68% compared with the non-green facade. It is crucial to highlight that evapotranspiration was the primary mechanism for energy dissipation in the green facade. The experiments conclusively show that both the modular living wall and open-ventilated facade significantly reduce solar heat loads compared with non-passive bare wall facades, demonstrating their effectiveness in enhancing thermal performance and minimizing heat absorption.
Sistema berdeak sendotzen ari dira hirietako eskari termikoa murrizteko eta, aldi berean, hiriko bizitzaren kalitatea hobetzeko. Sistema berdeei lotutako onurak hainbat dira: biodibertsitatea ...handitzea, ekaitz-uren kontrola, energia aurreztea, tenperatura erregulatzea eta zarata arintzea. Landaredun sistema bertikalek errendimendu energetikoari egiten dioten ekarpenari buruzko ezagutza lortzeko, landaredun fatxada bati proba metodologikoak egin zaizkio Paslink zelda batean. Helburua landare-fatxada modular baten berokuntza- eta hozte-eskaria ezaugarritzea da. Emaitza nagusia isolamenduaren hobekuntza izan da. Erreferentziako fatxada 0.75 W/(m2 °C) baliotik abiatzen zen, eta 1.22 W/(m2 °C)-ko transmisio termikoko balioetara igaro zen landare-fatxadari esker; horrek esan nahi du isolamendu-ahalmena % 30 handitu zela. Fatxada berdeek energia aurrezteko potentzialtasun handia dutela ondoriozta daiteke.
In recent years, passive solutions for building envelopes have become much more common due to their capacity to decrease the heat flux through the envelope during summer time. Vertical greenery ...systems (VGS) are emerging as an interesting method of decreasing the thermal demand of cities, and also improving the quality of urban life. Open ventilated facades (OVF) have gained popularity due to their capacity to enhance the thermal resistance of the building envelope. As part of a project carried out in a Paslink cell in Vitoria-Gasteiz, an experimental campaign with full-scale VGS and OVF was carried out during the summer season to assess the thermal performance of a modular living wall (MLW) with respect to an OVF. The objective is to demonstrate that a stochastic differential equations (SDE) model can be used to assess the cooling requirements of an MLW and an OVF. An analysis was carried out to evaluate how different characteristics of the main facade affect performance, such as thermal resistance, solar absorption coefficient and convection coefficient. The results of these experiments show that both MLW (46 %) and OVF (67 %) configurations significantly minimize solar heat loads compared to non-passive bare wall (BW) facades, which are the reference configurations.
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•Physics-based model to predict the transient behavior of PHEX is presented.•Flexible design tool to compare different working situations, geometries and fluids.•Same model to simulate condensers and ...evaporators in counter and parallel-flow.•Dynamic model for simulation of counter-flow two-phase PHEX in Matlab/Simulink.•Experimental validation under the four possible casuistries is presented.
In order to improve the energy efficiency and control of heat pump systems, it is necessary to develop dynamic models that accurately simulate their real performance. In addition, these models will help to carry out future works of research, such as new low carbon refrigerant testing.
Physics-based models follow a set of physics laws that characterize the model as the most accurate, versatile and robust to simulate different heat pump systems. Taking into account the fact that the dynamics of the elements that regulate mass flow (compressors and valves) are much faster than the dynamics of the components that regulate heat transfer (heat exchangers), the model complexity usually resides in the latter.
This paper provides a detailed explanation of the physics-based dynamic model in Matlab/Simulink using the finite-control volume approach applied to a refrigerant-to-liquid plate heat exchanger. Dynamic experimental tests were developed to validate the model under four possible situations: condenser and evaporator heat exchangers working in both counter- and parallel-flow. In addition, an approximation of the number of finite control volumes required to reach a good accuracy, while maintaining a reasonable simulation time is presented.
Simulation results show great accuracy when compared to experimental tests. It was proved by calculating the Normalized Residual Error, which is between 1.1 E-04 and 1.0 E-03 in all cases. It was also concluded that using twenty finite control volumes, there is good agreement between the accuracy of the results and the computational time.
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•A physics-based dynamic model is developed to simulate heat pumps behavior.•Plates heat exchanger model works indistinctly for a condenser or an evaporator.•Plates heat exchanger model works ...indistinctly in counter-flow or parallel-flow.•The model is capable to switch the system working mode.•A procedure is developed to simulate the working mode switch.
Residential reversible liquid-to-liquid heat pump systems are effective systems to increase energy efficiency and decrease gas emissions of buildings that can supply both the cooling and heating demand of a building due to the reversible capability.
This document presents an innovative model developed in Matlab/Simulink that simulates the dynamic behavior of liquid-to-liquid heat pump systems. It is based on a physics-based numerical model capable to switch the refrigerant flow direction and the behavior of the PHEX (condenser or evaporator) according to the actual working mode. With this model, an analysis of the transient states during the switch of the operation mode is carried out.
The model was validated with experimental tests for both the heating and the cooling modes separately. For each working mode test, a sudden change in the working conditions of the system was forced to trigger a fast transient state. Then, the validated model was used to carry out a simulation of a switching mode, starting in the cooling mode and finishing in the heating mode.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
8.
Flameless errekuntzak klima aldaketaren aurka Romero-Anton, Naiara; Martin-Eskudero, Koldobika; Del-Portillo-Valdés, Luis Alfonso
EKAIA Euskal Herriko Unibertsitateko Zientzia eta Teknologia Aldizkaria,
04/2021
39
Journal Article
Open access
Gaur egun klima aldaketaren inguruan daukagun egoera hobetzeko, energia kontsumoa murriztu behar da eta teknologia eraginkorrak eta emisiorik gabekoak suspertu behar dira. Nahiz eta energia ...berriztagarrien alde apustu egin, gaur egungo datuen arabera, bai gaur egun zein etorkizunean erregai fosilen kontsumoa energia primarioa izango da. Egoera honen aurrean erregai fosiletan oinarritzen diren teknologiei buruz ikerkuntzak egitea beharrezkoa da, teknologia berderantz bideratzeko. Klima aldaketari aurre egiteko flameless errekuntza garatu da. Flameless errekuntza produktuen aerodinamikan oinarritzen da, eta horiek birzirkulatuz erreaktiboak diluitu egiten dira. Horri esker O2-aren kontzentrazioa murrizten da labeko gar tenperatura murriztuz. NOx gasen emisioak tenperaturarekin erlazionatuta daudenez, labe tenperatura murriztean, NOx emisioak murrizten dira. Gainera, produktuen birzirkulazioaren bitartez erreaktiboak aurreberotzen badira, energia eraginkortasuna hobetzen da. Teknologia berri horrek aplikazio zuzena izan dezake tenperatura altuko labe eta galdaretan; adibidez, potentzia termikoko instalazioetan, findegietan, industria kimikoan, zeramika, beira, zementu eta altzairu lantegietan, NOx emisioak eta energia kontsumoa murriztuz. Flameless teknologia hobeto ulertzeko helburuarekin ikertzaileak Fluido Dinamika Konputazionala (FDK)-ren bitartez esperimentuak eta simulazioak egiten ari dira. FDK programan dauden modeloekin ohiko errekuntzaren ezaugarriak zehaztasunez simula daitezke (bero transferentzia, jariakinen mekanika, erradiazio termikoa, erreakzio kimikoak eta turbulentzia-kimika interakzioa), baina ez flameless errekuntza, erreaktiboen diluzioa kontuan hartzen ez delako. Hori dela eta beste modelo berri batzuk garatu behar dira.
Europar Batasunak (EB) energia merkatu aldakor bati aurre egin behar dio eta, ildo horretan, «Horizon 2020» deritzon programa jarri du indarrean. Bertan, 2020ra arteko epealdia ezarri dute honako ...xede hauek bideratu ahal izateko: (1) kontsumitutako energiaren % 20ak jatorri berriztagarria izan behar du, (2) eraginkortasun energetikoa hobetu behar da energia primarioaren erabilera % 20 murrizteko eta, azkenik, (3) 1990. urteko balioekin alderaturik, berotegi efektuko gasak % 20 murriztu behar dira. Eraginkortasun energetikoa bideratzeko indarrean dauden «Eraginkortasun Energetiko Plana» eta «Eraginkortasun Energetiko Direktiba 2012/27/EU» definitu dira. Bestetik, aldaketa klimatikoari aurre egiteko eta emisioak murrizteko EBk aplikatutako «cap and trade» mekanismoa eta «2020 klima eta energia paketea» azaldu dira. Dena den, ikerkuntza eta garapen teknologikoak ezinbestekoak dira «Horizon 2020» xedeak betetzeko, beraz, SET-planaren jarduerak ere aztertu dira. Horrez gain, eraginkortasun energetikoak industrian dituen aukerak aztertu dira eta, adibide moduan, SPIREk bultzatutako proiektuak deskribatu dira. Azkenik, EBk 2030 eta 2050 urteetarako proposatutako helburuak eta ikerkuntza lerroak aztertu dira.
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