Some aspects of the energy cost linked to the IAQ. Impact of free-cooling and heat recovery in office buildings.

CLIMA 2000 (.1997.BRUSELAS)Increasing air exchange rate to improve IAQ may increase energy consumption, but this increase may be compensated for by strategies such as free cooling and heat recovery. The frame of the proposed paper is the examination of the potential at a regional level (the Iberian peninsula) of the different strategies mentioned above in typical office buildings. Based on a set of reference building morphologies, studies are conducted to evaluate the impact of increasing air ventilation rates for different orientations, quality of the envelope (opaque walls and glazing), operating schedules and indoor set-point temperatures. Then, the impact of the increased air ventilation rates is corrected by introducing the effect of free-cooling, air-to-air heat recovery devices of different types and finally, the combined effect of both energy savings strategies. The research provides Maps allowing: 1. To identify zones when heating or cooling regimes are dominant, in terms of both, peak load conditions and energy requirements. 2. To compare the expected performance of the two energy saving strategies at a certain locality. 3. To compare the potential benefit of applying a given strategy at different localities. 4. To indicate regions of recommendable application of the strategies and the expected energy savings achievable

Natural ventilation: CFD aerodynamic study about passive extractor and windcatcher

La ventilación natural se ha ganado protagonismo en los últimos tiempos como una medida de ahorro de energía para edificios. Los dos principios fundamentales de ventilación natural son el tiro natural por diferencia de temperatura, y la fuerza del viento. El artículo pretende analizar la aerodinámica de los captadores y extractores de viento mediante fluido-mecánica computacional, optimizando las geometrías de estos elementos, y dando como producto del trabajo un modelo simplificado para poder tenerlos en cuenta el cálculo aeráulico de las instalaciones de ventilación y climatización de los edificios. Concretamente, se caracteriza una base de geometrías de captación de viento, y se elabora una guía para el diseño de geometrías de extracción ofreciendo varias de ellas como producto del trabajo realizado.In recent years, natural ventilation has won popularity as an energy saving measure for buildings. There are two fundamental principles of natural ventilation: natural draft by temperature differences, and wind force. The purpose of the article is to analyze the aerodynamics of windcatchers and wind-extractors by means of computational fluid mechanics, optimizing the geometries of these elements, and giving a simplified model as a result of the work, so as to include it in the aeraulic calculation of the buildings’ air conditioning systems. Therefore, a base for wind catching geometries has been characterized, and a guide for the design of extraction geometries has been developed; several of them are offered as a result of the work undertaken

Simplifying the process to perform air temperature and UHI measurements at large scales: Design of a new APP and low-cost Arduino device

The main purpose of Urban Heat Island (UHI) studies and the monitoring of ambient temperatures at large scales is to gather temperature information in a certain area, so as to understand temperature heterogeneity and its drivers or detect locations that lack thermal comfort. However, these studies originate mostly from some research projects, with sufficient budget and manpower to carry out the measurements and the necessary calculations. Thus, there is a scarcity of air temperature information, making it difficult to implement appropriate mitigation actions worldwide. The present work aims to greatly simplify the process to monitor air temperatures and carry out UHI estimations through mobile transects. This is done by introducing the design of a low-cost device and a new APP, which performs automatically most necessary UHI calculations. A web tool based on the Inverse Distance Weighting interpolation method is also included to obtain heat maps. The methodology is illustrated using case studies in Seville (Spain) and New York city (USA). By introducing a straightforward and reproducible methodology, we aim to open the path for a more widespread availability of ambient temperature data anywhere in the world, without the need for costly equipment and many hours of dedication by the researcher

PHDC: sistemas de enfriamiento evaporativo pasivos e híbridos para edificios – software de prediseño

PHDC, es un proyecto internacional, creado con el objetivo de promover el uso de sistemas de refrigeración Pasivos e Híbridos en los edificios entre profesionales de diseño, constructores, propietarios y usuarios. En este artículo, se describen brevemente algunos de los sistemas PHDC. En el marco de este proyecto, el trabajo de investigación realizado produce dos herramientas informáticas para el mejor y máximo aprovechamiento del objetivo del proyecto, las cuales se presentan en este artículo. Las herramientas comentadas son dos: – PHDC AirFlow, en la que se implementa el “método del bucle de presiones” para el cálculo de los caudales de aire que circulan por el interior del edificio. Se analizan los elementos-sistemas-características del edificio, con objeto de integrar un sistema de climatización basado en enfriamiento evaporativo, y se le ofrece al usuario la posibilidad de modificarlos, además se destaca la capacidad de integrar captadores de viento, chimenea solar, sistema de enfriamiento evaporativo basados en medio poroso, micronizadores o pulverizadores. – Y PHDC Energy & Comfort, en la cual se simula el comportamiento térmico del edificio: cargas térmicas, consumos del sistema de refrigeración convencional y ahorro producido al integrar el sistema evaporativo elegido en la herramienta anterior.PHDC is an international project with the objective of promoting use of passive and hybrid cooling systems in buildings between design professionals, builders, owners and users. This article describes some of the systems PHDC analized. Under this project, work of the authors produces two tools for improving and optimization of the objective of project, which are presented in this article. The tools discussed are two: – PHDC AirFlow, which implements the «loop pressure method» for calculating the air flow inside the building. It discusses elements, systems and building characteristics, in order to integrate an air conditioning system based on evaporative cooling, and offers capacity to modify, also user can integrate sensors wind, solar chimney, system based evaporative cooling in porous media, micronisers or sprays. – And PHDC Energy & Comfort, which simulates thermal behavior of building: thermal loads, consumption of conventional cooling system and savings produced by integrating the evaporative system chosen in the previous tool.Unión Europea proyecto de PHDC para la promoción y la diseminación de sistemas de refrigeración pasivos e híbridos downdraught en edificio

Contributions of heat pumps to demand response: A case study of a plus-energy dwelling

- Premio ETSI al mejor artículo científico del Trimestre. Junio 2018. - Artículo subido a idUS con permiso de su primera autora (Laura Romero Rodríguez), que proporciona las versiones preprint y postprint.Demand Response programs are increasingly used in the electricity sector, since they allow consumers to play a significant role for balancing supply and demand by reducing or shifting their electricity consumption. For that purpose, incentives such as time-based rates have been proposed. The present study analyzes the potential benefits of operating the heat pump of a plus-energy dwelling which participates in a dynamic pricing market, benefitting from the thermal storage capacity of the building. The software TRNSYS 17 has been used to model the building and the supply system. A validation of the model was carried out by using available measurements of the dwelling. Three setpoint temperature scenarios have been considered for sixteen different strategies which depend on temperature and electricity price thresholds, with the aim of determining which alternatives could lead to significant savings while maintaining an acceptable thermal comfort. Several factors such as cost savings, heat pump consumption, ratio of self-consumption of the dwelling and use of the heat pump during peak hours were also evaluated in every case. The results show that dynamic price thresholds should be used instead of fixed price thresholds, which may cause low activations of the heat pump or overheat the building above the comfort limits. Cost savings up to 25% may be achieved by using optimal strategies, increasing the self-consumption ratio, having almost no influence on the thermal comfort and achieving significant peak reductions on the grid. The outcomes of this study show the importance of looking at the implications of such strategies on several criteria within a demand response framework.Ministerio de Economía y CompetitividadUniversidad de Sevilla. V Plan Propio de Investigación (VPPI-US)Unión Europea. Horizon2020. Grant agreement No. 69596

Analysis of the economic feasibility and reduction of a building’s energy consumption and emissions when integrating hybrid solar thermal/PV/micro-CHP systems

The aim of this paper is to assess the performance of several designs of hybrid systems composed of solar thermal collectors, photovoltaic panels and natural gas internal combustion engines. The software TRNSYS 17 has been used to perform all the calculations and data processing, as well as an optimisation of the tank volumes through an add-in coupled with the GENOPT® software. The study is carried out by analysing the behaviour of the designed systems and the conventional case in five different locations of Spain with diverse climatic characteristics, evaluating the same building in all cases. Regulators, manufacturers and energy service engineers are the most interested in these results. Two major contributions in this paper are the calculations of primary energy consumption and emissions and the inclusion of a Life Cycle Cost analysis. A table which shows the order of preference regarding those criteria for each considered case study is also included. This was fulfilled in the interest of comparing between the different configurations and climatic zones so as to obtain conclusions on each of them. The study also illustrates a sensibility analysis regarding energy prices. Finally, the exhaustive literature review, the novel electricity consumption profile of the building and the illustration of the influence of the cogeneration engine working hours are also valuable outputs of this paper, developed in order to address the knowledge gap and the ongoing challenges in the field of distributed generation

Mitigating energy poverty: Potential contributions of combining PV and building thermal mass storage in low-income households

The issue of energy poverty has devastating implications for the society, and it has been aggravated in the past years due to the economic crisis and the increase of energy prices. Among the most affected are those with low incomes and living in inefficient buildings. Unfortunately, the bitter reality is that sometimes this part of the population are facing the next question: Heating, or eating? The declining prices of distributed energy technologies such as photovoltaics provides an opportunity for positive social change. Although their use does not address energy poverty directly, substantial contributions may be made. Measurements of indoor temperatures in a social housing district of southern Spain in 2017 have revealed the unbearable temperatures that the occupants have to endure, both in summer and winter. Using this district as a case study, the present work aims to evaluate the benefits of exploiting its rooftop PV potential to cover part of the electricity consumption of the district (reducing the energy bills), and use the surplus electricity to supply power for the heat pumps in the district. Optimal alternatives regarding maximum PV production, maximum self-sufficiency ratio and minimum investment costs have been found, considering as well different options when sharing the available electricity surplus to improve the thermal comfort of the occupants. As far as the authors know, no previous study has followed an approach aimed at energy poverty alleviation such as the one presented in this work. The results show that using the surplus electricity to heat or cool the whole dwellings would improve the thermal comfort of the occupants in average up to 11% in winter and 26% in summer. If all the PV generation was used or more buildings in the area were employed to install PV modules, improvements up to 33% in winter and 67% in summer could be obtained, reducing at the same time the thermal comfort differences among the dwellings of the district

Building thermal storage technology: Compensating renewable energy fluctuations

Emerging technologies and new intelligent management systems will be needed to rise to the energy challenges posed by buildings today. Thermally activated building systems (TABS) are attracting growing interest on the back of their energy savings potential. The TABS studied in this article, a new prefabricated panel designed for installation in residential building façades, was characterised by the high thermal inertia afforded by the phase change materials in its composition. The design and assessment of the potential savings derived from TABS require specific characterisation methodologies to estimate the amount of useful energy available to control the indoor environment. A two-stage approach was adopted for the TABS studied here with ``ideal'' operating control (the building is assumed to be at a constant desired temperature). The first stage involved a simplified method for characterising system behaviour based on performance maps developed from CFD simulations. Such maps can be used to quickly assess changes in system energy performance following on variations in design and operating parameters. In the second, the TABS was integrated into a building with a simplified model to assess monthly energy demand to evaluate the system potential for energy savings in representative types of Spanish single-family housing in different climate zones. The first-stage findings showed that given the system significant inertia, it discharged for several days, even when charging occurred only on the first, ensuring a wide operating range adaptable to renewable resource limitations. The analysis of potential, in turn, revealed that savings of over 40% in heating demand are possible even under the least favourable circumstances.This study was funded by Spanish Ministry of Economy and Competitiveness under the INPHASE (RTC-2015-3583-5) and DACAR (BIA2016-77431-C2-2-R), the European Regional Development Fund (ERDF) and the University of Seville under its Research Plan VI (VPPI-US). Prof. Cabeza would like to thank the Catalan Government for the quality accreditation given to her research group GREiA (2017 SGR 1537). GREiA is certified agent TECNIO in the category of technology developers from the Government of Catalonia. This work is partially supported by ICREA under the ICREA Academia programme