‘State-of-the-art’ of building integrated photovoltaic products

During the last decades, the photovoltaic (PV) modules and their associated architectural materials are increasingly being incorporated into the construction of the building envelope such as façade, roof and skylights in the urban centers. This paper analyzes the-state-of-the-art of the PV elements and construction materials which are advertised as BIPV-products at the most important companies in the world. For this purpose 136 companies and 445 PV elements have been investigated and analyzed from a technical and architectural point of view. Also, the study has been divided into two main groups according to industry which producing the product: BIPV-Modules, which comes from the PV modules manufacturers and consist of standard PV-modules with some variations in its aesthetic features, support or dimensions; and PV-Constructions Elements, which consist of conventional constructive elements with architectural features intentionally manufactured for photovoltaic integration. In advance for conclusions, the solar tile is the most common PV-constructions element, the Si-crystalline is the most widely used PV technology, and the BIPV-urban furniture is the fastest growing market experienced in recent years. However, it is clear the absences of innovative elements which meet at the same time both the constructive purpose as the quality standards of PV technology.

Model Based On-Line Energy Prediction System for Semi-Autonomous Mobile Robots

Maximizing energy autonomy is a consistent challenge when deploying mobile robots in ionizing radiation or other hazardous environments. Having a reliable robot system is essential for successful execution of missions and to avoid manual recovery of the robots in environments that are harmful to human beings. For deployment of robots missions at short notice, the ability to know beforehand the energy required for performing the task is essential. This paper presents a on-line method for predicting energy requirements based on the pre-determined power models for a mobile robot. A small mobile robot, Khepera III is used for the experimental study and the results are promising with high prediction accuracy. The applications of the energy prediction models in energy optimization and simulations are also discussed along with examples of significant energy savings.

Aplicación de energía geotérmica de muy baja entalpia para la climatización de un edificio de oficinas en Alcorcón, Madrid

El presente Proyecto tiene como propósito el estudio de la viabilidad de la implantación de energía geotérmica de muy baja entalpia para la climatización de un edificio empresarial en Madrid. Para ello se emplearon cálculos teóricos y simulaciones realizadas mediante programas informaticos especializados con el fin de estimar los parámetros técnicos necesarios para su viabilidad. Se estimo el suministro de la potencia necesaria a través de tres bombas de calor tipo agua-agua que sustituyen a las bombas de calor aire-agua individuales anteriormente instaladas. El intercambio de calor se realiza a través de sondas geotérmicas U-Simple. Se dimensionaron los colectores, bombas de circulación, deposito de inercia y vaso de expansión necesarios para funcionamiento del sistema. El estudio económico determino la necesidad de una alta inversión inicial, con una rentabilidad a medio plazo. Además de los beneficios económicos se realizo un estudio de las emisiones de gases de efecto invernadero demostrando la reducción de los mismos, lo que refleja que además de ser una tecnología económicamente viable es una energía limpia. ABSTRACT The objective of the present project is to evaluate the viability of the imposition of a low-enthalpy geothermal energy system for air conditioning in a business building in Madrid. In this study, both theoretical calculations and numerical simulations in specialized programs were used in order to estimate the technical parameters needed for its viability. We estimated the necessary power supply, which is delivered by three heat water-water pumps that substitute the individual heat air-water pumps previously installed. The heat exchange is achieved through geothermal vertical simple-U probes. Also in this work we have measured the collectors, flow pumps, inertia deposit and the water expansion vessel needed for the proper operation of the system. The economic study determined the need of a high initial investment with mid-term profit. In addition to the economic benefits, the greenhouse gases emissions were evaluated, finding that the geothermal energy system implies a reduction of these emissions. This reflects the fact that, in addition to being economically viable, the geothermal energy is considered a clean energy.

Experiences and methodology in a multidisciplinary energy and architecture competition: Solar Decathlon Europe 2012

Solar Decathlon Europe is an international competition among universities which promotes interdisciplinary learning in engineering and architecture. Students from different disciplines participate in teams guided by several professors during a 29 month preparation period plus five weeks of on-site contest. The educational project involves designing, building and testing a solar energy house connected to the electrical grid with the strategy of maximizing self-consumption, supported by bioclimatic technologies and maintaining a low environmental footprint. It culminates in a on-site contest in which teams must assembly the house themselves, test it with ordinary real life tasks and finally disassembly it. The event has also a divulgative aim, trying to make students and visitors get interested in discovering the problems presented by real engineering and architecture applications. In addition, SDE covers R&D aspects in different fields such as energy efficiency, solar energy and bioclimatic architecture. This article presents the methodology followed during the SDE 2012 edition, in which more than 850 students participated. The obtained results show that the educational competition was a success according to the technical and professional ambitions of the students, most of them considering that their knowledge had increased in areas related to technical and multidisciplinary aspects.

Experimental analysis of energy savings and hygrothermal conditions improvement by means of air curtaines in stores with intensive pedestrian traffic

Current worldwide building legislation requirements aim to the design and construction of technical services that reduce energy consumption and improve indoor hygrothermal conditions. The retail sector in Spain, with a lot of outdated technical systems, demands energy conservation measures in order to reduce the increasingly electrical consumption for cooling. Climatic separation with modern air curtains and advanced hygrothermal control systems enables energy savings and can keep suitable indoor air temperature and humidity of stores with intense pedestrian traffic, especially when located in hot humid climates. As stated in the article, the energy savings in commercial buildings with these systems exceeds 30%

Fuel poverty as a determinant in energy retrofitting actions

Fuel poverty can be defined as “the inability to afford adequate warmth in the home" and it is the result of the combination of three items: low household income, housing lack of energy efficiency and high energy bills. Although it affects a growing number of households within the European Union only some countries have an official definition for it. In 2013, the European Parliament claimed the Commission and Estate Members to develop different policies in order to fight household energy vulnerability. The importance of tackling fuel poverty is based on the critical consequences it has for human health living below certain temperatures. In Spain some advances have been made in this field but main existing studies remain at the statistical level and do not deepen the understanding of the problem from the perspective of dwelling indoor habitability conditions. What is more, this concept is yet to be officially defined. This paper presents the evaluation of fuel poverty in a building block of social housing located in the centre of Zaragoza and how this issue determined the strategies implemented in the energy retrofitting intervention project. At a first step, fuel poverty was appraised through the exploration of indoor thermal conditions. The adaptive thermal comfort (UNE-EN 15251:2008) method was used to establish the appropriate indoor temperatures and consequently to determine what can be called 'comfort gap'. Results were collated and verified with energy bills collection and a survey work that gathered data from neighbours. All this permitted pointing out those households more in need. Results from the social analysis combined with the evaluation of the building thermal performance determined the intervention. The renovation project was aimed at the implementation of passive strategies that improve households thermal comfort in order to alleviate households fuel poverty situation. This research is part of the project NewSolutions4OldHousing (LIFE10 ENV/ES/439) cofounded by the European Commission under the LIFE+ Programme.

Optical characterisation of semi-transparent PV modules for building integration

A complete characterisation of PV modules for building integration is needed in order to know their influence on the building’s global energy balance. Specifically, certain characteristic parameters should be obtained for each different PV module suitable for building integrated photovoltaics (BIPV), some by direct or indirect measurements at the laboratory, and others by monitoring the element performance mounted in real operating conditions. In the case of transparent building envelopes it is particularly important to perform an optical and thermal characterization of the PV modules that would be integrated in them. This paper addresses the optical characterization of some commercial thin-film PV modules having different degrees of transparency, suitable for building integration in façades. The approach is based on the measurement of the spectral UV/Vis/NIR reflectance and transmittance of the different considered samples, both at normal incidence and as a function of the angle of incidence. With the obtained results, the total and zoned UV, visible and NIR transmission and reflection values are calculated, enabling the correct characterization of the PV modules integrated in façades and the subsequent evaluation of their impact over the electrical, thermal and lighting performance in a building.

Methodology for estimating building integrated photovoltaics electricity production under shadowing conditions and case study

Building integrated photovoltaic (BIPV) systems are a relevant application of photovoltaics. In countries belonging to the International Energy Agency countries, 24% of total installed PV power corresponds to BIPV systems. Electricity losses caused by shadows over the PV generator have a significant impact on the performance of BIPV systems, being the major source of electricity losses. This paper presents a methodology to estimate electricity produced by BIPV systems which incorporates a model for shading losses. The proposed methodology has been validated on a one year study with real data from two similar PV systems placed on the south façade of a building belonging to the Technical University of Madrid. This study has covered all weather conditions: clear, partially overcast and fully overcast sky. Results of this study are shown at different time scales, resulting that the errors committed by the best performing model are below 1% and 3% in annual and daily electricity estimation. The use of models which account for the reduced performance at low irradiance levels also improves the estimation of generated electricity.

Greenfield shopping center development. The integration between environmental features, building design and investment analysis at the decision making stage

The Shopping centre is a long term investment in which Greenfield development decisions are often taken based on risks analysis regarding construction costs, location, competition, market and an expected DCF. Furthermore, integration between the building design, project planning, operational costs and investment analysis is not entirely considered by the investor at the decision making stage. The absence of such information tends to produce certain negative impacts on the future running costs and annual maintenance of the building, especially on energy demand and other occupancy expenses paid by the tenants to the landlord. From the investor´s point of view, this blind spot in strategy development will possibly decrease their profit margin as changes in the occupancy expenses[ ] have a direct outcome on the profit margin. In order to try to reduce some higher operating cost components such as energy use and other utility savings as well as their CO2 emissions, quite a few income properties worldwide have some type of environmental label such as BREEAM and LEED. The drawback identified in this labelling is that usually the investments required to get an ecolabel are high and the investor finds no direct evidence that it increases market value. However there is research on certified commercial properties (especially offices) that shows better performance in terms of occupancy rate and rental cost (Warren-Myers, 2012). Additionally, Sayce (2013) says that the certification only provides a quick reference point i.e. the lack of a certificate does not indicate that a building is not sustainable or efficient. Based on the issues described above, this research compares important components of the development stages such as investments costs, concept/ strategy development as well as the current investor income and property value. The subjects for this analysis are a shopping centre designed with passive cooling/bioclimatic strategies evaluated at the decision making stage, a certified regional shopping centre and a non-certified standard regional shopping centre. Moreover, the proposal intends to provide decision makers with some tools for linking green design features to the investment analysis in order to optimize the decision making process when looking into cost savings and design quality.

Income, energy expenditure and housing in Madrid: retrofitting policy implications

Fuel poverty can be defined as ‘the inability to afford adequate warmth in the home’ and it is the result of the combination of three factors: low household income, lack of energy efficiency and high energy bills. Within this context, the present research is aimed at characterizing, for the first time, the housing stock of fuel-poor households in the Autonomous Region of Madrid. Fuel poverty incidence was established and households were divided into six different groups according to their relative position regarding fuel and monetary poverty. The housing stock of each group is characterized and those households most in need are identified. These results enable energy retrofitting priorities to be established, focusing on the needs of the different household groups and accounting for their housing stock characteristics. This allows Spanish energy retrofitting policies to be assessed for their capability of tackling fuel poverty and makes it possible to suggest some improvements.

Assessment of expected damage on buildings subjected to Lorca earthquake through an energy-based seismic index method and nonlinear dynamic response analyses

The city of Lorca (Spain) was hit on May 11th, 2011, by two consecutive earth-quakes of magnitudes 4.6 and 5.2 Mw, causing casualties and important damage in buildings. Many of the damaged structures were reinforced concrete frames with wide beams. This study quantifies the expected level of damage on this structural type in the case of the Lorca earth-quake by means of a seismic index Iv that compares the energy input by the earthquake with the energy absorption/dissipation capacity of the structure. The prototype frames investigated represent structures designed in two time periods (1994–2002 and 2003–2008), in which the applicable codes were different. The influence of the masonry infill walls and the proneness of the frames to concentrate damage in a given story were further investigated through nonlinear dynamic response analyses. It is found that (1) the seismic index method predicts levels of damage that range from moderate/severe to complete collapse; this prediction is consistent with the observed damage; (2) the presence of masonry infill walls makes the structure very prone to damage concentration and reduces the overall seismic capacity of the building; and (3) a proper hierarchy of strength between beams and columns that guarantees the formation of a strong column-weak beam mechanism (as prescribed by seismic codes), as well as the adoption of counter-measures to avoid the negative interaction between non-structural infill walls and the main frame, would have reduced the level of damage from Iv=1 (collapse) to about Iv=0.5 (moderate/severe damage)

Shake-table tests of a reinforced concrete frame designed following modern codes: seismic performance and damage evaluation

This paper presents shake-table tests conducted on a two-fifths-scale reinforced concrete frame representing a conventional construction design under current building code provisions in the Mediterranean area. The structure was subjected to a sequence of dynamic tests including free vibrations and four seismic simulations in which a historical ground motion record was scaled to levels of increasing intensity until collapse. Each seismic simulation was associated with a different level of seismic hazard, representing very frequent, frequent, rare and very rare earthquakes. The structure remained basically undamaged and within the inter-story drift limits of the "immediate occupancy" performance level for the very frequent and frequent earthquakes. For the rare earthquake, the specimen sustained significant damage with chord rotations of up to 28% of its ultimate capacity and approached the upper bound limit of inter-story drift associated with "life safety". The specimen collapsed at the beginning of the "very rare" seismic simulation. Besides summarizing the experimental program, this paper evaluates the damage quantitatively at the global and local levels in terms of chord rotation and other damage indexes, together with the energy dissipation demands for each level of seismic hazard. Further, the ratios of column-to-beam moment capacity recommended by Eurocode 8 and ACI-318 to guarantee the formation of a strong column-weak beam mechanism are examined.

Building memristor applications: from device model to circuit design

Since the memristor was first built in 2008 at HP Labs, no end of devices and models have been presented. Also, new applications appear frequently. However, the integration of the device at the circuit level is not straightforward, because available models are still immature and/or suppose high computational loads, making their simulation long and cumbersome. This study assists circuit/systems designers in the integration of memristors in their applications, while aiding model developers in the validation of their proposals. We introduce the use of a memristor application framework to support the work of both the model developer and the circuit designer. First, the framework includes a library with the best-known memristor models, being easily extensible with upcoming models. Systematic modifications have been applied to these models to provide better convergence and significant simulations speedups. Second, a quick device simulator allows the study of the response of the models under different scenarios, helping the designer with the stimuli and operation time selection. Third, fine tuning of the device including parameters variations and threshold determination is also supported. Finally, SPICE/Spectre subcircuit generation is provided to ease the integration of the devices in application circuits. The framework provides the designer with total control overconvergence, computational load, and the evolution of system variables, overcoming usual problems in the integration of memristive devices.

A game theory based strategy for reducing energy consumption in cognitive WSN

Wireless sensor networks (WSNs) are one of the most important users of wireless communication technologies in the coming years and some challenges in this area must be addressed for their complete development. Energy consumption and spectrum availability are two of the most severe constraints of WSNs due to their intrinsic nature. The introduction of cognitive capabilities into these networks has arisen to face the issue of spectrum scarcity but could be used to face energy challenges too due to their new range of communication possibilities. In this paper a new strategy based on game theory for cognitive WSNs is discussed. The presented strategy improves energy consumption by taking advantage of the new change-communication-channel capability. Based on game theory, the strategy decides when to change the transmission channel depending on the behavior of the rest of the network nodes. The strategy presented is lightweight but still has higher energy saving rates as compared to noncognitive networks and even to other strategies based on scheduled spectrum sensing. Simulations are presented for several scenarios that demonstrate energy saving rates of around 65% as compared to WSNs without cognitive techniques.

Determination of the influence of specific building regulations in smart buildings

The automation of domestic services began to be implemented in buildings since the late nineteenth century, and today we are used to terms like ‘intelligent buildings’, ‘digital home’ or ‘domotic buildings’. These concepts tell us about constructions which integrate new technologies in order to improve comfort, optimize energy consumption or enhance the security of users. In conjunction, building regulations have been updated to suit the needs of society and to regulate these new facilities in such structures. However, we are not always sure about how far, from the quantitative or qualitative point of view, legislation should regulate certain aspects of the building activity. Consequently, content analysis is adopted in this research to determine the influence of building regulations in the implementation of new technologies in the construction process. This study includes the analysis of different European regulations, the collection and documentation of such guidelines that have been established and a study of the impact that all of these have had in the way we start thinking an architectural project. The achievements of the research could be explained in terms of the regulatory requirements that must be taken into account in order to achieve a successful implementation of a home automation system, and the key finding has been the confirmation of how the design of smart buildings may be promoted through specific regulatory requirements while other factors, such as the global economic situation, do not seem to affect directly the rate of penetration of home automation in construction.