EAC - Artigos em revistas internacionais
Permanent URI for this collection
Browse
Browsing EAC - Artigos em revistas internacionais by Issue Date
Now showing 1 - 10 of 30
Results Per Page
Sort Options
- Solar XXI building: Proof of concept or a concept to be proved?Publication . Panão, Marta Oliveira; Goncalves, HelderSolar XXI building is a low energy office building where passive and active solar strategies have been applied to reduce the use of energy for heating,cooling and lighting, combining also an extensive photovoltaic façade for electricity production. Solar XXI opened in 2006 and is considered a high efficient building, close to a net zero energy building (NZEB), where the difference between the energy consumed and that produced is 1/10th of the energy consumed by a Portuguese standard new office building. Its design includes many energy efficiency concepts, such as a high insulated envelope,south sun exposure, windows external shading, photovoltaic panels heat recovery,ground-cooling system, daylighting, stack effect and cross ventilation. The solar gains of the windows and the effectiveness of shading devices were evaluated in order to correlate solar radiation, external and indoor air temperatures.It was also verified that amplitude-dampening of ground cooled air ranged between 5 and 8 C, following the trend of the analytical solution for heat diffusion of a cylindrical air/soil heat-exchanger.
- Assessement of the Portuguese building thermal code: Newly revised requirements for cooling energy needs used to prevent the overheating of buildings in the summerPublication . Panão, Marta Oliveira; Camelo, Susana; Goncalves, HelderIn this paper, cooling energy needs are calculated by the steady-state methodology of the Portuguese building thermal code. After the first period of building code implementation, re-evaluation according to EN ISO 13790 is recommended in order to compare results with the dynamic simulation results. From these analyses, a newly revised methodology arises including a few corrections in procedure. This iterative result is sufficiently accurate to calculate the building’s cooling energy needs. Secondly, results show that the required conditions are insufficient to prevent overheating. The use of the gain utilization factor as an overheating risk index is suggested, according to an adaptive comfort protocol, and is integrated in the method used to calculate the maximum value for cooling energy needs. This proposed streamlined method depends on reference values: window-to-floor area ratio, window shading g-value, integrated solar radiation and gain utilization factor, which leads to threshold values significantly below the ones currently used. These revised requirements are more restrictive and, therefore, will act to improve a building’s thermal performance during summer. As a rule of thumb applied for Portuguese climates, the reference gain utilization factor should assume a minimum value of 0.8 for a latitude angle range of 40-41ºN, 0.6 for 38-39ºN and 0.5 for 37ºN.
- Solar Load Ratio and ISO 13790 methodologies: Indirect gains from sunspacesPublication . Panão, Marta Oliveira; Camelo, Susana; Goncalves, HelderThis paper reviews and analyzes the compatibility of the simplified empirical method based on the dimensionless parameter of Solar Load Ratio (SLR) and the monthly procedure of the standard ISO 13790 for indirect gains, specifically for unconditioned zones adjacent to a conditioned zone, but separated from it by a partition wall (sunspaces). The main contribution of the work presented here is the new formulation to account SLR correlations in ISO 13790, obtained for sunspaces, but generalizable for other solar systems with known SLR functions. Simulation models are used to perform a sensitivity analysis of internal gains and heat transfer through solar collector surfaces, both issues that distinguishes ISO 13790 from Load Ratio methods. The analysis shows that internal gains can be added to the heat source term or subtracted to heat transfer term without influencing the utilization factor dependence with the gain-to-loss ratio. On the other hand, the SLR assumption that solar collector surfaces are neutral elements and, therefore, not added to the heat transfer term, results in large inconsistencies between SLR and ISO 13790 methods. The detailed monthly methodology of ISO 13790 fairly reproduces results obtained by simulation. However, predictions from the simplified monthly methodology of ISO 13790 fail in mid season months and coldest months.
- Net Zero Energy Residential Building Case StudiesPublication . Aelenei, Laura Elena; Ayoub, Josef; Aelenei, DanielA number of International Energy Agency (IEA) member countries have adopted a vision of so-called "net zero energy buildings" (NZEBs) as long-term goals of their energy policies. However, what has been missing is a clear definition and international agreement on the mesures of building performence that could inform "zero energy" building policies, programmes and industry adoption worldwide.
- Solar XXI: A Portuguese Office Building towards Net Zero-Energy BuildingPublication . Goncalves, Helder; Aelenei, Laura Elena; Rodrigues, CarlosSolar Building XXI, built in 2006, at LNEG Campus in Lisbon, pretends to be an example of a low energy building using passive systems both for heating and cooling (ground cooling) towards a Net Zero-Energy Building (NZEB). The main façade has a PV system with heat recovery which assists the heating in winter time. In summer a ground cooling system (earth tubes)is used to cool the building, together with night cooling strategies. Net Zero-Energy Buildings Performance has gained more attention since the publication in 2010 of the EPBD recast. Successful implementation of such an ambitious target depends on a great variety of factors. For designers and code writers these include: balancing climate driven-demand for space cooling and heating with climate-driven supply for renewable energy resources. With a literature full of theoretical advice and a building industry rife with myths about the value of technologies,the present paper intends to unveil a sustainable framework for sharing insights into NZEB methodology applied to a Portuguese solar office building, SOLAR XXI, currently underway to reach the Net Zero-Energy Goal. Under the common work which is developed also in SHC Task 40-ECBCS Annex 52, “Towards Net Zero Solar Energy Buildings”, the authors of this paper are currently engaged in studying possible strategies for “upgrading” Solar XXI to NZEB status.
- Passive cooling load ratio methodPublication . Nunes, Ana I. F.; Panão, Marta OliveiraThe method Passive Cooling Load Ratio (PCLR) is an innovative simplified method which calculates the monthly cooling energy needs of a thermal zone where passive cooling systems are installed using the variables: cooling energy load and passive cooling potential. This new method is based on the Solar Load Ratio (SLR) that was previously developed for solar heating systems. Although, PCLR was theoretically developed for any passive cooling system, here it is applied to passive cooling based on ventilation strategies. In addition, this paper presents its application to an office room ventilation using: i) forced cooled air from an earth-to-air heat exchanger (EAHE) and ii) natural induced air by a solar chimney from the EAHE. Correlations were obtained for those systems, using the parameters that describe the local climate, the system type and its dimensions. The numerical model used to obtain the correlation functions when one of the systems is installed, associates previously developed numerical models with 5R1C model of ISO 13790. However, the PCLR method can be used to accurately estimate the cooling energy needs without using complex models for simulation. The error for all systems does not overcomes 5.2%, which is an acceptable variation for a simplifed method.
- Design issues for net zero-energy buildingsPublication . Aelenei, Laura Elena; Aelenei, Daniel; Goncalves, Helder; Lollini, Roberto; Musall, Eike; Scognamiglio, Alessandra; Cubi, Eduard; Noguchi, MassaNet Zero-Energy Buildings (NZEBs) have received increased attention in recent years as a result of constant concerns about energy supply constraints, decreasing energy resources, increasing energy costs and the rising impact of greenhouse gases on world climate. Promoting whole building strategies that employ passive measures together with energy efficient systems and technologies using renewable energy became a European political strategy following the publication of the Energy Performance of Buildings Directive recast in May 2010 by the European Parliament and Council. However designing successful NZEBs represents a challenge because the definitions are somewhat generic while assessment methods and monitoring approaches remain under development and the literature is relatively scarce about the best sets of solutions for different typologies and climates likely to deliver an actual and reliable performance in terms of energy balance (consumed vs generated) on a cost-effective basis. Additionally the lessons learned from existing NZEB examples are relatively scarce. The authors of this paper, who are participants in the IEA SHC Task 40-ECBCS Annex 52, “Towards Net Zero Energy Solar Buildings”, are willing to share insights from on-going research work on some best practice leading NZEB residential buildings. Although there is no standard approach for designing a Net Zero-Energy Building (there are many different possible combinations of passive and efficient active measures, utility equipment and on-site energy generation technologies able to achieve the net-zero energy performance), a close examination of the chosen strategies and the relative performance indicators of the selected case studies reveal that it is possible to achieve zero-energy performance using well known strategies adjusted so as to balance climate drivendemand for space heating/cooling, lighting, ventilation and other energy uses with climate-driven supply from renewable energy resources.
- How low should be the energy required by a nearly Zero-Energy Building? The load/generation energy balance of Mediterranean housingPublication . Panão, Marta Oliveira; Rebelo, Miguel P.; Camelo, SusanaDirective 2010/31/EU adopted that by the end of 2020 all new buildings should be nearly Zero-Energy Buildings (nZEB) and Member States should achieve cost-optimal levels by ensuring minimum energy performance requirements for buildings. This paper discusses how low should be the energy required by a nZEB, in the context of housing energy consumption in a Mediterranean climate (Lisbon). For selected houses built after 1990, the calculated primary energy loads for regulated uses – heating, cooling and domestic hot water – are found to be below 90 kWh/(m2 year). Applying the cost-optimal solutions of thermal insulation and glazing type and considering energy efficiency improved systems, this study concludes that housing energy loads are ‘low’ for the indicative range of 70 kWh/(m2 year) for regulated uses or 100–110 kWh/(m2 year) for total uses, taking primary energy indicators (PEI) from EN 15603. Assuming PEI from Passive House Planning Package or those to be assumed in Portugal for 2013, the threshold decreases to 60 kWh/(m2 year) for regulated uses or 90–100 kWh/(m2 year) for total uses. Only the first nZEB condition is explored by this paper. The second condition requires that the nZEB energy load is covered by a ‘significant’ part of renewable energy sources produced on-site or ‘nearby’.
- Thermal performance of a hybrid BIPV-PCM: modeling, design and experimental investigationPublication . Aelenei, Laura Elena; Pereira, R.; Goncalves, Helder; Athienitis, AndreasIn this paper, a BIPV-PCM installed in an office building façade is investigated to approach the practical application of PV-PCM. Based on an updated mathematical model, theoretical simulation has been conducted for BIPV-PCM in this case. Furthermore, field testing for this case has also been performed to validate the model, and then the simulated and experimental results are compared and found in considerably good agreement. The experiments have been conducted during the winter time, as the prototype has been installed in January 2013. The experimental and numerical results show a good agreement, the maximum electrical efficiency of this BIPV-PCM can reach 10% and the thermal one 12%.
- Revisiting cooling energy requirements of residential buildings in Portugal in light of climate changePublication . Panão, Marta OliveiraSince climate data for building energy simulation have recently been refreshed with 1971–2000 observational data and theoretically influenced by a conservative approach of climate change, benchmarks forcooling energy requirements for residential buildings are discussed for a set of 30 regions in Portugal,mainland and islands, as a contribution to the next revision of Portuguese building thermal code (DL118/2013). The main conclusion is that gain utilization factor correlates with average external air tem-perature for summer season by a logarithmic function. The benchmark for gain utilization factor playsan important role in defining cooling energy requirements. A set of recommendations are suggested:(i) using the gain utilization factor as an index to evaluate the overheating risk, thus, for values abovea defined threshold cooling energy needs could be neglected for primary energy demand quantifica-tion; this measure may encourage designers to integrate passive cooling systems; (ii) defining a nationalroadmap based on technological advances of shading solutions for benchmark parameterization of thewest equivalent collecting area by unit of floor area starting from 0.065.
- «
- 1 (current)
- 2
- 3
- »