Browsing by Issue Date, starting with "2008-10-07"
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- Solar XXI building PV systems: performance during the first two yeras of operationPublication . Rodrigues, Carlos; Viana, Susana; Joyce, A; Goncalves, Helder; Silva, António Rocha eThe purpose of this paper is to present the results obtained in the first two years of operation of the grid-connected photovoltaic (PV) systems installed in the named “Solar XXI” building. One PV system, made with multicrystalline silicon modules, has a peak power of 12 kW and was installed on the façade; another system made with amorphous silicon modules has a peak power of 6 kW and was installed in the surrounding park area near the building. From 1st February 2006 until 31 July 2008, the measured daily average, of the building electrical energy consumption, was about 75 kWh and the two PV systems produced in average about 72 % of this energy. The averaged measured Performance Ratio of the systems was about 0.84 for the PV Façade and about 0.76 for the PV in the Park.
- Os edifícios bioclimáticos e a integração das energias renováveis e os sistemas energéticos : Livro de apresentações do seminárioPublication . Goncalves, Helder; Camelo, Susana
- On the sustainable development of solar thermal obligations in buildings in the framework of the Portuguese casePublication . Prates, Manuel João Lopes; Costa, J. Cruz; Mendes, J. Farinha; Carvalho, Maria JoãoThis paper starts remembering the steps given in Portugal to prepare the introduction of a solar thermal obligation. Next, it presents a description of the present legislation related to the Solar Thermal Obligation (STO) and to other incentive measures for growth of the solar thermal market in Portugal. The main problems with implementation of the new regulation are analysed and systematized. Based on the acquired knowledge, further actions are presented to guarantee the success of Solar Thermal Obligation, namely proposals for updating the obligation in conformity with best practice for solar thermal installations and taking into account the new realities upcoming from the actual solar thermal
- Solar climate of Azores: results of monitoring at Faial and Terceira islandsPublication . Aguiar, Ricardo; Silva, António R.; Coelho, RicardoThe North Atlantic archipelago of Azores (Portugal) consists of nine islands, located about 1,500 km from mainland Europe. Currently the Azores has about 243,000 inhabitants, which depend heavily on imported fossil fuel for their energy supply. This is a concern for the regional Government and its Agency for Energy and Environment, ARENA, which naturally support energy efficiency and use of renewable energies. The Azores are rich in several renewable resources, and have even pioneered Portuguese exploitation of wind, wave, and high enthalpy geothermal energy for electricity generation. However, so far solar energy has not been a priority in the renewable energy panorama, probably because the Azores climate has been considered too cloudy. Nevertheless, this is true only in comparison with the Portuguese mainland, as the radiation levels are probably similar or even better than those of Northern Europe. In this context ARENA is developing efforts for increasing the use of solar systems. A collaboration, partly financed by an INTERREG III B Project of the European Community, has been established with INETI, the Portuguese Public Laboratory for the area of Energy, to improve the solar climatology of the Azores. This climatology is indeed quite incomplete. It consists mainly on daily measurements for two sites only at the S. Miguel and Terceira islands. Some sunshine records are available from Campbell-Stokes heliographs. Satellite data exists but their quality is uncertain due to the small size of the islands and the shallow view angle.
- Implementing a new method for the design of bioclimatic buildingPublication . Graça, João Mariz; Bento, João; Goncalves, HelderA tool for support the design of bioclimatic buildings is under development. This tool is also specialy adapted to the particular needs of buildings in the portuguese territory, since it includes the possibility of doing evaluations according to the requirements that are imposed by the new regulations of thermal performance for buildings (RCCTE). This tool will allow designers of bioclimatic architecture to easily extract reports of different energy simulation programs, such as energy Plus, Radiance and RCCTE thermal code. The system is provided with a 3D Editor that shares multiple interfaces with the different simulation programs above mencioned. A particular method for the conception of bioclimatic architecture is assumed, however different types of evaluations can be performed with this interface program. A particular method for the conception of bioclimatic buildings is here sugested. It begans with the evaluation of the complience with the portuguese thermal codes. Once the shape and construction for the building under design are conformant with regulations, other evaluations are sugested. The system provides the possibility of automaticaly generate a geometric definition for future energy plus simulation that maches the previous RCCTE definition, however with some simplification assumptions. This can bring closer the evaluations of the thermal code requirements with the energy Plus evaluations, and so to take advantage of a large number of energy plus features in a detailed analysis. The program under development provides automatic generation of some particular features of Energy Plus that were found very usefull for design tasks of bioclimatic buildings, such as the generation of; adjacent zones, trombe walls zones, earth tubes, detailed window variables, etc.
- Energy simulation of a vernacular raw earth construction, in South Alentejo: a case studyPublication . Graça, João Mariz; Beirão, Teresa; Vinagre, Joel; Macedo, Pedro; Carneiro, Nuno
- Novel solar absorber surfaces with organic pigmentsPublication . Nunes, Clarisse; Brites, Maria João; Mendes, J. Farinha; Prates, Manuel João Lopes; Alexandre, J.; Ferreira, M.; Martins, A. J.; Teixeira, V.; Carneiro, V.; Carvalho, Maria JoãoThis paper presents results of application of natural and synthetic organic pigments in selective solar absorber coatings. Some of these photo excite pigments were tested like solar radiation absorber pigments in paint coatings and others as a form to increase the absorption of solar radiation in titanium oxide monolayer selective coatings produced by reactive magnetron sputtering. Morphologic aspects and optical properties are discussed as a function of deposition parameters and of formulation parameters. The main goal is to prepare solar absorber surfaces as a tandem of TiOx thin films, organic pigment using a conductive substrate or of paint with organic and/or inorganic pigments and conductive substrate, all reaching great photo thermal conversion efficiency, high durability and low costs to the ending product and stability at medium range temperatures (120-150ºC). The best optical properties for titanium oxide sputtered films were 88% for solar absorption, with 7% of emissivity for deposition parameters of: pulsed frequency 200kHz, reverse time of 0.4μs, discharge current of 0.7A, argon flow rate of 50ml/min and oxygen flow rate changing from 0 to 2.5ml/min. The results obtained with paints were not satisfactory. The best couple values for solar absorption and emissivity were respectively 94%, and 74%
- Solar thermal collector yield: experimental validation of calculations based on steady-state and quasi-dynamic test methodologiesPublication . Horta, Pedro; Carvalho, Maria João; Fischer, S.The characterization of collector efficiency is the fundamental tool for long term calculation of collector yield. It is, thus, one of the most important inputs in software tools aiming the design of solar thermal systems. Presently two test methodologies are available for characterization of the efficiency of glazed collectors: i) steady state test and ii) quasi-dynamic test, methodologies based in different model approaches to a solar collector, providing different collector efficiency curve parameters and, consequently, imposing different power calculation algorithms. Moreover, Horta et al (2008) demonstrated that the use of the collector efficiency curve derived from steady state test method is not enough for a thorough characterization of the long term performance of a collector. The present work takes into account the introduction of the above referred test methodologies in the European Test Standard for Solar Thermal Collectors, and aims at clarifying how each test results should be used in long term thermal performance calculations. The paper presents a synthesis of the different efficiency parameters provided by each test methodology and corresponding algorithms, applicable in the calculation of delivered power. Application of these algorithms to two days of measured data allows for a comparison of the results obtained with these different methodologies. For validation purposes, results of tests performed on a CPC type collector with a concentration ratio C=1.72 are used. Measurement sequences are used to validate the calculation of power delivered by the collector using both algorithms based on steady-state methodology (with and without correction) and quasi-dynamic methodology.
- Thermal performance of a passive solar office building in PortugalPublication . Goncalves, Helder; Silva, António Rocha e; Rodrigues, CarlosThis paper presents the thermal performance of a Passive Solar Office Building in Portugal in winter and summer 2006 and 2007. This Building, called Solar XXI, pretends to be an example of passive design both for heating and cooling. It contains a direct gain system assisted by a solar thermal system for winter conditions. In summer a ground cooling system (buried pipes) is used to cool the building, together with night cooling strategies. It also integrate in the vertical south envelope a Photovoltaic System (12 kWp) which provide around 12 MWh per year plus a 6kWp in the car parking, which correspond to around 76% of the electric energy consumption of the building. The integration of the PV system, in the building was done in such a way, that it is possible to recovery the heat production from the PV in order to be used for heating purposes
- Thermal performance of residential buildings in Lisbon with large glazing areasPublication . Tavares, Márcia; Goncalves, Helder; Bastos, JorgeThis work presents the results of an experimental study of residential buildings (multi-family apartments) with glazing areas greater than 75% of the total façade area, and for different solar exposures in Lisbon. These buildings were designed after the implementation of the first Portuguese Buildings Thermal Regulation and they are intrinsically related with the construction and architecture practiced in the last few years. The analysis includes the thermal behaviour of the apartments selected for the study during the summer (2007) and winter (2007-2008). During the monitoring process important data were obtained to assist in the understanding of the thermal performance of the observed units. The main thermal exchanges in a building generally take place through the transparent elements and these can be considered an element of great flexibility and adaptation to climatic variations. The mean of the interior temperature means in the different monitored compartments during the hot season was approximately 27ºC (some cases close to 29ºC), while in the cold season 21ºC (some cases close to 18ºC).