cresesb.cepel.br/sundata>. Accessed Aug. 25, 2014. [6] METEONORM Software. Available at: . Accessed Aug. 25, 2014. [7] H. Gallo ...
APPLYING PHOTOVOLTAIC SOLAR ENERGY IN HISTORIC BUILDINGS: A METHODOLOGICAL APPROACH Filomena M. V. Longo1, Luis C. M. Blasques2, André C. Nascimento2, Andreza C. S. Martins1, Marco V. A. Vinagre1, Francisco R. R. França1 1 Exact Sciences and Technological Center (CCET), Amazonia University (UNAMA), Pará, Brazil Av. Alcindo Cacela, 287 – Umarizal, Zip Code 66.060-902, Belém, Pará, Brazil. Phone: +55-91-8269-6222 2 Group of Strategic Studies on Electrical Energy (G4E), Federal Institute of Pará (IFPA), Brazil Av. Almirante Barroso, 1155 – Marco, Zip Code 66.093-020, Belém, Pará, Brazil. Phone: +55-91-8815-1521
ABSTRACT: This work presents a methodology with architectural and engineering technical guidelines for the integration of solar photovoltaic (PV) energy in historic buildings protected by the public laws. Brazil has many urban sites in cities founded during the colonial periods of sixteenth and seventeenth centuries, with strong European influences. At that time, most of these cities were under domain of Portugal and Spain and some of them, for short periods, were under domain of the Netherlands. Some of these cities are currently UNESCO world heritage sites, like São Luiz city. The universe of the present research comprises historic buildings of Belém city, located at Pará State, on Brazilian northern region and on the heart of the Amazon Region. The roof plane is adopted as the PV modules installation plane since the façade integration tends to damage the building’s cultural value. The proposed methodology aims to evaluate the impact of the PV integration in historic buildings, in terms of architecture and energy performance, in order to minimize the commitment of the cultural characteristics of the historic and protected buildings and to maximize the PV electricity generation. Keywords: Building Integrated PV (BIPV), Solar Architecture, Historical Buildings, Roofing Systems, Energy Performance.
1
INTRODUCTION
The concern with the economy and conservation of energy is influencing the field of intervention in protected historic buildings. This concern is due to the constant increase in the power demand required for their preservation and conservation and for the urban areas where they are in. Another important factor is the use to which the historic building is intended, and this is a basic requirement for their preservation. In particular, with changes in use or with the need to increase the comfort level, interventions are needed in historic buildings, protected or not by the public laws. If these interventions affect the constructive system and/or the building’s appearance, the measure shall present concepts of reversibility. The experience shows, however, that any intervention causes impacts in the building, so different specialists shall work together in the planning and development of an interdisciplinary effort, since the beginning of the work [1]. In this context the architects, mainly the restorers, are encouraged to think about the problem of the electricity consumption and how to insert new technologies of electricity generation, based on renewable sources such as the solar photovoltaic (PV), in this category of building. However, besides the high potential presented by the PV source and the good results presented by several researches made in the area in the past decade, it is a great challenge specifically for the restorers and project developers to integrate or adapt PV modules into protected historic buildings [2]. In Brazil, the electricity costs are constantly increasing, and this is another problem that the project developers have to face. The integration of a PV system into a historic building, if done to minimize the architectural impact and maximize the energy performance, may be an interesting option to add value to the building and to reduce its operational costs.
2 SOLAR POTENTIAL AMAZON REGION
IN
THE
BRAZILIAN
The Amazon Region biome covers a total area of almost 6.3 million km2, reaching 9 different South America countries. 4.1 million km2, the major part of the Amazon total area, lies within Brazilian territory, reaching 9 Brazilian states [3]. Two of these states, Amazonas and Pará, holds almost all the natural wealth of this biome, including the solar potential that annually reaches the Amazon Region. The Brazilian Solar Energy Atlas estimates this potential as 4 to 6 kWh/m2.day, or 4 to 6 daily sunshine hours [4]. Considering the Pará State, more specifically its main city, Belém, where the present study is being developed, different sources consider the city as the one which holds the best solar potential of the major cities of the Brazilian Amazon Region. The SUNDATA application [5], a national tool, indicates an annual total radiation of 1,847 kWh/m2 on a surface ideally oriented and tilted, with azimuth () of 180° (north oriented) and inclination () of 3°, resulting on a daily mean of 5.06 kWh/m2. The Meteonorm software [6], a global meteorological database widely used by PV specialists, indicates similar values, with annual total radiation of 1,851 kWh/m2 and daily mean of 5.07 kWh/m2, considering = 180° (north oriented) and = 6°, ideal values according to the software. It is important to highlight two particular characteristics of the Belém city climate that affects the PV system’s installation and performance. The first one is the low monthly variability of the solar resource. The best month considered by the Meteonorm, August, with the same orientation and tilt angles mentioned above, presents a daily mean of 6.19 kWh/m2, only 18 % higher than the annual daily mean and 34 % higher than the daily mean of the worst month, February, with 4.07 kWh/m2. Another characteristic, common to all low latitude cities, is the indication of low tilt angles for the installation of PV modules, as can be seen from the
angles indicated for ideal installations (3o by SUNDATA and 6o by Meteonorm). Façade installations therefore present a considerable loss of system’s performance. On the other hand, even though the north orientation is pointed as the ideal, the very low latitude (1.456o South) of Belém indicates that a south oriented surface presents almost negligible loss of performance compared to north oriented surfaces. To illustrate this characteristic, very important for the methodology proposed in this paper, Fig. 1 presents the system’s performance compared to an ideal installation (100 % for = 180° and = 6°).
that it provides, especially for the tourism sector. In the past three decades, the historic buildings protected by the public laws of Belém, main city of the Pará state, located in the Brazilian northern region, went through interventions to become reference and attraction centers for locals and tourists. The origin of Belém city dates back to the year 1616 and its urban setting began with the formation of two original bases represented by the districts called “Cidade Velha” and “Campina”. These two districts, with their air photo and map shown in Fig. 2, constitute the historic site of the city, where there are expressive concentration of architectural, urban and landscape assets. This area is protected by public laws and its urban mesh is composed by 146 blocks, with slender lots and historic buildings erected on the alignment of the lot without side clearances, narrow streets and regular topography [9]. The architecture varies from early examples of simple form, with predominance of single-story houses and townhouses and the constant presence of churchyards in front of the religious buildings and palaces. The buildings inserted into narrow lots without setbacks are still characterized by the presence of roofs with ceramic tiles of the “Colmar” type.
Figure 1: PV system performance for Belém city, according to different orientation and tilt angles
3 SOME CONSIDERATION ABOUT HISTORIC AND PROTECTED BUILDINGS The protected historic building emerges as a result of the dynamics of life and collective effort, as a basic element to preserve the memory that characterizes a society and in some way brings references from the past to the present. The understanding that all protected historic buildings should be preserved in its entirety is a romantic point of view. Likewise, do not recognize the value of their preservation is an inappropriate thought. The dynamics of life continuously changes the buildings, the cities and the environment, and sometimes the “old” has to be replaced by the “new”. Nowadays those changes, especially in big cities, occur at a pace never seen before [7]. The great dynamics of these changes imposes to the historic buildings and monuments impacts of high proportion. However, these buildings do not have to be stationary in time; otherwise, they would be preserved just as a cultural value, and not as a commodity, which helps to guarantee their existence [8]. Aiming to attend these two aspects, the culture value and the commodity, the methodology proposed in this work demonstrates that PV systems are possible to install in historic buildings and monuments, considering the visual aspect and their constructive characteristics, without violate the restoration and preservation laws and regulations. The main objective in any restoration work of historic buildings is the conservation of the monument’s constructive characteristics, as well as the maintenance of its appearance [1]. 3.1 Historic Buildings in the Brazilian Amazon Region The maintenance of the cultural patrimony of the Brazilian northern region, derived from the Portuguese colonization, is an important social action that presently is turning into an economic action by the multiplier effect
(a)
(b) Figure 2: (a) Air photo and (b) map of the “Cidade Velha” and “Campina” districts, in Belém city
4
PROPOSED METHODOLOGY
The methodological procedure proposed aims to reach all types of historic buildings, protected or not by public laws, and is initially applied in buildings of the Brazilian northern region, especially in Belém city. However, it is important to mention that the initial results of the methodology will be used to adjust it to be applied in historic buildings of any other region of the world. The main question to be analyzed is the protection laws of each country or region, which can modify the methodology in a most considerable way. The methodology is divided into four steps, presented below.
4.1 General Characteristics This first step aims to research and analyze data regarding the architectural characteristics of the historic building and the urban space in which it is inserted. This research identifies the exact location of the building, the typology of the streets surrounding the building, its geographical orientation, its protection scale, the architectural features and the inclination, the construction material and the area of the building’s roof plane. Fig. 3 presents an example of this research for a historic building of Belém.
Figure 3: Sheet with data identification and classification of the building under investigation and its urban surroundings 4.2 Visual Impact This second step analyses the visual impact of the possible integration of the PV modules in the historic buildings. The methodology of this step works with three conditioning factors that are related to the image of the historic building and are important for the installation of the PV systems. These three factors are the readability, the identity and the imageability [10]. The readability factor is associated especially to the visual quality of the building, i.e. to the external observer’s capability to recognize and to organize coherently the building’s envelopment (façades, roofs, windows and others). The imageability factor, figuratively called as visibility, focuses on the physical qualities of the building, relating them to the attributes of the identity and the image structure. By definition, imageability is the building’s feature that make possible to individuals of a society to evoke a strong image of the building. These two factors explained above are analyzed by the methodology through several external views of the building, necessary to investigate the level of the visual impact that the possible PV integration can cause on the readability and on the imageability of the building. The identity is the factor that relates the individual or particular meaning of the historic building and its structural or spatial relation with the city. It is the meaning of the historic building, i.e. its relationship with the city, be it practical, technological, emotional or other, different from the structural relationship. This meaning is not easily influenced by physical manipulation. This requisite is represented in the methodology by the building’s preservation level and is studied in the first step of the methodology, the general characteristics. Based on this initial information, the identification and analysis of the data of this step is related to the evaluation of the roofing plane’s visibility in the urban
space. This stage of the methodology aims to identify the visual impact of the PV modules installation in each roof face of the historic building, classified as: (1) High visual impact, when the roof face is seen by any observer in the urban space; (2) Moderate visual impact, when the roof face is seen by observers inside the building’s area; and (3) Low visual impact, when the roof face can not be seen by walk observers, just in aerial views. This is the first factor of the analysis, called F1, and has the following scores: 0.5 point for high visual impacts; 0.75 point for moderate visual impacts; and 1.0 point for low visual impacts. The hypothetical case study presented in sub-section 4.5 explains the influence of these scores in the result of the analysis. It is important to mention that specifically for Belém city the façade integration of PV modules is not considered, since the authors conclude that this type of integration causes a considerably damage to the building’s image, based on the profile of the historic buildings studied. This explains the fact that the methodology considers only the roofing area of the buildings for the installation of PV modules. The data research for this step is based on different views of the building. To analyze each view some important factors are considered, such as the topography of the urban area where the building is inserted, since this factor influences the relationship between the building’s image and what the observers see from the street planes; and the observer’s possible routes to reach the building under study. The product of this step, the F1 factor, is then defined by the analysis of a sheet containing all the information commented above. Fig. 4 shows one of these sheets, for a specific historic building of Belém city.
Figure 4: Sheet with data required for the analysis of the visual impact of the possible integration of PV modules, based on the observer’s views from the street plane 4.3 Solar Potential Available on Tilted Roof Planes As already mentioned, the façade installations are not considered in this study, since the visual impact originated by the PV module integration could damage the image of the historic buildings. Thus, the PV integration is expected to cover only the rooftops of the buildings. Based on this assumption, this step of the methodology aims to evaluate the solar potential available on each roof face of the building, with different orientation and tilt angles, and compare it with the ideal case on a percentage basis. The two stages of this calculation is the assessment of the ideal solar potential for a given region, based on the azimuth and tilt angles that give the best averages, and the assessment of the
solar potential specifically on the roof face under evaluation. The result of this calculation, called factor 2 (F2), is presented by equation (1), where Href is the annual sunshine hours for the ideal installation and Hi is the real annual sunshine hours verified at the roof face.
F2
Hi H ref
(1)
It is important to mention that the solar potential can be assessed from a historic database (software, atlas or meteorological stations installed far from the building) or be measured at the interest place. For both cases, it can be observed that the presence of any obstacle that blocks the incident radiation shall be considered, and the value of Hi presented above must be corrected considering the shadowing. 4.4 Area Available for the PV System Installation and its Relationship with the Building Electricity Needs This step aims to associate the roof face area available for the PV installation and the building’s electricity needs. The roof face with sufficient area to meet the electricity consumption will get a higher score in this step. The relationship is calculated according the estimated mean annual electricity generation if the whole roof area is covered with PV modules, and the impact of this generation in the building’s mean annual electricity consumption. Equations (2) and (3) illustrate the calculation to determinate the factor 3 (F3), third step of the proposed methodology.
EG Hi A PR P A
F3
EG EC
(2)
Figure 5: Identification and orientation of the 6 roof faces of the hypothetical building. Table I: First group of the methodology’s interest data Face 1 2 3 4 5 6
Orientation North East South West South West
(o) 180 - 90 0 90 0 90
(o) 6 6 45 45 25 25
Area (m2) 185.72 133.22 86.30 58.8 137.50 87.50
Hi (h) 1,851 1,838 1,411 1,565 1,187 1,399
It is important to notice that the values of Hi for the faces 5 and 6 are negatively influenced by the presence of trees in the internal garden of the building, as shown by Fig. 6, which also shows the position of the building related to the street, important to analyze the visual impact of each roof face.
(3)
The terms EG and EC are the estimated PV generation and the building’s electricity consumption, respectively, given in kWh; A is the roof face area available for the PV installation, in m2; PR is the system estimated performance ratio, in a decimal basis; and the term P-A is the average kWp PV power installed per m2 of roof area, which depend basically on the efficiency of the PV technology considered. Crystalline-cell technology presents a higher P-A than thin-film technology. 4.5 Case Studies This section will present 3 different case studies. The first one considers a hypothetical building located at Belém city, which is used as a reference case aiming to present the methodology in detail. The two other cases are studies developed on real historic buildings of Belém city.
Hypothetical case The hypothetical building has 775 m2 of total roof area, distributed along 6 roof faces with different areas, azimuth and tilt angles. Fig. 5 illustrates this building and Table I presents the first group of interest data. The annual sunshine hours (Href) for an ideal installation in Belém, presented in section 3 and obtained from Meteonorm, is 1,851 h.
Figure 6: Layout of the building, representing the influence of the shadowing on two roof faces The building’s annual electricity consumption is 59,000 kWh. The visual impact, the first factor of the analysis, considers the impact that the PV modules causes from the observer point of view, as explained in section 4.2. In this hypothetical case, the observer is someone who is walking on the streets or on the sidewalks near the building. The F1 is thus high on roof faces 1 and 2, which are seen by any observer on the streets; moderate on roof faces 5 and 6, which are seen only by observers inside the building area, in the garden; and low on roof faces 3 and 4, which are seen only by aerial views. Table II presents the main result of the methodology, with the values of the three factors and the final score of each roof face. The final score is obtained by the simple sum of the three factors. The higher the final score, more suitable is the roof face for the PV installation.
Table II: Main result of the methodology Face 1 2 3 4 5 6
EG.year (kWh) 41,229.84 29,383.00 14,612.32 11,042.64 19,585.50 14,689.50
F1 0.5 0.5 1.0 1.0 0.75 0.75
F2 1.0 0.99 0.76 0.85 0.64 0.76
F3 0.70 0.50 0.25 0.19 0.33 0.25
roofing area, opposite conditions presented by the worst classified roof faces. Score 2.198 1.991 2.010 2.033 1.723 1.755
The results presented in Table II indicate roof face 1 as the more suitable for the PV installation, followed by faces 4, 3, 2, 6 and 5. The values of F3 factor indicate that a PV system covering the best three faces are sufficient to meet the entire electricity consumption of the building. The results indicate that even roof faces 3 and 4 being the ones with low visual impacts, which is the most impactful factor of the analysis, roof face 1 is indicated as the more suitable because presents ideals azimuth and tilt angles and has a big roofing area. Faces 5 and 6 are the less suitable because of the shadowing, even presenting moderate visual impact.
“Antonio Lemos Palace” Case Fig. 7 illustrates the Antonio Lemos Palace building, which has 19 different roof faces with a total roofing area of 3,034 m2. Its annual electricity consumption is 316,422 kWh, Href is equal to 1,851 h, since it is located in Belém city, the roof faces present low tilt angles, ranging between 20 and 28o, and there are no obstacles that shade any roofing area of the building. Based on this data, Table III presents the results of the analysis.
Figure 7: Identification and orientation of the 19 roof faces of Antonio Lemos Palace building Table III indicates roof faces 4, 7 and 2 as the ones with better results, with negligible differences between them, followed by roof faces 6, 17, 13, 8 and 5. This eight roof faces are sufficient to receive PV modules to cover the entire building’s electricity consumption. The worst classified are the faces 12, 16, 15, 19, 9 and 10. Unlike the results obtained for the hypothetical building, which presents roof faces with different tilt angles and shadowing conditions, the Antonio Lemos Palace presents roof faces with similar tilt angles and no shadowing, and for this reason the most impactful factor, the visual impact, is decisive for the final scores. The best-classified roof faces have in common the fact that they present moderate visual impact and have good
Table III: Results for Antonio Lemos Palace building Face 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
EG.year (kWh) 59,738.58 45,981.72 87,868.80 40,387.86 39,927.42 40,935.80 40,058.64 41,676.66 1,867.32 1,867.32 59,148.40 7,312.93 30,128.94 38,869.74 7,104.78 7,310.81 30,377.45 39,713.85 7,100.53
F1 0.5 0.75 0.5 0.75 0.75 0.75 0.75 0.75 0.5 0.5 0.5 0.5 0.75 0.5 0.5 0.5 0.75 0.5 0.5
F2 0.92 0.93 0.92 0.96 0.92 0.93 0.96 0.92 0.93 0.93 0.93 0.96 0.96 0.92 0.96 0.96 0.96 0.92 0.96
F3 0.19 0.15 0.28 0.13 0.13 0.13 0.13 0.13 0.01 0.01 0.19 0.02 0.10 0.12 0.02 0.02 0.10 0.13 0.02
Score 1.605 1.829 1.693 1.834 1.792 1.813 1.833 1.797 1.440 1.440 1.621 1.479 1.801 1.539 1.479 1.479 1.802 1.541 1.479
“São José Liberto” Case Fig. 8 illustrates the São José Liberto building, which has a total roofing area of 2,198 m2 and has 32 different roof faces for the analysis. Its annual electricity consumption is 894,494 kWh, Href is equal to 1,851 h, since it is also located in Belém city, the roof faces present low tilt angles, ranging between 13 and 25o, and there are no obstacles that shade any roofing area of the building. Table IV presents the results of the analysis.
Figure 8: Identification and orientation of the 32 roof faces of São José Liberto building Table IV indicates roof face 29 as the one with better results, followed by roof faces 32, 30 and 12. The difference between then is very small. The worst classified are the faces 7, 22, 28 and 20. The conclusions presented for the Antonio Lemos Palace building can also be applied to this case. The only difference is the fact that the building of the present study has a higher electricity consumption, making the F3 factor least significant for the analysis. If the whole roofing area of the São José Liberto building were covered with PV modules, the PV generation would meet only half of the building’s electricity consumption.
Table IV: Results for São José Liberto building Face 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
5
EG.year (kWh) 35,118.22 32,286.04 38,532.95 33,854.61 3,658.05 7,963.11 3,524.92 7,957.63 3,700.18 23,322.75 26,484.16 8,447.00 3,685.05 8,150.00 3,712.15 25,540.76 32,693.76 27,054.22 23,135.86 3,171.28 7,855.87 3,280.43 7,851.24 3,358.13 23,602.32 22,967.28 17,661.60 17,186.40 3,081.12 3,042.48 3,012.24 3,060.96
F1 0.50 0.75 0.50 0.75 0.75 0.75 0.50 1.00 0.50 0.50 0.50 1.00 1.00 1.00 1.00 0.50 0.50 0.50 0.50 0.50 1.00 0.50 0.75 0.75 0.50 0.75 0.50 0.50 1.00 1.00 1.00 1.00
F2 0.96 0.96 0.94 0.96 0.95 0.92 0.92 0.92 0.97 0.99 0.97 0.97 0.96 0.94 0.96 0.97 0.97 0.99 0.97 0.97 0.92 0.95 0.92 0.92 0.96 0.94 0.96 0.94 0.99 0.98 0.97 0.98
F3 0.04 0.04 0.04 0.04 0.00 0.01 0.00 0.01 0.00 0.03 0.03 0.01 0.00 0.01 0.00 0.03 0.04 0.03 0.03 0.00 0.01 0.00 0.01 0.00 0.03 0.03 0.02 0.02 0.00 0.00 0.00 0.00
Score 1.496 1.743 1.481 1.752 1.704 1.675 1.420 1.925 1.476 1.513 1.502 1.981 1.961 1.948 1.968 1.500 1.509 1.517 1.498 1.475 1.925 1.453 1.674 1.669 1.490 1.714 1.484 1.457 1.994 1.982 1.972 1.988
CONCLUSIONS
The dissemination of PV systems is a reality worldwide. In Brazil, this dissemination is not in the same stage of other countries like Germany, Spain or USA; however, the local public and private actors now understand the importance of the PV source for the national electricity matrix, mainly on installations integrated to buildings in developed urban areas. For this reason, some efforts are currently being made to motivate this type of installation. Although, some barriers have to be surpassed to achieve better results in PV integration, especially when applied to already existing buildings. A correct architectonic integration is one of these barriers, maybe the most important for some category of buildings, such as the historic and protected buildings. The complexity of this discussion needs a research effort to enable the PV integration without compromising the image of the building and contributing to meet all or part of its electricity needs. The present paper demonstrates that the PV integration in historic buildings shall be analyzed considering different factors, both architectural and energetic, aiming to meet two specific objectives: minimize the visual impact and maximize the energetic performance. The first one has a greater influence, but the latter can not be considered much less relevant. This subject has not yet reached a final consensus worldwide, even less in Brazil, because the discussion needs to be
conducted by architects and engineers in a very close way. The consolidated methodology can be further applied to contemporary buildings, since the architectonic issues, even still important, are easier to work with.
ACKNOWLEDGEMENTS The authors of this paper would like to thank the support of the R&D Project sponsors, Eletrobras-Eletronorte, company responsible for the electricity generation and transmission on the Brazilian northern region, and ANEEL, the Brazilian Electrical Energy Agency.
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