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Cities are experiencing an energy policy transition to minimise and finally zeroing their carbon footprint. A significant part of this carbon footprint originates from energy consumption, and buildings play a vital role in this regard. Therefore, this PhD aimed to determine to what extent the BIPV can contribute to this goal in Europe by investigating the feasibility of building integrated photovoltaic (BIPV) systems as a building envelope material in Europe. Through its huge numbers of building facades and roofs, cities can become the power stations of the future.

The results are promising and show that the technology as an alternative for other building envelope materials has already become economically viable in a major part of Europe. The overall price of the BIPV system is going down annually, and simultaneously, its efficiency is increasing.

Although, more efforts towards a more appropriate and fair procedure are needed when it comes to the regulation and policies and power trading schemes for the owners of buildings with BIPV solutions.

The footprint of the technology on the environment and society is also investigated. It is concluded that the technology could also avoid massive investment on the power grid and transmission line and their expansion because the technology is producing power where it would most likely be used. Moreover, BIPV also addresses the critics of exploited land use for solar power plants or wind farms by being implemented on the building skins.

Unfortunately, it is not possible to set a specific price for BIPV per unit kW or square meter, even for a country, region, or city. The BIPV price depends on many factors like BIPV type, location, technical specification, system size, etc. Therefore, in this PhD project, we tried to set average prices to evaluate the system and, in the end, investigate the impact of the inputs on the output with a sensitivity analysis.

Regarding technical investigations, emerging technologies such as organic solar cells and perovskite solar cells are progressing rapidly in terms of efficiency, performance, and other technical privileges such as spectral response and mechanical flexibility. These aspects will make the available types and models of BIPV in the market increasingly diverse and results in a more comfortable use of technology.

The result from the designed experiment to investigate the reflected radiation from the south facade of a neighbouring building to the north façade is also remarkable. The results illustrate that while the incident solar radiation of the north façades in urban areas like Stavanger is less than 30% of the incident solar radiation of the south façades, with a reflection from the south facade of a neighbouring building with glass and/or white panel materials, the incident solar radiation of the same north facade can increase to 50%. Although the electricity production might not scale up to the same portion when using silicon-based PV panels. This indicates that although some issues such as shading in urban areas would jeopardize the incident solar radiation of facades, a portion of this decline can be recouped by the reflection. From an urban planning point of view, if taken reflection seriously to legislation, it might have an impact on the use of urban spaces and the building of structures there, vegetation etc. Therefore, the planners will have to carefully balance how reflection needs are valued as supposed to need for parks, green spaces, and trees that obstruct reflection.

Other major findings from this doctoral study are briefly presented here:

 In Scandinavian countries and because of higher latitude (lower solar altitude), the geographical potential of façades is

the high reflection of the snow and the increased incident radiation on the facades.

 The average annual radiation potential of BIPV as a building envelope material for the entire skins of building in Europe is more than the average annual radiation potential of BIPV on the east or west façade. Figure 5-1 shows these values for Stavanger.

Figure 5-1 Historical data of annual solar incident radiation potential in Stavanger

 BIPV, for its building envelope role, should be regarded as its alternatives such as glass, stone, brick, wood etc. It means that the cost corresponding to its energy supplying role should be considered for the financial analysis and economic feasibility study.

 By considering the investment on the BIPV related to its power generation role as the initial investment for the financial analysis, the BIPV as a building envelope material on average and in all the capital of European member states plus Norway and Switzerland will reimburse all the investment in its lifetime. Non-optimal solutions or inappropriate technical design can violate this fact.

0 200 400 600 800 1,000

2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 AV

Radiation (kWh/m2)

Year

Annual Solar Potential of different orientations Stavanger-Norway

Roof

South

East

West

North

Building skin

Building skin except north

 BIPV as a building envelope material for the entire skin of buildings in urban areas of Europe can have an incredible contribution towards the energy transition of cities. For example, on average and in Europe, by a building skin to the building net area ratio of 0.78, building skin glazing ratio (which is the ratio of the glazed surface to the total surface of the building skin) of 30% and using BIPV on the entire skin of buildings in 2030, the EU cities could reach the zero-energy target.

Results of this study and theoretical and practical implications can guide end-users, architects and urban planners to decide more conscious about the BIPV systems and steer governments and decision-makers to support the technology by rational subsidies and incentive regulations.