SOLAR ROOF - Roof potential investigation for installing PV system

Abstract

By increasing the amount of CO2 emissions to the atmosphere because of using fossil fuel and the limitation of non-renewable energy sources, solar photovoltaics technology has been growing steadily and is thought to play an important role in the realm of future energies.
The objective of this thesis is to investigate the potential of the rooftops for installing PV system on a small scale of 30 multifamily houses in Gothenburg divided into four categories of age, location, roof type, and ventilation system.
The results of this study are based on simulations from PV*SOL software. The solar potential in this study were investigated by two designing approaches: first, applying the PV modules on the total available area on the roof and considering the total electricity demand in the building, the second approach was to design a PV system for each building for the best roof area by taking into account all possible shading on the roof and the roof direction. Furthermore, the electricity demand was considered only for the building's common electricity. A deep-in analysis for shading effects was performed in this study to determine the importance of shading on the PV systems output.
The investment payback time of each system was investigated for both current and predicted electricity price by performing Life Cycle Cost (LCC) analysis. Additionally, Life Cycle Assessment (LCA) of the PV system was investigated in terms of two aspects: environmental impact and energy payback time.
The result of this study indicated that the profitability of the systems is directly depended on the amount of electricity demand in the buildings. The ventilation type of the building for designing a PV system on the rooftop had a significant role in the system output and profitability. The buildings with FTX ventilation system which demanded the highest amount of electricity had the shortest investment payback time. The most significant effect of the building’s location was on shading analysis results. However, the output of the system did not show any difference between the tilted or the flat roofs. By designing the systems based on the second approach the average size of the PV systems decreased by 40 %, while the demand for buying electricity from the grid for both common and household electricity increased only by 10 %. The output of the designed system indicated that designing PV system for household electricity demand was not profitable. The average investment payback time for current and predicted electricity price was calculated as 28 and 22 years, respectively and the average energy payback time was determined as 1.5 years.

Popular Abstract

The shortage of non-renewable energy sources poses a threat to the human species, the next generation in particular. This prerequisite, combined with the effects of increasing CO2 emissions due to the continued use of fossil fuels, has motivated governments, scientists, and activists to seek renewable energy.
Sweden is a country with a progressive investment in efforts and research towards using renewable energy to meet the energy demand. The Swedish government decided to aim for an ambitious goal of relaying on 100 % of renewable energy by 2050. Therefore, many companies and researchers are investigating sustainable and green energy sources. In this regard, the Swedish Research Institute (RISE) is participating in the Efficient Solar Roofs (EST) project to equip rooftops of residential buildings in Sweden with PV panels.
The objective of this report is to investigate the potential of solar energy generation on roofs in a small scale of 30 multi-family houses in Gothenburg. These buildings were selected among 190 buildings, considering their specific features with direct relation to PV panels output. The most effective factors on the PV system output were divided into four groups of the buildings’ age, location, roof type, and ventilation type. In the age category, buildings were divided into young, old, and million program buildings. In the location category buildings were studied as buildings in the city center and buildings in the suburbs of Gothenburg. The difference between flat and tilted roof in solar potential was studied in roof type category, and the last category was based on the different ventilation systems in the buildings.
The buildings and their surroundings were modelled in PV*SOL software. To ensure an accurate result, modelling the details of installation on the roof was essential, as well as the roof tilt and building's dimension and direction. The lack of available 3D-maps was a major limitation in this study. However, every dimension of the buildings was determined with Google Map Pro and the map section in PV*SOL to have the highest possible accuracy.
The maximum solar potential in this study was investigated by applying the PV modules on the total available area of the roof and considering the total electricity demand in the building, i.e., common and households. Furthermore, as the regulation in Sweden implies, the PV system for each building was designed only for building's common electricity by considering the optimum size and output of the system. An in-deep analysis for the effect of shadings was performed to determine the importance of shading on the output of PV systems. Economic feasibility is an important consideration while investing in a PV system in Sweden due to low electricity prices. Therefore, LCC analysis was Performed for each system to calculate the net present value and payback. Finally, the environmental effect of the PV system was investigated in two aspects. The impact of the production of the PV modules on Global warming, Ozone depletion, Terrestrial acidification, Freshwater eutrophication, Marine eutrophication, and Photochemical oxidant formation was investigated “from cradle to the gate.” Furthermore, the energy payback time for the PV panels production was calculated to determine the time in which the energy used for PV panels production is covered by the sustainable energy produced by the PV system.
The result of this study indicated that the profitability of the systems directly depended on the amount of electricity demand in the buildings. The ventilation type of the building for designing a PV system on the rooftop had a significant role in the system output and profitability by affecting the buildings' electricity demand and providing the available area on the roof for installing the PV system. In the buildings with natural ventilation systems, the highest amount of electricity demand was covered by the PV system although almost 70 % of the generated electricity was sent to the grid. While for the buildings with mechanical ventilation with heat exchanger system, 95 % of supplied electricity was directly used in the building although it covered only 12 % of electricity demand. Investigating the output of the designed system indicated that while the average size of the PV systems decreased by 40 %, the demand for buying electricity from the grid for both common and household electricity increased only by 10 %. Finally, the result of performing Life Cycle Cost and Life Cycle Assessment analysis showed the average investment payback time of 28 and 22 years for current and predicted electricity prices, respectively, and the average energy payback time was determined as 1.5 years.

• author: Hosseini, Forough and Salehi, Saba
• supervisor: Dennis Johansson
• organization: Division of Energy and Building Design; Department of Architecture and Built Environment
• course: AEBM01 20201
• year: 2020
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: Solar roof, solar potential, PV system, Ventilation system, Photovoltaics, million-program buildings
• language: English
• id: 9025204
• date added to LUP: 2020-07-20 11:13:21
• date last changed: 2020-07-20 11:13:21