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Power - Photovoltaic - 1,000 kW / Germany
Case study assignment
Your engineering firm has been hired to advise the municipality of Herne in Germany on the financial feasibility of installing a large Building Integrated Photovoltaic (BIPV) system in a proposed new educational centre. The design for this facility has been selected via an international competition and incorporates many innovative architectural and environmental concepts.
Site information
The town of Herne is in the state of Nordrhein-Westfalen in western Germany, some 60 km northeast of Düsseldorf and about 170 km west of Kassel.
The new training centre will pioneer a "micro-climatic envelope" design: an exterior shell of glass and semi-transparent PV modules will enclose some 12,000 m2 of floor area. The enclosed volume will hold the buildings and structures that comprise the centre's lecture halls, meeting rooms, civic hall, library, gymnasium and other facilities. The objective of the glass envelope is to simulate a mild Mediterranean climate in northern Germany. It will shelter, but not completely seal off, the interior space from the outside. Natural airflow and breezes will be maintained via numerous motorized openings in the shell. A sophisticated shading system based on the strategic placement of PV cells in rooftop panels will help keep the interior from overheating. The glass envelope will thus moderate interior temperatures to reduce both the heating and cooling loads of the enclosed buildings while still allowing for the sensation of being in an outdoor environment.
Most of the roof surface will be made up of 925 kWp semi-transparent PV modules. The rooftop modules will be tilted 5º from the horizontal and oriented to the south. Another 75 kWp of PV modules will be installed vertically on the west-facing façade of the structure. A large number of small inverters will feed the solar generated electricity to the loads within the structure and any excess to the grid.
For the greenhouse gas analysis, you can assume that the conventional electricity generation fuel mix that the project will displace is approximately as follows: 31% coal, 7% natural gas, 28% #6 oil, 30% nuclear, and 4% wind and other renewables.
Financial information
Some initial cost estimates have been obtained for the project and show that on average, the selected polycrystalline PV modules will cost about €5,670 per kWp while the total cost of inverters will be approximately €600,000. Installation of all BIPV system components will cost about €860,000. Planning and engineering tasks, including the feasibility analysis and all project development costs, are expected to cost about €560,000. Overall annualized maintenance costs are estimated at about €15,300 per year.
The use of PV modules as roofing material will replace the need for conventional glazing and shading systems that would have otherwise been required for such a design. These avoided costs amount to approximately €2.5 million.
To promote PV installations, the German government guarantees a premium purchase price for PV-generated electricity. The training centre BIPV system will thus receive €0.457/kWh for at least 20 years. Also, since it is a prominent demonstration project, about 50% of the total initial cost of the BIPV system will be subsidized by the state and federal governments. The municipality will provide the balance of the capital and will own and operate the project. It will also receive all income from electricity sales.
You may assume typical financial figures for the analysis: fuel cost escalation of 3%, inflation rate of 2% and a discount rate of 8%. The project life is estimated at 30 years.
Prepare a RETScreen study, documenting any assumptions that you are required to make, and report on the significant conclusions from this analysis.
Solution
The worked-out solution is the data file selected from within the RETScreen Project Database. The user automatically downloads the Project Database file while downloading the RETScreen software.
Teacher's notes
Results
Following some ten years of planning and an international architectural competition, the Mont-Cenis Academy was built between 1997 and 1999 in the town of Herne in the state of Nordrhein-Westfalen, Germany. Located some 60 km northeast of Düsseldorf, the town is in the historic industrial and coal mining heartland of Germany. The educational academy is situated atop the old Mont-Cenis coal mine. With its environmentally and technically groundbreaking design, it is an internationally acclaimed landmark and serves as a symbol of the region's ecological and economic renewal.
Among many other energy and environmental innovations, the most prominent feature of the 12,000 m2 facility is its "micro-climatic envelope", a vast exterior shell of glass and semi-transparent PV modules. This shell encloses a number of buildings and structures that comprise the centre's lecture halls, meeting rooms, civic hall, library, gymnasium and other facilities. While the buildings themselves are heated in the winter, the space inside the glass envelope is not. Large-scale mechanized ventilation controls and the strategic variation of PV cell densities for shading is employed to create a mild Mediterranean micro-climate for the urban environment inside the glass shell.
The PV modules serve a variety of key functions in this design: aesthetically appealing roofing material, shading control that regulates the intake of solar heat and light, and electricity generator. The total capacity of the Building Integrated Photovoltaic (BIPV) system is 1,000 kWp, making it the largest in the world at the time of its construction.
The BIPV system generates some 2.5 times more electricity than is consumed by the facility. Most of the power is thus sold to the central grid. The German Renewable Energy Law (Erneuerbare Energien Gesetz - EEG) promotes grid-connected PV systems by guaranteeing a fixed premium purchase price for PV-generated electricity for 20 years. This significantly improves the cost effectiveness of the Mont-Cenis Academy large BIPV system.
The BIPV system, as well as the overall micro-climatic envelope, has operated well since the project's construction.
System description
Nearly 10,000 m² of the roof's surface is made up of 925 kWp semi-transparent PV modules. Each module is tilted slightly (5º) south. Another 75 kWp of PV is installed vertically on the west-facing façade of the structure. Several different types of multi-crystalline PV cells are used, all of them manufactured by Solarex and ASE. Some 569 individual Sunny Boy 1500 inverters (1,500 W each) are installed in multiple series strings to deliver the solar electricity to the Mont-Cenis buildings and to the grid.
Lessons learned
Worldwide, installed photovoltaic capacity has been increasing by 20 to 30% annually since the mid 1990s. PV systems now supply the equivalent electricity needs of over 1 million homes. Much of this growth has been fueled by European, and particularly German, governments' resolve to establish PV as a significant energy supply option. As a result, module and system costs continue to drop while the efficiency and variety of PV products increases. Building Integrated Photovoltaic systems (BIPV) offer increased application flexibility and cost effectiveness by utilizing PV modules not only for electricity generation but also as a valuable and attractive building material.
Photos
Educational building - Photovoltaic, Westfalen, Germany - Photo 1
Educational building - Photovoltaic, Westfalen, Germany - Photo 2
References
Case study assignment
Your engineering firm has been hired to advise the municipality of Herne in Germany on the financial feasibility of installing a large Building Integrated Photovoltaic (BIPV) system in a proposed new educational centre. The design for this facility has been selected via an international competition and incorporates many innovative architectural and environmental concepts.
Site information
The town of Herne is in the state of Nordrhein-Westfalen in western Germany, some 60 km northeast of Düsseldorf and about 170 km west of Kassel.
The new training centre will pioneer a "micro-climatic envelope" design: an exterior shell of glass and semi-transparent PV modules will enclose some 12,000 m2 of floor area. The enclosed volume will hold the buildings and structures that comprise the centre's lecture halls, meeting rooms, civic hall, library, gymnasium and other facilities. The objective of the glass envelope is to simulate a mild Mediterranean climate in northern Germany. It will shelter, but not completely seal off, the interior space from the outside. Natural airflow and breezes will be maintained via numerous motorized openings in the shell. A sophisticated shading system based on the strategic placement of PV cells in rooftop panels will help keep the interior from overheating. The glass envelope will thus moderate interior temperatures to reduce both the heating and cooling loads of the enclosed buildings while still allowing for the sensation of being in an outdoor environment.
Most of the roof surface will be made up of 925 kWp semi-transparent PV modules. The rooftop modules will be tilted 5º from the horizontal and oriented to the south. Another 75 kWp of PV modules will be installed vertically on the west-facing façade of the structure. A large number of small inverters will feed the solar generated electricity to the loads within the structure and any excess to the grid.
For the greenhouse gas analysis, you can assume that the conventional electricity generation fuel mix that the project will displace is approximately as follows: 31% coal, 7% natural gas, 28% #6 oil, 30% nuclear, and 4% wind and other renewables.
Financial information
Some initial cost estimates have been obtained for the project and show that on average, the selected polycrystalline PV modules will cost about €5,670 per kWp while the total cost of inverters will be approximately €600,000. Installation of all BIPV system components will cost about €860,000. Planning and engineering tasks, including the feasibility analysis and all project development costs, are expected to cost about €560,000. Overall annualized maintenance costs are estimated at about €15,300 per year.
The use of PV modules as roofing material will replace the need for conventional glazing and shading systems that would have otherwise been required for such a design. These avoided costs amount to approximately €2.5 million.
To promote PV installations, the German government guarantees a premium purchase price for PV-generated electricity. The training centre BIPV system will thus receive €0.457/kWh for at least 20 years. Also, since it is a prominent demonstration project, about 50% of the total initial cost of the BIPV system will be subsidized by the state and federal governments. The municipality will provide the balance of the capital and will own and operate the project. It will also receive all income from electricity sales.
You may assume typical financial figures for the analysis: fuel cost escalation of 3%, inflation rate of 2% and a discount rate of 8%. The project life is estimated at 30 years.
Prepare a RETScreen study, documenting any assumptions that you are required to make, and report on the significant conclusions from this analysis.
Solution
The worked-out solution is the data file selected from within the RETScreen Project Database. The user automatically downloads the Project Database file while downloading the RETScreen software.
Teacher's notes
- As a simplifying assumption, the PV system was modeled as if all PV modules were installed 5º from horizontal.
- The RETScreen default value for the efficiency of poly-Si PV modules was used.
- The published projection for the energy output of the actual project (700,000 kWh/yr) is about 16% less than the Renewable energy delivered calculated by RETScreen.
- Transportation costs for the PV modules are assumed to be roughly equal to the transportation costs for conventional roof glazing that would have been incurred if the modules had not been used. These costs cancel each other and are therefore not included in the analysis.
- All periodic costs are assumed to be annualized and expressed as part of the annual O&M costs. While inverter repair or replacement are often the major periodic cost in a PV system, in this case many small inverters are used and it is thus possible to budget for a certain annual failure rate (about 4 to 6 units per year).
- The incentive, or grant, amount was calculated as 50% of total real initial costs (i.e. not including the €2.5 million in materials credits).
Results
Following some ten years of planning and an international architectural competition, the Mont-Cenis Academy was built between 1997 and 1999 in the town of Herne in the state of Nordrhein-Westfalen, Germany. Located some 60 km northeast of Düsseldorf, the town is in the historic industrial and coal mining heartland of Germany. The educational academy is situated atop the old Mont-Cenis coal mine. With its environmentally and technically groundbreaking design, it is an internationally acclaimed landmark and serves as a symbol of the region's ecological and economic renewal.
Among many other energy and environmental innovations, the most prominent feature of the 12,000 m2 facility is its "micro-climatic envelope", a vast exterior shell of glass and semi-transparent PV modules. This shell encloses a number of buildings and structures that comprise the centre's lecture halls, meeting rooms, civic hall, library, gymnasium and other facilities. While the buildings themselves are heated in the winter, the space inside the glass envelope is not. Large-scale mechanized ventilation controls and the strategic variation of PV cell densities for shading is employed to create a mild Mediterranean micro-climate for the urban environment inside the glass shell.
The PV modules serve a variety of key functions in this design: aesthetically appealing roofing material, shading control that regulates the intake of solar heat and light, and electricity generator. The total capacity of the Building Integrated Photovoltaic (BIPV) system is 1,000 kWp, making it the largest in the world at the time of its construction.
The BIPV system generates some 2.5 times more electricity than is consumed by the facility. Most of the power is thus sold to the central grid. The German Renewable Energy Law (Erneuerbare Energien Gesetz - EEG) promotes grid-connected PV systems by guaranteeing a fixed premium purchase price for PV-generated electricity for 20 years. This significantly improves the cost effectiveness of the Mont-Cenis Academy large BIPV system.
The BIPV system, as well as the overall micro-climatic envelope, has operated well since the project's construction.
System description
Nearly 10,000 m² of the roof's surface is made up of 925 kWp semi-transparent PV modules. Each module is tilted slightly (5º) south. Another 75 kWp of PV is installed vertically on the west-facing façade of the structure. Several different types of multi-crystalline PV cells are used, all of them manufactured by Solarex and ASE. Some 569 individual Sunny Boy 1500 inverters (1,500 W each) are installed in multiple series strings to deliver the solar electricity to the Mont-Cenis buildings and to the grid.
Lessons learned
- Photovoltaic cells integrated into a building envelope can serve a variety of functions (e.g. weather skin, shading, daylighting and power generation), thus significantly increasing their value and cost-effectiveness.
- Large PV projects allow for economies of scale and can result in low overall per-kWp costs.
- Unforeseen factors such as higher than expected temperatures below the roof-integrated PV modules and slight shading due to the saw-tooth configuration of the tilted modules may account for some loss of performance from the overall array.
- The use of multiple small inverters allows for easy replacement of defective units and eliminates the large periodic costs associated with the failure of large centralized inverters.
- A large BIPV installation can be a cost-effective and attractive showpiece of environmental sustainability and technological sophistication for a community.
Worldwide, installed photovoltaic capacity has been increasing by 20 to 30% annually since the mid 1990s. PV systems now supply the equivalent electricity needs of over 1 million homes. Much of this growth has been fueled by European, and particularly German, governments' resolve to establish PV as a significant energy supply option. As a result, module and system costs continue to drop while the efficiency and variety of PV products increases. Building Integrated Photovoltaic systems (BIPV) offer increased application flexibility and cost effectiveness by utilizing PV modules not only for electricity generation but also as a valuable and attractive building material.
Photos
Educational building - Photovoltaic, Westfalen, Germany - Photo 1
Educational building - Photovoltaic, Westfalen, Germany - Photo 2
References
- Belotserkovsky, V., "Personal communication," GPCo Inc., 2003.
- IEA Photovoltaic Power Systems Programme, Case Studies Website: http://www.oja-services.nl/iea-pvps/cases/index.htm.
- Krause, "Personal communication," Scheuten Solar Technology GmBH, 2003.
- Lee, E.J., "Personal communication," Korea Institute of Energy Research (KIER) and Korean Solar Energy Society (KSES), 2003.
- Mletzko, L. (Ed.), Impressum: Akademie Mont-Cenis Herne, Susa-Verlag, 1999.
