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Power - Photovoltaic - 3.2 kW - Isolated-grid / Canada
Case study assignment
You are a photovoltaic (PV) system designer and you have been contracted by an electric utility operating an isolated grid. The isolated grid is presently powered by diesel gensets, but the utility anticipates that PV will eventually be cost-effective on their grid, due to decreasing PV costs, increasing diesel fuel costs and environmental regulations. In preparation for this eventuality, the utility wishes to install a 3.2 kW building-integrated PV system that will be connected to their isolated grid. The utility needs an analysis of the financial viability of the system. In particular, they wish to know the avoided cost of electricity necessary for a 10% internal rate of return.
Site information
The site is located on Baffin Island in the community of Iqaluit, Nunavut, Canada. Due to the low angle of the sun even in midsummer, and for cost-effectiveness, the system will be mounted vertically on a wall with unobstructed exposure to the sun. The wall faces 30º west of south. The PV array will require only a few tens of meters of wiring to connect with the grid. The grid base load is large enough that the grid will absorb all the energy produced by the PV system. The PV array must be automatically isolated from the grid in the case of grid failure; it must be possible to manually isolate the system for maintenance.
Light levels are very low during the winter; during the summer, the sun will often be at the side of or even behind the array, resulting in low levels of radiation on the array. The low light levels experienced year-round are expected to reduce the average inverter efficiency by 5 to 10% below what would be expected at a more southern location. The low light levels will also decrease the average efficiency of the PV array, even though high-quality monocrystalline PV modules are to be used.
Financial information
Financial figures for the analysis, provided by the utility, are inflation of 2.5%, fuel cost escalation rate of 5.0%, debt ratio of 60%, debt interest rate of 8.5%, discount rate of 9%, and a debt term of 10 years. The array is obtained at about 10% less than the normal commercial price as the manufacturer is interested in the volume purchase and marketing opportunities of the installation. The current retail price of electricity in the community is approximately $0.40/kWh. The utility is a government owned corporation and does not pay income tax. The installation is expected to last for 25 or more years.
The northern location results in high costs for travel and accommodation and makes oversights and delays expensive. Qualified electricians are available, but they will require some technical assistance with the installation.
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
In July, 1995, a 3.2 kW photovoltaic (PV) system was installed on the southern façade of the Nunavut Arctic College, in Iqaluit, Nunavut, Canada. Iqaluit, being off the North American electricity grid, furnished all the electricity for its isolated grid using diesel gensets. The PV system was built to feed electricity onto this grid and reduce diesel fuel consumption. The project had two additional objectives: to publicise PV as a viable power source in the eastern Arctic and to document the long-term performance of grid-tied PV systems in the far north.
The Iqaluit system has been monitored continuously since it started operation, and performance reports have been issued periodically. The system has been very reliable and has required almost no maintenance. Inverter efficiency is low during the winter months, but the average inverter efficiency, weighted by electricity output, has been comparable to systems in the South.
System description
The PV array is mounted on a wall facing 30° west of south. Sixty 50-watt peak PV panels are connected in 5 parallel strings of 12 panels each. Siemens M55 modules make up three strings while the two remaining strings use Solec S-53 modules. Nominal voltage of the 12 series modules is 207 VDC under standard test conditions. A 3 kW Statpower Prosine sine wave inverter with 208 VAC output is tied to the grid. As the system is grid-tied there is no energy storage; the grid is large enough that it can absorb all electrical energy produced by the array.
The overall system efficiency has been relatively low compared with similar systems at more southern locations. The parallel connection of modules from two different manufacturers causes the whole array to operate at a voltage that is not optimal for either type of module. Low irradiance levels, which occur both during winter and during those times in summer when the sun is to the side of or behind the array, reduce efficiency further: the inverter is less efficient at low power levels, and module efficiency is decreased at low light levels.
Lessons learned
On remote grids, even in the far North (or far South), high fuel and maintenance costs for diesel gensets may make photovoltaics cost-effective long before they make sense in more populated areas. The financial viability of PV in grid-tied northern applications hinges on reductions in PV costs, increases in fuel cost and possible environmental regulations. The high reliability, low maintenance requirements, and long life of PV systems are significant advantages on remote grids, where maintenance is expensive and system reliability very important.
Photo
College - Photovoltaic - Isolated-grid, Nunavut, Canada
References
Case study assignment
You are a photovoltaic (PV) system designer and you have been contracted by an electric utility operating an isolated grid. The isolated grid is presently powered by diesel gensets, but the utility anticipates that PV will eventually be cost-effective on their grid, due to decreasing PV costs, increasing diesel fuel costs and environmental regulations. In preparation for this eventuality, the utility wishes to install a 3.2 kW building-integrated PV system that will be connected to their isolated grid. The utility needs an analysis of the financial viability of the system. In particular, they wish to know the avoided cost of electricity necessary for a 10% internal rate of return.
Site information
The site is located on Baffin Island in the community of Iqaluit, Nunavut, Canada. Due to the low angle of the sun even in midsummer, and for cost-effectiveness, the system will be mounted vertically on a wall with unobstructed exposure to the sun. The wall faces 30º west of south. The PV array will require only a few tens of meters of wiring to connect with the grid. The grid base load is large enough that the grid will absorb all the energy produced by the PV system. The PV array must be automatically isolated from the grid in the case of grid failure; it must be possible to manually isolate the system for maintenance.
Light levels are very low during the winter; during the summer, the sun will often be at the side of or even behind the array, resulting in low levels of radiation on the array. The low light levels experienced year-round are expected to reduce the average inverter efficiency by 5 to 10% below what would be expected at a more southern location. The low light levels will also decrease the average efficiency of the PV array, even though high-quality monocrystalline PV modules are to be used.
Financial information
Financial figures for the analysis, provided by the utility, are inflation of 2.5%, fuel cost escalation rate of 5.0%, debt ratio of 60%, debt interest rate of 8.5%, discount rate of 9%, and a debt term of 10 years. The array is obtained at about 10% less than the normal commercial price as the manufacturer is interested in the volume purchase and marketing opportunities of the installation. The current retail price of electricity in the community is approximately $0.40/kWh. The utility is a government owned corporation and does not pay income tax. The installation is expected to last for 25 or more years.
The northern location results in high costs for travel and accommodation and makes oversights and delays expensive. Qualified electricians are available, but they will require some technical assistance with the installation.
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
- The miscellaneous PV array losses of 10% account for the decreased efficiency of the PV modules at low light levels.
- The average inverter efficiency is lower than that typically achieved; this reflects the decrease in inverter efficiency at the low power levels resulting from low light levels.
- Contingencies of 20% have been budgeted for the initial costs to allow for the high cost of oversights and delays at this remote, northern location.
- While an electricity export rate of around $1.54 per kWh results in an internal rate of return of about 10%, the debt service coverage is less than 1: during the first half of the ten year debt period, annual costs exceed annual savings.
Results
In July, 1995, a 3.2 kW photovoltaic (PV) system was installed on the southern façade of the Nunavut Arctic College, in Iqaluit, Nunavut, Canada. Iqaluit, being off the North American electricity grid, furnished all the electricity for its isolated grid using diesel gensets. The PV system was built to feed electricity onto this grid and reduce diesel fuel consumption. The project had two additional objectives: to publicise PV as a viable power source in the eastern Arctic and to document the long-term performance of grid-tied PV systems in the far north.
The Iqaluit system has been monitored continuously since it started operation, and performance reports have been issued periodically. The system has been very reliable and has required almost no maintenance. Inverter efficiency is low during the winter months, but the average inverter efficiency, weighted by electricity output, has been comparable to systems in the South.
System description
The PV array is mounted on a wall facing 30° west of south. Sixty 50-watt peak PV panels are connected in 5 parallel strings of 12 panels each. Siemens M55 modules make up three strings while the two remaining strings use Solec S-53 modules. Nominal voltage of the 12 series modules is 207 VDC under standard test conditions. A 3 kW Statpower Prosine sine wave inverter with 208 VAC output is tied to the grid. As the system is grid-tied there is no energy storage; the grid is large enough that it can absorb all electrical energy produced by the array.
The overall system efficiency has been relatively low compared with similar systems at more southern locations. The parallel connection of modules from two different manufacturers causes the whole array to operate at a voltage that is not optimal for either type of module. Low irradiance levels, which occur both during winter and during those times in summer when the sun is to the side of or behind the array, reduce efficiency further: the inverter is less efficient at low power levels, and module efficiency is decreased at low light levels.
Lessons learned
- Cold, severe northern conditions do not in themselves restrict the use of PV.
- The efficiency of the photovoltaic modules is low under the conditions of weak sunlight prevalent during much of the year in northern applications.
- Inverters with high efficiency over a broad range of outputs improve the output of PV systems in the far North, where low light levels are predominant.
- Inverters intended for systems in the far North should have low quiescent power draw, to reduce power consumption during the long winter nights.
- Accurate prediction of the annual PV system energy output for installations in the far North requires accounting for decreased module and inverter efficiency at low light and power levels, respectively.
On remote grids, even in the far North (or far South), high fuel and maintenance costs for diesel gensets may make photovoltaics cost-effective long before they make sense in more populated areas. The financial viability of PV in grid-tied northern applications hinges on reductions in PV costs, increases in fuel cost and possible environmental regulations. The high reliability, low maintenance requirements, and long life of PV systems are significant advantages on remote grids, where maintenance is expensive and system reliability very important.
Photo
College - Photovoltaic - Isolated-grid, Nunavut, Canada
References
- Lapp, Steve, "Personal communication," SGA Energy, 2000.
- Martel, S., "Personal communication," CANMET Energy Diversification Research Laboratory, 2000.
- Thevenard, D., Dignard, L., Martel, S., Ross, M, Turcotte, D. and Troke, S., "Evaluation of the Monitored Data from a Grid-Connected Photovoltaic System at Nunavut Arctic College, Iqaluit, NWT (Canada)," Proceedings of Renewable Energies in Cold Climates - SESCI 98, Montreal, Canada, 1998.
