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Heating - Solar water heater - Hotel/Motel / Canada
Case study assignment
A supplier of glazed collectors for solar hot water systems wants to develop the market for its product. One application that the supplier wishes to investigate is the typical motel. You have been hired by the supplier to help determine the viability of a solar water heating system, from the perspective of the motel owner.
Site information
The supplier proposes that you use a specific motel for the study, and has chosen a motel in St. Côme, Quebec, Canada. It is about 100 km north of Montreal, but the climate is closer to that of Quebec City. The motel has 23 units plus an apartment for the motel manager. The rate of occupancy is typical of facilities depending mainly on tourism and seasonal activities: the yearly occupancy rate is only 20%, but reaches 100% during weekends in January and February. As the motel is equipped with a low-temperature hydronic slab-heating system, the owner proposes that any solar energy surplus be diverted to the slab during the heating season. Therefore the service hot water system can be designed on the basis of a 100% occupancy rate from mid-September to mid-May, and excess hot water will be used for heating. Outside of the heating season, the solar water heating system will be used at only 40% of its capacity, due to the low occupancy rate.
The existing service water heating system utilises oil (#2) and has a seasonal efficiency of 73%. The motel's roof faces due south at a slope of 30º to the horizontal. A maximum of 30 m² of collectors can be installed on the roof. The mechanical room is located 2 floors below the proposed collector site. The horizontal distance from the mechanical room to the proposed solar collector location is 5 m. The desired hot water temperature is 55 °C.
The design and installation should be simple, so that residential system components can be used, thus avoiding the cost of industrial piping, custom design structures, and specialised plumbers.
Financial information
The client provides typical financial parameters for the analysis (income tax rate of 43.6%, inflation of 2.5%, fuel cost escalation rate of 3.5%, debt ratio of 80%, debt interest rate of 8%, discount rate of 9% and a debt term of 20 years). The solar water heating system would last 25 years. This installation would be eligible for an incentive of 25% from the federal government. The system would qualify for an accelerated depreciation rate of 30%, calculated on a declining balance basis.
The price of heating oil is $0.36/L and the retail price of electricity is $0.04/kWh.
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
Real project
Results
In 1998, a solar water heating (SWH) system was installed on a motel located in St. Côme, Quebec, Canada, about 100 km north of Montreal. The project was partially funded by a federal government incentive.
System description
The 30 m² collector consists of 10 Thermodynamics G Type modules, placed at an angle of 45º from the horizontal on the south-facing roof of the motel. It is connected to five 273-litre storage tanks (total storage capacity of about 1,400 litres). Three of these tanks are dedicated to service hot water while the other two are used for slab heating. This configuration was proposed by the installer.
The total cost of the installed system was $20,000.
Lessons learned
The big picture
Solar heating systems for service hot water have high initial costs. With governmental support of about 25% of the initial cost, small Canadian solar service hot water systems will have a payback period comparable to the system life. The market for these systems is therefore limited to consumers ready to pay a premium on energy from renewable sources or to consider their investment based on the entire life-cycle cost of the system.
Photos
Motel - Solar water heater - Solar collector - Glazed, Quebec, Canada
Motel - Solar water heater - Storage tank, Quebec, Canada
References
Case study assignment
A supplier of glazed collectors for solar hot water systems wants to develop the market for its product. One application that the supplier wishes to investigate is the typical motel. You have been hired by the supplier to help determine the viability of a solar water heating system, from the perspective of the motel owner.
Site information
The supplier proposes that you use a specific motel for the study, and has chosen a motel in St. Côme, Quebec, Canada. It is about 100 km north of Montreal, but the climate is closer to that of Quebec City. The motel has 23 units plus an apartment for the motel manager. The rate of occupancy is typical of facilities depending mainly on tourism and seasonal activities: the yearly occupancy rate is only 20%, but reaches 100% during weekends in January and February. As the motel is equipped with a low-temperature hydronic slab-heating system, the owner proposes that any solar energy surplus be diverted to the slab during the heating season. Therefore the service hot water system can be designed on the basis of a 100% occupancy rate from mid-September to mid-May, and excess hot water will be used for heating. Outside of the heating season, the solar water heating system will be used at only 40% of its capacity, due to the low occupancy rate.
The existing service water heating system utilises oil (#2) and has a seasonal efficiency of 73%. The motel's roof faces due south at a slope of 30º to the horizontal. A maximum of 30 m² of collectors can be installed on the roof. The mechanical room is located 2 floors below the proposed collector site. The horizontal distance from the mechanical room to the proposed solar collector location is 5 m. The desired hot water temperature is 55 °C.
The design and installation should be simple, so that residential system components can be used, thus avoiding the cost of industrial piping, custom design structures, and specialised plumbers.
Financial information
The client provides typical financial parameters for the analysis (income tax rate of 43.6%, inflation of 2.5%, fuel cost escalation rate of 3.5%, debt ratio of 80%, debt interest rate of 8%, discount rate of 9% and a debt term of 20 years). The solar water heating system would last 25 years. This installation would be eligible for an incentive of 25% from the federal government. The system would qualify for an accelerated depreciation rate of 30%, calculated on a declining balance basis.
The price of heating oil is $0.36/L and the retail price of electricity is $0.04/kWh.
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
- During the summer months the low demand will result in high temperatures in the collectors. This will necessitate more frequent replacement of the glycol. For this reason, the glycol replacement interval has been set to 5 years. The annual maintenance consists only of inspection.
- There are no development costs for this small project.
- The storage system appears relatively small compared to the collector, but there is thermal mass in the heated slab that increases the effective storage capacity.
- The losses due to snow and dirt are relatively high (8%) because the system is mainly used during the winter.
- A heat exchanger effectiveness of 70% is typical of a custom side-arm design without secondary pump.
Real project
Results
In 1998, a solar water heating (SWH) system was installed on a motel located in St. Côme, Quebec, Canada, about 100 km north of Montreal. The project was partially funded by a federal government incentive.
System description
The 30 m² collector consists of 10 Thermodynamics G Type modules, placed at an angle of 45º from the horizontal on the south-facing roof of the motel. It is connected to five 273-litre storage tanks (total storage capacity of about 1,400 litres). Three of these tanks are dedicated to service hot water while the other two are used for slab heating. This configuration was proposed by the installer.
The total cost of the installed system was $20,000.
Lessons learned
- In typical Canadian climatic conditions, solar systems that are under-utilised in the summer months will have difficulty competing with conventional hot water systems. Systems specifically intended for active solar space heating (i.e., slab heating) therefore face significant financial obstacles.
- For this application, the 25% federal government incentive was insufficient to make SWH competitive with conventional systems based on financial criteria alone. This reflects the high initial costs, poor match between demand for hot water and solar availability, and competition from cheap conventional energy sources.
The big picture
Solar heating systems for service hot water have high initial costs. With governmental support of about 25% of the initial cost, small Canadian solar service hot water systems will have a payback period comparable to the system life. The market for these systems is therefore limited to consumers ready to pay a premium on energy from renewable sources or to consider their investment based on the entire life-cycle cost of the system.
Photos
Motel - Solar water heater - Solar collector - Glazed, Quebec, Canada
Motel - Solar water heater - Storage tank, Quebec, Canada
References
- Gagné, Benoit, "Personal comunication," Motel St-Côme, 2000.
- Logie, Richard B., "Personal communication," CANMET Energy Technology Centre, Natural Resources Canada, 2000.
- Hosatte, Pierre, "Personal communication," TN Conseil, 2000.
