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Heating - Solar water heater - Swimming pool - Indoor / Canada (Calgary Int'l Airport)
Case study assignment
The municipal swimming pool in Okotoks, Alberta, is an all-season, indoor facility that currently uses natural gas as the heating fuel to maintain the temperature of the pool water. As a member of town council you want to investigate the option of using solar water heating (SWH) as a sustainable way to provide heat to the pool while at the same time reducing greenhouse gas (GHG) emissions and operating costs.
Site information
Okotoks is a town of 12,000 located 32 km south of Calgary, the nearest weather station. The swimming pool has two areas: a 4-lane competition area (8 m wide by 25 m long) and a shallow leisure area. The leisure area is a 10-m extension to the 4-lane competition area. The pool is heated to 29ºC and used year round. A pool cover is not used.
Because of the all-season operation, a local SWH system installer has recommended that you consider a glazed collector system with a heat exchanger and antifreeze protection (e.g. glycol-water solution as the working fluid in the solar loop). The horizontal distance from the mechanical room to the area where the solar collectors can be installed is 15 m for this one-story building.
The fuel mix for electricity generation in Alberta is approximately 90% coal, 4% large hydro and 6% natural gas.
Financial information
As a first estimate, you have obtained a price of $250/m² for a model G32 glazed collector manufactured by Thermo Dynamics Ltd. The labour to install the collectors will cost about $60/m². It is expected that the municipality will receive an incentive for 25% of the cost of the SWH system (up to a maximum of $80,000) from a federal government incentive.
The town will need to borrow 80% of the money needed to fund this project, to be paid back over 20 years. The interest rate quoted by an Okotoks bank is 9%. You can assume a 9% discount rate, a 2% inflation rate and a 3% fuel cost escalation rate over a project life of 25 years.
The city pays an effective rate of 7¢/kWh for electricity and 30¢/m³ for natural gas.
Prepare a RETScreen study to determine the feasibility of the project. Document 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
Okotoks is a town of 12,000 located 32 km south of Calgary. In keeping with the mandate of its "Sustainable Okotoks" program, the municipality decided to install a solar water heating (SWH) system to heat its indoor swimming pool. The facility includes a 4-lane, 25-m long competition-size pool as well as an adjoining shallow basin. Construction on the SWH system began in October 2002.
System description
Evacuated tube collectors (ETC) were initially investigated, but it was found that the higher performance from ETC was not required for this particular project and that less costly glazed flat-plate solar collectors would result in a more favourable payback period. Collectors from Thermo Dynamics Ltd. (model G32) were selected and 100 collectors, with a total glazed area of 300 m2, were installed on the roof of the pool building. To allow for all-season operation, an antifreeze working fluid is pumped in a closed-loop between the collectors and a heat exchanger, where it gives up its energy to heat the pool water.
Lessons learned
The big picture
Solar water heating for outdoor swimming pools has long been an accepted practice using relatively inexpensive unglazed collectors. The heating demands of year-round indoor swimming pools in cold climates require higher performance solar collectors with freeze protection.
With the increasing cost of conventional heating fuels and increasing awareness regarding greenhouse gas emissions, more municipalities are turning to solar energy for pool heating. Lead by the growing popularity of unglazed collectors for summer-only pools, all-season pools are increasingly also being considered for solar heating.
Photos
Solar water heater - Swimming pool - Indoor, Alberta, Canada - Photo 1
Solar water heater - Swimming pool - Indoor, Alberta, Canada - Photo 2
References
Case study assignment
The municipal swimming pool in Okotoks, Alberta, is an all-season, indoor facility that currently uses natural gas as the heating fuel to maintain the temperature of the pool water. As a member of town council you want to investigate the option of using solar water heating (SWH) as a sustainable way to provide heat to the pool while at the same time reducing greenhouse gas (GHG) emissions and operating costs.
Site information
Okotoks is a town of 12,000 located 32 km south of Calgary, the nearest weather station. The swimming pool has two areas: a 4-lane competition area (8 m wide by 25 m long) and a shallow leisure area. The leisure area is a 10-m extension to the 4-lane competition area. The pool is heated to 29ºC and used year round. A pool cover is not used.
Because of the all-season operation, a local SWH system installer has recommended that you consider a glazed collector system with a heat exchanger and antifreeze protection (e.g. glycol-water solution as the working fluid in the solar loop). The horizontal distance from the mechanical room to the area where the solar collectors can be installed is 15 m for this one-story building.
The fuel mix for electricity generation in Alberta is approximately 90% coal, 4% large hydro and 6% natural gas.
Financial information
As a first estimate, you have obtained a price of $250/m² for a model G32 glazed collector manufactured by Thermo Dynamics Ltd. The labour to install the collectors will cost about $60/m². It is expected that the municipality will receive an incentive for 25% of the cost of the SWH system (up to a maximum of $80,000) from a federal government incentive.
The town will need to borrow 80% of the money needed to fund this project, to be paid back over 20 years. The interest rate quoted by an Okotoks bank is 9%. You can assume a 9% discount rate, a 2% inflation rate and a 3% fuel cost escalation rate over a project life of 25 years.
The city pays an effective rate of 7¢/kWh for electricity and 30¢/m³ for natural gas.
Prepare a RETScreen study to determine the feasibility of the project. Document 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
- Note that this solar water heating (SWH) system requires additional electricity input for pumping, which slightly decreases the overall greenhouse gas (GHG) emissions reduction of the project.
- A pool cover has not been included in the analysis because covers are often not used in large indoor pools. Such covers however can be very effective in saving energy. If the use of a pool cover had been specified in RETScreen in this case, it would not have changed the amount of usable renewable energy that is delivered by the collectors and thus would not have influenced the cost-effectiveness of the SWH system. However, using a pool cover would significantly decrease the amount of natural gas that is used by the back-up heating system. RETScreen provides an estimate of this savings in the form of the reduced "Energy demand for months analysed" (this, in turn, is reflected in an increased solar fraction).
- Note that while the simple payback for this project is over 8 years, the cumulative cash flow curve shows a much more favorable picture. The cash flow for the project is positive from the very beginning because such a large portion (80%) of the initial investment is financed as debt and because the cash incentive available from a federal government incentive is larger than the resulting first-year expenditures. Without debt financing, the project would take about 7 years to reach positive cash flow. This shows the "power" of financing for renewable energy projects.
Real project
Results
Okotoks is a town of 12,000 located 32 km south of Calgary. In keeping with the mandate of its "Sustainable Okotoks" program, the municipality decided to install a solar water heating (SWH) system to heat its indoor swimming pool. The facility includes a 4-lane, 25-m long competition-size pool as well as an adjoining shallow basin. Construction on the SWH system began in October 2002.
System description
Evacuated tube collectors (ETC) were initially investigated, but it was found that the higher performance from ETC was not required for this particular project and that less costly glazed flat-plate solar collectors would result in a more favourable payback period. Collectors from Thermo Dynamics Ltd. (model G32) were selected and 100 collectors, with a total glazed area of 300 m2, were installed on the roof of the pool building. To allow for all-season operation, an antifreeze working fluid is pumped in a closed-loop between the collectors and a heat exchanger, where it gives up its energy to heat the pool water.
Lessons learned
- The cost/performance tradeoffs of various solar collector types must be analysed thoroughly. Glazed collectors may not have as high performance as evacuated tube collectors, but may provide a more cost effective pool heating option.
- While the initial costs of all-season SWH systems can be significantly higher than for summer-only systems, the high heating energy demand of year-round pools can make solar water heating financially very attractive.
The big picture
Solar water heating for outdoor swimming pools has long been an accepted practice using relatively inexpensive unglazed collectors. The heating demands of year-round indoor swimming pools in cold climates require higher performance solar collectors with freeze protection.
With the increasing cost of conventional heating fuels and increasing awareness regarding greenhouse gas emissions, more municipalities are turning to solar energy for pool heating. Lead by the growing popularity of unglazed collectors for summer-only pools, all-season pools are increasingly also being considered for solar heating.
Photos
Solar water heater - Swimming pool - Indoor, Alberta, Canada - Photo 1
Solar water heater - Swimming pool - Indoor, Alberta, Canada - Photo 2
References
- Energy Content Label, Website: http://www.greenenergy.com/Disclosure.html, Retrieved 1 Oct., 2002.
- Howell-Mahew Ltd., Okotoks Solar Heating Inspection Report, 2002.
- Quail, Richard, "Personal communication," Town of Okotoks, 2002.
- Salkeld, Matthew, "Personal communication," EnergyWise Ltd., 2002.
- Shewfelt, Mark, "Personal communication," Enermodal Engineering Ltd., 2002.
