-
35 Languages:
Heating - Solar water heater - House / Canada
Case study assignment
You wish to examine the financial viability of using solar water heating to supply some of the domestic hot water requirements for a single family home. The owner of the home is keen to use renewable energy to satisfy a portion of his energy consumption. He would like a year-round system that operates in a freeze protected configuration.
Site information
The home is located in North Vancouver, British Columbia, Canada. The 2-storey, 185 m² home has 3 occupants. The roof has a pitch of 12 in 12 and faces due south. A high-efficiency, natural gas-fired water heater already exists in the house.
The solar storage tank will be located in a room on the ground floor; the horizontal distance from the collector to the storage tank will be 3 m. Since there is little space available, a standard 150-litre tank will be used. All piping shall be copper with foam insulation. A small heat exchanger and pump will be used.
Financial information
The customer will purchase the system out of savings. He suggests that a discount rate equal to current mortgage rates be used. These average around 8%. The retail price of natural gas is currently $0.44/m³, but this is very high compared to prices in the recent past: a year ago, it was $0.24/m³. The retail price for electricity is $0.06/kWh. Inflation averages about 2.2%.
New glazed solar collectors have a life expectancy of 25 years. In the Province of British Columbia, solar hot water systems are exempt from provincial sales tax of 7%.
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 the summer of 1997, a solar domestic water heating system was installed in the Kadulski residence, located in North Vancouver, British Columbia, Canada. At the same time, this turn-of-the century home underwent a major renovation aimed at improving its energy efficiency; super insulation and high efficiency heating were installed. The 2-storey, 185 m2 home has 3 occupants.
System description
The system works by circulating water through the solar collectors whenever the controller indicates there is useful energy to be gained. The heated water from the solar collectors is stored in a standard 150-litre water tank. The differential temperature solar controller operates a high-head circulating pump. The pump feeds and returns to a 20-litre drainback reservoir tank. When the pump shuts off, the water in the solar collectors drains back into the reservoir tank to ensure that the system is protected from freezing.
Three 2.2 m² (0.9 m by 2.4 m) glazed flat plate collectors are mounted on wood sleepers fastened to the rafters below the roof. Copper piping (13 mm in diameter) with foam insulation is used to ensure adequate flow. To save space, a 150-litre storage tank (a standard 40 U.S. gallon electric water tank) was used. A small shell-in-tube side-arm heat exchanger transfers heat by natural convection from the solar loop to the solar storage tank.
Solar energy now provides 2 MWh (7.2 Gigajoules) of energy, about half of the hot water for the home, and avoids 0.5 tonne per year of greenhouse gas emissions.
Lessons learned
The big picture
Domestic hot water, used for such things as laundry, showers, and dishes, can account for up to 20% of a home's energy use. Next to space heating, it is the home's largest energy requirement. Most hot water heaters in Canada currently use natural gas or electricity. Heating with solar energy is an excellent way to reduce pollution; a system avoids up to 2 tonnes a year of greenhouse gas emissions.
A SDHW system can be a straightforward retrofit to most homes, and can typically provide over 50% of the annual hot water needs. With a projected life of 20 to 40 years, most SDHW systems pay for themselves in 15 to 30 years, while they reduce dependence on non-renewable resources.
Homes off-grid or those using propane or electricity for water heating offer the best economic opportunity for SDHW.
Photo
House - Solar water heater, British Columbia, Canada
References
Case study assignment
You wish to examine the financial viability of using solar water heating to supply some of the domestic hot water requirements for a single family home. The owner of the home is keen to use renewable energy to satisfy a portion of his energy consumption. He would like a year-round system that operates in a freeze protected configuration.
Site information
The home is located in North Vancouver, British Columbia, Canada. The 2-storey, 185 m² home has 3 occupants. The roof has a pitch of 12 in 12 and faces due south. A high-efficiency, natural gas-fired water heater already exists in the house.
The solar storage tank will be located in a room on the ground floor; the horizontal distance from the collector to the storage tank will be 3 m. Since there is little space available, a standard 150-litre tank will be used. All piping shall be copper with foam insulation. A small heat exchanger and pump will be used.
Financial information
The customer will purchase the system out of savings. He suggests that a discount rate equal to current mortgage rates be used. These average around 8%. The retail price of natural gas is currently $0.44/m³, but this is very high compared to prices in the recent past: a year ago, it was $0.24/m³. The retail price for electricity is $0.06/kWh. Inflation averages about 2.2%.
New glazed solar collectors have a life expectancy of 25 years. In the Province of British Columbia, solar hot water systems are exempt from provincial sales tax of 7%.
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
- Although this installation was not justified on the basis of its financial performance, the customer was very content to be able to supply some of his own energy with renewables. The price of natural gas in British Columbia is very low, making it among the cheapest forms of energy available residentially in Canada. A less expensive seasonal solar water heater that displaced electricity or propane would have much better financial performance and be appropriate for the West Coast climate.
- Unglazed collectors would be less expensive than glazed collectors and produce about 75% as much energy, per unit area of collector.
- A solar domestic hot water system such as this one requires no annual maintenance. The drain-back design makes glycol or other antifreeze unnecessary, eliminating costs associated with periodic antifreeze replacement. Eventually the circulating pump will fail and need replacement; this has been accounted for as a periodic cost.
- The price of gas has been estimated as the average of the price a year ago and the current price, i.e., $0.34/m³. This price has been increased by 7% to account for the provincial sales tax that is levied on gas but not on solar water heating systems. The fuel cost escalation rate has been set to 3.5%, somewhat higher than inflation.
- Costs have been given for the feasibility study and engineering. In reality, these would not be separate costs charged to the customer, but would be folded into the installed cost of the system. The consultant separated these costs to illustrate their relative importance.
- RETScreen suggests using 2 collectors, based on energy considerations, but 3 collectors have been used. This reflects financial considerations: smaller systems cost more on a per unit basis. With 2 collectors, the cost of the feasibility study and engineering would change little, but energy revenues would drop considerably. A 4-collector system would tend to generate significant amounts of hot water at times when it could not be used.
Real project
Results
In the summer of 1997, a solar domestic water heating system was installed in the Kadulski residence, located in North Vancouver, British Columbia, Canada. At the same time, this turn-of-the century home underwent a major renovation aimed at improving its energy efficiency; super insulation and high efficiency heating were installed. The 2-storey, 185 m2 home has 3 occupants.
System description
The system works by circulating water through the solar collectors whenever the controller indicates there is useful energy to be gained. The heated water from the solar collectors is stored in a standard 150-litre water tank. The differential temperature solar controller operates a high-head circulating pump. The pump feeds and returns to a 20-litre drainback reservoir tank. When the pump shuts off, the water in the solar collectors drains back into the reservoir tank to ensure that the system is protected from freezing.
Three 2.2 m² (0.9 m by 2.4 m) glazed flat plate collectors are mounted on wood sleepers fastened to the rafters below the roof. Copper piping (13 mm in diameter) with foam insulation is used to ensure adequate flow. To save space, a 150-litre storage tank (a standard 40 U.S. gallon electric water tank) was used. A small shell-in-tube side-arm heat exchanger transfers heat by natural convection from the solar loop to the solar storage tank.
Solar energy now provides 2 MWh (7.2 Gigajoules) of energy, about half of the hot water for the home, and avoids 0.5 tonne per year of greenhouse gas emissions.
Lessons learned
- Some clients may prefer to buy used solar collectors and significantly reduce the cost of the system.
- Electric water heater tanks are typically the most economical form of solar storage tank for solar domestic hot water (SDHW) applications.
The big picture
Domestic hot water, used for such things as laundry, showers, and dishes, can account for up to 20% of a home's energy use. Next to space heating, it is the home's largest energy requirement. Most hot water heaters in Canada currently use natural gas or electricity. Heating with solar energy is an excellent way to reduce pollution; a system avoids up to 2 tonnes a year of greenhouse gas emissions.
A SDHW system can be a straightforward retrofit to most homes, and can typically provide over 50% of the annual hot water needs. With a projected life of 20 to 40 years, most SDHW systems pay for themselves in 15 to 30 years, while they reduce dependence on non-renewable resources.
Homes off-grid or those using propane or electricity for water heating offer the best economic opportunity for SDHW.
Photo
House - Solar water heater, British Columbia, Canada
References
- Thwaites, Joe, "Personal communication," Taylor Munro Energy Systems Inc., 2000.
