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Heating - Solar air heater - Warehouse / United States of America
Case study assignment
You are a project manager for a major courier company and you are overseeing the design and construction of a new distribution centre. The city's building codes require a high fresh air ventilation rate since there will be delivery vans driving in and out of the building. You must decide whether to specify conventional natural gas heated air make-up fans, as recommended by a consultant, or solar air heating (SAH).
Site information
The building will be located near Denver, Colorado, USA. This area requires heating for 8 to 9 months of the year and has excellent solar radiation levels. The building codes require 7.6 L/s of heated fresh air per m² of floor area; the building will have a floor area of 5,574 m². The air in the building should be kept above 10 ºC.
The RSI value of the building's ceiling and walls will be around 1.5 (m²-ºC)/W. The walls are prefabricated in concrete and tilted-up into place. No exterior cladding is placed on the concrete. The distribution centre will have drop-in traffic as well as delivery vans and a reliable SAH system could help project a green image for the company. The southeast wall of the building will be located adjacent to the parking lot but it is still partially visible from the road. It will have 465 m² of area suitable for a SAH system. The architect has expressed concern about the appearance of a solar collector, but is willing to consider an all-metal collector (i.e., without glazing) that can be supplied in a colour which compliments the rest of the building. Dark red would be ideal.
The building will be occupied and operating for 12 hours a day, 7 days a week.
Financial information
Your company will borrow 75% of the money for the initial building costs at a rate of 9%; the debt term will be 15 years. You assume that inflation is 2% and that fuel costs will escalate at 3% per year. Your company uses a discount rate of around 10% for this type of investment.
Your company pays income tax at a rate of 34%. In the first year, the federal government will give you a tax credit equal to 10% of the initial solar project costs. Moreover, the project's cost can be depreciated at an accelerated schedule over 6 years, with 20%, 32%, 19.2%, 11.5%, 11.5%, and 5.8% being the annual allowances.
Natural gas prices are approximately US$0.17/m³.
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
Delivery trucks enter Federal Express' new distribution centre and building codes require that the 5,574 m² building have 42,300 L/s of fresh air ventilation. Rather than heat the air entirely by natural gas, a solar air heating (SAH) system was installed. The building is oriented such that 2 walls are potentially suitable for solar collector installation. The southwest wall contains a number of overhead doors and has a jog in it, making it subject to shading. The southeast wall is much better suited to solar heating, as it has a large exposed area and receives the sun in the morning, when the trucks enter and leave the facility. The southeast wall can supply heat to half of the required air using high flow through the solar collector.
A feasibility study indicated that significant energy savings would be possible even with half of the air being heated. The remaining ventilation air would be brought in unheated and then warmed by infrared space heaters; the heaters would also used on cloudy and cold days, when the SAH system supplied insufficient heat to achieve the desired building air temperature of 10 ºC.
The construction of the SAH system started in April 1996 and was completed in June 1996. The SAH system began producing heat in the fall of 1996 and has continued operating since then. The SAH system on the building is an attractive installation and Federal Express has hosted numerous tours of the SAH system since 1996.
Compared to the SAH system, a conventional gas-fired air make-up system would have approximately the same initial costs; its operating costs would be much higher, however.
System description
A dark red SAH system of 465 m² was selected as the exterior cladding for the southeast wall. Three ventilation fans, each providing 7,050 L/s of fresh air, were connected to the solar collector. The dark red colour was selected by the architect and the same colour was carried around the entire building as a feature line.
As the building was owned by a developer, the client agreed to add the cost of the SAH system to the 10-year lease payments at an additional rate of approximately $400 per month. With projected energy savings of over $12,000 per year, or $1,000 per month, Federal Express was able to immediately save approximately $600 per month compared with a gas-heated air make-up system.
Lessons learned
Colonial Red Solar Collector on South Wall of Building, an Architectural Feature of FEDEX's New Distribution Centre Located Near Denver, Colorado, USA
References
Case study assignment
You are a project manager for a major courier company and you are overseeing the design and construction of a new distribution centre. The city's building codes require a high fresh air ventilation rate since there will be delivery vans driving in and out of the building. You must decide whether to specify conventional natural gas heated air make-up fans, as recommended by a consultant, or solar air heating (SAH).
Site information
The building will be located near Denver, Colorado, USA. This area requires heating for 8 to 9 months of the year and has excellent solar radiation levels. The building codes require 7.6 L/s of heated fresh air per m² of floor area; the building will have a floor area of 5,574 m². The air in the building should be kept above 10 ºC.
The RSI value of the building's ceiling and walls will be around 1.5 (m²-ºC)/W. The walls are prefabricated in concrete and tilted-up into place. No exterior cladding is placed on the concrete. The distribution centre will have drop-in traffic as well as delivery vans and a reliable SAH system could help project a green image for the company. The southeast wall of the building will be located adjacent to the parking lot but it is still partially visible from the road. It will have 465 m² of area suitable for a SAH system. The architect has expressed concern about the appearance of a solar collector, but is willing to consider an all-metal collector (i.e., without glazing) that can be supplied in a colour which compliments the rest of the building. Dark red would be ideal.
The building will be occupied and operating for 12 hours a day, 7 days a week.
Financial information
Your company will borrow 75% of the money for the initial building costs at a rate of 9%; the debt term will be 15 years. You assume that inflation is 2% and that fuel costs will escalate at 3% per year. Your company uses a discount rate of around 10% for this type of investment.
Your company pays income tax at a rate of 34%. In the first year, the federal government will give you a tax credit equal to 10% of the initial solar project costs. Moreover, the project's cost can be depreciated at an accelerated schedule over 6 years, with 20%, 32%, 19.2%, 11.5%, 11.5%, and 5.8% being the annual allowances.
Natural gas prices are approximately US$0.17/m³.
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 southeast wall is too small to heat all the building's fresh air; if all the ventilation air was routed through a solar air heating (SAH) system on this wall, excessively high air flow rates would result. Thus, the wall has been used to heat one-half of the building's ventilation air.
- A dark red collector has roughly the same solar absorptivity as a dark grey collector.
- No bypass damper was used for this project. During warm periods the solar half of the building ventilation system does not run; rather, the output of the conventional half of the ventilation system is augmented by leaving the building's large delivery doors open. No additional fans were required by the solar system, and only minimal additional ducting was necessary. This accounts for the low costs for fans and ducting.
- A 5-year straight-line depreciation method has been used to approximate the real 6-year depreciation method.
Results
Delivery trucks enter Federal Express' new distribution centre and building codes require that the 5,574 m² building have 42,300 L/s of fresh air ventilation. Rather than heat the air entirely by natural gas, a solar air heating (SAH) system was installed. The building is oriented such that 2 walls are potentially suitable for solar collector installation. The southwest wall contains a number of overhead doors and has a jog in it, making it subject to shading. The southeast wall is much better suited to solar heating, as it has a large exposed area and receives the sun in the morning, when the trucks enter and leave the facility. The southeast wall can supply heat to half of the required air using high flow through the solar collector.
A feasibility study indicated that significant energy savings would be possible even with half of the air being heated. The remaining ventilation air would be brought in unheated and then warmed by infrared space heaters; the heaters would also used on cloudy and cold days, when the SAH system supplied insufficient heat to achieve the desired building air temperature of 10 ºC.
The construction of the SAH system started in April 1996 and was completed in June 1996. The SAH system began producing heat in the fall of 1996 and has continued operating since then. The SAH system on the building is an attractive installation and Federal Express has hosted numerous tours of the SAH system since 1996.
Compared to the SAH system, a conventional gas-fired air make-up system would have approximately the same initial costs; its operating costs would be much higher, however.
System description
A dark red SAH system of 465 m² was selected as the exterior cladding for the southeast wall. Three ventilation fans, each providing 7,050 L/s of fresh air, were connected to the solar collector. The dark red colour was selected by the architect and the same colour was carried around the entire building as a feature line.
As the building was owned by a developer, the client agreed to add the cost of the SAH system to the 10-year lease payments at an additional rate of approximately $400 per month. With projected energy savings of over $12,000 per year, or $1,000 per month, Federal Express was able to immediately save approximately $600 per month compared with a gas-heated air make-up system.
Lessons learned
- In new construction, the SAH system can be installed for approximately the same cost as a conventional wall and air make-up system. It is important that the building design team of engineers and architects be fully aware of the product so that the SAH can be incorporated into the design as early as possible.
- Appearance is an important criterion and engineers must not be concerned simply with efficiency, but also with aesthetics. A SAH system must be designed to blend in with the building and, if possible, enhance its appearance.
- The client must instruct the architect and engineer to consider the solar option as most architects and engineers appear to be reluctant to consider renewable energy.
Colonial Red Solar Collector on South Wall of Building, an Architectural Feature of FEDEX's New Distribution Centre Located Near Denver, Colorado, USA
References
- Grainger, Richard, "Personal communication," Conserval Systems Inc., 2000.
- Nikiforov, Vladimir, "Personal communication," Conserval Engineering Inc., 2000.
