Below is a spreadsheet detailing the resources our team has purchased in completing our final prototype. The major items we purchased, in terms of their cost, were: the heat pump, which cost $999.99 and was also the first item we purchased, the PureTemp phase change material, of which we ordered 5 gallons for $492.68, and the copper tubing, acrylic sheet, and rivets which totaled $598.88. These items made up about 70% of the total we spent on this project and are items which were absolutely necessary in completing our prototype.
| Date | Line Item | Line Item Cost | Running Total | Total Remaining (out of $3,700) |
| 1/13/2023 | Heat Pump | $999.99 | $999.99 | $312.76 |
| 2/3/2023 | Transformer | $99.59 | $999.99 | (returned) |
| 2/7/2023 | PCM | $492.68 | $1,492.67 | |
| 2/15/2023 | Duct pieces & new transformer | $116.98 | $1,609.65 | |
| 2/15/2023 | Duct wyes and collar | $67.04 | $1,676.69 | |
| 3/3/2023 | Sheet Metal | $50.75 | $1,727.44 | |
| 3/3/2023 | PCM Sealing Test Parts | $58.35 | $1,785.79 | |
| 3/6/2023 | Copper Tube, Acrylic Sheet, Rivets and Riveter | $598.88 | $2,384.67 | |
| 3/16/2023 | Stepper motors, thermocouple shield | $107.84 | $2,492.51 | |
| 3/16/2023 | Duct booster fan | $52.99 | $2,545.50 | |
| 3/20/2023 | Aluminum plate and actuator parts | $168.57 | $2,714.07 | |
| 3/24/2023 | Rubber Stoppers | $51.00 | $2,765.07 | |
| 3/24/2023 | 2 New Dampers | $56.00 | $2,821.07 | |
| 3/24/2023 | Copper tube caps | $28.41 | $2,849.48 | |
| 3/30/2023 | Aluminum Angle | $13.89 | $2,863.37 | |
| 3/30/2023 | Duct flow sensors | $57.98 | $2,921.35 | |
| 3/31/2023 | 2 New Dampers (Better Design) | $67.98 | $2,989.33 | |
| 4/4/2023 | Gear | $38.82 | $3,028.15 | |
| 4/5/2023 | Gear | $54.69 | $3,082.84 | |
| 4/10/2023 | Set Screws and Motor Drivers | $58.98 | $3,141.82 | |
| 4/11/2023 | Power Supply | $9.89 | $3,151.71 | |
| 4/11/2023 | Pressure Sensors | $177.12 | $3,328.83 | |
| 4/11/2023 | Clear tubing for PCM and pressure sensing | $58.41 | $3,387.24 |
In terms of tools, the machine shop, 3D printers, and tool cart in Acopian Engineering Center (AEC) room 006 were mostly able to provide what was needed. We made extensive use of the water jet cutter in the machine shop for cutting both the acrylic and metal components of the heat exchanger. We also used the sheet metal press as well as a variety of hand tools including a copper tube cutter, hand drills, files, clamps, etc.
AEC 006 was also able to provide the space needed to manufacture and fit our final prototype. Two tables were put together to support the final prototype, which included the purchased heat pump, our heat exchanger, the transition piece, and the final circular ducts. Other tables throughout the space were used for manufacturing and the floor space was used to fill the tubes with PCM (when outdoor space was unavailable due to weather).
Expense Reflection *might make sense for this to be on a separate page from the above
Our team sat down to collectively discuss and reflect on our final expenses after the bulk of assembly was completed. Overall, we are aware that our senior design team spent more money than other teams and that although we were originally aiming to spend below $3,000, that number had to end up being increased to a “will not exceed” number of $3,700. We do feel, however, that the money we spent is reasonable, especially compared to what we pay in tuition.
The prices of many of the individual components we purchased, including the raw materials, off-the-shelf duct components like the duct booster fan, and the duct wyes and sheet metal used to create the transition piece were pretty reasonable, especially considering that they made up a substantial portion of our final prototype.
Furthermore, it seems to us that based on our prototype cost, the production cost could be competitive within the residential market our project is geared towards. To evaluate the cost of the production product, it is important to subtract certain costs, including the costs of the heat pump and ductwork outside of the dampers, since homes would already be outfitted with those components, the sample pricing of the PCM, and small quantity added pricing for raw materials and gears. As for the pressure sensors and other duct-mounted components, we are aware that they were relatively expensive, but if this were a production product, it’s unlikely that we would need airflow sensors everywhere; we would likely be able to come up with a calibration, rather than using as many sensors.
Overall, our team previously outlined a few functional requirements under the heading of Financial Justification. Per constraint 4.2, our final prototype did stay under the allowable budget, although that budget did have to be changed a couple times for our project, and per objective 4.3, our team did use locally and commercially available components, like those already available in the machine shop, in order to keep our prototype cost down. Given everything outlined above, the goal of a mass-produced product that is affordable to the end user still seems feasible.