Authors
- Nasim Alam
- Samantha Kapushy
- Umar Mutwafy
- Lyrica Yanaway
Mentor
Molly Over
Abstract
The heating and cooling requirements of a building are a significant portion of the average buildings’ energy usage and traditionally leads to higher consumption of non-renewable fossil fuels. MicroEra Power plans to use phase-changing materials (PCMs) to achieve thermal energy storage in combination with a heat pump to provide flexibility of electrical power usage for HVAC (Heating, Ventilation, Air Conditioning) for medium to large buildings. Implementing this technology would increase the integration of sustainable materials on the grid.
Problem Statement
Currently, MicroEra does not have an efficient system for testing a PCM sample with an average heating-cooling cycle time of 20 minutes. This project aims to manufacture a device capable of testing phase change materials to determine their stability which will allow MicroEra Power to determine suitable phase-change materials for different applications.
Requirements
- Non-reactive container for storing the PCM while testing. A list of approved materials was provided by MicroEra Power.
- PCM container can be cleaned, filled, and emptied.
- Device to heat the PCM to the desired temperature.
- Device to cool the PCM to the desired temperature.
- Device must be insulated to keep the system thermally isolated from the surroundings.
Specifications
- Can cool PCM to -10oC within +/-1oC.
- Can heat PCM to 100oC within +/-1oC.
- Contains a minimum volume of 50 mL within +/-1 mL of PCM.
- Contains a maximum volume of 250 mL within +/-1 mL of PCM.
- Can complete a minimum of 1 cycle per 20 minutes of a PCM in the temperature range of -10oC to 20oC.
- Can complete a minimum of 1 cycle per 20 minutes of a PCM in the temperature range of Ambient to 90oC.
- Has a total system mass of less than 45 kg.
- Has a total system volume of less than 1 meter width x 1 meter depth x 1 meter height.
- Has the ability to measure the filled container, PCM’s volume within +/-1mL of total.
- Has the ability to hold sample at 100oC and -10oC within a range of +/-1oC for 2 minutes.
Design Description
Several designs were considered for this project. The selected design incorporated Peltier Thermoelectric Modules to provide heating and cooling to the system with aluminum cooling blocks to manage the waste heat generated during the cooling cycles.
The PCM chamber was constructed by welding a 2 in x 2 in square of stock stainless steel onto the bottom of a 12 in long piece of 2 in x 2 in square stainless steel tubing. Stainless steel was selected as it was one of the best thermal conductors among the approved materials. A polyethylene endcap with a hole drilled in the center was used to seal the top of the chamber, while allowing the temperature sensors access to the material being tested.
Four aluminum brackets were fabricated to keep all components in place and ensure good conductivity between the thermoelectric and the PCM chamber. These brackets were held together using bolts and featured seven small screws positioned around the cooling blocks and thermoelectrics to ensure these components remained in the optimal position.
Thermoelectrics were placed on each side of the PCM chamber. The system was designed to operate with anywhere from four to twelve thermoelectrics, depending on the available voltage and the heating and cooling requirements of the material being tested. Due to safety concerns regarding the magnitude of the voltage required, the system was tested with only one thermoelectric at a time. The cooling blocks were attached to the cold water system in the laboratory using braded tubing. The tubing lead from the cold water supply, into the cooling blocks, and to the return trench. Hose clamps were used to ensure a strong connection between the tubing and the cooling blocks. The thermoelectrics used a combination of DC Motor drivers and LabJacks and were controlled using LabVIEW.