Thermal Storage Tiles for Cooler Indoor Spaces

ISEF Category: Materials Science

Subcategory: Ceramic and Glasses  ·  Difficulty: Intermediate  ·  Setup: School Lab  ·  Time: 1 to 2 Months

The Hook

A wall can act like a battery for heat. If a tile can soak up warmth during the day and give it back later, your room may stay steadier without extra power. That idea sits behind phase-change thermal-storage tiles. You can test whether a cheap ceramic tile soaked with paraffin really smooths indoor temperature swings.

What Is It?

This project studies a material trick. Paraffin is a phase-change material, which means it absorbs or releases a lot of heat when it melts or solidifies. Terracotta is porous, so it can hold paraffin inside tiny holes. Think of the tile like a sponge, but for heat instead of water.

When the room warms up, the paraffin starts to melt and absorbs heat. When the room cools, it solidifies and gives some heat back. That can slow down how fast the air temperature changes near the tile. You are not trying to make the room cold. You are trying to make the temperature swing less sharply.

Why This Is a Good Topic

This is a strong science fair topic because you can test a clear cause and effect. You change the tile treatment, then measure how well it reduces temperature swings. That gives you real data, not just a pretty prototype. The project connects to energy use, passive cooling, and building design, and you can learn materials testing, sensor logging, and data analysis without needing a full research lab.

Research Questions

• How does paraffin loading level affect the amount of indoor temperature swing reduction in terracotta tiles?
• What is the effect of tile thickness on how long the tile delays peak temperature rise?
• Does sealing the tile surface change the thermal buffering performance of paraffin-impregnated terracotta?
• To what extent does repeated heating and cooling cycle change the tile's ability to store heat?
• Which tile composition, plain terracotta or paraffin-impregnated terracotta, produces the lowest peak indoor temperature near the sensor?
• How does the placement of the DHT22 sensor relative to the tile affect the measured temperature attenuation?

Basic Materials

• Terracotta tiles of the same size and thickness.
• Paraffin wax with a known melting range.
• Hot plate or water bath for controlled heating.
• Digital kitchen scale with 0.1 g accuracy.
• Aluminum foil or heat-safe trays.
• DHT22 temperature and humidity sensor.
• Arduino board.
• Breadboard and jumper wires.
• Laptop with Arduino IDE.
• Cardboard box or insulated container for a simple test chamber.
• Tape measure or ruler.
• Timer or stopwatch.

Advanced Materials

• Differential scanning calorimetry access for phase-change characterization.
• Universal testing machine or simple flexural setup for comparing tile strength after impregnation.
• Thermal camera or infrared thermometer for surface temperature mapping.
• Environmental chamber or controlled hot-box setup.
• Data logger compatible with Arduino sensor streams.
• Scanning electron microscope access for pore-filling observation.
• Porosity measurement setup.
• Sealant samples for surface-treatment comparison.

Software & Tools

• Arduino IDE: Uploads code and logs DHT22 sensor data from your tile setup.
• Google Sheets: Organizes time series data and helps you graph temperature changes.
• Python: Fits curves, compares groups, and calculates thermal buffering metrics.
• ImageJ: Measures surface coverage if you photograph wax distribution or cracking.
• GeoGebra: Helps you make quick plots and compare cooling curves.

Experiment Steps

1. Define the performance metric you will compare, such as peak temperature reduction, time to peak, or area under the temperature curve.
2. Choose one material variable to change first, such as paraffin content, tile thickness, or sealant type.
3. Design a control group with plain terracotta so you can separate the effect of the phase-change material from the tile itself.
4. Plan a sensor layout that records both the tile response and the nearby air response in the same test chamber.
5. Decide how you will repeat each trial and how you will randomize the order so room conditions do not bias one group.
6. Set up a data analysis plan that compares heating and cooling curves, not just single final temperatures.

Common Pitfalls

• Letting paraffin coat only the surface instead of soaking into the pores, which gives weak thermal storage.
• Comparing tiles that differ in size or thickness, which mixes geometry effects with material effects.
• Mounting the DHT22 too close to a warm tile or heat source, which measures the tile surface instead of room air.
• Running trials in changing sunlight or draft conditions, which overwhelms the tile effect.
• Looking only at one peak temperature, which misses how long the tile delays heating and how much heat it buffers over time.

What Makes This Competitive

A stronger project goes beyond a simple before-and-after test. You can compare several paraffin loadings, add a plain tile control, and analyze full temperature curves instead of one number. You can also test durability across repeated cycles, which matters for real building use. Strong students often pair thermal data with another measurement, like mass change, porosity, or surface imaging.

Project Variations

• Try different porous ceramics, such as brick, clay pavers, or terracotta roof pieces, to see which stores heat best.
• Compare paraffin-impregnated tiles with salt-hydrate phase-change inserts to test a different thermal-storage material.
• Add a reflective coating or sealant layer and test whether the surface treatment changes indoor temperature attenuation.
• Use a small model room or insulated box and compare sensor locations near the wall, at mid-air, and near the ceiling.

Learn More

• MIT OpenCourseWare, materials science courses: Search MIT OpenCourseWare for introductions to heat transfer, phase changes, and porous materials.
• NASA Earth Observatory, surface energy balance resources: Search NASA for articles on how materials absorb, store, and release heat.
• NIST, thermal properties data: Search the National Institute of Standards and Technology for thermal conductivity and heat capacity references.
• PubMed, review articles on phase-change materials: Search PubMed for reviews on paraffin phase-change materials and building applications.
• Ceramics International: Search the journal for papers on porous ceramics, wax impregnation, and thermal storage.
• NOAA Climate.gov, heat and temperature basics: Search NOAA for clear explanations of temperature variation and energy flow.