Low-Cost Elastocaloric Heat Pump — Polymer Film Platform

Getting started · Documentation

Research project · Institute of Microstructure Technology (IMT) · KIT
Zero-emission Thermal Technologies — Dr. Jingyuan Xu Group

_{Live Monitor tab in Demo Mode — Natural Rubber film cycling at 0.4 Hz, ΔTad ≈ 2.5 K, rolling COP 4.42. All four sensor channels update at 10 Hz. No hardware required to explore the interface.}

EC-Lab is a dedicated desktop research tool for daily lab use — live serial monitor from the Arduino controller, in-app DSC and COP analysis, polymer film sample database with fatigue tracking, material comparison against the SMA baseline, and one-click HTML report export. A built-in Demo Mode runs a full simulated elastocaloric cycle so every feature works without connecting any hardware.

Installs in one click. Updates automatically in the background. See app/ for source code and development instructions.

Conventional vapor-compression cooling accounts for roughly 20 % of global electricity consumption and relies on HFC refrigerants with global-warming potentials orders of magnitude above CO₂. Elastocaloric (eC) cooling eliminates both problems: the working body is a solid-state material — no refrigerant, no compressor, no leakage risk.

Shape-memory alloy (SMA) films already demonstrate world-class eC performance (ΔT_ad > 20 K, specific cooling power up to 19 W g⁻¹ for TiNiCuCo). This project asks the complementary question: can polymer films achieve a practically useful eC effect at a fraction of the material cost? Polymers such as natural rubber (NR), PVDF, and silicone elastomers cost < 5 € m⁻² and offer strain amplitudes exceeding 300 %, making them attractive for large-area, low-cost demonstrators even if their volumetric eC effect is smaller.

      ┌─────────── STRESS APPLIED ──────────────┐
      │  Polymer chains align → entropy ↓        │
      │  Adiabatic temperature RISES (ΔT > 0)    │
      │  Heat rejected to hot side (heat sink)   │
      └──────────────────────────────────────────┘
                         │
               [mechanical cycle]
                         │
      ┌─────────── STRESS RELEASED ─────────────┐
      │  Chains relax → entropy ↑               │
      │  Adiabatic temperature DROPS (ΔT < 0)   │
      │  Heat absorbed from cold side (load)     │
      └──────────────────────────────────────────┘

The adiabatic temperature change under uniaxial stress is governed by:

ΔT_ad = − (T / ρ c_p) · (∂σ/∂T)_ε · Δε

where ρ is density, c_p specific heat, σ engineering stress, and Δε the applied strain amplitude.
The Coefficient of Performance of an ideal regenerative eC cycle is:

COP_ideal = T_cold / (T_hot − T_cold)     [Carnot limit]
COP_device = Q_cold / W_mech              [measured]

elastocaloric-heat-pump/
├── materials/               # Raw characterization data per film type
│   ├── natural_rubber/
│   ├── pvdf/
│   └── silicone/
├── experiments/             # Measurement data organized by campaign
│   ├── 01_dsc/              # Differential scanning calorimetry
│   ├── 02_tensile/          # Stress–strain & fatigue testing
│   ├── 03_ir_thermography/  # IR camera recordings during cycling
│   └── 04_demonstrator/     # Full-cycle COP measurements
├── analysis/                # Python analysis scripts and notebooks
│   ├── dsc_analysis.py
│   ├── ir_thermography.py
│   ├── cop_calculator.py
│   └── notebooks/
│       └── 01_baseline_characterization.ipynb
├── design/                  # CAD and schematic files for demonstrator
├── firmware/                # Microcontroller code (Arduino/STM32)
├── results/                 # Processed figures and summary tables
├── docs/
│   ├── theory.md
│   ├── setup.md
│   └── materials_selection.md
└── .github/workflows/
    └── validate.yml

• Python ≥ 3.11
• Hardware: linear actuator, force sensor, IR camera or thermocouple array, microcontroller

pip install -r requirements.txt

jupyter notebook analysis/notebooks/01_baseline_characterization.ipynb

python analysis/validate_data.py

This project directly extends the ZET group's SMA film-based eC cooling platform to low-cost polymer substrates, addressing the cost-scalability gap identified in recent SMA film device work (Xu et al., Shape Memory and Superelasticity, 2024). Polymer films share the large surface-to-volume advantage of SMA foils for solid-contact heat transfer while offering a dramatically reduced material cost — a prerequisite for residential and consumer-scale deployment.

1. Xu J. et al. (2024). SMA Film-Based Elastocaloric Cooling Devices. Shape Memory and Superelasticity. https://doi.org/10.1007/s40830-024-00484-y
2. Greibich F. et al. (2021). Elastocaloric heat pump with specific cooling power of 20.9 W g⁻¹. Nature Energy, 6, 260–267.
3. Moya X. & Mathur N. D. (2020). Caloric materials for cooling and heating. Science, 370(6518), 797–803.
4. Tušek J. et al. (2016). A regenerative elastocaloric heat pump. Nature Energy, 1, 16134.

MIT — see LICENSE