Lesson Plan (Grades 9–12): Solar-Thermal Wind Tunnel – Harnessing Heat-Driven Airflow

Lesson Title: Solar-Thermal Wind Tunnel – Harnessing Heat-Driven Airflow

Grade Level: Grades 9–12

Subject Area: Physics (Thermodynamics & Fluid Dynamics) / Engineering (Thermal Systems) / Environmental Science (Renewable Energy)

Overview: Renewable energy technologies often harness wind or solar resources, but solar-thermal updraft towers combine both: sunlight heats air, which rises through a chimney to drive turbines. In this hands-on STEM unit, students work in teams to design, build, and test a small-scale solar-thermal “wind tunnel.” They will use parabolic reflectors or foil-lined troughs to concentrate sunlight onto a section of PVC ducting, heating the air inside. Buoyancy drives the warmed air through the tunnel, and students measure airflow velocity with anemometers and temperature differences with thermocouples. By varying reflector geometry, duct diameter, insulation, and orientation, learners explore the relationships between solar irradiance, temperature rise (∆T), and convective flow speed. They calculate volumetric flow rates (Q = A·v), estimate thermal-to-kinetic energy conversion efficiency, and discuss applications in passive ventilation systems or solar updraft towers. This lesson plan provides detailed objectives, materials, step-by-step procedures, differentiation strategies, assessments, and extension ideas to support teachers in delivering a rich inquiry-based experience.

Objectives and Standards

Learning Objectives

1. Thermodynamics & Buoyancy: Explain how solar radiation absorbed by a dark surface increases air temperature inside the duct, creating density differences (∆ρ) that produce buoyant flow.
2. System Design: Design and construct a solar-thermal wind tunnel using parabolic or trough reflectors, PVC ducting, and insulation to maximize temperature rise and airflow.
3. Instrumentation & Measurement: Deploy thermocouples to measure inlet and outlet air temperatures (T₁ and T₂), and anemometers to record airflow velocities (v) at the tunnel exit.
4. Data Analysis: Calculate volumetric flow rate Q = A·v (where A is duct cross-sectional area) and examine how ∆T and solar irradiance (I in W/m²) correlate with v.
5. Energy Conversion Efficiency: Estimate the device’s thermal-to-kinetic conversion efficiency using η = (½·ρ·Q·v²)/(I·A_reflector), comparing theoretical and experimental values.
6. Renewable Applications: Evaluate potential real-world uses—passive solar ventilation, solar updraft towers—and propose design optimizations based on student data.

Standards Alignment

• Next Generation Science Standards (NGSS)
  • HS-PS3-3: Design, build, and refine a device that converts energy from one form to another (solar to thermal to mechanical flow).
  • HS-ESS3-4: Evaluate or refine a technological solution that reduces environmental impacts of energy use (e.g., passive ventilation).
• Common Core Mathematics
  • HS-REI.B.3: Solve literal and multistep equations to analyze relationships (e.g., solving for v in buoyancy equations).
  • HS-F.LE.A.1: Distinguish between linear and exponential models (analyzing flow response vs. temperature difference).
• NGSS Crosscutting Concepts
  • Energy and Matter: Tracing energy flow from sunlight to thermal energy to kinetic energy of moving air.
  • Systems and System Models: Considering reflector, ducting, and measurement instruments as an integrated system.