Solar Receiver Flux Density & Hot-Spot Map

Heliostat Field

Active heliostats 48

Aim-point spread σ 10°

Direct normal irradiance 850 W/m²

Wind speed 3 m/s

Receiver State

cool

hot

Peak flux density

— kW/m²

Peak panel temp

— °C

Total absorbed thermal power

— MW

How it works

An external cylindrical receiver sits atop the tower and is illuminated only on the arc that faces each heliostat — a panel at azimuth φ receives light from a heliostat at field azimuth ψ only while cos(φ−ψ) > 0. Each heliostat's reflected image is modelled as a Gaussian footprint of angular width σ (the "aim-point spread"), so the flux at a panel is the superposition of every visible heliostat's image:

q(φ) = DNI·ρ·A_h·Δφ · Σᵢ g(φ−ψᵢ, σ)      [W/m², visible ψᵢ only]
g(x,σ) = exp(−x²/2σ²) / (σ√2π)

Fewer, tightly-aimed heliostats (small σ) concentrate power onto a narrow hot band — high peak flux, high risk of tube overheating. Spreading the aim points (large σ) trades a lower peak flux for a more even load, which is exactly why real CSP towers use deliberate aim-point strategies instead of aiming every heliostat at receiver centre.

Each panel's temperature follows a steady-state radiative + convective energy balance, solved every frame by Newton iteration:

α·q(φ) = ε·σ_SB·(T⁴ − T_amb⁴) + h·(T − T_amb)
h ≈ 5.7 + 3.8·v_wind   (forced-convection estimate)

α ≈ 0.95 (selective black absorber coating), ε ≈ 0.88. Wind cools the receiver by raising h; irradiance and heliostat count raise q(φ) directly. Real molten-salt receivers (e.g. Gemasolar, Crescent Dunes) are engineered to keep peak flux below roughly 0.8–1.0 MW/m² to avoid tube-wall failure — watch the peak-flux readout cross that line as you concentrate the field.

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