A concentrated solar power, or CSP, tower receiver is the high-temperature device at the top of a solar tower where reflected sunlight becomes useful heat. Thousands of mirrors called heliostats aim sunlight onto the receiver, greatly increasing the energy arriving at its surface. This heat can be stored, used to make steam, and converted into electricity after sunset.
The receiver matters because it is the point where solar radiation is transformed into thermal energy for a power plant.
Key Facts
- Solar power on the receiver is Psolar = I A C, where I is sunlight intensity, A is mirror area, and C represents optical concentration and losses.
- Useful heat gained by the working fluid is Q = m c ΔT.
- Thermal power transferred to the fluid is P = ṁ c ΔT.
- Receiver efficiency can be estimated by η = Puseful / Psolar.
- Radiative heat loss rises strongly with temperature: Prad = ε σ A T^4.
- Molten salt receivers often operate near 290°C entering and 565°C leaving the receiver.
Vocabulary
- CSP receiver
- A device that absorbs concentrated sunlight and transfers the energy as heat to a working fluid.
- Heliostat
- A sun-tracking mirror that reflects sunlight toward a central receiver.
- Working fluid
- A moving liquid or gas that carries thermal energy through a system.
- Molten salt
- A liquid salt mixture used in some CSP plants to absorb, transport, and store heat.
- Thermal efficiency
- The fraction of incoming energy that becomes useful heat or work rather than being lost.
Common Mistakes to Avoid
- Confusing the receiver with a solar panel is wrong because a CSP receiver makes heat, while a photovoltaic panel makes electricity directly.
- Ignoring heat losses is wrong because high-temperature receivers lose energy by radiation, convection, and conduction.
- Using Celsius directly in T^4 radiation calculations is wrong because absolute temperature in kelvin must be used.
- Assuming all reflected sunlight reaches the receiver is wrong because mirrors have reflectivity losses, aiming errors, shading, and atmospheric losses.
Practice Questions
- 1 A heliostat field sends 120 MW of solar power to a receiver. If the receiver transfers 96 MW to molten salt, what is the receiver efficiency?
- 2 Molten salt flows through a receiver at 850 kg/s with specific heat 1500 J/(kg°C). If its temperature rises by 275°C, what thermal power is transferred to the salt?
- 3 Explain why a CSP receiver must balance very high sunlight absorption with protection against overheating and heat loss.