Solar salt — about 60 % sodium nitrate and 40 % potassium nitrate — is the standard storage medium of tower and trough CSP plants. It is pumped from a cold tank through a receiver or heater into a hot tank and back through a steam generator.
Salt freezes at about 220–240 °C, so tanks, pipes and valves need heat tracing and freeze-protection procedures. Chloride and carbonate salts are being developed for higher temperatures.
Key facts
- Solar salt
- NaNO₃ 60 % · KNO₃ 40 %
- Window
- ≈ 290–565 °C
- cp / ρ
- ≈ 1.5 kJ/kg·K · ≈ 1,800 kg/m³
- Freezing
- ≈ 220–240 °C
Two-tank system6
- Hot storage tank
- Cold storage tank
- Storage medium circulation system
- Charging heat exchanger or receiver
- Discharging heat exchanger
- Pumps, piping, insulation and instrumentation
Salt families5
- Solar salt (nitrate)
- Ternary nitrate salts (lower freezing point)
- Chloride salts (higher temperature)
- Carbonate salts
- Advanced and alternative salts
Engineering points6
- Tank foundation cooling
- Heat tracing and freeze protection
- Corrosion and material selection
- Salt melting at commissioning
- Long-shaft vertical pumps
- Leak detection and containment
Freeze and leak risks
Salt freezing, hot-fluid leakage and thermal shock are design-basis risks; procedures and protection must be defined at concept stage.
Related calculators
Calculators are available to staff / admin only.
Related topics
- CSP StorageConcentrated solar power with molten-salt storage generates electricity for hours after sunset.
- High-TemperatureSalts, solids, ceramics and PCMs storing heat at 400–1,300 °C for steel, cement, glass, chemicals and power.
- Heat-to-PowerSteam Rankine, ORC, sCO₂ and closed-cycle gas turbines convert stored or recovered heat into electricity.
- Sensible HeatThe simplest and most deployed principle: energy is stored by heating water, salts, oils or solids without a change of state.
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