Solar thermal
Capturing the sun's heat rather than its photons. The decisive advantage of concentrated solar power (CSP) over photovoltaics is built-in thermal storage — molten salts that make solar electricity dispatchable after sunset. The same principle also delivers large-scale industrial and district heat.
The main families
Parabolic trough, solar tower, molten salt
Mirrors concentrate direct sunlight onto a receiver to heat a fluid to high temperature. Parabolic troughs track the sun on one axis; the solar tower focuses thousands of heliostats on a central receiver. The hot fluid drives a conventional steam cycle.
Collectors, process heat (SHIP), district heating
Beyond power generation, solar thermal supplies heat directly. Flat-plate and evacuated-tube collectors feed hot water and space heating. Solar heat for industrial processes (SHIP) covers drying, preheating and low-temperature steam; large collector fields supply district heating networks.
Molten salt, dispatchability, capacity firming
Thermal storage is what sets CSP apart from PV. Hot molten salts are stored in insulated tanks, then drawn down to raise steam once the sun is gone. A few hours of storage shift output into the evening and firm up dispatchable capacity.
Key challenges
- Dispatchability via storage — molten-salt thermal storage is the differentiator versus PV: it shifts output into the evening and firms up dispatchable capacity, where PV stops dead at sunset.
- Optical efficiency & solar tracking — CSP only uses direct normal irradiance (DNI): it is only viable in the sun belt. Heliostat accuracy, mirror cleanliness and tracking quality drive optical efficiency.
- Industrial process heat integration — integrating solar heat (SHIP) into an existing process means matching temperature levels, back-up and buffer storage, and managing intermittency without interrupting production.
- O&M of mirrors & heat-transfer fluid — regular cleaning of mirrors and heliostats, tracking heat-transfer-fluid (HTF) degradation, managing salt freezing and crystallization: operation is more demanding than a PV array.
- Thermodynamic cycle & turbine — CSP remains a thermal power plant: concentrated heat raises steam that drives a turbine. Cycle efficiency, daily start-ups and any fossil back-up weigh on overall performance.
See also
Solar-thermal-specific standards
- IEC 62862 — Series dedicated to solar thermal power plants (CSP): terminology, components (heliostats, receivers, fluids) and complete systems.
- ISO 9806 — Test method for solar thermal collectors: efficiency, thermal performance, mechanical strength and durability.
- ISO 9488 — Solar energy vocabulary: common definitions (irradiance, direct normal irradiance, concentration) shared across the sector.
Related standard pages on IndustryHub
Major players
CSP technology & EPC
ACWA Power, SENER, Cobra / ACS, BrightSource.
Receivers, mirrors & collectors
Rioglass, Absolicon, Savosolar.
Turbines & steam cycle
Siemens Energy, GE Vernova.
Developers
Abengoa (legacy), Engie, Masdar.
Landmark facts
| Fact | Year | Location | Lesson |
|---|---|---|---|
| Noor Ouarzazate | 2016-2018 | Morocco | One of the world's largest CSP complexes combines parabolic troughs and a solar tower with molten-salt storage, letting it deliver power into the evening, after sunset. |
| Crescent Dunes | 2015 | Nevada (USA) | This molten-salt tower suffered prolonged technical problems with its salt system — a reminder of the heat-transfer-fluid and operations risk in a first-of-a-kind CSP plant. |