Solarthermal

Solarthermal, or solar thermal energy, refers to technologies that convert sunlight into heat rather than electricity. Collectors absorb solar radiation and transfer heat to a working fluid, which can be water, oil, or molten salt. The heated fluid is used directly for heating or to generate steam for power generation or industrial processes. Solarthermal systems are distinct from solar photovoltaics, which convert light to electricity.

There are two broad categories: non-concentrating solar thermal collectors and concentrating solar thermal (CST) systems. Non-concentrating collectors, such as flat-plate and evacuated-tube collectors, are commonly used for domestic hot water and space heating. Concentrating solar thermal systems use mirrors or lenses to focus sunlight on a small absorber, achieving higher temperatures and enabling electricity generation and high-temperature industrial heat.

Storage and integration: Thermal energy can be stored in sensible forms (for example, water or molten salt) or in latent forms with phase-change materials. This storage supports dispatchable operation, allowing CST plants to deliver power when solar input is insufficient and to smooth supply in hybrid systems.

Components and operation: A solar thermal system typically includes collectors, a heat transfer fluid loop, a heat exchanger, thermal storage, and equipment to supply heated water or generate steam for a turbine. Controls manage heat collection, storage, and usage.

Advantages and challenges: Solarthermal can provide low-emission heat and, with storage, dispatchable power. Challenges include water use for cooling in some designs, land requirements, upfront costs, and competition with other energy sources in different regions.