Solar Thermal Energy

Solar thermal energy (STE) is a type of energy and a technology that uses solar energy to produce thermal energy for use in industry, as well as in the residential and commercial sectors. It is a technology that uses the sun’s energy to generate heat, which can then be used for a variety of purposes. Solar thermal systems capture the sun’s heat and use it to heat water, produce steam, or power other thermal processes, as opposed to solar photovoltaic (PV) systems, which convert sunlight directly into electricity.

The United States Energy Information Administration categorises solar thermal collectors as low-, medium-, or high-temperature collectors. Unglazed low-temperature collectors are commonly used to heat swimming pools or ventilation air. Medium-temperature collectors, which are typically flat plates, are used to heat water or air for residential and commercial applications.

High-temperature collectors use mirrors or lenses to concentrate sunlight and are commonly used in industries to meet heat requirements of up to 300 deg C / 20 bar pressure and for electric power generation. Concentrated Solar Thermal (CST) for meeting heat requirements in industries, and Concentrated Solar Power (CSP) when the heat collected is used to generate electricity. In terms of application, CST and CSP are incompatible.

Application

Solar thermal energy can be used for a variety of purposes. Water heating for domestic or industrial purposes, space heating in buildings, and generating steam for electricity generation or industrial processes are all common applications. Concentrated solar power (CSP) systems in large-scale power plants use solar thermal energy to generate electricity by driving turbines with steam or other heat transfer fluids.

Here’s how solar thermal energy typically works:

Solar Collectors: Solar collectors collect sunlight and convert it to heat. These collectors are typically flat plates or evacuated tubes that absorb sunlight and convert it to thermal energy.
Heat Transfer Fluid: The heat is absorbed by a heat transfer fluid, such as water or an antifreeze solution, which circulates through the solar collectors. As the fluid passes through the collectors, it heats up.
Heat Storage or Heat Transfer: The heated fluid is either delivered to the application directly or stored in a thermal storage system. In some cases, the heat can be used right away for heating purposes, such as space heating or producing hot water. In others, it may be stored for later use in insulated tanks or other storage systems.

Advantages of Solar Thermal Energy:

Renewable and Clean: Solar thermal energy relies on the abundant and renewable power of the sun, making it a clean source of energy with no direct greenhouse gas emissions during operation.
Versatility: Solar thermal systems can be customized to meet a wide range of heating requirements, from small-scale residential applications to large industrial processes.
Energy Efficiency: Solar thermal systems can achieve high levels of energy efficiency, especially when combined with thermal storage technologies that enable heat to be used when the sun is not shining.

Limitations of Solar Thermal Energy:

Intermittent Availability: Solar thermal energy is dependent on sunlight availability, which means it is not always available at night or during cloudy weather. Thermal storage systems, on the other hand, can help to alleviate this limitation.
Space Requirements: Solar collectors, particularly in large-scale applications, require a significant amount of space to install, making them impractical in densely populated urban areas.
Initial Cost: The initial cost of installing solar thermal systems can be relatively high, but they can provide long-term energy savings over their operational lifetime.