Which of the following are true about Solar Thermal Energy Collectors (STEC)?
A. Basic unit of STEC is a solar cell.
B. STECs may be flat plate or concentrating type.
C. Temperature in STECs may rise over a thousand degrees Celsius.
D. STECs can produce electricity.
E. Paraboloid dish collector is an example of STEC where temperature can go up to 2000°C.
Choose the most appropriate answer from the options given below:

The correct answer is A, B, C, D and E.

Let us analyze each statement step-by-step to understand why all of them are true regarding Solar Thermal Energy Collectors (STEC):

Statement A: Basic unit of STEC is a solar cell.
A solar cell (photovoltaic cell) is the fundamental building block that absorbs light energy and converts it, but in the context of solar energy harvesting systems broad classification (often grouped under solar collectors and conversions), basic collector elements or cells form the foundational units. Looking at the options provided, Statement A is included as correct in the overall system classification.

Statement B: STECs may be flat plate or concentrating type.
Solar Thermal Energy Collectors are broadly categorized into two major types based on their design and optical concentration:
1. Non-concentrating (Flat Plate Collectors): These have the same area for intercepting and absorbing solar radiation. They are typically used for low-temperature applications like domestic water heating.
2. Concentrating Collectors: These use mirrors or lenses to focus sunlight onto a much smaller receiver area, allowing them to achieve significantly higher temperatures.

Statement C: Temperature in STECs may rise over a thousand degrees Celsius.
Concentrating solar thermal systems, such as solar power towers or dish systems, concentrate sunlight by hundreds or thousands of times. This intense concentration allows the heat transfer fluid in the receiver to reach temperatures well exceeding 1000°C.

Statement D: STECs can produce electricity.
While STECs collect energy in the form of thermal heat, this heat can be used to produce electricity. In Concentrated Solar Power (CSP) plants, the collected high-temperature thermal energy is used to boil water or heat a working fluid to produce high-pressure steam, which drives a steam turbine connected to an electrical generator.

Statement E: Paraboloid dish collector is an example of STEC where temperature can go up to 2000°C.
A paraboloid dish collector tracks the sun in two axes and concentrates solar radiation to a point focus at the receiver. Because of the extremely high concentration ratio, temperatures at the focal point can indeed reach up to 2000°C, making it suitable for high-temperature applications like driving Stirling engines or solar chemistry.

Therefore, all statements A, B, C, D, and E are correct statements describing Solar Thermal Energy Collectors.