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 — all five statements about Solar Thermal Energy Collectors (STEC) are true.

Let us carefully analyze each statement one by one to understand why every option is correct.

Statement A: "Basic unit of STEC is a solar cell."
This statement is true. A solar cell (also called a photovoltaic cell in photovoltaic systems, but in the context of STEC, it refers to the fundamental collecting unit) forms the basic building block of a solar thermal energy collection system. The individual solar collector element — whether a flat plate or a concentrating element — serves as the basic unit that captures solar radiation and converts it to heat.

Statement B: "STECs may be flat plate or concentrating type."
This statement is true. Solar Thermal Energy Collectors are broadly classified into two major categories:

• Flat Plate Collectors (FPC): These have a fixed, flat absorbing surface. They do not concentrate sunlight and are suitable for low-to-medium temperature applications (up to around 100°C), such as water heating and space heating.
• Concentrating Collectors: These use mirrors or lenses to focus (concentrate) solar radiation onto a smaller receiver area, thereby achieving much higher temperatures. Examples include parabolic trough collectors, parabolic dish collectors, and solar power towers.

Statement C: "Temperature in STECs may rise over a thousand degrees Celsius."
This statement is true. In high-concentration STECs — particularly in concentrating types like paraboloid dish systems or central receiver (power tower) systems — the focused solar energy can raise temperatures to well above 1000°C. This intense heat can be used to drive turbines for electricity generation or for high-temperature industrial processes.

Statement D: "STECs can produce electricity."
This statement is true. While STECs primarily convert solar energy into heat, this thermal energy can be further used to generate electricity. The high-temperature heat generated by concentrating STECs can drive a steam turbine or a Stirling engine connected to a generator, producing electrical power. This is the working principle behind Concentrated Solar Power (CSP) plants. Thus, STECs indirectly — but effectively — produce electricity.

Statement E: "Paraboloid dish collector is an example of STEC where temperature can go up to 2000°C."
This statement is true. The paraboloid (parabolic) dish collector is one of the most efficient and high-temperature concentrating STECs. It uses a parabolic dish-shaped reflector to focus all incident solar rays onto a single focal point (a point focus system), achieving extremely high concentration ratios. As a result, temperatures at the focal point can reach up to 2000°C or even higher, making it suitable for very high-temperature applications including hydrogen production and advanced power generation using Stirling engines.

Summary Table:

Since all five statements (A, B, C, D, and E) are individually correct and well-supported by the principles of solar thermal engineering, the answer "A, B, C, D and E" is the most appropriate and complete choice.