Basic Concept

The concept of ASC provides a solution for the technical problems that commercially existing concentrators are facing. Basically, it is a lens-like, metallic point concentrator which concentrates solar radiation to a lower focal area fixed to the ground.

For the last decade the reflective concentrators used in CSP and CSH systems are based on four types of concepts to concentrate Sun rays shown in the illustration here. In principle, the concentrator purpose is to reflect the solar rays such that they are concentrated on a focal area smaller than that of gross area of the concentrator (aperture area) resulting in high temperature and solar flux. The ratio between the focal receiving area and the aperture area is called the concentration ration. Higher the concentration ratio results in higher receiver temperature. To understand the concept of ASC we will briefly explain the characteristics and the problems facing the existing concentrators.

Linear Solar Concentrators

These are concentrators which concentrate solar radiation to a focal line. The most famous and mature type is the parabolic Trough while the other type is the Linear Fresnel Concentrator (LFC). Generally, for the commercial systems, the concentration ratio of such linear systems is below 80 resulting in temperatures around 450 C. Such temperatures are suitable to generate steam for industrial purposes or to power a steam turbine power plant. ASC can have concentration ratio of more than six thousand and generate temperatures more than 1,000C.

Point Solar Concentrator

These are concentrator which concentrate the solar radiation to a focal point. These have higher concentration ratio than linear concentrators and hence a higher receiver temperature. Two types of commercial Point Solar Concentrators currently exist as follow:

The Heliostat Tower System (Power Tower)

This is the rising star of CSP and is usage is increasing in many projects. Its main advantage that it has a higher concertation ratio of around few hundreds resulting in higher temperatures. Commercially, the temperatures generated are around 600C although it can reach a 1000 C for non-commercial experimental applications. Such high temperatures allow for good thermal storage like molten salt stored at 550C. However, the Heliostat-Tower system has the following issues:

  1. It has low optical efficiency and uses large areas compared to other types of CSPs. For large scale Heliostat systems only 40% of average solar radiation falling on the total area of the heliostats can be concentrated on the receiver, (theoretically),  while for small scale systems 60% ratio can be obtained. For ASC this ratio reaches 100% .
  2. The system is central system and feasible for large scale projects. For modular distributed projects the system is not financially feasible. For ASC the concentrator can produce modular small to medium CSP systems with storage at feasible cost.
  3. The Receiver is placed high on the top of long towers, in some cases 130m above ground. This makes maintenance and installation a big challenge. For ASC the receiver is placed near the ground and is fixed on having easy access for maintenance and no challenge of installation.

Parabolic Dish Solar Concentrator

In this system a parabolic dish is used to concentrate the solar radiation to its focal point. The dish tracks the Sun to be directly facing it concentrating the solar radiation to its focal point which is moving in space as the sun moves in the sky.

SOLAR DUAL AXIS TRACKING

A very high concentration ratio can be achieved by the parabolic dish resulting in very high temperatures at the focal point. Such temperatures can power a Stirling Engine placed at the focal point (Stirling Dish Systems). The parabolic Dish has a very good optical efficiency since it reflects 100% of the solar radiation it receives to the focal point. However, the Parabolic Dish Concentrator has the following issues:

  1. Its focal point is moving in space as the dish tracks the Sun. This poses great challenges on transferring high temperatures and high-pressure fluids through flexible pipes or rotational joints (Swivel Joins). Moreover, large bulky systems (like gas turbines, thermochemical reactors or metal smelters) cannot be placed at the continuously moving focal point. This limits the application of the parabolic dish to application like a Light Weight Small Stirling Engines without storage or to steam generation moderate temperatures (200C-300C). For the ASC the focal point is fixed on the ground opening the door for many applications as seen here.
  2. The Parabolic Dish has a very high wind facing solid cross section resulting in a very high wind load. This demand a very strong structure made of special materials which affect the cost. For the ASC its design is such that wind can flow through it allowing much lower wind load and requiring lower cost structure.
  3. The parabolic dish requires high accuracy mirrors manufacturing to produce the needed accuracy to concentrate solar radiation to the focal point. Such technology of 3-D bending of mirrors is specialized and not highly spread. For the ASC the reflectors are manufactured with low-tech 2-D cutting and metal shaping which is available nearly everywhere.

The basic concept of the ASC (Ayman Solar Concentrator) that it is a lens-like, metallic point concentrator which concentrates solar radiation to a lower focal area fixed to the ground. It has a low wind load, easy to manufacture, with a wide range of Applications as seen here. For more details please contact us.

Scroll to Top