Not much has changed in basic screw design, and they are essentially the same as they were in ancient times. Originally, Archimedes screws were composed of wood, but gradually wood was replaced by metal. Current screws are exclusively made of metal. Typically, Archimedes screws are encased in a box covering so as to prevent splash out or loss of material, but some, such as those used in sewage treatment, are designed in a way that makes this unnecessary. 

As stated, the standard design of an Archimedes screw resembles a very large screw, an inclined plane wrapped around a cylinder, which rotates, sending material or liquid “up” (sometimes these screws are positioned horizontally) along the threads. The variations in design present some of the crucial differences in the Archimedes screw. These include:

• Rotation comprises the speed at which the drill turns. A faster speed means the transported material moves along the screw faster, but for heavier or more viscous items, a slower motion might be required to prevent damage. For instance, in an irrigation screw, too fast a rotation could lead to flooding.

• Extention refers to the length of the screw. The length can change the way the screw operates because a shorter screw will transfer material a short distance quicker, but like rotation speed, it can cause flooding problems. Also, if a screw is being used for sorting, there will be less time to perform the separation.

• Pitch refers to the angle of the threads. These angles need to be more acute or obtuse depending on the material being delivered. Liquids require a higher angle in order to fully capture the substance and ensure it does not fall out. Also, a deeper thread can contain more material.

• Plot Range refers to the overall transference of material in the screw. If a screw has only one range, it refers to one thread, but two threads can operate at once around the same shaft to increase deliverance.

Archimedes Screws Turbines and Hydropower

Archimedes Screws Turbines (ASTs) are a new form of turbines for small hydroelectric powerplants that could be applied even in low head sites. ASTs offer a clean and renewable source of energy. They are safer for wildlife and especially fish. The low rotation speed of ASTs reduces negative impacts on aquatic life and fish.

The structural simplicity, low operational demands, and modest costs make ASTs an environment-friendly and sustainable solution, especially in developing countries to generate power 

Archimedes Screw Turbines (ASTs) provide a range of practical advantages for generating electrical energy. For supporting sustainable development, ASTs offer economic, social, and environmental advantages. Considering the flexibility and advantages of ASTs, they could be considered as one of the most practical options for a more sustainable electricity generation:

1. To increase the number of suitable sites for power generation even in sites with very low flow rates and/or water head. ASTs can be designed to operate in a wide range of flow rates (currently from 0.01–10 m3/s) and water heads (currently from 0.1–10 m), including at sites where other types of turbines may not be feasible. This increases the number of potentially suitable sites for hydropower.

2. To maximize hydropower generation even in rivers with high flow rate fluctuations. ASTs can handle flow rates even of up to 20% more than optimal filling without a significant loss in efficiency [63]. Even when the conditions are not perfect for a single screw, installing more than one screw, and utilizing variable-speed ASTs, allows developers to fully utilize available flow at a wider range of sites, including those with high seasonal variability.

3. To retrofit old dams or upgrade current dams or mills to make them economically (power generation) and environmentally (renewable energy) reasonable. Using ASTs as an upgrade for retrofitting old dams or upgrading operational dams makes it possible to add electrical generation with extremely low incremental environmental impact, at reasonable costs and with good potential for low social impacts while providing an incentive to maintain aging dams and infrastructure. ASTs utilized in this manner could help to reduce fossil fuel usage and greenhouse gas emissions by displacing electricity generated by more polluting methods.

4. To reduce the hydroelectricity major operational and/or maintenance costs: In addition to retrofit/upgrade current dams advantages, at appropriate sites, the capital costs of AST hydropower can be less than other hydropower technologies. The overall maintenance demands and costs of ASTs are often lower than other turbines. Major maintenance is required after the 20 to 30 years.

5. To reduce the disturbance of natural erosion and sedimentation processes which could lead to soil and land conservation.

6. To make hydropower generation safer for aquatic wildlife, especially for fish.

7. To generate electricity for small communities or regions that are hard to access or connect to the power grid, especially because of the low operation and maintenance demands and costs of ASTs. These characteristics make ASTs a potential candidate for providing electrical power in undeveloped, remote regions, and small communities that currently lack energy infrastructure.

8. To improve the welfare of the developing countries and regions with limited access to the power grid or other infrastructures. Despite many other technologies, ASTs do not require high manufacturing capabilities and hi-tech technologies to design, implement, operate, or maintain. Simplicity, low operational demands, and moderate costs make ASTs a practical environment-friendly and sustainable solution for supplying energy, especially in developing countries. At remote locations with a low head water supply, ASTs may provide a possible means of providing electricity that would otherwise be impractical in developing communities. Improving the economy and welfare of such communities is a win-win futuristic sustainable development approach that could be facilitated by using AST hydroelectric plants.