The Archimedes screw was invented in 200 AD by Archimedes and was used to pump water up to irrigate fields. It has been used to drain lowlands in the Netherlands and in modern times as part of sewage systems to pump sewer effluent. It has only been a recent development that the screw has been applied to power generation.
Type of generator
Induction (asynchronous) generator – to generate single or 3 phase AC electricity.
The generator is excited by the existing grid, the frequency automatically matches the existing grid with no need for inverters. The generator’s have a brake that is activated by the grid, if the grid power goes out the brake comes on and at the same time the 3 phase motor loses excitation and stops generating power. We have chosen this type of generation because of availability of mass produced, relatively inexpensive, reliable and available gear motors to be used as generators.
The weight of the water falling through the screw turns the screw which turns the gear box and generator and produces electricity as it turns. The diameter of the screw increases as the design flow increases. The length of the screw increases as the “head” or vertical drop increases.
Watch this video for an overview of the technology via a tour of our small test site. This small site has all the main features of a large one but in a small package so you get a clear idea of how things work.
Operating Envelope Diagram
The diagram to the left shows the operating ranges for the Archimedes screw in comparison with other types of turbines in terms of head and flow rate.
Within its operating range, the Archimedes screw is unmatched in terms of;
- -ease of maintenance
- -performance under non ideal head and flow conditions
- -fish and environmental friendliness
GreenBug Energy offers Grid-Tied screw generators from 1/2 kw to 300kw in size, for grid environments of 50 or 60 Hz and for either 3 phase or single phase connections.
GreenBug also offers 3 models of screw generators for effective operating environments.
GreenBug’s Grid-Tied Screw Generators -Custom Designed to maximize your return
Our grid-tied induction generators are custom designed for each site based on the head and flow duration data in order to maximize the IRR (Internal Rate of Return) on the project. This fine tuned custom approach is the key to maximizing IRR and making micro hydro viable.
The head and flow duration data for a site in combination with system cost and design information determines the optimal screw generator specifications.
If you have already determined the optimal design head and maximum capacity design flow for your site we can supply a custom designed screw generator to match those specifications.
Net Metering vs FIT
For a detailed discussion on the pros and cons of “Net Metering” versus “Feed in Tariff” (FIT) connection.