Perth man invents new tidal energy harvester

Energy Harvester
Image: Doug English

Perth man Doug English has shared his invention, the Energy Harvester, a patented technology for harvesting energy from an ocean current as an alternative for the propeller or turbine.

Doug is a veteran of the manufacturing industry, spending his first 20 years working for components suppliers to the motor industry. Arriving in Australia as a skilled migrant from South Africa in 2007, he worked for Austal Ships before starting Doug’s Engineering nine years ago.

Watch the video below to see the Energy Harvester in action and read Doug’s introduction afterwards.

From the inventor

Doug English

To start off, I believe it is important for me to explain the thinking of what motivated me to develop the Energy Harvester in the renewable space. The thinking behind it is as an important a representation as the attached video as the Energy Harvester has not yet been built in all versions or embodiments that it could be.

My goal was to try to find a way to harness the torque that is generated by, for example, the sail of a yacht to find an alternative to the propeller for harvesting energy from a fluid flow. The aim was to turn this harvested kinetic energy into a rotational force to drive a crank shaft. Once this was achieved then most commonly used technologies such as generators, pumps, etc. would be able to be attached to the crank shaft to make use of the energy supply.

The challenge for developing a mechanism with a sail/fin attached to the end of a shaft is, once it has exhausted its travel, how to get it to change and reverse its direction in a way so as to impede the flow of the fluid and to complete a revolution. To achieve this I have designed a robust and accurate indexing mechanism.

The camming system that I have designed, that is employed in my patented invention, allows for the accurate control of the angle of attack of the sail/fin to best impede the fluid flow at any given time during the 360-degree rotation of the crank shaft. This is the key feature that makes the design practical and has been recognised by the patent authority as inventive. This feature will mean that engineers who desire to employ this technology in the future will be able to tailor the working of the machine in the best possible way to maximise the benefits of the fluid flow at their disposal.

The above video of the Energy Harvester is a representation of a machine where the crank shaft lies in the horizontal plane and the sails/fins move up and down in the vertical plane. This test machine was manufactured by myself to prove that the technology does work in a water flow/current. It has very small fins as the only goal was to make sure that the mechanism worked as I had envisaged. It does not represent the exact proportions of a machine that could be built to extract the maximum energy out of a fluid flow.


  • Reduced superstructure. The sails/fins are arranged that the forces are reciprocating, therefore negating the need for a large superstructure to handle the differential loads of current propeller machines.
  • Reciprocating forces allow for large single units to be constructed.
  • This is a simple technology that can be deployed in developing nations where a large proportion of the world’s population lives. The current commonly adopted technologies of solar and wind turbines used for electricity generation are both high tech disciplines. One only needs to look at the market leaders in these fields and you will quickly notice that the people building the grid scale machinery are large, multinational, engineering giants. The sophistication of photovoltaic solar panels and the complexity of wind turbines means that the manufacture of this equipment is the domain of companies with enormous budgets and highly sophisticated aircraft level manufacturing facilities. The technology employed in the Energy Harvester is of a much lower level. The skill level required is more universally common. A person who has the skill level to build a semi-truck trailer or manufacture lawn mowers or motor industry components would be well equipped to manufacture the energy harvester for small-scale application.
  • Crank shaft lies above the water. This has a large benefit for practical deployment as working parts and generators can be kept in an enclosed dry area out of the water. This type of machine would be particularly applicable to a run of river hydro type application. There is large scope for this type of machine in countries such as Canada with fast flowing rivers/canals and powerful tidal current.
  • Able to be used in fluctuating water depths from shallow to very deep. The machine in the video is fitted with skids and wheels so should the water level in the river recede it could just sit on the floor of the river and continue working, even if the water level receded below the top workings of the fin’s travel. When the river water rises again the machine would merely float on the pontoons.
  • Most embodiments of these machines only require anchoring. In areas where the fluid flow is close to dry land, like rivers or tidal systems or current flows between island passages, the machine could be moored and anchored to dry land thus negating the necessity for sub-sea works. Such currents exist between Bali and Lombok and between some of the Solomon Islands.

I am very excited about the possibilities of the Energy Harvester and am keen to dialogue with interested parties.

More to come.