Hydrokinetic turbines operate from underwater currents, whether from rivers or tides. We applied computational fluid dynamic technologies to underwater river and tidal turbines. The result was a turbine based on two synergistic patents, one on shroud shapes and the other on blade shapes. Together, they are capable of revolutionizing the industry by making turbines produce 50-250% more power. This large improvement is possible because we in effect concentrate the energy in the flow of water in two axes simultaneously, thereby making its velocity faster in the plane of the blades. The US Navy validated the 50% figure through simulations on one specific design of 10 meter blades. We intend to make versions of many sizes for different rivers and tides. First demonstration project is tentatively scheduled for November 2014 in a river in Massachusetts.
More Detailed Information
- Two synergistic patents on shrouds and blades result in underwater turbines (for run of river, tidal, and ocean currents) much more effective than those on the market. This can revolutionize the field and provide a large portion of the world’s energy.
- It addresses the cost of electricity since water is the lowest cost renewable when done correctly. It makes renewable energy available in the many locations in the world that are near rivers, such as cities, so that the renewable energy can be harnessed locally.
STATE OF THE ART
- Most underwater turbines today are simply propellers. This is good, but it can be better. Some systems have huge shrouds that are unwieldy or concentrate the enhanced flow on the nacelle in the middle, where it is worthless, and it extends along the length of the turbine.
- Simulations already performed, both by the US Navy and by us, show a large enhancement effect: with 10-meter blade turbines, 50% more power. This is more effective than increasing blade diameter. A simple understanding of the technology explains why it is better than increasing the size of the blades. A typical funnel results in a central zone of increased flow speed extending over the length of the funnel. The new, patented shroud shapes are relatively small, but are highly effective unique shapes that concentrate the flow both radially and in the direction of flow into the plane of the blades at the tips, where it can be harnessed much better. This process is much more effective at short ranges, and we expect improvements of 100-200% for turbines of several meters in diameter. This is combined with a patent-pending unique blade design that takes advantage of that altered flow.
- Shrouded underwater turbines have been tried before, but they are very large relative to the size of the propellers because the thinking behind them is wrong; for maximal effect, the flow has to be compressed in two dimensions—one radial, and one horizontal.
- PVR technology would lead to turbines that start at lower speed and produce much more power per unit size than current ones. Here is a comparative table of the effect of a few sizes in meters of blade diameter at a few flow speeds of meters per second on power in kilowatts. Note that our lower cut-in speed will change the economics of placing turbines and expand the market. In the table, “Brand X” refers to standard propellers alone.
There is another way in which this would advance the state of the art. The shroud offers an opportunity to suspend a mesh and protect fish, so it can overcome one of the major regulatory barriers. Below: A photo of early-stage prototype. Middle: A simulation performed by the US Navy, showing flow from left to right at 1 meter per second. As it enters the space perpendicular to the foil, its average becomes 1.3 m/s. The red, highest velocity zone of 2 m/s is the most important to capture with the blades in the correct plane perpendicular to the flow. The graph shows the percentage increase in power compared to a simple propeller system on the y axis and the relative position of shroud to blades on the x axis in meters. Look at the black line. In a shift of shroud position of less than 20 centimeters, the percentage increase falls from over 200% to 50%.