E!113995 The project will deliver a 10kW scaled device, to exploit the turbine’s unique functionality

The aim of the project is to develop and test a simple vertical turbine to produce electrical energy in tidal currents and ocean currents. The project aims to continue the current TRL 3 laboratory tests up to a TRL 6 level through tests in a realistic environment. The project's objective is to arrive at a technology that can meet or exceed the market's expectations for cost-effective production of renewable energy. Our main goal was to make and test a small-scale (TRL6) turbine for airfoils and whether it was self-starting. The turbine has been designed, built, tested and compared with theoretical calculations/simulations. The turbine self-starts due to its helical blades and therefore requires no starter motor. The theoretical calculations show that the power potential for the model is 5 kW at normal tidal currents and can be scaled to 1 MW for real size. Our vision is a simple, minimal maintenance device with a true 25-year design life (commensurate with the marine industry in general). We will achieve this by using the Darrieus turbine layout, which is a turbine design particularly suited to marine applications. The main reason is that water carries much more kinetic energy density than air. Therefore, blade lengths in hydraulic turbines are shorter than in wind turbines, relative to the size of the central hub and generator. This means that hub losses are typically much larger in marine turbines than wind turbines. The Darrieus turbine avoids hub losses by placing the “hub” at the base of the device, away from the flow path. In a rotating Darrieus turbine, the blade angle is always changing as the blade makes progress about the central turbine axis. However, at any point in its progress, the blade angle can be optimized if the blade can rotate independently about its own axis. This is analogous to a sailboat being able extract power from the wind while travelling (almost) any direction (except directly up-wind). To accomplish independent blade angle adjustment in a Darrieus turbine with active controls (i.e., a motor at each blade attachment point) would lead to an expensive and complex turbine. Our innovation uses a passive, spring like flexibility in the blades or their joints to produce much the same effect, and a level of efficiency superior to a fixed-blade Darrieus turbine. This improves lifetime MWh captured without increasing CAPEX or OPEX risk. Hydrowatt’s capability to self-start in low flows represents a key advantage. This extends our load factor (time generating electricity) and reduces our CAPEX per MWh generated. Improvements over State of the Art We define direct competition as only tidal stream devices and furthermore only fully submerged, deep-sea tidal stream devices. These are turbines and other devices that extract kinetic energy directly from ocean currents including tidal currents. Our design uses a vertical axis Darrieus turbine, in which there is no central hub, and the generator is located at the base, away from the path of fluid flow. While the Darrieus turbine offers marginal advantages in wind applications, the large hub losses associated with hydraulic turbines make the benefits of the Darrieus turbine very substantial in marine applications. Most importantly, our design is quite simple, with no gear box, no active blade pitch control, and no yaw control.

After having completed the test, we have three main take outs: 1. The turbine as it is designed have excellent capabilities of self-starting. It started at water velocity as low as 0,2 meter/second. 2. We where able to produce energy in the equivalent of 7 kW/h at a speed of 1 meter/second. This is slightly over our expectations and give great motivation to further develop the technology. 3. We did see some turbulences and flow behavior that leads us to believe that there are room for further development of the technology. Known and published data for calculating turbines in slow moving water are not common. Most data refer to air as the medium. We have learned that data from air simulations cannot be directly transferred on to our situation with water at low velocity.

The goal of this project is to research and develop a novel vertical-axis tidal stream power generation device based on our TRL3 laboratory proof of concept, achieving a TRL-6 prototype characterised through performance trials in an ocean environment. We will use our expertise in the North Sea oil & gas industry to deliver a 25-year maintenance-free design life, making this device a gateway to our planned next step, a 30kW (1st generation) commercial device. To reduce maintenance, the turbine will use a simple yet innovative Darrieus design with a single moving part and one external seal. (See Annex.) This will provide a direct drive to a generator featuring a patented non-contact magnetic gearbox, further reducing complexity. To offer competitive performance and self-starting capability versus more complex turbines, this device will feature highly innovative flexing blades capable of passively changing the angle of attack to maximise energy extraction through a range of flow conditions. The main result of the project will be a 5kW demonstrator device tested and validated in the marine environment. Accelerated life testing and operational data will validate a maintenance free design life of 25 years (95th percentile), similar to successful sub-sea devices for the oil and gas industry. The demonstrator data will provide input to a revised business plan, based around three alternative business models designed to maximise the commercial opportunity. The results of this project will build on patents and our proof-of-concept device. We will generate new knowledge in the areas of flexible blade design. The choice of optimal blade flex, the implementation (materials and geometry), generator geometry and torque/speed characteristics will be researched. The result will be a turbine that can match or exceed the cost-efficiency of existing, more complex, turbines, but with a world-leading 25-year service life and maintenance/downtime costs 90% lower than for competitors.