First slow-current turbines in the world to enter sea trial
In July 26th 2013 Valorka became the first turbine developer in the world to test tidal turbines in the sea; intended for use in currents of less than 1 m/sec in velocity. The significance of this event becomes apparent when kept in mind that such slow currents are much more common worldwide than the faster flowing currents for which most other tidal-turbine developers are competing. The slower currents, widely found by capes and shallows all around the world, do however not posess the same energy concentration, and that means that Valorka must keep its turbines more effective, yet simpler and cheaper, than other tidal turbines. We have already solved many of the problems involved, and we have the solutions to solve the rest of them.
Modernizing an ancient invention
The fundamental function of the Valorka turbines is similar to that of an invention more than 2300 years old; the traditional waterwheel. The waterwheel is a convenient way to capture energy from slow currents, because the blades can be made very big to take on maximum pressure of the stream. The challenge was how to get the waterwheel to operate submerged in a stream of water. In order to do that the old waterwheel needed to undergo the most dramatc changes from its earliest invention. Valorka has found, not one, but several solutions to the problem; put them to tests and developed them. At the present Valorka is in the forefront of this technology.
The Valorka turbines are different from the propeller type turbines, most commonly being developed. Valorka aims for capturing energy from currents of less velocity than 2 m/sec, even less than 1 m/sec, which means that the turbines may be used in wide areas outside the coasts all over the world.
Many different turbine types
V-1 is the original Valorka turbine. Here, the solution is to make the sides of the wheel conical in shape; split the axis in two and split each shovel in two parts. Then one wheel-half can be folded towards the other in such a way that each shovel folds completely together at one part of the wheel, but opens fully at the opposite part. In this way the turbine´s resistance to the current will be more on one half of the wheel than the other.
V-2 is an improvement of V-1. The conical sides have been replaced by pins. This means that the blades can extend into the „cones“, increasing the surface and resulting in more torque. This also means simpler design; improved stability of the blades and spimplicity in construction. A patent was granted, which included both V-1 and V-2. It also included a novel shifting mechanism, which makes it possible for the turbine to operate in shifting tidal currents; while the direction of rotation remains unchanged.
V-3 is based on a different approach, but still bears a resemblance to the old waterwheel. Basically it consists of one single wheelside, with shovels hinged on each side of it. The shape of the shovels allows the current to open them at one position and shut them closed at the opposite position. The advantage compared to V-1 and V-2 is that many V-3 turbines can be combined on a single straight shaft, using a common generator. This makes the whole unit much more economical and effective.
V-4 is yet another completely different solution. The V-4 has no wheelsides at all. Through the axle go free-spinning pins on which the blades are mounted in pairs; in the way that when the current hits one blade flat-on, it hits the opposite blade edge-on at the same time. The resulting difference in resistance makes the turbine turn, and at the same time the current causes the blades to shift their position. In reversed current the blades are flat-on at the opposite side, but the spinning direction of the turbine stays the same.
V-5 is the latest type. This is a direct derivative of the former types, but even simpler and proved to be more effective in tub-tests. This was the type selected for the first sea trials. As the others, this turbine is fundamentally a waterwheel with its main axis at 90° to the current. The one shown has 10 blades which are hinged on pins so they can be in open position; flat against the current, or closed position, with the edge towards the current. The blades´ pins are fixed at slightly less than 90° to the axis, causing the blade to open when the blade approaches the upstream-position. When in open position, it gets pushed back until downstream, where it is turned to the edge-on position by the current pushing on its backside. This repeaded action causes the turbine to spin and deliver energy. When the tide turns, the blades open on the opposite half of the axis, but the spinning direction remains the same. Arranged on a straight axis, many turbines can use a common generator. Technology already exists for submerged generators, cables and other parts needed.
The WATT-hybrid: Wave Assisted Tidal Turbine
Older than the first Valorka turbine is Valdimar´s invention of a Wave Energy Convertor. Based on the long tradition of fishing in the rough seas of Icelandic waters, this WEC is able to withstand gale forces better than previous devices. When first presented, the ideas did not get sufficient finance and were put to rest. Recently they emerged again, as a solution has been found to making the WEC a part of the Valorka tidal turbine. This solution is a coupling mechanism which transfers the pull of buys on the surface to a special gearing device on the turbine´s axis; enhancing the power output of the combined unit. Valorka started developing this invention in january 2014. To date, no such hybrid has entered sea trials, and Valorka intends to be in the lead of this technology. This hybrid has the approriate name WATT; Wave Assisted Tidal Technology. It may not apply at all places, since many of the energy-rich races by capes are also in the route for ship-traffic. But where applicable, it will make the Valorka turbines even more practical for ocean energy production.
From tub to sea trials
All Valorka turbines have been tested in a tub as a Ø50cm scale models in a tub. In 2013, a bigger scale model of V-5 began sea trials in the Hornafjordur Estuary. It is tested in a floating test-raft; purpose-built by Valorka. This is the first test of ocean energy technology in Iceland and the first turbine ever invented in iceland.
Tidal turbine farms – no environmental hazard
Valorka is developing methods for installing the turbines and servicing them. The turbines will probably sit in mid-depth on poles, rising from the bottom; tethered for stability. Each energy-production site will probably consist of several turbines, connected to a common hub with electricity being fed ashore by a submerged cable. The spinning of the turbine is very slow, so wildlife will not be harmed. Sea traffic will not be hindered because the powerplant is totally submerged. In fact the turbines seem to have no environmental effects, making them the greenest possible way to harness energy. The idle time between the shifting of tides can easily be compensated for by many methods,for example by grid-connection of many turbines at different locations, using the different time of tides from one place to another.
Still more novelties are on Valorka´s drawing board, such as a suitable genertor for slow turbines of this kind; a combined wave- and tidal energy device; methods to lay out and service the turbines and more.
Different approach – added value – protection of environment
The primary goals of the Valorka turbines design are „efficiency, simplicity and rugged design“. This kind of turbines, sometimes referred to as „crossflow turbines“, is more suitable to harness tidal energy from relatively slow flowing currents than most of the turbine types now in development. Those are of the „axial flow“ type; many of them resembling the wind turbines used on land. Axial flow turbines need currents in excess of 2,5 m/sec to work effectively. The Valorka turbine is expected to work effectively at 1 m/sec and even slower currents. The energy in currents to the velocity by the power of 3, and thus turbines in slower currents will not deliver the same power each as axial turbines. But this can be compensated for by cheaper turbines and the electrical interconnection of turbines; turbine farms. Their greatest advance is that they can be used in variety of places by the world´s coasts, while the fast-flowing current is limited to relatively few channels. The Valorka turbines do not have to be as rugged as the others and they will be cheaper in production. That means that the turbine will be accessible by poorer nations, which then can use their own energy resources and reduce their dependance on polluting oil and coal. It will also benefit many rural districts, which need long and fragile powerlines, but then may be able to use the tidal energy by their coasts. The Valorka turbine will thus be a great step forward in many aspects, opening new possibilities in energy production; more equal access to energy and energy safety.
The Valorka turbine is expected to be fully submerged; safe from the surface turbulance which may be very destructive. This also prevents hazards for ships. The Valorka turbine is probably the only way to harness energy without any known environmental risk. No air pollution; no chemical pollution; no visual pollution; no sound pollution; no radiation; no sacrifice of precious land. Sceptics may point out that tidal currents are not a coninuous source of energy, as they stop and change direction up to four times a day, depending on situation. This is true, but this can easily be compensated for by various means. One is to connect turbines at various places along the coast; using the time difference in daily tides; other is to use other sources of energy to compensate, for example wind or hydro; the third method may be to use tidal energy to produce another form of energy, such as hot water or hydrogen. We may have to adopt new procedures to make use of tidal energy, but the benefits are obvious. Tidal energy is not only the most environmentally friendly, but the most predictable form of energy found on Earth. For each place we can predict the available energy hundreds and thousands of years into the future. Tidal energy is our future energy source.