Figure 1. Solar Hydrodinamic WIG. This type of ship can reach speeds of 200 to 230 km/h compared to the 80 to 100 km/h maximum speed that current high-speed ships can reach.
Hydrodinamic WIG or Naval Vehicle in Ground Effect Propelled totally or partially to Solar Energy
In order for a boat to run on solar energy, it needs a surface to capture the sun's energy several times larger than the size of its hull, for this it is necessary to put an additional structure to increase the surface of solar energy collection and where to place the photovoltaic solar panels to generate the electrical energy necessary for the operation of the boat, both for its propulsion systems and for the energy consumption of the different equipment that carries it.
In the case of boats that need to navigate at high speed, a system that may be suitable to expand the surface of solar energy collection is a system of folding wings on both sides of its main hull. Where said structure will also have floats on its sides to support the weight of said solar panel carrier structure when it is deployed and extended.
This folding wing system can be deployed and folded to increase and decrease its size as needed by means of hydraulic cylinders placed inside the wings and on the sides of the ship's hull. When said structure is extended, it may increase the area exposed to the sun and generate the electrical energy necessary for the operation of the ship and when it has to be moored or anchored in a port, this wing system will be folded to decrease the surface occupied by the ship in its place of anchorage or mooring.
Figure 2. The hulls you may have will be like those used by today's high-speed boats such as gliding hulls, catamarans or hulls with hydrofoils. In addition the WIG may carry a structure of vertical solar panels to take advantage of the solar energy reflected in the water but with a rigid shape and a limited height so as not to affect its stability and its resistance to high-speed advance.
To reduce the energy consumption of the ship when sailing at high speed it may be convenient that the structure that is deployed to be able to capture more solar energy, also has the shape of the wing of an aircraft, since when this boat sails at high speed , on the wings of the ship will appear a lifting force that will tend to raise the hull of the ship and decrease the contact of the water with its surface.
As the kinematic viscosity and the density of the water is greater than that of the air, at high speed, the force of resistance to the advance produced by the water on the hull of the boat will be greater than the force produced by the air on the wings of this boat, therefore, it is better that this boat when sailing at high speed has the least possible contact and friction with the water.
In addition, when the wings of an airplane travel on a flat surface at a very low height (between 0,3 and 3 meters), an overpressure of the air appears under the wings of the plane that increases its lift force and decreases its consumption between 35 and 50% compared to when the plane travels at a conventional height. This effect is used by the Ekranoplans or current ground effect vehicles, but in them both their propellant systems and the parts that form it never touch or are submerged in the water, that is, said Ekranoplans can take off and land from land tracks or from the water but when they travel none of its parts is in contact with the water or with another type of surface and they function as if it were a plane in flush flight.
In our case, both the propellant systems and the side floats may be totally or partially submerged or in contact with the water in order to improve the thrust force of the propulsion system or the stability of the vessel when operating at high speed. For this reason I think it is convenient to differentiate the name of this type of boats that I call as Ekranoships with respect to the current Ekranoplans that as we said when they sail, none of their parts are in contact with water.
Although the force of resistance to the advance on the engines and the propulsion system that will be submerged at all times in the water will be greater than if they were in the air, when this boat moves both at low and high speed the their thrust force on water will be greater than if they are made on air.
In the case of the stability of the boat, if part of the side floats are in contact or partially submerged in the water, or have hydrofoils or water propellers at the bottom, the stability of this boat at high speed will be better that if these wings were always in the air, and therefore, wings can be used without so many aerodynamic characteristics that allow it to give a greater surface area of solar energy capture to increase the solar energy generated by this vessel.
Efficiency of solar panels
At this time the maximum efficiency of commercial solar panels is in the order of 20 to 21% although there are space-use solar cells that would be very expensive to use in this type of ships with efficiencies of the order of 35 to 40% . The maximum efficiency that a multijuncture or tandem solar cell could have is 68,2% and solar cells of silicon quantum dots are currently being developed in laboratories with the potential to reach efficiencies of the order of 40-50% in the coming years, therefore for the calculations and estimates of the consumption that we will carry out in this article we will consider 50% efficient solar panels which is an efficiency that solar panels may have in the not too distant future.
Laboratories around the world are working on new types of solar cells, how the called Phonovoltaic Solar Cell that have the theoretical potential to reach efficiencies close to the Carnot Limit of 95%. So, it can be expected that at some point 50% efficiency will be reached, if not exceeded.
Therefore, for the calculations in this article, we will consider solar panels with an efficiency of 50%.
Figure 3. For long-distance and high-speed uses, the joint use of underwater propellers and air propellers may significantly improve the overall propulsion efficiency of the vessel.
Propulsion and operation systems at different speeds
In this type of boat the most advisable is that its propulsion system is formed by electric motors since they have a smaller size than internal combustion engines and also they can work submerged in water and be placed next to the thrusters let them be used. As propellant elements, the most convenient thing is to use high speed propellers, supercavitant propellers or high efficiency water jet systems, which are the propulsion systems used in today's high speed ships.
In general, the consumption of the vessel will increase with the weight of the cargo transported and the speed of the vessel, therefore this vessel may have two main forms of operation one at low speed, where 100% of its energy consumption may be supplied by its own solar panels, reaching speeds of approximately 30 km/h. And another running at high speed where the wing shapes of the solar panel carrier structure and the ground effect that will occur below them will allow it to operate with a marked lower energy consumption and also reach higher cruising speeds than the ships of Current high speed.
Also in its high-speed operation, although the total consumption of the vessel depends on the total weight of the vessel and the weight of the cargo transported, it is most likely that it cannot function only with the energy supplied by the solar panels but needs an auxiliary electrical energy, which may be delivered by a system of electric accumulators that are recharged with recharging systems external to the vessel at the docks or at the anchorage locations thereof.
In the event that this boat is used to transport loads or people over long distances and at high speeds, it may be convenient to use water propellers together with air propelled, open or standard or wrapped or guided flow propellers, since the water propellants when they must work medium or high speeds begin to lose propulsion efficiency due to the increase in efficiency losses due to cavitation.
In this case, the joint use of underwater propellers with the air propellers will improve the overall efficiency of this vessel when sailing at high speeds and the underwater thrusters will give it greater thrust when the vessel sails at low speeds or when it has that navigating in areas of winds and intermediate waves, where the boat begins to destabilize and the thrusters under water improve both stability and propulsion force at that time.
Figure 4. The width of the wings and their size can be adjusted to each application. The side floats also serve to bag the air under the wings and increase the ground effect.
Although commercial solar panels currently have a limited efficiency of the order of 20 to 21%, less than the efficiency they may have in the future, today the use of this type of vessel is also justifiable since the The use of solar energy will allow you to save considerably the external energy consumption of the boat, whether it is at low speed or high speed compared to the current energy consumption of these two types of uses.
So that when this vessel operates at high speed, the wings of the vessel do not tend to raise it and turn it backwards, it may be convenient to use its propulsion systems both at the stern and at the bow of its hull. The most convenient being the use of thrusters in pairs, so that the direction of rotation of their propellers is contrary to each other and increase their propulsion efficiency.
Types of applications and areas appropriate for the use of this type of ships
Figure 6. The mooring and anchoring should be done so that the wind and waves do not affect the boat due to the significant height that the folding wing system can have when folded.
This vessel for having the side wing system very close to the water when it navigates with the structure deployed and extended, and for having a great height when the folding wing structure is folded, it may have problems when it is sailing if there are strong winds and waves. For this reason, the most convenient thing is that this type of vessel is used in areas of sheltered waters or in open seas with light winds and with the precaution of not exposing this vessel to strong winds and waves such in as a time of storms. Perhaps in these cases the boat has to navigate with the folding wing structure in a semi-folded position to improve its lateral stability and decrease the impact that the swell may have on it.
For the loading and unloading of people and cargoes of this ship, due to the system of folding wings on the side of its hull, the most convenient is that it be done from the front or from the back of the ship. And in general, this type of ship will be convenient to use for the transport of light or medium loads and not for the transport of very heavy loads such as the large ships of current loads.
In addition, this type of WIG that are propelled from the water can suffer significant destabilization and difficulties in their maneuverability when the wind and waves are crossed and do not coincide with the direction of movement of the WIG propelled from the water. For this it is necessary to make both its water propellers and its air propellers "Steerable" to accommodate the wing structure to each wind condition that exists at all times.
The three types of applications that may be more convenient to use this type of boats are:
1_ In recreational yachts and sports or fishing boats with a length greater than 6 or 8 meters. In this case, when these boats move at low speed, they will be able to do it 100% with solar energy, and if they need a higher speed to move, they will be able to do it at a higher speed than these boats at present. In addition, when they are anchored or without movement, they can take advantage of the solar energy to recharge the electric batteries that they carry.
2_ On police or military ships patrolling coastal areas. In this case, when the boats are patrolling at low speed, they can do it 100% with solar energy and if they need more speed for their displacement or for a chase, they can also do it at a faster speed than the current patrol boats.
3_ In Ferries for the transport of people or loads from short to long distances.
In the case of transporting heavy loads at low or intermediate speeds, this type of solar Hydrodinamic WIG will surely be used in conjunction or superimposed with other types of propulsion systems such as battery-powered boats, or solar boats with the solar panel holder system telescopic type.
In the case of transporting people or light or intermediate loads at high speeds, the use of this type of solar Hydrodinamic WIG will also surely be used in conjunction or overlapping with other propulsion systems such as current high-speed boats powered by batteries electric or by the use of WIG or ground effect aerial vehicles where the use of WIG will begin to be more convenient than the use of our solar Hydrodinamic WIG, when the distances are greater, and when they need to take off or land from land airports in areas from the interior of the country.
But, in general, this type of high-speed boat has an interesting application to be able to reach speeds of around 100 or 125 knots, which cannot be reached by other types of boats such as catamarans or hydrofoils ships and they will probably be used mainly in short and medium distance boats that generally do not exceed 1.000 or 2.000 km of autonomy navigating at high speed.
Figure 7. The flaps at the rear of the wing will be able to control the final height between the wing and the water to increase the ground effect and the lift force under the wing.
Stability and maneuverability of these ships with winds and cross waves.
The ground effect vehicles that use water propellers as propulsion systems, in general, have drawbacks in the stability and maneuverability of the boat when it moves at high speed with winds and cross waves, as was the Ferry project Seabus-Hydaer of ground effect and high speed investigated by the European Union between 1997 and 2000 and which was frozen and abandoned after finding significant drawbacks in the maneuverability and stability of this type of boat when the boat is moving at high speeds with cross winds and waves.
This Ferry Seabus-Hydaer investigated years ago by the European Union, used gas turbine combustion engines and water jet propellants for its propulsion and had a design speed of 125 knots (231.5 km/h) and could transport 800 people and 100 cars.
Figure 8: Ground effect ship propelled with electric motors and supercavitating propellers with hydrofoils.
One way of reducing the harmful effect of the action of crosswinds against the lateral stability of the boat when moving at high speeds is by using multiple propulsion systems, each consisting of an electric motor, a supercavitating propeller and its corresponding hydrofoil in "V" shape, where each of them has the possibility to change the direction of their propulsion independently of each other and in general, especially the propeller units at the bow with respect to the propeller units at the stern of the boat.
Figure 9: Ground effect vessel with supercavitant propellers and hydrofoils oriented to move in the same direction as the wind and waves.
When this ground effect boat is moving for or against the wind but with a direction that coincides with the direction of the wind, all the propulsion units formed by the electric motor, the propeller and the hydrofoil will all be oriented in the same direction as the direction of movement of the boat.
Figure 10: Wind directions acting on the wing structure of the vessel.
In this case of the example, as we can see, the angle between the differences in directions between the direction of movement of the boat and the resultant of the wind that acts on the wing structure of the boat, which is what most complicates stability and maneuverability. of the boat is 8°, therefore if we rotate “all” the independent propeller units formed by the water propellers and hydrofoils and their respective electric motors that same angle and all both the bow and stern thrusters (As shown in Figure 11), the resulting wind will coincide with the direction of the wing structure of the boat so that the harmful effects of destabilization of the cross wind on the boat will be minimized and the stability of the wing structure of the boat can be significantly improved, and the boat will can improve its maneuverability and decrease the value of resistance to forward movement generated by wind and cross waves.
Figure 11: Ground effect boat with supercavitant propellers and hydrofoils oriented to move in a different direction than the direction of the wind and waves.
With this system of rotation independent of the propulsion systems to align the wing structure of the boat with the resulting wind that acts on said structure when the boat moves at cruising speed, we will reduce the harmful effects of the wind on the boat; but we will not completely decrease the adverse effects that cross waves will also have on hydrofoils and underwater propulsion systems of the boat, but since propellers and hydrofoils are generally small in size and move underwater, the destabilization that cross waves generate on these parts of the boat are likely to be much less than that generated by cross wind action on the big wing structure, but overall, the effect of the cross wave on the immersed thrusters in the water (once the harmful effect of the crosswind with the wing surface of the ship has been resolved) will be similar to the effects and destabilization that the cross wave generates in the boats with only hydrofoils and whose effect is often practically negligible in the operation of these boats only with hydrofoils.
With this steering system of the wing structure of the boat, as needed, it will be possible to significantly decrease or directly solve the problems of stability, maneuverability and increased resistance to advance caused by winds and cross waves on the normal operation of the boat. These crossed waves with which this boat can operate should not exceed certain heights at which it is impossible for the boat to navigate with a high wave height that will also occur with the wind or the waves in the same direction of the boat.
Therefore, I think that it may be interesting and necessary to study and investigate again with the application of this type of electric-solar propulsion system in this type of ground effect vehicles propelled by water propellers given the interesting characteristics of high speed and low power consumption that this type of high-speed vehicles could have, given the growing interest that the application of solar energy has in naval transport systems, and that is possible to use this type of ground effect vehicles propelled by water propellers both on high-speed ferries and on medium and large-sized recreational yachts and on coast guard patrol boats.
The fuel consumption per ton transported and the ratio of the transported load with respect to the total weight of the loaded Hydrodynamic WIG given in the tables shown in the figures are estimates and their values depend on the efficiency of the ground effect that is achieved with the WIG during its operation, the own weight with which this boat is manufactured and the weight of the fuels or electric batteries used.
How the maximum ratio of the lift coefficients Cl and drag Cd is 65, for the chosen wing profile and taking into account the decrease in this value due to the extra drag generated by the hull and other components of the boat , but considering that the ground effect achieved by this boat can become similar or greater than those achieved by the Ekranoplanes and be able to double the final relationship between the lift force L and the resistance force D. It is because These reasons we consider for the calculation of the fuel consumption of the boat at values of the ratio R=L/D, of the order of 30, 40 and 50.
In addition, considering that a good relationship between the ship's own weight and the transported load can be 50%, and if the trip is long distance, where it would be necessary to carry a lot of weight in electric batteries or fuel or if the weight The Hydrodynamic WIG itself is high, the percentage of the transported cargo can fall to an estimated value of 40%. That despite being a low value, it is higher than that of long-distance airplanes since the Ekranobarco can be built without the need to be pressurized or have as many aerodynamic and design requirements as said airplanes.
Furthermore, in these calculations, we estimate that the Ekranobarco's engine will be a Diesel engine with an efficiency of 30% and that the efficiency of the set of supercavating water propellers and guided flow air propellers will be around 75%.
The energy consumption calculations will be made for the case of a weight of 1 Ton or 9,800 Newton and a distance of 100 Km or 100,000 meters.
In these results we can see that the estimated consumption for the Hydrodynamic WIG would be lower than the consumption per load transported by an airplane, but higher than the case of a truck or the rest of the transport systems of large loads such as railways or interoceanic ships.
In principle, according to the results obtained, this type of WIG would be justified as a use for the transport of light or intermediate loads, or of people over short, intermediate or long distances. And what would also be interesting especially that it can be used in refrigeration loads for intermediate or long distances.
Project progress status
At this moment this solar boat project with the folding wing system for high-speed applications is presenting it as a patent application for its manufacture here in Argentina and I am looking for those interested in carrying out and applying this project both in Argentina and in other countries.
If you are interested in this project you can contact me by email:
Ruta 51, Km 5 - Villa Ramallo - Pcia. de Bs. As. - Argentina - Celular: 03407 15417654 - Email: Martin-Giordano@hotmail.com