24 de julio de 2020

Large-scale solar ship

Large-scale solar powered ship




Figure 1: Horizontal solar panels can capture direct solar energy while vertical panels can capture reflected sunlight




Summary


With the depletion and increasing cost of traditional fossil fuels, solar energy is a promising alternative technology for the shipping industry.

Solar power has the potential to reduce the cost of energy spent by current ships, but the biggest problem with the use of solar energy in the propulsion of ships is that a surface for capturing solar energy between 6 to 8 times or more than the surface of the ship's own hull is needed.

For this, a system was developed that allows the solar energy collection surface to be expanded when the ship is sailing and that folds and reduces its size when the ship has to moor a port or navigate rivers or narrow navigation channels.

The system that is proposed to expand and reduce the size of the solar energy collection surface is formed by a telescopic structure that also allows to take advantage of both the direct solar energy of the sun that radiates on this structure of the ship and the solar energy reflected in the surface of the water, and in this way allows to increase the total solar energy generated for the consumption and propulsion of the ship by this telescopic system of solar energy capture.





Introduction


With the depletion and increasing cost of traditional fossil fuels, solar energy is a promising alternative technology for the shipping industry. Solar power not only has the potential to reduce the cost of energy spent by current ships but also improve ships’ navigability, particularly in the open sea where there is a large amount of solar energy readily available. The surface of solar panels that a cargo ship requires in order to capture the solar energy necessary for its operation must be six to eight times larger than the surface of the ship’s hull. This will ensure the ship can navigate autonomously during the day and night at the same speed today’s cargo ships sail. Therefore, a solar energy system is needed that allows solar panels to be placed beyond the ship’s own surface area.

My solution is a telescopic structure that can expand and decrease its size when needed. This design will enable a ship to navigate both the open sea – in calm sea conditions it can sail with the extended solar structure – as well as ports, narrow rivers and channels, during which time the structure can be adjusted to fit a ship’s measurements.

To be able to expand and reduce the size of the structure that carries the solar panels, a telescopic structure was designed that has solar panels arranged horizontally and vertically. the horizontally arranged solar panels would capture direct energy from the sun while the vertically arranged solar panels would allow diffused solar energy and sunlight reflected from the sea water to be captured. Solar energy reflected in the open sea is an important source of energy (we consider this energy to be nearly 50% of the direct solar energy of the sun in the open sea), which can be added to the direct solar energy used in principle by the horizontally arranged panels.



Figure 2: Solar panels will be organised in a telescopic structure allowing navigation on the open sea and in ports



If the support structure of the solar panels is very large, this type of ship also has as an option to have two floats attached to the sides of the hull in order to support the structure’s own weight, taking the form of a Trimaran species. where side floats only fulfill the function of supporting the weight of the structure of the solar panels and no loads are carried on said floats.

Although these floats would increase the ship’s resistance in a semi-folded position, it would also improve the lateral stability of the ship, allowing it to navigate the high seas better during storms and easily maneuver through shallow water depths.





Solar panel efficiency


At this time the maximum efficiency of commercial solar panels is approximately 20 to 21%. There are space-use solar cells with efficiencies of the order of 35 to 40%, however, they would be very expensive to use in this type of ship. The maximum efficiency that a multi-juncture or tandem solar cell could have is 68.2%. Solar cells composed of silicon quantum dots, which have the potential to reach efficiencies of the order of 40-50%, are currently under development.

Laboratories around the world are working on new types of solar cells that have the theoretical potential to reach efficiencies greater than 70%. 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%.




Speed and characteristics


As an example, we will consider the application of this form of solar-powered propulsion system to a Panamax-type vessel of 50,000dwt with a total maximum length of about 250m, a maximum width of 32m and a draft of 12m. However, this type of telescopic layout of solar panels may also be applied to larger ships such as post-Panamax ships or smaller vessels where it is justified.



Figure 3: Solar panels in a fully folded position


For a vessel of these dimensions, the maximum width of the support structure of the solar panels would be 256m (making it eight times larger than the maximum width of the ship), 250m long (equal to the maximum length of the vessel), with the height of the vertical solar panels 128m (half the width of the horizontal panels). For calculation purposes, we consider the hours of sunshine per day with a standard radiation of 1,000W/m2 at a south latitude of 35° (the position of Buenos Aires or Cape Town) is 6.5h/day for an average summer day and 2.5h/day for a winter day in open sea conditions.

Consider also that the vertical solar panels that capture diffuse and sea-reflected surface solar energy have an energy radiation of the order of 50% of the direct solar energy of the sun. That is, that the vertically arranged solar panels will generate around 50% of the energy generated by the horizontally arranged panels, for a general situation of the ship, although this diffuse reflected solar energy will depend on the position of the ship and the vertical panels relative to the sun.

As stated previously, the solar panels used in this ship will have a maximum efficiency of 50%, generating an estimated 13,000kW of energy per day during the summer and 5,000kW of energy on a typical winter day.

Further factors to be considered in this scenario include:

The extra advance resistance generated by the ship’s pontoons and the sail resistance of the vertical solar panel as well as the structure of the horizontal solar panels.

 The vessel’s two electric motors coupled to two propellers and direction of different turns, which generates an improvement in propulsion efficiency with respect to the use of a single propeller of 5-8%.

The vessel and its pontoons will be coated with silicone paints, which have 4-8% less resistance than the conventional paints that are primarily used today.

The overall efficiency of the electrical system of both motors and electric batteries is of the order of 80%.


Given all of the above, we expect the ship to have an average speed of 16.5knots (equal to 30,55km/h) on a summer day and 12.5knots (equal to 23,15km/h) on a winter day. This calculation is only to estimate what such a ship could achieve in the future with a solar cell efficiency of 50%. However, the efficiencies of marine solar cells today are lower than the values considered in these calculations.




Operation at higher speeds


This type of ship will have to carry electric accumulators to store the solar energy generated by the solar panels during the day for the night. Additionally, a sufficient amount of electric batteries are needed to guarantee the ship will have energy stored for at least four or five days of operation in case the ship has to go through an area of storms or cloudy days. If a greater speed is needed, the batteries carried by the ship can be recharged while at port.

During its operation, the ship will be able to draw on the energy generated by the solar panels and the energy from the electric accumulators, allowing the ship to obtain a greater speed than a vessel which only relies on the energy generated by the solar panels.

Another interesting application that ships powered by solar energy may have is the generation of surplus electrical energy at sea that could then be used in coastal areas on land. Such ships could replace floating solar parks, which can be difficult to tie to the sea floor and struggle to withstand the swell of a strong storm.

If we use a solar boat to generate energy with solar energy that radiates over the seas or the oceans offshore, it will be easier and more convenient than doing it with floating solar parks.

In addition, these power-generating ships in their offshore operation may function as electric power recharging stations for ships that need more electrical power for operation, either because they are winter days with little solar radiation at sea or because they need higher speed of transport of the loads that the vessel can give it with the solar panels that it carries with this type of solar panel carrier structures.




Loading and unloading


In this type of solar ship, when the structure that holds the solar panels is folded, the telescopic structure and its solar panels will be folded on top of the ship and above the loads that will be placed on the ship’s hull, whether bulk cargo or containerised cargo.

To be able to load and unload a special telescopic crane bridge would be required for loading and unloading. Current port cranes would be incapable of performing this task correctly because the upper part of the ship is covered by the solar panels and its support structure when it is folded.

The crane bridge would have a main carriage that moves longitudinally along the ship’s hull and transversely across the width. It can be seen in schematic form in Figure 4, illustrating how the crane bridge will load and unload while moored.




Figure 4: The telescopic crane bridge




Ship side stability


As the telescopic structure carries solar panels and as the same solar panels are arranged in the upper part of the ship, this weight can affect its lateral stability during storms or heavy waves. One feasible solution to this problem is to place the pontoons at a certain distance from the ship’s hull so that the lateral stability of the ship increases in rough navigation conditions (Figure 5).


Figure 5: Solar panels in a semifolded position. The pontoons will increase the lateral stability of the ship




Construction of the first ships powered partially by solar energy

From another point of view, looking to the future, one possibility is that solar powered boats will begin to be used after electrically powered boats start to be manufactured from rechargeable electric batteries, as these types of boats are less complex to manufacture than fully solar powered boats as proposed in this article. The ships that are currently beginning to be manufactured powered by lithium batteries and recharged in the ports, how current electric cars are recharged, have a cost of the recharge energy purchased by the ship from the systems of recharges at a price that ranges between 0,12 to 0,15 u$s/KWh, but if we take into account that today the cost of wholesale production of solar energy in a photovoltaic park in a sunny area of ​​a desert it does not exceed 0,02 or 0,03 u$s/KWh and although in the open sea the direct solar radiation is a little lower than in a desert in the future it will surely be convenient that the electric boats that are currently being manufactured are add as many solar panels as possible to self-consume your own generated energy and thus decrease the costs of the energy purchased to propel it to external electrical energy sources to the boat, starting slowly to manufacture the solar powered boats how we propose in this article.

One way to start building these types of ships with the solar panels that exist today, which as we said have a lower efficiency than those considered in the calculations we made, is to make a solar ship with a lower support structure for the panels. without the side pontoons and without the vertical solar panels, decreasing the solar energy generated by the ship but also decreasing the complexity of construction of said structure and making a propulsion to partial solar energy, that is, partially solar energy with the current panels that they have an efficiency of the order of 20-21% and the rest of the energy needed to move the ship would be by recharging the ship's electric batteries with recharging sources external to the ship.

This type of ships powered partially by solar energy could start to build in the manner indicated in the figure below, where it is seen that the surface of the solar panels is less than the vessel intended to operate 100% solar energy but also surely easier to build and test on the first ships that want to be manufactured with this telescopic solar panel support system.


Figure 6: Concept design for the first hybrid solarpowered ship




Basic operating costs of current ships


Our interest in this cost analysis is to see what impact the cost of fuel and the different consumables of the main propeller engine and auxiliary generator sets have on the total operating cost of the ship. In this analysis, we will not take into account the total costs of the shipping company, such as administrative expenses, taxes or its profit, we will only take into account, as we said, the approximate costs of the operation of the ships.

For this we will make the following considerations:

• The construction and start up cost of our 50,000dwt bulk ship is 60 million dollars and with a useful life of 40 years.

• The main engine of the vessel has a maximum power of 14,560 Kw with an estimated fuel consumption of 20,000 liters per hour of operation.

• The operating time of the ship will be approximately 65% of the time of its useful life, due to maintenance stops, stops due to loading and unloading of the same or other cases.

• The approximate cost of the fuel consumed by the vessel is 0,5 u$s/liter.

• This ship will have a staff of 20 people with a 30-day work period on the ship and 30 days off, so the total staff of the ship will be 40 people.

• The average and approximate salary of each ship operator will be u$s 8,000 per month considering the gross salary, taxes, bonuses, prizes or other costs.

• The approximate expenditure on supplies and foodstuffs of the personnel in the 40 years of life of the ship will be 20 million dollars.

• The expense in supplies for the maintenance of the ship during its trips above the ship in the 40 years of useful life of the ship will be 20 million dollars.

• The cost of maintenance at their stops in shipyards or dry docks in the 40 years of their useful life will be about 80 million dollars.

• The registration, patent and insurance costs of the ship in the 40 years of useful life will be 80 million dollars.

• The fuel cost of the ship's generator sets, the oil and other consumables of the main engine and the various auxiliary combustion engines of the ship will represent approximately 15% of the total cost of the fuel consumed by the main engine of the ship.


With these considerations we will have the following operating costs of the ship in its 40 years of useful life.

• Ship Cost: 60 Million Dollars.

• Main engine fuel costs: 2.277,6 Million Dollars.

• Cost of fuel and consumables of auxiliary combustion engines: 341,64 Million Dollars.

• Cost of ship personnel: 153,6 Million Dollars.

• Cost of edible supplies of ship's personnel: 20 Million Dollars.

• Cost of supplies for maintenance of the ship during its voyages: 20 Million Dollars.

• Cost of Maintenance of the ship in the shipyards: 80 Million Dollars.

• Cost of registration, patent and insurance of the ship during its 40 years of useful life: 80 Million Dollars.


Thus, we have that the total operating cost of the ship in its 40 years of useful life: 3.052,84 Million Dollars.

And the cost of fuel and consumables of all the ship's combustion engines: 2.619,24 Million Dollars.

And thus, the percentage of the cost of fuel and consumables of combustion engines with respect to the total operating costs of the ship during its useful life is of:   86,36%

With this we can see that the main cost of a ship in its operation is the cost of fuel, oil and the different consumables that have their engines to combustion of a ship. Therefore, if we achieve with the use of the solar energy, reduce the cost of energy used by the ship, we will also significantly reduce the operating costs of the ship and the final cost of freight of the transported loads.

This allows us to think that with the improvement in efficiency and cheaper that the photovoltaic panels and the energy accumulators that the vessel needs to be propelled to solar energy in the near future, the cost of operation and the final freight of the Solar powered ships can be significantly lower than the current freight costs of the loads.




Conclusion


The increase in the cost of fossil fuels in recent years due to the increasing depletion of its world reserves, forces us to look for alternative fuels, where solar energy, due to the abundance of obtaining it, especially in the open seas and oceans, and with its ever-increasing cost reduction and improvements in the efficiency and in the useful life of its collection equipment and accumulation of the electrical energy generated, it can be a very important alternative to consider.

Although the use of solar energy in cargo ships has certain technical difficulties such as the addition of the telescopic structure proposed here to increase the surface area for capturing the solar energy that the ship will need for its operation, which may add inconveniences in navigation compared to traditional ships; given the high cost of fossil fuels, it allows us to think that the use of solar energy in the propulsion of ships will be able to effectively replace the use of traditional fuels, and in addition, significantly reduce the cost of operation and value end of the freight of the transported loads.


Furthermore, considering the other alternatives currently being studied to replace fossil fuels on ships that are primarily the use of electric batteries or hydrogen, which would recharge on ships as they currently recharge on electric cars; we also believe that the direct use of the solar panels on the ships themselves, will grant them greater autonomy to reach greater distances traveled without the need for energy recharges and a lower cost in their operation since it consumes the energy produced by their own solar panels and not the purchase of electrical energy from sources external to the ship is necessary.

Therefore, we believe that the telescopic structure that supports solar panels that we propose in this project so that the ships can be powered by solar energy can have a great implementation in high-load transport ships, both now and in the future.




Project status


At this time, a patent application for the telescopic structure of the ship’s solar panels has been filed, and we are seeking interested industry parties in hopes of being able to build this project.

If you are interested in having the manufacturing patent for this project in your country you can contact me by email:

Martín-Giordano@hotmail.com.