Introducing The Aeromancer
Aeromancer offers an innovative propulsion-scale wind power solution for long range high endurance naval vessels. The solution enhances system capabilities by providing indefinitely sustainable electrical and propulsion energy without fuel. It accelerates development cycles by providing a scalable technology platform that can modularize vessel design, eliminating the need for holistic designs for every vessel purpose as well as offering a simpler alternative to the complex state of the art hybrid energy systems. This simplification allows a framework suitable for streamlined procurement strategies, allowing ‘building blocks’ to be defined and sourced from different vendors. It reduces sustainment costs through drastic MRO/crew reduction plus elimination of fueling infrastructure. Finally, it mitigates technical risks through modularization and simplified systems architecture.
Currently there are a wide range of technologies used to enhance performance and sustainability for oceangoing vessels. These technologies range from simple with low capability to very capable and highly complex. The goal of Aeromancer is to have high capability in a very simple to design, implement, and maintain platform. This is accomplished with a wind turbine as the primary power source combined with a large battery buffer using an all-electric DC bus architecture. The wind turbine and battery technologies are the two primary enablers, and are enhanced by high efficiency sub systems.
Our EcoVert75™ was designed for distributed generation applications, like powering schools, retail stores, etc. The key requirements focused on people living and interacting near the machine. It is technically called a pitch-controlled H-VAWT, a design originally modeled, prototyped, and tested by McDonnell Aircraft Corporation (now Boeing) in the early 80’s. It produces a healthy 70kW in a 21 knot wind at 32 rpm. With a few hardware and software modifications it is an excellent machine for use aboard a vessel. Here are a few reasons why:
- Less than ¼ the head mass and a third the storm wind loads compared to other similarly sized turbines
- Less than ½ the operational blade speeds of conventional turbines at similar power outputs
- Very low noise & safe blade path for vessel occupants
- High power efficiency, Cp > 0.5 at some wind speeds
- The ability to produce propulsion thrust directly with the turbine instead of converting all the wind power into electricity, saving conversion losses
Battery performance is advancing at a rapid pace, and is now providing critical energy supply on modern ships regularly. From work vessels like the impressive Edda Freya to pure battery electric ferries like the ro-ro Ampere, and many more, Li-chemistry batteries are developing a maritime propulsion legacy. Numerous battery cell manufacturers are promoting solutions for marine applications. Traditional classification societies are also developing standards for large scale onboard Li based energy storage. We have been studying, testing, and evaluating cells and battery management for years and have already applied the technology in a marine environment.
The Vessel Concept
Propulsion scale wind turbine power is the heart of the Aeromancer concept. A common metric used to describe a sailing vessel is the sail area displacement ratio (SA/D). This basically allows vessels to be compared to each other in terms of a power to weight ratio. The highest SA/D ratio tested with a turbine thus far has been <5. Aeromancer’s target SA/D is 11. Given that ocean going sailing vessels are commonly around 15, and racing vessels above 20, there is opportunity for advancement in power to weight ratio metrics.
The 2,500 kWh energy storage system will be divided into the two outrigger hulls, along with the DC-DC converters, the propulsion motors and drives, and HVAC equipment. Cooling requirements are suppressed by the highly paralleled architecture. Unlike an automobile or even a ferry, the battery system is sized for a very low duty cycle. High thermal conductivity construction of these hulls aids in transferring heat to the external environment, and humidity can be controlled by a creative venting strategy. This approach limits the interfaces with the main hull, eliminates raw water systems entirely, and allows building and testing of these hulls at a subsystem level—completely decoupled from the requirements of the main hull.
Aeromancer’s main hull is dedicated to little more than housing crew and mission spaces. In normal conditions the hull is jacked up clear of the water so it has no main running surfaces. Given the absence of diesels or related systems, all spaces within the main hull can be environmentally controlled, and relatively little mechanical space is necessary. A large enclosed garage is provided for storage of a RHIB and unmanned systems. Additionally a control office with multiple workstations and a maintenance workshop are available.
A Comparison to Status Quo Ship Design
IC engine propulsion has served ships well and will continue to for many years, especially on high speed vessels. It has drawbacks however that seem ubiquitous today in the absence of alternatives. One such drawback is the physical I/O that contributes to virtually all internal shipboard maintenance:
- Introduction of copious amounts of humid air into mechanical spaces
- Introduction of fuel having conditioning and contamination mitigation requirements
- Introduction of cooling water that fouls complex cooling systems
- Output and exhausting of high temperature gases
- Output of high frequency mechanical vibrations
These negatives are eliminated along with the engines. Moving electrons around is not immune to failure but generally does not require a lot of maintenance, and while the wind turbine has moving parts they are few in number compared to an IC engine.
Not all purposes are suitable for wind powered battery electric ship technology. As of now the batteries will hold far less energy than large fuel tanks, but most regions of the world’s oceans have abundant wind energy available on a regular basis so that there isn’t a need to carry weeks or months of energy on board. ISR, SAR, and other applications that host UAV’s or UUV’s as a primary function are a good fit, as is any application that long term station keeping or long term slow cruise speeds are acceptable.
A Comparison to Other Potentially Disruptive Technologies
Solar PV is excellent technology and should augment power supplies whenever possible. Planet Solar even made famous their MS Turanor by sailing around the world on PV power alone. The trouble is that it requires a great deal of area to obtain enough power to propel a ship. As with the Turanor, much of the functionality was sacrificed to maximize unshaded module area. Aeromancer would require more than 10,000 SQFT of unshaded module area to derive equivalent power production to the EcoVert, in a Caribbean type environment. This isn’t practical on a 100’ vessel and scale doesn’t alter these dynamics.
A return to sailing technology is receiving consideration lately. Whether using flexible or rigid sails, the aerodynamic efficiencies on vessels are limited by the tip speed ratio, or the ratio of the airfoil’s speed through the air to the wind speed. Foiling catamarans, like the America’s Cup race boats, are able to sail faster than the wind, and therefore achieve tip speed ratios well above 1. This allows their airfoils (sails) to obtain higher propulsion efficiency. This works great on a racing boat, but when loaded down with all the needs of a ship serving a purpose other than racing, the efficiency is reduced by lack of ability to achieve those same tip speed ratios. Also when the vessel is intentionally moving more slowly than optimal; such as when limited by comfort in a seaway; performing mission objectives not involving transit; or sailing in a non-optimal direction; wind energy is wasted. EcoVert on the other hand can maintain tip speed ratio and optimal angle of attack independently of vessel course and speed. The batteries allow the extra energy to get stored for later use.