Power and Energy Aboard the SSV Robert C. Seamans
Sea Education Association’s newest vessel, the SSV Robert C. Seamans, is the most advanced ship of her kind. She is both a sail training ship and a multi-million dollar oceanographic research vessel. She is 134.5’ long, has a beam of 25.4’, carries a complement of up to 40 people with up to 25 students, and is powered by 8200 square feet of sail area, a 455 hp 3408 Caterpillar diesel engine, and two 40 kw Northern Lights diesel generators. The Seamans carries 6600 gallons of diesel fuel and uses two reverse osmosis desalination plants to make freshwater. All this easily allows her to stay at sea 6-7 weeks at a time, but she is capable of even longer trips. She is also equipped with both wet and dry science labs as well as a computer library. A research ship with a crew of this size obviously has enormous energy demands, and the two diesel-powered generators provide all of the power.
Considering that part of SEA’s mission is to educate students about environmental sustainability, the question of whether or not to integrate some form of alternative power generation capacity like wind turbines, photovoltaic solar panels, or towable water turbines into the ship was considered during the design and planning phase. It was ultimately decided not to include any power source other than the #2 marine grade low-sulfur diesel fuel she carries today, for a variety of reasons. In the decade since her launch in 2001 that same question has been raised many times. What factors caused SEA and the designer (Laurent Giles of Hampshire, England) to reject renewable energy in the design? Is that still the right choice? For many, the thinking behind the original decision is not clear, and the questions become more pressing as a time when fuel prices only continue to climb. Many other smaller sailboats carry such devices, and commercial cargo ships and tanker ship companies are investing heavily to adapt alternative means of power generation in order to cut fuel costs. However, both of SEA’s ships (including the Atlantic-based SSV Corwith Cramer) actually were designed as hybrid vessels. SEA has been utilizing the wind via traditional sails since 1971, but other contemporary renewable energy technologies exist that are better suited for marine industries like transport.
As the marine industry continues to invest in alternative energy, many technologies are becoming increasingly feasible options for ships looking to complement traditional petroleum fuels. In order to identify which of these technologies is most promising, one study surveyed ship builders, designers, operators and government authorities in Taiwan in order to discover which alternative technologies they preferred and their respective familiarity with each. Hydrogen combustion was the most favored at 80%, followed by solar at 72%. Fuel cell technology came in at 62%. Theoretically, hydrogen can be burned in most internal combustion engines with little modification, and this makes it an attractive option. Photovoltaic cells were favored by some because of the enormous deck area available on super tankers and modern bulk carrier ships. Wind turbines and towable water turbines however are not efficient options for powered vessels. They create drag in order to harness the apparent wind or water flow created by the drive from the main engine--essentially an inefficient extra step in generating electrical energy that could just come straight from the fuel. On vessels under sail, turbines also detract from propulsion via drag, but because these ships are wind powered it is a useful way to convert wind energy into electrical. Overall, Taiwanese professionals expressed a desire for progressive adoption of renewable energy technology, citing benefits such as reductions in emissions, noise, vibrations and foul smells, reduced risk of fire and fuel spill, lower operating costs, and increased flexibility. These are all benefits that SEA realizes in its use of sails, with the additional benefit of a much more stable platform for scientific deployments. When hove too under sail, the Seamans is noticeably more stable than comparable motor-driven research vessels.
Even though wind turbines may not be suitable for most shipping applications, there is another method of harnessing the wind that requires neither turbines nor traditional sails. Giant kite sails (Fig. 1) are currently being fitted to cargo ships and tankers and producing impressive results. The kites are computer controlled and fly at heights of 100 to 420 meters. In ideal conditions, they can generate up to 2,700 horsepower and reduce fuel usage by up to 35%. SkySails, a new company based in Germany, has recently signed an agreement with the international shipping and freight company Cargill for kite applications, currently a 320 m2 kite on a 170 meter bulk cargo carrier. These types of sails are especially convenient for cargo ships due to the lack of a complex system of standing rigging cluttering the deck and the ability to operate them with very little manpower. Critics have contended that other methods of cutting fuel may be more economical, as the kite systems can cost anywhere from $400,000 to millions of dollars, but current applications have shown fuel savings of around $1500 per day. A 2009 International Maritime Organization study found that using kite sails can theoretically result in energy savings of up to 44% at a speed of 10 knots under optimal weather conditions, and the current technology is only getting more efficient with continued research. With regard to SEA’s more traditional sailing, no detailed study has yet been undertaken to quantify fuel savings (could make for a very interesting comparison with kite sails). This could be a very useful direction for future student research.
￼￼Figure 1. Proof of the design’s simplicity. A commercial bulk cargo ship demonstrates a real world application of a SkySail’s kite while cutting fuel consumption and emissions.
For SEA, the decision to stick with traditional sails and not integrate alternative energy systems was based largely on safety and function. As a student ship and oceanographic research ship, the Seamans must be a reliable work platform that supplies power the instant it is needed. When she was constructed the idea of installing renewable systems was discussed, but ultimately the designers felt the added complexity was not worth the benefits. Whether running the hydro-wire for a scientific instrument deployment while the galley is cooking dinner (one of the main power consumers of the ship) or running the fire pumps in an emergency, the generators on the ship have to be ready to meet sudden spikes in energy demand. Currently the only energy source capable of reliably meeting these needs is diesel fuel. For the Seamans, this resulted in the two powerful generators aboard today, one of which is running at any given time and can power the entire ship. They are switched every 200 hours for maintenance, but the ship always has power even during the transfer. Over the years since her launch however, the generators have been plagued by an expensive problem that stems partly from just how powerful they had to be.
Diesel engines run most efficiently under load. Because the average power load on the generators aboard the Seamans at any given time is typically around 17.8 kW, less than half of the 40 kw they are rated at, the generators frequently run at very light loads. Peak loads, however, can reach as high as 46 kW, and the generators can provide this much power for a limited duration during power hungry activities like cooking and scientific deployments. The absolute peak load for S239 reached 50 kW, nearly 300% of average demand. Because the generators had to be sized appropriately for these temporary spikes, maintenance issues have resulted. Consistently running under a light load may be resulting in a buildup of carbon deposits on the fuel injector nozzles. Carbon fouling such as this causes dirtier exhaust and decreased generator efficiency. This means that the injectors must be manually cleaned (or replaced for $600) approximately every 1200 hours, roughly every other semester). This is an expensive, time consuming, and delicate job. The engineers aboard S239 also suspect another practice may be contributing to carbon fouling: mixing used motor oil into the generator’s diesel fuel at very low concentrations (<1%). This has been standard practice at SEA for years, as burning the used oil obviates the problem of disposal in remote ports. The generators themselves produce 4 gallons of waste oil each week, and the main engine produces 25 gallons of oil per change--a rather significant amount over the course of the semester. But waste oil is saturated with carbon and adding it the generator’s fuel may be contributing to the carbon fouling issue, though there are many other variables involved that are difficult to analyze.
Seth Murray and Jimmy O’Hare, S239’s chief and assistant engineers, decided to conduct an informal experiment concerning the addition of motor oil to the fuel. As of February 25th no more waste oil was added into the fuel source for either generator. The injectors were cleaned in the starboard generator, and those in the port generator were left untouched. Less than a month later, by March 17th, there had been a visually apparent reduction of exhaust from the port generator, and the starboard generator exhaust remained clean when typically it would have become smokier in the weeks following the cleaning as injectors fouled again. While not a precisely scientific experiment, it has provided some insight into the issue. The under-load problem with the generators presents one of the major complications when considering renewable energy installation on the ship, but clearly there are other variables that require further investigation. Currently it is thought that adding any additional energy generation would only reduce the load on the generators further and unfortunately compound the carbon fouling problem.
Figure 2. Looking over the main engine, the #2 generator is visible on the starboard side of the engine room. The port generator is directly opposite at the viewer’s back. Photo Justin Lawrence, 2012.
A way to circumvent the under-loading issue might involve using alternative energy to cover the low-level needs of the ship so that generators could be shut down completely for a period of time. For example, in order to provide the average 17.8 kW load,118.7 m2 of photovoltaic solar panels would have to be installed. This is assuming that with an average solar radiation density of 1kW/m2 a one m2 panel operating at a generous 15% efficiency (commercial applications range from 13-15% efficiency, and peak efficiencies of 22% or higher are only found in controlled lab conditions or in space) would provide 0.15 kW of power. 118.7 m2 is also just the pure photovoltaic surface that would be needed; the calculation doesn’t include frames or mounting hardware. A surface area large enough simply isn’t available; even if the ship were a rectangle with a beam of 25.4’ from bow to stern, this area is still just over a third of the 313.5 m2 of hypothetical area. Also, to maintain an efficiency of 15%, all of the panels would require expensive aiming mechanisms to be perfectly aligned. There is just no safe place to install the panels required to generate any economically significant amount of energy. Even if there were room, the vessel would have to be retrofitted with equipment to allow that energy to be added to the grid. A synchronous inverter or a large battery bank would be necessary to sync the power source with the generators, and the wiring and installation of such a system is complex and expensive as well. There are similar issues with wind or water turbines: there isn’t space for the number of turbines needed, and towable water turbines don’t yet provide significant amounts energy. However, both solar panel and turbine efficiencies continue to climb with continued research, and it may not be long before these technologies become more viable options for SEA.
The good news is that SEA already harnesses massive amounts of renewable energy in the form of wind power by sailing, and saves significantly in the process. During our cruise, uncooperative weather resulted in an anomalously high number of engine hours, but even while motoring our sails undoubtedly contributed to propulsion and saved money. In order to calculate the rough fuel efficiency and operation cost of the main engine, we can use the following calculations for the S239 cruise: 4925 gallons of fuel oil consumed overall – 1794 gallons for the generators (39 gal/day • 46 days) = 3131 gallons consumed by the main engine. With 440.7 hours on the engine for this trip, this equates a rate of 7.1 gal/hour. This number is actually artificially low, as the engine hours figure includes time spent running but not in gear and warming up, when the engine consumes very little fuel. Estimates of the true rate of fuel consumption are closer to 8 or 8.5 gal/hour while steaming. This translates into a fuel bill of $14,402 for the main engine alone (using the price of $4.60/gallon paid for refueling in Hawaii). Clearly any sailing that SEA does has results in enormous fuel savings.
While renewable energy is becoming increasingly common on land, applying these technologies to a floating platform with strict space and time limitations adds further complexity. Renewable energy has come a long way already, but it has yet to achieve the mature reliability, consistency, and international acceptance of fossil fuels. It seems the most economical option for SEA in the near future would be to attempt to route cruise tracks as carefully as possible in order to maximize sailing time and reduce engine hours. (S239 had abnormally high engine hours that are partially attributable to a windward leg up the Marquesas). But renewable energy technology continues to progress, and it may not be long before other options become appealing to SEA. About 5 years down the road the generators on the Seamans will require replacement, and this may provide a logical opportunity to consider alternative power generation. Future student research on the energy savings from sailing could also be a great way to illustrate how important alternative energy is to SEA and to stay on top of industry trends. Another worthwhile direction for further research might be a more detailed analysis of the carbon fouling problem, as resolving that issue would save SEA significant time and money. In the meantime SEA continues its 40-year tradition of utilizing the same power of the wind that has propelled goods, people, and knowledge around the globe for centuries, to educate students on living responsibly in an increasingly global environment.
Figure 3. The Recipe For Water
Aboard the Robert C. Seamans, all of the fresh water comes from the two reverse osmosis seawater desalination plants pictured here. These plants consume 5-5.5 kWh to produce roughly 80 gallons of freshwater an hour with an average recovery rate of 35%. During S239 we consumed 22,554 gallons of freshwater, requiring about 1410 kW.
The recipe: one gallon of freshwater = 3 gallons of salt water + 21.7 milliliters (less than 1/10th of a pint) of diesel, some sand, and a series of very, very fine filters. Photo Justin Lawrence, 2012.
Justin Lawrence, Boston College
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How to cite this page:
Justin Lawrence. “Power and Energy Aboard the SSV Robert C. Seamans,” Atlas for Sustainability in Polynesian Island Cultures and Ecosystems, Sea Education Association, Woods Hole, MA. 2012. Web. [Date accessed]