This article was initially published in the Mar/Apr 2020 issue of Marine Professional magazine.
Shipbuilding expert Simon Yeo has made it his goal to drive efficiencies and reduce greenhouse gas emissions.
You joined Saga Cruises in 2016 and have been involved in what you describe as an exciting time for the company. What makes it particularly exciting?
Since Saga’s entry into the cruise market in 1996 the company has operated heritage ships. The opportunity to build new vessels offered the chance to design products to precisely satisfy the exacting standards demanded by Saga’s clientele. In addition, as a small, young company with limited corporate experience, it has been relatively challenge-free for us to introduce changes to both operations and designs. This has permitted some revolutionary modifications to the systems and processes.
The propulsion plant for the new ships is your responsibility. What challenges did you face there?
Application of the new Siemens eSiPOD drives with permanent magnet rotors permitted the addition of 12 crew cabins and optimisation of the provision storage arrangements compared with the original twin-shafted arrangement specified. This step also assisted in the development of a simple and usable SRTP (safe return to port) philosophy with a maximum of fewer than 340 actions to meet all 26 scenarios. To date it has proven to be robust and reliable, offering excellent manoeuvrability and economy.
The support from the OEM has been outstanding – which has generally been the case with all of our selected suppliers. Working with the shipyard’s young, talented engineers also permitted many novel and exciting efficiency improvements to be incorporated, such as:
- ECOMAP on the common-rail Tier III engines. This permits the selection of optimum electronic injection parameters based on the anticipated engine load from the itineraries to give ideal specific fuel consumption.
- The application of variable frequency drives on many pumps and fans matches performance to required flow rates to optimise energy consumption.
- The adoption of 100% reverse osmosis freshwater production capability (two-stage to produce both potable and technical quality water). Waste energy from the engines is used to heat the potable water, swimming pools and air-conditioning reheat.
- The selection of variable speed, hermetically sealed, multi-oil free compressor chillers capable of providing a coefficient of performance as high as 14 in temperate conditions with variable frequency drive pumps.
- The choice of R744 (CO2) for the domestic provision freezer, with cascade cooling from the chilled provision system, results in an enhanced coefficient of performance and reduction of global warming potential.
- The application of a thermally circulated exhaust-gas economiser with an enhanced heat-exchange surface and individual steam drums. This eliminates the requirement for exhaust-gas economiser circulation pumps with subsequent energy and maintenance load saving. The division of auxiliary cooling circuits to permit harbour, sea and manoeuvring modes to be arranged. This optimises flow and pump loads.
- The heating, ventilation and air-conditioning system is optimised to reduce energy consumption through the use of rego-therm wheels and a high percentage of recirculation.
- Vertical sides are coated with silicon paint and flat bottoms are coated with hard coats that require scrubbing as required.
- The automation system is provided with telemetry to allow analysis of where all the energy is being used, from the propulsion-plant power consumption to the steam and electricity in the laundry and galleys. This permits the development of Sankey charts indicating where and how energy is used on board and identifying areas of inefficiency to permit rapid fault identification.
The energy saved by these and other improvements has allowed for approximate fuel savings of in excess of 1,800 tonnes per year over the original specification. The required Energy Efficiency Design Index for the vessel at build was 15.875 CO2/tnm, yet the vessel attained an index of 10.158 CO2/tnm.
Saga has opted for scrubbers for the two ships. What was the rationale behind this?
The Spirit-class ships are fitted with hybrid scrubbers and Tier III engines. This is beyond the IMO requirement, offering the advantages of being able to use 3.5% sulphur content heavy fuel oil with minimal polluting discharge. We looked at the option of using liquefied natural gas (LNG) but rejected it for the following reasons:
- The vessels’ dimensions effectively meant their range would be unduly restricted.
- The well-to-wheel greenhouse gas emissions due to methane slip and leakage during bunkering were considered excessive and off set any marginal reductions in CO2 emissions.
- The challenges in recruiting and maintaining staff with the necessary LNG certification and experience were considered too great.
LNG can only be considered as a purely transient solution, as it is still a fossil fuel. Any asset using this fuel may be obsolete within 15–20 years as the optimum renewable carbon-neutral solution (ammonia, methanol or hydrogen) is identified and developed.
CV: Simon Yeo
Simon Yeo is an IMarEST Fellow, Chartered Engineer, environmentalist, mechanical engineer and chief design engineer for the newbuild team at Saga Cruises. He is responsible for the design of the propulsion plant for the company’s new generation of vessels.
What further steps do deep-sea passenger cruise liners need to take to achieve IMO’s 2050 emission targets?
Quantum leaps in efficiency are not a viable option. It will be necessary to take all steps to reduce fuel consumption through the adoption and promotion of efficiency-enhancing measures. We are committed to minimising the environmental footprint of our operations and are working on numerous alternative solutions to meet the 2050 IMO targets. These include further investigations into air lubrication systems and their applicability to our hull form; use of the Organic Rankine Cycle; and, where feasible, solar and wind energy recovery, hybrid drives with DC generation, fuel-cell technology and the application of alternative carbon-neutral fuel sources.
In your 30-plus-year career, what has been the biggest change?
The dramatic leap to big data and the ability for information to be gathered and analysed remotely. This has been particularly evident with the Spirit class, which has multiple items of plant that can be remotely interrogated and diagnosed. This means that technicians do not need to fly around the world to repair equipment, which further reduces our carbon footprint.
With Spirit of Discovery on the water and Spirit of Adventure due this year, what’s next for you and Saga?
The initial feedback from guests after six months of operation of Spirit of Discovery has been very positive, and we are now investigating options for further newbuilds. Given the company’s spirit and values, and the fact that we have a small, committed group of experts in the newbuild team, I will be happy to stay with the company to be part of its growth as it strives to become the prime British cruise line it deserves to be.