by Ed von Siemens
The beauty of Energy Management is in the simplicity of conceptualizing an optimal balance of efficient production and thrift consumption yet the complexity lies in the accountability of details. I first started visualizing an optimal energy balance when I saw the work at the “Energy & Environment at Livermore National Laboratory”. The graphical representation of US Energy Flow Trends helped me visualize the production and consumption of energy across the United States while identifying the significance of each sector.
Their model inspired me to visualize a cruise liner or passenger ship in a similar fashion. It was exciting to grasp within a ship the same concept of balancing optimal power production in order to meet minimal energy consumption and I used a generic 130,000gt Diesel Electric passenger ship with Azipod type propulsion. I learned to map and focus on each area, or sector, in order of priority, or financial significance, while defining clear lines of accountability.
US Energy Sources and Flows - Useful and Lost Energy
Power Production Plant – Diesel Generators: The production of power is ultimately the best place to start examining the balance of power because as the most significant sector and under clearly defined scope of responsibility it has the best return on investment. The typical passenger ships in my fleet are fitted with Diesel Electric plants and have four to six generators and range from 12MW to 20MW depending on hull size and number of guests. While all the energy on board is derived from oil (we need to develop alternative sources of energy other than hydrocarbons), heat is produced by boilers and recovered from the engines while the electrical energy is produced by diesel engines and primarily all services are powered by electricity. The diesel engines drive generators and the power factor is far from optimal, I’ll touch more on that subject later but are typically around 0.8, while the diesel engines are limited to produce energy at a rate of 187grs/kW at its best. We must accept some limitations within our capabilities from the inherited equipment but we focus on how to monitor the variables that help us reach our equipment limitations. In other words, our goal is to reach our equipment limitations and this is where the fun begins. We should ultimately monitor how close to the equipment limitations we transfer our energy and introduce a Balance Score Card mechanism to drive the behavior we want. The simplicity in producing energy at the efficiency limits lies in the ease of accountability. The energy production plant is under direct responsibility of the Chief Engineer and therefore within one person’s reach of influence. We are however compelled to help our human resources reach our organization’s goals and therefore introduce several awareness and educations programs to adjust the variables that influence the optimal transformation of energy from oil. Once the awareness, education, and support have been established it is critically important to allocated responsibilities and execute on accountability to meet the goals.
Energy Consumption – Propulsion Systems: On the other side of the energy balance are the consumers and among them the primary energy use on board a diesel electric ship is allocated to the variable frequency propulsion drives. Depending on the speed, weather/current patterns, and other influences the propulsion systems will consume anywhere from 40% to 65% of the generated power. The optimization of the propulsion will undoubtedly reap the best benefits in the reduction of energy consumption. We may need to live with intricacies of hull design or even the turbulence drag from the cabin balconies but we can optimize several variables to meet the optimal design limits. In addition to keeping the propellers polished and the hull clean, we must focus on minimization of the propulsion by using our asset within its most effective parameters such as trim, ballast, list, and any other metrics that can guide the operations to meet its needs with minimal impact on the propulsion. Nevertheless, we are now entering accountability ambiguity if we are lacking the capabilities of assigning responsibilities of not reaching our energy consumption goals. For example, if we need more power than specified to reach the required speed, we need systems in place to assess if it is due to poor ballasting, unfavorable weather, or else. The need for performance based navigation technologies is evident. Some of the performance based navigation tools are extraordinary and well worth our consideration.
Typical Energy Consumption Sectors
Energy Consumption – Hotel Services & Auxiliary Services: Also on the other side of the energy balance are the hundreds of services that provide habitability and comfort to the people on board. We normally find the HVAC systems at the forefront of energy savings opportunities due to the intricacies of refrigeration systems. HVAC systems can also be monitored to perform at its limits and our metrics must be designed to measure how close we operate to the design capabilities. When considering the lifecycle of a passenger ship the HVAC alone consumes equal amount of energy as the propulsion which, in contrast to the propulsion, runs continuously. Likewise we find also the Auxiliary Services that are at the bulk of our consumption. It is nevertheless the hundreds of circuits that flow down into the service spaces, public areas, and cabins that make up the rest the bulk and therefore extraordinarily complex to allocate singular responsibility for the utilization of the energy resource. The solution in this case is then to diligently analyze the value in measurement technologies that can distribute accountability for the thrift utilization of the energy.
Delivering power to a bulk of consumers is challenging to reduce because of the ambiguous ownership in energy consumption. We must therefore dissect the bulk consumption in strategic segments or sectors that can be effectively monitored for accountability purposes. The strategic segmentation of the sectors is done by running the energy consuming asset inventory against its power consumption characteristics and rate of utilization (hours of operation) and then prioritize the assets to monitor as per the potential return of investment (ROI). Likewise we will be prioritizing the measurement of energy consuming assets as per the potential savings in differential (delta) power consumption. It is critical important to analyze if the “delta” in power consumption reduction which makes up for the cost of installing the metering devices. In other words, if a 500kW circuit or asset, which can potentially run for fewer hours, can be measured at a cost of $10,000 and we expect to curb energy consumption by 3% then it probably makes some sense to monitor while the cost of energy production is $0.15/kWh. On the other hand if it cost $100 to monitor the energy circuit it is highly competitive to do so. Diligent measurement of production sectors, monitoring of consumer circuits, and indisputable accountability of the key performance indicators are the foundations of an effective energy management program.
