Technology is a sphere that frequently updates itself with new elements and inventions to fit a certain purpose and occasionally replace older iterations in fulfilling a certain role with some improvements and new functions. The shipping industry is a fusion of different technologies which network and combine to move ships, operate port machinery and maintain records.
However, technology runs on power which will bring additional costs and take its toll on the environment as well; along with that, “wear-and-tear” symptoms occur in the sphere of technology and with frequent use, damage and serious accidents would follow. So what is to be done to provide maintenance and be closer to a safe working environment? Such solutions come from MacGregor, (part of Cargotec) Fairford in 1980s and NASA in 1970s in the form of changes to existing machinery; “Soft-Start” technology.
“Soft-Start” technology was tested on various machines from hydraulic hatch covers to pump jacks with different power requirements, degree of wear on parts and physical pressure. Another idea of “Soft-Start” technology is to reduce peaks and stresses on mechanical and hydraulic components due to the fact that a ship has a closed electrical system where current peaks may cause disturbance elsewhere in the system. “Soft-Start” technology reduces starting peaks to 4x a motor’s nominal running output power; replacing standard solutions. This is operated by a remote which allows startup and shutdown remotely.
Operation of this particular variant of “Soft-Start” requires 2x people for hatch cover operations. Safety measures also include an emergency stop function which is activated; shutting down the hydraulic pump unit which also requires confirmation upon activation; replacing older convention. One advantage of this process is the slowdown of chemical aging of oil and prolonging lifecycle of components along with boosting energy efficiency.
Aside from hydraulic machines the “Soft-Start” technology is also used in:
- Power units on bulk carriers.
- Cargo ships
- Pump jacks and onshore oil wells requiring mechanical lifts.
- AC current induction motor controlling pump jacks.
“Soft-Start” technology creates more efficient operations but what were the main problems before this technology was discovered? Firstly, AC induction motors are designed in a way that they run on highest efficiency when load is between 75-85%. As load is reduced the overall efficiency of a motor declines and losses inherent within the motor contribute to the inefficiency of the whole system. Load dropping below 30-40% decline efficiency which shows that reducing certain losses in this portion of the loading cycle improves efficiency.
The losses present in AC induction motors are:
- Load losses that relate to heat produced by electrical current flowing in the conductor.
- Stray losses caused by higher flux density harmonics due to slotting effects into the bar rotor currents and skewing.
- Mechanical losses caused by friction in bearings, belts and cooling fans.
- Iron/Excitation/Magnetising losses are voltage-related and constant regardless of load .
Leading back to machinery, motor driving the crank in Pump Jacks experiences different loads throughout the cycle. One part of the cycle has the motor fully loaded/overloaded and then, as the counter weight begins to drop the load declines. At low-load, the iron losses still fixed and the amount of energy supplied to the motor is higher than required.
As mentioned above NASA presented one of the solutions in the form of an algorithm for reducing iron losses in a single phase which was used in Apollo rockets. Fairford electronics also developed a 3-phase digital energy saving soft-starter mechanism; the IERS/Intelligent Energy Recovery System which was included in a BOXER pump jack controller which reduced iron losses on fixed speed AC induction motor which reduces amount of energy consumed when motor is lightly loaded. This is done by detection of running power factors. Power factor drops when IERS detects and reduces voltage and current to the motor to only supply exact amount of energy required to maintain full speed; reducing power demand by motor improved fractional/load power factor.
Finally, to conclude this analysis of power consumption, the average power demand of a motor over 4 cycles w/o energy saving equipment is 25.20kW while WITH energy saving it is 19.50kW.
Yielded kW saving of 5.6kW equates to 22.63% energy saved.
