Diesel engine and generator sets (gensets) have been extensively used for standby and remote power generation over the past hundred years. Due to their use for standby power, these diesel gensets are designed to operate in conjunction with the grid, which relates to a fixed speed operation with a 60 Hz AC output. For operation in remote conditions, such as military and disaster relief applications, this fixed speed operation results in limiting the power output available from the engine, as well as the overall efficiency of the system.
The removal of this grid connectivity requirement could result in an increase in system efficiency. At a given load, the engine operates more efficiently at lower speeds, which corresponds to an increase in the system efficiency. This low speed operation also results in lower power output. Knowledge of the load is important in order to determine the most efficient operating point for fixed speed operations.
Operating at a higher power output for a given speed also results in higher system efficiency. The addition of a battery pack will allow for a higher apparent load, resulting in higher operating efficiency. The addition of a battery pack will also allow for energy storage, which allows for a higher operating efficiency, as well as "engine off time". A controlled series capacitor converter should be used to ensure that the maximum power is transferred from the genset to the battery/load. Knowledge of the load and equipment available should be used in order to determine the ideal dispatch strategy.
Overall, operation at the grid frequency limits the efficiency of the overall system for remote operations where grid frequency is not required. The simulated genset had an efficiency of 24% for a 3 kW when operated at 1800 RPM, and increase from the 17% efficiency at it normal operating speed of 3600 RPM. This corresponded to a fuel savings of 3 gallons over 24 hours of continuous operation. When a battery is incorporated into the system, the efficiency of the system will increase for a given output load. For example, the simulated genset has an efficiency of 15% for a 1 kW load, which increases to 24% when a battery is added and charged at 2 kW. / Master of Science / Diesel engine and generator sets (gensets) have been extensively used for emergency and remote power generation over the past hundred years. Due to their use for emergency power, these diesel gensets are designed to operate in the same way as the grid. This results in a fixed speed operation in order to achieve 60 Hz. For operation in remote conditions, such as military and disaster relief applications, this fixed speed operation results in limiting the power output available from the engine, as well as the overall efficiency of the system.
Increasing the efficiency of the diesel engine will increase the overall system efficiency, which is the relationship between the energy into the engine as compared to the energy produced. At a given load, or energy output requirement, the engine will operate more efficiently at lower speeds. This low speed operation, however, will result in a lower power output. Therefore, knowledge of the load is important in order to determine the most efficient operating point for a diesel engine, and the genset as a system.
Operating at a higher power output for a given speed also results in higher system efficiency. The addition of a battery pack will allow for a higher apparent load, or the load seen by the engine, resulting in higher operating efficiency for the engine. The addition of a battery pack will also allow for energy storage, which allows for “engine off time”, or time which the system can provide power silently. Analysis should be conducted to ensure that the maximum power is transferred from the genset to the battery/load. Knowledge of the load and all equipment available should be used in order to determine the ideal charging and discharging strategy for the battery and system.
Overall, operation at the grid frequency limits the efficiency of the overall system for remote operations where grid frequency is not required. A simulation was conducted to illustrate this concept. The simulated genset would save approximately 3 gallons of fuel over a 24 hour operating time when run at of speed of 1800 RPM, as opposed to its normal operating speed of 3600 RPM. When a battery is incorporated into the system, an additional gallon of fuel can be saved over a 24 hour period.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/78374 |
| Date | 19 July 2017 |
| Creators | Wheeler, Kaitlyn Rose |
| Contributors | Mechanical Engineering, Wicks, Alfred L., Nelson, Douglas J., Southward, Steve C. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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