Today’s energy costs can be daunting, but there are ways to reduce energy consumption while still meeting process objectives. Equipment load management is a way to extract cost savings in the form of reduced energy consumption from the capital invested in equipment assets. Here, we discuss general principles and strategies for optimizing equipment load management.
Minimizing the Number of Machines in Parallel
One of the most effective ways to reduce energy consumption is to minimize the number of machines running in parallel. This not only reduces the amount of power consumed but also increases the level of redundancy and operating flexibility.
Reducing the Rate of Operation
Another effective way to reduce energy consumption is to reduce the rate at which individual machines are run. This can be done by minimizing recycle flows, which will reduce the amount of power consumed.
Operating at Maximum Efficiency
Operating equipment at its maximum efficiency point is also beneficial in terms of energy consumption. Equipment should be operated at near its maximum efficiency point, as much as is practical. This will help to reduce energy consumption while still meeting process objectives.
Assigning Maximum Duty to Most Efficient Equipment
When operating parallel sets of equipment, the most efficient equipment should be assigned the maximum duty, while the least efficient equipment is used as the “swing” unit. This helps to ensure that the most efficient equipment is always operating at its peak efficiency.
Drivers for Load Management
Pumps and compressors are usually driven by electric motors, but sometimes the motive power is provided by steam turbines or gas turbines. The correct choice of driver depends on whether speed control is beneficial in the application and on the size of the pump or compressor. The overall site steam and power balance should also be considered, as it can have a considerable influence on the economics of driver selection.
Using Adjustable Speed Drives
In many cases, significant savings can be achieved by using adjustable speed drives on pumps and compressors. This allows for flow control to be achieved in different ways, such as throttling the main discharge line, running the pump at full throttle and re-circulating the excess flow, or using an adjustable speed drive.
Calculating Power Consumption
The power consumption of pumps and compressors is a function of flow. To calculate the power consumption for each case (actual, required, minimum), the average flow rate and head for the given time interval should be used. Pump efficiencies should be obtained from the pump manufacturer’s data sheet or from the efficiency data generated during the most recent pump performance test.
Conclusion
Equipment load management is an important way to reduce energy consumption and achieve cost savings. Several strategies and tactics can be employed to optimize load management, such as minimizing the number of machines running in parallel, reducing the rate of operation, operating at maximum efficiency, and assigning maximum duty to the most efficient equipment. Careful consideration should be given to the choice of driver, as well as to the calculation of power consumption. By following these strategies and tactics, energy costs can be reduced while still meeting process objectives.