A VSD (variable speed drive) is a piece of equipment used to change the speed of an electrical motor. In situations where the water pump supplies too much pressure or flow, a VSD is used to reduce the speed for optimal flow or pressure. Less energy is required at lower speeds and thus the saving. Please note that lower pump speed also results in less pressure and less water flow. In applications where less pressure or flow is not required, a VSD will not contribute to power savings.
Previous energy surveys in agricultural applications has shown that energy savings between 10% and 40% are possible. These surveys were part of the IEE project of the NCPC-SA and the PSEE project of the NBI. Cost savings can be achieved by improved management of the tariff structures, while energy consumption savings were identified on applications such as irrigation pumps, cold stores, packing lines, heating, drying tunnels, buildings, fans, compressed air and also diesel use on farms. These are very technical solutions and trained specialists are available with dedicated measuring equipment to assist in energy saving solutions.
Energy consumption depends on the rate of energy use (kW) and the duration of use (time). A small machine running 24 hours 7 days a week will consume more energy than a larger machine that is only used for a few hours a week. Typical large energy users are cold storage or cooling facilities, heating equipment and water pumps. Look out for equipment that runs during the night and on weekends – the longer time periods means more energy consumption. The energy survey as mentioned in the previous question will identify the large energy users at your facility, which may differ from other locations depending on the size of equipment and the duration of use.
This question has different answers for different places. The best way is to conduct an energy survey (aka energy audit) so that a complete analysis can be made on the major energy consumers and opportunities for energy savings at the facilities. An action plan is normally supplied as part of the survey report to guide the implementation of savings in a structured way. The survey can be repeated at a later stage to identify the next cycle of savings. This is a continuous improvement process. Trained specialists in energy management are available to conduct such a survey for your unique circumstances.
The utility supplier (Eskom or the municipality) has different tariff structures. These tariffs are based on different cost components based on a period (e.g. days), or consumption as measured in kWh, or maximum demand as measured in kVA. By selecting the most appropriate tariff structure for his needs, the farmer can manage the energy use and time periods and thereby reduce the total cost paid for the electricity per kWh used.
Cost savings on energy can be achieved in two ways: 1. Pay less for the energy by using a more suitable tariff structure, and 2. Use the energy more efficiently i.e. do more with less energy.