4 Task C: Extended Product Approach (EPA)
4.3 Performance parameters
The performance parameters can be determined according to the different approaches explained in previous sections. In a Product Approach the focus is on how the product itself performs. For water pumps the overall performance and energy use is dependent not only on the pump itself but the other components it is coupled with and the system it is placed in. Therefore, the performance of a pump can also be seen from an Extended Product Approach or a System Approach .
If the Product Approach is used for ecodesign regulation, it can be ensured that only energy efficient pumps are placed on the market, but that does not ensure lower energy consumption. The energy consumption of pumps depends on factors such as the rotational speed of the motor and the system curve of the pump system (i.e. its flow and pressure profile). If the pump is connected to a fixed speed motor, the system will only be energy efficient if the pump is used in a constant flow system. With a VSD (or another mean to adjust the speed, i.e. continuous control) the rotational speed of the motor can be adjusted to the demand in a variable flow system. This will reduce energy losses in the motor from operating it constantly at full speed, as well as the losses occurring in the hydraulic circuit when the motor is operated at full speed (without VSD) when only a reduced flow is needed (illustrated in Figure 6). Theses losses typically occur when a valve is used to throttle the flow, as illustrated in Figure 7. Energy consumption is proportional to the pressure; so lower pressure means lower energy consumption66.
The process for implementing EPA in the EU regulation work progresses in two parallel tracks. Europump has developed a guide to create a common understanding of the subject and to guide the process towards developing actual standards. In parallel the European Commission issued Mandate 498, aiming to create harmonised standards covering an EPA.
Currently, two standards have been developed: FprEN 17038-1:201767 and FprEN 17038-1:201768, and another is on the process of being developed.
In the Europump guide, an EPA is defined as a methodology to calculate the Energy Efficiency Index (EEI) of an Extended Product (EP), which incorporates load profiles and control method for a set of physical components.
Following this, Europump defined the extended pump product as a pump driven by an electric motor with or without variable speed drive with given load profiles (see Figure 6).
66 Extended Product Approach for Pumps, A Europump Guide, October 2014, Europump..
67 Pumps - Methods of qualification and verfification of the Energy Efficiency Index for rotodynamic pump units - Part 1: General requirements and procedures for testing and calculation of energy efficiency index (EEI)
68 Pumps - Methods of qualification and verification of the EnergyEfficiency Index for rotodynamic pump units - Part 2: Testing and calculation of Energy Efficiency Index (EEI) of single pump units
Figure 6. Illustration of operation with fixed speed pump and variable speed pump69.
Figure 7. Illustration of system losses and improvement before and after installing a VSD, when low flow is needed.
69 Extended Product Approach for Pumps, A Europump Guide, October 2014, Europump
PumpPump
Coupling Electric
Motor Electric
Motor
Desired work
Mains
Hydraulic circuit NoVSD, motor at fullspeed
Valve Desired flow, high pressure
Desired flow and pressure Destroyed
energy
Mains VSD
PumpPump
Coupling
Electric Motor
Electric Motor
Desired work
Hydraulic circuit VSD, motor at reducedspeed Desired
flow and pressure
Water pumps can be divided into two groups according to the intended system:
• Constant flow systems: where the pump is pumping at best efficiency point (BEP) with slight variations of the flow rate around the nominal value; and
• Variable flow systems: where a widely varying demand for flow rate and water pressure or differential pressure has to be generated by the pump.
Note that ‘Constant flow system’ in this context does not mean that there is no variation in the flowrate, it means that there is no variation in the desired flowrate and therefore there is no need for controls such as a control valve. A typical constant flow system is draining or filling of a reservoir, where there is no need for controlling the flowrate, but the flowrate will fluctuate as the head from the reservoir is changing.
For both types of systems typical and standardized flow-time profiles and reference control curves are defined and used to calculate the corresponding energy efficiency. In section 4.4 this energy efficiency calculation will be explained in more detail. The flow-time profile describes the percentage of time a certain flow is needed in the system. The reference control curve is a standardized control curve, which describes the desired head at the flows defined in the flow–time profile.
Figure 8 and Figure 9 show the flow-time profiles for constant and variable flow systems as they are defined in EPA for Pumps, A Europump Guide, October 201470. Notice that the flow-time profiles are defined as step-functions. It is assumed that the pump has the correct BEP compared to the application, so that in variable flow system the nominal flowrate of the pump is equal to the maximum required flowrate for the application (Q100%).
For constant flow applications it is assumed that BEP matches the most frequent operation point (Q100%). This means that for constant flow applications the flowrate varies around BEP being both lower (Q75%) and higher (Q110%).
The flow-time profiles are different for constant flow applications and variable flow applications. Setting a clear division for constant and for variable flow requirements makes it possible to compare how well pumps are performing in each application.
Figure 8. Flow-time profile for constant flow systems65.
70 Ibid.
Figure 9. Flow-time profile variable flow systems65.