1st November 2011
The Motor Driven Systems (MDS) Conference being held at St. Johns Hotel, Solihull, on 9th & 10th November 2011, will examine how a systems engineering approach to designing motor driven systems will result in the achievement of greater energy savings.
Within the MDS Conference individual elements of a system – pumps, fans, motors, drives and compressors – will be addressed to highlight best practices, new technology and innovative ideas designed to achieve those enhanced energy savings.
Touchwave Media provides a synopsis of what will be discussed at the Conference within each product area, and having previously addressed Pumps, Motors and Fans we now look at both Drives and Compressors.
Co-ordinating motor drive systems for best efficiency
To achieve the best possible energy savings/efficiency from a fan or pump infrastructure, it is an absolute requirement that Variable Speed Drives (VSDs) are used. VSDs, combined with high efficiency motors, enable a fan or pump system to be optimised to the best operating speed for the Duty, rather than being restricted or compromised by the use of a fixed speed design.
This paper will show, by way of example, where the use of VSDs can enable the compromise of a fixed speed design to be avoided with subsequent energy efficiency benefits.
1. A fan design that has poor efficiency that will never benefit from variable speed operation
2. Multiple pump operation versus single pump
3. Higher operating speed than mains frequency nominal
The metric for these examples will be the ‘Cost of Energy’ in kWhr per cubic metre, using this metric, the benefits, or detriment, of particular fan/pump scenarios will be demonstrated
From this it is hoped that the use of VSDs will be shown to assist in the complex interaction that is design, to arrive at an optimum solution to end user clients.
Optimisation of drive system energy efficiency
The global optimisation of energy efficiency of various processes in industry, building automation and civil engineering is a complex exercise involving a multitude of components. A global optimization is not easy, as the decisions on component selection in various parts of the energy flow (specifically electric energy) are undertaken by different actors, who do not necessarily communicate sufficiently. Thus it is easy to optimise some part of the total energy used, but create a globally suboptimal solution.
The components and devices involved in optimising electricity flow and usage start with the prime movers – generators , then transmission and distribution systems, power distribution , drives and motors and finally the actual working machine that change state or location of material for specific purposes. The final requirement is that this process should be as efficient and cheap as possible.
A typical drive system – from the final user’s point of view, – consists of a motor and a drive and the power supply for this. An analysis of the developments in terms of energy efficiency will be presented for the motor and the drives (introduction of new legislation for motors, efforts to create similar requirements for drives) as well as technical developments focused on energy consumption are presented. The relationships of various parameters to the energy efficiency and the cost of the product are examined – typically switching frequency and its relationship with the motor efficiency, the improvements in energy efficiency reached with new drive components and topologies etc.
Following up – the influence of harmonics on cable and transformer losses, stretching all the way to the generators will be discussed. A short discussion on optimal cable sizing will also be done – examining the different priorities in choosing cable size.
A presentation of the relative effects of various actions in optimising the energy use in comparison to the relative costs of the action rounds off the presentation.
Drive chain management as part of a best practice approach
It is becoming increasingly well known that motor driven systems account for around 2/3 of the electrical energy consumed by industry – and are the largest single consumers of electrical energy overall. Additionally, most end users have already engaged with energy efficiency programmes. However, very few users have adopted a truly systematic approach to energy and cost reduction which could dramatically multiply the cost savings – this paper therefore seeks to;
- Provide a clear evaluation of complete “drive train management”
- Define the relative importance of motors, mechanical drives and electronic variable speed drives
- Highlight many of the most common mistakes
- Position “drive train management” within the context of a systematic approach to energy management and the recommendations of important standards such as BS EN 16001
- Provide clear technical and commercial benefits of a systematic approach
- Identify new technologies and strategies to maximise the benefits of complete “drive train management”
Energy optimisation in air compression
Electrical energy in Europe for Compression Air Systems (CAS) in Industry accounts for almost 100 TWh. Including leakage and the incorrect use of compressed air, the potential in terms of energy saving, has been estimated to be 30%. Using optimised compressors, specifically conceived for energy saving could offer potential energy savings estimated at close to 10%, which would represent 50% of the European Energy saving goal by 2020 (“20-20-20” EU Directive) if CAS is considered as a specific sector.
Sliding Vane Rotary Compressors (SVRC) show previously unforeseen potential in terms of energy saving due to some intrinsic features specifically related to the principles of the working conditions of the machine and which do not strictly apply to other types of rotary compressor.
As we strive for energy savings and CO2 reduction the inherent efficiency advantages of these machines increases the importance of developing this SVRC technology,
A complex reconstruction of the pressure inside a cell was carried out using multiple piezoelectric pressure transducers positioned within an existing commercial SVRC. The data obtained represented an innovation in the sector and thanks to comprehensive mathematical modeling previously developed by the Authors; the theoretical handling of the pressure measured allowed a detailed examination of the thermodynamic aspects of the closed volume compression phase.
In this paper the Authors refine the mathematical modeling of a SVRC focusing on energy consumption:
Main issues of this advancement are.
a) Filling and emptying process of the cells made by a quasi-propagatory modeling, optimised for the discharge phase;
b) Blade settings which are not radial, so the blade motion moves according to a given angular inclination respecting the geometrical constraints;
c) A complete derivation of a new blade dynamics modeling was considered allowing a more precise value of energy lost due to friction to enhance the main SVRC design parameters.
The model has been used in order to deal with:
a) Maximisation of the air mass inducted by the machine, having fixed the stator and rotor geometry, as well as the inlet and exhaust ports. Leaving as free design parameters, the eccentricity, and the associated inclination of the blades (slots), taking into account the real slot and blade dimensions, and, so, the possible geometrical interferences;
b) The optimisation of the specific power required to compress the air (W/kg/s), having fixed a downstream pressure in the line.
A validation with actual experimental data is presented based on direct measurement of the indicated and mechanical power.
The MDS Conference will take place at St. John’s Hotel, Solihull, on 9th & 10th November 2011.
For further information and delegate booking details please contact Andrew Castle, Event Director at Touchwave Media on 07785 290034 or by email at andrew@touchwavemedia.co.uk.
