Let’s Get Technical…Load Side Products
Both Enigin partners and their customers continue to be highly impressed with not only the unique business tools we provide, but also the powerful and compelling benefits of ALL of the four stages of the Enigin – EnergyMaps programme, especially the new Eniscope.
However, many of the questions raised with our technical development team relate to our comprehensive range of ‘load side’ energy saving products namely; iMEC, LESS, ACES & CUES.
I can appreciate that the prospect of being able to offer products that can save massive amounts of energy across such a wide range of applications is very intriguing, but the big question is: How do the products actually work? Are they commercially viable? And what is the underlying technical theory behind these solutions? Is it really possible to save 30% – 50% – 70% or more in energy consumption?
In a nutshell… what Enigin design into equipment could be summed up as ‘intelligence’. In many cases we introduce sophisticated microprocessor based solutions imbedded with unique control algorithms that constantly monitor the ‘work’ being done by an appliance and ensure that the energy consumption is matched exactly to the required demand (which is often variable). Of course the methodology used within say an iMEC controller may be completely different than that deployed within LESS, but the principles of maximising efficiency are the same. We design out unnecessary waste.
For a simple lay-mans understanding of the rationale behind each of the load side products you need to go to the Enigin Corporate web-site where you will find a comprehensive explanation on each one under the Enigin – Energy Saving Products drop-down menu: http://www.enigin.com/products however if you have a thirst for all things technical please continue (you have been warned).
In physics, the first law of thermodynamics is a statement of the conservation of energy. In short, the law states that “energy can neither be created nor destroyed”, it can only be changed from one form to another or transferred from one body to another. e.g. friction turns kinetic energy into heat (radiant energy). In other words, once an appliance has absorbed energy it becomes irreversible and when not utilised to meet a demand (work) then the excess energy will be converted to losses (heat), which is then dissipated into the environment often triggering a further isentropic effect.
Most electrical inefficiencies are converted to heat-loss. In simple terms heat is; “energy in motion” and one of the primary considerations in the design of most of our load side products is not to reactively control or transfer this heat but to prevent it from being created in the first place. Energy consumed by an appliance will create either ‘work’ or ‘heat’ and the objective should be to minimise heat and maximise work (without getting too technical – not ALL ‘work’, however is effective and can often be controlled). For example, you don’t install lights to heat a building and yet that is what much of the consumed energy does (often air-conditioning then has to remove it). To put this into perspective a traditional and still widely used incandescent light bulb produces 10% work and 90% heat.
Electric motors are installed into appliances and production facilities to do a job of work; be that to turn, pull, push or drive something, and yet a thermal image camera will clearly demonstrate that many motors run incredibly (and totally unnecessarily) hot due to the affect of the first law of thermodynamics. Interestingly while this is only one of many factors we consider, the laws of thermodynamics are also at the very heart of both CUES and ACES.
When it comes to motor controllers you will sometimes come across statements like; “you can only save part of the energy that is being wasted” however, while this may for the most part be ‘technically’ correct it nonetheless could be misleading. How so? There is a principle in physics that is not widely known called ‘isentropic effect’, which for the less initiated has to do with equal entropy (thermodynamics). Understanding this principle explains why, in some cases following the installation of a controller like iMEC, a motor can give substantially more energy saving benefits to the consumer than might seem technically possible, thus leading to statements by customers of otherwise seemingly unrealistic savings. This does not defy the laws of physics it simply embraces more of them!
This can be proven conclusively with an Enigin’s Eniscope installation because the isentropic effect is seen across the whole site.
Having been involved personally in the development of several incarnations of fixed speed motor controllers, and having directly or indirectly through partners, distributors and employees been involved in the installation of thousands of units in almost every country of the world over the last twenty years I do have a measure of experience in maximising savings in commercial and industrial motor control applications.
Whilst a saving of 50% is certainly achievable this is by no means the norm and it would be foolhardy to think one should ‘assume’ that every motor is a potential big energy saver. You do well to think in terms of the 10-20% range for old partially loaded motors – many will deliver more. At Enigin we would rather under promise and over deliver! Remember what most customers are interested in is a robust turn-key solution that will give an acceptable pay-back. We recommend you should be budgeting for a two-year return on investment. You can also add weight to the payback proposition if you can clearly quantify significant improvements in equipment reliability following installation. I remember installing 102 units in a foundry and the Managing Director told us he reckons he got his money back in the first month from significantly reduced maintenance costs and increased production. It helps when assessing the benefits on control technology to think ‘outside the box’, rather than just focusing on what’s going on in the winding of the humble AC Induction motor.
So how does the isentropic effect work: It’s really quite simple, when a motor is running under less than full load it will almost always draw more electrical energy than it needs. Remember one of the basic laws of physics is that energy cannot be created or destroyed. So… the ac Induction motor draws more power than it needs… it can’t send the excess back along the cables again because there is more on the way so it converts into other forms of energy primarily heat, in addition to vibration and noise which is then dissipated.
Motors cause excess power to be consumed for any of the following reasons, or sometimes a combination of them all:
- Variable supply voltage on the National grid.
- Over-sizing of the motors at the design/specification stage.
- Variable duty cycle with no intelligent way of adjusting the power to meet the demand.
- The motor running needlessly when it could be turned off.
- Isentropic efficiency.
On the matter of variable voltage on the National grid here is a question for you. If you took two identical single phase electrical appliances; plugged one in at our offices, which routinely has a measurable voltage of circa 245, and one in some remote parts of Europe where the voltage often drops to circa 210, would they both use the same amount of power (kWh)? Of course not! Kilowatts is derived from an equation which includes ‘volts’. Testing a motor in isolation in a laboratory with and without iMEC can prove the Enigin controller has the ability to dynamically adjust the magnetisation between the stator and the rotor, but it can give an incomplete picture if we are not measuring ALL the relevant electrical parameters at site level (rather than just an appliance of motor) along with other influencing factors which could include ambient temperature where the appliance is located.
Think outside the box (or the motor in this case) for a moment… A good example of isentropic efficiency can be seen in many fridges and freezers (probably like the one you have at home). When running an hermetically sealed refrigeration system where the motor is constantly cooled down by the refrigerant coolant, where does the excess heat from the motor ultimately go to? Firstly – into the refrigerant coolant, which means the compressor, has to work longer to overcome the motors losses. It then leaves the compressor and moves to the environment… then what?
A significant determinant on how long a refrigeration compressor runs for is the ambient temperature where it is located. Let me illustrate: Consider for example if you placed a fridge at the North Pole how long would it run for each day? Right, it would never turn on because the ambient temperature is at least the same as or lower than the target temperature of the freezer – OK? Conversely if you placed the exact same fridge in the middle of a desert it would never turn off. Yet as the fridge goes through it’s cycle, we are taking ALL the excess heat from the motor and heating up the very environment that the cabinet lives in so it takes longer to turn off. And there is more… we then have to pay for the air-conditioning system to run longer to keep the building (be it a convenience store, freezer centre or hotel) at the desired temperature. An air-con system is really a big fridge so the whole process starts over again. Remember there are also ‘line losses’ in the cables before electricity even reaches the refrigeration compressor.
Of particular relevance is the fact that a fairly typical air-conditioning unit will use 500 watts of energy to remove every 1000 watts of heat from a building. In simple terms this means that for every 1000 watts a motor wastes it will cost the owner of the building in real terms 1500 watts…
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