Energy assessment based upon Motor Consumption

IndustrialElectrical2007

Welcome to CR4. Hopefully you'll find this forum as informative and, at times, as humorous as I do. There are some very good people here.

One of the things missing in your question, perhaps on purpose, is what type of facility you are talking about.

In the area of reducing energy consumption there are a lot of overlooked places that save. Some are very simple and cheap. Some are very pricey and you need to get into the return of investment(ROI) issue in order to sell it. The longer the ROI time is, the harder it is to get done.

When I took this plant over ... actually two small to small-medium plants... our combined electric bill was running right at $95,000 a month. It currently is right at $49,000 and I have almost doubled output in one of the plants. I've reduced gas usage by about 20%.

It all adds up. We had the typical plant lighting... low bay 400w metal halide. Hot hogs. It cost about $150k to put in t6 lighting with sensors in appropriate places but it had an roi of 1.2 years and saved us over 400,000kWh. Lots of areas now have sensors to activate the lighting. Bathrooms, hallways, etc.etc..

Your thoughts on motors are the right direction. If you change out a motor go with high efficiency style. We have a ton of conveyors. Those running all day, every day add up. I've done real load running studies and found so many things oversized. I did a lot of automating and tying conveyors controls to the machines that are feeding them. If a crew goes to lunch and shuts down a high speed wrapping machine...why leave the conveyors running? If I have no product coming down the line, regardless of why...shut off the line. We had 3 lines running the same product in different packaging and this mess of conveyors these ladies had to deal with. Just dumb design. I had the box maker add me a couple different colored dots on the bottom and put an eye on. Send it all down the same line and divert it where it needs to go.

Anyway...there are a lot of areas that can be considered. Also, there are companies out there that specifically do this for a living. These people will be more than happy to come in and do a full real-time evaluation, and work with you to get whatever utility incentives there are. It typically doesn't cost you anything on the front end for them to look and give their suggestions.

Good luck and again, welcome to CR4.

I think conducting comprehensive 'energy audit' is a good proposition for your organization. The exercise includes identifying specific areas of energy losses viz. motive load operating at low power factor, losses on account of lighting, losses in HVAC system etc, among others. To begin with, you can tabulate the load profile of your organization and analyse the system for mitigating losses. Switchman has practically endeavoured to reduce losses and succeeded, I think with more specific information from your end, he may also like to elaborate on further suggested course of action.

Kind regards,

The movement we say savings, it should be sustantial and quantifiable. You have choosen good exercise, but it takes lot of time and appreciable savings may or may not be seen, which should have been taken after major power savings proposals are completed. As a matter of fact your monitoring shall help in reduction of idle running of equipment. You may also calculate motor efficiency and propose for high efficiency motors, where the pay back will be about 1.5 to 2.5 years depanding on inefficiency of present selected motor. Of course for old motors the repair and break down cost also shall be considered. There is a lot of technology available which varies from case to case. If a specific problem is highlighted, you get related solution.

Voltage reduction method is successfull in most of the cases, where you can try at your plant very carefully (Reduce step wise and study motors, then try to reduce further and arrive at optimum voltage).

I think it is better to take up each equiment and analyse. For. Eg. Fans- check the parameters (Volume, draft, temp etc), static efficency etc. Then think of speed reduction, high efficiency fans, with good finance appraisal system.

To what others have said, I'd add that replacing an underloaded motor with a smaller one is unlikely to be worth the trouble. Even if it's 2x oversized, efficiency at 50% load won't be much less than a replacement at 100%, partly because full-load efficiency tends to increase with motor rated power. And an oversized motor runs smoother, cooler and lasts longer.

Cheers......Codey

Thank you for taking the time, I appreciate the comments. I agree with the tone of each of your comments and many of the things you've pointed out agree with observations and beliefs held by myself and my electrical compatriots.

I am of the impression that it takes a very poorly loaded motor (actual load<30% of rated load) for the efficiency losses to bring the ROI to a reasonable payback period (ROI<5 years). To estimate the loading I use power or current measurement. I found some indications on the web that current does not have a linear correlation to load at low load levels. The graph of this trend can be viewed at http://www.loadcontrols.com/whatisaloadcontrol/whatisaloadcontrol.html. This issue would lead to the impression that the motor is loaded more heavily that it actually is when It is operating at low very load. The window for savings is so small I am hesitant to use the current indication as the only basis for load estimation. Does anyone have any insight into this?

Many of the plants are old and most motors will not have instrumentation to measure current. Do any of you use rules of thumb for estimating the efficiency of a motor based upon its age and rewind history?

This company has clearly defined accounting principles which control how power consumption is measured and to which department the consumption is charged. This allows me to easily see which departments are over consuming.

The environment is cement manufacturing each facility will have well over a thousand motors. The equipment is mainly conveyors, crushers, blowers, and fans. The assessments are performed by a team of seven people and so I am focused on measurement accuracy, motor loading, transformer loading and VFD upgrade prospects. I just wanted to add this information to see if anyone has some specific recommendations.