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Norbert Vasen's picture
CEO Birdseye Energy Consulting GmbH

I am on a quest to bring more Energy Managers into industry. Energy Efficiency is behind on Renewable Energy and that is because it is less exciting (is it?) and labour intensive (each situation...

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Transform your transformer

image credit: https://transformers-magazine.com

Can a transformer fail? See the picture. 
The lifetime of a transformer is between 25 and 40 years. How old is your transformer? When it is more than 20 years old, it is very probable that today’s transformers are much more efficient and will remain cooler. Remember that you can deduct them for a long time from the taxable profit.

Can I save much energy with a better new transformer? 
Yes, you will save money for many years in the future! 
If the future doesn’t interest you especially, you can always discount future savings in the formula for Net Present Value, to express that. See my last article about financial parameters. Especially with long life investments like transformers, the Simple Payback Time is a bad parameter to adopt.

The USA energy agency EPA tells that significant total life time cost savings are obtained if the new transformer is chosen BETTER than the law requires.

A transformer has an efficiency curve, telling how much % of power is transferred with the load is N% of the nominal value. It is good to look to your daily power demand curve and if there is some region where this power is often included, and match this with the power of maximum efficiency of the (new) transformer. So if you are often between 700 and 800 kW, choose a transformer that works well in this range. If you have more of these regions, work sample during the night you are mostly around 300 kW, it can be a good idea to consider two transformers. This will also make you more fail proof.

The efficiency of a transformer depends also very much on the power factor of all the consumers together, so please adopt power factor correction! This is already in itself a big money saver.
 

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Matt Chester's picture
Matt Chester on May 3, 2021

How old is your transformer? When it is more than 20 years old, it is very probable that today’s transformers are much more efficient and will remain cooler.

At what point in the old transformer lifetime does the calculation switch from 'getting as much value as you can from previous investment' to 'you're losing out on even more value by not converting before the end of transformer life'? I imagine this is very much a case-by-case basis, or is it true that it's more uniform that upgrades for certain age transformers are always worth it? 

Norbert Vasen's picture
Norbert Vasen on May 3, 2021

Hi Matt, that is a good question, which shows how Energy Efficiency is a tailor made job and why I am in favour of more Energy Managers in the society. Nobody today has time for this kind of questions and Energy Efficiency remains a dream!

If the old transformer was already low quality when it was purchased or when it is working in bad conditions (overload or "underload"), or when modern transformers are just so much better, then the gap between old and new is bigger and will justify earlier replacement. Therefore it is necessary to calculate the residual value of the old transformer and compare it with the possible savings during the corresponding period (from now to end of life). These potential savings may be larger than the residual value and in that case you say goodbye to the old transformer.

Also a rebate program from the government can be a good moment to anticipate the replacement.

It can still be interesting to keep the old transformer together with the new transformer, for example to increase redundancy. It might then be used only during peak demand (a few hours per week) so that the lower efficiency is not so important. This sharing of the peak demand between the old and new transformer will have the benefit that you may choose the new transformer really precise in function of the average load and not (as usual) in function of a maximum load that might never occur.

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