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Every day we are hearing “energy saving” expressions but what does it really mean, specifically in the industrial automation field?
- How much savings we can have?
- Is it a fixed value or calculable?
- What are the different criteria that effect this concept?
- In what kind of applications is it valid?
- Are there any tools/software to take care of this task?
To give you a clearer picture, I will first try to explain what “energy savings” is not…
No, it is not energy efficiency
The first thing that comes to mind is the energy efficiency chart when I want to purchase home appliances or a muscle car, with G level for fun we don’t care, but this is not the case for different automation products (PLC, HMI, VSD…) that uses some energy for supplying/running internal circuits and it could be different from brand to brand and also product to product.
No, it is not mechanical life cycle
Although we are increasing the life cycle of gears, bearings, welding… by using Variable Speed Drives or Soft Start-Soft Stop units and prevent the mechanical shocks and vibration during start up and stop, it is difficult to have precise mechanical life time calculation and related saving.
No, it is not Telemetry or web-Visualization
Even though by remote connection to the automation products which are located in the field we can save some money (travel, fuel… costs) and time by handling debugging and monitoring from far distances via different medias.
No, it is not Reactive Power (Q, kvar)
Although by using Variable Speed Drive we can improve the Power Factor (Cosɸ) close to 1 by internal capacitors of Variable Speed Drive and automatic regulation and consequently power factor correction by capacitor bank is not needed any more.
Yes, it is Active Power (P, kW)
In variable torque applications such as Fans or Pumps that nominal torque at startup is not needed and the resistive torque applies to the asynchronous motor’s shaft gradually, in parallel we can decrease the driven torque/active power when it is not needed in this way saving some energy that is active power is possible.
Yes, it is calculable
Based on load profile, number of working days per year and hours, cost of electricity (kWh)… we can calculate it; let’s have a look at a practical example:
How to calculate Energy Saving
A 37kW Fan needs to supply air during 10h/day for 250 days per year with the price of the power at 0,164€/kWh
- The cost of running that Fan at full speed will be 15170€
37kW x 250days x 10h x 0,164€/kWh = 15170€
If the Fan only runs:
20% of the time at 100% of full load means 20%*2500 h= 500 h
The cost: 37 kW x 500 h x 0,164 €/kWh = 3034€
50% of the time at 80% of full load means 20%*2500 h= 1250 h
The Cost: 37 kW x 1250 h x(0,8)^3 x 0,164 €/kWh = 3883,5€
30% of the time at 60% of full load means 30%*2500 h= 750 h
The Cost: 37 kW x 750 h x(0,6)^3 x 0,164 €/kWh = 983 €
- Total Costs: 3034€ + 3883,5€+ 983€ = 7900,5€
- The cost of running that Fan with a VSD will be 7900,50€
52% in Saving
Eergy Saving = 15170-7900.5=7269,5 €
Summary:
- Energy savings means active power savings and consequently affects the Apparent power (S) as S= √ (P^2+Q^2)
- The level of savings related to the working time and load profile, cost of electricity (kWh), cost of the product & installation so, it is not fix value.
- In variable torque applications like fan & pump that reduce the duty cycle it is possible to implement the energy saving concept, but in constant torque applications that nominal torque at asynchronous motor at start-up is needed… this concept is not feasible.
- Less foot print by reducing CO2 emission
- The Variable Speed Drive suppliers usually providing such software that is very nice in case of fast calculation and reporting for management level to make investment decisions.
I hope now you have a clearer picture of what is the basics of Energy Savings calculation software in industrial automation field.
Conversation
Jacques Schonek
10 years ago
Interesting post.
I fully agree that Energy Savings are related to Active Power (kW), but I would suggest to mention explicitly Active Energy (kWh) as the most relevant value.
In addition, the given example seems an over-simplification, as it compares two different operating modes: one mode where the air flow is always at 100%, and one mode where the flow is reduced. A more relevant comparison would be between two different methods of flow control: mechanical device with motor at full speed vs. variable speed operation.
By the way, please note that standardized notation of power and energy units are kW, kvar, kWh.
Aidin Aliyarzadeh
10 years ago
Dear Mr.Schonek,
Thanks for your valuable time to read the blog and your comment.
Regarding to blog frame rules I tried to write it as simple and generic as possible that transfer the concept to the people who they do not have deep knowledge about this subject that’s why I tried to just highlight the related concept and point out on the fundamental calculation of Energy Saving software available in the market moreover, electricity bill issues by the supplier measures/shows the active power (P) consumption not energy, so people can have a references for comparison.
I will take your advise into the consideration about capital or Non-capital alphabets in related unit measurement.
Thanks again
Aidin Aliyarzadeh
Hussain Ahmed
10 years ago
Really like the article: best ever seen so far to explain the idea of energy efficiency.
Aidin Aliyarzadeh
10 years ago
Dear Mr.Ahmed,
Thanks for your valuable time to read the blog and your kind comment.
I am happy that you have found it helpful/useful.
Thanks again for your encouragement comment.
Best Regards
Aidin Aliyarzadeh
Jacques Schonek
10 years ago
On my personal electricity bill, only active energy (kWh) is mentionned, not active power. It is important to consider the duration of power usage, not only the amplitude.
By the way, your calculation example for energy savings is definitely based on energy (for example: 37kW x 500h).
Aidin Aliyarzadeh
10 years ago
Dear Mr. Schonek,
Thanks for your professional comment…
You are completely right Sir. That’s why I tried to simply transfer the saving concept by active power in the first part and second calculation part base on energy concept.
Some countries/suppliers issuing the bills base on peak period (mid, high or low) consumption and also winter/summer time to implement different tariff.
Thanks again for your valuable time to read/write.
Best Regards
Aidin Aliyarzadeh
Victor
8 years ago
Interesting article. Can you make the connection between Energy saving & Cost Saving versus Energy Efficiency & Cost Efficient?
Aidin Aliyarzadeh
8 years ago
Dear Victor,
Thanks for your valuable time to read my blog and write feedback.
Happy to hear that you find it helpful/useful.
To reply your question:
For calculating the cost saving you need some parameters such as: load profile (should not be 100% fix in all working period), electricity cost, investment cost (when you install a variable speed drive instead of traditional motor start ups such as: direct on-line or star-delta).
In my fan example you can see that as you consume less active power in an hour you could save more, that is applicable for variable torque applications such as fan and pump.
In Schneider Electric we have a free of charge ECO2 software that calculates it and report you. The principle of the software is based on active power as I have mentioned in my fan example. The software could save your calculation time.
You can download it from below link:
https://www.schneider-electric.com/en/product-range/7589-eco2-0/?parent-category-id=5100
If more information is needed, please do not hesitate to contact me.
Sincerely Yours
Aidin Aliyarzadeh
Nisha
7 years ago
Hi Sir,I am so excited and happy to read this. A brief knowledgeable content regarding energy efficiency… I get more than I expected here. I like the way you explain everything in your own simple style and I felt no more complicated. Please…..I will expect more posts like this.
Thank you
Aidin Aliyarzadeh
7 years ago
Hello Nisha,
It is my honor that your read my blog and happy that you find it helpful.
As you correctly mentioned, it should be good connection between theoretical and practical subjects to make the case crystal clear which I am trying to implement this concept/s in my blogs, tutorials, training exercises etc.
As soon as I find new interesting topic for sure I will write new blog.
You may find my other blogs in: https://blog.se.com/author/aaliyarzadeh/
You may find my SoMachineHVAC programming tutorials in Schneider Electric official YouTube channel: https://www.youtube.com/results?search_query=somachinehvac+aidin+aliyarzadeh
Sincerely Yours
Aidin Aliyarzadeh