Amanda, this is a great story. The solution saves money on energy and the solutions used to keep costs down are really innovative. I worked with an electrical contractor once who, when show a Zigbee based building controll system said, wait a minute now. He was seeing his business going away, since wiring is a major cost and very labor intensive.
The other aspect of this solution that many people overlook is the need (or lack thereof) to get a PC to run the system. The whole premise of clould computing is that businesses have to purchase computer equipment that meets peak needs, while they end up spending a lot of time running at less than a quarter of their capacity. This is even more true of PCs in offices. Hats off to the Building Maintenance Supervisor.
This was a very interesting use of a PLC and interfacing to cycle block heaters. One thing that sort of irritated me was the initiative to save money was only driven when taxpayer funds became short. Why is it government entities only come up with good solutions when the taxpayer is fed up with feeding the behemoth?
Kudos to the bus guy! I now have at least one example of government doing something right.
Now if the spendaholics in DC could find ways to save money???
20 years ago whilst working for Idiot Blinking Management I realised running the cooling compressors on a walk in thermal chamber that was designed to be able to reach -80 and +150 C when it was only ever run at +75 to condition Hard-Drive casings was just plain stupid. I discussed it with my line manager, and his manager, was given a small budget and designed some really simple timer relay circuits, a PLC would have been nice, but back then simplicity and low cost was required.
We installed it on several different chambers and over several months cut power costs significantly. So we converted the whole plant, and not just power but wear saving soon mounted up. When my idea was put forward for the I'm Bloody Marvelous employee idea's scheme the plant managements answer was it wasn't worth it, and I was 'only a fu*king contractor'. 6 months later one of the plant managers put it in under his name and 5% of the savings made by modifying every thermal chamber world wide owned by Incredibly Badly Managed was his...
I hope the supervisor gets at least some credit for this work, beyond those in the technical field, and it's uptake by others, but somehow I doubt those in charge will care.
This is indeed an interesting application of PLCs, but I am puzzled as to why it had to be that complex. That may be due to having the heating outlets tied to the lighting circuits, I suppose, which may have been cheaper when the lot was first built. Otherwise, a simple system to switch on the power only when the ambient temperature demanded it and only at the times needed would probably have been much less expensive. But possibly there are a few details not mentioned that would have mandated the PLC choice.
William K. I agree that the PLC may have been a little overkill, but that there may be other requirements or functionality not detailed in the article. I wonder if a simpler timer circuit, and possibly a temperature switch in the circuit with each block heater could give similar savings.
Certainly a temperature switch that was fairly accurate could avoid unneeded heater operation, no question about that, and a time switch could also eliminate heating until it was needed. BUT all of those operations require a bit of attention and some intelligence, and those are sadly lacking in maany organiizations these days.
I too didn't get some of the details. Each PLC has one 20A relay, but the details made it sound like there were more than one outlet in each junction box. Were multiple block heaters controlled a single PLC? Were all outlets on that box switched on/off at the same time by that one single relay?
Jim, it has occurred to me that the solution using PLCs was done by an outside contractor. It is entirely possible that nobody in the organization had the required skills to implement an X10 solution, or to wire up anything, much less design it. The problem I have is realizing that so many people have no concept of anything that is technical. They lack the expertise to put oil in their cars engine or even air in the tires. They don't realize that things need to connect to a power source if not using batteries. It would seem that our public schools need to alter what they teach so as to provide everybody with a better chance of being able to help themselves in real life. Of course I am sure that the educators will claim that they already do that, or that the standardized testing does not allow time for that.
High school tech centers are chartered with teaching students about various technical fields such as welding, electronics, CAD, automotive repair, and industrial maintenance. Upon taking these classes, students will have good direction to take for careers to pursue after high school. The PLC solution would have made a good project for the electronic students to spec out the controller and all of the engine block heat management system components. Putting theory to practice is a good way to insure knowledge has be obtained by the students.
@MrDon, In this area the school maintenance people and the bus drivers are highly unionized and so there is a huge element of "That's not my job" that gets in the way of just about any suggested change that would improve almost anything. So seeing that attitude has definitely reduced my thinking that our local staff would be able to complete such a project, or willing to even consider it.
And while it certainly would be an educational project for students, although not to include the actual installation. But designing the system after determining the requirements would certainly be a good exercise. BUt the physical implementaion of such a system would indeed require a familiarity with a lot of things never covered in classes. I have had to fix several systems that had been created by educated individuals with inadequate practical experience, and the job was never fun.
Valid points. You hit the nail on the head in terms of projects for students: the instructor or teacher must have real world experience to guide the classroom to a successful conclusion. Practical knowledge and hands-on experience is vital to the project's success and the students enjoying the assignment.
The concept of automating the engine block heater management system allows the automation to turn these electrical devices on/off based on event inputs like temperature changes and time of day. The PLC engine block heater management system is quite complex in design. A timer system will not be able to manage the input events mentioned alone without some type of software. A central PLC helps in managing these events as well as turning on the heaters at the appropriate time. Future revisions for the system can be to alert maintenance workers the heaters are on energized and the time of day via a text message sent to their smartphones. A basic timer system would not allow future expansion based on new requirements.
William K; Everyone can't know everything, but some gaps seem surprising. I had a disagreement with a mechanical engineer over whether nitrogen was heavier than air - from my memory of the periodic table, nitrogen is 7, while oxygen is 8. Thus nitrogen is lighter than oxygen, and since air is 80% nitrogen and 20% oxygen, nitrogen cannot be heavier than air. The engineer was sure that I was wrong and instructed me to do some research and then come back and apologize. I was surprised that an engineer didn't know the periodic table.
Good point GlennA. That's why I'm happy of having studied Chemical Engineering. Even when I have worked in project engineering mostly during the last 35 years, and I really love mechanical eng. aspects, the chemistry knowledge has proven very valuable to me many times, and helps undestanding materials too. The key in this matter you are commenting is about the capability of understanding a wide panorama of engineering subjects. That's why I feel happy of notbeing too specialized, and always trying to keep as versatile as possible. For me, engineers should become multi-disciplinary before becoming too focused into a too narrow field.
Years ago, I was attending an international seminar provided with an excellent simultaneous translator. It happened that the gentleman doing the translations was blind from birth, and was a true multilingual person. During a coffe break, he approached the coffe table and I felt the sincere impulse to congratulate him for his linguistic and technical knowledge (he had not studied any technical career, but he became so familiar doing technical translations that he speaked like a versed engineer!). So I asked him about his secret, saying to him: How did you learned so many languages and how did you achieved such a good command of the technical terminology?
He responded with a very charming answer, He said:
"Well, I don´t really SEE much TV, so I have some time to keep studying, And you know what, the tough one was about the third and fourth new languages... after those, every new one I learned was easier and easier! Maybe because one starts to use the knowledge of the already learnt ones to understand the new one that you are trying to learn... That would be..."
That admirable capacity of joking about his own disability, and at the same time share his viewpoint made me admire him even more. In engineering (and in many other fields, I guess, like medicine) this concept applies very deeply, so I'm convinced a true, died-in-the-wool engineer should be as versatile as possible, and that a multi-discliplinary approach even helps in finding when an specialist is not understanding the problem or becoming lost. And while it is absolutely true that "Everyone can't know everithing", the current trend towards overspecialization is not producing better designs at all, and is the main reason "Made by Monkeys" is so enlightening!
In respect to the Buses problem, my suspiction is that the common type of engine heater is not too efficient. Unless the applied power is large enough, the required heating time to reach the desirable engine block temperature is going to be longer, therefore increasing the overall thermal loses to ambient. I don't know if there are 220 VAC engine block heaters that could be more effective than 110 VAC ones. If one considers an smaller power heater, there would be a point where the lost thermal energy equals the suppied heating power, with no benefit but still consuming power during more time. Maybe a more powerful heater, fed at 220V would be still more effective and energy efficient (consider the wiring losses would be lower at 220V, in view of the wiring lenghts). I would revise this aspect in addition to the intelligent energy administration already done in this case. Amclaussen.
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