Most of the customers I work with design small systems, or smaller pieces of larger systems. Occasionally I get to see an end product: a car, an airplane, a mockup of the International Space Station to name a few. Most of these systems are built or assembled in one location, then put to work in another. In other words, the systems most of my customers work with are portable in a very general sense.
On the other end of the scale – what I call Big Engineering – are systems whose pieces may be designed and manufactured at multiple locations, but when the parent system is built, it lives and works in a fixed location throughout its serviceable life. Think large industrial sites. My sister is an engineer at just such a place – a coal fired power plant.
Power plants are some of the biggest industrial sites on our planet. Get beyond a handful of kilowatts and the space requirements are almost mind-boggling. Generating electricity, no matter the method or amount, requires a physical footprint proportional to the number of watts generated.
My sister works at the Intermountain Power Plant, which sits on roughly 4600 acres of high desert acreage in Central Utah. It runs two turbine-driven 950 megawatt generators. The footprint of the turbine + generator room is roughly the square footage of a medium-sized shopping mall. Everything else at the site is dedicated to either making or keeping the turbines and generators running and generating electricity. The plant is one of the biggest of its type in the nation.
My sister recently took me on a tour of her plant, which I thought would keep us busy for maybe an hour. But six very interesting hours later we turned in our hard hats and safety goggles, and headed home. During the tour, we drove and walked to areas not on any normal plant tour. She explained in interesting detail every phase of the generation process, from when the coal is dumped onsite from train or truck, to when the remains of spent coal are transported by conveyor belt to a remote corner of the site. While I am not fluent in power-plant speak, it was fun to talk engineer-to-engineer about electricity, our common technical language. There are definitely worthwhile perks when your sister is a lead engineer at a power plant.
Coal-fired power plants are simple in principle: coal makes fire, fire boils water to make steam, steam is collected under pressure and channeled to the generation room where it turns the turbine that turns the generator to create 3-phase electricity. The electricity is then routed to a big transformer (my sister’s baby) where it is stepped-up to a mind bogglingly large number of kilovolts before being converted to DC and shipped to Southern California. Yep. Utah residents very rarely benefit from any electricity generated at the plant. It all goes to help power California communities. As is often the case, however, what is simple in principle often gets pretty complicated when you peek under the hood. You might think a system that burns coal to boil water to make steam to spin a turbine to turn a generator is simple. Nope. Within the power plant are essentially three separate, complex systems: fire, steam, electricity.
The fire system tracks fuel from when it arrives on site to when waste from burnt coal is sent out to the ash bed. Coal is pulverized to dust, then mixed with air to create a highly combustible fuel that fires in what is essentially a big boiler. Once the fuel is spent, the remains are filtered through a multi-step process to mitigate air pollution. Some of the ash gets recycled at a local cement plant; the rest is piled on spare acreage.
The steam system is the middle process, converting heat from the coal to pressurized steam. Lots and lots of water is moved around the plant by motor-driven pumps of all sizes. It is a great example of a pretty efficient thermodynamic system at work. Water is transformed from liquid to gas then back to liquid again. And sometimes ice enters the process if temperatures dip far enough below freezing.
All of this leads up to the electrical system. Pressurized steam drives the turbines which spin the generators to create 3-phase electricity. All of that juice is routed to a big transformer and sent to a second facility not far away to get converted to DC for the trip to the West Coast. The combined turbine + generator units are massive (note the picture), as are the transformers. Despite their size, however, there is barely a vibration in the generation room. A good thing, too, since even a small vibration could lead to some pretty serious damage.
One recurring thought I had during my tour was “How did someone figure thus out?” The short answer, of course, is “engineering”. But that may be too simple an answer. The real answer is “iterative engineering” which is how some of the most elegant system solutions are found. And while some of my tour questions appeared complicated, many of the solutions were elegantly simple. Even though a process seems complex, it is often built on a series of very simple steps or sub-processes.
I have often wondered whether power plant design could benefit from simulation-based, multi-physics modeling and analysis. After seeing a power plant in action, I believe the answer is yes, without a doubt. It is hard to appreciate what goes in to making the lights turn on in your house until you see all of the power plant pieces working together. But it is a well-balanced, finely-tuned, closely-monitored process that can easily go haywire if, as my sister said, just one screw is out of place.
Engineering at any level is interesting. From millions of transistors crowded inside an integrated circuit, to the turbine and generator deck of a coal-fired power plant, amazing things happen. The cool thing about Big Engineering is it is easier to see the system parts and pieces working together. Not so easy to look inside of an integrated circuit, let alone to figure out even the basics of what it does (unless, of course, you either designed the chip or have a datasheet). But how industrial-sized systems work is easier to decipher, with the added advantage of being able to reach out and touch the toys.