Category Archives: energy

Ethanol Plant Tour

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Aerial view of the Front Range Energy Ethanol plant

Last week I toured the Front Range Energy ethanol plant in Windsor along with 9 other members of the Northern Colorado Clean Energy Network many of whom are also members of the Northern Colorado Renewable Energy Society. I had requested the tour because I had a desire to see this facility up close to find out what is involved in an operation capable of producing 40 million gallons of ethanol per year. The company manager, Dan R. Sanders, and FRE employees very graciously set up a tour for our group and explained the details of ethanol production at the facility.

Ethanol has been an additive in auto fuels in the U.S. for many years. In addition to making the gasoline burn cleaner, ethanol increases the fuel’s octane rating and helps reduce our dependence on imported gasoline by more than 5 billion gallons per year. While this is still a small percentage of the U.S. consumption rate of 140 billion gallons of gasoline each year, its recent growth rate is impressive as is the rate of ethanol plant expansion and construction. I’ve written about E85 ethanol previously, including using it in vehicles that were not designed for it as well as in aircraft.

I am aware that ethanol is still controversial in some circles primarily due to some persistent myths such as it taking more energy to produce a gallon of ethanol than it returns, which is not true. Ethanol production in this country provides 40% more energy than it requires to produce it and that number continues to improve, but more importantly, ethanol’s energy has 3 times the value to consumers than the type of energy it uses, which is usually natural gas. When it comes to energy, some types of energy are worth much more than others because of convenience or compatibility with existing infrastructure. It’s the reason you probably don’t heat your house with coal, even though it’s the cheapest fuel per BTU by a significant margin.

The Front Range Energy plant was built in 2005 and began producing ethanol in 2006. Our tour included a 35 minute presentation to describe the operation in detail by Amanda Huber, the process manager, who walked us through each step in the highly automated process of converting corn into ethanol. She also answered many questions from our members. We were then taken through the facility by the company manager to see and hear all the equipment up close. The words that come to mind to describe the plant’s equipment are large, loud, and highly automated. There are many large cylindrical tanks connected with numerous pipes and pumps. The smell of the plant reminded me of the smell of our kitchen when we make pizza dough.

The corn arrives to the plant by both truck and rail and is stored in two impressively large 500,000 bushel storage silos. The corn from local growers arrives by truck and the corn from outside the region, primarily Nebraska, arrives by train. From the storage silos, the corn moves by conveyor to the hammer mills where flailing hammers pound the dried kernels through screens containing holes that will only allow particles smaller than about 1/10 of an inch to pass. This helps to expose the starch inside the kernel, which accounts for about 65% of the corn by weight. From the hammer mills, the corn passes to the slurry blender which mixes it with water and enzymes and cooks for several hours. It is inside this slurry cooker that enzymes begin to break the corn starches down into fermentable sugars.

From the slurry cooker, the mixture passes through some liquefaction stages and then on to one of four 535,000-gallon fermentation tanks. Additional enzymes and yeast are added to the mash, as it’s called at this stage, and it is allowed to ferment for about 50 hours. This stage is critical to monitor because it’s where the sugars are converted to alcohol and if this process is not properly controlled, it could ruin the entire batch. They use a combination of analytical instrumentation to monitor the health of the yeast as well as the concentrations of sugar, alcohol, and acids in this tank. After the fermentation step is complete, the mixture will contain somewhere between 15-18% alcohol. Another output of the fermenters is carbon dioxide which could be vented to the atmosphere, but in this plant it is fed directly to another plant that condenses it and provides it to bottling plants for carbonating drinks and for making other CO2 products such as dry ice.

The mix is moved from the fermenters to a 735,000 gallon beer well which feeds the distillers. Using a combination of heat and vacuum, the alcohol is separated from the rest of the mix using a beer column to produce alcohol in a 70% concentration and then it is transferred to a rectifier column to get the concentration to 95%. Alcohol and water form an azeotrope at this concentration, meaning that distillation can no longer further separate the water and alcohol. So the next stage is to run the mixture through a molecular sieve to remove the remaining water and produce anhydrous ethanol. The ethanol is then denatured to make it unfit for human consumption by mixing it with about 5% gasoline. It is then pumped into one of two 500,000 gallon tanks where it awaits transportation by truck or rail car to its destination.

From the bottoms of the distillation towers, the solids and water are pumped to a centrifuge which separates the water from the solids. The solids then become wet distiller’s grain which is used as an animal feed. In some plants, this grain needs to be dried so that it will not spoil during transportation and storage, but in northern Colorado, because of its proximity to numerous cattle feedlots and dairies, it can be shipped in its moist state directly to the dairies and feedlots. Trucks remove approximately 1100 tons of this material a day from the plant. If the distiller’s grain had to be dried, it would more than double the amount of natural gas consumed by the plant, so there is definitely a benefit to having large meat packing and dairy industries nearby.

I have simplified my description of this process considerably. There are many auxiliary steps to achieve a high level of efficiency for the plant. For example, there are steps for adding nitrogen to the fermenters, recycling the water, regenerating the molecular sieve, extracting and remixing syrup with the grain, and recovering alcohol which I did not mention. This plant has a lot of very sophisticated and finely-controlled processes. If you’d like to see a little more detail, there is an explanation complete with a diagram at the ICM website, the company that designed and built the FRE plant.

As an engineer, one area I found particularly fascinating was the control room which had a series of computer screens that showed a pictorial view of the real-time status of every level, temperature, flow, and pressure of the entire process from beginning to end, all being monitored by one person. The plant is so automated that it can be run by as few as 3 people. The plant only requires 32 full time employees to run a 24-hour a day, 365-day per year schedule. The plant is able to process 55,000 bushels of corn into 145,000 gallons of ethanol every day of the week and have minimal plant downtime, typically less than 7 days over the course of a year. The plant achieves a yield of 2.7 gallons of ethanol per bushel of corn.

I was curious to know how close to the nameplate value this plant was producing. I had interpreted the nameplate value to be the maximum output if everything ran perfectly every hour of the year. I was very impressed that the plant regularly exceeds the 40M gallon per year nameplate value by more than 20%. So, unlike power generating plants, an ethanol plant has a conservative nameplate value to take into consideration issues that may cause periodic downtime.

Another thing that impressed me was how aware the company manager was of power consumption in the plant. At this plant, a gallon of ethanol requires 15,000 BTU in natural gas and .5 kWh of electric energy. Since ethanol contains 76,300 BTU per gallon of thermal energy, and .5kWh is equal about 1600 BTUs, the excess energy is about 60,000 BTU per gallon.

There is a controversial study by Pimentel and Patzek that is referenced frequently by skeptics about how ethanol has a negative energy balance of 20% meaning that it takes 20% more energy to produce ethanol that it delivers as fuel. However, two separate USDA studies contradict that study, the most recent one showing a 40% net positive energy balance. Yet the numbers the USDA uses, often called ‘optimistic’ by critics, are not as high as the actual numbers from this operating plant. For example, the USDA cites portion of energy attributed to the ethanol plant as 49,700 BTU/gallon. Yet here is an actual plant using only 16,600 BTU in combined natural gas and electricity per gallon. Even if they had to dry the distiller’s grain, they’d still be under 34,000 BTU/gallon. So I don’t think that the USDA study is overly optimistic. It seems to me to be very conservative.

And, like I mentioned before, energy balance is only part of the equation. The cost per BTU of various forms of energy vary significantly so if you take one type of energy that is worth $7/MBTU, such as natural gas, and covert it into energy that is worth $23/MBTU, such as automotive fuel, then energy balance is overshadowed by the net increase in economic value of the energy.

I got a lot of positive feedback from the rest of the members about the plant tour. It was a great to have a chance to see firsthand how ethanol is made. We really appreciated the professionalism and hospitality shown to us by the knowledgeable staff at the Front Range Energy plant.

Electricity from Human Power

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Every once in a while I read stories about people generating electricity with treadmills and bicycles by connecting them to electric generators. I read an article recently about a health club in Hong Kong that was using the energy from the human-powered exercise equipment to offset its electric bill. Whenever I read something like this, the first thing I want to do is put it in its proper context. I want to know if it’s being done for symbolic reasons to make people feel good in a ‘green sense’, or if it really has any potential to make a significant contribution to our energy needs. Before I get to that, I’d first like to talk about some terminology related to power and energy.

In the U.S., you will often see the term horsepower (HP) used to describe the size of an internal combustion engine or electric motor. Horsepower is an incredibly sticky term. By that I mean that the term ‘horsepower’ helps to put a vague concept into something easier to comprehend. It was first coined by James Watt in the 1800’s in order to quantify the rate of work that could be done by steam engines. He needed a way to put the power of a machine in some context that would be easy to understand. Watt recognized that an average horse could pull a load of 180 lbs at a speed of 2 mph. Back in those days, horses were not only used for transportation but were often harnessed to large diameter rotating wheels to perform functions like lifting loads of coal or water out of a mine. In some cases the apparatus could be adapted for grinding grain at a mill. If you do the multiplication, pulling a 180 lb load at a speed of 2 mph is equivalent to 550 ft-lb/sec which is the value used to compute horsepower today.

In most other parts of the world, the metric SI unit kilowatt (kW) is now used to describe mechanical power. I find it a little ironic because James Watt coined the term horsepower to put mechanical power in a recognizable context. Now, in order to honor him, we completely removed the context from the term by naming a unit of mechanical power after James Watt instead! In reality, the term ‘watt’ can be use to describe both mechanical and electrical power. Thus it makes it quite convenient to use watts so that it’s not necessary to use any computation to convert from mechanical to electrical power. With HP we need to do a little arithmetic to go back and forth. One HP is the equivalent of 746 Watts or .746 kW. Or, if you prefer, 1 kW is equal to 1.34 HP.

Back when I was in college, my roommate and his mechanical engineering classmates were trying to figure out a way to split a log using a .1 HP motor. I asked why he planned to use such a small motor and he said that it was a test of their skills as designers. A man can work at a rate of .1 HP and can split wood with an axe and so it stands to reason that a few smart MEs should be able to design a machine that was as efficient as a man. They wanted to store the energy in a flywheel, but couldn’t figure out a way to get it out of the flywheel to split the wood. I recalled my uncle telling me about a device he used that was like a conical screw to split logs that was attached to a wheel on a car. With the front wheels of the car chocked and one of the rear tires removed, the conical screw was attached to the hub with the wheel lugs. With the axle supported, the conical screw would spin and even at idle have no trouble screwing itself into a sizable log and splitting it. They looked around for the device and eventually found one and were able to adapt it to their large flywheel. A version of this log splitter is still sold today . With the conical screw in combination with their flywheel and tiny .1 HP motor they were able to split logs with great success. Upon looking at the arrangement, no one thought it was going to work, but it did and they were quite happy with the result.

Ever since that project, I have always recalled the number 1/10 of a HP or 75 watts in the context as what a healthy human could be expected to generate on a sustained basis. For periods shorter than an hour, a healthy human could generate about twice that amount or about 150W, and an elite athlete can generate nearly 300W (.4 HP) for as much as 8 hours. For very short bursts, a human can even exceed 1 HP.

This brings me back to the original question. If you had to generate your own electricity, assuming it was a full time job of 8 hours a day, how much of your own electricity could you generate? The answer is that if you worked 5 days a week, 8 hours a day at a rate of 75W, you’d be able to generate about 12 kWh of electricity per month. This is about 1.7% of what a typical U.S. household consumes. The value of this much electricity is around $1.20. That’s $.0075/hour. Yes, it means you would not quite generate a penny’s worth of electricity per hour of pedaling effort. But I’ll bet you’d be in great physical shape in no time.

I would be remiss if I didn’t include the food energy required to offset this new level of physical activity. The human body is about 20% efficient at converting food energy into mechanical energy so the 600 Wh you produce per day would need an additional 3000 Wh of food. This amounts to 10800 kJ or 2580 food calories. A typical basal metabolic rate for an average man is around 1900 calories per day, so if you were to add this level of activity to a sedentary lifestyle, you’d see some dramatic weight loss, assuming you didn’t more than double your food intake to compensate for the new hunger pangs you’d begin to feel.

So now when I read about human-powered generators, I recognize that you could use something like it in an emergency to power a light, or even a laptop computer, but it would not contribute in a positive sense to a sustainable energy program because you’d likely have to double your food intake which would cost much more than the 6 cents a day of electrical energy you could produce.

Colorado Hydroelectric Power part 3

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To wrap things up, I wanted to provide a short chronicle what is most likely the earliest instance of hydroelectric power in Northern Colorado.

Nearly 100 years ago the Fall River hydroelectric plant was built by F.O. Stanley just northwest of Estes Park, CO. Stanley is best known for developing the Stanley Steamer automobile. Stanley came to Estes Park in 1903 at age 54 when he was suffering from tuberculosis. His doctors thought that the dry mountain air would be beneficial for him. It must have worked because F.O. Stanley went on to recover from TB and fell in love with Estes Park and decided to move there permanently. He ended up living into his 90’s and left his mark on the town. Today you can see the luxurious Stanley Hotel perched up above the north side of the town. It’s become quite a tourist attraction in its own right. One of the hotel’s most notable distinctions is that it was the inspiration for Steven King’s famous book The Shining.

Stanley recognized that the hotel would need electrical power so he took it upon himself to construct a hydroelectric plant utilizing the Fall River which exits Rocky Mountain National Park at the Fall River entrance. This river meets with the Big Thompson in Estes Park and then goes on to Estes Lake which is formed by the Olympus Dam. The Fall River plant is about 3 miles northwest of town very close to the Rocky Mountain National Park Fall River Visitor’s Center.

The Fall River hydroelectric plant was built in 1909, the same year as the hotel, and had a Hug Water Wheel powering a 200 kW GE generator. It was initially intended just to power the hotel in the summer months but residents of the town also wanted to have electricity so Stanley agreed to sell it to them. Within a short time, the generator was no longer large enough to supply a growing population. Stanley decided to use a coal-powered steam plant at the hotel to free up some of the Fall River plant’s capacity for the town’s residents. He also replaced the penstock that was fed by Cascade Lake with a larger diameter pipe. Cascade Lake is located about a mile upstream and is 400’ higher in elevation than the plant.

In 1921, a second unit was added, a 900 HP Worthington Francis turbine powering a 680 kW GE generator which only ran from May through September when the river flow was sufficient to supply the power.

The plant was augmented with diesel generators several times and ownership was passed from Stanley to the Public Service Company and eventually to the Town of Estes Park who owns the plant today. The Lawn Lake Flood of 1982 damaged the plant and penstock and today it no longer produces any electricity but is instead run as a museum. You can read much more about its history and how to find it here.

My wife loves to gift shop up in Estes Park and I usually accompany her and follow her around from store to store as she searches for just the perfect gifts. I don’t think you’ll find a higher density of gift shops anywhere in the world than you will in Estes Park. I enjoy the scenery while traveling there and back, but next time I think I’ll take my own little side excursion during the shopping activities and tour this hydroelectric facility.

Colorado Hydroelectric Power part 2

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After my last posting on Colorado Hydroelectric power, I got a comment related to the fact that there were several hydro plants on the Big Thompson River. I started to do some more research eventually culminating with a visit to canyon yesterday to do some firsthand investigation on the subject.

There are actually two hydro plants situated on the Big Thompson River. One is part of the Colorado Big Thompson (C-BT) project and is located down by the mouth of the canyon near the Dam Store. It’s called the Big Thompson Power Plant and was accounted for in my last posting. It is the smallest of all the C-BT generating plants (4.8 MW) and is only operated during the runoff season from May through September. There is a dam just upriver from it, but the water from that dam is not used to power it. Instead, it is powered by a penstock with 180’of head that comes from the Charles Hansen Feeder canal. The canal runs across Highway 34 via an inverted siphon. That’s the pipe you see when you enter the canyon.

This is the 4.8 MW Big Thompson hydro plant. The large overhead structure is a crane for servicing the generator.

The water in the Charles Hansen Feeder canal can be augmented with the Big Thompson River by a diversion dam located about a mile up the canyon. This small dam feeds water into the Dille tunnel which goes through a mile of solid rock to meet up with the Charles Hansen Feeder canal just south of the inverted siphon. You’ll notice that the pipe is quite a bit lower than the open canal sections that run on either side of it. I’ve included a Google Earth 3D perspective of this phenomenon. I never understood what that pipe did until I flew over it and then it was like a lightbulb going off in my head. I suppose an aqueduct that ran across the canyon at the canal elevation would have cost much more to construct than this inverted siphon. The Charles Hansen canal is used to fill Horsetooth Reservoir with C-BT water.

The Big Thompson power plant’s penstock is formed by a rectangular concrete chute that runs down from the canal on the south side of the highway 34 and is piped under the highway and over to the generating station. In addition, some of the canal water can be simply dumped into the Big Thompson River depending on how they want to move flow along the C-BT project.

This is the inverted siphon that crosses Highway 34. The canal is about 100′ higher than this pipe.

This is a Google Earth 3D view of the mouth of the Big Thompson canyon. You can see that the Charles Hansen canal is much higher in elevation than the pipe that crosses the highway. The power plant water inlet comes from the top of the canal on the left side of the canyon.

I spoke yesterday with a very nice woman from the Bureau of Reclamation by the name of Kara Lamb who posts frequently to a forum sponsored by Mountainbuzz. This forum is monitored by white water kayakers with rapt attention to check flow rates on the Big Thompson River. That way they know when it’s time to ditch work and do some kayaking. Flow rates are changed periodically to send water to where it’s needed and so the volumetric flow can vary unpredictably and thus is important for kayakers to check the forum to see when the water levels are suitable for kayaking. Kara is very knowledgeable about the C-BT project and in the course of one of her postings, she mentioned another power plant on the river owned by the city of Loveland. The power plant she referred to is the Idlewilde Hydro Plant located in Viestenz-Smith Park. This power plant is fed via a penstock from the Idlewilde Reservoir which is located about 2 miles upriver from the plant. The plant is very easy to overlook because it’s not very big and there is not much equipment around it to suggest it’s a power plant. It could easily be mistaken for a maintenance building.

I found in searching around that there was a trail that ran up the canyon on the opposite side from the park called the Foothills Nature Trail that was said to have a few exposed sections of the penstock, which is otherwise buried for the 2 mile distance it runs to the Idlewilde reservoir. I hiked this trail yesterday and took a picture of the metal pipe. It is 3’ in diameter and was originally made of wood back when it was first constructed in 1920’s.

A small exposed section of the Idlewilde Dam-Power Plant penstock. It runs 2 miles, mostly underground from the reservoir to the power plant and can carry 74 cfs of water.

I couldn’t find any information regarding the amount of water flow through the penstock or generating capacity of the Idlewilde plant on the Internet so I went to the park and found some posters that explained a little more about its tumultous history and other interesting facts. The generators inside the building were rated at 900KW which is enough to supply electricity to about 900 homes. Back in the days when the only use for electricity was lighting, this hydro plant could supply a substantial portion of Loveland’s electricity needs.

At 900KW, the Idlewilde hydroelectric plant much smaller than any of the hydro plants that are part of the CB-T project. But since it is not a technically a part of the C-BT project, there is no information about it on the C-BT web pages. The entire facility was completely wiped out in the Big Thompson flood of 1976 and the remnants of the 3 original generators are on display in the park. In the 1980s, the plant was rebuilt and the generators were replaced
with 2 turbines with the same generating capacity. The generating station subsequently returns all the water it receives from the penstock to the river just downstream from the hydro plant.

I also found on the Bureau of Reclamation website that my estimate of 50% for the capacity factor may be too high for several of the C-BT power plants, particularly the Big Thompson Power Plant since it only operates from May-Sept each year. Thus, its capacity factor is only around 20% of its 4.8MW nameplate value. I think that when the river flow is low like it is now in January (~20 cfs), only a portion of the rated power could be generated by the Idlewilde plant. In other words, a 74 cfs diversion flow from the Idlewilde Dam could not be sustained in the winter months and thus it would have to run at reduced capacity. But I was able to hear the generators running, so it appears to be generating at least some electricity year-round.

In talking with Kara, she mentioned that there have been various proposals to add hydro capacity over the years, such as at the outlet of the Olympus Dam in Estes Park, as well as the outlets of Carter Lake and Horsetooth Reservoir. However, these never seem to move forward due to their economics. They just wouldn’t generate enough power to cover their construction and operating expenses.

The more I research the C-BT project, the more impressed I am with the engineering and foresight that went into it. In addition to augmenting the water supply on the Front Range with more capacity that the Big Thompson and Poudre Rivers combined, the designers did an excellent job at extracting all of the available hydro power from the water with minimal environmental impact. It’s hard to fathom that much of the project was implemented more than 60 years ago.

My conclusion is still the same as my original assessment, that is, since now I know that 2 miles of the interior of the Big Thompson canyon essentially has its hydro power harvested to produce less than 1MW of power, the total capacity of the 20 mile stretch of canyon would account for no more than 12 MW of generating capacity which is certainly not enough to justify the environmental impact or economics of pursuing it.