Monthly Archives: December 2007

Colorado Hydroelectric Power

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My friend Bevan asked me recently why we don’t see more hydroelectricity projects being developed. I replied, “All available hydroelectricity that can be developed has already been developed”, hoping it didn’t sound too much like the unfortunate 19th century quote attributed to Charles Duell about how everything that can be invented has already been invented. Despite my interest in renewable energy, I had not thought very much about hydroelectric power since I have long assumed that if someone could have built another dam on any existing waterway and placed a generating turbine at the bottom of it, it would have been done decades ago.

Bevan responded, “Well, how about the Big Thompson River which flows unimpeded down a canyon for many miles and has no hydro generating stations along it?” I began to wonder if we had been avoiding employing a source of clean and renewable energy simply because of its environmental impacts, as often seems to be the case. I thought, “If the Big Thompson canyon could be dammed, how much hydroelectric power could it produce?” Please note I’m not suggesting that anyone actually do this. It’s one of the most naturally beautiful and accessible canyons in Colorado and even if it could supply enough energy to solve the entire world’s energy needs, it probably still would never be approved due to opposition by those who would like to keep the canyon and river in their natural states. I am just trying to satisfy a curiosity I have.

Often times, putting up dams on rivers is resisted even more vehemently by environmentalists than constructing fossil fuel-burning plants. The concerns range from the people who are displaced by lakes that are created by the dams to fish species that can no longer reach the river’s head waters to breed. Dams have some other benefits such as flood and drought control, but those may be overshadowed by the safety concerns of a dam breaking and causing flooding and destruction. So despite its environmentally-friendly electric power generation, hydroelectric power has other environmental impacts that can limit its acceptance.

A few months ago I took a clean energy class through CSU. One of the classes met at the offices of the Platte River Power Authority, a co-op power company that supplies electricity to the cities of Fort Collins, Loveland, Longmont and Estes Park. The PRPA gets about 20% of its power from hydroelectricity. While touring the grid control facility, I saw a lot of generating stations on the large control board. Among them were several hydro generating stations located west of Fort Collins. I realized that I had somehow overlooked these generating stations in my travels, although I’m sure I had driven by them or flown over them on many occasions. Upon doing some research into the topic, I found that the hydroelectric generating stations monitored by the PRPA are powered with water that is diverted from the western slope. Through a series of tunnels, canals, and siphons, nearly all of the 260,000 acre feet of water diverted annually from the western slope has its energy converted to electricity by a series of power hydroelectric generating facilities, most of which are easy to overlook.

The means to divert the water from the western slope is called the Colorado Big Thompson (C-BT) Project. It is one of the largest and most complex natural resource developments ever undertaken by the Bureau of Reclamation. There are more than 100 structures comprising this project which you can read about here.

The most important part of the project is the Alva B. Adams tunnel that directs water from Grand Lake on the western slope to the eastern slope of the Rocky Mountains. The tunnel is 13 miles long and goes through solid rock under the continental divide. The water eventually finds its way into several large man-made reservoirs, the largest two being Carter Lake and Horsetooth Reservoir which are situated in the foothills along the Front Range. Prior to arriving at these reservoirs, the water flows through 5 hydroelectric generating stations. I’ve listed them and their capacities in this table:

Generating Station Penstock Head (ft) Capacity (MW)
Mary’s Lake 205 8.1
Estes Park 482 45
Pole Hill 815 33.25
Flatiron 1055 71.5
Big Thompson 180 4.5

Unlike many of the hydro generating stations you find on large rivers, the ones that are part of the Colorado Big Thompson Project are small stations located at the end of long pipes called penstocks, which are large diameter tubes connected to the upstream water source.

Energy contained in water is proportional to both the water’s pressure and flow rate. This energy is converted to electric power through a turbine-generator. Available water flow is usually dictated by nature by the region’s snowfall and rainfall. Pressure, however, can be adjusted. To increase the pressure, it’s necessary to increase the depth of water, also known as its ‘head’. Water pressure increases about 1 psi per 2.3 foot of head, and as a result, you can see that the generating stations with the higher penstocks in the table above produce much more power. One way to get more pressure is to construct a very tall dam. Another way is to construct a relatively shallow dam and put the generating facility at lower elevation and connect the dam and generating station with a penstock. You need to constrain the water in the penstock that runs downhill to the generating station which has the effect of greatly increasing its pressure. Sometimes these large diameter pipes are buried, and other times they are exposed. You can see them exposed in several places in Colorado Big Thompson Project, such as above and below Mary’s Lake just south of Estes Park. There you can see a long sections pipes running down a mountainside. At the bottom of the upper penstock, you’ll find Mary’s Lake generating station. A similar penstock runs partially underground and partially above ground from Mary’s Lake to the east side of Estes Lake, where you will find Estes Park generating station.

I am missing one C-BT power plant in my list above because it is located on the western slope, a 21.6 MW generating facility on the Green M
ountain Reservoir. Although it is technically part of the C-BT project, I didn’t include it because I was interested in figuring out how much power is generated from this diversion project from water flow to the east side of the continental divide. I was also curious about how much water flowed to the east side of the continental divide through the tunnel and how it compared with the normal Big Thompson River flow. In other words, just how much water do we import from the western slope?

Wikipedia lists the average flow rate of the Big Thompson River to be 72.5 cu. ft/sec where it exits the Big Thompson Canyon. The Alva B. Adams tunnel can handle a flow rate of 550 cu. ft/sec. It runs at about 84% capacity on an annual basis which means that it has an annual average flow of 460 cu ft./sec. I was very surprised by this number. This means the tunnel provides more than 6 times as much water flow as the Big Thompson River provides on an annual basis.

The total maximum generating capacity of the 5 hydro plants that I’ve listed in the table is 162.5 MW. A reasonable capacity factor for hydroelectric generating plants is 50% so we can assume that the average annual generating capacity of these stations is about 81 MW or 710 million kWh per year.

So, where am I going with all this? I’m trying to figure out how much energy could be obtained if we were to convert all the flow of the Big Thompson canyon using several large dams or a series of smaller dams with penstocks connected to generating stations. Based on the differences in flow rates between the Big Thompson River and the diverted flow through the Alva B. Adams tunnel, which is a factor of 6.4 greater, I would estimate that the amount of power available from the Big Thompson River would be around 12 MW, again assuming a capacity factor of 50%. I figure that the head of each flow is the same, and thus the flow rate difference means that the Big Thompson would generate about 16% (1/6.4) of the capacity of the C-BT generating stations if it were to all be converted to electricity. That’s enough to power 12,000 homes. This sounds like a lot, but to really put it in perspective, this is only around 2% of the capacity of a typical fossil fuel generating plant. For example, the Rawhide Power Plant north of Fort Collins which is a coal/gas plant can generate 522 MW. The Fort St. Vrain power plant south of Greeley which uses natural gas can generate 720 MW. Nuclear plants typically have capacities of 1000 MW or more, with the largest one capable of generating more than 8000 MW. When you talk about power in those quantities, 12 MW seems like a drop in the bucket.

It would appear that the amount of power available from the Big Thompson River is so small as to not make it worth the investment even if there were no environmental concerns. The construction costs would be quite substantial, considering the impact to the region such a project would cause. It would require moving many homes and businesses as well as the highway that runs through the canyon.

Rivers in the Colorado are much smaller than the ones you find in the eastern and pacific northwestern parts of the United States. In fact, based on flow rate, they would probably only qualify as creeks in other parts of the country. On the lower section of the Susquehanna River in Pennsylvania, there are 3 hydroelectric dams in a span of 21 miles that combine to generate more than 1,000 MW of hydroelectric power. But with an average flow rate of 40,000 cu ft/sec, the Susquehanna River has 500 times the flow of the Big Thompson River.

The largest hydroelectric generating project in the world is currently under construction in China. The Three Gorges Project will have an output of 22,000 MW and will thus qualify as the largest electrical generating plant in the world of any kind. It’s not without its environmental impacts, however. Nearly 1.4 million people had to be moved in order to fill the lake behind the dam. I suppose eminent domain may work a little differently in China than it does in the U.S.. I can’t conceive of any public works program that could displace people on that scale in the U.S. or any other country for that matter.

Hydroelectric power is one of the oldest and largest sources of renewable energy available today. Its output doesn’t vary as much as other renewable energy sources like wind or solar. It even offers the potential for energy storage to allow for peak demand-shifting. However, I don’t think that it can be expanded significantly from its current state, except perhaps in a few geographies around the world that are underdeveloped by western standards.

Giving the Gift of Light

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I’ve been in an engineer for more than 25 years and have designed a lot of products during that time. So every time I get a new product, I look at it from a design engineer’s standpoint. Sometimes I am pleased to the point that I wish I could meet the engineers who designed the product just to get their story on all that went into designing it. Other times I think engineer must have been inexperienced, or possibly under pressure to meet a cost goal or time deadline.

When I ordered a Bogolight a few months ago, I didn’t know exactly what to expect. I was intrigued, yet a little skeptical, because I never had seen a similar business model for selling products. The letters BOGO stand for ‘Buy one, Give one’. The flashlight is sold in such a way that when you pay $25 for one light, you’re actually buying two of them, one for you and another for a charity. In this case, the Bogolights going to charity are heading for developing regions in Africa.

The Bogolight is the brainchild of Mark Bent, CEO and President of SunNight Solar who conceived of designing a solar rechargeable flashlight and selling it in a way that would get flashlights to go to a place where they are desperately needed yet without the resources to purchase them. Mark spent over twenty years in the developing world and understands their needs better than most. He realized that in most of the developing world, there is no reliable electricity and so any reading at night must be done by a kerosene lantern, which is expensive and very inefficient. Imagine if all of your night time reading or studying had to be illuminated with the dim light of a kerosene lantern. You’d have probably done a lot less of it. I know I would have.

The Bogolight provides reading light with high efficiency white LEDs powered by solar rechargeable batteries. The solar cells are built right into the flashlight. For every hour that it’s charged, it provides about 30 minutes of brilliant white light. With an 8 hour charge, it can provide sufficient illumination to last for an entire evening’s worth of reading. Best of all, you don’t need to continually replace batteries. It uses 3 readily available rechargeable AA batteries that are capable of more than 750 charge-discharge cycles. I’ve often found that rechargeable products have either built-in batteries or else they use custom-designed batteries that are dreadfully expensive to replace. So my hat is off to the Bogolight designers who chose to use standard rechargeable AA batteries.

The 6 LEDs have a life expectancy of about 100,000 hours of continuous use and the integrated solar panel is designed to last 20 years. When the average life expectancy of consumer electronics products seems to shrink every year, it’s refreshing to see something like this that is obviously ‘built to last’.

I really appreciate the rugged design, complete with moisture seals. Another pleasant surprise was the glow-in-the dark accent to makes it easy to locate in the dark. Its bright orange color makes it easy to find during the day too. It also has a built-in hook to hang it from overhead to make task lighting easier. The hook has a spring-loaded clip so you can attach it to a backpack and carry it around without fear of losing it. I am very impressed with the attention to detail that was obviously put into its design.

Now that I’ve had the chance to use it for several months, I can say with confidence that Mark Bent and the people at SunNight Solar are doing something truly wonderful and if you’re looking for a unique Christmas gift, you can rest assured that the recipient will find nothing else like it. Better yet, when you buy one, you’ll also have the satisfaction of knowing that someone in Africa will be getting a highly-valued and useful Christmas gift, and it’s hard to put a price on that.

PC Resuscitation

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I get a lot more satisfaction out of fixing things than I do replacing them. Part of it is the challenge, part of it is the learning experience, and part of it is the savings. But I think the biggest part of it may be genetically programmed into my DNA.

I do realize that sometimes it’s cheaper to replace something than it is the repair it. The other day I was looking over a broken electric can opener that we had replaced for the princely sum of $15 and realized that it was not worth repairing. I didn’t know what I’d do with an extra used electric can opener if I did repair it when they are available new for as little as $6 at Target.

I got an inquiry last week from my cousin in Pennsylvania about whether a power supply for a Compaq PC manufactured in 2002 should cost $185. I am usually able to pick up PC power supplies for as little $15 to $25, and so this price seemed way out of line. Upon further investigation I found that back in 2002 Compaq was using a non-standard connector and case size in their desktop power supplies. This makes the power supply rare and therefore very expensive. After looking over the pinout of the motherboard connector for the Presario 5000 model, it appeared that the majority of the pins were consistent with the ATX standard, but there were enough changes that it would take some fiddling to adapt a standard power supply to work like the Compaq model. The failure mode didn’t seem consistent with a normal power supply failure though. Usually when a PC’s power supply fails, the computer will show no signs of life. In this case, the computer would power on, but in a short time would shut itself down. This made me suspect that perhaps there was a bad electrolytic cap on the motherboard that would short and cause an over-current condition after things warmed up. If that were true, even a new power supply wouldn’t fix the problem.

My uncle is quite handy designing and fixing all things electrical and mechanical and offered to help. Despite having very little experience with computers, in a relatively short time, he and another relative were able to determine that the power supply’s fan had stopped spinning. That would explain why it was powering on but shutting down after a while. He went to Radio Shack and found a similar fan but it would not fit inside the power supply’s case. No problem, he mounted it outside the computer’s case over the power supply vent. It still fulfills the need of moving air through the power supply to prevent it from overheating. The fix worked and the PC has been successfully resuscitated.

It may be his nearly 70 years of ham radio and tinkering experience that came to the rescue because once you understand how things work, you can fix them even if you’ve never done a repair exactly like it before.

And then, of course, there’s that DNA thing too.

Ponnequin Wind Farm Tour

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The Northern Colorado Clean Energy Network conducted a field trip on Friday, November 30th 2007 to visit the Ponnequin Wind Farm. This wind farm is located just south of the Colorado-Wyoming border and about 2 miles east of Interstate 25. We had a total of 21 attendees. We met at the Fort Collins Park-n-Ride and carpooled to the site where we met with Ken Bolin, Senior Engineer at Xcel Energy who hosted us on the tour.

The weather was chilly in Fort Collins, about 17 F with light winds, but we all knew that it would be colder and windier at the site. Sure enough, as we got closer to Wyoming the outside air temperature had dropped to 11 F with a wind blowing around 15-20 mph. As we got into Wyoming, the cloud ceilings began to descend, making me wonder if we’d even be able to see the wind turbines.

As we arrived at the entrance gate, Ken was unlocking it and some light snow was beginning to fall, sideways of course, which is the direction that snow always seems to fall in Wyoming. In the few minutes that I left my vehicle to talk to Ken the cold wind chilled me to the bone.I’ve been to Wyoming in the winter on quite a few occasions and yet I still cannot get used to how much colder its weather can be than Colorado’s. The wind chill factor was breathtaking, to say the least.

We followed Ken as we drove for about 3 miles along dirt roads. We were only able to see the turbines when we got within a quarter mile from them and even then could only see the bottoms of the spinning blades because the clouds were so low that the tops of the towers and blades disappeared into them. We parked our vehicles and assembled in the maintenance building where Ken told about the site’s history and many other interesting facts about the wind turbines.

After the ceilings lifted, we were able to see all the turbines.

The Ponnequin Wind Farm is Colorado’s first wind farm and was built in several phases starting in 1998. The first phase consisted of seven 750 kW NEG-Micon turbines with a total capacity of 5 MW. A year later, 22 more 750 kW NEG-Micon turbines were installed bringing up the total generating capacity to 21 MW. In 2001, 15 more 660 kW Vestas turbines were installed which brought the capacity of the wind farm to about 31 MW with a total of 44 turbines. I should mention that wind farms are rated at their maximum generating capacity, but they don’t generate at their maximum capacity all the time. A wind farm that is positioned on a good site will generate about 30-35% of its maximum capacity averaged over the course of a year. This percentage, known as the capacity factor, can go higher if the winds tend to be more consistent, such as they are for off-shore wind farms. We also found that in North America, the capacity factor varies considerably throughout the year. For example, the months of April through September may only have an average capacity factor of 10%, whereas during the months from October through March it can be as high as 70%.

People are always trying put generating capacity in perspective and so you’ll often hear that a wind turbine can power a certain number of homes. A general rule of thumb is that each household consumes about 1 kW of energy on a continual basis so 1 MW of generating capacity is enough to power 1000 average homes. Electrical power is sold by the kWh and since there is an average of 730 hours per month, the above rule of thumb would imply that an average household consumes about 730 kWh per month. This average household energy consumption has been creeping up steadily so you may find that it varies depending on the date of the reference. I should also mention that the cost per kWh varies considerably over the U.S. from a low of $.051/kWh in West Virginia to a high of $.208/kWh in Hawaii with the average hovering around $.10/kWh. In Europe, the cost is closer to twice the average U.S. rate.

Estimating an annualized capacity factor of around 30%, this 31 MW facility should generate about 9.3 MW x 8760 hours/year x $.10 kWh x 1000 KW/MW = $8,150,000/year worth of electricity. This would be enough to power 9300 homes. The cost of generating the electricity at this site is $.057/kWh so it would appear to be profitable for Xcel, although there are other power distribution costs that I’m not including. But if you take into consideration that power companies are able to charge a premium for wind energy, then it should all tend to even out. In the case of Xcel Energy, they do this through their Windsource program which effectively adds about another $.01/kWh to the retail price. I participate in this program and so about one third of the electricity I use in my home effectively comes from wind power.

Ken explained that the major factors that influence the selection of wind farm’s location are the speed and consistency of winds throughout the year, its ease-of-access, and its proximity to power distribution lines. High voltage power distribution lines can significantly add to the expense of the wind project if they have to be extended very far since it costs about $500,000 per mile to build them. Today wind farms cost about $1800 per kW to construct which is nearly twice what it cost 10 years ago. This is largely due to increases in the cost of raw materials such as concrete, copper, and steel in addition to the increased demand for turbines.

One of the common concerns expressed about wind farms is their effect on local wildlife, but in the case of the Ponnequin site, there doesn’t seem to be much, if any, interference with the wildlife in the area. The wildlife that inhabits the site includes deer, elk, antelope, fox, coyote, ground squirrels, badgers, and, of course, birds. The antelope appreciate the shade of the towers provide in the hot sun during the summer and will line up and lay down in its shadow and then continue to move as the sun changes the position of the shade. Cattle are also allowed to graze on the property and on occasion have been known to stand in a line at the fence and stare curiously at the turbines.

Bird strikes have been very minimal with only about 20 birds killed per year at the site. Only one raptor has been killed in the 9 years the site has been operating. To put it in perspective, for every bird killed by a wind turbine, 250,000 are killed by domestic cats, cars, and controlled flight into windows.

With generating capacities of 660 to 750 kW each, the Ponnequin turbines are smaller than the ones that are being delivered today which are averaging between 1 to 2 MW each. Even so, they are still impressive in size and you can really appreciate it when you get up close to them. The blades are 70 feet in length and are mounted on a hub that is positioned 170 feet in the air. The NEG-Micon blades are fixed pitch, but have a 12 foot tip section that is hydraulically actuated when the wind speed exceeds 57 mph. When that happens, the tip sections pop out and rotate 90 degrees and this slows down the blade so that it can be stopped by a disc brake mounted inside the nacelle. This is done to protect the blades, gearbox, and generator from being destroyed in high winds. Once the wind slows down enough, the tips retract and the turbine will automatically begin spinning again. Ken told us that winds exceeding 90 mph have been recorded on the site and that during the windy season, it’s not unusual to experience 3 or 4 shutdowns due to high winds each month. In the case of the Vestas turbines, the blades are variable pitch so they are able to adjust their angle to get the maximum energy out of the wind at low speeds and at high speeds, they can be rotated to slow down the rotor enough until the disc brake can stop it completely.

The blades have built-in lightning protection in the form of conductive members buried inside the fiberglass/epoxy blades to attract and conduct the energy of a lightning strike to ground which protects the blades from damage. Ken mentioned that some wind turbines were installed in Wyoming that did not have lightning protection and during a weekend of thunderstorms a number of turbines experienced catastrophic blade damage. So lightning protection in the blades is very important.

End view of a blade. Note person’s hand in left hand upper corner to get a sense of the size.


NEG-Micon blade 70 feet long.

Many of our group’s questions were related to the costs to run the wind farm and reliability of the turbines. Ken said there are 3 full-time employees required to run site and mentioned that the annual maintenance budget varied considerably from year to year depending on what needed to be replaced. He related an incident when some improperly torqued bolts had caused a nacelle complete with gearbox, generator, and rotor to tilt over and fall 170 feet to the ground while it was spinning, completely destroying everything in the process. The resulting damage was nearly $750K. A blade sets cost around $250K and an equal amount is required for a new generator and gearbox. Then there is the cost of the crane which is $10,000 to move it in, $10,000 to move it out, and $1,000 per hour that it operates. It appears that the crane costs are a major factor in maintaining a wind farm. Some maintenance items can be handled without a crane, but when it’s necessary to use the crane to bring down a gearbox or generator, the downtime can be significant, taking as long as 3 to 4 months depending on part availability. In some cases, it’s been necessary to have parts custom-machined to get the gearboxes repaired due to long lead times on parts. Ken tries to keep rebuilt generators and gearboxes on hand to minimize downtime in the event that one needs to be replaced. However, there are times during the winter when it’s impossible to get a crane on site and so much of the maintenance is done during the warmer months.

After our discussion in the maintenance building, we all went outside again to get a look at the turbines. I was relieved to find that the cloud ceilings had lifted and we were able to see the tops of the turbines and had more than a mile of visibility. We drove to an operating turbine and 15 people squeezed into its base to hear about how one goes about climbing up the ladder when maintenance in the nacelle is required. We also got to see the controller in the base with digital readouts of various parameters used to monitor the health of the turbine as well as its output. At the time we were there, the turbine was operating with an output of 375 kW, enough to power about 375 homes.

Then we went to look at a set of blades that were on the ground resting on some hay bales. They were awaiting some parts and a crane to reattach them to the turbine. I asked about maintenance on the blades and Ken mentioned that whenever they are taken down from the tower they are carefully inspected and any damage is repaired. They use composite repair techniques similar to the way you’d repair a composite boat or airplane. On occasion, it’s possible to repair a blade from a crane while the blade is still mounted on the tower, but when it’s on the ground, it’s much easier to work on it. A damaged blade sometimes whistles as it spins, making it possible to know in advance if a turbine has blades that may need some repair work.

We then went back to the maintenance building to ask some final questions and to warm up a bit. We also looked over some of the turbine parts, including a generator, prop cowling, slew motors, and disk brakes. The size of these parts was very impressive.

A box with two electric slew motors. Five of these are used to rotate the turbine into the wind.
The blue item in the background is a 660 KW generator.

This is the blade cowling that covers the hub.

Ken then led us to the front gate where we departed back to warmer climate of Colorado. About 8 of us then gathered for lunch and had a good time discussing wind turbines and what we learned.

We really appreciated Ken’s generosity for hosting this tour and are grateful that Xcel Energy allows groups like ours to tour their facility to learn more about wind power.

Several people took some great digital photos and put them up on web sites where you can view them from these links:

Hugh’s pictures

Scott’s pictures