Hydropower at the Woolen Mill

Vertical drop in feet times flow in gallons per minute divided 

by 10,000 equals kilowatts, and kW x 1.34 equals horsepower.

Deep in the bowels of Clock Tower Place there is a space where an antiquated monster once sat – the turbine which converted water power to electrical power. This machine was the last of several generations of hydropower generating engineering in the mill.

Hydropower is all about high school algebra. Vertical drop in feet times flow in gallons per minute divided by 10,000 equals kilowatts, and kW x 1.34 equals horsepower. For the metric-minded, vertical drop in meters times flow in liters per second times 9.81 divided by 1,000 also equals kilowatts. By this math, ten gallons of water dropping 100 feet yields the same power as 100 gallons of water falling ten feet.

Actual power yield is always less than theoretical due to friction and other inefficiencies. An “undershot” waterwheel describes a design with water running under the wheel, pushing the bottom blades forward. For wooden wheels of this design capture of the water’s energy was on the order of 20 to 30 percent.

Wherever greater vertical drop allowed, water was led over the top of the wheel to pull blades downward by force of gravity. This style, referred to as “overshot,” traditionally captured 50 to 70 percent of available energy. By the 1830s wheels would have had wooden blades, rims and spokes attached to iron hubs and axles. Late in the 1800s the Fitz Waterwheel Company was selling all-steel waterwheels, with the advantages of nearly 90 percent efficiency plus resistance to icing in winter.      

Ben Smith dam stored water for the woolen mill

Back to Maynard, or what at the time was known as Assabet Village. Construction of the Ben Smith Dam, the mill pond and the canal between the two in 1847 resulted in a large, year-round water reserve at an altitude above sea level of 175 feet. Outflow from the waterworks would have reentered Assabet River below the mill at an altitude of 155 feet. Flow rate through the system is not known, nor design, but a good guess is two overshot wheels each with a 15 foot drop and a combined flow of up to 45,000 gallons per minute.

That flow is equivalent to 100 cubic feet of water per second (cfs). For comparison, the Assabet River has a year-round average of 200 cfs, but summer months average under 100 cfs. Keep in mind that water power production was never around the clock. Flow through the mill was stopped at the end of the workday to back up as much water as possible in the millpond for the next day.

Power production was approximately 50 horsepower. As Maynard’s mill operations grew, water power was supplemented by coal-fueled steam power, hence all the historic images with smokestacks. The book “Assabet Mills” states that by 1879 nearly 40 percent of power was from steam engines. A different source states that the first steam engine was installed in 1862, when Amory Maynard was increasing capacity to meet Union Army contracts for wool goods. 

At some point the waterwheel complex was replaced by a turbine. Turbines are much more compact than wheels. Water drops down through a progressively narrowing pipe. This water, now under high pressure, jets into the turbine chamber at high speed, spins the turbine blades, and exits out the bottom. Turbine efficiencies rival the best wheels.

Records show a hydroturbine used to generate electricity from 1902 to 1968, with a hint that Digital Equipment Corporation may have refurbished the power plant in 1983 and run it until 1992. The Clock Tower Place 2002 petition to surrender electricity generating rights described the last operative turbine as having a pass-through of 128 cfs and production of 125 kilowatts of energy.

CTP has recently had some second thoughts about alternative and renewable energy sources, and according to Joe Mullin, CTP’s Public Affairs Director, is tentatively exploring the process of restoring hydroelectric power generation. Currently, the turbine is long gone, the smokestack is merely a support for cell phone antennae, and all of the kilowatt-hours used to power CTP by day and light up the windows by night are wired in from elsewhere.

Coda: According to an article in the March 14, 1902 issue of The Maynard News, the switch to electric power included the installation of two vertical compound engines directly connected to electric generators. The engines would have been steam engines powered by either coal or fuel oil. The power of the two engines was 2,500 and 800 horsepower. From this time forward hydropower was clearly a minor portion of total energy production at the mill complex. Employment at the newly enlarged complex owned by the American Woolen Company was 2,000. 

Assabet River National Wildlife Refuge

Hunting is allowed in our neighboring wildlife refuge. Details first – the Massachusetts deer hunting season runs from mid-October to the end of December, is limited to bows, shotguns and muzzle-loading rifles, and never on Sundays. These are all short-range weapons compared to hunting rifles, hence lowering the risk of accidental shootings. The application deadline was back in July. The Assabet River National Wildlife Refuge also has hunting seasons for turkeys, grouse, woodcock, rabbits and squirrels. Deer hunters must wear orange. During hunting season, so should you.

Origins of the Refuge date back to the 1942 seizure of land spanning Maynard, Sudbury, Hudson and Stow by federal eminent domain. Landowners were given about ten days to pack up and leave, and by their own accounts received around ten cents on the dollar of what the land was actually worth.

Blueprint of munitions bunker [click to enlarge]

One of the most interesting features of the Refuge is the World War II era ammunition bunkers. The site was chosen to be convenient to railroad shipping to the Boston Navy Yard, which was active over the years1801-1974 and currently home to the USS Constitution, yet far enough inland so that a German battleship could not shell the area. Each of the 50 bunkers, officially referred to as “igloos,” has inside dimensions of 81x26x12 feet, with a curved roof. Sides and roofs were mounded with dirt for extra protection and disguise. Today, from all but the door end, these bunkers resemble small hills, complete with a forest of trees growing on top. Bunker #303 is sometimes open for tours. 

After WWII this site, referred to as the Fort Devens-Sudbury Training Annex, served as a troop training ground, ordinance testing and laboratory disposal area for Natick Labs, i.e., the U.S. Army Soldier Systems Center. A 1980s assessment led to this being categorized as an EPA “Superfund” clean-up site in 1990, as the site was contaminated with arsenic, pesticides and other chemicals. Extensive Army clean-up efforts continued for years, ending with the site being turned over to the U.S. Fish & Wildlife Service in 2000, to turn into a wildlife refuge.        

Tour of Bunker #303

The Refuge covers 3.5 square miles. The prime purpose is to manage land for migratory bird conservation. A website (www.farnwr.org) maintained by Friends of the Assabet River National Wildlife Refuge has maps, photos, activities, and a link to the government’s Refuge website. There is a wonderfully informative, child-friendly, Visitor Center at 680 Hudson Road, Sudbury. For people who just want to park and roam, the north parking lot is accessed from White Pond Road, reachable from Route 117 in Stow. Within the Refuge there are 15 miles of old roads and new walking trails, with the old roads, which are in poor repair, open to bicycles. No dogs allowed anywhere in the Refuge, no other pets, no horses, no fires, no overnight camping, no ATVs, no dirt bikes, no snowmobiles. Use of the Refuge is currently free, but that is likely to change. 

Back to deer hunting – this is an example of a need to manage a native species acting like an invasive species. Unrestricted hunting through the 1800s resulted in the New England extinction of wolves and mountain lions, and near-extinction of whitetail deer. But what with restrictions on hunting and return of farmland to wilderness, the state’s deer population is roughly 100,000 or 10 per square mile, and much higher in favorable terrain. Without population management of some sort, deer destroy ecological balance. ARNWR allows deer hunting so it will be a refuge for all wildlife, not just deer.

Trees growing on top of bunker, next to roof vent

One gray wolf made his way from Canada to western Massachusetts in 2007. Unfortunately he took up sheep killing rather than deer hunting, and was shot. A mountain lion walked from South Dakota to Connecticut, where he was then hit by a car in 2011. If more apex predators emigrate from the west then the Refuge will become a more interesting place to walk, as these animals hunt year round, including Sundays.     

Death by Exercise, Marathon, Triathlon

Sudden cardiac death – as in the college-age basketball player or the hyper-fit triathlon participant – tends to make the news. As it should. Newsworthy death while exercising provides every non-exerciser with rationale for not exercising. “See” they say, “this person was an avid runner [cyclist, swimmer] and dropped dead at 40.” The contrarian point being that the endurance sports that are supposed to protect against heart disease sometimes appear to do just the opposite.

There is an iota of truth to this observation. Estimates are that just under one person per 100,000 participating in a half-marathon or marathon, or 1.5/100,000 participating in a triathlon race will die during or immediately after the event. The great majority of triathlon deaths occur in the swim phase. Figure a collective three million participants in these types of races each year and that comes to maybe 30 deaths per year. There are fuzzier estimates of perhaps one sudden death per every million exercise event for other forms of exercise. So the true answer is yes, exercise can kill the physically fit, but no, not a risk factor worth avoiding exercise entirely.

There is more truth in the observation that exertion by the physically unfit can result in fatal cardiovascular events. The classic case is the middle-aged office worker who drops dead shoveling snow while attempting to clear the driveway and get to work. Contributing factors include the fact that blood pressure peaks in the morning a few hours after waking up, and the fact that exertion in cold weather constricts arteries, further adding to heart stress (triathlon deaths in cold water probably for the same reason). Snow removal related heart attacks frequently occur in women and men with no known pre-existing heart disease.

Exercise can also result in accidental death. In the U.S., walking, running, bicycling, swimming, boating and winter sports add up to about 10,000 deaths per year. Subtract half who are either children or are adults under the influence of alcohol (as in walking or riding a bike home from a bar, at night), and it’s still a big number. But the total pales compared to the 2,500,000 total deaths per year, of which many are premature cardiovascular deaths brought on by a lifetime of inactivity.

The good news is that benefits from even modest amounts of exercise are becoming clearer. In a 2011 article in The Lancet, C.P. Wen and co-authors reported that for a multi-year tracking study of 416,175 Taiwanese adults, as little as 90 minutes per week of moderate-intensity exercise reduced the risk of death by fourteen percent. Each additional 90 minutes per week added four percent further reduction. Other studies have also reported the greatest improvement for modest exercise compared to no exercise at all, and diminishing returns for progressively more exercise.

The theory that over-doing exercise may cause more harm than good has neither been confirmed nor disproven. A science journal article by Masaru Teramoto reviewed fourteen studies of longevity of elite athletes. Athletes from endurance sports had 3-6 year longer life spans than the general population, but the results were mixed for athletes in power sports. The latter may be disadvantaged by larger body size typical of their sport or from a discontinuation of exercise as they age. The authors caution that elite athletes may by genetically different from the population as a whole, with both their abilities and lifespan being consequences of their genes rather than one causing the other.

There is a non-fatal problem with exercise – it is potentially addictive. As one well-known fitness expert author put it, “…people reduce their lives to fitness routines, training as many as 40 hours a week. That the effort may wreck marriages and compromise immune systems isn’t even relevant. To these people – demographically a diverse lot – exercise is addictive. The more the body gets, the more it wants. In return, the drug of exercise infuses the swimmer, cyclist and runner with two powerful illusions: that he/she is escaping the horrible, and progressing toward the divine.”


Beyond the story: Exercise-related articles on this blog include "Avoiding Overhydration" (Feb 2010), "Hypothermia" (Nov 2010) and "Recovery from Donating Blood" (March 2011). For a detailed, referenced take on death from exercise, go to the entry "Sudden Death and Exercise", in the Encyclopedia of Sports Medicine and Science:  http://www.sportsci.org/encyc/suddendeath/suddendeath.html. 

Recovery from Donating Blood

Spring is when many endurance athletes start increasing training for events such as marathons and 100 mile bicycle rides. These athletes may hesitate to donate blood because they worry about compromising subsequent performance. The volume collected is 500 ml (about a pint) in most countries, with standard post-donation instructions not to exercise or do manual labor for a day or two, and to not donate again for 56 days. R research shines a light on the complicated timing of recovery from a blood donation.

A donation will have a different initial impact based on sex, size, age, and physical fitness of the donor. For example, a donation will be a much larger percent of total blood volume for a small, middle-aged, sedentary woman than it will for a large, young, athletic man. Men average 8 percent blood by weight, women 6 percent. The largest part of the difference is due to women having about 25 percent more body fat compared to men of the same athletic fitness. Age can also affect the impact of donating blood. As people age there is a trend for the amount of blood-rich muscle to decrease and for the amount of blood-poor fat to increase.

Taking an iron supplement or eating iron-rich foods will not speed recovery. With the exception of people who are iron deficient, there are adequate reserves of iron in the form of ferritin, an iron-rich protein to replace what was removed. The rate-limiting factor is how fast bone marrow can increase red blood cell production over the normal replacement rate.

A research article published in 2008 gives a picture of the donation recovery process in healthy young men. Dr. Torben Pottgiesser removed 550 ml of blood from 29 men and then measured plasma and total body hemoglobin twice a week. Plasma, the fluid part of blood, recovered within 1-3 days. This fast recovery of fluid volume is what most people think is all that affects exercise capacity. But plasma does not carry oxygen.

Hemoglobin, in red blood cells, is the protein responsible for transporting oxygen. In these men, hemoglobin did not even begin to recover in the first 5 to 10 days. It took, on average, 36 days for the subjects’ hemoglobin to return to the levels seen before the blood donation. The full range was 20 to 59 days; with 25 percent having recovered by 25 days, 50 percent by 34 days, and 75 percent by 46 days. Thus, for these young men the results support the standard practice of having donors wait at least 56 days before donating blood again. The equivalent experiments have not yet been published for women or older donors.

In theory, at anything up to moderately vigorous exercise there will be no difference in perceived exercise capacity. The heart will beat faster to compensate for less oxygen-carrying capacity per heart beat. However, the high end will be compromised. Amateur cyclists were tested before and after a blood donation. At seven days, donated hemoglobin was down 6.7 percent and maximum exercise as measured in watts output was down 7.1 percent. Unfortunately, no testing was conducted beyond seven days.

Thus, on a practical note, anyone planning to compete in a long-distance endurance event should not schedule a blood donation during the final eight weeks leading up to the event. Training can resume within a few days after the donation with the understanding that training performance will likely be compromised for weeks.

Calories in Human Blood

As of Dec 2018 >21,600 visits have been made to this post on calories in human blood. "Article Directory by Category" lists other health-related topics. From main page to 2011 will get to Recovering from Donating Blood (March 2011) and Death by Exercise (Sept 2011).

CALORIES HUMAN BLOOD or HUMAN BLOOD CALORIES:  The standard U.S. blood donation is 500 ml and weighs a tad under 1.2 pounds. Nutritionists tell us that losing one pound is equivalent to losing 3,500 calories. Does this mean that donating blood is a good way to start a diet? The answer is "No," because blood is mostly water, and thus not 3,500 calories per pound. To cut to the chase - a donation contains roughly 450 calories. There is an energy cost involved in synthesis of replacement cells and non-cellular (plasma) proteins, which means a replacement total would be higher. Details of the math:

Blood tests always include hematocrit - the percent of blood that is cells versus the percent that is liquid, determined by spinning a tube of blood in a centrifuge to pack the cells to one end. Whatever percentage that is not packed cells is plasma. Men's blood has a lower plasma content (55%) than women's blood (60%) because men have more red blood cells, i.e., a higher hematocrit than women.

First calculate calories for plasma. Blood is denser than water by six percent, so multiply that 500 ml donation times 1.06 to get to grams (because calorie content will be calculated from grams). Multiply that by 55/100 for men or 60/100 for women to get to grams of plasma. Now, multiply that by .07, because plasma is only 7% protein, to get to grams of protein. Finally, multiply that result by four to get protein calories. Answer in the 80’s? Good.

Now for sugar in plasma. Normal fasting blood sugar is around 0.09 grams per 100 ml of plasma (more familiarly expressed as 90 mg/dl). Multiply the amount in grams time 2.75 for men or 3.00 for women, i.e., equal to how many hundreds of mls of plasma there are in 500 ml of blood, and then times four to get to calories. Result should be one calorie. Blood is not sweet!

As an aside here, for most people only 20 calories' worth of glucose (sugar) is circulating in the blood at any given moment, with the exception of after a meal, when there is a bump up for a few hours.. Muscle and other organs are constantly adding or withdrawing glucose to maintain this constant amount. For people with diabetes, excess sugar is poorly removed from circulation, leaving the sugar molecules to inappropriately attach to proteins, i.e., glycosylation, causing cumulative damage. Measuring blood sugar gives a real-time picture. Measuring hemoglobin A1C - glycosylation of a blood component - assesses long-term control.   

For plasma calories from fat, use 0.5 grams per 100 ml of plasma, times hundreds of mls of plasma, times nine - for calories from grams of fat - to get to calories. The 0.5 g/100 ml covers triglycerides and fatty acids in lipoproteins but not cholesterol, as cholesterol is not metabolized for energy. Result is roughly 12 calories.

Next comes calories from red blood cells. RBCs are mostly water and protein, the protein almost entirely hemoglobin. Hemoglobin does not conform to the rule of four calories per gram because the heme portion of the molecule is not metabolized for energy. Use average hemoglobin values of 160 g/L for men or 140 g/L for women, multiplied by 0.5 to get to the blood donation volume of 500 ml, multiplied by 0.96 to correct for using only the non-caloric heme portion of the hemoglobin molecules, then multiplied by four to get to calories. But wait! Hemoglobin is only 90% of the dry weight of RBCs. Multiply one-tenth the amount of the hemoglobin weight in 500 ml times six (see below for why six) and add that to red blood cell calories.

Finally, estimate calories for the other types of cells. Of the 500 ml blood donation, roughly one percent will be white blood cells and platelets. Figure five grams, times one-third to get to dry weight, times six, to get to an estimated 10 calories. The "times six" is because some of the dry weight is protein or carbohydrates, which both have four calories per gram, and some is fat, which is nine calories per gram.

Add everything up. The total should be approximately 425 calories for women and 460 for men. Anemia would result in a lower value. Use of EPO or NESP, drugs which unethical athletes can use to increase their red blood cell count and thus their oxygen transporting capacity, would result in a higher value.

All in all, the calories removed in a unit of donated blood are less than the equivalent of one normal-sized meal. The actual energy cost of making new blood will be higher than this calculated calorie content, as synthesis is not 100% energy efficient. But keep in mind that even without a blood donation, the body replaces about 1% of red blood cells every day. So the excess energy needed to replace a donation of roughly 10% of one's blood supply is not large, and takes place over four to eight weeks.

During prolonged vigorous exercise it is possible to deplete the easy to access stores of energy in the form of glycogen - a precursor for glucose - and not be able to metabolize fat or protein fast enough to keep up with demand. The transition from fueled to empty is quick and the consequences dramatic. In the U.S. the condition is referred to as 'bonking,' or 'bonked.' Marathon runners used to call it 'hitting the wall.' When circulating blood sugar drops, the brain, which relies solely on blood sugar, crashes. Recovery is slow, because even if the athlete stops moving and rests, any sugar being made by muscles or liver tends to get used locally before it gets to the brain.   

BLOOD AS FOOD: Blood, human or otherwise, can not be considered a nutritionally complete or balanced food for humans, as it is lacking in essential fatty acids and sufficient carbohydrates, has too much protein, and does not provide sufficient vitamins, minerals or fiber. Vampire bats get by, but to do so they have to consume more than a third of their body weight in blood every night. And pee a lot. As for vampire calorie requirements, if vampires have the same caloric needs as (living) humans then it would take five units a day (a night?) to keep a vampire in caloric balance. But given that vampires have no resting metabolism calorie requirements (they’re dead, remember?) calorie needs are probably much lower.

Non-human blood is featured in many traditional dishes from around the world. Blood sausage combines blood with grain and spices. Note that boudin blanc the popular Cajun sausage uses pork livers and hearts, rice and spices, but not blood. The boudin noir version uses blood. Blood is used as a soup ingredient in many cultures. In Eastern Asia, blood is allowed to congeal in shallow trays and then cut into squares. This is called “blood tofu” and used in many stir-fry dishes.

Calvin Trillin, renowned food writer, oft told of his frustration at being in a Chinese restaurant in the U.S. and not knowing what the choices meant on the Chinese-language parts of the menu. When he tried pointing at the entries the waiter typically replied "You no like." So if you see 血豆腐 on the Specials menu, likely, you no like. It translates as pig's blood tofu.