Tag Archives: electronics

Human Power: That Other Renewable

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Bike-powered peanut sheller and blender

Of all the renewable energy sources available today, one of them is constantly overlooked by modern society. It’s a shame, because this renewable energy is easy to harness, uses little space, and is complementary to wind and solar energy. I am speaking about that other, forgotten renewable: human power.

Using machines like a hand-crank, treadle, or pedal, human labor can be harnessed as mechanical or electrical work. The most common human-powered machine is the bicycle: mechanical work from a pedal is used to turn a wheel, which propels the rider forward. Bicycles, however, are not the only possible human-powered machines. With some clever engineering, human power has been harnessed to crank washing machines, plow fields, and saw wood. A bicycle can even generate electricity if equipped with a generator, voltage regulator, and battery. It can then power light bulbs, flashlights, laptops, and vacuum cleaners.

Hand-cranked and solar flashlight and radio


Hand-cranked red pepper processor

Unlike other renewable energy sources, human power requires active labor. Modern society, with its distaste for exercise in general, rejected human-powered machines for this very reason. That’s a shame, because human-power provides a nice complement to solar technology. Pedal-power can provide a handy back-up to photovoltaic panels on cloudy days. What’s more, pedal power can create short bursts of electricity, in contrast to the steady-stream of low power provided by solar panels.

An illustration involving an LCD monitor can provide perspective. A typical monitor requires around 100W of power to operate. After cloud cover and the earth’s tilt are considered, a photovoltaic panel might produce a power of around 25W/m^2 on average (1). So to power the monitor, we would need 4m^2 of solar panels. It only takes a single stationary bicycle, however, to generate 100W. Space is only needed for the bicycle itself and a few electronics, so the whole system can be contained in around one square meter. A fit cyclist, moreover, can produce even higher rates of sustained power — up to 200W in athletes. As a result, a well-trained cyclist can produce twice the energy of a photovoltaic panel in one-fourth of the space.

Pedal-power is not unreasonably expensive. A stationary unicycle can be built for under $250, and accompanying electronics can be purchased for around $400 (2). The combined total is $650, roughly the cost of similar solar panel installations.

The real cost savings, however, are for appliances that require only mechanical power. When there is no need to purchase expensive electronics, pedal power is clearly cheaper, since these machines can be built using only donated bicycles, spare hardware, and elbow grease. One NGO based in Guatemala, Maya Pedal, has taken discarded bikes and retrofitted them to make useful tools for local farmers. Old bicycles have been used to blend soap, pump water, grind flour, shell peanuts, and thresh grain. Not only has this removed the drudgery of agricultural work, it has also increased the income of local families. These projects promote development without burning extra gasoline or coal, all while recycling old garbage.

The Western world could learn a lesson. We chronically suffer from energy shortages, and we have no lack of people needing exercise. In the United States, more than one in four Americans are obese, and six in ten overweight. Cheap energy has allowed us to live sedentary lifestyles, which shorten our lifespans and waste trillions of dollars on unnecessary healthcare. If couch potatoes were forced to pedal for their television time, the rates of Western diseases — heart attacks, strokes, diabetes, and cancers — would rapidly plummet.

This is much better than going to the gym. Not only does gym membership cost thousands of dollars, but workout machines like treadmills actually waste additional energy to power. The average treadmill consumes 1500W of power — enough power to run 20 laptops. When people drive to the gym, moreover, they further add to greenhouse gas emissions. With human-power, they could instead burn their extra fat for productive purposes. Those calories might as well be used to wash clothes, blend smoothies, and generate electricity. Why not combat global warming while getting in shape?

Pedal-powered washing machine

Whether human power can truly make a difference depends on the efficiency of the exercise machine and the power demanded by your household. The average person can produce around 35-60W of power using a hand-crank, and 100W-120W using pedal power. Cell phones, flashlights, and watches can all be powered by hand-crank, while computers and televisions can be powered by pedals.

This sounds promising — that is, until you consider our monstrous demand for power. A medium-sized, window air conditioner uses around 1000W of power. To supply the energy for just that one AC unit, it would take a team of ten cyclists pedaling at full speed for the entire day. Once you add in laptops, televisions, clothes driers, washing machines, heaters, and light bulbs, human power becomes woefully inadequate. It would take a legion of cyclists to support the typical American home.

Storing generated electricity is a problem as well. Most pedal generators use lead-acid batteries, which store energy for later use. Devices can then be plugged into the battery rather than directly to the exercise machine. This helps avoid the awkward situation of having to simultaneously pedal while using your laptop. But as Low Tech Magazine points out, lead-acid batteries require massive amounts of energy to manufacture. Sulfuric acid can also cause severe burns, and lead can cause birth defects and brain disorders. Even pedal-powered electricity, then, isn’t perfectly green.

This limitation can be largely overcome by simply transmitting work mechanically rather than electrically. One clever hobbyist retrofitted his bicycle to spin washing machines using only pulleys and belts. The Human Powered Home, a compendium of do-it-yourself pedal-powered machines, provides plans for mechanically connect your bicycle to a grain mill, sewing machine, and tool sharpener. With a little ingenuity, the mechanical applications of pedal power are endless.

Pedal-powered jig saw

Despite its flaws, human-powered electricity can still contribute to sustainable living. Every renewable technology has its limitations, and a human-powered generator is no exception. They may not be perfectly green, but neither are solar panels. When used properly, the benefits of renewable, off-grid electricity can outweigh the harm caused by pedal-power electronics.

Generating your own electricity can allow you to live off the land, which dramatically reduces your carbon emissions. One difficulty with living on rural, undeveloped land is the lack of grid electricity. Pedal power, along with photovoltaic panels, can provide electricity without an expensive connection to the utility company. One Laptop Per Child, for instance, has taken advantage of human power to design off-grid laptops. Students in remote villages often lack access to electricity, but one minute on a hand-crank can provide enough energy for ten minutes of laptop use.

Yet the most profound impact of human power is not the generated electricity itself, but rather the conservation ethic it instills. Producing electricity is hard work. When we hook up an appliance to a power outlet, we are blind as to how much energy we are truly wasting. But if we had to pedal forty-five minutes for each hour of television we watched, we would be more conscious about our electricity usage. We would never have to be reminded to turn off our lights or to sleep our computers, and few would dream of using an air conditioner. Ultimately, it’s conservation — in addition to our feet — that will provide us with the power to lower our carbon footprint.

Do-it-yourself bicycle-power plans are the most affordable and have the lowest environmental impact. There are also some commercially-available attachments. They are expensive, however, and may actually waste more energy than they produce. I encourage you to build your own instead.

  1. Sustainability: Energy: Without the Hot Air generously estimates that a solar panel in Britain produces around 22W/m^2 on average. Low-Tech Magazine estimates a power capacity of 100-150W for average cyclists and up to 300W for athletes.
  2. The Pedal Powered Prime Mover is one unicycle designed especially for pedal power. It costs around $100-$250. The exact electronics will vary depending on your needs.
  3. Photo credits: Alan Levine, CC BY. Engineering for Change, CC BY. AIDG, CC BY-NC-SA. AIDG, CC BY-NC-SA. Donkeycart, CC BY-NC. Bruce Turner, CC BY.

Energy-Efficiency Is Not Enough

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The IT industry now wastes as much energy as the airline industry (1). This is an enormous environmental problem because most of the electricity in America is generated from coal power plants. Not only is coal a non-renewable resource, but it’s a far dirtier polluter than gasoline. As a result, the electronics industry has made an attempt to produce energy-efficient devices. Logically, we would therefore expect our total energy consumption to decrease. Yet the exact opposite is occurring. In fact, given its current rate of growth, IT might even become one of the top energy hogs of the 21st century.

How do we make sense of this energy paradox? Here’s one possible explanation: As devices become more energy-efficient, we start using them more often. Any potential savings that technology would have enabled, we throw away by increasing our consumption.

Energy is a product of power usage and operating time (Energy = Power × Time). To make this equation easier to grasp, think of electricity usage like running water from a faucet. Power corresponds to the flow of water, and energy corresponds to the volume of water. There are two ways to conserve water (energy): we can slow down flow (the power), or we can limit how long the faucet is open (operating time). Likewise, energy (water volume) is a product of power (flow rate) and time. If we want to conserve energy, we must decrease either power usage or time.

At first glance, our power usage appears to be decreasing. Back in the early 2000s, a desktop computer with a CRT monitor drew around 350W in power. Today, the average desktop and LCD monitor requires only 150W, 60% less power than its predecessor. By itself, this would represent a huge savings in energy. But the problem is that while each individual device uses less power, we now own far more devices than ever before.

It’s not unusual today for the average household to own dozens of computers. Long-gone is the era of the family computer; everyone now owns his own personal desktop and laptop. The average household is also flooded with non-traditional computers: tablets, smartphones, video game consoles, digital video recorders, mp3 players, GPS devices, and routers. Some computers are embedded in everyday items, hidden inside cars, microwaves, refrigerators, toaster ovens, and even clothing. Each computer also comes with a set of digital peripherals: external hard drives, speakers, LCD projectors, webcams, and printers. When the power ratings on all these devices are summed up, it turns out that total power usage per person hasn’t dropped much in the last decade. It might even have increased.

A similar effect is also negating the benefits of power management. To conserve energy, many of our digital appliances now enter sleep mode automatically when idle. This reduces the amount of time a device operates. But in spite of power management, we’re still powering our computers for longer than ever. It’s common to use a computer for 10+ hours each day, every day of the year. Perhaps equally important, a greater percentage of the world is starting to embrace digital appliances. Developing nations, especially India and China, are acquiring computers in large number and plugging into the hydrocarbon-powered electrical grid.

This paradox exposes why typical solutions to environmental problems often fail. Relying entirely on technology to solve cultural issues is counter-productive. The core problem isn’t a lack of energy-efficiency; it’s a lack of conservation ethic. Better technology — telecommuting, search engines, videoconferencing, and digital downloads — can be totally undermined by bad habits. Energy-efficiency only works when we don’t increase our consumption to match.

  1. The computer industry produces is responsible for 2% of the world’s carbon emissions, which is the same as the airline industry. So approximately, they use the same amount of energy. See COSN.
  2. A related phenomenon is known as the Jevons Paradox. William Jevons lived during the Industrial Revolution, a time when steam engines had just become practical. These steam engines wasted massive amounts of coal, so engineers were working to improve their efficiency. But Jevons predicted that any increases in efficiency would only result in more coal use, not less. This is because more efficient devices become more affordable to operate, and hence improved steam engines would be operated by more factories for longer periods of time. Hence, improved technology by itself can’t solve any energy problems.

Powering Off

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Play a board game instead of watching TV.

Electricity from renewable sources can never solve our energy problems completely. The most obvious reason is because setting up all that high-tech infrastructure—photovoltaic cells, hydroelectric dams, wind turbines—is extremely expensive. New technology costs money both to develop and to build. Today, many homeowners are looking to retrofit their existing houses with solar panels. However, the installation can easily cost tens of thousands of dollars, even when solar panels are subsidized by the government. It can take decades before the solar panels recoup their investment costs. So when it comes to lowering your environmental impact on the cheap, the best tactic is still old-fashioned, low-tech conservation.

Every effort you make towards conserving energy will be passed back to you as savings. A household electric bill of $100 per month translates into $1200 per year. With some minor effort, it’s possible to quickly save over $1000 each year just by changing old habits. After all, if you’re going to be conscientious about your carbon footprint, why not earn a little reward for your trouble?

Here’s a chart of how much energy (and money) you could save each year by powering off:

Energy and money saved per year from powering off (1).
Appliance Alternative Energy Savings
Central Electric Furnace Thicker clothing and blankets, small space-heater 5690kWh $853.20
Central Air Conditioning Lighter clothing, fan, window AC unit 2520kWh $378
Electric clothes dryer Clothes hanger, clothesline 1370kWh $205.90
Lights Natural sunlight, appropriate lighting 1095kWh $164.25
Refrigerator Smaller fridge, cellar 630kWh $94.60
Television Boardgames, books, sports 365kWh $54.75
Treadmill Outdoor running in backyard, parks, trails 225kWh $33.75
Desktop PC and Monitor Boardgames, books, sports 220kWh $32.85
Xbox 360 “   ” 135kWh $20.25
Theater Speaker System “   ” 125kWh $18.60

Whenever possible, use a low-tech, electricity-free alternative. Whenever that’s impractical, use your appliances sparingly. These are the two key tactics for reducing electricity waste without spending extra money. All it requires is a change in mindset. Electricity appears to be unlimited and practically free, but it’s actually coming from power plants burning coal. So conserve and use sparingly.

Low-tech solutions are the techniques people once used prior to electricity. Sometimes the answer is very obvious. Before the clothes dryer, laundry was hung on clotheslines. Rather than turn on central heating, people often wore extra sweaters and used thicker blankets during a mild winter. Sometimes the low-tech solution will surprise you. It might encourage you to live without television, or even a refrigerator. Since certain appliances are much easier to live without, tackle the easy ones first. Limit central heating and air conditioning, hang-dry your clothes, and tune out mass media from your life–TV, music, video games, and web surfing.

If it’s impractical to eliminate a device, downsizing is the next best tactic. Reduce electricity use as much as possible by powering off redundant appliances. For example, I don’t own any electronic accessories besides my laptop. I have no cell phone, external hard drives, monitors, speakers, or mp3 players draining extra power. Some larger houses have two refrigerators; if you buy less processed food, you can unplug one of them. Washing laundry in cold water saves electricity used in heating. If you use a space heater, you won’t be wasting money by heating unoccupied space. Lastly, try to use natural sunlight in place of light bulbs. Keep as many appliances unplugged as possible.

The technology for sustainable living is already here at an affordable price. We can reduce our carbon emissions while saving money; it just takes getting used to the idea that big, complicated, and expensive isn’t always better. We need a willingness to embrace what our culture, perhaps, is most afraid of embracing: powering off.

Michael Bluejay explains electricity, how to calculate the power a device uses, and how much it costs.

1 To calculate energy used, take the power rating (in Watts), multiply it by the number of hours used per day, then by the number of days in a year. Divide this by 1000 to obtain the energy in kilowatt-hours (kWh). The cost of energy is roughly 15¢ per kWh. Here are my assumptions for the following devices:

Appliance Power Rating Hrs/day Days/yr
Central Electric Furnace 7900W 8 90
Central Air Conditioning 3500W 8 90
Electric Clothes dryer 4400W 6hrs/wk 52wk/yr
Lights 25W 12 365
Refrigerator 72W 24 365
Television 250W 4 365
Treadmill 1500W 1 150
Desktop PC and Monitor 150W 4 365
Xbox 360 185W 2 365
Theater Speaker System 170W 2 365