Human Cogeneration: Generating your own Heat and Electricity

Published on 2023-01-21 by Jim Gregory
reading time: ~8 minutes

Schematic diagram of conventional cogeneration above that of human cogeneration.  The conventional cogeneration diagram shows the power plant as a larger building and a home as a small building.  They are joined by a wire and hot and cold water pipes which is connected to a radiator in the home.  Heat given off from the radiator is depicted as red arrows.  The human cogeneration diagram shows a stick figure sitting at a computer desk pedaling a generator.  Electricity from the generator is depicted as a lightning bolt, and heat given off from his body as red arrows.
conventional cogeneration vs human cogeneration

Most fossil-fueled power plants convert less than 40% of the energy they consume into electricity. The remaining 60% is lost as heat. To increase efficiency, some power plants capture a portion of this waste heat and put it to use elsewhere. This combined generation of electricity and useful heat is called cogeneration or combined heat and power (CHP).

A typical example is a power plant teamed with a district heating system, which I've illustrated in the top half of the figure above. Here, steam or hot water is extracted from the power plant's waste heat and piped through the radiators and heat exchangers in nearby buildings, providing them with heat and domestic hot water.

Cogeneration also occurs whenever you pedal a generator in a cool environment. The human body is only about 20% efficient at converting food into useful work. The remaining 80% is given off as heat, in a process known as exercise activity thermogenesis (EAT). This EAT-derived heat both makes you warm and helps heat the area around you, too, as shown in the bottom half of the figure.

I call this simultaneous production of heat and electricity while pedaling a generator human cogeneration. It is uniquely differnt from conventional cogeneration, and offers some energy-saving opportunities that are worth exploring.


Fixing Higher-than-Normal Voltage Readings

Published on 2023-01-08 by Jim Gregory
reading time: ~4 minutes

pictorial schematic of circuit board, fuse holder containing a fuse, and the battery
The connections between the circuit board, fuse holder, and the battery

On the PedalPC, the power sockets and battery are all wired together in parallel, so all loads plus the battery are at nearly the same voltage. The circuit board on the PedalPC measures this voltage constantly, using it to calculate the power the generator produces and each device consumes. When the voltage gets above a certain threshold, it disconnects the generator from the power sockets and battery to prevent damaging them. It's therefore crucial that this voltage measurement be accurate.

I recently noticed the voltage on my machine creeping higher than normal at any given state of battery charge. (Voltage is proportional to a battery's state-of-charge—the greater its charge, the higher its voltage will be.) This made charging the battery more difficult, as I had to reduce my pedaling cadence to prevent the voltage from rising over the threshold cutoff. If I didn't, the generator would disconnect.

It also lengthemed the time required to charge the battery, because my reduced pedaling speed lowered the generator's power output.

Here's what was causing the voltage to creep upward, how I fixed it, and what I should have done differently.


How to Determine How Much Electricity Your Equipment Uses

Published on 2022-12-28 by Jim Gregory
reading time: ~9 minutes

plug-in AC power meter on left, USB power meter on right
AC and USB power meters (sources: P3 International / DealExtreme

The first step to becoming more energy self-sufficient is knowing how much electricity you use. Without that knowledge, you won't know how much electricity you need to generate.

But finding accurate information on how much electricity a particular device uses is often difficult. Manufacturers seldom provide this information in their promotional material or documentation.

Here are four different ways to determine how much electricity each device you have uses. Which one works best for you depends on what equipment you have, what data is available, and how accurate you need to be.


Surviving a Power Outage With a Pedal-Powered Generator

Published on 2022-12-12 by Jim Gregory
reading time: ~3 minutes

power pole broken in half with power lines still attached
damage from the August 10, 2020 derecho

What is the best, most reliable method of getting electricity during a power outage?

Having solar panels on your roof might seem like the best solution, but most homes equipped with solar panels don't have a backup battery. For safety reasons, such homes won't produce any power when their connection to the grid is lost.

But even off-grid solar homes are vulnerable to natural disasters. Strong winds can tear off solar panels. Flying debris and falling trees can break them. Deep snow can block them.

Gasoline or diesel backup generators have their own problems. They can be annoying loud. They can't be used indoors due to their toxic exhaust gases. During a crisis, fuel may be hard to get.

A pedal-powered generator has none of these problems. It's portable, so you can move it to a safe location in threatening weather. It's not tied to the grid, so power outages don't effect it. It can safely generate electricity indoors or out. It requires no extra fuel (other than food for the user), is reasonably quiet, and produces no fumes. It's very reliable, generating the same amount of power regardless of weather conditions or time of day. And while it may not be able to produce as much power as other methods, it can generate enough to meet many important needs.

We've experienced several power outages over the 12 years I've powered my home office with a pedal-power generator. Most were so short I didn't even notice. But a serious storm a couple of years ago was different, and proved how useful a pedal-powered generator can be.


How Much Electricity Can A Human Generate Per Day?

Published on 2022-12-07 by Jim Gregory
reading time: ~9 minutes

a refrigerator covered by an 'X'; a microwave and toaster covered by a '?'; and a cell phone, laptop, battery-powered light, and mini-router surrounding a check mark
Examples of what can and cannot be human-powered

One of the first posts on this blog answered the question how much electricity can a human generate. That answer, in retrospect, was incomplete. It calculated only the electrical power a person could generate, not the electrical energy.

Energy is the product of power and time. It is a more accurate measure of a human-powered generator's feasibility, because it takes into account both how hard and how long you have to pedal to power a device or appliance.

So this post again answers the same question, but this time from an energy perspective. It also considers how you could use this electricity plus the additional equipment you'd need to use it.


The Difference Between Energy and Power

Published on 2022-11-22 by Jim Gregory
reading time: ~6 minutes

Robert Förstemann standing on balcony in front of bike on left, Ed Begley stradling a bike in front of his home on right
The hare and the tortoise: Robert Förstemann (left) and Ed Begley Jr (sources: todaycycling / Pinterest)

The terms "energy" and "power" are often confused, especially in articles by journalists who should know better. Knowing the difference between these two terms is critical to making good energy-related decisions. Here's what the two terms mean, why they are often confused, and an example showing why the distinction is important.


Human-Powered Broadband Internet and Web Server

Published on 2022-09-20 by Jim Gregory
reading time: ~10 minutes

black mini-router with two attenna and white ONT box sitting on clear plexiglass table
our broadband networking equipment: optical network terminator (ONT) (right) and mini-router

I described in an earlier post how I used a pedal-powered generator to generate the electricity needed to power the DSL modem/router and web server that serves this web site.

While this worked, our internet service's slow upload speed caused problems. Pages took too long to load for most visitors to our site [1]. We couldn't video chat with family, friends, or customers, either.

But I was hesitant to upgrade to higher-speed internet service. Every service option required considerably more power than the 2.9 W our DSL modem/router did. I was already pedaling my old generator over 4 hours each day; for every extra watt a high speed internet connection required, I would need to pedal 40 minutes per day more. I didn't want to pedal an additional couple of hours each day just to reduce this site's page load times or engage in a video chat a few times a year.

In the end, I came up with a solution that significantly upgraded our internet service, made our server more secure, and lowered the amount I had to pedal each day.


Changing Generators

Published on 2022-04-04, updated on 2022-08-19 by Jim Gregory
reading time: ~8 minutes

toothed pulleys and belt mounted on pedal-powered generator
The new toothed pulleys and belt on my pedal-powered generator.

Early prototypes of the PedalPC used a chain-driven direct-drive Conhis Motor electric bike hub motor for it's generator. In 2014, I dropped this motor in favor of a Bofeili mid-drive E-bike motor instead. I preferred the Bofeili because it was compact, fully enclosed, and reasonably quiet.

I thought it was the ideal pedal-power generator. But a sequence of events over the past two and a half years has led me to change my opinion.

In this post, I will describe why I originally chose the Bofeili over the hub motor, the sequence of events which caused me to return to using a hub motor, and the improvements I made that now make it my preferred choice.


Pedal-Powered Home Lighting

Published on 2022-02-28 by Jim Gregory
reading time: ~14 minutes

We have illuminated our home using human-powered electricity for the past several years. Battery-powered LED lights in rooms and hallways around our house provide the light we need at night. I recharge their batteries using the generator on my pedal-powered computer.

Lighting your home this way has many advantages:

  1. It uses 100% renewable energy.
  2. Your lights never go out when the power fails.
  3. You can recharge the batteries any time, even when it is dark outside or the weather is poor.
  4. You can put lights anywhere in your home, including areas without light fixtures or power outlets.
  5. The lights are portable, so you can move them whenever you feel like it.
  6. It provides a daily source of exercise.
  7. Your original lighting system is maintained, which you can continue to use when and where you prefer.
  8. No building modifications are necessary, making this lighting system an option even if you rent.

In short, a human-powered home lighting system using battery-powered LED lights allows you to have a completely reliable, off-the-grid, renewably-powered home lighting system, regardless where you live.

In this post, I will describe the battery-powered LED lights, rechargeable batteries, battery chargers, and the pedal-powered generator we use to provide most of the lighting needs for our home.


Latest PedalPC Improvements - Variable Power Output, New Case, New Server, And More

Published on 2021-04-10 by Jim Gregory
reading time: ~7 minutes

PedalPC desktop with heated beverage cup
You can now heat your favorite beverage using the PedalPC while you work.

I made four improvements to the PedalPC over the last year. They are:

  1. New pulse-width modulation option on 12V DC power sockets and fan, for improved power management;
  2. New web server, for easier upgrades;
  3. New 3D-printed case with integrated phone shelf, to improve the PedalPC's appearance and functionality; and
  4. Re-designed control board, to add more power ports and make it easier to re-flash the firmware.

Read below to learn more about them, as well as others I hope to implement later.


This Website is Pedal-Powered

Published on 2019-12-21, updated on 2021-11-08 by Jim Gregory
reading time: ~21 minutes

This website is 100% human-powered. I use a pedal-powered computer in my home office; the excess electricity I generate each day while working is stored in a storage battery built into the desk. This battery powers this website's web server and the modem connecting it to the internet when I am not pedaling. You can find details on how the system is set up here.

photo of my pedal-powered computer, web server, and modem
my pedal-powered computer, web server, and modem

The battery icon in the header of every page on this site displays the current state-of-charge of the battery. If the icon is green, I'm currently charging the battery. If it's red, I'm not. The icon is updated every 10 minutes.

I got the idea to do this from an article Kris De Decker wrote about how he uses solar power to power his Low Tech Magazine website. One difference between Kris's setup and mine is that my origin server is entirely off-the-grid, while Kris depends on a grid-powered router.

Pedaling Time

The biggest challenge to operating a human-powered website is generating enough electricity each day to keep the site up. The energy stored when pedaling must be sufficient to keep the web server and modem up for the remainder of the day. Assume S is the surplus power generated while pedaling, L the power the web server and network equipment consumes when not pedaling, e is the storage efficiency of the battery, and t is the number of hours spent pedaling each day. Then:

energy stored when pedaling = energy consumed when not pedaling
                  S x e x t = L x (24 - t)
            (S x e + L) x t = 24 x L
                          t = 24 x L / (S x e + L)

My web server and modem draw 6 W combined, and my LiFePO4 battery is about 95% efficient at storing electricity. When I'm working on my computer, I generate, on average, 33 W more than my load requires. Then the amount I need to pedal each day to keep this server up is:

                          t = 24 x 6 / (33 x 0.95 + 6) = 3.86 hours

Since I currently work on my computer about 4 hours a day on average, this has yet [1] to be a problem.


How the PedalPC Works

Published on 2019-11-11, updated on 2024-05-20 by Jim Gregory
reading time: ~11 minutes

My pedal-powered computer desk, which I call the PedalPC, is composed of six parts:

  1. desk frame
  2. generator
  3. battery
  4. control board
  5. power sockets
  6. single-board computer
The PedalPC stand and powerbox, highlighting its six major parts
The six major parts of the PedalPC

Each part is described below, followed by a brief description of the software that controls the desk.


Why You Should Use a Pedal-Powered Computer at Work

Published on 2019-11-06 by Jim Gregory
reading time: ~6 minutes

There is probably nothing that will improve your health more than doing aerobic exercise. It can help you:

  1. Keep off excess weight
  2. Increase stamina, fitness, and strength
  3. Ward off viral illnesses
  4. Reduce your risk to many chronic diseases (heart disease, type 2 diabetes, stroke, etc)
  5. Manage those chronic conditions
  6. Strengthen your heart
  7. Keep your arteries clear
  8. Boost your mood
  9. Stay active and be independent as you age
  10. Live longer

Medical societies and health agencies recommend a minimum of 150 minutes (2.5 hours) of moderate aerobic exercise every week. These are activities like walking, bicycling, gardening, etc that raise your respiratory and heart rates to the point where you can still carry on a conversation but not sing.

It's worth noting that 2.5 hours/week is the recommended minimum--some health researchers recommend at least an hour a day to maintain a healthy weight. Longer duration produces even greater benefits.

plot showing reduction in mortality with increasing amounts of exercise
Reduction in all-cause mortality vs daily moderate exercise duration
(from Minimum amount of physical activity for reduced mortality and extended life expectancy: a prospective cohort study)


How Many Calories Do You Burn When Using a Human-Powered Generator?

Published on 2019-11-05 by Jim Gregory
reading time: ~10 minutes

One of the benefits of using the PedalPC is the ability to exercise while you work. Since a common goal of exercise is to control your weight, it's natural to ask, "How many calories do you burn using a human-powered generator like the PedalPC?"

In this article, I'll look at what factors influence your calorie expenditure when using a human-powered generator, the different ways to measure it, and how the PedalPC measures it.


How Much Electricity Can a Human Generate?

Published on 2019-11-04, updated on 2022-08-05 by Jim Gregory
reading time: ~8 minutes

I took part in an exercise study several years ago that measured the effect of a nutritional supplement on human performance. As part of that study, the investigators measured my power output while pedalling a stationary bike. It was over 300 watts.

And yet, when I'm working at my pedal-powered computer desk, I'm only able to generate 60-70 W of electricity. Why is it so much lower?

There are multiple factors that influence how much electricity you can generate using a pedal-powered generator. Some are biological, some depend on the design of your generator. Let's look at them one-by-one.


My Human-Powered Office

Published on 2019-11-03, updated on 2021-09-22 by Jim Gregory
reading time: ~11 minutes

my pedal-powered generator desk and office equipment
my human-powered office

I have used a pedal-powered generator to power my home office since 2010 (You can learn why here.) Since I can only generate about 60 W of electricity when working at my desk, I need to pick my equipment carefully.

Below is a description of the equipment I use in my office. I include some issues to consider if you are thinking of setting up your own human-powered office. None of the links in this article are affiliate links.

I conclude with a description of my typical workday.


How to Program a PIC Microcontroller Using a Raspberry Pi or Orange Pi

Published on 2019-10-29 by Jim Gregory
reading time: ~12 minutes

I have used PIC microcontrollers on many projects, including the PedalPC. I like using them because:

Compiling programs for PIC microcontrollers is easy on a low-resource single board computer like a Raspberry Pi using open-source program languages like Great Cow Basic or JAL. (I may describe how to do this in another post).

The challenge is how to get the compiled programs onto the chip. The usual technique is to use a dedicated external device (called a programmer) that attaches both to your computer and to the chip and transfers the compiled program into the memory of the microcontroller.

These programmers can be somewhat expensive (usually at least $30) and are another piece of specialized hardware you have to keep around.

However, with the right software and a few resistors, you can transfer your programs directly to your PIC using the GPIO pins of a single-board computer (SBC) like a Raspberry Pi or Orange Pi. This can be very useful if you are already using a SBC to read data from the PIC, like I do on the PedalPC.

In this tutorial, I will explain how to:

The in-circuit serial programming (ICSP) software we'll be using in this tutorial is an excellent utility called Pickle written by Darron Broad. It works with many single-board computers running Linux, and requires only a few resistors to successfully program most PICS at 3.3V. (Programming a 5V PIC in-circuit will require an inexpensive 4-channel 5V-to-3.3V logic level converter, which are widely available on eBay and other sites.)

This method works only with PIC microcontrollers that can be programmed using the low-voltage programming (LVP) method, which includes most common PICs in use today. (Darron has a list of supported PIC microcontrollers on his site as well as a large table of PICs that have been tested.) It will not work with older chips that require the high-voltage programming (HVP) method. For those chips, you'll need a programmer, not just a few resistors or level converter.