electricity from a gym: quick calcs

[[email protected]]

I had a conversation with a co-worker about harnessing energy from
folks dancing on a dance club, and from folks walking in a mall during
the shopping season. I was skeptical, thinking the capital costs
would outweigh any benefit, but decided to run the calcs just to be
fair.

I was *sure* I'd posted similar calcs on sci.physics or sci.chem a few
years ago, but can't find them. So, I re-derived them.

Let's say we have a gym with 100 pieces of equipment, with generators
on each of them. And let's also say the gym is open 24 hours a day,
fully packed at all times.

Let's say each person exercises at a rate of 100 W (pretty hard work),
or 0.1 kW.

Let's say electricity costs $0.10/kW per hour. (More in the bay area,
less here in wintertime...)

So, each person generates $0.10/kW/hr x 0.1 kW, or one cent per hour.
(Much less than minimum wage, I might add.)

That's 24 cents/day/piece of equipment.

$0.24/day x 100 pieces of equipment = $24/day, or $8,760/year in
electricity back to the grid.

Now for the equipment costs. Let's say that each generator thingie
costs $100, including installation labor costs. $100 x 100 pieces of
equipment = $10,000.

Breakeven time is just over a year.


Key assumptions:
- gym is fully packed at all times. Not gonna happen.

- each generator thingie, plus grid-intertie-converter, breaks down to
$100/piece of exercise equipment. That's awfully generous. Probably
more like $1,000/piece of equipment is closer to the mark...

- 100% credit from the electric company for electricity. Probably in
Minnesota, but not here...


Any thoughts, folks?

Michael (I'm *not* an electrical engineer, by the way)

 

[Paul Mathews]

I had a conversation with a co-worker about harnessing energy from
folks dancing on a dance club, and from folks walking in a mall during
the shopping season. I was skeptical, thinking the capital costs
would outweigh any benefit, but decided to run the calcs just to be
fair.

I was *sure* I'd posted similar calcs on sci.physics or sci.chem a few
years ago, but can't find them. So, I re-derived them.

Let's say we have a gym with 100 pieces of equipment, with generators
on each of them. And let's also say the gym is open 24 hours a day,
fully packed at all times.

Let's say each person exercises at a rate of 100 W (pretty hard work),
or 0.1 kW.

Let's say electricity costs $0.10/kW per hour. (More in the bay area,
less here in wintertime...)

So, each person generates $0.10/kW/hr x 0.1 kW, or one cent per hour.
(Much less than minimum wage, I might add.)

That's 24 cents/day/piece of equipment.

$0.24/day x 100 pieces of equipment = $24/day, or $8,760/year in
electricity back to the grid.

Now for the equipment costs. Let's say that each generator thingie
costs $100, including installation labor costs. $100 x 100 pieces of
equipment = $10,000.

Breakeven time is just over a year.

Key assumptions:
- gym is fully packed at all times. Not gonna happen.

- each generator thingie, plus grid-intertie-converter, breaks down to
$100/piece of exercise equipment. That's awfully generous. Probably
more like $1,000/piece of equipment is closer to the mark...

- 100% credit from the electric company for electricity. Probably in
Minnesota, but not here...

Any thoughts, folks?

Michael (I'm *not* an electrical engineer, by the way)

1. Credit for power put into the grid is much higher than cost of
power taken out of the grid in many states. For example, in WA, you
get paid as much as $.51/kW-hr to add solar or wind energy to the
grid.

2. Many exercising machines convert effort more or less directly to
heat. In winter, this can subtract from the heating requirements of
the building, much as waste heat from lighting fixtures does. Of
course, if taken too far, this heat can cause the cooling system to
kick in, even in winter. In summer, the heat from exercising generally
adds to the cooling load.

Paul Mathews

 

[[email protected]]

1. Credit for power put into the grid is much higher than cost of
power taken out of the grid in many states. For example, in WA, you
get paid as much as $.51/kW-hr to add solar or wind energy to the
grid.

Wow, I'm really living in the wrong state, then! Here in CA, you're
lucky to get a fraction of the rate they charge you...

2. Many exercising machines convert effort more or less directly to
heat. In winter, this can subtract from the heating requirements of
the building, much as waste heat from lighting fixtures does. Of
course, if taken too far, this heat can cause the cooling system to
kick in, even in winter. In summer, the heat from exercising generally
adds to the cooling load.

Excellent point.

Paul Mathews- Hide quoted text -

- Show quoted text -

Ah, here's a link to the dance club generator:

http://www.washingtonpost.com/wp-dyn/content/article/2006/08/03/AR2006080301454_pf.html

SUSTAINABLE NIGHTCLUB

Energy can be harvested from just about anywhere: rivers, the sun,
wind . . . and hyperactive club kids. The latter is the rationale
behind Club Double Dee, which dubs itself the world's first
sustainable dance club.

Scheduled to open in Rotterdam, the Netherlands, the club is a
cooperative project between Enviu, an international organization
promoting sustainable entrepreneurship; Doll Lab, a Dutch architecture
firm; and Off Corso, a local dance club. Not only is Double Dee
considering serving organic beer and using a rainwater collection
system for toilets, but it may actually be powered by dancing: Springs
beneath the floor would capture motion energy to be converted into
electricity. Enviu is remaining tight-lipped about the specifics of
the project until its public presentation on Oct. 7, an event that the
organization's Web site, http://www.enviu.org/ , touts as "the
beginning of a new era; an era in which sustainability will be hip and
trendy."

 

[Brad]

Wow, I'm really living in the wrong state, then! Here in CA, you're
lucky to get a fraction of the rate they charge you...




Excellent point.





Ah, here's a link to the dance club generator:

http://www.washingtonpost.com/wp-dyn/content/article/2006/08/03/AR200...

SUSTAINABLE NIGHTCLUB

Energy can be harvested from just about anywhere: rivers, the sun,
wind . . . and hyperactive club kids. The latter is the rationale
behind Club Double Dee, which dubs itself the world's first
sustainable dance club.

Scheduled to open in Rotterdam, the Netherlands, the club is a
cooperative project between Enviu, an international organization
promoting sustainable entrepreneurship; Doll Lab, a Dutch architecture
firm; and Off Corso, a local dance club. Not only is Double Dee
considering serving organic beer and using a rainwater collection
system for toilets, but it may actually be powered by dancing: Springs
beneath the floor would capture motion energy to be converted into
electricity. Enviu is remaining tight-lipped about the specifics of
the project until its public presentation on Oct. 7, an event that the
organization's Web site,http://www.enviu.org/, touts as "the
beginning of a new era; an era in which sustainability will be hip and
trendy."- Hide quoted text -

- Show quoted text -

You failed to consider the conversion efficiency of the people doing
the work... Currently the US Government is looking into harvesting
energy from soldiers as they walk around. They are looking at a
variety of techniques, but all have fairly low conversion
efficiencies. You might have some luck, but I'm not holding my
breath.

Brad

 

[[email protected]]

You failed to consider the conversion efficiency of the people doing
the work... Currently the US Government is looking into harvesting
energy from soldiers as they walk around. They are looking at a
variety of techniques, but all have fairly low conversion
efficiencies. You might have some luck, but I'm not holding my
breath.

Brad- Hide quoted text -

- Show quoted text -

Yep, conversion efficiencies all around are likely to be low. Then
again, some folks might be able to put out 200W continuously.

I did the math intending to prove that this was a complete waste of
time, but my results do not conclusively prove that... although, I do
not intend to open a gym of any sort anytime soon.

Michael

 

[Rich Grise]

Ah, here's a link to the dance club generator:

http://www.washingtonpost.com/wp-dyn/content/article/2006/08/03/AR2006080301454_pf.html

SUSTAINABLE NIGHTCLUB

Energy can be harvested from just about anywhere: rivers, the sun,
wind . . . and hyperactive club kids. The latter is the rationale
behind Club Double Dee, which dubs itself the world's first
sustainable dance club.

Scheduled to open in Rotterdam, the Netherlands, the club is a
cooperative project between Enviu, an international organization
promoting sustainable entrepreneurship; Doll Lab, a Dutch architecture
firm; and Off Corso, a local dance club. Not only is Double Dee
considering serving organic beer and using a rainwater collection
system for toilets, but it may actually be powered by dancing: Springs
beneath the floor would capture motion energy to be converted into
electricity. Enviu is remaining tight-lipped about the specifics of
the project until its public presentation on Oct. 7, an event that the
organization's Web site, http://www.enviu.org/ , touts as "the
beginning of a new era; an era in which sustainability will be hip and
trendy."

So, do they just surround the dance floor with induction coils and
strap large supermagnets to the dancing kiddies? ;-)

Cheers!
Rich

 

[Rich Grise]

Yep, conversion efficiencies all around are likely to be low. Then
again, some folks might be able to put out 200W continuously.

I did the math intending to prove that this was a complete waste of
time, but my results do not conclusively prove that... although, I do
not intend to open a gym of any sort anytime soon.

Just strap TVs to exercycles, and sell them to everyone. It'll
save energy, and help alleviate the obesity epidemic. ;-)

And, of course, if the user turns off the TV and, say, reads a
book while still pedaling, it can feed back to the grid for
credits. That would encourage reading instead of TV. ;-D

Cheers!
Rich

 

[Spehro Pefhany]

Just strap TVs to exercycles, and sell them to everyone. It'll
save energy, and help alleviate the obesity epidemic. ;-)

And, of course, if the user turns off the TV and, say, reads a
book while still pedaling, it can feed back to the grid for
credits. That would encourage reading instead of TV. ;-D

Cheers!
Rich

High gas prices help too, according to The Independent:

http://news.independent.co.uk/world/americas/article2956424.ece




Best regards,
Spehro Pefhany

 

[David L. Jones]

I had a conversation with a co-worker about harnessing energy from
folks dancing on a dance club, and from folks walking in a mall during
the shopping season. I was skeptical, thinking the capital costs
would outweigh any benefit, but decided to run the calcs just to be
fair.

I was *sure* I'd posted similar calcs on sci.physics or sci.chem a few
years ago, but can't find them. So, I re-derived them.

Let's say we have a gym with 100 pieces of equipment, with generators
on each of them. And let's also say the gym is open 24 hours a day,
fully packed at all times.

Let's say each person exercises at a rate of 100 W (pretty hard work),
or 0.1 kW.

Let's say electricity costs $0.10/kW per hour. (More in the bay area,
less here in wintertime...)

So, each person generates $0.10/kW/hr x 0.1 kW, or one cent per hour.
(Much less than minimum wage, I might add.)

That's 24 cents/day/piece of equipment.

$0.24/day x 100 pieces of equipment = $24/day, or $8,760/year in
electricity back to the grid.

Now for the equipment costs. Let's say that each generator thingie
costs $100, including installation labor costs. $100 x 100 pieces of
equipment = $10,000.

Breakeven time is just over a year.

Key assumptions:
- gym is fully packed at all times. Not gonna happen.

- each generator thingie, plus grid-intertie-converter, breaks down to
$100/piece of exercise equipment. That's awfully generous. Probably
more like $1,000/piece of equipment is closer to the mark...

- 100% credit from the electric company for electricity. Probably in
Minnesota, but not here...

Any thoughts, folks?

Michael (I'm *not* an electrical engineer, by the way)

If you frequent gyms as I do you'll know that probably around 90% of
the people on the equipment like treadmills, bikes and rowers are
complete slackers. They don't work hard, and most come off barely
having raised a sweat.

Also, cables are a trip hazard, so lots of bikes and rowers are self
powered, only switching on when you start rowing. Can't feed those one
back to the grid unless you have an expensive facility retrofit.

Dave.

 

[John Bachman]

If you frequent gyms as I do you'll know that probably around 90% of
the people on the equipment like treadmills, bikes and rowers are
complete slackers. They don't work hard, and most come off barely
having raised a sweat.

Also, cables are a trip hazard, so lots of bikes and rowers are self
powered, only switching on when you start rowing. Can't feed those one
back to the grid unless you have an expensive facility retrofit.

How expensive? Most of the gym equipment I see already has a
generator of some sort installed - to operate the equipment
screen/control system. There is likely excess capacity already
built-in, even for the slacker-user.

All that is needed is some cabling and an inverter to feed back to the
grid or power the gym lights, etc.

It might be economically feasable after all.

John

 

[David L. Jones]

<snipped a bunch of original posting>





How expensive? Most of the gym equipment I see already has a
generator of some sort installed - to operate the equipment
screen/control system. There is likely excess capacity already
built-in, even for the slacker-user.

The "slacker" user would barely generate enough power to turn the
machine on and power the flashy LED display panel. There is a huge
difference between the potential power output a "slacker" would
generate compared with a super freak going at full speed.

All that is needed is some cabling and an inverter to feed back to the
grid or power the gym lights, etc.

Yes, and that's my point. That cabling might be expensive to install
because you can't just lay it on the floor because it's an OH&S trip
hazard. You might have to cut channels into the concrete floor or
whatever to conceal the cabling. I have no idea how much that costs,
but I'm sure it ain't trivial. That's how it is at many gyms I've been
too, and that is why a lot of the machines are self powered, no need
for the gym to install a costly power outlet for each machine.

Dave.

 

[ehsjr]

I had a conversation with a co-worker about harnessing energy from
folks dancing on a dance club, and from folks walking in a mall during
the shopping season. I was skeptical, thinking the capital costs
would outweigh any benefit, but decided to run the calcs just to be
fair.

I was *sure* I'd posted similar calcs on sci.physics or sci.chem a few
years ago, but can't find them. So, I re-derived them.

Let's say we have a gym with 100 pieces of equipment, with generators
on each of them. And let's also say the gym is open 24 hours a day,
fully packed at all times.

Let's say each person exercises at a rate of 100 W (pretty hard work),
or 0.1 kW.

Let's say electricity costs $0.10/kW per hour. (More in the bay area,
less here in wintertime...)

So, each person generates $0.10/kW/hr x 0.1 kW, or one cent per hour.
(Much less than minimum wage, I might add.)

That's 24 cents/day/piece of equipment.

$0.24/day x 100 pieces of equipment = $24/day, or $8,760/year in
electricity back to the grid.

Now for the equipment costs. Let's say that each generator thingie
costs $100, including installation labor costs. $100 x 100 pieces of
equipment = $10,000.

Breakeven time is just over a year.


Key assumptions:
- gym is fully packed at all times. Not gonna happen.

- each generator thingie, plus grid-intertie-converter, breaks down to
$100/piece of exercise equipment. That's awfully generous. Probably
more like $1,000/piece of equipment is closer to the mark...

- 100% credit from the electric company for electricity. Probably in
Minnesota, but not here...


Any thoughts, folks?

Michael (I'm *not* an electrical engineer, by the way)

In a typical gym you wouldn't recover the energy needed
to light the place, let alone sell power back to the grid.

So you have to play the "what-if" game, where you can
make (unrealistic) assumptions: highly efficient generators,
100% equipment usage, lowered requirements for lighting,
heat, ventillation, etc, high output power from each user
and so forth.

Of course, if you could somehow harvest the energy expended
by the free-energy crowd ...

Ed

 

[[email protected]]

In a typical gym you wouldn't recover the energy needed
to light the place, let alone sell power back to the grid.

Yep. 10 kW *maximum*, assuming 100 pieces of equipment. That already
is a lot. *Can* one pack more than 100 pieces of exercise equipment
into a gym?

24 Hour Fitness is downright empty at times... not always fully
packed, as my optimistic calcs assumed. If only 10% occupied, 1kW...
can that power the fluorescent lights...? It definitely won't keep
the indoor pool heated...

Then it just boils down to the economics of reduced electricity
purchases - never mind the grid intertie. Hmm... replace the
inverter with a shelf of deep cycle batteries to store energy from the
peak crowds, and just use that energy to heat the pool...???

M

 

[John O'Flaherty]

Wow, I'm really living in the wrong state, then! Here in CA, you're
lucky to get a fraction of the rate they charge you...




Excellent point.




Ah, here's a link to the dance club generator:

http://www.washingtonpost.com/wp-dyn/content/article/2006/08/03/AR2006080301454_pf.html

SUSTAINABLE NIGHTCLUB

Energy can be harvested from just about anywhere: rivers, the sun,
wind . . . and hyperactive club kids. The latter is the rationale
behind Club Double Dee, which dubs itself the world's first
sustainable dance club.

Scheduled to open in Rotterdam, the Netherlands, the club is a
cooperative project between Enviu, an international organization
promoting sustainable entrepreneurship; Doll Lab, a Dutch architecture
firm; and Off Corso, a local dance club. Not only is Double Dee
considering serving organic beer and using a rainwater collection
system for toilets, but it may actually be powered by dancing: Springs
beneath the floor would capture motion energy to be converted into
electricity. Enviu is remaining tight-lipped about the specifics of
the project until its public presentation on Oct. 7, an event that the
organization's Web site, http://www.enviu.org/ , touts as "the
beginning of a new era; an era in which sustainability will be hip and
trendy."

If springs beneath the floor capture energy from dancers, it will be
harder to dance. (Compare to one of those exercise machines with
dampers hooked to foot pedals - your going down of your own weight,
but your muscles are still applying a force through a distance,
costing energy.) So everyone will go home early, giving further
savings in lighting costs.

 

[ehsjr]

Yep. 10 kW *maximum*, assuming 100 pieces of equipment. That already
is a lot. *Can* one pack more than 100 pieces of exercise equipment
into a gym?

24 Hour Fitness is downright empty at times... not always fully
packed, as my optimistic calcs assumed. If only 10% occupied, 1kW...
can that power the fluorescent lights...? It definitely won't keep
the indoor pool heated...

It's worse - *far* worse - than that. In a typical gym, most of
the equipment is idle. On top of that, most of the exercisers
generate power intermittently rather than continuously while they
are exercising, with a lot of idle time between exercise sets.

The energy the human puts into some repetitive motion machines
must be "given back" to move the mechanisms back to the initial
condition. If it were all converted from kinetic to electrical, the
machine would not return to the initial condition for the next cycle.
Repetitive motion (push and relax) machines would yield a very low
efficiency.

Even if on a stationary bicycle type generator where power is
provided 100% of the time, a typical human can produce and maintain
about 75 watts, not 100, according to:
http://www.humboldt.edu/~ccat/pedalpower/hec/hpeg/index.html

So to produce and maintain 1KW, you would need 13 people producing
a bit above average on continuous effort machines, like a bike,
which is not found in the typical gym. But say it was.
If that's 10% of the equipment, it implies 117 other machines,
all of which occupy space, and all of that space needs to be
lighted. So, since we're into "what-if" territory assuming
13 bikes producing 75 watts each, how many square feet will all
the (130) machines occupy, and how many square feet can 12 4 foot
(80 watt, two tube) watt fluorescant fixtures illuminate, meeting
commercial building code requirements? I'm not going to do the
math, as I don't know how many square feet each machine needs
nor what commercial code requires - but I doubt that that the
fixtures can each provide enough illumination for 11 machines
per fixture. And then there is the requirment for emergency
lighting, lighting in the showers, bathrooms, reception area,
battery charging (so you can turn the lights on when you
enter the room and no one is generating at the moment, or so
you can keep the lights on when the last person stops exercising)
etc.

Ed

 

[Rich Grise]

If you frequent gyms as I do you'll know that probably around 90% of
the people on the equipment like treadmills, bikes and rowers are
complete slackers. They don't work hard, and most come off barely
having raised a sweat.

I've had occasion to ride a bus past one of those exercise joints,
and I wonder, do these people drive to this place to pay to walk on
the treadmill? Why didn't they just walk to the gym, and they wouldn't
have to use the treadmill? And the other question I'm always impelled
to ask - isn't life itself enough of a treadmill already? ;-)

Cheers!
Rich

 

[Rene Tschaggelar]

I had a conversation with a co-worker about harnessing energy from
folks dancing on a dance club, and from folks walking in a mall during
the shopping season. I was skeptical, thinking the capital costs
would outweigh any benefit, but decided to run the calcs just to be
fair.

I was *sure* I'd posted similar calcs on sci.physics or sci.chem a few
years ago, but can't find them. So, I re-derived them.

Let's say we have a gym with 100 pieces of equipment, with generators
on each of them. And let's also say the gym is open 24 hours a day,
fully packed at all times.

Let's say each person exercises at a rate of 100 W (pretty hard work),
or 0.1 kW.

Wrong to start with. 100W is our standby dissipation. Driving a
generator with 300W continous is doable, 500W continous will be hard.

 

[David L. Jones]

I've had occasion to ride a bus past one of those exercise joints,
and I wonder, do these people drive to this place to pay to walk on
the treadmill? Why didn't they just walk to the gym, and they wouldn't
have to use the treadmill? And the other question I'm always impelled
to ask - isn't life itself enough of a treadmill already? ;-)

It's a social thing, they spend half their time chatting or watching
the big screen TV's.

I'm the only one who rides a bike to my gym.

Dave.

 

[ehsjr]

Wrong to start with. 100W is our standby dissipation. Driving a
generator with 300W continous is doable, 500W continous will be hard.

Accordding to this link, 75 watts is sustainable on average:
http://www.humboldt.edu/~ccat/pedalpower/hec/hpeg/index.html

Where did you get yoyr 300 watt figure?

Ed

 

[[email protected]]

Accordding to this link, 75 watts is sustainable on average:http://www.humboldt.edu/~ccat/pedalpower/hec/hpeg/index.html

Where did you get yoyr 300 watt figure?

Ed

Maybe he's a Tour de France rider?

I also didn't specify whether my 100W was power input or power
output. If it's power output, the rider will have to ride harder due
to inefficiencies in the power conversion, of course... 200W? what's
a typical small generator efficiency? 50%? 90%?

Michael