donrhummy

https://online.wsj.com/public/article...html?mod=blogs

The way they describe it sounds scary (Matrix or something):

Thanks for not scaring people off of this. LOL.

Interesting thing to think about: right now, electricity generation is very inneficient/low, but there are new advancements all the time in heat-capturing, magnetic-frictionless-motion, etc that may lead to good enough efficiency in the future to make this useful. What level does everyone think it would have to get to to be useful and could we ever get there?

gerv 

I'd be looking at things like wind-up radios, solar lamps that you set up in your window or generating devices that you add to your faucets. This thing sounds like too much drudgery.

ModoVincere

Wouldn't spin bikes make better generators? I think the average person could probably generate close to 100 watts for almost an hour. Most of the spin classes I have attended had something like 20-30 bikes, that would be 2-3 kwh's generated each class, and usually there's at least 2 classes a day. Surely that could run the lights for a gym and contribute to the air conditioning usage. Especially if the lights were all high efficiency LED lighting.

donrhummy

I agree. I think they hired the wrong person for the job. His power output levels sound very low. Even conservative estimates I've heard on this forum, seem to put output at around 100 watts for an hour. Their machines are generating about 23 watts (by their estimate of 300 total watts for 13 machines). That's ridiculous.

cerewa

I think the difference is power input (maybe 100 watts) vs electricity output (23 watts). A strong cyclist can put out a few hundred watts of power, but the best small generators turn motion-energy into electricity at way below 100% efficiency. It would not surprise me if 23% efficiency is pretty normal for a generator that size.

cerewa

Perhaps he should try riding a bike for transportation, rather than to power his car's starter motor.

The Human Car

Groan

donrhummy

LMAO, that's great!

CaptainCool

Also, a bike is about the perfect machine to hook up to a generator. On a weight machine, you have to use linear motion, provide constant resistance, and deal with a lot of stops.

Roody

Efficency of a bike on the road is over 90 %, IIRC. That sure beats the 23 % they're getting here.

supcom

100 watts for an hour, assuming 100% efficiency is 1/10 of one kilowatt-hour. That's about 2 cents worth of electricity. Takes a long time to pay back the cost of the generator at that rate.

ModoVincere

I've heard of people using old alternators from junked vehicles. Tie that into a deep cycle marine battery and a power converter and you should be able to get a decent amount of electric power from 1 to 2 hours of cycling. The alternator will put out 14 V and charge the battery. A modified sine wave converter can be bought pretty cheaply.

You wont power the entire house this way, but you could probably cover your lighting needs easily.

supcom

If you generate 100 watts on the bike for 2 hours and assuming your charging system is 100% efficient, you woould generate 200 watt-hours. This will be enough to power three 60 watt bulbs for about 1 hour. Or, if you are using a single 20 watt compact flourescent bulb, you would be able to power it for 10 hours.

Now, if you are using your generator to charge a battery, then you will find that your losses are significant. In addition to the conversion loss, the charging will not be very efficient. And using a DC battery to run an inverter will result in even more losses. I would be surprised if you could get more than 100 watt-hours to the light bulb from your two hours of cycling.

If you plan to generate electricity from a stationary bike, you should generate AC power and either power something directly or feed it back into the grid.

donrhummy

I agree, that's what they should have done. It seems like the people they chose to implement this had never done it before and didn't do any research or consult with anyone before choosing the route to go.

ModoVincere

If you are going to the effort to generate your own electricity, why in heavens name would you continue using standard lighting? I would suspect most people who have an inclination to do this would switch over to higher efficiency lighting such as Compact Flourescents or even LED based lighting. Even with the losses you mentioned, an average person could easily generate and store the power needed to light a room in a house and have power left over.

Couple that with my previous posts about using spin classes to generate the power (20-30 people 2-3 x/ day) and there would be ample power for lighting in an average gym. I think the major expense would be the storage systems.

supcom

OK, let's go with that idea. The average fluorescent light tube uses 40W. The typical fluorescent light fixture has three tubes, for a total of 120W. Go into a fitness center and count up the fixtures. I'll bet you find there are many more fixtures than exercise cycles. Being generous, we can assume that one exercise cycle will power one fixture when it's in operation. But the reality is that the average user almost certainly generates less than 120W when using the machine. But, let's not quibble. So, the 20-30 cyclists will be able to power 20-30 fixtures.

The would be no reason to waste any of the energy with a storage system. The facility will surely have much more than 20-30 light fixtures so there's not going to be any extra energy. In addition, if there were, the air conditioning system, fans, computers, music, water heaters, etc. will be happy to use it.

ModoVincere

Agreed that using current flourescent tube technology is not the ideal way to go. I beleive the flourescents yeild between 50 and 60 lumens per watt. Current LED technology is closing in on that and expected to reach 80 lm/watt soon (https://en.wikipedia.org/wiki/Light-emitting_diode. Given the directional nature of LED lighting, one would need fewer lumens as well.

I still maintain that the lighting requirements could be met. It may not look exactly the same as it does now with a massive flooding from flourescent lights, but it could be made more than adequate by using higher efficiency technologies.

PDay

2.65 Giggawatts!

hotbike

https://www.scienceshareware.com/bike_gen.htm

https://www.scienceshareware.com/how-...DC-current.htm

Some links to a related article.

jeff-o

When I first saw this topic title, I thought it was in reference to Vancouver's plan to burn human waste for energy...

smilin buddha

Found this

https://www.los-gatos.ca.us/davidbu/pedgen.html

smilin buddha

This was a local guy in the paper. During the hurricanes.

cooker

Here's the problem with all of this. You need food calories to exercise, and food is grown using an excess of energy. So the energy recovered from a generator attached to gym equipment is a miniscule fraction of what is input. If people are already wasting calories working out in a gym, and this system is installed, it may make make a tiny bit of sense, because a small portion of the huge wasted energy of indoor exercise is recaptured; but to improve the world's energy use, it would be far better for people to simply walk or bike to where they're going. That way your efforts are actually being put to productive use.

marchse

Why can't we think about generating electricity for our own domestic needs..

Soma Roark

The best idea I've seen is still building a playground where kids play and create energy via the swings and etc. =) We all know how much energy kids have! As for adults, it's not wasted energy, we need to exercise for health and it's nice that we can supplement some of the energy we use. I don't think this is meant to replace but just to augment some of that energy use. Gimmick to bring people into the gym most likely.