This smells like some attempt at getting money out of bloated aid agencies.

A car battery and an el-cheapo solar panel can be had for the same price (or less - used batteries that may not hold enough charge might still be suitable to power some lights can be obtained for free) and has the advantage of being a simple system, understandable by everyone, repairable in the field with easy to obtain parts and way more rugged & reliable than what seems like a plastic, proprietary contraption with intricate moving parts and electronics.

Given the price point these are selling at, the target market of “people without reliable electricity” seems a bit off. Shouldn’t this the MSRP be $10-20? It seems more like it’s marketed as a novelty to rich westerners…
I really like an idea of gravity-based light, reminds me of a weight-driven wall clock we had as a kid. So it was somewhat sad to read that GravityLight has been discontinued.

This page has a nice, technical explanation: https://www.engineeringforchange.org/news/gravitylight-nowli... In short, the cellphones got popular, but the gravity mechanism was only producing ~0.1 watt of electricity, which is not nearly enough to charge them.

This is a good idea, but has been overtaken by solar and batteries precipitous price declines.

Kerosene lighting is both expensive and unhealthy and inflexible compared with solar/battery/LED.

One of the few things it wins on (for now at least) is up front cost, but there's various finance models that enable the future savings to be used to advance the upfront costs.


The other thing about kerosene is that it works for decades if not more with only occasional user serviceable maintenence. It can be dropped in mud, banged up, etc, and still be repaired most of the time without lots of expertise or tools. Will something like this have even a percent of the longevity and resilience?
> In 2019 we stopped manufacturing GravityLight to focus on a new product called nowlight.
Considering the incredible low cost of LEDs, would it not make better sense to have solar / wind installation, at a village level, to distribute energy for local needs?

This seems a lot of waste (both in effort and in materials)/

It'd be really cool if instead of having to pull the cord for a long time you could just detach a heavy weight from the bottom and reattach it on the top of the loop.
I would still think that something much simpler (and "bycicle based") together with a battery could be much more useful in places where there is no mains and for emergencies.

Something loosely like :


It seems like 60-80 W are sustainable for a longish period of time, so say half an hour that should be doable could be 40 Wh, something like 4 hours 10 W or 8 hour for a 5W led lamp.

I always thought that (for people sitting on a couch watching TV and not moving/walking/biking enough) connecting a small TV to the generator (with a minimal cache battery) could be a good product (though I doubt anyone would ever actually buy it).

Destin from Smarter Every Day made a video on this product in 2015: https://www.youtube.com/watch?v=Jsc-pQIMxt8
This is their current product: https://deciwatt.global/nowlight
Finally, something to wind up to power those OLPC laptops!
for those wondering: a 120 kg bag, raised for 1 meter, could give you 1 W of energy for 20 minutes.
There's a reason this was replaced by NowLight. The energy density of raised weights is low. Mechanical stuff is unreliable or experience or both compared to solid state.

Someone probably was working on some kind of "Low tech is always best" assumption. But modern tech is pretty great.

Especially now that we have LTO batteries that can last 20 years.

Also, things are more recyclable there. Just have a returns program for dead batteries and people will probably do it.

I don't think that this is quite a good idea. The weight feels a little too heavy to hang on a wall consistently, and the mechanisms are a bit too intricate. I'm also not sure the string would take that much weight, and because the weight falls slowly it might be prone to being stalled. I think it's easier to have a hand-cranked lamp that recharges a battery, which is probably much cheaper and easy to use.
Decathlon (does it exist in the USA?) has some camping lights with a crank to charge the internal battery. Or use the USB socket with a phone charger. At their volume they are pretty cheap. I got one, very convenient when camping in areas with no electricity, which is the point of Gravity.
The article mentions kerosene multiple times - wouldn't it be a better option to run a generator off kerosene to produce electricity to power multiple households?
You can replicate this with Lego. Brick Experiment Channel's most recent video has one of these that runs for 5 minutes.
Update title to use "nowlight"
converting motion into electricity efficiently requires quite a few brain cycles. I believe my solution to be much superior but actually making a product is an entirely different challenge! Impressive.

A different puzzle involved would start by gathering the [world] records in amounts of weight over distance over times for repeatedly lifting from small to maximum in all the ways we do so and then make many more dimensions accounting for different levels of strength and endurance from the best trained to the worse. Involve the amounts of sleep and food and of course account for the distribution of thees human qualities.

You sort of inevitably end up looking at Eamonn Keane's doings. https://en.wikipedia.org/wiki/Eamonn_Keane_(weightlifter)

Bench press most weight in 1 hour 138,480 kg (305,300 lb) 1,280 reps with 200 lb (90 kg) and 493 reps with 100 lb (45 kg)

Walter Urban Squad lifting in 1 hour 57,717.36 kg (127,245 lb) 145 lb for the first 30 minutes then switched to 135 lb (say 127245/140 = 909x)

Kris Winther did 5,200 consecutive air squats in 4.5 hours.

There is lots and lots of horrifically poorly shaped data available.

My conclusion is that for the most efficient power from muscles you need a range of practical fitness devices.

2000 kcalories worth of food is about 2.325 kwh say 100 watt average consumption. Say 80% is lost as heat.

But the effort it takes is considerable! You better clear the schedule.

And the winner is: 50 liters of methane for 500 wh