Cargo e-bicycles for roadless villages

EarthOS Autarky Lab
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Content

1. Introduction

2. Design outline

3. Operating costs

4. Cost comparison with small ropeways

5. Cost comparison with porters

6. Running an electric bicycle rental business

1. Introduction

When discussing aerial ropeways for mountain village with my brother, we came up with another idea for how transportation can be done in areas without motorable roads: electric cargo bicycles.

This proposal is meant for villages in mountainous regions, for example in Nepal. In these areas, there are usually no bicycles because they are pretty useless: on all these steep hills, it is simpler and just as fast to walk, and driving with significant loads is just impossible. Off-the-shelf high-powered e-bikes would work, but are not affordable in these areas. Also, they have no proper options to transport cargo.

However, it turns out that similar e-bikes specialized for cargo transport could be operated as a profitable rental business and even poor people will be able to rent them. Here are some back-of-envelope calculations:

2. Design outline

We assume a typical small market town in a valley with several villages around it, each with 600 m height difference. E-bike charging stations are built in the valley and the villages, powered by photovoltaics.

The bicycles would be cargo bikes built like mountain bikes extended in length. To further improve their off-road capabilities, they could have all-wheel drive for better traction. The front wheel would use a wheel hub motor, and the back wheel a bracket mounted motor for better hill climbing abilities. Transmission to the rear wheel hub will be with a toothed rubber belt (without any lubricants!), using a gear box at the bracket for changing gears. Avoiding any open, lubricated parts this way will avoid most wear and tear. In this setup, only the front motor can be used for regenerative braking, but that is sufficient as the front brake delivers >70% of the braking power anyway.

Article.CargoBikeRental.Flickr.wittcogmbh_7360173402.1600x1063.qu80.jpg1600Ă—1063 471 KB

Longtail cargo bicycle – a similar but electric version is envisioned here.
(Source: here on Flickr, by wittco.gmbh, licenced CC-BY2.0)

There are a few bicycles that come quite close to the proposed design:

  • Portal Long-Tail. Not an electric bicycle, but the right type of cargo bicycle and already used in Nepal. The price is only ca. 320 EUR (40,000 NPR), and it could be a suitable base for an electric conversion.

  • Radwagon. Very similar to the cargo bike envisioned here, with a long frame, side boards for cargo, a 750 W motor and a 670 Wh battery. It is available for 1270 EUR (1500 USD) when not sold out. So 1000 EUR for one with a somewhat smaller battery, local fabrication and “open source components” is hopefully possible.

  • HPC 2018 SuperMundo Cargo Bike. With a 3000 W motor and a 2.7 kWh battery, this is the highest-performing electric cargo bicycle made so far. Obviously, it is not cheap: 8700 USD with in the highest-powered variant described here. There’s a video with a detailed description, and another video of the cycle in action.

    (Note, the battery capacity was deducted from 945 Wh for 35 miles range and 100 miles range but no capacity indicated for the extended battery: 945 Wh / 35 miles * 100 miles = 2700 Wh.)

3. Operating costs

Lifting a total weight of 80 kg (60 kg driver plus 20 kg bicycle) for 600 m requires 130 Wh: 80 kg * 600 m * 9.81 m/s² / 3600 s/h = 130 Wh. With an additional 60 kg load (or a passenger …) it is 229 Wh.

Assuming these 600 m height difference has an average 15% inclination, it means a road length of 4000 m. Assuming an uphill travel speed of ideally 20 km/h, it would mean a travel time of 4 km / 20 km/h = 0.2 h = 12 min. Using 229 Wh in 12 min means a power of 229 Wh / 0.2 h = 1145 W. Quite doable – that’s a 300 W “very standard” front wheel hub motor, a 700 W gearbox motor, and 145 W human assistive power.

A 550 Wh battery will be sufficient when assuming 60% depth of discharge (20-80%, as it extends LiIon battery lifetime to 1,500 cycles for a LIPO4 battery, see here) while allowing for a depreciation down to 70% of design capacity: 229 Wh * (100/60) * (100/70) = 545 Wh. Some of the energy used (let’s assume half) can be recovered by regenerative braking.

We assume 0.40 EUR/Wh for the required high-current LiIon cells (requiring a discharge time of 15 minutes, or “4C”). This price tag is very realistic, see for example the high-current (8C - 12 C) “LG HG2” cells, selling for 0.41 EUR/Wh in packs of 10 (we extracted the shipment price here). So a 550 Wh battery would cost: 550 Wh * 0.4 EUR/Wh = 220 EUR. If such a battery can be used for 1,500 cycles, it means 220 EUR / 1,500 cycles = 0.147 EUR/cycle = 18.6 NPR/cycle.

Assuming another 0.075 EUR/cycle for other spare parts and 0.075 EUR/cycle for maintenance time and rental company profits, this adds up to ca. 0.30 EUR/cycle.

4. Cost comparison with small ropeways

Let’s compare these costs to aerial ropeways by looking at the specific transportation costs. For comparability of “costs per kilometer”, we assume the load is transported uphill in a straight line of 1 km with 600 m height difference, as it would be done with a ropeway. According to the calculation above, transporting a 60 kg load for 600 m uphill would cost: 0.30 EUR / (60 kg * 1 km) = 0.35 USD / (60 kg * 1 km) = 0.00583 USD/(kgkm). This is comparable to small aerial ropeways in developing regions, as I once calculated 0.0070 USD/(kgkm) for the example of the small-scale Barpak ropeway in Nepal, using numbers from this publication.

In addition to having comparable operation costs, electric cargo bicycles have way lower setup costs (ca. 1000 USD for per bicycle), scale much better, and are more redundant: the system still works even if half of the bicycles break.

5. Cost comparison with porters

In Nepal, the Barpak ropway was about 4 times cheaper than mule transport and 5 times cheaper than a porter (according to numbers from here), so electric cargo bikes are also as much cheaper.

This assumes that everyone transports their own cargo, so worktime is not factored in as a cost – when transporting cargo for others due to large amounts of for example building materials, this would be different. In these cases, electric cargo bicycles become a tool for porters to earn more:

Before porters would earn five times more than the transportation fee of the Barpak ropeway, with kilometers counted straight uphill “as the ropeway goes”: 5 * 0.0070 USD/(kgkm) = 0.035 USD/(kgkm). Now they have to rent the electric bicycle, which lowers their earnings to 0.035 USD/(kgkm) - 0.00583 USD/(kgkm) = 0.02917 USD/(kgkm). However, they can transport load now at 20 km/h uphill instead of 3-4 km/h on foot – let’s say 4 times faster as 20 km/h will not always be possible on bad paths. This increases their daily earnings by: 4 * 0.02917 USD/(kgkm) / (5 * 0.0070 USD/(kg*km)) = 333%. Some of that saving will be forwarded to customers, but they are surely not out of business.

6. Running an electric bicycle rental business

Some practical considerations: payment would depend on the amount of energy used, to let users contribute to the battery depreciation costs. Booking and payment would be made with a phone (including smartphones via an app, but that is optionally). Like in similar systems in cities, users would get a code to open a number lock. The position of the e-bikes would be tracked by GPS, to prevent theft.

In addition, there are interesting additional ways to make business with these electric bicycles. They are basically high-powered electric motors on wheels. This allows to also rent them out with machinery for stationary processing, connected via a power-take-off (PTO) shaft like here:

  • corn shelling, with a corn sheller mounted on the back like here
  • cereals grinder
  • water pump, with required hoses also transported on the cargo bicycle
  • winnowing machine

For these stationary uses, it will often be better to operate the motor directly on solar energy, to not strain the batteries. This is possible by also transporting a mobile set of photovoltaics panels on the bicycle, so it can produce its own energy anywhere while the battery acts as a buffer.

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Another technology you might also want to examine is the banana monorail which is cheap, off-the-shelf, and quite well known in the developing world. They can function with a variety of energy sources from human power to solar-electric, though most commonly use small gasoline engines. I’ve long been intrigued by them for their potential for deployable micro-railway systems for eco-villages and even space settlements.

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Thank you for the link, it’s a very interesting technology: mature, low-tech, DIY producable, and capable of crossing any terrain. I even found this video, where banana ropeway tech was adapted to create a personal transportation system in Nepal.

I think there is a huge potential in this and other types of lightweight ropeways for both urban “developed” areas and rural mountainous areas without roads. And it seems that nobody explored it so far: the idea to create an automated logistics system that connects every house in a settlement, and settlements with each other. Imagine how cheap postal service will be when parcels arrive automatically, and what infrastructure could be shared in villages with an automatic transport system: tools, household appliances, composting etc… People could travel with it, too. Villages might become much more viable again when logistics becomes virtually free, and “jump over” the development stage of roads to the next one. It’s pretty solarpunk :smiley: (I have a detailed plan for such a system in draft state here, will share it when once I find time to tidy it up.)