ZolarBoda

solar powered cargo ebike taxi

The ZolarBoda is a solar powered cargo ebike which can carry a passenger on a rear seat and luggage in a large front basket. The 160Wp solar roof allows for charging on the go and provides sun and rain protection.

Concept

Boda Bodas are two wheeler taxis in East Africa. Initially, they were mostly bicycles which are now more and more replaced by motorcycles. The latter are faster, and therefore, more profitable. But their increased speed also means an increased safety risk for the driver and passenger and they contribute to air and noise pollution.

The ZolarBoda as an solar powered electric assist ebike aims to provide a clean transportation means between the purely human and purely motor powered boda boda taxi. It is not as fast as the motorcycle but it is safer (lower speed), less expensive, allows for easy cargo transportation and provides driver, passenger and cargo with protection from sun and rain.

The ZolarBoda uses an affordable (~70 €) cargo (bakery) bike as basis. These type of cargo bikes with a large basket above the small front wheel were common in Europe in the past. They are still used in India and East Africa among others. The roof structure is made out of aluminium tubes and is the result of 6 years of protoyping.

A main challenge was to get the roof structure stable and lightweight enough while only attaching it to the front (basket) of the bicycle. Attaching the roof also at the rear of the bicycle like in early ZolarBike protoypes or the awesome solar bicycles of the sun trip for instance would not allow for any passengers on the rear seat.

Technical Details

solar module	160 Wp, 18V (exact maximum power point voltag depends on temperature), semi-flexible, ETFE front layer, 2kg, 68cm x 148cm
battery	36V, 15Ah, 540Wh, max 5A charging current, Lithium (later versions might use LiFePO4 for increased cycle lifetime and safety), USB (phone) charging port
solar charge controller	no-name (blue-black) MPPT boost solar charge controller, max 300W, adjustable output voltage 24V-72V. The other (green) affordable solar mppt boost solar charge controller for lithium batteries that I used for the ZolarBike and ZolarTrike proofed to be unsuitable for the mobile application. I had two contollers and both broke after some months – probably due to the fan breaking from vibrations during cycling. One even took out the ebike motor controller with it. Another alternative is the Gensun MPPT Lithium solar charge controller. It is lighter, more efficient (producing some power during very low light when the no-name controller already switches off, and its mppt tracking is faster (reaching max power quicker after the solar panels had been shaded) but it is also 10x more expensive (280€ vs 28€).
motor	250W front hub motor, 36V, 25 km/h max
front wheel	20″
rear wheel	26″

Rain Protection

The solar roof provides both sun and rain protection. When it is raining covers can be placed at the front, top and sides to provide additional rain protection. The roof provides a sufficient large overhang towards the front for an adequate rain protection towards the front without needing a windshield. I tried a windshield on the ZolarTrike but without a wiper visibility during rain was too poor. By having no windshield rain protection is not 100% but the view to the front stays clear.

Solar Charge Range

How many kilometers can be driven purely using solar power depends on the power requirements (amount of electric assist, hilly vs flat terrain, weight), the amount of sun available and the degree of shading due to trees and buildings. The graph below shows a rough estimation assuming a power consumption of 10 Wh/km and an average loss due to shading of 40% in Berlin, and 20% in Mombasa.

What Next

I will test the ZolarBoda protoype in Berlin for the next couple of months. Sometime in 2021 I plan to import one or two (bakery) cargo bikes from India or Kenya to build additional prototypes. They will already come with the large front basket which I had to built myself for the current protoype for which I used an old East German bicycle wich came with a too small front basket.