Sunbrella: A Responsive Micro Bus Shelter

Delfina Vildosola + Anushka Samant + Kathleen Scopis + Laura Frances

Sunbrella is an autonomous micro bus shelter that tracks the sun to cast the greatest shade coverage keeping commuters in any neighborhood cool all day. At night, embedded street lights automatically turn on and when it rains, the shelter responsively changes position, too. Since Sunbrella tracks the sun, it efficiently charges via solar panels generating excess energy to power inclusive bus hailing features and bus arrival time displays. All in all, Sunbrella is a responsive, minimalist public technology that can deliver transit and environmental equity to all transit riders.

Heat Island Effect is Deadly 

Cities are often 1–7°F warmer than outlying areas because of urban heat island effect caused by cities’ built environments, geographies, and intense energy use. Heat generated from vehicle emission, in particular, exacerbates extreme temperatures, particularly in summer months. Public transit must be more accessible than ever to combat rising car ownership rates. Nearly every city in the US offers bus services, but too often it falls short with long wait times. Sunbrella aims to make waiting for the bus safer and more comfortable.  

The City of Philadelphia is a paradigmatic heat island, and rising temperatures have deadly consequences for residents.

Low-Income, Non-White Bus Commuters Experience More Heat Stress

Heat stress is not equitably felt across Philadelphia. Neighborhood-level hotspots, known as “intra-urban” heat islands, are caused by the uneven, inequitable spread of heat-absorbing landcovers such as highways and parking lots. Residents of intra-urban heat islands are more likely to experience heat-related illnesses and even death, and in Philadelphia those residents are more likely to be low-income and Black, Hispanic or Asian. Expectedly, these are also areas of high bus commute rates. As of 2022, less than 5% of Philadelphia’s nearly 13,000 bus stops feature a bus shelter, making bus commuting less than desirable on any given hot, cold, rainy, or windy day. 

Sunbrella Rollout Strategy

To determine Sunbrella’s prototype site selection, we developed the Sunbrella Equity Index based on three main criteria: heat exposure, bus demand, and streetscape considerations. Click on a map for a more detailed view.

Based on these converging factors, the Sunbrella Equity Index ranks each bus stop for a Sunbrella rollout strategy in Philadelphia.

Inclusive, Responsive and Low-Cost Design

The following pilot prototype is designed for an east-west curb for up to 4-5 riders waiting for the bus at once.

Sunbrella’s sensors are powered by at least 200W of solar PV panels that charge a 12V lithium-ion battery, that powers photoresistors that track light intensity, a motor that tilts the roof panel, and an Arduino Uno as well as a LED display screen and RFID reader to provide assisted ride hailing. With the addition of wireless connectivity, such as wifi or cellular shield, the display screen could also display estimated arrival times.

Sunbrella’s structure features a number of key improvements from the City of Philadelphia’s 2021 Micro-Shelter Pilot, including: 

• Integrates a responsive design to optimize shade or rain coverage as well as solar power generation
• Raises the height of the seat from 18” to 36” and chages the seat’s shape so wheelchairs, strollers, or grocery carriages can benefit from the Sunbrella’s protection
• Offers assistance bus hailing where a rider can tap their bus card or app to turn on a light that alerts the bus driver 
• Can display readily available real-time bus arrival data
• Casts street light all night rather than only when motion-activated to enhance safety, value to the community at large, and accessibility

For stops with higher ridership and/or a North-South orientation, the Sunbrella’s modular design can be configured to best serve local commuters. 

Prototype Demonstration

Next Steps

Sunbrella’s customization options are inspired by the City of Philadelphia’s transit modernization plans that integrate neighborhood-specific artwork. In terms of funding, in order to avoid expensive, large display screens for advertisers, Sunbrella is well-suited for sponsor branding.

References

Heat Island Effect: https://www.epa.gov/heatislands/learn-about-heat-islands 

Car-Rich Households are Growing: https://www.bloomberg.com/news/articles/2019-01-07/despite-uber-and-lyft-urban-car-ownership-is-growing 

Intra-Urban Heat Islands: https://www.epa.gov/heatislands/heat-islands-and-equity#:~:text=Residents%20of%20intra%2Durban%20heat,trends%20and%20consequences%2C%20and%20solutions. 

City of Philadelphia Micro-Shelter Pilot: https://www.phila.gov/media/20210827091725/Micro-bus-shelter-submission.pdf 

Technical Tutorial

In the following tutorial, the prototype is built on two modules, or Arduino boards. *All parts indicated with an asterisk were included in the ELEGOO UNO Project Super Starter Kit

Solar Tracker & Motor Module Parts List:

• Arduino UNO R3 Controller Board *
• Elegoo Prototype expansion module (shield and mini breadboard) *
• Servo (SG90)*
• Solar panel (6V) 
• Battery charge controller  
• XL6009 DC-DC Boost Converter Module 
• Rechargeable batteries and dock
• Photoresistors (light dependent resistor – LDR) – 2 pieces *
• Water Detection Sensor with Digital Output
• WS2812B Individually Addressable LEDs 
• Various resistors *
• Breadboard jumper wires *
• Female-to-male Dupont wires *

RFID & LCD Display Module Parts List:

• Arduino UNO R3 Controller Board *
• LCD 1602 Module (with pin header) *
• RC522 RFID
• Elegoo Prototype expansion module (shield and mini breadboard) *
• Various resistors *
• Breadboard jumper wires *
• Female-to-male Dupont wires *
• Blue LED *

Wiring Diagrams

1. Solar Tracker & Motor Diagram*
2. RFID & LCD Display*
3. Solar Panel & Rechargeable Battery

*Prototype shield is connected to Arduino Uno board.

Code

Solar Tracker & Motor Module Code:

RFID & LCD Display Module Code: