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Enabling Smart Parking: Lithium Battery vs. Energy Harvesting

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A comparative study to understand the economic and environmental impact of the two solutions: lithium battery and energy harvesting in smart parking.

By: Anirban Roy
Department of Industrial Design Engineering
Delft University of Technology

Published in: Technology
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Enabling Smart Parking: Lithium Battery vs. Energy Harvesting

  1. 1. Enabling smart parking: Lithium battery vs energy harvesting A comparative study to understand the economic and environmental impact of the two solutions Anirban Roy Dept. Of Industrial Design Engineering Delft University of Technology
  2. 2. This is a case study comparing battery technology and energy harvesting to power a distributed grid of parking sensors from the economic and ecological perspective. The study is conducted at the Delft University of Technology and Nowi Energy (a technology company founded at the startup incubator program of TU Delft) has provided their product to benchmark against other solutions in the market. Nowi was specifically chosen because of their superior product charac- teristics with respect to available market competitions. IoT Outlook: A Sought After Technology Major consultancy firms are predicting an exponential growth of IoT in every sector, with use cases ranging from industrial to smart cities to agricultural applications. Predictions suggest that the number of connected devices will reach 21 billion in the next 5 years. The total market is expected to reach 1.6 trillion dollars by 2025 (7). Some of the major implementation would be in smart industries (Industry 4.0), logistics and smart infrastructure. Introduction In spite of such reports from different market research agencies predicting a wider accep- tance of IoT solutions across all industries, uptake has been conservative. One of the major reasons is the unclear Total Cost of Ownership and ROI of these systems. Main- tenance cost over a period of time plays a significant role in the TCO of IoT systems. This report focuses specifically on the smart parking use case and helps take an informed decision while deploying large scale smart parking projects. Bottleneck to Wider Acceptance of IoT Solutions IOT PLATFORMS The Gartner chart show that ‘IoT platform’ is falling into the ‘Trough of Disillusionment’
  3. 3. Parking eats up an incredible amount of space and costs cities an extraordinary amount of mon- ey. A new study (1) that looks in detail at parking in five U.S. cities: New York, Philadelphia, Se- attle, Des Moines, and Jackson, Wyoming shows that the number of car parking spots in these major cities in the US is far more than required. But people still find it difficult to quickly locate good parking spots near their place of convenience (2). “20 to 30% of motorists in inner city traffic are looking for somewhere to park, but 13 to 14% of spaces remain vacant” - Mayor, Nice, France This dichotomy comes from the changing mobility trends of the 21st century. The behavior of vehicle ownership is slowly declining and being replaced by the trend of mobility access. The young urban generation is less inclined to own a car, but rather use services like Uber and Lyft for their mobility needs. This change directly affects the parking market: the growth of car shar- ing services has transformed the parking requirement from continuous long hours to frequent short time spans, thereby creating demand for smarter parking space management. Smart Parking - Current Projects and Market outlook A recent study by GSMA (3) found that enabling smart parking in the city of San Francisco re- duced traffic volume by 8% and greenhouse gas emissions by 30%. The study also suggested an increase of $93 / month / spot in parking revenue. As a secondary benefit, implementing smart parking can enable new business models for cellular connectivity providers: “Mobile operators can discover more meaningful intelligence about a cities’ parking usage enabling a greater range of value added services.” - GSMA Urbiotica started deploying smart parking in the city of Nice in France in 2011 with the manage- ment of 120 parking spots in a pilot phase. In 2013, 4500 sensors were deployed increasing to 8.500 by the end of 2014. A study by Allied Market Research suggests that the smart parking market is poised to grow @11.2% CAGR with a projected size of $11B by 2025 (4). Changing Vehicle Parking Market Enabling Smart Parking with Parking Sensors A key component to deploy smart parking, the parking sensor is able to detect presence of cars in a spot and relay the information through NB-IoT network. This provides real time information on the availability, usage and billing of parking spaces. Like any other IoT sensor, the parking sensor is comprised of 4 basic components: Powering the Parking Sensors Available sensors in the market are powered by lithium bat- teries. But this is turning out to be a major bottleneck for long term maintenance because they need frequent battery replacement. The unclear TCO is slowing down the uptake of smart IoT solutions (5). Energy harvesting may be a viable solution to this problem
  4. 4. With the requirement of one sensor per parking spot, and more than 10 million parking spots in 5 major cities of the US alone, the number of parking sensors installed globally by 2025 is going to be huge. Powering these sensors is a challenge and the current approach of using batteries is going to be a major bottleneck for long term maintenance (5). Battery Life - Current Industry Offerings Parking sensors from different vendors advertise battery life between 3 to 8 years. However this estimate does not take into account the high variation in operating temperature from -30° C to +45° C which adversely affect battery life (6). Another factor is the number of messages sent from the sensor to the base station - generally it is kept to a few times per day in order to conserve battery life. Frequent data gathering will improve usage time and hence revenue from parking. Growing Cost of Ownership These current battery powered sensors need maintenance every few years (8) which can quickly drive up the ownership cost over a period of time. The chart below showcases a typical cumu- lative TCO over 20 years for 100 million sensors with conservative assumptions (no change in price of battery and service + embedded sensor allows multiple battery replacements). Battery Powered Solution Environmental Impact of Batteries Also, the ecological footprint of lithium ion battery is significantly higher than solar panels or other energy harvesters. The graphic below estimates the environmental impact of 10M battery powered parking sensors for the first 5 years (it is ~200 million Kg CO2 over 20 years)
  5. 5. Activity Unit Energy / transmission Energy / day (mJ) Uplink Power consumption (mW) 623 0.997 11.964 Downlink power consumption (mW) 62.5 0.1 1.2 RF unit PSM mode (microW) 10 72 864 Microcontroller run mode (mW) 1 2 24 Microcontroller low power mode (microW) 1.4 10.1 121 10 sec Handshake power (mW) 623 6230 74760 Data transfer rate (kbits / s) 250 Data packet size (bits) 400 Time required for 1 transmission (s) 0.0016 Total power required (mJ) 6315.2 75782.2 Energy Harvesting Use Case in IoT Implementing energy harvesting in distributed sensor arrays like parking sensors is practical due to their long operational life without any maintenance. This drives down the TCO and increases ROI. The production cost (at high volumes) of one unit of the entire energy harvesting system (including the power management chip, solar cells and other components) is less than $2. Solar cells have an operational lifetime of >20 years and recent strides in technology have made them more efficient in low luminous conditions (when the car is parked on top) Energy harvesting technology has improved over the past decade to reach enough maturity where it can be used to power devices with low energy requirement for very long periods of time without any manual intervention / maintenance. Nowi energy harvesting chip has ad- dressed some chronic problems often related to energy harvesting. • ~30x smaller PCB footprint compared to leading product in the market (TI) • Need for external components to set up energy harvesting brought down from ~10 to 2 • Advanced MPPT and world leading conversion efficiency of ~92% Energy Harvesting with Nowi PMIC PMIC Characteristics - Nowi vs Industry Leader (TI) Production cost of Nowi Energy harvesting system (at high volume) < $2 / unit. Solar power harvesting with Nowi PMIC for a Typical Parking Sensor A typical parking sensor with solar harvesting can provide enough energy for continuous usage with the number of up-link messages exceeding more than 12 / day (once every 2 hours). A typi- cal energy requirement table for NB-IoT operation is presented (9): A tiny solar cell (2cm2 ) with Nowi PMIC integration can provide enough pow- er (3.5mW) for continuous usage with only 6 hours of energy harvesting in a very cloudy day. The number of up-link messages can be increased based on longer energy harvesting period.
  6. 6. Battery Power vs Energy Harvesting The two methods of powering the sensors are compared on different parameters. As is evident from the infographic below, energy harvesting is significantly superior from economic as well as ecological standpoint. The price of batteries considered is based on current cost of Lithium Car- bonate, which is poised to increase in coming years owing to the higher demand for large scale EV production. The difference in the cost of ownership is significant due to required mainte- nance of battery powered sensor systems every few years. Also, environmental impact of lithium batteries is lower than fossil fuels but is several times higher than green energy like solar power or other natural energy harvesting methods. Power Component Cost The production cost of a 10400 mAh lithium ion bat- tery is $6 (mass scale produc- tion) compared to the cost of an energy harvester system which is ~$2 / unit. This ratio is skewed even more over time as batteries need re- placement every few years where as solar powered ener- gy harvesters can work more than 20 years uninterrupted. Ownership Cost Ownership cost consists of the product and the mainte- nance cost of the system. In case of energy harvesting, the maintenance cost com- prises of one time installation (plug and forget) where as battery powered sensors need maintenance every few years where the sensor is dug out to replace the battery and installed again. Environmental Impact As we move towards a sus- tainable future, the ecologi- cal footprint of every activity will be highly monitored. Using solar powered energy harvesters in 10M sensors can reduce the CO2 pro- duction by 175M Kg over 20 years. This calculation is made considering the current production efficiency of lithi- um batteries and solar cells.
  7. 7. Reference 1. https://www.citylab.com/transportation/2018/07/parking-has-eaten-american-cities/565715/ 2. https://medium.com/@goparkr/this-is-the-truth-about-why-good-parking-is-hard-to-find- scarce-6093ef4525a5 3. https://www.gsma.com/iot/wp-content/uploads/2017/09/iot_smartparking_guide3_09_17. pdf 4. https://www.alliedmarketresearch.com/smart-parking-market 5. https://www.forbes.com/sites/forbestechcouncil/2018/09/20/five-reasons-why-iot-is-not- ready-for-prime-time/#3a5e9b1c78aa 6. https://batteryuniversity.com/learn/article/discharging_at_high_and_low_temperatures 7. https://www.statista.com/statistics/976313/global-iot-market-size/ 8. https://twtg.io/product/smartcity-parkingsensor-demokit/ 9. https://www.semanticscholar.org/paper/Power-Consumption-Analysis-of-NB-IoT-and-eMTC- in-J%C3%B6rke-Falkenberg/ad6a568775d83a1a730e8d6783229bd7ea333769

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