Street lighting comprises of 14.8% (9,935 GJ) of total energy used by the City of Hobart, and is a major contributor to electrical and greenhouse gas usage in all cities.
The City of Hobart spends approximately $1.5 - $2 million dollars a year and would like to investigate strategies to reduce their energy costs and light pollution. There are over 5,000 street lights in the City of Hobart, where only 300 are managed by the city. The rest of the lights are managed by TasNetworks and are unmetered. This means regardless if the light is on, off, or dimmed, the council pays the full 10 hours a day.
We wanted to investigate 4 main ideas:
- Which bulbs are the most effective, and is it cost-effective to swap bulbs?
- Is it worth metering individual poles to reduce electricity costs from dimming, with and without sensors?
- Are solar poles worth the cost?
- Can we make use of IoT and wireless technologies to make our community more sustainable?
To investigate this, we looked into street light data set from the City of Hobart, as well as data on historical energy usage and foot traffic in the CBD.
We created a webapp to help City of Hobart make decisions in regards to lighting. (https://lights-out-hobart.herokuapp.com/)
1. Phase out old MV lamps
LED bulbs are twice as efficient as MV bulbs in terms of luminosity per watt. We recommend swapping high wattage MV bulbs with lower wattage LED bulbs to greatly reduce electrical cost, while maintainging similar luminosity levels. Overall, we recommend phasing into LED bulbs, which provide other benefits of life-span, ability to be dimmed, reduced light pollution and it is the most used lights in smart cities.
- We propose swapping out 400 W MV bulbs with 250 W LED bulbs on major roads and highways.
- We propose swapping out 125 W and 150 W MV bulbs with 18 W LED bulbs on minor roads in residential areas.
2. Metering, dimming and sensors are not cost effective
Dimming has the greatest potential in residential areas, where we do not require the street lights to always be on. However, dimming existing efficient 18 W LED lights has minimal electrical cost savings. Accounting for the expensive upfront meter box installation costs, we do not recommend installing individual metering or sensors for each light pole.
3. Adapting to solar
We wanted to investigate the benefit of installing solar poles, as a permanent electrical solution by weighing up the benefits and costs.
The main advantage of solar poles is that they are a permanent electrical solution. As solar is a renewable energy source, solar poles take street lights off the grid permanently, which means permanent electricity savings from usage per kilowatt hour as well as network charges. This also means the lights are invulnerable to electricity outages, which provides added safety to the city. Solar poles also have an average lifespan of 20 years and have low maintenance costs associated with it. Some solar poles also have a sensor option available, which can reduce light pollution in areas that are deserted at night.
The major downside is that solar poles have an expensive upfront cost. Using the given inputs provided by the City of Hobart, we have done a cost analysis and found that the average payback period for street lights with inefficient bulbs is around 13 years. This is less than the average lifespan and indicates the long term payoff by switching to solar poles. Solar energy can also be inconsistent as it is reliant on weather factors such as UV index, cloud coverage and daylight hours, however we have seen solar poles with batteries that last 3 days without charging.
We recommend a 4 phase solar pole rollout targeted at major foot traffic areas to maximise the greatest social benefit and attract people towards the city centre. We also made sure each phase was within the City of Hobart's annual street light budget, making this a realistic plan.
4. Embracing a smart future
We know cities are constantly on the lookout for smart solutions to enhance city vibrancy and promote local businesses by attracting local and overseas tourists. With this in mind, we propose building on the sustainable solar poles and adding in street friendly features such as a solar charging station for small devices.
We also believe we can harness the power of IoT by connecting each solar pole to a cloud. Councils are able to utilise these wireless connections by feeding in inputs such as forecasted weather, UV index, cloud coverage. This allows the council to adjust the dimming to accomodate for special public events such as New Years, which may draw large crowds out into the city late at night. This flexibility provides the citizens with safe lighting, as well as meeting the council's energy and sustainability requirements.
- Emily Shen
- Alfred Zou
- Heng Wang
- Arnab Mukherjee
Dataset: City of Hobart Energy Savings Action Plan
Description of Use: Report was used to obtain a greater understanding of the City of Hobart council's future intentions to rectify the lighting issue.
Greenhouse Gas Emissions And Energy Use Annual Report 2017 - 2018
Description of Use: Report was used to understand the City of Hobart council's interest in solar poles, as well as other smart features for the city centre.
City of Hobart Energy Efficiency Tour
Description of Use: Report was utilised to provide crucial context into Hobart's street lighting problem to drive decision making. This allowed our team to think as a city council would, which drove our recommendations in a realistic, viable and sustainable manner that is forward thinking.
Hobart City Smart Cities Action Plan
Description of Use: Report allowed us to broaden the use cases of street lamps by incorporating additional features that align with the strategy and plans declared by City of Hobart for a smarter city. We were able to see the council's appetite for innovation and a smarter city.
Hobart City Strategy Report
Description of Use: Report was utilised for information to further enhance analysis of street lights and provide a more holistic picture of the City of Hobart.
Street Light costs - open data
Description of Use: Data was utilised to obtain the figures given to form budgets around the recommendation plan given. This formed the framework for our recommendations and ensured our recommendations and strategy for the City of Hobart was realistic and viable. This was tailored for the City of Hobart, however the costs and budget can easily be adapted and changed for any council in any state or country.
Street Lights - open data
Description of Use: Data was utilised to perform analysis on the street lights within the City of Hobart, using features such as the type of street lamp, wattage and coordinates. We were able to extrapolate the different use cases for each lightbulb and base our recommendations on that eg. highways would require a stronger lightbulb for driver safety.