Summary Reader Response

In the article “Go-Ahead Singapore rolls out 6-month trial of public buses with solar panels”, Kok (2021, March) discusses the “proof of concept trial” conducted by Go-Ahead Singapore from March to September 2021. The article highlighted the features and uses of ultra-thin solar panels that aim to reduce carbon emissions and fuel consumption by utilizing solar energy.

The 16mm-thick pliable panels are designed to resist shattering and weigh under 20kg which is a third of what conventional solar panels weigh. According to Kok, Leonard Lee, Go-Ahead Singapore engineering director, mentioned that the weight and size of the solar panels do not pose a problem for it to be installed on the roof of the buses due to their ultra-thin and lightweight feature. Due to the hot and humid climate in Singapore, solar panels can absorb solar energy effectively. The panels generate electric energy to charge the buses’ batteries instead of depending on their alternator. Kok mentioned that data from a trial that was conducted in Southampton in 2019 resulted in saving 1,400 liters of diesel and 3.7 tones of emissions per bus annually.

While buses equipped with solar panels are expected to do better in Singapore due to its hot and humid climate, other factors such as cloud cover, space limitations, and technological limitations may mean that solar panels will not be as effective.

One factor that impacts solar panel use is cloud cover. When clouds form during the day, a portion of the sun's energy reaches the earth and is reflected into space, preventing the planet from becoming too hot. Most of the time, the areas with the least cloud cover are the ones with the most sunshine, whereas areas with the most clouds are the ones with the least sun. According to Andrew-Speed, the average level of solar radiation in Singapore is not above a high level despite its hot and sunny climate. Radiation in Singapore is 50% higher than that in northern Europe, where solar photovoltaic plays a significant role. Yet, it is less than that in northern China and 30% - 40% less than that in North Africa, the Middle East, and Australia, where large photovoltaic arrays are being constructed, (Andrew-Speed, 2021). Furthermore, consistently high temperatures reduce the efficiency of photovoltaic cells. As a result, solar panels may not be as efficient. 

Another impactful factor is space limitations. Singapore is known as one of Asia's greenest cities. Buildings and precincts have been designed to improve wind flow and reduce heat. As a small island city-state with a land area of 71,400 hectares, Singapore faces challenges in utilizing its land efficiently and effectively to achieve high productivity (Marchant, 2021). Most of the land in Singapore is occupied by buildings, roads and protected by green spaces. According to Andrew-Speed, a total area of just under 37 sq km could be utilized for solar photovoltaic panels. Considering the lack of sun exposure caused by high-rise buildings and large areas of green space, solar-powered buses may not perform to their full potential while on the road.

Apart from the two factors mentioned, an additional factor to take into consideration is solar cell efficiency. Solar cell efficiency is a measure of the performance of converting sunlight into electricity. According to “Solar Energy At Home”, only sunlight has the specific energy that efficiently produces electricity. One way to store PV (photovoltaic) is to use a battery bank to store the power generated by the PV array. Solar grid integration is a technology that allows PV or CSP (concentrated solar power) systems to inject large amounts of solar power into existing power grids. Cell efficiency, energy storage, and grid integration are examples of technological limits. According to Andrews-Speed, the efficiency of commercial solar cells is currently between 15% and 21%. Singapore's electricity demand is highest between 9 am and 5 pm when the sun peaks, but low at night when people return home from work and turn on air conditioners and other appliances. As the use of solar energy to generate electricity during the evening hours increases nationwide, batteries and other forms of energy storage are becoming increasingly important. Energy storage also helps integrate solar energy into the power system. As the amount of solar energy produced increases, both minute and hourly fluctuations in solar energy can complicate grid stability.

Although solar panels have severe limitations, installing solar panels on buses reduces carbon emissions, fuel consumption, and cost. According to data from “GlobalPetrolPrices”, diesel price in Singapore is 2.209 SGD per litter. Kok mentioned that the trial conducted in Southampton UK in 2019 resulted in 1400 liters of diesel, which equates to saving 3092.6 SGD per bus. However, despite the cost reduction in fuel, installing solar panels on buses may result in increased cost maintenance and repair activity.

Solar-powered buses are a good start to mitigate climate change and reduce fuel consumption and cost, given that transportation is one of the sectors that contribute to the high rise in carbon emissions. However, there are still limitations that may affect the performance of these solar panels. Although Singapore has a hot a humid climate, having limited sunlight, inadequate amount of space and technical constraints prevent the solar panels from performing effectively. In addition, given the lifespan of solar panels, there is an increase in the cost of maintenance. 

References:

1. Auto, H. (2021, March 30). Go-Ahead Singapore rolls out 6-month trial of public buses with solar panels. The Straits Times. https://www.straitstimes.com/singapore/transport/first-public-buses-with-solar-panels-hit-the-road-in-six-month-trial-by-go-ahead

2. National Geographic Society. (2020, March 20). Cloud Cover. https://www.nationalgeographic.org/encyclopedia/cloud-cover/

3. Wikipedia contributors. (2022, January 29). Cloud cover. Wikipedia. https://en.wikipedia.org/wiki/Cloud_cover#:%7E:text=Cloud%20cover%20

4. Andrews-Speed, P. (2021, May 4). Commentary: Why hasn’t solar energy in Singapore taken off in a big way after so long? CNA. https://www.channelnewsasia.com/commentary/solar-energy-singapore-panels-cloudy-unpredictable-electricity-1882996

5. The Weakness Of Space Constraint In Singapore | ipl.org. (n.d.). IPL. https://www.ipl.org/essay/The-Weakness-Of-Space-Constraint-In-Singapore-PCUHUK3NFU#:%7E:text=3.,to%20obtain%20a%20high%20productivity.

6. How is Solar Energy Stored? Solar Energy Storage Information. (n.d.). Solar Energy At Home. https://www.solar-energy-at-home.com/how-is-solar-energy-stored.html

7. GlobalPetrolPrices. (2022). Singapore Diesel Prices, 14-Feb-2022

https://www.globalpetrolprices.com/Singapore/diesel_prices/