CARBON IMPACTS OF CO-LOCATED SOLAR GREEN ROOF SYSTEMS

Abstract

Global warming stands as a critical and pressing global issue, prompting nations worldwide to seek innovative solutions to mitigate its impact. Singapore, despite facing constraints in adopting ample renewable energy sources other than solar energy, has been active in efforts to advance co-located solar green roof systems.In this study, the Cost-Benefit Analysis of the co-located solar green roof on the rooftop of Alexandra Primary School was studied. The research objectives are to (1) Identify carbon and financial costs and benefits of a co-located system; (2) Calculate and monetise the carbon cost and benefits; and (3) Calculate the financial cost and benefits. The analytical framework will encompass the utilisation of five key metrics: Benefit-Cost Ratio, Simple Payback Period, Net Present Value, Internal Rate of Return, and Carbon Payback Period. The analysis will be performed for two timeframes, one being 3 years which is the duration of the experiment in Alexandra Primary School and other timeframe including 10 years, 20 years, 30 years, and 40 years. The results of the analysis demonstrate the financial and environmental implications of the co-located solar green roof system over five distinct lifespans. The Benefit-Cost Ratio (BCR) reveals favourable outcomes, with a ratio of 2.90 over a 3-year period and significantly higher ratio of 4.80, 7.72, 8.46, and 8.75 over a 10-year, 20-year, 30-year and 40-year span respectively. The Simple Payback Period indicates that the project would break even in less than a year for all the five scenarios. In terms of Net Present Value (NPV), the findings show positive values for all timeframes, indicating significant financial gains. The Internal Rate of Return (IRR) further supports the positive financial outlook, with rates of 82% for 3-year periods and 96% for 10-year periods and 97% for the other three timeframes consisting of 20 years, 30 years, and 40 years. The high IRR is attribute to the methodology to monetise the benefits such as through carbon rates which results in it outweighing the costs. Lastly, the carbon payback period (CPBP) is exceptionally low at 0.00049 years, underscoring the system's efficiency in offsetting the carbon emissions associated with its implementation. This low CPBP is attributed to the exclusion of total carbon emissions.