Giving solar the green light?

Amongst all alternate energy technologies, I find solar power to be the most relatable at a personal level – growing up in sunny Singapore, I often felt that more can be done to reduce our fossil-fuel dependency, if only we utilized our abundance of sunlight. My hopes are gradually being realized over the years, beginning with the SolarNova Programme in 2014 which aims to generate 420 GWh of electricity annually (or ~5% of Singapore’s total energy consumption) by installing solar panels on the rooftops of numerous public housing blocks, followed by the recent commencement of construction for a large-scale floating solar photovoltaic (PV) system on Tengeh Reservoir as illustrated below. With heightened domestic interest, the Solar Energy Research Institute of Singapore (SERIS) has projected that solar energy could comprise up to 4.5% of Singapore’s electricity generation mix within a decade under its accelerated scenario, which is over twice its 2.3% composition today.

Source: Public Utilities Board (PUB), 2020

While seemingly abrupt, these investments were underpinned by decades of cumulative advancement in solar technologies, which extend way beyond Singapore’s borders. In 2019, solar energy alone accounted for ~56% of global growth in renewable generation capacity, dwarfing all other alternatives combined. Perhaps more surprisingly, solar capacity growth of 20% (98GW) from 2018 was barely more than half its historic average annual growth rate of 38% between 1998 to 2015, indicating that this breakneck progress has already been ongoing for a considerably lengthy period.

Source: Creutzig et al., 2017

Rising adoption of solar energy across the globe were catalysed – at least in part – by their rapidly plummeting costs, which were primarily attributable to successful progress along learning curves and vast economies of scale for manufacturing and assembly of solar PV modules. Much of these gains were then passed onto consumers, who became increasingly receptive to solar energy as their electricity prices decreased. While the long-term financial viability of sustaining ultra-cheap power purchase agreements were initially brought into question, subsequent analysis attested for their feasibility – and even profitability – given conditions of low financing costs and strong sunlight, whether in the USA or Middle East.

Source: Apostoleris et al., 2018

Demonstrating the environmental benefits of solar energy is far more straightforward than discussing its economics – put simply, it helps prevent runaway global warming by reducing greenhouse gas (GHG) emissions, which would otherwise have resulted from burning fossil-fuels to meet the global energy demand. To be more precise in pinpointing the extent which GHG is avoided, it is necessary to conduct a life-cycle assessment (LCA) from “cradle to grave” to account for environmental impacts of manufacturing and disposal of solar PV units, rather than being captivated by its clean operational phase alone. Estimates from one such meta-study of different electricity generation systems, as depicted below, suggests that GHG emissions per unit of electricity from solar PV and thermal are typically less than one-fifth of natural gas, the cleanest fossil fuel. While solar lies amongst the most pollutive renewable energy technologies, it is still a huge improvement from the status-quo.

Source: Amponsah et al., 2014

Of course, solar energy also contains environmental costs. For starters, renewable energy suffers huge systemic disadvantages in land-use efficiency per unit of power output when compared against their fossil-fuel counterparts. With fossil-fuel power stations generating 200–11,000 We/m2, the 2–10 We/m2 by solar PV plants is only ~1% as land-efficient, hence the latter requires far more land which could have been allocated for agricultural or even conservation purposes. To address concerns over land-scarcity, solar PV can be integrated within farmland as agrivoltaic systems, without necessarily diminish reducing crop yield. Floating solar PV plants like the above-mentioned example in Singapore provide plausible alternatives, but the resultant shading and sediment re-suspension could have detrimental effects on coral and seagrass, rendering such trade-offs complicated.

With solar PV panels being utilized in huge quantities, these also act as potential environmental hazards after being retired from operation, as they contain up to 18 releasable metals which can poison their surrounding ecosystems and contaminate drinking water. To make matters worse, the prominent third-generation perovskite solar cells are heavily reliant on lead-based halides that are known for their high toxicity. Though these detrimental effects can be mostly mitigated through controlled recycling and waste-processing operations, doing so requires that adequate enforcement measures to be implemented, posing considerable challenges for jurisdictions with weaker institutional controls.

Overall, I believe the benefits of solar energy as a scalable method of avoiding GHG emissions significantly outweigh its costs. However, since existing options for mitigating its detrimental effects are limited in their effectiveness, it would be hasty to conclude that solar energy is universally beneficial. Nonetheless, I remain hopeful that technological improvements would help reduce these downsides in the years to come.