Rooftop solar could supply the complete electricity needs of 5-35% of U.S. manufacturing sectors, explains Matthew Eckelman at Northeastern University who summarises his co-authored paper “Technical feasibility of powering U.S. manufacturing with rooftop solar PV”. At present, only 0.1% of industrial electricity demand in the U.S. is supplied by on-site sources of renewable energy. But large, unobstructed industrial rooftops and the declining costs of solar PV systems means they can proactively decarbonise rather than wait for their local grid to go green. According to the study, the target sectors include furniture, clothing, printing, fabricated metal and others. Each location will, of course, have to make its own site assessment. But the sector averages in the study should be a good guide to feasibility. In certain cases a grid connection will be needed to cover seasonal shortfalls or sell off excess power. Others can incorporate battery storage to achieve the same flexibility. Benefits include long-term cost savings and energy independence. And, as always, policy support can drive the change, says Eckelman.

A recent study conducted by researchers from Northeastern University has shed light on the potential of rooftop solar arrays in meeting the electricity demands of the US manufacturing sector. The findings of this study, published in IOP Publishing’s journal Environmental Research Letters, have far-reaching implications, offering a viable solution for manufacturing companies to achieve their renewable energy targets, reduce their carbon emissions, and promote sustainability.

Industry accounts for 38% of global energy consumption and 37% of greenhouse gas emissions. As the world focuses on meeting net zero carbon emissions targets, the number of manufacturing companies that have set renewable energy and decarbonisation goals is increasing.

On-site renewable energy

Currently just 0.1% of industrial electricity demand in the US is supplied by on-site sources of renewable energy, motivating a number of studies into the practicality of renewable energy sources in the sector. To assess the feasibility of meeting these targets through on-site electricity generation, the researchers focused their attention on rooftop solar panels. With their large, unobstructed rooftops and the declining costs associated with solar photovoltaic (PV) systems, these installations represent a compelling option for manufacturers seeking to embrace on-site clean energy sources.

Rooftop Solar for up to 35% of US manufacturing sectors

Certain manufacturing processes have particularly high electricity demands that cannot be entirely met by rooftop solar PV systems alone. Nevertheless, the analysis revealed that, on average, rooftop solar arrays could supply the complete electricity needs of 5-35% of US manufacturing sectors, depending on the season. Furthermore, every state had light manufacturing sectors that could achieve full electricity self-sufficiency through rooftop solar panels, and many states could do so consistently throughout the year.

It is worth noting that the results are based on average conditions derived from the US Department of Energy’s Manufacturing Energy Consumption Survey. While these findings provide a comprehensive overview at the state or federal level, actual energy consumption for individual facilities may deviate from the averages. Consequently, the study’s objective is not to make specific investment recommendations for individual manufacturing sites, but rather to demonstrate the technical viability of rooftop solar PV as a solution that can help US manufacturers become more sustainable and potentially energy self-sufficient.

Contemplating the future, the researchers emphasise the need for further exploration. Currently, the analysis is conducted on a net basis, assuming surplus electricity can be sold back to the grid when on-site supply exceeds demand, and electricity can be sourced from the grid during times of high demand or low supply, such as at night. To refine the assessment, the researchers propose modelling the technical feasibility of completely off-grid systems, incorporating battery storage. Such an evaluation would provide invaluable insights into the states and sectors that could potentially achieve full electricity self-sufficiency, regardless of net consumption.

Policy support

The study also emphasises the importance of policy recommendations to drive the adoption of rooftop solar PV systems within the manufacturing sector. Historically, state-level policies have significantly influenced solar investments across the country. With this in mind, the researchers hope their work will serve as a compelling argument to state policymakers. By crafting policies that simplify, expedite, and reduce the cost of installing rooftop solar panels on manufacturing sites, states can create a favourable environment for the industry to embrace renewable energy and unlock the substantial advantages associated with these clean energy solutions.

The implications of the study extend beyond individual manufacturing companies. The US manufacturing sector plays a significant role in global energy consumption and greenhouse gas emissions, making it a crucial target for decarbonisation efforts. The adoption of rooftop solar panels across the manufacturing sector has the potential to contribute significantly to reducing carbon emissions, promoting sustainability, and aligning the industry with renewable energy goals. By embracing rooftop solar PV systems, manufacturers can not only enhance their environmental credentials but also benefit from the long-term cost savings and energy independence offered by on-site renewable energy generation.

This transition would not only contribute to a cleaner and greener energy landscape but also bolster the country’s commitment to combating climate change. As the US strives to meet its renewable energy targets and decarbonise its industries, rooftop solar arrays offer a practical and scalable solution, empowering the manufacturing sector to make significant strides towards sustainability and a more environmentally friendly future.

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Matthew Eckelman is Associate Professor of Civil and Environmental Engineering at Northeastern University