Does renewable mean clean?
South Africa is joining the renewable-energy bandwagon with solar and wind technologies being added into the energy mix. We take a look at whether these sources are truly pollution free
The South African Department of Energy states that the country has a high level of renewable energy potential. Presently, there is a target in place of 10 000 GWh of renewable energy. “The minister has determined that 3 725 MW needs to be generated from renewable energy sources to ensure the continued uninterrupted supply of electricity,” the parastatal points out.
“This 3 725 MW is broadly in accordance with the capacity allocated to renewable energy generation in the Integrated Resource Plan (IRP) 2010 to 2030.” The Department also developed an Independent Power Producer Procurement Programme “to contribute towards the target of
3 725 MW and towards socio-economic and environmentally sustainable growth, and to start and stimulate the renewable industry in South Africa”.
Quartz Africa, a digital news outlet, adds that, by the end of June 2015, about five percent of South Africa’s electricity requirements were being provided by renewables (excluding hydro), of which one third is being supplied by solar. “By 2030, the plan is to have 21 percent of the total energy capacity being derived from renewables.”
How clean are these alternative energy sources? The Journalist’s Resource, named one of the best reference websites by the American Library Association, answers this question in its piece: Lifecycle greenhouse gas emissions from solar and wind energy: A critical meta-survey.
“A key question, with respect to renewable energy growth, surrounds the greenhouse-gas emissions associated with specific technologies. While renewable power sources are, themselves, carbon-free _ it’s just sunlight, wind and water, after all _ the components and facilities have to be manufactured, built and maintained. At the end of their lives, plants must be retired or replaced and their components disposed of or recycled.”
The reference website highlights a 2008 study, published in the international peer-reviewed journal Energy Policy, which examined nuclear power from this perspective. “It found that the mean value of CO2 emissions, over a reactor’s lifetime, was 66 g per kWh of electricity _ less than the best fossil fuel (natural gas), but more than the most carbon-intensive renewable (biomass).”
It adds that another research review and meta-analysis was published in Energy Policy during 2014. The piece: Assessing the lifecycle greenhouse gas emissions from solar PV and wind energy: A critical meta-survey, tackles the same question for renewables.
The authors were Daniel Nugent and Benjamin Sovacool, of Vermont Law School. Sovacool is also at Aarhus University in Denmark and authored the 2008 nuclear-power study.
“In their research, they examined more than 153 studies on the life-cycle CO2 emissions of a range of wind and solar photovoltaic (PV) technologies,” Journalist’s Resource points out. “They selected 41 of these for deeper analysis, allowing the scholars to better understand the emissions of current technologies, as well as to pinpoint where emissions occur and under what circumstances. All the studies chosen for inclusion were peer-reviewed and more than 70 percent were published within the last five years.”
The key findings include:
• Based on the studies examined, wind energy emits an average of 34,11 g of CO2 per kWh over its lifetime, with a low estimate of 0,4 g and a high estimate of 364,8 g.
The mean value for solar PV is 49,91 g of CO2 per kWh, with a low estimate of 1 g and a high estimate of 218 g. The large ranges in the estimates were due to factors such as resource inputs, technology, location, sizing and capacity and longevity, as well as different calculation methods used by source studies.
• The sources of energy used to manufacture components can be critical: “The same manufacturing process in Germany would result in less than half of the total emissions that such a process would entail in China. This was primarily due to China’s significantly greater dependence on black coal for electricity production compared to Germany’s much greater reliance on natural gas and nuclear power.” (The same issue plays into the lifetime emissions of electric cars.)
• The “material cultivation and fabrication stage” of renewable-energy facilities was responsible for the greatest proportion of emissions _ just over 71 percent for both solar PV and wind.
Facility construction and related transportation were responsible for 24 percent of lifetime CO2 emissions of wind power and 19 percent for solar PV, while operation contributed 19,4 percent of lifetime emissions for wind farms and 13 percent for solar.
• Decommissioning or reuse was a net gain for both solar and wind, offsetting the equivalent of 19,4 percent of the lifetime emissions of a wind farm and 3,3 percent of a solar PV facility.
This is because “reclamation is not a standard practice for wind energy (the pads are often left or reused), and a majority of the steel towers, plastics, and fiberglass blades are recyclable.” These practices allow future emissions to be avoided.
• On average, larger wind turbines were found to have lower lifetime emissions per kWh than smaller ones: “Higher capacity wind turbines, both with taller hub heights and larger rotor diameters, correspond to lower greenhouse gas intensities.”
• Solar greenhouse gas intensity also fell with increasing size, despite the fact that panels are modular and should theoretically have the same efficiency at all sizes. This was possibly due to gains in transportation and logistics.
• Lifetime emissions decreased substantially as lifespan increased: Studies that assumed a 20-year turbine life resulted in an average of 40,69 g per kWh, falling to 28,53 g for 25 years and 25,33 g for 30 years. Solar followed a similar pattern, with an even sharper drop over time, from 106,25 g per kWh for five years to 17,5 g per kWh over 20 years.
The authors note: “By spotlighting the lifecycle stages and physical characteristics of these technologies, which are most responsible for emissions, improvements can be made to lower their carbon footprint.”
The Journalist’s Resource concludes: “Looking forward, they recommend that future studies should be more methodologically rigorous and that key questions, such as the impact of energy storage on lifetime emissions, be examined.”
Developing countries such as South Africa should definitely continue to join the renewable-energy bandwagon, however, if our planet is to survive.