In a paper published in ‘Renewable and Sustainable Energy Reviews’ Volume 76, four Australian researchers have warned that published modelled scenarios which affirm that an electricity system based entirely on renewable-energy sources is possible are significantly underestimating the challenges involved. The researchers are BP Heard, of the University of Adelaide, BW Brook, of the University of Tasmania, TML Wigley, of both the University of Adelaide and the US National Centre for Atmospheric Research in Boulder, Colorado, and CJA Bradshaw, of Flinders University.
In the introduction to their paper (‘Burden of Proof: A comprehensive review of the feasibility of 100% renewable-electricity systems’), they note that the “recent warming of the earth’s climate is unequivocal. . . . Inexpensive and abundant energy remains crucial for economic development; the relationship between per-capita energy consumption and the United Nations Human Development Index is ‘undeniable’. But there seems little prospect of decreasing energy consumption globally this century, especially with >10% of the global population in extreme poverty.”
Thus, to decarbonise electricity generation while meeting the growing demand for power worldwide, it will be necessary to develop credible plans, based on evidence, for electricity systems that avoid using fossil fuel resources and which can be ramped up to address the energy needs of a global population that will most likely amount to nine- to ten-billion people by 2050 and perhaps more than 12-billion by 2100. “This process logically begins with displacing coal, gas and oil in electricity generation, but must eventually expand to eliminate nearly all fossil hydrocarbon[s] used in industrial and residential heat, personal and commercial transportation, and most other energy-related services.”
They point out that much of the focus on developing low-carbon energy sources has been on those classified as renewable – such as biomass, geothermal, hydroelectricity, solar, wave and wind. Nuclear power and carbon capture and storage technologies are often explicitly excluded. “These imposed choices automatically foreclose potentially essential technologies,” they argue. “[T]he burden of proof for such a consequential decision is high and lies with the proponents of such plans. If certain pathways are excluded a priori, then such exclusions should be fully justified and the alternatives proven. This is rarely the case.”
They point out that the only developed country in the world today that gets all its electricity from renewable sources is Iceland, and that is because the country benefits both from excellent geothermal and hydroelectric resources and has only a small population (about 300 000). As for European States much lauded for their investment in, and use of, renewable energy, their greenhouse-gas emissions from electricity generation are about the same as the average for the 27 European Union member States, or EU-27. (Technically, the EU still has 28 members, but the UK has formally started the process of leaving.) Thus, the figure for Denmark is 468 g CO2-e kWh-1, for Germany 365 g CO2-e kWh-1 and for the EU-27 442 g CO2-e kWh-1.
For their analysis, they examined 24 studies that predicted energy requirements at the global, regional or national levels in sufficient detail to be “potentially credible”. They were reviewed using four “novel feasibility criteria”. These criteria were: “(1) consistency with mainstream energy-demand forecasts; (2) simulating supply to meet demand reliably at hourly, half-hourly, and five-minute timescales, with resilience to extreme climate events; (3) identifying necessary transmission and distribution requirements; and (4) maintaining the provision of essential ancillary services”
.Of the studies reviewed, one-third (8) contained no type of system simulation. Half (12) were dependent on unrealistic energy demand forecasts. One-sixth of the studies (4), all focused on the regional level, did deal with transmission requirements, but only two dealt with ancillary-service requirements. “In addition to feasibility issues, the heavy reliance on exploitation of hydroelectricity and biomass raises concerns regarding environmental sustainability and social justice.”
“Our assessment of studies proposing 100% renewable-electricity systems reveals that, in all individual cases and across the aggregated evidence, the case for feasibility is inadequate for the formation of responsible policy directed at responding to climate change,” they conclude. “To date, efforts to assess the viability of 100% renewable systems . . . have substantially underestimated the challenge of excising fossil fuels from our energy supplies. This desire to push the 100% renewable ideal without critical evaluation has ironically delayed the identification and implementation of effective and comprehensive decarbonisation pathways. . . . Uniting the alleviation of poverty with a successful climate change response in our energy and electricity systems should be an international goal. . . . It behooves all governments and institutions to seek optimised blends of all available low-carbon technologies . . . to pursue clean, low-carbon electricity-generation systems that are scalable to the demands of ten-billion people or more.”