Source-linked AI summary
Response to 'Burden of proof: A comprehensive review of the feasibility of 100% renewable-electricity systems'
T. W. Brown, T. Bischof-Niemz, K. Blok, C. Breyer, H. Lund, B. V. Mathiesen
TL;DR
The paper examines whether criticism of 100% renewable-electricity studies demonstrates genuine technical infeasibility. It distinguishes feasibility from viability, reviews the challenged criteria and related modelling evidence, and concludes that renewable systems are feasible and viable while identifying separate feasibility concerns for nuclear technologies.
Problem
A prior review concluded that many 100% renewable-electricity studies do not satisfy selected technical-feasibility criteria.
Method
The paper analyses the prior review’s methodology and criteria, compares them with engineering and modelling evidence, and introduces additional feasibility criteria.
Results
100% renewable-energy scenarios are concluded to be feasible and viable, with systems meeting citizens’ energy needs at all times described as cost-competitive with fossil-fuel systems.
Takeaways & Limitations
The paper concludes that the criticized issues can be addressed at low economic cost and that only directed evolution of the current power system is required.
Takeaways & Limitations
Breeder reactors are described as technically immature, costly, unreliable, potentially unsafe, and associated with proliferation risks.
Abstract
from arXiv · showhide
A recent article 'Burden of proof: A comprehensive review of the feasibility of 100% renewable-electricity systems' claims that many studies of 100% renewable electricity systems do not demonstrate sufficient technical feasibility, according to the criteria of the article's authors (henceforth 'the authors'). Here we analyse the authors' methodology and find it problematic. The feasibility criteria chosen by the authors are important, but are also easily addressed at low economic cost, while not affecting the main conclusions of the reviewed studies and certainly not affecting their technical feasibility. A more thorough review reveals that all of the issues have already been addressed in the engineering and modelling literature. Nuclear power, which the authors have evaluated positively elsewhere, faces other, genuine feasibility problems, such as the finiteness of uranium resources and a reliance on unproven technologies in the medium- to long-term. Energy systems based on renewables, on the other hand, are not only feasible, but already economically viable and decreasing in cost every year.
1. Introduction
The response challenges a review that judged highly renewable electricity studies against selected feasibility criteria, arguing those criteria are addressable and do not overturn the studies’ conclusions.
- Critics questioned whether renewable scenarios adequately address variability, storage scalability, system costs, resource constraints, social acceptance, non-electric energy use, and deployment rates.
- The reviewed article assessed 24 regional and global studies of highly renewable electricity systems using feasibility criteria drawn from existing criticisms.
- The response argues that the authors’ criteria are technically and economically easy to address and do not affect the reviewed studies’ conclusions.
- The paper additionally introduces feasibility criteria that renewable scenarios satisfy but nuclear power does not adequately satisfy.
2. Feasibility versus viability
The paper distinguishes narrow technical feasibility from broader socio-economic viability and argues that viability, rather than feasibility alone, is the more relevant debate.
- The authors define feasibility as technical possibility with current or near-current technology, while viability includes environmental, social, and reasonable-cost constraints.
- The response argues that today’s technology provides solutions to the feasibility issues raised, making cost-effective deployment within broader constraints the more important question.
- The authors are criticized for treating requirements from cost-optimization studies as evidence of feasibility rather than viability.
- In Europe, annualized network expansion costs of 8 billion AC/a are presented as 2% of electricity spending, or 0.003 AC/kWh.
3. Feasibility Criteria
The response argues that the authors’ feasibility criteria and scoring are arbitrary or conflate technical feasibility with economic viability. It shows that renewable scenarios remain feasible through efficiency, electrification, statistical smoothing, existing technologies, and modest-cost infrastructure.
- The authors’ criteria, weighting, and scoring are described as arbitrary, with resource constraints and technological maturity identified as more consequential feasibility criteria.The response also argues that primary energy, transmission, and ancillary-services scoring is coarse and subjective.
- Demand projections: Primary energy can fall while delivered energy services remain unchanged because renewable technologies are accounted for differently from fossil-fuel systems.The response argues that meeting energy needs and reducing emissions matter more than primary energy alone.
- Demand projections: 30–60% reductions in German space-heating demand were modelled through retrofitting measures, although their socio-economic viability is not established for every measure.The response distinguishes technical feasibility from the question of whether all measures are economically and socially acceptable.
- Simulation time resolution: At large spatial scales, hourly modelling is adequate because aggregation smooths load, wind, and solar variations; 5-minute simulations do not significantly change large-scale results.An Ireland study found 5-minute simulation costs just 1% higher than hourly simulation, while the response notes that smaller areas may require finer resolution.
- Reliability and flexibility: Even worst-case dispatchable capacity for peak load would not invalidate renewable scenarios, while storage, demand response, imports, and biomass can reduce reliance on open-cycle gas turbines.The response presents this as a feasibility argument and notes that the authors’ concern about cost and complexity is instead a viability issue.
4. Other Issues
The response argues that storage technologies criticized as unproven are established, commercialized, or demonstrable at relevant scales. A cross-sectoral approach can further rely on low-cost thermal, gas, and liquid storage.
- The response rejects the claim that most storage technologies beyond pumped hydro are unproven at large scales.It contrasts that claim with evidence for established lithium-ion batteries, commercialized compressed-air storage, and megawatt-scale power-to-gas demonstrations.
- Battery storage uses established lithium-ion technology already deployed in utility-scale plants and increasingly available from second-life electric-vehicle batteries.Examples include a 100 MW South Australian plant and 700 MW of utility-scale batteries in the United States by the end of 2017.
- Compressed-air storage and electricity-to-gas technologies have been demonstrated or commercialized, including hydrogen electrolysis with possible later methanation.Hydrogen can be used in gas networks, fuel-cell vehicles, synthetic fuels, or electricity generation.
- Integrating thermal, transport, and industrial demand enables renewable systems using low-cost, well-proven thermal, gas, and liquid storage.These sectors also provide deferrable demand that helps integrate variable renewable energy.
4.2. Feasibility of biomass
The response acknowledges concerns about biomass availability and environmental impacts, while noting that newer studies assess biomass potential more carefully and restrict use to residues and waste.
- Biomass-based renewable scenarios raise concerns about fuel-crop availability, environmental damage, biodiversity loss, and competition with food crops.
- More recent studies conduct detailed biomass-potential assessments or restrict biomass use to agricultural residues and waste.
- The response treats biomass feasibility as conditional on addressing resource and environmental constraints rather than assuming unrestricted biomass deployment.
4.3. Feasibility of carbon capture
Carbon capture and negative-emissions technologies have some commercial-scale components but remain constrained by cost, technical, efficiency, regulatory, and public-acceptance challenges. CCS is reported as not cost-effective in some high-resolution system studies, while DAC may support synthetic-fuel production.
- Carbon capture components have been demonstrated commercially, but sequestration leakage, cost, pollutants, imperfect capture, efficiency, regulation, acceptance, and integration remain hurdles.
- High-resolution studies find CCS not cost-effective because of high capital costs and low utilization.
- Direct air capture may be promising for synthetic fuels because of locational flexibility and minimal water consumption.
4.4. Viability of renewable energy systems
The response argues that highly renewable energy systems can be socially viable and economically competitive, with renewable generation often at or below fossil-fuel costs and modeled system costs remaining low.
- The response concludes that highly renewable systems are feasible and economically viable across demand, variability, extreme events, grids, ancillary services, resources, and technological maturity.
- Social viability: 89% of surveyed European Union citizens considered national renewable-energy targets important, while 82% across 13 countries supported a fully renewable-powered world.
- Social viability: Public acceptance of onshore wind can increase through early community engagement, responsive planning, and local participation in project outcomes.
- Economic viability: Onshore wind, offshore wind, solar PV, hydroelectricity, and biomass are already at or below the cost range of current fossil-fuel generation on a levelized-cost basis.
- Economic viability: 52 AC/MWh is the projected average system cost for global 100% renewable electricity in 2050, down from 70 AC/MWh in 2015.The study modeled hourly operation across 145 world regions.
- Economic viability: 36 US$/MWh for PV-plus-battery and 21 US$/MWh for wind-plus-storage were median auction prices for United States systems scheduled to come online in 2023.
4.5. Viability of nuclear power
The discussion distinguishes nuclear power’s technical feasibility from its broader socio-economic viability, including cost, safety, waste, and proliferation concerns.
- Nuclear power’s socio-economic viability encompasses cost, safety, decommissioning, waste disposal, public acceptance, terrorism, and nuclear-weapons proliferation.
4.6. Other studies of 100% renewable systems
The authors’ review omitted many studies of 100% or near-100% renewable systems, spanning multiple regions and commonly using hourly simulations and transmission-grid modelling.
- Many omitted studies simulated 100% renewable systems at hourly resolution and modelled transmission grids.
- The omitted literature covered regions including the globe, North-East Asia, ASEAN, Europe, the Americas, China, and the United States.
- Subsequent studies expanded coverage to Asia, Europe, the Americas, India, Australia, Brazil, Iran, Pakistan, Saudi Arabia, Turkey, Ukraine, and islands.
4.7. Places already at or close to 100% renewables
Countries, regions, and islands already generate all or most of their electricity from renewables, including systems relying on synchronous generation, interconnection, or inverter-based technologies.
- The claim that Iceland is the only developed nation with 100% renewable electricity overlooks countries near 100% and smaller islands already at 100%.
- Paraguay generates 99% renewable electricity, Norway 97%, Uruguay 95%, Costa Rica 93%, Brazil 76%, and Canada 62%.
- Regions at or above 100% renewable electricity include parts of Germany, New Zealand, Scotland, and Denmark.
- Some systems stabilise grids through hydroelectricity, geothermal, biomass, or alternating-current connections, while Tokelau and American Samoa use solar-plus-battery systems without synchronous generation.
- German North Sea offshore collector grids operate with only inverter-based generators and consumption, transmitting power ashore through an AC-DC converter and HVDC cable.
4.8. South Australian blackout in September 2016
The response disputes attributing the September 2016 South Australian blackout to wind generation, citing the incident’s extreme circumstances and control-setting response.
- Wind turbines rode through the grid disturbances; a control setting responding to multiple faults led to the blackout after tornadoes damaged two transmission lines.
5. Conclusions
The response argues that the reviewed feasibility criteria are important but not critical, because their requirements can be met technically and at low economic cost. It concludes that 100% renewable systems are feasible, viable, cost-competitive, and require only directed evolution of existing power systems.
- The reviewed feasibility criteria can be addressed at low economic cost and do not undermine the conclusions of highly renewable scenarios.Conservative measures such as dispatchable peak capacity, grid expansion, and synchronous compensators remain technically feasible, while more cost-effective solutions are also available.
- 100% renewable energy scenarios are both feasible and viable.
- Guaranteeing affordability, reliability, and sustainability requires directed evolution rather than a reinvention of the power system.