Exploring the Biophysical Constraints and the Socio-Economic Implications of a Global Transition to Renewable Energy Systems.

能源投资回报率（EROI）是衡量社会可获得的净能源（在计算能源生产中使用的能源后）。例如，如果开采30桶石油需要1桶石油，则净EROI比率为29:1。在较高的EROI比率下，经济体有足够的可用能源来支持其社会。然而，在较低的EROI比率下，低于“阈值”可能会严重限制我们复杂社会的运作能力。传统观点认为，化石燃料的EROI值正在下降，但远高于现代可再生能源技术（RET）（~10:1），这意味着以RET为主导的能源系统转型可能会导致EROI降至社会水平阈值以下。简而言之，这句话的意思是“可能有问题，但不是现在”。然而，利兹大学最近完成的一项研究挑战了这一观点。我们发现有证据表明，化石燃料的EROI水平正在下降，但关键是远低于之前的预期。我们估计了最终能源（如电力、汽油）的价值，而不是传统的开采阶段（如石油、煤炭），发现全球化石燃料最终能源的EROI值约为5:1，并且在下降。我们的研究表明，化石燃料的EROI实际上可能低于RET，我们可能比我们想象的更接近“净能源悬崖”，在那里，经济的净能源可用性可能会急剧而严重地下降。为了评估这一点，必须考虑到向RET能源系统过渡的两个主要生物物理限制因素来分析：1)RET生产的能源成本；2) RET生产的材料成本。假设社会经济组织没有其他变化，并且在绿色增长情景下，研究发现，在高RET渗透路径中，RET基础设施的必要扩张导致能源成本增加，到本世纪中叶，全球EROI从12:1下降到3:5:1。同时，由于可再生能源的材料强度较高，对矿物资源的限制也可能限制可再生能源的部署，增加经济的材料强度，同时也限制非能源部门的材料使用（除能源外）。博士课题：考虑到RET过渡的生物物理可行性和社会经济影响的不确定性，迫切需要在这一领域进行进一步的全面研究。该博士学位将寻求将我们世界领先的研究扩展到这一领域，同时与EPSRC能源主题优先领域“整个能源系统”，“能源效率”，“能源网络”，“太阳能技术”，“风能”联系起来。因此提出了三个指导性研究问题：1。什么是全时间RET EROI值？2. 矿产资源的限制如何限制RET的部署？3. 什么是社会层面的EROI阈值和越轨的影响？

Energy return on investment (EROI) is measure of the net energy available to society (after accounting for energy used in energy production). So for example, if it takes 1 barrel of oil to extract 30 barrels, the net EROI ratio is 29:1. At high EROI ratios, economies have plenty of available energy to support their societies. However, at low EROI ratios, going below a 'threshold' value could seriously constrain the ability of our complex society to function. The conventional view is that fossil fuel EROI values are declining but are much higher (~30:1) than modern renewable energy technologies (RET's) (~10:1), meaning that an RET-led energy system transition may lead to dipping below a societal-level EROI threshold. In short, this translates as 'there may be a problem, but not just yet'.However, recent research completed at the University of Leeds challenges this current wisdom. We find evidence that the level of fossil fuel EROI is declining, but crucially is much lower than previously thought. We estimated values for final energy (e.g. electricity, petrol), as opposed to conventional extraction stage (e.g. oil, coal), finding that global fossil fuel EROI values for final energy are around 5:1 and declining. Our research suggests that fossil fuels EROI may be actually lower than RET's, and we may be nearer a 'net energy cliff' than we thought, where the availability of net energy to the economy may go into a very sharp and serious decline.To assess this, the transition to a RET energy system must be analysed with its two primary biophysical constraints in mind: 1) the energetic cost of RET production; and 2) the material cost of RET production. Assuming no other changes to socio-economic organisation, and within a Green Growth scenario, it has been found that in high RET penetration pathways the required expansion of RET infrastructure leads to increased energetic costs and a decline in global EROI from ~12:1 to ~3-5:1 by mid-century. Concurrently, given the higher material intensity of RET's, constraints on mineral resources may also limit RET deployment, increase the material intensity of the economy, whilst also limiting material use (in addition to energy) in non-energy sectors.The PhD Topic:Given the uncertainty surrounding the biophysical feasibility and socio-economic implications of a RET transition further and holistic research in this area is urgently required. This PhD will seek to extend our world-leading research into this area, whilst at the same time linking to the EPSRC Energy Theme priority areas "Whole Energy Systems", "Energy Efficiency", "Energy Networks", "Solar Technology", "Wind Power". Three guiding research questions are therefore proposed: 1. What are fully-temporal RET EROI values? 2. How do constraints on mineral resources limit RET deployment? 3. What is the societal-level EROI threshold and the impacts of transgression?