Courtesy: world-nuclear.org

Renewable Energy and Electricity

(Updated August 2021)

• There is widespread popular support for using renewable energy, particularly solar and wind energy, which provide electricity without giving rise to any carbon dioxide emissions.
• Harnessing these for electricity depends on the cost and efficiency of the technology, which is constantly improving, thus reducing costs per peak kilowatt, and per kWh at the source.
• Utilising electricity from solar and wind in a grid becomes problematical at high levels for complex but now well-demonstrated reasons. Supply does not correspond with demand.
• Back-up generating capacity is required due to the intermittent nature of solar and wind. System costs escalate with increasing proportion of variable renewables.
• Policy settings to support renewables are generally required to confer priority in grid systems and also subsidise them, and some 50 countries have these provisions.
• Utilising solar and wind-generated electricity in a stand-alone system requires corresponding battery or other storage capacity.
• The possibility of large-scale use of hydrogen in the future as a transport fuel increases the potential for both renewables directly and base-load electricity supply off-peak.Technology to utilize the forces of nature for doing work to supply human needs is as old as the first sailing ship. But attention swung away from renewable sources as the industrial revolution progressed on the basis of the concentrated energy locked up in fossil fuels. This was compounded by the increasing use of reticulated electricity based on fossil fuels and the importance of portable high-density energy sources for transport – the era of oil.As electricity demand escalated, with supply depending largely on fossil fuels plus some hydro power and then nuclear energy, concerns arose about carbon dioxide (CO₂) emissions contributing to possible global warming. Attention again turned to the huge sources of energy surging around us in nature – sun, wind, and seas in particular. There was never any doubt about the magnitude of these, the challenge was always in harnessing them so as to meet demand for reliable and affordable electricity.Today many countries are well advanced in meeting that challenge, while also testing the practical limits of doing so from wind and solar (variable renewable energy, VRE). The relatively dilute nature of wind and solar mean that harnessing them is very materials-intensive – many times that from energy-dense sources.Wind turbines have developed greatly in recent decades, solar photovoltaic technology is much more efficient, and there are improved prospects of harnessing the energy in tides and waves. Solar thermal technologies in particular (with some heat storage) have great potential in sunny climates. With government encouragement to utilize wind and solar technologies, their costs have come down and are now in the same league per kilowatt-hour dispatched from the plant as the costs of fossil fuel technologies, especially where there are carbon emissions charges on electricity generation from them.However, the variability of wind and solar power does not correspond with most demand, and as substantial capacity has been built in several countries in response to government incentives, occasional massive output – as well as occasional zero output – from these sources creates major problems in maintaining the reliability and economic viability of the whole system. There is a new focus on system costs related to achieving reliable supply to meet demand.In the following text, the levelised cost of electricity (LCOE) is used to indicate the average cost per unit of electricity generated at the actual plant, allowing for the recovery of all costs over the lifetime of the plant. It includes capital, financing, operation and maintenance, fuel (if any), and decommissioning.Another relevant metric is energy return on energy invested (EROI). This is not quoted for particular projects, but is the subject of more general studies. EROI is the ratio of the energy delivered by a process to the energy used directly and indirectly in that process, and is part of lifecycle analysis (LCA). An EROI of about 7 is considered break-even economically for developed countries. The US average EROI across all generating technologies is about 40. The major published study on EROI, by Weissbach et al (2013) showed: “Nuclear, hydro, coal, and natural gas power systems (in this order) are one order of magnitude more effective than photovoltaics and wind power.” This raises questions about the sustainability of wind and solar PV which have not yet been addressed in national energy policies. A fuller account of EROI in electricity generation is in the information paper on Energy Return on Investment.The World Energy Outlook 2016 (WEO2016) made the points that VRE have five technical properties that make them distinct from more traditional forms of power generation. First, their maximum output fluctuates according to the real-time availability of wind and sunlight. Second, such fluctuations can be predicted accurately only a few hours to days in advance. Third, they are non-synchronous and use devices known as power converters in order to connect to the grid (this can be relevant in terms of how to ensure the stability of power systems). Fourth, they are more modular and can be deployed in a much more distributed fashion. Fifth, unlike fossil or nuclear fuels, wind and sunlight cannot be transported, and while renewable energy resources are available in many areas, the best resources are frequently located at a distance from load centres thus, in some cases, increasing connection costs.These points are more fully put forward and modelled in the 2019 OECD Nuclear Energy Agency (NEA) publication, The Costs of Decarbonization: System Costs with High Shares of Nuclear and Renewables. All the modelling is within a 50g CO₂ per kWh emission constraint, and quantifies the system costs due to different levels of VRE input, despite declining LCOE costs (and zero marginal costs) for those. The concept of system effects, which are heavily driven by the attributes of VRE listed above, has been conceptualised and explored extensively by both the OECD International Energy Agency (IEA) and the NEA along with research from academia, industry and governments. System effects are often divided into the following four broadly defined categories:
  • Profile costs (also referred to as utilisation costs or backup costs by some researchers).
  • Balancing costs.
  • Grid costs.
  • Connection costs to the grid (sometimes included in LCOE).