To avoid the worst effects of climate change, the Paris Agreement calls for keeping global warming below 1.5°C, preferably within 2°C. Currently, Earth's temperature is already about 1.1°C warmer than it was at the end of the 19th century, and emissions continue to rise.
To this end, many countries have proposed emission reduction and carbon neutrality goals. In 2011 the European Union (EU) proposed its climate target to reduce greenhouse gas (GHG) emissions by 80-95% by 2050 from 1990 levels, a necessary step to ensure global warming.
To achieve these goals, electricity sector emissions must first fall to zero, or even become negative by 2050. This will require large-scale implementation of low-carbon energy and carbon-negative technologies, such as renewable energy (RES), nuclear power, and carbon capture and storage (CCS).
Recently, the Deputy Director-General of Energy of the European Commission said that considering the energy problems caused by the Russian-Ukrainian war, the European Commission supports the goal of increasing the proportion of renewable energy, that is, to 45% by 2030.
Germany's proposed goals are more radical. The German federal government cabinet recently passed a series of draft legislation aimed at getting rid of fossil fuels and accelerating the development of clean energy, which set a two-stage target: 80% renewable energy power supply by 2030, and 100% renewable energy by 2035. powered by.
With the gradual shutdown of nuclear power plants and the grid-connection of a high proportion of wind power, photovoltaics, etc., the renewable energy power system will have strong uncertainty and instability. Planning and design, scheduling operation, stability control, power quality and other links have raised scientific problems to be solved.
Building a 100% renewable energy power system is not only as simple as increasing the proportion of wind power and solar energy, but also faces many challenges in technology, economy and policy. More importantly, it is necessary to plan for various renewable energy sources. In a reasonable proportion, it is necessary to build a soft, flexible and coordinated smart grid, and an adjustable large-capacity power trading market needs to be established.
As early as 1975, the Danish physicist B. Sørensen first proposed the construction of a 100% renewable energy power system, but the progress since then has been relatively slow. Driven by the upsurge of the energy revolution, the theoretical research on the 100% renewable energy power system is gradually deepening, but it is also faced with technical, economic and policy challenges.
100% renewable energy power system refers to the full use of non-fossil fuel and renewable energy such as water energy, wind energy, solar energy, biomass energy, ocean energy, geothermal energy, etc. (CSP) and other power generation devices are converted into electric energy, and finally reach the user side through the transmission and distribution network.
Similar but not identical in concept are carbon neutral power system (zero-carbon power system) and pure clean energy power system (100% clean energy power system). Among them, the carbon neutral power system is composed of nuclear power, renewable energy units and thermal power units with CCS. The main feature of this system is that the net CO2 emission is zero or even negative. For the pure clean energy power system, there is no unified definition at home and abroad.
The 100% renewable energy power system needs to realize fully renewable power generation resources, so it is necessary to completely withdraw from nuclear power based on a carbon-neutral power system, and make full use of CCS and natural gas synthesis technology to meet the energy storage and power supply needs of the system. The final result is a 100% renewable energy power system.
According to the Copernicus Institute for Sustainable Development at Utrecht University in the Netherlands: A sufficient supply of renewable energy (RES) alone does not mean that a 100% renewable energy power system is feasible, because the intermittent nature of wind and solar power makes electricity The balance of demand and supply is difficult.
In addition to variable renewable energy sources, the remaining demand must be supplied by dispatchable RES generation technologies (hydro, geothermal, etc.) or energy storage.
In the short term, technological constraints mean these plants may not be able to balance supply and demand fast enough, leading to overvoltages or energy starvation in the network.
In the long run, some years are sunny or windy, which means that wind and photovoltaic installations cannot be relied on to generate the same amount of electricity each year. Therefore, William et al. argue that any assessment of the viability of a 100% RES power system should include an analysis of its long-term and short-term reliability.
Some of the shortcomings of current research aimed at building a power system with 100% renewable energy mainly focus on:
When building a power supply planning scheme for a 100% renewable power system, it is necessary to focus on the strong uncertainty of new energy output, and build an economical and reasonable power supply planning scheme under the multi-dimensional requirements such as investment constraints, power balance, and adjustment capacity. Phase-out strategy of coal-fired power generation units and renewable energy power generation installation composition and capacity.
The geographic scope of the study includes the EU-27 as well as the UK, considering a broad portfolio of renewable energy generation technologies: including wind (onshore and offshore), photovoltaics (utilities and rooftops), biopower, CSP, geothermal and hydro. Aiming at the lowest total investment and operating costs, and constrained by conditions such as supply and demand balance, carbon emissions, energy storage capacity, and the development potential of various types of renewable energy, a linearized comprehensive energy system planning model is established to obtain the power supply configuration in multi-energy system planning scheme within.
A 100% RES system requires increased cross-border transmission capacity. Europe is structured as a single integrated electricity system in which electricity capacity can be shared among countries. This fully interconnected power system becomes critical to the reliability of transmission and ensuring system adequacy. Achieving transmission network stability in the high demand scenario would require the installation of 10 GW of new transmission capacity per year from 2016 to 2050, twice the rate currently planned.
A 100% RES system requires sufficient wind and photovoltaic capacity. European onshore wind energy is forecast to be installed mainly in countries bordering the North and Baltic Seas because of their favorable wind speeds and their central location in Europe, which minimizes transmission losses. Most countries will vigorously develop photovoltaics by 2050. Within countries, PV capacity is often installed in a more southerly location, or closer to load centers to reduce costs. According to William et al., by 2050, Europe can deploy enough wind and photovoltaic capacity to support a 100% renewable energy power system.
100% RES systems require a significant increase in biomass use: Unlike wind and photovoltaics, which are already installed significantly and are growing, the total installed capacity of solid biomass, biogas, CSP and geothermal in 2015 was only 18 GW, 10 GW, 2.3 GW and 0.8 GW. The deployment rate of any technology does not exceed 1 GW/year. To reach the 2050 installed capacity in the base case, CSP and geothermal capacity would need to average 6 GW and 1.4 GW per year, respectively, from 2016 to 2050.
While biomass will play a key role in a 100% RES power system in 2050, the future cost and potential supply of biomass is uncertain and will depend on future rainfall patterns, agricultural practices and biomass from other countries demand Department. A 100% RES power system that relies on biomass to provide stable capacity would be vulnerable to ultimately scarce and relatively expensive fuels.
A 100% RES system requires a significant reduction in the cost of renewable energy technologies. Different cost developments for different power generation technologies will affect the composition of the optimal renewable energy mix and their competitiveness with non-renewable energy alternatives. Although the cost of renewable energy has fallen rapidly in recent years, it still needs to fall by another 70% from base levels. The total annual cost of a 100% renewable energy system would be at least 530 billion euros per year, about 30% higher than a system that includes nuclear power or carbon capture and storage. Furthermore, these costs will increase relatively as demand increases.
A 100% renewable power system requires large amounts of hydro, CSP, geothermal, biomass or seasonal storage to provide capacity to balance variable wind and photovoltaic generation and meet demand when wind and solar supplies are insufficient. But none of these technologies are currently deployed to the level needed to support a 100% renewable electricity system in 2050.
The researchers say that even a 100% renewable energy system may not provide the level of emissions reductions needed to meet European climate goals, still requiring negative emissions from biomass captured and stored by CCS technology. Therefore, policymakers should ensure that all technology options are combinatorial and sound when guiding the transition to a reliable, cost-effective power system that meets European climate goals.
