Coal phase-out and integration of renewables? Czech power grid poses no obstacle

The full study called Czech Power Grid without Electricity from Coal by 2030: Possibilities for Integration of Renewable Resources and Transition into a System Based on Decentralized Sources is available at the end of article.

The current European trend comprises a redirection of the energy sector from coal to renewables. This process often raises the question whether electricity production from sources which are highly dependent on weather could threaten power grid stability and energy supply security. This question is quite reasonable considering the speed of the transformation process – renewables share on EU energy production are currently 30 % and is still rising. This increase is caused mainly by solar, wind and biomass generation. The Czech Republic has, until now, been eluding these changes. However, the numbers are clear: It is not possible to achieve the decrease in greenhouse gases emissions as stipulated by the Paris Convention with the current energy mix settings.

A thorough assessment of the power grid capabilities is one of the crucial points in the debate on energy transformation. The study at hand, being first of this kind in the Czech Republic, shows that the power grid is no obstacle to phasing out coal-fired power plants and integrating more renewables into the system.

The research was carried out by a renown German consulting company Energynautics, upon a request of Czech organizations – Glopolis, Frank Bold, Hnutí Duha (Friends of the Earth Czech Republic), CEE Bankwatch Network and ALIES.

The study is based on the results of a complex modelling through a computer software developed by Energynautics experts. The presumptions of the scenario were that all coal power plants which are used mainly for electricity generation (as opposed to cogeneration heating units) will be phased out by 2030. Another presumption was an increase in renewables electricity production: the model expects an increase in installed capacity of wind power generation from 278 MW in 2107 to 2050 MW in 2030, and of solar power generation from 2100 MW in 2017 to 5500 MW in 2030. The modelled scenario also included variations of energy sector development in the neighbouring countries. The software simulated the conduct of Czech power grid under the aforementioned conditions for all the days of a whole year.

The main findings of the study are:

• The Czech transmission grid presents no major obstacle to the transformation from mainly coal based generation to renewable energy due to the size of the Czech Republic, the high degree of redundancy found in the design of the existing grid, the distribution of renewables within the country and the large share of renewables from biomass and biogas.
• The phase-out of coal generation capacity transforms the conventional power fleet away from baseload coal and toward a more balanced generation mix with flexible and mid-merit generation capacity. While nuclear power and biomass continue to more or less provide inflexible, nearly constant power generation (baseload), the power system in the assessed scenarios will be characterized by a variety of flexible resources, including gas fired units (OCGT and CCGT), reservoir hydro, pumped storage, flexibly operated CHP and biogas plants, as well as storage and demand response.
• Coal capacity does not have to be replaced on a one-to-one basis due to the reduction of surplus capacity, the increased utilization of existing plants and the building and use of more efficient gas power plants.
• In the scenarios assessed, exports as a share of overall electricity generation declines to 5.7%-10.5% in 2030 compared with 14.9% in 2017. However, the Czech Republic remains a major exporter of electricity (mainly to Poland and Germany), with estimated net exports of 4.2 – 8.07 TWh in 2030 depending on the scenario.
• All scenarios assessed showed very little necessary curtailment of wind and solar, with curtailment increasing only slightly in case of a delay of the German HVDC corridors (e.g. 1.39% vs 0.22% curtailment for wind generation). By contrast, a delay in the construction of the German HVDC line slightly increases net electricity exports due to increased exports to Southern Germany.
• No grid reinforcements were identified as strictly necessary under the 2030 scenario, however, some projects in the East of the Czech Republic could be considered.
• An assessment of potential stress cases from high shares of variable renewables (wind and solar) with little synchronous generation from conventional power plants to provide inertia shows that these circumstances are highly manageable and do not pose a threat to system stability if system operations are adapted.
• The scenarios assessed for this study were also generally found to have enough large units left to provide reactive power and voltage control in the grid, however, further study is recommended so that existing technical fixes (e.g. FACTS, synchronous condensors) can be implemented where and if needed.
• The demand for at least some reserves (aFRR) are expected to potentially slightly increase with higher installed wind and solar capacities. The generator portfolio is generally capable of providing enough reserves under the assessed scenarios, but some reforms of reserve markets are recommended to enable the cost-effective participation of a wider variety of generators and technologies.