Maintaining equilibrium in the European power grid

Utilities’ biggest challenge is the successful intergration of new generation sources
Credit: Ansaldo

Integration of Europe’s energy systems must continue if grid stability is to be sustained, says Dr Franco Rosatelli of Ansaldo Energia

The liberalization of energy markets in Europe and the separation of generation, transmission and distribution in most countries have played a vital role in increasing the efficiency of energy systems for the benefit of industrial users and consumers alike.

New players have strengthened their presence in the energy markets, endowed with higher efficiency, a greater propensity for investment, and greater generation capacity compared with former monopoly players.

At the same time, a significant improvement has been achieved in the transparency of decision-making processes at a regional and pan-European level regarding development of an interconnected European grid. This has been enabled by the publication of the Ten-Year Network Development Plan of the European Network of Transmission System Operators for Electricity (ENTSO-E) as part of the framework set out by the EU’s Third Energy Package.

Processes to harmonize Europe-wide requirements in light of current and future system developments have also been discussed regularly among network operators, stakeholders and regulators.

In 2013, ENTSO-E released its latest Network Code on ‘Requirements for Generators’ (NC RfG) and published NC RfG Implementation Guidelines to support the code by highlighting the impact on specific technologies, the link with local network characteristics, and the need for co-ordination between network operators and grid users.

Good progress has undoubtedly been made in respect of both market liberalization and EU policy; however, the economic and financial crisis of 2008-2009 hit at a time when energy systems were just starting out on their transformation journey. Unfortunately, it caught most utilities unprepared. Following a period of significant capital expenditure and increased mergers and acquisitions activity, most found themselves loaded with debt. This is why European utilities have been ranked among the worst-performing sectors in the global share indices over the last five years.

The biggest challenge they face, however, is the integration of new generation sources in a well-balanced mix. In an ideal world, the secure integration of growing amounts of renewables, together with wide-scale deployment of storage units, would meet demand at any time and ensure a stable frequency and voltage if steered via a robust backbone of combined-cycle power plants (CCPPs). In reality, the majority of conventional plants needed to sustain a secure supply are barely operating for a sufficient number of hours during the year to cover payback and maintenance costs.

The severe problems that arose in late 2013 with the grid in Germany exemplify the uncertain realities of renewables. A result of high wind power feed-in, alongside sudden load variations and power fluctuations provided by wind farms and solar parks, raised significant concerns over risks to grid stability.

Moreover, claims from clean-power groups that major European grids would be stable if renewables were the only sources of energy have also been called into question. The resulting price rise from the oversupply of renewable power has served to reinforce the belief that favouring green power, whilst maintaining a secure and stable supply, is a combination of incompatible objectives.

Certainly, a complex relationship has emerged given the wider deployment of renewables and how they impact on existing sources of energy. Stagnating electricity demand and the resulting deterioration of equilibrium in the generation mix could lead to a slowdown of energy market integration in Europe, as well as a rise in electricity bills and CO2 emissions due to the increasing contribution of coal-fired generation in parallel to the increase in renewables.

A more integrated approach is therefore advisable. Here, natural gas power stations can play a crucial role in assuring the stability and continuity of the power generation system.

Combined cycle power plants were considered crucial to liberalization
Credit: Ansaldo

In the early 2000s, the focus was mostly on CCPPs, as these were considered crucial to liberalization. Increased use of CCPPs over the past decade can also be attributed to their high efficiencies, short execution times and relatively low investment costs. By 2010 gas reigned in Europe, representing more than 50 per cent of the total power generation market.

Since then, wind and solar PV have taken the place of gas technologies and in the last few years have grown to account for more than 60 per cent of the power generation market. But given that the output of wind and solar power is highly variable, overcapacity of conventional power is needed in order to counterbalance these sudden variations.

In scenarios where renewable power has priority access to the grid, fossil fuel plants will have to increasingly shift their role from providing baseload power to providing fluctuating backup to meet unpredictable and short-noticed demand peaks, in order to control and stabilize the grid. This change in requirements throws down a real challenge for fossil fuel plants (CCPP and CHP), and for each component of the plant in terms of improving their operational flexibility for cycling and fast startup and shutdown times.

Plants should be able to run both at the lowest part load possible and at the highest possible efficiency. Moreover, they will be required to operate across the entire load range with high load-change velocities, and even operate in start/stop mode with full turndown and very fast restart, all at minimal emissions and fuel consumption.

This forces baseload plants to operate closer to their design limits, mainly in terms of increased thermal cycles. However, projects are underway that should lead to new technology that delivers more cost-effective and highly flexible solutions for new and current plants capable of meeting demand peaks and renewable output reductions at minimal fuel consumption, while mitigating the effects of cycling operation to avoid strong reductions in plant service lifetime.

The challenges should not be underestimated, but with technology developments promising greater plant flexibility and physical interconnection of the energy systems across Europe, there is an opportunity to build on progress so far and realize the better balance between affordable, clean and reliable electricity in Europe.

Franco Rosatelli is Chief Technology Officer – Innovation and Product Development at Ansaldo Energia

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