Maintaining equilibrium in the European power grid

Integration of Europe's energy systems must continue if grid stability is to be sustained, writes Dr. Franco Rosatelli* of Ansaldo Energia, ahead of the POWER-GEN Europe 2014 event being held in Cologne

Integration of Europe's energy systems must continue if grid stability is to be sustained, writes Dr. Franco Rosatelli* of Ansaldo Energia, ahead of the POWER-GEN Europe 2014 event being held in Cologne

The liberalisation of energy markets in Europe and the separation of generation, transmission and distribution in most countries have played a crucial 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 European Union's Third Energy Package.

Processes to harmonise European-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, as well as the need for coordination between network operators and grid users.

Utilities caught unprepared

Good progress has undoubtedly been made in respect of both market liberalisation and EU policy, however the economic and financial crisis in 2008/9 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 CapEx and increased mergers & 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 indexes over the last five years.
The biggest challenge they face however, is the integration of new generation sources to arrive at a well-balanced mix among the different types of generation technologies, especially since stagnating electricity demand and the resulting deterioration of the equilibrium in the generation mix could lead to a slowdown in the progress of energy market integration in Europe.
In an ideal world, the secure integration of growing amounts of renewable energy, 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. 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.

This is particularly true in markets such as Italy and Germany, where there has been a significant generation overcapacity due to the rise in renewable energy. The severe problems that arose in late 2013 with the power grid in Germany exemplify the uncertain realities of renewable energy sources. 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 the risks to grid stability.

Moreover, the 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 generation, whilst maintaining secure and stable supply, represents a combination of incompatible objectives.

From gas to renewables

Certainly, a complex relationship has emerged given the wider deployment of renewable energy sources 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, given that an overcapacity of conventional power is needed to counterbalance sudden variations in the availability of renewable energy. Here, natural gas power stations can play a crucial role in assuring the stability and continuity of the power generation system.

In the early 2000s, the focus was mostly on Combined Cycle Power Plants (CCPP), as these were considered crucial to liberalisation. Increased use of CCPPs for power generation over the past decade can also be attributed to their high efficiencies, short execution times and relatively low investment costs. By 2010, gas technologies 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, and depends on factors such as time of day and prevailing weather conditions, overcapacity of conventional power is needed in order to counterbalance these sudden variations.

Shifting role

In scenarios where renewable power has priority access to the grid, fossil fuel power plants will have to increasingly shift their role from providing base-load power to providing fluctuating back-up power to meet unpredictable and short-noticed demand peaks, in order to control and stabilise the grid. This change in requirements throws down a real challenge to fossil fuel power plants (both CCPP and CHP) and for each component of the plant (Gas Turbine, Steam Turbine, Heat Recovery Steam Generators and other pressure parts) in terms of improving their operational flexibility for cycling and fast start-up and shut-down 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 re-start, all at minimal emissions and fuel consumption.

This forces base-load 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 power 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 shouldn't 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 the progress so far and realise the better balance between affordable, clean and reliable electricity in Europe. Certainly, this will be a key topic of debate at this year's POWER-GEN Europe conference.

Franco Rosatelli is on the Advisory Board for POWER-GEN Europe a committee of industry leading professionals responsible for agreeing the conference programme for this events. Being held 3-5 June 2014 in Cologne, Germany, POWER-GEN Europe is co-located with Renewable Energy World Europe and is the leading European Conference and Exhibition for the power industry to meet, share information and do business. Addressing topical issues critical to the development of power generation in the host region, the conference theme for 2014 is Navigating the Power Transition. Track one of the conference looks at strategy for a changing energy sector, with a session on Wednesday 6 June dedicated to decentralised generation and system integration.

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