The Development Plan and reduction of the electricity system’s CO₂ emissions

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The construction of the new lines and stations provided for by the 2012 Development Plan will produce positive effects not only in terms of service security and the end cost of electricity, but also of reduced emissions by the electricity system. Achievable upon completion of the Plan, the effects will be of three kinds:

  • reduction of grid losses;
  • improvement of the production mix and interconnection with other countries;
  • connection of plants using renewable energy sources.

Overall, the reduction of emissions within the time frame of the 2012-2021 Plan could reach the value of nearly 11 million tons a year.

Reduction of grid losses

Grid losses depend mainly, but not only, on the length the electricity travels on the transmission grid. To simplify: with equal consumption the farther the point of withdrawal (i.e., consumption) of electricity from the NTG is from the point of injection into the NTG of the electricity produced, the greater the losses. Furthermore, holding length constant, losses are greater on lower-voltage lines.

Therefore, losses can be reduced by work that improves the mesh of the grid, i.e. brings the points of injection and those of consumption closer to one another. They can also be reduced by upgrading a grid segment, for example by replacing a 150kV line with a 380kV one on the same route.

When all the work included in the 2012 Development Plan has been completed, the decrease in peak losses could reach 200 MW of power, which corresponds to a reduction of energy losses in the grid quantifiable as nearly 1,200 GWh a year. Assuming that the reduction of such losses is equivalent to a reduction in production from fossil fuels, it is estimated that the above-mentioned work will lead to a reduction in CO2 emissions ranging from 500,000 to 600,000 tons a year(1). 

Improvement of the production mix and interconnection with other countries

One of the main objectives of the transmission grid development is to overcome the limits of electricity transfer among “electricity zones”. These limits impose several restrictions on the possibility of production by generation units that are more efficient – i.e. less polluting in terms of CO2 emissions – and at the same time render production from obsolete and inefficient power plants necessary for the security of the grid.

Together with the upgrading of interconnection with other countries, the work provided for by the 2012 Development Plan will render a production mix possible that is more efficient than the current one, with a larger share of production from plants with higher yields. The same quantity of end consumption will be possible with a smaller quantity of fuel, and the benefits can be quantified as a reduction of CO2 emissions of up to 4,800,000 tons a year.

Connection of plants using renewable energy sources

The main contribution to the reduction of CO2 emissions is due to the connection of plants producing from non programmable renewable sources (NPRS) which are considered in the 2012 Development Plan works. The production of energy from renewable sources has grown rapidly in the last few years. In particular, NPRS generating plants have considerably increased, especially in southern Italy and in the islands.

During 2011, new wind and photovoltaic plants have gone into service, with nearly 8990 MW and 815 MW respectively of new installed capacity. One of Terna’s main tasks is to plan the upgrading of the NTG in order to encourage production of electricity from renewable energy sources by trying to overcome any grid and operating limitations that could condition the injection into the grid of such energy, which is entitled to dispatching priority.

In this regard, the works included by Terna in the 2012 Development Plan will release nearly 4,700 MW of power from renewable energy sources, to whom the beneficial effects should be added related to the installation of widespread storage systems of total capacity amounting to nearly 240 MW, thus obtaining a reduction of emissions amounting to nearly 6,000,000 tons of CO2.

 (1) The estimate was made assuming equal conditions. A change in consumption or the location of production plants could lead to different results.

MAIN WORKS OF THE DEVELOPMENT PLAN WITH EFFECT ON ENERGY EMISSIONS FROM RENEWABLE SOURCES

Category Works Power from renewable sources
(MW)
Grid upgrading indirectly functional for the reduction of operating limitations in dispatching generation, which favors production from non programmable renewable sources 380-kV “Sorgente-Scilla-Rizziconi” line and upgrading of the EHV grid in Sicily 1,000
Upgrading of interconnection capacity between Sardinia
and Corsica/continental Italy
500
New 380-kV “Aliano Montecorvino” line 900
380-kV “Foggia-Villanova” line 700
Upgrading of 380-kV “Foggia-Benevento” line 500
Work to upgrade and decongest EHV and HV grid sections into which production is injected from non programmable renewable sources Upgrading the transmission grid in southern Italy 1,100

Priority to energy from renewable sourcesEU8

In 2011, the injection into the grid of energy from plants powered from renewable sources has increased sharply with respect to previous years, by 18.8 TWh (6.5% of electricity demand in Italy)(4).

This increase is due to the growth of installed wind power (+13% year-on-year, for an installed capacity at the end of 2011 of nearly 6,200 MW) and to an increase of installed solar power (+260% year-on-year, for an installed capacity at the end of 2011 of nearly 12,500 MW).

The increase in the production from renewable sources satisfies environmental sustainability requirements, entailing a reduction of greenhouse gases, however, it has repercussions on the complexity of managing the electricity system, which is a consequence of the intermittence of the primary source and its unpredictability.

In order to adjust management of the electricity system to increased production from non programmable renewable sources, Terna has invested in technology and work methods for:

  • improving real-time forecasts;
  • optimizing the allocation of maintenance and the adjustment of operating procedures;
  • adjusting defense systems;
  • technical regulation.

Improving real-time forecasts

An accurate forecast of the injection of energy from renewable sources enables better dimensioning of operating reserve margins to be made available in substitution of renewable energy (if not available), with advantages in terms of both cost-effectiveness and security.

The investment made by Terna to improve wind forecasts through the use of self-learning expert systems has enabled the Company to reduce errors in forecasts of the injection from wind plants in 2011 to 11% – against 18% recorded in the previous year – reaching for the third year the improvement objectives as defined by AEEG.

The process of wind forecasts was also modified calculating, in addition to the forecasts up to the prior day, a re-forecast during the day of reference, with evident advantages in terms of reducing uncertainty concerning meteorological forecasts and consequent advantages in terms of the accuracy of the wind forecasts. 

As a result of the growth of photovoltaic facilities, in 2011, instruments for forecasting solar production were introduced, with additional difficulties with respect to what was already developed for wind resources, due to a greater widespread presence of such systems, which are outside of Terna’s control, given their connection to the distribution grid.  

Optimizing the allocation of maintenance and the adjustment of operating procedures

The unavailability of grid elements because of maintenance work can result in a limitation of the grid’s transportation capacity and, thus, of the production of the renewable sources plants concerned, in particular wind power plants connected to Terna’s sub transmission grid.

Therefore, in order to maximize production from renewable sources, Terna equipped itself with instruments and methods for optimally allocating maintenance, which include the following criteria:

  • long periods of unavailability, including those regarding grid developments in preparation of the upgrading of main lines with a high level of installed wind power, are allocated in periods with low windiness, which are identified through appropriate medium-term systems for forecasting;
  • brief periods of unavailability are allocated according to short-term forecasts of wind production (for example, allocation 24-48-hours in advance on the basis of the forecast of wind in specific areas of Italy).

Operational procedures for real-time dispatching by renewable source plants underwent further revision, also coordinated with operators that were owners of the plants, in order to be able to define on short notice possible limitations to wind production based on more certain information.

Thanks to such instruments and work methods, Terna has managed to limit considerably the limitations of wind production regarding the maintenance of grid elements (63% reduction of limitation hours).

Adjusting defense systems

The defense systems of the islands have been revised to include corrective automatic controls in the event of accidents connected to a higher amount of renewable generation, also through inclusion of renewable sources plants in defense systems.

Technical regulation

In 2011, greater growth in solar installations has made it urgent to develop applicable technical regulations. 

In this connection, Terna has updated the Grid Code to include technical descriptions of solar plants and a definition of management methods so that they can be fully integrated into the electrical system.  

With reference to distributed solar generation connected to distribution grids, technical regulation has been started in concert with distribution companies, due to the need for greater coordination in managing the transmission and distribution grids to safeguard the service continuity of reciprocal users.

(4) Provisional 2011 data as of February 2012.

 

Terna-Legambiente agreement for a sustainable energy culture

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The comparison with the environmentalist associations on themes of common interest was further enriched with a new and significant collaboration agreement.

On December 12, 2011 Terna signed a Memorandum of Understanding with Legambiente to promote all the initiatives necessary for disseminating an energy sustainable culture joining the development of the electricity system with that of renewable sources. Terna and Legambiente are both committed to promoting and disseminating knowledge on the energy world and to initiate joint activities for an environmentally sustainable energy transportation, starting from reducing CO2 in the atmosphere.

The Memorandum, that is valid until the end of 2013, includes sharing an operational plan for exchanging information and opinions on themes of common interest, particularly regarding the need for developing the National Transmission Grid (NTG) and the renewable energy sources.

To promote a proper approach on the first theme, Terna will arrange for technical analyses for measuring territorial and environmental integration of the works included in the 2012 and 2013 Development Plan and will analyze together with Legambiente the hypotheses of locating new electricity lines that will cross through sensitive areas of the national territory. The location choices for the electricity works will also involve Terna and Legambiente sharing any type of mitigation and compensation action for reducing to a minimum the visual and environmental impact.

With respect to “green” energy, the Memorandum includes specific analyses and studies on the state of the art and the development scenarios of the renewable sources sector also in relation to the connection to Terna’s grid of the renewable energy plants. This action is necessary for supporting the growth of the installations for which the company will provide on a quarterly basis, updated and additional information regarding development projects planned for promoting production.