GRÁFICO N° 38 El personal de la comida

Faced with the threat of climate change, many nations have been setting targets to reduce carbon emissions. For example, the UK government has committed to reduc- ing emissions by at least 80% of 1990 levels by 2050 [26]. To reduce our dependency on fossil fuels, we have seen a huge surge in the development of renewable energy and so-called ‘smart’ technologies, such as smart metering in homes, electric vehicles, and various forms of energy storage. As technologies become more cost-effective, ei- ther through technological advances, mass-production or government subsidies, they are becoming increasingly prevalent on the GB power grid. Such changes naturally bring a mixture of challenges and opportunities for system operability, which must be carefully navigated. Anticipating changes to demand and generation and the potential issues requiring mitigation is part of the role of the SO.

tions for the changes to energy supply and demand in the coming decades, based on input from stakeholders from all areas of the energy industry. The 2017 scenarios (projections to 2050) are

• Two Degrees (TD) - high economic growth and investment in green technolo- gies and strong government policy to drive change, the only scenario in which the UK meets its carbon targets

• Consumer Power (CP) - high economic growth, lower focus on green govern- ment policies, market-led investments in smaller generation with shorter-term financial returns

• Slow Progression (SP) - low economic growth competes with desire to meet carbon targets, cost-effective long-term environmental policies

• Steady State (SS) - low economic growth, business as usual, security of supply at low cost, little investment in long-term solutions, the ‘least-green’ scenario.

Figure2.2shows the projections for the installed capacity of each class of generation for each of the four scenarios. We see a moderate-to-large increase in the installed capacity of renewables in all four scenarios. The role of interconnectors and storage also increase, as the amount of installed fossil-fuel generators reduces.

Figure 2.2: Installed generation capacity projections by type, for each energy sce- nario in the 2017 FES [27].

an electricity grid that arise from increased use of renewable energy, in particular wind power and solar PV, such as [1,9,28–31]. The key operational challenges for a grid with a high penetration of renewables (or distributed renewables) are reduced inertia, greater RoCoF (Rate of Change of Frequency), fewer generators capable of providing frequency response, voltage fluctuation and harmonic distortion, power quality issues, and the supply volatility and unpredictability caused by the nature of the weather. The challenges most relevant to our work are the first three, which directly impact the electricity grid frequency and/or the need for greater frequency response.

As discussed above, the higher the system inertia, the slower the system will be to grid frequency fluctuations. To provide inertia to the system, a component must be synchronously connected (rather than connected with a power electronic converter). To provide a significant amount of inertia, the component needs to have large rota- tional inertia, such as a heavy motor or a turbine in a power plant. Solar panels have no moving parts and therefore contribute no inertia to the system. Wind turbines and interconnectors are connected via power electronic converters, and so at present they are unable to supply system inertia. With lower inertia the frequency changes more rapidly. When the RoCoF is high, the load-shedding controller will decouple its component(s) from the system to protect them. Certain renewable technologies such as solar PV are particularly sensitive to high RoCoF and in the event of a fre- quency incident may remove themselves very quickly from the system, exacerbating the frequency issues.

Traditionally energy was generated by a relatively small number of very large power plants, such as coal, oil and gas. In recent years energy generation has become far more distributed, meaning that we now have a large number of very small generators on the distribution network with a large spatial distribution. These generators are often invisible and beyond the control of the SO9. They can also dramatically alter the way power flows in the distribution network, since bi-directional flows become possible. In recent years decentralised generation has grown to comprise over a quarter of installed capacity in GB. National Grid’s Future Energy Scenarios [32] anticipates that this percentage will increase to 34-40% by 2025 and to 34-50% by 2050. According to their analysis, to achieve the UK carbon targets would require the highest percentage in each of these ranges.

The analysis presented in National Grid’s System Operability Framework 2015 [9] 9

The SO does not have direct observation of these generators and their effects are seen as reducing system demand.

predicts a number of challenges for frequency control going forward. System inertia is expected to reduce over the next 20 years in all four future energy scenarios during periods of low demand and/or high renewable power generation. Primary frequency response requirements are expected to increase by 30-40% by 2020, and new response providers will be needed to meet these requirements.