Future energy-mix scenarios in Spain: feasibility and impact of a higher electricity supply provided by renewable sources

The evolution toward a higher use of renewable energies in the generation of electricity as a means of reducing the air pollutants and greenhouse gasses emitted to the atmosphere is the main objective in the current planning of the energy-mix development for most countries. To achieve this goal, the European Union has approved different directives and policies for both the short and longterm future, which aim to limit these emissions. The main objective of this research is to explore different alternatives in which the Spanish energy-mix can increase its share of renewable energies in the future in order to fulfil these environmental objectives and how it will affect the reliability and the costs of the electric system. The different scenarios designed have been analysed using PowerPlan, a computer model which simulates the electricity demand and production of a defined electric system and calculates different parameters, such as costs, reliability and emissions. This allows to compare the different results obtained with different scenarios to know which strategy is more convenient. To do so, a represenation of the current electric system has been designed using actual data from 2014. Subsequently, this represenation has been simulated with PowerPlan in order to calibrate it. After the calibration, the possible future development of the energy-mix have been simulated, considering a certain growth of electricity demand based on different forecasted values. As a simplification, the demand pattern of electricity has been considered to be constant throughout the simulation, which spans until 2050. The results obtained are used not only to ensure that the environmental objectives are fulfilled but also to find out which scenario implies a higher reliability and lower costs of operation. The research focuses only in the Peninsula, without taking into account the other regions of Spain as well as the international exchanges. The short-term objectives are set by the European Directives 2009/28/CE and 2010/75/EU, which focus mainly on the reduction of air pollutants and greenhouse gas emissions, respectively. The results obtained show that coal power must be reduced in order to fulfil the objectives. The plan designed limits the operative hours of coal plants until 2020. From then on, most of the coal plants are decommissioned, which results in a decrease of capacity down to 35 % of its current value. Plants that continue operating are obliged to invest in air pollutant reduction mechanism. The long-term objectives are set by two European policies: the 2030 climate & energy framework and the 2050 low-carbon economy. The first policy sets a 40 % cut in greenhouse gas emissions (compared to 1990 levels) by 2030. The results obtained show that the best strategy is to combine wind and solar power. This scenario fulfils the environmental objectives and assures the reliability of the supply, while reducing the surpluses produced. As a counterpart, the costs of electricity generation are higher. Additionally, it has been found that nuclear power should continue operating in order to fulfil the environmental objectives of this period. The second policy sets an 80-95 % cut in greenhouse gas emissions (compared to 1990 levels) by 2050. The main problem during this period is the high surpluses produced by a higher share of renewable energy in the energy-mix. The results obtained show that the best strategy is to combine pumped hydro with power-to-gas storage. The rest of non-renewable plants have been decommissioned by 2050, despite combined cycle plants, which operate in peak-load power. Some of them are equipped with carbon capture mechanisms that supply CO2 to power-to-gas plants, which produce the synthetic natural gas used in these combined cycle plants, resulting in a carbon neutral production of electricity. The optimal scenarios designed are the better option chosen among a few different scenarios designed, but they do not represent the ultimate optimal scenario that should be developed. The actual results that can be extracted from this research are the conclusion obtained in the design and simulation of scenarios, more than the exact values, given the assumptions and simplifications considered