Carbon neutral archipelago – 100% renewable energy supply for the Canary Islands
Introduction
The need to mitigate anthropogenic global CO2-emissions increasingly focuses on the current energy system, which produced 78% of global greenhouse gas (GHG) emissions between 1970 and 2010 [1]. Policy already addresses the transformation of the existing system towards a more sustainable energy supply on a large scale [2] and local action plans aim at an increased use of renewable energies. The integration and balancing of large fluctuating renewable energy supply with the future demand represents major challenges for national and continental energy systems. For Island systems these challenges are even more pronounced. Owing to their remote situation, islands are often dependent on fossil fuel imports, which are typically expensive due to transport costs [3], [4]. Remoteness and size lead to small isolated markets, with few actors and a low diversity of technologies [5]. Island economies often rely strongly on tourism, with a high impact on structure and variability of the energy demand [4].
Renewable energy (RE) technologies provide solutions for a more sustainable and self-sufficient energy supply [6], [7]. However, the possibilities to balance fluctuations in power generation and demand through interregional electricity transmission are typically very limited or not available at all in island systems. Consequently, other flexibility options must be employed, including storage, demand response (DR) as well as synthetic fuel production [6], [7]. Considering this, island solutions can act as role models for future energy transition in larger systems.
Supply systems predominantly or fully reliant on RE technologies have been studied for various countries and islands. On a European level, the impact of different balancing technologies on electricity supply and costs has been assessed previously for RE shares of up to 80% [8]. In this work, grid could reduce costs at high RE shares, whereas storage was not cost-efficient. For Portugal, a 100% RE power supply system has been designed before, treating the country as an island system with no international electricity exchange [9]. The possibility of a fully renewable power supply has been evaluated as well for France, showing a significant need for flexibility options along with imports and DR [10]. For the United Kingdom, an analysis of the future power supply in high temporal and spatial resolution found that for more than an 80% RE share to be economically feasible, large-scale storage, significantly more power imports, or domestic dispatchable renewables must be available [11]. These studies were limited to power supply and did not consider energy demands of other sectors. For Ireland, is has been shown that electricity, heating, and transport demands can be completely supplied by RE [12]. Owing to the abundant availability of biomass, intermittent technologies played only a minor role in this work. With the analysis relying on the application of a detailed energy system model, it did not provide any cost assessment. In a subsequent study, the cross-sectoral transition towards 100% RE supply in Ireland has been described in more detail, including an economic assessment [13]. There, wind power was rated most important future energy source, whereas photovoltaics (PV) and ocean energy were not considered. Considering the whole energy system, a 100% RE supply has been designed for Denmark as well [14]. All these national studies did not evaluate internal power transmission.
Specifically for island energy systems, the RenewIsland methodology introduced in [15], provides a framework for mapping demand and supply of energy and water as well as the development of scenarios. Amongst other, it has been applied to Cozumel/Mexico, Porto Santo/Portugal, and Mljet/Croatia [16]. The model relies on a merit order approach and does not optimise the layout and operation of the system components. Based on high resolution data, potential supply cost reductions that can be achieved by RE technologies have been identified on almost 1800 small islands globally [17]. However, this analysis was limited to the power sector and did not consider other balancing technologies than battery storage and diesel generators. A more detailed comparison of electricity demand and RE potentials has been provided for Salina/Italy [18]. Similarly, it has been shown that up to 90% of the electricity demand of Dia/Greece can be supplied by RE technologies [19]. This work proposed to use surplus generation from intermittent resources for seawater desalination. By adjusting their operation to the availability of intermittent RE, desalination plants can enable supply cost reductions [20]. Applying a power system model in hourly resolution to the island of Lesbos/Greece, it has been found that a grid connection to the mainland can reduce supply costs and enable higher wind shares [21]. The importance of energy storage in island systems has been highlighted in a cross-sectoral case study for an imaginary island [22]. All these studies are limited to the assessment of energy demand and RE potentials, but do not provide a scenario of how to transform the energy supply system.
The available studies on sustainable energy systems and islands are limited mostly to the power sector, and do not reflect the advantages of linking power, heat, transport, and water supply. Furthermore, previous works did neither consider the supply potentials across the large bandwidth of RE technologies, nor provide pathways towards a 100% RE supply system. Instead, they focused either on the final or intermediate stages of the system transformation. Our paper closes this gap by providing a novel approach to the development of cross-sectoral transformation pathways towards a 100% RE system, focusing on a potential supply structure for the future local energy demand. We therefore combine a long-term outlook on transformation pathways with a detailed insight in the interdependencies of an interconnected energy system based mostly on fluctuating power sources. Additionally we focus on connecting neighbouring island power systems to provide insight beyond existing research. We apply this approach to the Canary Island archipelago, which represents an example for a remote island system of relevant size [23]. The archipelago with 2.2 million inhabitants is situated west of the African coast and politically part of Spain. Starting with Lanzarote and Fuerteventura, situated 100 km west of Morocco, the archipelago stretches out more than 300 km to the west across seven islands. Gran Canaria and Tenerife at the centre are the largest islands with a population of 0.85 million and 0.89 million people, respectively. Further to the west the archipelago extends to the smaller islands La Gomera, La Palma, and El Hierro. Tourism is the main economic sector and concentrated in the four larger islands. It is strongly developing, with guest-nights increasing from 11 million in 2010 to 14 million in 2014 [24], putting additional pressure on the energy system. The Canary Islands are part of a cluster of near tropical islands, featuring high solar irradiation, low precipitation with high seasonality. The seven islands feature low PV and wind generation costs at high generation rates and represent a large variety in population density and land availability [23]. As for many other islands and archipelagos, so far the Canary Islands’ energy supply depends almost totally on oil imports [25]. Alternatives are being assessed or promoted, including RE sources, natural gas imports and an improved grid connection between the islands [25], [26]. While transformation scenarios are already available on national level for Spain [27], they cannot directly be transferred to the remote Canary archipelago. One of the few previous studies dedicated to the archipelago’s energy supply proposed a wind powered pumped hydro system for the island of Gran Canaria [28]. Furthermore, the complementarity of natural gas and renewables in the Canary Islands has been evaluated, suggesting that both supply risks and costs are lowest in a balanced mix of both [5]. So far, no comprehensive long-term study of a sustainable energy supply in the Canary Islands is available. Starting from the current energy system, we elaborate a transformation pathway towards a 100% RE supply in the year 2050, considering RE and efficiency potentials as well as interdependencies between power, transport, and heating sectors.
The present paper is structured as follows: Section 2 gives an overview over the current energy system in the Canary Islands. Section 3 introduces the two applied models Mesap-PlaNet for long-term modelling and REMix for optimisation with high resolution as well as their calibration and linkage for this study. The model input data is described in Section 4. Model results including supply structures and impacts on CO2 emissions are presented in Section 5 and discussed in Section 6. Finally, the main conclusions from the results are drawn in Section 7.
Section snippets
The Canary Island energy system
The Canary Island’s government provides detailed statistics on the local energy system [25]. Currently this system is characterised by a heavy dependence on oil imports, delivering 99% of primary energy. Oil is used for power generation, heat production and land transportation. Road traffic accounts for 45% of internal final energy consumption, such as the residential, service, and commerce sectors, while industry plays a minor role (6%). Renewables are still in the beginning of their
Methodology
For the analysis of a 100% RE system in the Canary Islands, we enhance our modelling approach by linking the long-term energy system balancing tool Mesap-PlaNet with our deterministic high-resolution energy system optimisation model REMix (Fig. 1). Both models are introduced in the following as well as the link between them and the scenario approach for assessing future development pathways for the energy system.
Data
The calculation of the target-oriented scenarios is based on the development of detailed input data sets considering efficiency and RE potentials as well as technical parameters of power, heat, and synthetic fuel production technologies.
In a first step, the general Mesap-PlaNet model was adapted, calibrating model inputs and results for the starting year against statistical data for the Canary Islands for 2013 [25]. Where no data was available, the calibration was based on IEA energy balances
Results
In the following, we present scenario results along the modelling chain. Starting with the evaluation of the final energy demand and potential efficiency gains (Section 5.1), we then present the results of the REMix optimisation for 2050, focusing on the optimised mix of power plants and their regional disaggregation (Section 5.2). Finally, we provide an overview of the transition pathway for the whole archipelago (Section 5.3). Additional results are reported in [67].
Discussion
The scenario pathway to a 100% RE supply developed in this paper relies on a back-casting approach and provides a breakdown of long-term targets to short-term actions. It can be used as a guideline to a carbon-free energy supply for the Canary Islands, but does not represent a prognosis of the future. The decarbonisation scenario is limited to power, heat, and land transport, whereas aviation and navigation are not included. Owing to the restricted RE potentials in the Canary archipelago, these
Conclusion
This paper provides a novel approach to energy scenario design. It combines a cross-sectoral energy system model in high temporal and spatial resolution with an accounting framework. This modelling framework is able to simulate a consistent pathway towards a fully renewable energy supply and can be applied globally.
Our modelling results highlight the importance of transmission, storage, and flexible demand in energy systems with high share of fluctuating power generation. Furthermore, they show
Acknowledgements
The research for this paper was partially funded by Greenpeace Spain. The authors thank Red Eléctrica de España, Endesa Energía SA as well as the Instituto Tecnológico de Canarias for their valuable input regarding the Canary Islands power system. They furthermore thank Denis Hess for his support in the REMix-EnDAT application as well as Carsten Hoyer-Klick and Benjamin Fuchs for their valuable comments on previous drafts of this paper.
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