1. Introduction
Nowadays, the transport sector accounts for a quarter of the global CO
2 emissions from fuel combustion. In particular, road transport, which is highly dependent on fossil fuels such as petrol and diesel, represents around 75% of the sectoral emissions [
1]. According to a central document from the European Commission setting targets in terms of greenhouse gas (GHG) emission savings with milestones in 2030 and 2050 to decarbonise the energy system [
2], GHG emissions associated with the transport sector must decrease between 54% and 67% with respect to the 1990 levels. Since the transport sector has a low share of renewable energy, considerable efforts are required for its transformation [
3]. In this sense, alternative transportation fuels should be explored in order to mitigate the climate change impact linked to conventional fuels.
Within this context, the future transportation fuel mix is expected to involve alternative fuels such as natural gas, electricity, hydrogen, and biofuels. In particular, the penetration of electric vehicles (EV) could significantly contribute to achieve the decarbonisation of the transport sector [
4]. Spain, as well as other member states of the European Union, is actively involved in the fight against climate change and contemplates EV penetration as a potential energy solution for the road transport sector, even though binding policy targets have not yet been set for Spain. There are several studies in the literature which estimate different penetration rates for EV in Spain, as summarised in
Table 1 [
5,
6,
7,
8,
9].
A massive implementation of EV will have consequences for the electricity production mix due to the need to satisfy an increased electricity demand. In other words, the additional electricity demand associated with EV penetration will be supplied by a set of power generation technologies, leading to modifications in the electricity production mix and thus implications on its sustainability performance. Besides, this deployment will have effects in terms of energy planning regarding capacity expansion, demand projections, peak load requirement, etc. In this regard, the combined use of well-known methodologies such as Energy Systems Modelling (ESM) and Life Cycle Assessment (LCA) [
10] seems suitable to evaluate the prospective techno-economic and environmental performance of power generation all at once [
11,
12]. In the field of ESM + LCA, the benefits associated with an enriched analysis of energy systems should outbalance the current limitations in terms of results accuracy (e.g., lack of hard-linking approaches) and time consumption (e.g., in building energy systems models) [
12,
13].
Prospective EV penetration is a topic already studied by several authors. For instance, Liu et al. [
14] evaluated the variability of the electricity demand under the hypothesis of full penetration of EV in the Scandinavian countries by 2050. Bohnes et al. [
15] and Zhang et al. [
16] carried out analyses of the environmental impacts resulting from EV deployment in Copenhagen and Beijing, respectively. Höltl et al. [
17] analysed several scenarios including the electrification of the car fleet in Europe and its consequences. Within this context, this work addresses a prospective LCA study to evaluate the potential climate change (CC), human health (HH), and resources (Re) impacts of the increased electricity demand associated with EV penetration in Spain. As a novelty, this is done under three alternative scenarios of EV penetration and relying on the endogenous integration of life-cycle indicators into a national energy systems model (
Section 2). In addition to the influence of EV penetration on the prospective electricity production mix and its evolution under life-cycle sustainability aspects, the potential environmental benefits linked to the substitution of electricity for conventional fuels are preliminarily assessed (
Section 3). Although this study is especially useful for long-term energy planning at the national level, the methodological framework and the results presented are expected to be useful for a wide range of countries and actors facing similar decision- and policy-making concerns.
2. Materials and Methods
García-Gusano et al. [
18] carried out the endogenous integration of several life-cycle indicators (viz., CC, HH, and Re) into an energy systems model of power generation in Spain based on LEAP-OSeMOSYS. This is an optimisation-based energy systems model that minimises the total system costs. The minimisation of the objective function—a sum of investment costs, fixed and variable costs, fuel costs, etc. of the existing and new electricity production technologies—is subjected to different constraints regarding emission reductions and capacity limits. The energy demand projections are entered exogenously into the model and are based on the behaviour of key socio-economic drivers such as gross domestic product (GDP), energy prices, and population. This type of model usually compares a set of scenarios against a reference case (business-as-usual, BaU).
In [
18], the BaU scenario did not take into account EV penetration due to the lack of binding policy targets in this regard. Hence, as shown in
Figure 1, this article proposes a framework based on the combined use of ESM and LCA for the analysis of the influence of EV penetration in Spain. In comparison with previous studies [
18], the main novelty is the formulation and implementation of three transport-related scenarios for the corresponding prospective analysis of both the electricity production mix and life-cycle sustainability indicators with time horizon 2050. Thus, this work extends that in [
18] by implementing three alternative scenarios of EV penetration in addition to the BaU one.
Regarding prospective electricity production mixes, the comparison of the results for the alternative scenarios with those for the BaU scenario allows the identification of the power generation technologies that are expected to satisfy the increased electricity demand of the Spanish road transport sector. According to the original energy systems model of electricity production in Spain [
18], the following power generation technologies are included: coal thermal, natural gas combined cycle (NGCC; both with and without CO
2 capture), oil combustion engine, cogeneration (natural gas turbine), nuclear (pressurised water reactor –PWR– and boiling water reactor –BWR–, as well as generations III and IV and nuclear fusion), hydropower (dam and run-of-river, RoR), wind (onshore and offshore), solar photovoltaics (PV; both roof and plant), solar thermal (with and without storage), biomass power plants, waste-to-energy plants, biogas power plants, coal-based integrated gasification combined cycle (IGCC), proton exchange membrane fuel cells (PEMFC), solid oxide fuel cells (SOFC), tidal power plants, wave power plants, and new geothermal power plants.
Thanks to the endogenous integration of a set of life-cycle indicators –CC, HH, and Re– into the energy systems optimisation model of power generation in Spain, the results also include the evolution of the cradle-to-gate impacts of the increased electricity demand associated with EV penetration. These life-cycle indicators—which represent quality changes of the environment affecting the ecosystem and/or human beings—are evaluated according to the IMPACT 2002+ method [
19].
In order to calculate the extra demand of electricity caused by EV penetration, several vehicle categories are considered along with their corresponding distribution, energy consumption, and average annual mileage, as presented in
Table 2. The values in this table are assumed to be constant during the whole time frame.
Finally,
Table 3 quantitatively presents the energy scenarios evaluated in this study. In particular, in addition to the BaU scenario (which is based on [
18] with minor updates regarding the historical EV penetration for the period 2011–2015 [
7]), three alternative scenarios are formulated according to the EV stock assumed in the road transport sector in Spain in 2020, 2030, 2040, and 2050. The formulation of these alternative scenarios is founded on the targets proposed in the studies included in
Table 1. Thus, the scenario LOW is based on a slight penetration of 10 million EV in 2050, which results in an increased electricity demand of 9 TWh. On the other hand, the scenario MEDIUM considers a penetration of 14 million EV in 2050, which leads to an extra electricity demand of 12.6 TWh. Lastly, the scenario HIGH is based on a penetration of 20 million EV in 2050, which translates into an additional electricity demand of 18 TWh. In any case, EV deployment is found to involve a relatively small percentage (<4%) of the final electricity demand.
4. Conclusions
The electricity demand associated with the future penetration of EV in the Spanish road transport sector is expected to be mainly satisfied by an increased contribution of onshore and offshore wind power to the electricity production mix. This would generally lead to a slight increase in the annual life-cycle impacts of the power generation sector. In this regard, under a high market penetration of 20 million EV by 2050, the highest annual climate change, human health, and resources impacts of the EV-related electricity would be 0.93 Mt CO2 eq, 0.25 kDALY, and 30.34 PJ, respectively. In fact, these minor impacts would be outshined by the high environmental benefits within the transport sector due to the avoidance of conventional fossil fuels to perform the same transport function. In this sense, net annual impact savings of up to 10–20 Mt CO2 eq, 4–9 kDALY, and 149–301 MJ were estimated under three alternative scenarios on the penetration of EV in Spain (10–20 million EV by 2050). Overall, ambitious targets for EV penetration in countries such as Spain are deemed feasible and suitable from a life-cycle sustainability perspective.