Electric vehicles (EVs) represent an important socio-economic development opportunity for islands and remote locations because they can lead to reduced fuel imports, electricity storage, grid services, and environmental and health benefits. This entry presents an overview of opportunities, challenges, and examples of EVs in islanded power systems, and is meant to provide background to researchers, utilities, energy offices, and other stakeholders interested in the impacts of electrification of transportation. The impact of uncontrolled EV charging on the electric grid operation is discussed, as well as several mitigation strategies.
In remote and island areas, the benefits of EVs can be even more significant than on mainland systems. For example, fuel supply chains for island and remote communities are particularly volatile in both price and availability, so the higher efficiency and fuel flexibility of EVs (EVs can charge using electricity generated from any fuel) present an opportunity to stabilize and reduce transportation costs. EVs represent an important socio-economic development opportunity for remote and island locations because they hold the promise of reduced fuel imports, are an electricity storage resource, can provide grid services, and can result in improved environmental and health conditions. To directly show the cost savings achievable through electrification of transportation, Figure 1 shows the comparison of the cost of a gallon of gasoline to an equivalent value for EVs. In nearly all cases, EVs have a reduced cost of operation when compared to gasoline vehicles. A modified eGallon was used  for this comparison, based on miles per gallon and kWh/100 miles for 2019 Hyundai Kona gasoline and electric vehicles.
Beyond direct cost savings, the potential abilities to (a) control EV charging as a form of demand response to support the centralized electric grid, and (b) couple EV charging with distributed energy resources (DERs) such as rooftop solar photovoltaics (PV) are particularly valuable features of the electrification of transportation in island and remote systems. Coupling with PV can not only lessen grid impacts (dampen positive or negative ramps in net load), but can also be used in emergency-response applications to charge EVs directly from the PV when the centralized electric grid is out .
Yet, in the smaller electric grids of remote and island areas, relatively modest amounts of EVs can result in significant increases in total electric load, which could pose challenges to grid operations. Technical obstacles include grid reliability issues, increased generation capacity needs due to shifts in daily peak demand, and grid upgrade and maintenance costs . High EV penetration (percentage of total load due to EVs) in remote and island systems may require large grid and charging infrastructure investments and supportive policies, which might not currently exist in small islands with uncertain regulatory/policy environments .
This entry documents previous research and implementation efforts for EVs in islands. The works described focus on island or remote energy systems and their grid impacts as well as mitigation approaches for high EV penetrations. Key topics include: (1) the impact and potential mitigation options of integrating EVs into remote and island electric grids and, (2) the need for an overarching energy policy that can serve as a framework or guide to EV adoption strategies. The importance of a holistic energy policy is illustrated through case studies on the impact differing policies have had on EV adoption and operation.
Two interrelated studies modeled the impact of EV charging in the island grid of São Miguel, Azores, Portugal for a group of residential customers  and for an industrial customer allowing employee workplace charging . São Miguel has a total system load of 140 MW , though the residential load considered in  was 292 dwellings totaling 140 kW at peak load, and the industrial load in  also peaked around 140 kW. Despite the similar peak load values, the transformer serving the residential customers (630 kVA) was much larger than the one serving the industrial customer (250 kVA), as the residential transformer was sized based on expected seasonal increases in the residential load. Due to all EVs beginning to charge at the same time and the transformer size differences, overloading was found through simulations at 75% EV penetration in the residential scenario but at only 40% EV penetration for the workplace charging scenario. Both studies additionally estimated a shorter transformer lifecycle when EV penetrations led to transformer overloading. In the residential case, 3 h of daily transformer overloading due to 100% EV penetration would result in approximately 6 h of transformer life reduction each day. The industrial transformer was particularly stressed by fast-charging scenarios (regular charging rates were up to 7.4 kW, fast-charging rates were up to 50 kW), with approximately 58.5 h of service life lost for every one day of fast-charging operation at 35% penetration. This was heavily influenced by the transformer size and 3 daily overload peaks caused by all EVs starting to charge at the beginning of each work shift.
An example of line overloading comes from a study modeling an actual distribution feeder in the island of Trinidad . While Trinidad has an installed capacity of about 2200 MW , the feeder studied had about 5 MW of load. An increased amount of line overloading was observed when EV penetration levels reached 10%, though it should be noted that some line overloading is found to occur even before EVs are added. Consistent with the note in the previous paragraph, the authors comment that, “…known issues such as pole-mounted transformer overloading were intentionally neglected due to the understanding that it is inevitable that overloading will occur and can be addressed by simply resizing to a higher transformer capacity” .
As EV penetrations become significant, increased loads due to EV charging may cause voltages on distribution grids to drop below acceptable voltage limits. A common range of acceptable voltages is + /−5% (e.g., ANSI C84.1 Range A ) , such that at a 120 V customer, for example, the centralized grid must deliver voltage between 114 V and 126 V. Having too low or too high of a voltage on a distribution feeder can result in adverse impacts including unscheduled maintenance, early equipment replacement, damage to customer equipment, and in extreme cases, increased grid outages resulting in lost revenue . Several studies of island systems have simulated that voltages will decrease below allowable limits during the simultaneous charging of many EVs.
The study using the feeder model from Trinidad described earlier found that voltages dropped below acceptable limits at several feeder nodes when EV penetrations of as little as 5% were implemented . Voltages were already very close to lower limits before any EVs were connected, a state which may be common in island and remote systems due to grid design and operation considerations.
The challenges of EV integration motivate research on the impact, mitigation, and effective controls of EV charging. This research will immediately benefit remote and island systems and will also be valuable to larger mainland systems in coming years as EV penetrations become significant on larger mainland electric grids, which will take longer.
It is very important to reduce the negative impacts to the electric grid from the early stages of EV adoption to avoid limits on further EV adoption . While upgrades to electric grid infrastructure, such as increasing the size of conductors (to avoid line overloading), increasing the size of transformers (to avoid transformer overloading), or adding voltage control devices (to keep voltage in allowable ranges), can directly mitigate most concerns, they typically are high-cost and require significant installation efforts. Cheaper and easier to implement mitigation strategies will involve the EVs in grid operations, including simple control strategies for EV charging (e.g., use of timers), controlled EV charging in response to the state of the electric grid, EV chargers providing grid services to assist with grid operations, and integration of EVs with DERs.
EVs can provide grid support services (also known as “ancillary services”) to reduce their impact and support electric grid operations. For example, EVs can be used as a form of demand response, reducing their charging during periods when the electric grid is stressed, such as if a generator fails or when load is unexpectedly high. EV chargers can also be configured to provide voltage support, such as through volt-var control schemes which have become common in PV inverters .
A study in São Miguel looked at how EVs could support an increase in the use of renewable energy and presented possible grid-related revenues for EV owners . The study assumed bi-directional EV charging, that is, EVs could be used as dispatchable storage devices. When EV owners were compensated financially for providing ancillary services, EVs had lower total costs of ownership than conventional vehicles, even though EV purchase costs were significantly higher than conventional vehicles. However, as EV penetration increased, revenues from providing grid services decreased for individual EV owners. An important finding was if high EV penetrations are achieved and controlled effectively, nearly all of the variability in the total system’s electric demand curve can be eliminated, which would simplify and reduce the cost of electric generation needed.
Another way to mitigate the impact of EV charging is to place chargers at robust nodes in the electric grid such that large numbers of chargers can be installed without overloading system components or causing voltage issues.
EV chargers are already prolific on the island of Jeju, South Korea, with 1103 express charging points and 344 slow charging points (full recharge overnight) . The voltage and loading challenges highlighted in  are being addressed through strategic placement of new chargers , among other strategies (e.g., encouraging EV charging stations powered from renewable stations ).
EVs can be strategically controlled to enable higher penetrations of variable renewable energy resources by increasing charging during times of high renewable generation and decreasing charging during periods of low renewable energy generation. An example is shown for the Portuguese island of São Miguel where charging strategies were examined . The EVs were able to help flatten the island’s daily demand curve for different scenarios up to 32% EV penetration. Similarly, a study for the Portuguese island of Flores (peak load of approximately 2 MW ) looked at how EVs could increase the use of renewable energy . Optimal charging strategies were studied using a dynamic programming algorithm, and the main result was that controlled charging of EVs reduced both the need for backup generation and the amount of wind energy curtailed.
Overall, the works presented in this section demonstrate that EVs charging from renewable DERs can be mutually beneficial. EVs benefit from cheaper electricity with lower emissions, while renewable DERs can increase utilization and even allow for new installations as EVs utilize power which may have previously been curtailed due to a lack of demand or a concern over high penetrations of renewable energy resources.
In the Caribbean, for example, the long-term impacts of an EV transition need careful consideration due to limits on electrical and business infrastructures. The Caribbean Community (CARICOM) Regional Electric Vehicle Strategy (REVS) Framework provides the foundation for a transition to EVs in the Caribbean. The REVS acknowledge the importance of changing transportation systems at the local level, as well as accounting for driving behaviors and transportation preferences of individuals. The framework provides guidelines in the following areas: Policy and regulation; technology and infrastructure; capacity development and awareness; finance, market development and innovation. It has a strong emphasis in a market approach, inclusion of relevant stakeholders, capacity building, prioritization of public and commercial transportation, and the key role of technology and infrastructure improvements. Other important regional references for the Caribbean are the position paper “The Future of E-Mobility in the Caribbean” from the Caribbean Centre for Renewable Energy & Energy Efficiency (CCREEE)  and the report “Electrified Islands: The Road to E-Mobility in the Caribbean”.