Towards V2G

Grid integration of electric vehicles

Electric vehicles (EVs) have been stirring up significant attention and countries across the world have started laying down dedicated targets to cut emissions. In India too, EVs have received a policy thrust as many states have released their EV policy with an array of incentives. The Faster Adoption and Manufacturing of (Hybrid) and Electric Vehicles scheme has also helped create a momentum for the uptake of EVs. However, the large-scale penetration of EVs will require adequate charging infrastructure as well as the power grid’s ability to support the charging needs. In order to meet the expected demand of EVs, some key areas to consider should be the location of demand generation and whether the transmission and distribution (T&D) systems are prepared to handle such load.

Grid impact

Charging large fleets of EVs on low voltage networks will impact the planning and operation of power systems. The impact will vary according to factors such as penetration of EVs, energy mix, topology of the grid and driving patterns of EVs. Uncontrolled EV charging can cause a range of power network problems including voltage limit violations, component overloads, power system losses, phase imbalance and issues with power quality. With the rise in EV penetration, power drawn by the system will also increase, requiring additional infrastructure to be developed by discoms. Further, uncoordinated charging may result in voltage drops in heavily loaded lines. EV inverters may also create power quality problems while converting the power from direct current to alternating current by causing voltage and current harmonic distortion. Voltage and load issues can be eased to some extent with effective demand-side management. If the majority of the charging is carried out in the non-peak hours of the power system, congestions can be alleviated.

Focus areas for improvement

Shifting demand from peak to lower demand periods could be accomplished by imposing different tariffs during peak and off-peak time periods to incentivise off-peak charging. A dynamic pricing model could also be used besides smart grid tools for charging stations to encourage charging at non-peak timings. To curb uncontrolled charging putting pressure on the grid, a smart charging system should be established. In order to deliver power effectively, a demand-response mechanism should be put in place for signalling to consumers. This can be achieved through time-of-day tariffs. Specific network mitigation measures can also be undertaken. For instance, network reinforcement can reduce component overloads by increasing the load rating of components that are likely to be overloaded. There is a need to focus on grid ancillary services. There are many services that power generators and other ancillary service providers can offer to the grid. Ancillary services keep the grid stable by providing ramp up and down services, reserve services and frequency reserves. A series of regulatory reforms is required to ensure the effective implementation of ancillary services to meet system fluctuations throughout the day without destabilising the grid.

The EV models at present tend to have a shorter driving range than gasoline or diesel vehicles, and charging takes longer than filling up traditional internal combustion engine (ICE) vehicles. The lack of available and accessible public charging infrastructure adds to range anxiety. As the demand for long-range EVs grows, more innovative forms of charging and management solutions are required. There is a need to address challenges for the local grid infrastructure as well as vehicle-connected charging equipment. Connected and intelligent charging management solutions can enable widespread vehicle electrification without negatively impacting the grid, possibly providing additional benefits.

Integrating with solar

EVs can improve the reliability and utilisation of renewables by acting as a storage system, while generating distributed and reliable demand. EV charging equipment can also feed the grid at peak times if price incentives such as dynamic tariffs are provided as part of the smart grid implementation (vehicle-to-grid [V2G]). EV charging stations can be designed with rooftop solar generation to minimise the dependence on fossil fuels in the supply chain, hence shifting towards cleaner energy. Solar-powered EV charging stations can reduce power demand during peak times although they are vulnerable to weather changes. Battery-integrated EVs can significantly smoothen out charging spikes by transitioning from on-peak time charging to off-peak time charging. Combining EV charging equipment with energy storage systems and solar PV will eliminate high demand charges and maximise the use of renewables locally.

A study conducted by the National Renewable Energy Laboratory drew some conclusions about the use of solar power in EV charging. As per the study, daytime charging leads to more petroleum displacement, reduced range anxiety for drivers and increased adoption. Further, the use of controlled charging to synchronise the time of EV charging with that of solar generation increases benefits of both technologies. While uncontrolled EV charging poses a threat to the grid, controlled charging can help EV users plan their charging times and ensure grid optimisation. Integration with renewables may also need T&D system upgrades and significant grid-scale storage deployments to accommodate the shifting power demand and renewable power output throughout the day.

V2G

EVs have a large battery capacity that can be charged as well as discharged. To take advantage of this function, a technology called vehicle-to-grid (V2G) has emerged. V2G storage capabilities can enable EVs to store and discharge electricity generated from renewable energy sources such as solar and wind, with output that fluctuates depending on the weather and time of day. This is expected to relieve the grid stress due to the massive charging of EVs and utilise the potential of EVs to participate in grid ancillary services. The possible ancillary services include frequency regulation, load levelling (peak shaving), renewable energy storage, voltage regulation and congestion mitigation. EVs provide a cost-effective form of energy storage since they do not require huge additional investments or hardware. They serve a dual purpose in the transport and power sectors in this set-up. However, V2G is still a nascent technology and will require the use of smart charging and other compatible infrastructure in order to be functional on a large scale.

Outlook for the future

While the Covid-19 outbreak has put brakes on the automobile industry for a while, the demand for EVs is expected to slowly rejuvenate in the coming months and years. The recent introduction of BS-VI regulations in India has increased the costs of ICE vehicles, making EVs relatively cheaper. Further, with the government’s increasing focus on clean energy and private investments in the e-mobility segment, the EV industry is expected to weather the pandemic blow better than other vehicles. The Covid-19 lockdown has also lowered the overall power demand and thus the stress on the grid. Although progress in EV uptake may have taken a pause, this may just give the grid more time to prepare itself for the future large-scale penetration of EVs, smart charging and power management systems.

By Meghaa Gangahar

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