Green-Tinted Glasses: Electric Vehicles and Renewable Energy
In a previous article, “Electric Vehicles and their Infrastructure: The Chicken/Egg Dilemma,” I discussed the ability for electric vehicles to integrate into existing electrical-grid infrastructure as well as their infrastructure requirements in general. Looking to the future, the question arises: in a world that is moving increasingly towards renewable energy sources for power, how do EVs fit into the picture?
Driving an electric vehicle today is, environmentally speaking, a smart decision. Given that it may be charged using a renewable source, even better. Large-scale integration of EVs into the transport sector, while presenting an opportunity to reduce greenhouse gas and pollutant emissions and enhance local air quality, may even serve to drive possibilities for renewable power to become more mainstream by aiding grid integration and further decreasing emissions. In short, electric vehicles are still very much part of both the future of transportation and power generation.
One of the primary challenges facing mass integration of renewable energy sources into mainstream electricity supply is the issue of intermittency. Sources such as wind and solar photovoltaic (PV) are difficult to predict, especially with increasing prediction time horizons, making it challenging to plan supply in advance. There is also often little correlation between supply and demand. The wind may not blow and the sun may not shine when electricity is needed. The philosophy of current electricity system design and operation — ‘predict and provide’ — is achieved via the ability to ramp generation up or down to follow fluctuations in demand. This is achieved by making use of technology that allows for such adjustment, such as gas turbines, whereas with renewable sources such as wind and solar this rapid modification may not be possible.
Frequency regulation is an important electric grid requirement, and the introduction of renewable energy into the grid may, at worst, necessitate more use of fossil fuel reserves and risk subsequently increasing carbon emissions and operating costs. A further consideration that arises with an increasing renewable generation mix is curtailment. Curtailment, the practice of purposefully halting generation, is closely tied to the issue of intermittency. However, in this instance it may be that the wind blows or the sun shines when electricity is not needed. Curtailment often occurs as a result of other generation types such as nuclear or CHP (Combined Heat and Power) which carry a base load and may not be easily adjusted, or reserves, being online at that point in time, thereby reducing the additional amount of power that can be accepted into the grid. The level of curtailment therefore depends largely on electricity demand, other generator’s capacity and flexibility, and the correlation between renewable availability and demand.
Approaches to overcome these challenges include alternative generation, the use of storage, and demand response. All of these solutions may be in some form supported by grid-connected EVs, and so a brief exploration of how the mass acceptance and use of EVs might be an important part of a cleaner future electricity supply would serve.
As noted above, intermittency is a major challenge to widespread integration of renewable energy into the grid, often resulting in clean energy wastage not only because supply and demand don’t match, but also because adequate mass storage technology is not yet mainstream. Enter the electric vehicle, mostly charged overnight (or potentially whenever renewable energy is at its peak) and proven storage device.
One possibility currently under investigation is vehicle-to-grid (V2G) technology. This is a two-way interfacing technology conceptualised to supply electricity back to the grid via EV battery discharge. A joint programme between NRG Energy Inc. and the University of Delaware earlier this year successfully demonstrated the V2G concept. Though not yet commercial, key outcomes of such a pilot validate the possibility for EVs to provide frequency regulation and energy storage by leveraging many smaller power sources into one large resource. NRG Executive Vice President Denise Wilson summarised that “this demonstrates that (electric vehicles) can provide both mobility and stationary power while helping make the grid more resilient and ultimately generating revenue for electric vehicle owners.” Admittedly, there is some debate as to the ultimate merit of V2G technology. Turton & Moura’s (2008) global forecast model, run from 2000 to 2100, found that EVs and V2G technology enabled a 30 – 75% increase in installed renewable energy capacity. Contrarily, a literature review by Richardson (2013) concluded that though it may be possible in future, the role of V2G in renewable penetration is limited as a result of battery degradation and relatively high cost.
There are concerns that the addition of EVs and load to the grid will result in additional system costs, transmission losses and grid performance. Various literatures around this topic have suggested that network reinforcement and charge management strategies are critical to the success of mass deployment of EVs in future. Approaches such as smart charging may serve to overcome some such challenges by levelling load and using available (intermittent) energy. So while such concerns are certainly valid they should, rather than hindering the adoption of EVs, instead fuel further investigation into charging strategies and the role of smart grids and demand management.
There seems to be unanimous consensus that EVs in general will play a significant and positive role in future renewable energy rollouts and the grid. By supporting increased renewable energy adoption, EVs offer the opportunity to reduce carbon and pollutant emissions from transportation and power generation significantly, and to decrease dependence on fossil fuels. Understanding the possibilities as well as the limitations of EVs motivates further research to improve technology, drive infrastructural development, and inform policy so as to derive maximum benefit from such a specialized proposition.
Richard, DB 2013, ‘Electric vehicles and the electric grid: A review of modeling approaches, impacts, and renewable energy integration’, Renewable and Sustainable Energy Reviews, vol. 19, no. 1, pp. 247-254.
Turton, H and Moura, F 2008, ‘Vehicle-to-grid systems for sustainable development: An integrated energy analysis’, Technological Forecasting & Social Change, vol. 75, no. 10, pp. 91–108.
Genevieve Alberts is a passionate technologist with a solid technical foundation in mechanical and sustainable energy engineering and five years of career experience at a global automotive manufacturer. She is currently an MSc candidate at Imperial College London in Sustainable Energy Futures.
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