The paper investigates how different battery discharging cost calculation methods affect the contribution of plug- in electric vehicles to balance fluctuating generation. For the investigation an agent-based approach using the PowerACE model is applied. In addition to very valuable research focusing on solving the unit commitment problem including uncertainty on forecaster errors [5] or energy planning tools [21] combined with detailed dynamic system simulations [22] the used approach allows to investigate the perspective of single vehicles including the aging of associated batteries. The results indicate that depth of discharge-based discharging cost calculation results in a more restrictive discharging behavior compared to energy throughput-based discharging costs. Studies trading vehicle batteries as one large battery therefore are likely to overestimate the vehicle-to-grid performance. Especially, the amount of energy fed back into the grid is significantly lower if depth of discharge-based aging is considered. In terms of balancing fluctuating generations results are within the same range but sensitivities to battery size and costs are higher in case of the depth of discharge-based method. It should also be mentioned that depth of discharge-based ageing cost calculation results in a higher tendency of fully charged batteries which leads to battery wear out in terms of battery calendar life time. Comparing vehicle-to-grid with load shifting only indicates that the additional V2G benefits are relatively low. This is especially true for the consumption of surplus generation from fluctuating sources. In contrast to this, analyzing the reduction in hourly ramp rates shows that vehicle-to-grid highly contributes to balance fluctuating generation. The increase of the residual load change rate due to renewable generation units is one major challenge for system security. Here, vehicle-to-grid is able to realize significant improvements. In conclusion, analyzing not only surplus generation but also residual load ramping shows that vehicle-to-grid results in an additional contribution balancing fluctuating generation. For both charging strategies, load shifting only and vehicle-to-grid, expected revenues from day-ahead electricity markets are less than 200 euros per year compared to uncontrolled charging after the last trip. Coherence between a higher share of fluctuating generation in combination with rising prices for primary energy carriers and higher revenues from smart charging did not occur. The merit-order-effect results in increasing price spreads for specific situations when high and low residual loads occur during one day. In terms of smart charging revenues these high price spreads are compensated by low spreads occurring during long base-load periods. Here, prices spreads are only between marginal costs of different power plants in the base-load segment and therefore relatively low. Hence, realizing smart charging business cases will be very challenging even if prices for primary energy carrier are rising and high fluctuating generation output reduces spot market prices. Therefore, it remains particularly important to realize smart charging at low costs e.g. while using available components in vehicles as well as onboard metering.


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    Title :

    The contribution of vehicle-to-grid to balance fluctuating generation: comparing different battery ageing approaches


    Contributors:


    Publication date :

    2013


    Size :

    20 Seiten, Bilder, Tabellen, 22 Quellen


    Type of media :

    Report


    Type of material :

    Print


    Language :

    English