What was studied? This report studies the possibilities and challenges of establishing a high-power charging system for battery-electric aircraft (EA) within an operational airport environment, with a particular focus on enabling short turnaround times (TAT). The study integrates perspectives from a diverse group of stakeholders, including an airport owner, a charging equipment solution provider, an aircraft developer, a research institute, an innovation arena, and a testbed operator. The aim is to significantly enhance the common understanding and identify viable pathways for the efficient and safe implementation of EA charging systems. The report addresses the three key subsystems (airport, charging equipment, and aircraft) detailing their specific requirements, including e.g. technical, operational, regulatory, and safety considerations, followed by identification and evaluation of possible power system topologies and conceptual charging solutions. Smart control of EA charging systems is explored and modeled to support adequate system design and optimal utilization of available power capacity. Additionally, the report presents measurement results from an operational airport to better understand the current electromagnetic compatibility (EMC) environment. It also includes a review of aviation cybersecurity and offers initial recommendations for future risk assessments to ensure an efficient and safe deployment of EA charging systems. 

The adoption of electric aircraft (EA) offers notable environmental advantages by mitigating greenhouse gas emissions and enhancing regional accessibility through reduced operational costs. Despite these benefits, EA faces significant challenges, partly in achieving practical operational ranges and developing robust airport charging infrastructures. The infrastructure challenge is compounded by the need for rapid turnaround times (TAT) in regional aviation, requiring high-power charging solutions above 1 MW. This paper explores various topologies for EA power supply systems and discusses pros and cons with those. Furthermore, an optimization model is developed using quadratic programming (QP) to allocate charging power among multiple aircraft, ensuring efficient and reliable operations under different system configurations. Simulations evaluate the performance of these configurations, highlighting the impact of grid power capacity, dimensioning of battery energy storage systems (BESS), and number of charging stands on system feasibility. The findings in this paper provide a foundational framework for designing airport infrastructures capable of supporting a growing demand for electric aviation, ensuring efficient power management and minimal operational disruptions. 

The adoption of electric aircraft (EA) offers notable environmental advantages by mitigating greenhouse gas emissions and enhancing regional accessibility through reduced operational costs. Despite these benefits, EA faces significant challenges, partly in achieving practical operational ranges and developing robust airport charging infrastructures. The infrastructure challenge is compounded by the need for rapid turnaround times (TAT) in regional aviation, requiring high-power charging solutions above 1 MW. This paper explores various topologies for EA power supply systems and discusses pros and cons with those. Furthermore, an optimization model is developed using quadratic programming (QP) to allocate charging power among multiple aircraft, ensuring efficient and reliable operations under different system configurations. Simulations evaluate the performance of these configurations, highlighting the impact of grid power capacity, dimensioning of battery energy storage systems (BESS), and number of charging stands on system feasibility. The findings in this paper provide a foundational framework for designing airport infrastructures capable of supporting a growing demand for electric aviation, ensuring efficient power management and minimal operational disruptions. 

This work compares and quantifies the annual losses for three battery system loss representations in a case study for a residential building with solar photovoltaic (PV). Two loss representations consider the varying operating conditions and use the measured performance of battery power electronic converters (PECs) but differ in using either a constant or current-dependent internal battery cell resistance. The third representation is load-independent and uses a (fixed) round trip efficiency. The work uses sub-hourly measurements of the load and PV profiles and includes the results from varying PV and battery size combinations. The results reveal an inadequacy of using a constant battery internal resistance and quantify the annual loss discrepancy to −38.6%, compared to a case with current-dependent internal resistance. The results also show the flaw of modelling the battery system’s efficiency with a fixed round trip efficiency, with loss discrepancy variation between −5 to 17% depending on the scenario. Furthermore, the necessity of accounting for the cell’s loss is highlighted, and its dependence on converter loading is quantified.

This work presents a comparison of alternating current (AC) and direct current (DC) distribution systems for a residential building equipped with solar photovoltaic (PV) generation and battery storage. Using measured PV and load data from a residential building in Sweden, the study evaluated the annual losses, PV utilization, and energy savings of the two topologies. The analysis considered the load-dependent efficiency characteristics of power electronic converters (PECs) and battery storage to account for variations in operating conditions. The results show that DC distribution, coupled with PV generation and battery storage, offered significant loss savings due to lower conversion losses than the AC case. Assuming fixed efficiency for conversion gave a 34% yearly loss discrepancy compared with the case of implementing load-dependent losses. The results also highlight the effect on annual system losses of adding PV and battery storage of varying sizes. A yearly loss reduction of 15.8% was achieved with DC operation for the studied residential building when adding PV and battery storage. Additionally, the analysis of daily and seasonal variations in performance revealed under what circumstances DC could outperform AC and how the magnitude of the savings could vary with time. © 2023 by the authors.

För att elnätet ska fungera måste frekvensen hållas inom snäva gränser och därför handlar Svenska Kraftnät upp olika typer av stödtjänster för frekvensreglering. De senaste åren har kostnaderna för dessa tjänster ökat kraftigt, bland annat till följd av en allt högre andel intermittent elproduktion. Behoven är prognostiserade att öka ytterligare under de kommande åren. Detta har skapat ett ökat intresse för batterier och deras möjligheter att stödja elnätet. Men batterier och tillhörande kraftelektronik är kostsamt. Samtidigt finns en stor och alltjämt växande batterikapacitet i landets elbilar och med hjälp av dubbelriktad laddning, så kallad vehicle-to-grid öppnas nya möjligheter att komma åt denna potential för att på ett mer resurseffektivt sätt balansera elnätet. Projektets övergripande mål har varit att utreda hur standardisering kan användas för att påskynda och öka användandet av elbilar som resurs för flexibilitetstjänster till elnätet. Bland annat har en fallstudie genomförts av Axess Logistics anläggning i Malmö hamn och möjligheterna för att deras långtidsparkerade elbilar ska kunna leverera frekvensreglering till elnätet har studerats. Resultaten visar på att studerade standarder i stort inte utgör ett direkt hinder för användandet av elbilar för frekvensreglering men att förändringar av exempelvis ISO15118 skulle kunna öka möjligheterna att använda elbilar för att leverera frekvensreglering. Till exempel genom införande av krav på mätnoggrannhet på aktiv effekt, förkortning av tillåtna svarstider, krav på lokal frekvensmätning med god noggrannhet. För långtidsparkerade bilar vore det framförallt värdefullt att arbeta fram, och i standard beskriva, en funktion där elbilens BMS kan uppmanas av EVSE att hålla batteriet i ett tillstånd där det kan användas för att snabbt svara på en begäran om i-/urladdning. Detta så att elbilen kan vara förberedd för frekvensreglering även om den för stunden inte aktivt laddar eller matar effekt till elnätet. Detta en åtgärd som skulle kunna ha stor positiv påverkan på möjligheterna för långtidsparkerade elbilar att leverera frekvensreglering. Exemplifierande användarcykler för långtidsparkerade bilar har studerats för FCR-N och FCR-D. Resultaten visar att den förväntade cyklingen skiljer stort mellan dessa olika frekvensregleringstjänster och antyder att valet av frekvensregleringstjänst behöver studeras utifrån både förväntad ekonomi och eventuellt batterislitage. Överslagsräkningar på eventuella intäkter från deltagande i frekvensreglering har genomförts och de preliminära resultaten visar att investering av dyrare laddinfrastruktur som klarar Vehicle-to-Grid skulle kunna återbetalas inom ett år med 2022 års nivåer av ersättning för frekvensreglering. I en framtid där nya elbilar antas ha stöd för Vehicle-to-Grid har potentialen för att använda långtidsparkerade elbilar på logistikanläggningar till frekvensreglering preliminärt bedömts ligga mellan 110 och 165 MW för svenska förhållanden. Detta motsvarar ca 5-8% av den nordiska FCR-marknaden. På sikt kan också långtidsparkerade bilar hos återförsäljare, flygplatser med mera att utgöra en betydande potential.

In this report, a framework was developed to assess the profits from participating in the different ancillary services for frequency regulation in Sweden. The framework considers forecasting errors on both production and prices, market clearing times and technical requirements of the difference ancillary services. The framework was applied to evaluate potential profits for a real wind power plant of 2 MW in SE3 in 2020 and 2021. The economic analysis points out to aFRR down as the most profitable market today with additional revenue of as much as 35% compared to day-ahead only in case of perfect production forecasts, and as much as 22 % with consideration of standard production forecast errors. It is also shown that developing bidding strategies based on price forecasting to act on several ancillary service market may increase the revenues by up to 70% compared to day-ahead only. Future work in the topic includes evaluating the profits in other price areas and evaluating different production and price forecast methodologies and their impact on the profits.

Frequency in power systems is a real-time information that shows the balance between generation and demand. Good system frequency observation is vital for system security and pro-tection. This paper analyses the system frequency response following disturbances and proposes a data-driven approach for predicting it by using machine learning techniques like Nonlinear Autoregressive (NAR) Neural Networks (NN) and Long Short Term Memory (LSTM) networks from simulated and measured Phasor Measurement Unit (PMU) data. The proposed method uses a horizon-window that reconstructs the frequency input time-series data in order to predict the frequency features such as Nadir. Simulated scenarios are based on the gradual inertia reduction by including non-synchronous generation into the Nordic 32 test system, whereas the PMU collected data is taken from different locations in the Nordic Power System (NPS). Several horizon-windows are experimented in order to observe an adequate margin of prediction. Scenarios considering noisy signals are also evaluated in order to provide a robustness index of predictability. Results show the proper performance of the method and the adequate level of prediction based on the Root Mean Squared Error (RMSE) index. © 2021 by the authors.