Future national electricity, heating, cooling and transport systems need to reach zero emissions. Significant numbers of back-up power plants as well as large-scale energy storage capacity are required to guarantee the reliability of energy supply in 100 percent renewable energy systems. Electricity can be partially converted into hydrogen, which can be transported via pipelines, stored in large quantities in underground salt caverns to overcome seasonal effects and used as electricity storage or as a clean fuel for transport. The question addressed in this paper is how parked and grid-connected hydrogen-fueled Fuel Cell Electric Vehicles might balance 100 per cent renewable electricity, heating, cooling and transport systems at the national level in Denmark, Germany, Great Britain, France and Spain? Five national electricity, heating, cooling and transport systems are modeled for the year 2050 for the five countries, assuming only 50 percent of the passenger cars to be grid-connected Fuel Cell Electric Vehicles, the remaining Battery Electric Vehicles. The grid-connected Fuel Cell Electric Vehicle fleet can always balance the energy systems and their usage is low, having load factors of 2.1–5.5 percent, corresponding to an average use of 190–480 h per car, per year. At peak times, occurring only a few hours per year, 26 to 43 percent of the grid-connected Fuel Cell Electric Vehicle are required and in particular for energy systems with high shares of solar energy, such as Spain, balancing by grid-connected Fuel Cell Electric Vehicles is mainly required during the night, which matches favorably with driving usage.

The world's future energy supply will include intermittent renewable sources, such as solar and wind power. To guarantee reliability of supply, fast-reacting, dispatchable and renewable back-up power plants are required. One promising alternative is parked and grid-connected hydrogen-powered fuel cell electric vehicles (FCEVs) in "Vehicle-to-Grid" systems. We modified a commercial FCEV and installed an external 9.5 kW three-phase alternating current (AC) grid connection. Our experimental verification of this set-up shows that FCEVs can be used for mobility as well as generating power when parked. Our experimental results demonstrate that present-day grid-connected FCEVs can respond to high load gradients in the range of -760 % s^-1 to + 730 % s^-1, due to the parallel connection of the high voltage battery and the fuel cell stack. Virtual power plants composed of multiple grid-connected FCEVs could perform higher power gradients than existing fast-reacting thermal power plants with typical power gradients of 1.67 % s^-1. Hydrogen consumption in 9.5 kW AC grid-connected mode was 0.55 kg h^-1, resulting in a Tank-To-Grid-AC efficiency of 43% on a higher heating value basis (51 % on a lower heating value basis). Direct current to alternating current efficiency was 95 %.

This paper presents the results of a demonstration project, including building-integrated photovoltaic (BIPV) solar panels, a residential building and a hydrogen fuel cell electric vehicle (FCEV) for combined mobility and power generation, aiming to achieve a net zero-energy residential building target. The experiment was conducted as part of the Car as Power Plant project at The Green Village in the Netherlands. The main objective was to assess the end-user's potential of implementing FCEVs in vehicle-to-grid operation (FCEV2G) to act as a local energy source. FCEV2G field test performance with a Hyundai ix35 FCEV are presented. The car was adapted using a power output socket capable of delivering up to 10 kW direct current (DC) to the alternating current (AC) national grid when parked, via an off-board (grid-tie) inverter. A Tank-To-AC-Grid efficiency (analogous to Tank-To-Wheel efficiency when driving) of 44% (measured on a Higher Heating Value basis) was obtained when the car was operating in vehicle-to-grid (V2G) mode at the maximum power output. By collecting and analysing real data on the FCEV power production in V2G mode, and on BIPV production and household consumption, two different operating modes for the FCEV offering balanced services to a residential microgrid were identified, namely fixed power output and load following. Based on the data collected, one-year simulations of a microgrid consisting of 10 all-electric dwellings and 5 cars with the different FCEV2G modes of operation were performed. Simulation results were evaluated on the factors of autonomy, self-consumption of locally produced energy and net-energy consumption by implementing different energy indicators. The results show that utilizing an FCEV working in V2G mode can reduce the annual imported electricity from the grid by approximately 71% over one year, and aiding the buildings in the microgrid to achieve a net zero-energy building target. Furthermore, the simulation results show that utilizing the FCEV2G setup in both modes analysed, could be economically beneficial for the end-user if hydrogen prices at the pump fall below 8.24 €/kg.

In a 2050 fully renewable national electricity, heating and road transport system primary energy supply comes from non-dispatchable power generation such as solar and wind energy. Both negative and positive dispatchable balancing power plants need to balance the system. This work investigates whether parked and grid connected (Vehicle-to-Grid) Fuel Cell Electric Vehicles (FCEVs) fueled with pure hydrogen can replace positive dispatchable balancing power plants. These power plants, often gas turbine based, are likely to operate at low capacity factors in future. A simulation for a 2050 scenario is based on German 2015 renewable electricity data and assumes a passenger car mix of 40% FCEVs and 60% Battery Electric Vehicles. On average 0.9 million FCEVs with Vehicle-to-Grid (V2G) output of 10 kWe would be required during evening and night time and approximately 6 million during the annual peak shortage hour to balance the system at all times. These numbers represent respectively 2% and 14% of the total 2015 German passenger car stock and have the potential to replace all positive dispatchable power plants in future.

How can we analyse fuel cell stack voltage degradation with transient phenomena and are existing durability indicators as distance driven or operating hours still relevant in commercial FCEVs, used for driving and vehicle-to-grid (V2G) purposes? The mean stack voltage drop is measured over fuel cell operating time and produced electricity in 4 commercial Hyundai ix35 FCEVs. The experiments show that a durability indicator expressed solely in operating hours, distance or produced energy is not relevant for combined driving, V2G and idling load profiles. An indicator consisting of several usage parameters is recommended.

This article presents a detailed thermodynamic case study based on the Willem-Alexander Centrale (WAC) power plant in the Netherlands towards retrofitting SOFCs in existing IGCC power plants with a focus on near future implementation. Two systems with high percentage (up to 70%) biomass co-gasification (based on previously validated steady state models) are discussed: (I) a SOFC retrofitted IGCC system with partial oxy-fuel combustion CO₂ capture (II) a redesigned highly efficient integrated gasification fuel cell (IGFC) system with full oxy-fuel CO₂ capture. It is concluded that existing IGCC power plants could be operated without major plant modifications and relatively high electrical efficiencies of more than 40% (LHV) by retrofitting SOFCs and partial oxy-combustion CO₂ capture. In order to apply full scale CO₂ capture, major process modification and redesign needs to be carried out, particularly in the gas turbine unit and heat recovery steam generator (HRSG). A detailed exergy analysis has also been presented for both the systems indicating significant efficiency improvement with the utilization of SOFCs. Additional discussions have also been presented on carbon deposition in SOFCs and biomass CO₂ neutrality. It is suggested that scaling up of the SOFC stack module be carried out gradually, synchronous with latest technology development. The thermodynamic analysis and results presented in this article are also helpful to further evaluate design challenges in retrofitted IGCC power plant systems for near future implementation, gas turbine part load behaviour, to devise appropriate engineering solutions and for techno-economic evaluations.