A group of scientists from the Arctic University of Norway has demonstrated the theoretical technical feasibility of a nationwide energy system relying purely on distributed solar and electric vehicles (EVs) equipped with vehicle-to-grid (V2G) technology.
V2G technology is used to feed the energy stored in EV batteries back into national grids, which can help stabilize power supply during high-demand periods. In order to make this technology have a sufficient impact on grid operations, however, large deployment volumes are necessary.
With this in mind, the Norwegian team decided to undertake what they called a “conceptual exercise” and assumed that the entire energy demand of a sunny country, such as Spain, could be completely covered by distributed solar generation, and that the nation's entire fleet of 29.4 million road-going vehicles could, theoretically, switch to electric vehicle technology. “We chose Spain as a case study mainly because of its location in southern Europe, with relatively large amounts of solar radiation all year round,” the academics explained. “At higher latitudes, the sun-hours during winter months drastically decrease, making a pure PV-EV system unrealistic.”
Working with a Matlab-based model, they calculated the state of the charge (SOC) for the aggregated EV fleet with an hourly temporal resolution. The proposed system works as follows: if the solar power production is higher than the load, surplus is stored in EV batteries; if these batteries have reached a 100% SOC and PV generation is still higher than the load, the surplus is lost; if PV generation is lower than the load, the grid takes power from the EV batteries until a minimum of 10% SOC is reached; if both PV and the EV batteries are unable to supply the load, the result is what the scientists called a “failure hour.”
They also assumed that all the EVs are equipped with V2G, have a battery capacity of 100 kWh, and are connected to the power network when parked. At night, when PV is not operating, the country's power system is depending entirely on the electricity stored in the EV batteries. Through the modeling, the research group found that 3.45 billion m2 of PV systems would be necessary to build a 100% self-reliant energy system.
“The visionary conceptual study presented here shows that it is indeed theoretically possible to power a complete country like Spain solely by the use of photovoltaics (PV), and to balance the intermittency solely by using the battery capacity of a fully electric transport system and V2G technology,” the researchers concluded, noting that even with 2 billion m2 of PV systems, 79% self-reliance would be possible.
They also warned, however, that their findings should be taken as the basis for future research on energy systems based solely on renewable energy, adding that their work was based on three kinds of assumptions: technically unrealistic; technically feasible but not likely to occur; and technically feasible and likely to occur.
The details of the modeling can be found in the paper The pure PV-EV energy system – A conceptual study of a nationwide energy system based solely on photovoltaics and electric vehicles, published in Smart Energy.
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