PNNL researchers are studying the effects of innovative transport systems on the power grid
Imagine stepping into a capsule, suitcase in hand, and hurtling through tubes from city to city at a speed of 760 mph. Imagine vendors using these trays to move goods to grocery stores much faster than they can be delivered by truck.
You – or these goods – are traveling through another dimension, one might think. However, this is not the case The twilight zone.
Instead, it's an emerging mode of transport called Hyperloop. Before introducing such an innovative transportation system, however, Hyperloop developers, municipalities and network operators must first understand how this will affect the power grid.
A research team from the Pacific Northwest National Laboratory (PNNL) A “worst case scenario” assessment was recently carried out to determine the impact of Hyperloop systems on the network the results published in IEEE transactions on power systems. Their study also helped inform a report published by the US Department of Energy in February 2021 Office for Energy Efficiency and Renewable Energiesthat supports the evaluation.
Preparation for modeling the hyperloop
To conduct their assessment, the PNNL team modeled four conceptual hyperloop systems ranging from large metropolitan areas to smaller urban locations and stretching from the west coast to the eastern part of the country.
Systems in California, Colorado, and Ohio provided transportation between cities, while a second California system represented urban transportation – a station near the San Francisco airport with a location near the Golden Gate Bridge.
The sites were assumed to be less than 10 kilometers from a substation with a voltage of at least 138 kV – a standard high voltage used to transmit large amounts of electricity. PNNL's analysis focused on the power to propel and brake the pod, maintain a vacuum in the pipes, levitate the pod, and the station and pod electrical loads. The simulations assumed that industry-standard network tools were present and typical scenarios for electricity loads in summer were used to represent a higher load on the grid.
"We turned our attention to the worst-case scenario – the heavy-duty Hyperloop pods that make up high-acceleration freight traffic of up to 760 mph, with the network simulations showing the heaviest load profiles," he said Ahmad Tbaileh, the PNNL electrical engineer who led the study.
In the Intercity study, the team found that accelerating and braking through cargo loads resulted in flicker or "bumps" – sudden and noticeable changes in voltage levels due to fluctuations in power demand.
These surges can cause disruptions in the network – in the worst case, a power failure. In Colorado, the scenario with the greatest impact on the electrical load and the weakest transmission grid, the grid can flicker. The evaluation also found that some substations used at the smaller site – Colorado – exceeded guidelines to prevent flicker and would require mitigation equipment such as that required for energy storage in order for the Hyperloop system to be integrated into the grid.
In the intra-city study, the effects were small compared to the inter-city studies, mainly due to smaller pod sizes, less acceleration, and fewer stops and starts.
The team also found that due to large voltage drops at lower voltage substations, intercity hyperloop systems are likely to require connections to substations with voltage levels of 230 kV or higher compared to the standard of 138 kV.
The simulations also showed that the western network, which covers California and Colorado, was more disrupted than the eastern network connection, which covers Ohio, from the rapid changes in electrical load triggered by a hyperloop system. This finding suggested that the western grid may have less responsiveness to absorb shocks from hyperloop current spikes.
"We turned our attention to the worst-case scenario – the heavy Hyperloop pods that make up the high-acceleration freight traffic of up to 760 mph, with the network simulations showing the heaviest load profiles." – Ahmad Tbaileh, electrical engineer
Strengthen the grid
"Ultimately, we found that the continuous pulses or bumps in the intercity hyperloop system caused by freight traffic are large enough to likely cause disruption to the network," said Tbaileh. "These disruptions can lead to violations of the industry planning guidelines used by network operators for power flicker and fluctuations."
Furthermore, the impulses and shocks would put a considerable strain on the power plants that absorb these sharp impulses. The requirements for the maintenance of power plants would most likely have to be increased if the impulses or shocks are not mitigated by energy storage or other buffer technologies in order to smooth out the sharp increase in the electrical load. These compensation technologies are most likely indispensable in conditions when the power transmission network is under high load conditions.