The report’s framing is grounded in hard lessons from Japan’s disaster history. The 2011 Great East Japan Earthquake left approximately 1.9 million fixed telephone lines and 29,000 mobile base stations out of operation, with power outages persisting for weeks. Moreover, fuel distribution for diesel generators, which form the backbone of most emergency power plans, remained compromised for two to three weeks across affected areas.

The structural problem with diesel generators is not just their severe fuel dependency, but also the maintenance regime they demand. Gasoline oxidizes and loses volatility within three to six months in storage, clogging carburetors and failing to start precisely the moment they are most needed. Engine oil oxidizes, starter batteries self-discharge, and humid environments accelerate corrosion. The report documents that without a rigorous maintenance and fuel-cycling regime, a significant portion of standby generators in Japan have failed to start during actual disasters.

Stationary PV systems, meanwhile, face a different but equally serious vulnerability: if the building hosting them is damaged or destroyed, the panels go with it. Grid-connected battery storage is useless when the grid is down. Battery electric vehicles (BEVs) can supply power through V2L or V2H interfaces, but once discharged they become inert — there is no way to replenish them in an isolated community with no functioning charging infrastructure.

This is where VIPV comes in. A solar electric vehicle generates electricity continuously from sunlight, regardless of whether any grid or fuel supply chain is intact. It can be driven to wherever power is needed. It can be repositioned to avoid shading. And when its battery is partially depleted, the sun recharges it.

The core of the report is a Monte Carlo simulation model developed to assess how many Solar Electric Vehicles (SEVs) a community would need to sustain critical emergency facilities for seven days following a major earthquake in a notional “PV City” with a 5 km radius.

The simulations incorporate not just technical variables like shading probability and seasonal irradiance, but social ones, such as how many vehicle owners will actually check their state of charge and voluntarily drive to an evacuation centre to donate surplus energy. The authors model two scenarios: a simple voluntary contribution model, and a more realistic “selfish power hoarding” model where individuals prioritise their own needs first.

Under the voluntary model, approximately 1,000 SEVs within a 5 km radius — around 13 per km² — is sufficient to sustain all critical temporary facilities for a seven-day isolation period. Even under the selfish hoarding model, simulations show that 450 or more SEVs within the same radius can power evacuation centers for seven days. In a city like Miyazaki, which the report uses as its reference city, this corresponds to just 1% SEV penetration in the vehicle fleet. That is a level reachable within the current decade under plausible EV adoption trajectories.

Two operational insights emerge from the modelling that have direct implications for policy. First, when SEV density is low, maximising contribution per vehicle matters most, so owners should be encouraged to donate larger fractions of their surplus. When density is high, distributing smaller contributions across more vehicles produces greater systemic stability than concentrating on a few large donors.

Second, and crucially: social incentive design is not optional. A system that relies on voluntary contribution will only function if the incentive structure is well-designed. The report is clear that “take what you can” approaches, without meaningful rewards for donors, will fail.

The report’s second pillar is a case study of a commercial VIPV product developed by IM Efficiency, a Dutch renewable energy startup. Their SolaronTop system converts standard trucks and trailers into mobile solar power units by integrating high-efficiency monocrystalline silicon panels across both the roof and sides of the vehicle, paired with lithium-ion storage, MPPT controllers, and standardised AC and DC output interfaces.

Performance data from a full 12-month monitoring period in Miyazaki’s climate (January to December 2024) shows the system generating 13,967 kWh annually, or an average of 38.3 kWh per day. Peak summer generation exceeded 45 kWh/day, while even in the worst winter month (December) the system produced 31 kWh/day. A notable finding is that the vertically-mounted side panels provided remarkably consistent generation of 18 to 23 kWh per day across all seasons, acting as a stable baseload while the roof panels varied more strongly with season.

The practical implications for emergency power are clear. The report maps typical daily energy requirements for disaster response applications in Japan: charging 2,000 smartphones requires 13 to 14 kWh/day; maintaining a temporary 4G/5G base station serving a 1 to 2 km radius requires 25 to 35 kWh/day; LED lighting for an evacuation centre uses 8 to 12 kWh/day; medical refrigeration and oxygen concentrators require another 8 to 12 kWh/day. A single SolaronTop truck running at typical spring or autumn output can cover most of these needs simultaneously. And two trucks can cover them comfortably, with margin to spare.

The report also provides a direct comparison against diesel generators across six criteria: deployment time, fuel dependency, operational cost, mobility, environmental impact, and maintenance requirements. On all six metrics, the VIPV system outperforms diesel, sometimes dramatically. Diesel scores 1 out of 10 on fuel dependency; SolaronTop scores 10. On environmental impact, diesel scores 1 (local air pollution, 65 to 85 dBA noise, approximately 65 to 80 kg of CO₂ per day of operation); SolaronTop scores 10, with zero operational emissions and near-silent running. Deployment time for diesel involves a 2 to 4 hour cycle of transport, setup, fuelling, and testing; SolaronTop requires 30 to 60 minutes to drive to the site, park, and connect.

The report is candid about what VIPV cannot do. Vehicles submerged by flooding, buried by landslides, or structurally damaged by building collapse are not available to provide emergency power. The contribution of SEVs to resilience is, in the authors’ own framing, “scenario-dependent.” They are particularly valuable in the scenario that is most common in Japan’s earthquake history: prolonged power outages where road access is partially or fully restored before grid power returns, allowing surviving vehicles to move and operate as mobile power sources during the critical early recovery phase.

The report is also careful to position VIPV as a complementary technology within a diversified resilience portfolio, not a wholesale replacement for diesel generators, stationary PV-battery systems, or portable solar kits. Each technology has its own strengths and weaknesses. VIPV’s unique combination of mobility, continuous generation, and zero fuel dependency gives it a specific niche, one that is more valuable than previously recognised.

The implications extend well beyond Japan. Any country with high earthquake, typhoon, or flood risk, isolated communities dependent on road-delivered fuel, or ambitious EV adoption targets has a reason to take this work seriously. The report suggests that governments developing EV incentive programmes should factor in disaster resilience value explicitly — both in the financial case for VIPV over standard BEVs, and in designing the emergency response frameworks that would activate SEV energy-sharing during crises.

For the automotive and energy industries, the message is equally direct. Commercial VIPV systems already meet the technical standards for real-world disaster deployment. The gap between research and implementation, the report concludes, is closing. The question is whether the policy, incentive, and community policies needed to make voluntary energy sharing work in practice can keep pace.

Author: Ignacio Landivar

This article is part of a monthly column by the IEA PVPS programme. It was contributed by IEA PVPS Task 17. The main goal of this working group is to accelerate and structure the deployment of PV in the transport sector.