A landmark along the Tokyo-Osaka railway, Sanyo&39's Solar Ark is 344 yards wide with an annual output of 530,000 kWh.

Struggling with a continuing nuclear crisis and strains on its power supplies, Japan is thinking of requiring that all new buildings, including homes, come equipped with rooftop solar panels by 2030, according to a recent Nikkei newspaper report.

Prime Minister Naoto Kan may announce the plan this week at a G8 summit in France, the business daily reported. Kan has pledged to review Japan's energy policy and increase renewable sources following the crisis at the Fukushima Daiichi nuclear plant, which was hit by the March 11 earthquake and tsunamis.

Kan hopes a solar-energy requirement for new buildings, along with technological innovation, would help reduce the cost of solar-power generation.

The government's current energy policy includes plans to increase nuclear energy to more than half of the total supply by 2030 as a means of reducing greenhouse gas emissions. Japan now gets about 30 percent of its electricity from nuclear sources.

Meanwhile, Tokyo Electric Power Company (Tepco) said today that three reactors at the Fukushima Daiichi plant probably suffered meltdowns early into the emergency, and their inner pressure vessels may have been breached. While Units 2 and 3 experienced partial meltdowns, Unit 1 was most severely affected.

An International Atomic Energy Agency team has also begun to look into how Japan has handled the worst nuclear accident in decades, which has left parts of the Tohoku region uninhabitable.

Tepco is trying to get the reactors under control by January. Its April electricity output was down 15 percent from a year earlier and shortages are expected to continue into the summer. Since western Japan runs on a different frequency, Tepco can't easily import large power supplies from other cities.

Japanese have been cooperating with emergency power conservation campaigns since the quake. As a result, they'll likely be less keen to use air conditioning, so this summer may be particularly hot and sticky in Tokyo.