New York City provides some challenges to the use of solar power that other cities do not present.

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It will let wind and solar power be transmitted to the cities, and smooth out peaks and troughs in demand for example by feeding power to the batteries of parked electric cars at night, and sucking it out of them during the day, if their owners agree.

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Other Chinese cities, including Dezhou in Shandong Province, have embraced solar water heaters as well.

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This week Korean automaker Hyundai unveiled a multi-rotor flying electric car for congested cities and SolarWorld and PC-Aero announced plans to launch two new solar-powered electric airplanes at an air show in Germany.

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NRG, a power plant developer who has invested in some of the largest solar power projects in the country, decided to give SCS a try as it sought to expand its focus to include not just mega solar farms in remote locations but also smaller projects on commercial properties close to or within cities.

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Rebates: Some states, and even cities and utilities, offer rebates that cover part of the purchase price of a solar-energy system installation.

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