What are the three challenges to solar energy?

Solar space heating units tend to be less expensive than solar water heating units because

One of the most common sources of phosphate pollution that has led to eutrophication has resulted from the use of

Which of the following are used by individual farmers to generate biogas for their own use?

According to the Environmental Protection Agency, the greatest current water-pollution challenge in the United States is

Except for photovoltaic cells, all electricity production requires the use of which one of the following?

Given the problems of inconsistent winds, the best place to position new wind turbines would be

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Carbon reduction and capture and storage systems are currently

Which of the following is true regarding the greenhouse effect and climate change?