Your Questions About Sustainable Energy Technologies

What kind of science and technology do you think is needed for realizing a more prosperous & sustainable world?

by prosperous i mean happiness ( including wealth but not only limited to wealth)

by sustainable i am talking in enviornment terms and development which can be sustained for future generations also.

Why is it important that people conserve energy?

Why is it important that people conserve energy?
Okay, I have my science homework its a question and the question asks: there is a limited amount of energy available on Earth. Why is it important that people conserve energy??
Please help me!!!!