B is 99% false. Same thinking as above.
C is about 60% true. Solar is not economical for many homes, and wind even less so due to geography.
D is 90% true. When heating, cooling, and cooking needs are taken into account, solar does not supply enough power. When heat comes from somewhere else like a wood stove or natural gas, solar can supply a home’s needs. There’s still the economic issue. And the term "efficient" is subjective.
References :
Here are some good tutorials on how to do this and also understand the variability issue:
http://energy.wesrch.com/pdfTR1L02KEKX141
http://energy.wesrch.com/pdfTR1YL6V1ZIPVC
References :
http://energy.wesrch.com/pdfTR1L02KEKX141
http://energy.wesrch.com/pdfTR1YL6V1ZIPVC
B is obviously not true
C and D have some truth in them. Terms like efficient and expensive are relative, so depending on how you interpret these terms, you could see either C or D or both as true.
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References :
wind turbines are expensive to install but once up, not much maintanence is needed, checked up maybe every few years.. the energy can be stored in batteries when there is no wind present.
so, i guess its def not answer B and C.
edit: wind and sunlight is free so it isnt expensive to *use*
References :