People eat, drink and merrily breathe air. It is sunshine that keeps us alive by providing the food, water and oxygen in the air we breathe.
We like to eat and consume about 1 million calories a year. This requires about 10,000 square feet of sunshine. (NOTE this does not include: the range land for chickens and cows; the oil energy for industrial agriculture; my energy if I grow all my own food; or the sun hitting fallow land between crops.)
Roughly an equal area is required to provide the oxygen in the air we breathe, 10,000 more square feet. So every adult human on the planet uses at least 20,000 square feet of sunshine.
Water is interesting because it takes about 1 gallon to keep a human alive. It requires about 10 square feet of sunshine to provide a daily gallon of fresh water. We use over 10 gallons of water directly for washing and cooking and flushing. However, considering the industrial, agricultural, and cooling water used for each of us in our consumer culture, we use over 1000 gallons of water daily, another 10,000 square feet of sunshine.
That’s a rough total of 30,000 square feet of sunshine per American. At our house my wife and I use sunshine for passive solar heat and photovoltaic (solar panel) electricity. (Note we also use about a cord and a half of fire wood we cut locally. It takes about 30,000 square feet of sunshine in Troy NY for each of us to grow that wood sustainably.) We together have 240 square feet of passive solar vertical south windows providing most of our winter heat. We have 460 square feet of photovoltaic panels that provide more electricity than we use. For more information on the house see my earlier blog and video.
We in the US live on 20,000 sq ft of sunshine just like every one of the billions of adult humans on the planet. However, we in the US use 10s of thousands of square feet more of sunshine plus 100s of millions of BTUs of fossil fuels.
Yes, I use fossil fuels too, mostly for transportation. Our house is mostly heated by passive solar and generates more solar electricity than it uses with just 700 square feet total of sunshine collection, for my wife and I, here in sunny (?) Troy, NY.
David Borton is an RPI Physics Professor and Solar Advocate. He may be reached through Member email and comments to this blog.