Now that's a lot of Work.

James Prescott Joules found the specific heat of water using mechanical energy. In 1845, he used falling weights to churn water where the mechanical energy lost by the weights was equated to the heat gained by the water.^[1] From these experiments he estimated the mechanical equivalent of heat to be 838 ft•lbf of work to raise the temperature of a pound of water by one degree Fahrenheit.^[1]

Let us relate this experiment to modern day life. How much mechanical energy is needed to brew a 64 oz pot of coffee? Assuming that the tap water is 60 ◦ F the temperature needed to brew great coffee is between 190 ◦ F to 200 ◦ F. Using 190 ◦ F, the change in temperature is 130 ◦ F. The mechanical energy needed to raise the temperature of 4 pounds of water to 190 ◦ F is 435 ,760 ft•lbf .

When I took thermodynamics, I was astounded to learn the amount of work needed to heat water. However, despite the calculations I still took energy for granted. The concepts of thermodynamic did not begin to sink in until I embarked on my harvesting energy project.

Living in Seattle, I thought I would use rain water falling from the roof to harvest energy. From my calculations, during the rainiest months, the most energy harvested would be 1000 watts. My average daily usage of electricity at home is 18 kWhrs a day. The 1 kW harvested in a month is negligible.

The typical household uses 20 to 45 kWhrs a day and most people are at work for eight hours a day. However, houses can be built to optimize energy using 800 watts a day.^[2] If our houses were living organisms they would have become extinct long ago.

Nature does not waste. For example, aphids excrete an excess of glucose that they are unable to digest from plant leaves and this excess is ingested by insects and bats. The challenge for me is to learn from nature and devise technological symbiotic relationships to increase efficiency and decrease consumption. Stay tune.

1. Poynting, J.H. (2007). A Text Book of Physics. READ BOOKS. ISBN 1406773166
2. http://www.treehugger.com/files/2006/07/300whr_a_day_th_1.php