Saul Griffith is an inventor and entrepreneur. He did his PhD at MIT in programmable matter, exploring the relationship between bits and atoms, or information and materials. Since leaving MIT, he has co-founded a number of technology companies including www.optiopia.com, www.squid-labs.com, www.instructables.com, www.potenco.com, and www.makanipower.com.
How do we measure energy and power?
If you would like to quantitatively understand the relationship between your lifestyle, global energy use, and climate change, you need to establish the language with which you can translate between these things. There are many different ways we use energy, many different ways we produce energy, and many different consequences environmentally. Power and energy are being measured around us all of the time. You get your electricity bill in kilowatt hours (kWh), your gas bill in Therms or British Thermal Units (BTUs), your car's performance is measured in horsepower, and your lightbulbs are rated in watts. To compare these things you need a common set of units, and we've already encountered 4 different units (kWh, BTU, Hp, W), and two different concepts - energy and power -- and we've only just started.
The first problem with comparing these things is that some of them (BTUs and kWh) are measures of energy consumed, and some of them (horsepower and watts) are measures of power. To add to this confusion, some of them are measures of primary energy (barrels of oil equivalent, or metric tons of coal), some are measures of net electrical power at your outlet (W), some are measures of thermal energy or heat, and some are measures of net mechanical power (Hp at the wheels of your car). To wade your way through all of this, you need an intuition for the difference between energy, and power. Energy can actually be an abstract concept, while people often have a more intuitive understanding of power-- "my car has 200 horsepower!˝
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