In 1824, French engineer and physicist Sadi Carnot published a book, Reflections on the Motive Power of Fire and on Machines Fitted to Develop that Power. In this book, Carnot formulated the theory of the conversion of heat into work. This would soon prove valuable, as the world was on the cusp of the industrial revolution. Within a few years, Carnot's theories were put into practice on an enormous scale, using coal as the "power of fire" to boil water and make steam, the "motive" force for spinning turbines. By the 1880s, power plants were generating electricity in this manner to light street lamps and run factories.
Nearly two centuries later, New York power plants still use Carnot's method (although with different fuels, among them nuclear, natural gas, coal, and oil) to produce most of their electricity. However, there are problems with this model from an efficiency perspective. All fuel has an energy content which is used in the generation process. But of the energy generated, two thirds is lost, either during the conversion process (conversion loss), or during the course of transmission from power plant to customer (line loss). This means that electricity generation is the largest consumer of energy statewide. And, while some energy loss is unavoidable, you don't have to be an electrical engineer to see that this is wasteful!
Every time we put a photovoltaic (solar electric) power plant on a customer’s roof, we solve both the conversion loss problem and the line loss problem. Rooftop solar electric systems bypass losses from heat or friction, from stepping power up and down, and from shipping it miles away to customers. Photovoltaic systems have no moving parts and make no steam. Instead, photovoltaic modules convert photons, the particles of energy in sunlight, into electrons, the particles which power our electrical system. At our latitude here in Westchester County, every square foot of photovoltaic module can produce about 1,200 kilowatt-hours a year (100 kWh per month). What exactly does that mean? Check our next post to find out!