In 1824, young 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 that short book (only 65 pages!), Carnot formulated the theory of the conversion of heat into work.
At that moment in human history, the industrial revolution was about to unfold. Within a few years, coal became the fuel of choice for making steam. Steam became the ‘motive’ force for turning wheels.
By the 1880s, power plants all over the industrializing world began to make electricity by burning something to boil water to spin turbines past magnets to light street lamps and run factories.
Nearly two centuries after Carnot wrote his book, New York still uses boiled water to produce most of the state’s electricity from the following fuels, in descending order, nuclear, natural gas, coal, and oil. Hydropower, of course, uses falling not heated water to turn turbines.
From an efficiency (and resource conservation) perspective, the problem with using steam in centralized power plants is simple. We lose two-thirds of the fuel’s original energy content during electricity generation due to energy conversion losses itself (such as lost heat) or transmission losses during delivery to the customer.
Only one-third of the energy in the fuel that we use generating electricity becomes power we can sell to end-users.
That lack of efficiency means that electricity generation is the state’s single largest consumer of energy.
Every time we put a photovoltaic (solar electric) power plant on the customer’s roof, we solve both the energy conversion loss problem and the line loss problem.
Rooftop solar electric systems bypass any losses from heat or friction or from stepping power up and down or shipping it miles away.
Photovoltaic systems have no moving parts and make no steam. Instead, photovoltaic modules convert the photons in sunlight directly into electrons by means of the dielectric sandwich inside.
At our latitude here in Westchester County, every square foot of a photovoltaic module can produce about 1,200 kilowatt-hours a year (100 kWh per month).
Caption for the attached energy flow chart:
Of total energy devoted to electricity generation (1,526 TBtu) in New York, only one-third (478 TBtu) reaches end-users, while two-thirds (1,048 TBtu) is lost through conversion and line losses. New York’s conversion losses are typical and comparable to the national pattern. (Note: TBtu = trillion British thermal units) [Source: NYSERDA Patterns and Trends: New York State Energy Profiles: 1995-2009 (January 2011)]