This paper describes an instrument devised by Joule in 1863 to detect the energy of moonlight. It is extraordinarily sensitive to heat and must convert heat into mechanical energy with high efficiency. But since the temperature rise caused by moonlight is only 10-4°F, the Carnot theorem would give a maximum efficiency of 10-6.
JOULE'S THERMOSCOPE SHOWS
THAT THE CARNOT
EFFICIENCY LIMIT, THE MOST COMMON EXPRESSION OF
THE SECOND LAW OF THERMODYNAMICS, IS WRONG
The thermoscope uses convection currents and involves an energy cycle at constant volume. These features form the basis of proposals I have made for the efficient conversion of solar energy into electricity that were placed on this website in March 2002, September 2002 and March 2003. Indeed Joule's thermoscope is identical to Figure 3 in the Simple Solar Engine (March 2003). It is the author's view that heat from fossil fuels and from solar energy can be converted into mechanical energy or electricity with an efficiency of up to 100% using energy cycles at constant volume.