Low temperature heat sources are available anywhere that there is a temperature difference of about 30C or 40F between the heat source and the heat sink. Examples of low temperature heat sources are as follows: a) 30F Sea water {heat sink} and 70F {heat source} temperatures. b) 30F Sea water {heat source} and -10F {heat sink} temperatures. c) Geothermal temperature of 50F {heat source} and 10F {heat sink} temperatures. d) Geothermal temperature of 50F {heat sink} and 90F {heat source} temperatures. It is easy to see that Solar thermal can provide the heat source almost anywhere. Even starting a small fire will provide the energy for the heat source. Note that energy for the Lurtz Cycle comes from both gravity and from the heat source. In addition, think how easy it is to store “low temperature heat”. A foam insulated “swimming pool” size heat source at 90F [with a geothermal heat sink] can store heat for days and can produce 24kwh of electricity per day.