The heat source for this experiment is a compost pile (1 cubic meter), I know that the inside of the pile will reach approximately 50C for 2 weeks or so. Right now it's winter so the temperature will stay around 0C (average). The thermal conductivity of compost can vary greatly but in this case an average that would apply is 0.3 W/m. I'm guessing here but I believe Fourier's Law could apply and I could use that to solve how much energy is lost over the course of two weeks which would also give me how much energy is produced since the energy is constant. Again simplifying I'll say that the inner half of the sphere is 50C and the outer half acts only as insulation so Q = -kA(dT/dx) Q=Watts, k=thermal conductivity, A=heat transfer area, dT=temperature difference, dx=thickness of barrier Q = -0.3 * 3.14 (50 / 0.5) Q = 94.2 W * 1,209,600 (seconds in 2 weeks) 113,944,320 Watts over the course of 2 weeks Is that the proper way to solve this type problem?