Abstract: A thermal energy storage and transfer system includes solar energy collector means disposed to receive incident solar energy, thermal energy exchange means disposed in a utilization area, three water storage tanks, one of which is at least three times larger than the other two storage tanks. Water is selectively circulated through a first circulation loop between the solar collector and one small tank for transferring solar energy from the collector; through a second circulation loop between the second small tank and the utilization area; and through a third circulation loop between the large tank and the two smaller tanks. A heat pump is coupled between the two smaller storage tanks for transferring thermal energy between those two tanks.

Abstract: A temperature differential measuring circuit includes first and second temperature sensitive transducers disposed in corresponding first and second legs of a bridge circuit. Disposed in third and fourth legs of the bridge circuits are fixed resistors. An operational amplifier has its input terminals connected to the output terminals of the bridge circuit with its output terminal connected to one of the fixed resistors so that that fixed resistor is in feedback relation between the input and output of the amplifier. The transfer function of this bridge circuit is less temperature dependent than the transfer functions of conventional voltage bridge circuits.