Sun Tower is a space based solar energy collection system designed to beam microwave energy to a energy collection antenna on the earth for further distribution to the power infrastructure.
The proposed Sun Tower will require an efficient means for power transmission. This affects the Power Management And Distribution (PMAD) of the overall system and the individual PMAD elements distributed through the Sun Tower system architecture.
As proposed, the Sun Tower would require a PMAD unit at each of the 340 arrays to generate the desired transmission voltage and subsequently down convert the required voltages of the planar microwave array. The power will be approximately 1.44GW/340 or 4.24MW per channel.
To reduce the PMAD mass and size at the “bottom end” antenna array, a concept was developed using AC at approximately 10KHz. The use of AC will allow reduction in the bottom transformer size and simplify power processing. Conventional DC transmission techniques use SCRs (Silicon Controlled Rectifiers) to chop and reconstruct a 60Hz sinewave for transformer reduction to distribution voltages from about 12KV down to 440 for local distribution. The issue for Sun Tower will be the weight of the lower power processing electronics. Using The DC approach we need a transformer at 60 Hz. With AC we can effectively use a much lighter transformer rated at 10KHz.
The power distribution at the antenna was forecast at 80VDC. A power plane for the 80 volt interconnect will be used across the 300meter antenna back. This will have many benefits. The impedance of the plane will be very low for all users and create a low EMI environment. This will require the MMIC designers to incorporate voltage regulation to control the RF beam pattern.
This paper will show the design process and illustrate the system trades involved in building a large PMAD system.
