James Webb Space Telescope & Off Grid Power

Image: NASA

Is there a connection between a space telescope and off grid electric power? Yes, indeed there is. Since 1958 NASA has powered many satellites, including the international space station, with photovoltaic (PV) solar panels. The James Webb space telescope has PV solar power array to charge its battery and run its scientific loads. It’s hard to get farther off grid than space.

NASA’s use of PV solar power went a long way toward supporting the development of PV power, eventually making it possible for use in off grid systems on earth. For the first couple of decades of earthbound PV solar power, the only uses were exclusively off grid, grid connected solar system only coming on line in the late 1990’s, and not to any large extent until years later.

The James Webb space telescope has a 2kW PV solar power array, which was carefully sized to reliably power its loads for its intended lifetime. The designers have sized this to be adequate for the needed power, but would not oversize the solar with every ounce of weight in a satellite being critical. With a residential or industrial solar system on earth, one would design it to meet the expected loads, but not too oversized adding unnecessary cost to the customer. On the other hand, sizing too small is an even more serious issue, causing curtailment of power during poor weather, and often a dissatisfied customer. For ground based systems that are subject to night and day, seasons, and weather, the design is further complicated with the need for an adequately sized battery bank. A balance needs to be found between cost and function when sizing the solar and battery for an off grid system. It all starts with a specification of what the load is expected to be (kWh) and in what season and what location, including the tilt and orientation of the solar array and how much shading it is subject to. Working with good data one can design a system as reliable as those designed for use in space.

My experience with PV power started in 1980 with, of course, an off grid solar power system for my cabin. By 1985 I was working in the solar power field, and for many years all of our designs were to power off grid needs. Off grid equipment has changed some since those days, but the designs are still essentially very similar. With my extensive experience, I can assist our customers with the design and specification of materials for off grid systems, as well as grid connected systems.

Written By: Brad Bassett, AEE Solar Sr. Application Engineer, “I read the manual, (even written a few)”

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