First Successful Space Demonstration of a Thermal Accumulator for Microsatellites

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  HODOYOSHI 4 and the Heat Storage Device: The accumulator and reference surface differ in that the former includes a heat storage medium, while the latter does not. The material of the surface, and the surface treatment, are the same. A comparison of the temperatures of the reference surface and accumulator confirms that the accumulator stores and releases heat.
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  Orbital Test Results: The blue lines indicate the temperature of the reference surface, the orange points indicate the accumulator temperature, and the yellow lines indicate the amount of power generated by the solar panels. Generation of zero power by the solar panels indicates that Hodoyoshi 4 is in the earth’s shadow. Generation of any amount of power above zero indicates that Hodoyoshi 4 is in sunlight. As Hodoyoshi 4 emerges from the earth’s shadow, it is increasingly exposed to sunlight, and temperatures of the reference surface and accumulator increase. At approximately 90°C, the accumulator temperature (orange points) becomes less than the reference surface temperature (blue lines). The accumulator stores heat (i.e. absorbs heat) in this region, preventing an increase in temperature. Hodoyoshi 4 then moves into the earth’s shadow, and the temperatures of the reference surface and accumulator decrease. It is thus apparent that when the temperature drops to below 10°C, the temperature of the accumulator (orange points) becomes higher than the temperature of the reference surface. The accumulator releases heat in this region, thus preventing a drop in temperature.