Satellites could send electric energy to Earth through microwave radiation

Dec 28, 2007 10:54 GMT  ·  By
Artistic impression of such a sunlight collecting satellite, sending power to Earth through microwave radiation
   Artistic impression of such a sunlight collecting satellite, sending power to Earth through microwave radiation

Unlike other ideas proposed by certain people, including filling up the atmosphere with colloidal carbon in order to block the sunlight and cultivate seaweed to extract the carbon dioxide excess, it seems that, at this year's UN climate conference, the Pentagon finally had a realistic solution for an alternative electric energy source.

The idea is not exactly new, in fact it is rather old. The first such microwave power transmission device was actually demonstrated in 1964 by the American engineer William C. Brown by using a miniature helicopter equipped with an antenna and a rectifier, in order to collect microwave radiation from a high-power microwave emitter. Incredible as it may seem, this concept of wireless electric power transmission has a conversion efficiency of over 90% in optimal circumstances.

The U.S. Defense Department proposed the idea of using large solar panels arrays to collect sunlight in space, as the light intensity outside Earth's atmosphere is about eight times higher, convert the light into electric power that can be used to generate microwave emissions and send the power over to Earth's surface. Then, the microwave radiation could be collected by large rectenna, and converted back into electric energy with extremely high efficiency.

In order to demonstrate the efficiency of the system, Kevin Reed, an American entrepreneur, proposed, at the 58th International Astronautical Congress in Hyderabad, India, in the month of September this year, that, by setting a 80 meter diameter "rectifying antenna" on the uninhabited island of Helen Island, up to 1 megawatt of power could be sent by a satellite orbiting the Earth at an altitude of 480 kilometers. Only one month later, the U.S. Defense Department issued a report showing that a network of sun-collecting satellites could present a viable solution for an alternative energy source for the U.S. military operations.

According to Reed, the construction of such a device would require a budget of at least 800 million dollars, and could be completed by the year 2012, if his international consortium is successful in developing an ultralight solar panel and finds financial support at the same time. Furthermore, the idea is that the satellite would orbit at relatively low altitudes, passing over the rectenna once every 90 minutes in order to beam down the collected energy. Such possibility presents special interest, as electric cars, for example, with built-in rectennas, could draw their power supply directly from the microwave beam, while driving at the same time.

Common beliefs fear the effects of such high levels of microwaves being beamed down to Earth. But studies in this domain repeatedly showed that the microwave radiation levels would be no higher than the dose received while opening the microwave oven door, meaning it is slightly higher than the emissions created by cellular telephones, as the energy beam would be transmitted in diffuse rays collected by a large ground antenna. Furthermore, experiments on multiple generations of animals showed that constant exposure to microwave radiation of this kind or of higher levels does not determine any health issues.