Let's face it: we live in world that provides a quality of life that exceeds the dreams of historical kings and emperors. At the touch of a button, we have light, heat, clean water, instantaneous communication, boundless access to information, miracle medical technology, and a near-endless variety of food. Whether we realize it or not, the wonders of modern society are possible only because of the cheap oil and coal we've been burning for the past hundred years or so. Unfortunately, the fossil fuels we've taken for granted will not last forever, and one of the biggest challenges our species faces in the coming years is the need to find safe, clean, reliable, and renewable power sources.
There are many avenues of research being pursued in the quest for new power sources, but the most far-out idea is (literally) space-based solar power. Traditional solar photovoltaic (PV) arrays are attractive for a number of reasons, but there are also a number of problems with them. An interesting variation on the traditional, ground-based solar PV is discussed in detail in a recent article over at The Oil Drum. The article discusses the prospect of placing the PV arrays in orbit as geosynchronous satellites that collect solar power and beam it back down to ground stations as microwave energy.
Audacious? Definitely. Possible and Practical? Well, that depends on a number of factors, as discussed in the article.
As mentioned by the author of the article, Keith Henson, the main advantages of space-based solar are:
- A system of power satellites can be scaled as required by the needs of civilization
- A satellite in geosynchronous orbit is illuminated 99% of the time
- The constant illumination of power satellites make them about nine times as effective as an equivalently-sized ground-based collector
- Micro-gravity and a lack of wind allows power satellites to be constructed using much lighter material than their ground-based counterparts
- Power satellites have a very short energy payback time
Unfortunately, power satellites also have some disadvantages:
- Due to optical constraints, power satellites don't scale down well, so 5 GW is the smallest practical size possible
- 50% of power generated is lost by the time it is received on the ground; losses are due to conversion to microwaves, dispersion of energy during transmission, and reconversion back from microwave
- Lifting the satellites into orbit is extremely expensive, both financially and energetically
That last point is obviously the critical hurdle that must be overcome in order to make the concept of orbital solar power practical.
The article goes into extensive detail in analyzing the economics of orbital solar power generation and the logistics of placing the satellites into orbit. The latter point is the most interesting aspect of the article, since it touches on the limitations of chemical rocket technology, and the possible alternatives such as space planes and laser propulsion systems. Finally, the overall energy-return-on-energy-invested (EROEI) for solar satellites is discussed.
The concept of space-based power generation is fascinating, and Keith does a fantastic job of providing a high-level introduction to the topic. The comments from Oil Drum readers are also worth reading, though be forewarned that they get a little flamey at times (pity that couldn't be tapped to generate useful power).
Head over to the article at the Oil Drum for the full story....
