Guest essay by Eric Worrall
Renewables in their current form are a nonsense solution to the world’s energy needs. However, there is a combination of technologies which could make solar power a significant, reliable contributor to the World’s energy needs. But I doubt any green will rush to embrace it.
How do we make solar power reliable? The problems which make solar power unreliable are mainly related to weather – clouds, rain, snow, winter, poor air quality, anything which interrupts the flow of light reaching the collector.
The solution is to put the solar panels beyond the reach of all these problems – by putting them into orbit. Launching solar panels into orbit might sound far fetched, but it is being seriously considered by a number of national space programmes.
Space-based solar power (SBSP) is the concept of collecting solar power in space (using an “SPS”, that is, a “solar-power satellite” or a “satellite power system”) for use on Earth. It has been in research since the early 1970s.
SBSP would differ from current solar collection methods in that the means used to collect energy would reside on an orbiting satellite instead of on Earth’s surface. Some projected benefits of such a system are a higher collection rate and a longer collection period due to the lack of a diffusing atmosphere and night time in space.
Part of the solar energy (55–60%) is lost on its way through the atmosphere by the effects of reflection and absorption. Space-based solar power systems convert sunlight to microwaves outside the atmosphere, avoiding these losses, and the downtime (and cosine losses, for fixed flat-plate collectors) due to the Earth’s rotation.
Besides the cost of implementing such a system, SBSP also introduces several new hurdles, primarily the problem of transmitting energy from orbit to Earth’s surface for use. Since wires extending from Earth’s surface to an orbiting satellite are neither practical nor feasible with current technology, SBSP designs generally include the use of some manner of wireless power transmission. The collecting satellite would convert solar energy into electrical energy on board, powering a microwave transmitter or laser emitter, and focus its beam toward a collector (rectenna) on Earth’s surface. Radiation and micrometeoroid damage could also become concerns for SBSP.
SBSP is considered a form of sustainable or green energy, renewable energy, and is occasionally considered among climate engineering proposals. It is attractive to those seeking large-scale solutions to anthropogenic climate change or fossil fuel depletion (such as peak oil).
SBSP is being actively pursued by the Japan and China. In 2008 Japan passed its Basic Space Law which established Space Solar Power as a national goal and JAXA has a roadmap to commercial SBSP. In 2015 the China Academy for Space Technology (CAST) briefed their roadmap at the International Space Development Conference (ISDC) where they showcased their road map to a 1 GW commercial system in 2050 and unveiled a video and description of their design. A proposal for the United States to lead in Space Solar Power has recently received high level attention after it won the D3 (Diplomacy, Development, Defense) competition sponsored by the Secretary of Defense, Secretary of State, and USAID Director. As of May 21, 2015, there was an on Change.org and a second active petition at Whitehouse website.
The obstacle to space based solar power is obviously the launch cost. If you are paying thousands of dollars per kilogram for payload delivered into Earth orbit, launching thousands of tons of solar collector equipment is a sure route to a very expensive solar space station.
So how do we bring down the launch cost? There are a number of technologies on the drawing board, but lets stick with known technology, preferably a technology which has already been tested to some extent.
There is one cheap space launch technology which stands out – simple design, high thrust, high impulse, based on well understood engineering principles, capable of economically launching thousands, even millions of tons into any orbit you want, using a single stage launch vehicle. The only problem is the fallout.
Project Orion was a study of a spacecraft intended to be directly propelled by a series of explosions of atomic bombs behind the craft (nuclear pulse propulsion). Early versions of this vehicle were proposed to take off from the ground with significant associated nuclear fallout; later versions were presented for use only in space.
The idea of rocket propulsion by combustion of explosive substance was first proposed by Russian explosives expert Nikolai Kibalchich in 1881, and in 1891 similar ideas were developed independently by German engineer Hermann Ganswindt. General proposals of nuclear propulsion were first made by Stanislaw Ulam in 1946, and preliminary calculations were made by F. Reines and Ulam in a Los Alamos memorandum dated 1947. The actual project, initiated in 1958, was led by Ted Taylor at General Atomics and physicist Freeman Dyson, who at Taylor’s request took a year away from the Institute for Advanced Study in Princeton to work on the project.
The Orion concept offered high thrust and high specific impulse, or propellant efficiency, at the same time. The unprecedented extreme power requirements for doing so would be met by nuclear explosions, of such power relative to the vehicle’s mass as to be survived only by using external detonations without attempting to contain them in internal structures. As a qualitative comparison, traditional chemical rockets—such as the Saturn V that took the Apollo program to the Moon—produce high thrust with low specific impulse, whereas electric ion engines produce a small amount of thrust very efficiently. Orion would have offered performance greater than the most advanced conventional or nuclear rocket engines then under consideration. Supporters of Project Orion felt that it had potential for cheap interplanetary travel, but it lost political approval over concerns with fallout from its propulsion.
I doubt greens are going to rush to embrace a renewables solution which involves the release of atmospheric nuclear fallout, even if that fallout could be constrained to safe levels. But if the future viability of the planet was really at stake, and if nuclear power was unacceptable for whatever reason, solar power satellites could realistically and reliably deliver the energy our civilisation needs, with minimal carbon emissions, other than whatever was emitted during the construction of the components.