For the last two years I have been focused on developing alternative solutions for Space-based Solar Power (SBSP). This started with an extensive review of past concepts to determine why SBSP remained uneconomical forty years after its invention by Dr. Peter Glaser. The conclusion was that locating the SBSP Satellites in GEO posed a substantial mass penalty on the Satellites due to the need for a very large satellite transmitter and the need for in-space transportation from low Earth orbit (LEO) to geostationary orbit (GEO). So the question then became – If not GEO where?

I first looked at Equatorial low Earth orbits (ELEO) and decided there were too many problems, such as Earth shading and short transmissions times (the transmission problem was solved later), and looked for a better solution. The solution turned out to be a low Molniya orbit. The Molniya orbit was discovered by the Soviets and used for communications and spy satellites. Today the Sirius Satellite Radio satellites use this orbit to transmit their signals to US customers. A Molniya orbit is simply a stable elliptical orbit with an inclination of 63.4 degrees. This inclination puts the satellite high above the Earth and looking down at the northern industrialized countries.  Due to the ellipse the satellite would have a long dwell time over the ground receiver (rectenna). Here the satellites high apogees and low perigees. The drawback of using a low Molniya orbit is that you only get to utilize the satellite for percentage of the orbit. However, the mass reductions in transmitter mass are so great that it is still far more cost effective than GEO based systems and this translates into smaller, cheaper satellites and much lower launch costs. Also, the ground rectenna is much smaller at just a fraction of the size needed for GEO SBSP. The satellite would orbit the Earth several times each day and could supply power to ground rectenna as the Earth rotates underneath the satellite.

Another problem with past SBSP Satellite designs was that they were huge and required new, large and super cheap rockets to put them into space (These do not exist). To make the satellites more affordable I broke the large mega-satellite it into smaller independent, free flying satellites of only 20,000kg each. These could then launch on existing launch vehicles such as the Delta IV, Atlas V, Ariane 5 and Proton. Future heavy lift launch vehicles can be utilized when they become available.

After doing all of this I discovered that while this was a tremendous improvement the satellites where still not profitable. This should give you an idea of just how hard developing SBSP really is and why it has never been developed. The skeptics have always been right. I needed more innovation. I had noticed a trend in increased solar concentration in past designs. In the 1970s there was a proposal for 2x solar concentration, which reduced the original NASA base-line design by about thirty one percent. Then in the 1980s there where proposed designs at 4x solar concentration and then in 1990s 10x designs and now 100x designs. Looking at this trend I decided to research the state-of-art in solar concentration and found that in 2008 IBM has demonstrated 2,300 suns concentration using personal computer (PC) cooling technology to keep the photovoltaic cells from overheating. I then applied a 2,000 sun solar concentration level to the Molniya SBSP Satellite design and found that it was not only economically viable but potentially highly profitable.

Having achieved a viable design I went back and applied the 2,000 sun concentration to the ELEO design, added flywheels for on-board energy storage between transmissions and found that it was also potentially highly profitable. There are now two low cost SBSP systems concepts, one for the industrialized nations in the north and one for the developing nations on or near the equator.

How profitable? For the Molniya orbiting satellites and assuming the satellites will operate at full capacity as peak power systems and that electricity will sell at for 16 cents a kilowatt hour, a 10,000 megawatt satellite constellation will generate $9,450 million a year in revenue (revenue discounted by 30% for lost utilization). This adds up to $283 Billion over a thirty-year period. These satellites will produce enough revenue to pay off the original investment, including the support systems, and return a very handsome profit. After return of the initial investment, the cost of energy from the satellites will drop to the cost of operating and maintaining them. There is no fuel to buy and no more debt to pay. The benefits will come to all of us in the form of very low-cost energy.

To produce 10,000 megawatts of power we would need 100 satellites each producing 100 megawatts of power. The cost to launch these satellites is estimated at $100 million each assuming the use of the Russian Proton launch vehicle. This gives a total launch cost of $10 billion. Assuming a cost per satellite of $300 million the cost of the constellation would be $30 billion for the satellites. Subtracting those costs from the $283 billion in revenues leaves $243 billion over thirty years or $8.1 billion annually. Clearly the deployment of these satellites into the peak power market would be hugely profitable.

I took this just a bit further and designed a proprietary photovoltaic system for the satellites with an efficiency of 50% based on the “Rainbow” concept. This concept uses photovoltaic cells designed for specific bandgaps. This combination of high efficiency, high solar concentration, low orbits and small satellites provides a solution to the cost effective development of SBSP. With an investment of approximately $1 billion these designs could be orbiting in less than ten years. Note that this one time funding level for development is only half of one year’s funding for “clean coal” demonstrations proposed in the US and 1/60th the amount spent each year in the European Union on Cap and Trade.

This estimated investment only covers the development cost as the operational satellites would be leased to Countries, States, Major Cities and Private Energy Companies. This approach provides an almost unlimited access to capital. It is envisioned that there would be a total of forty rectenna with twenty around the equator and twenty in the north receiving a total of 20,000 megawatts of power from two satellite constellations of 100 satellites each. This does however create a unique problem as there is no launch service provider that can place that many satellites into orbit in a reasonable timeframe without substantial new investment in launch capability. At most we could expect to launch five satellites each year based on existing launch capability of any single provider. Therefore, it would take forty years to complete both constellations without substantial new space lift capability.

The technology now exists to solve the Earth’s energy problems with low cost power from space and at the same time solve the Global Warming problem. This technology will stimulate new investment in launch vehicles and can provide a basis for development of solar electric space transportation. There is still much work to do but there is no longer any question that SBSP can be an economically viable part of the Earth’s energy equation and will be a major factor in moving humanity into space. SBSP is the next step in space development and it is a step we can take now.

A new Space Based Solar Power concept utilizing an elliptical 3-Hour Sub-Molniya Orbit and concentrated solar energy for Solar Dynamic and Photovoltaic Solar Power Satellite systems.