9 April 2008
- Power (Good)
Why Space Solar Power Is Superior to Biomass Fuel
And what to do about it
By Marco C. Bernasconi

In the past thirty-five years, governments have spent billions of dollars, euros, pounds, and yuan toward research into alternative energy, with unimpressive results. Over the same time frame, research and development of space solar power ( SSP) received less than $30 million (of which $15.6 million came from the US Department of Energy and NASA). Today, governments are promising to spend hundred of millions to investigate measures to fight global warming.

Currently, not a cent out of this money will be used to study SSP.

According to the US Energy Information Administration's 2006 estimate, the world consumed 15TW total energy in 2004, and worldwide energy consumption increases on the average of 2% a year. As the world population continues to increase, and as many countries are making inroads in economic development (which leads to an increase in energy consumption), greater energy resources are required. Beside fossil fuels, only terrestrial solar power (i.e., ground-based solar power) can come close to supplying required power levels (although wind, ocean-thermal, and hydropower systems could contribute).

Kulcinski and colleagues created a system to measure the energy-payback ratio (EPR), the amount of electrical energy produced compared to the energy expended to fuel, build, and operate power plants: A higher EPR of a power-generation system means that less energy goes into operating it, likely reducing any associated environmental

If a power option has a ratio of close to one, it means it consumes almost as much energy as it produces, making it a poor supplier in general terms. Kulcinski and colleagues estimated values of 23 for wind plants (without power storage) – exceeded only by fusion systems – 16 for fission, and 11 for coal.

Following a similar methodology, we estimate SSP has an EPR of 20.

More significantly, calculations of the thermal burden multiplier (the ratio between the total energy released and the usable energy produced) yielded values of 1.4 for the space-based systems, compared to about 4 for photovoltaic arrays or 5 for nuclear power. This multiplier directly indicates the potential environmental impact of a power system.

A power plant may add energy to the biosphere in yet another way: by changing the amount of solar energy absorbed on its site. Of course, the importance of this change will depend on the surface area the plant occupies, which becomes significant for those systems directly exploiting the Sun's light. The proverbial "photovoltaic panel in the desert" offers a good example, as desert soil has an absorptance of 0.75. Given that solar cells have a 0.85-absorptance, each unit area injects into the biosphere 10% _more_ solar flux – about the same amount of generated power.

If we look beyond fossil fuels (but stop short of nuclear fusion power), we observe that ground-based solar power and nuclear fission plants can satisfy the world’s energy needs, but they impose a significantly larger thermal burden than SSP. Currently, terrestrial power plants not burning fossil fuels still provide only a small fraction of the world's energy needs (even nuclear power remains at 0.3 TW). A well-supported space power system could grow at higher rate and surpass them in terms of generated power.

Tragically, many governments currently consider biomass-derived fuels the solution of choice. In reality, global assessments of different types of biomass showed it insufficient: biomass-derived fuels could provide only a few percentage points of the population’s needs.

Furthermore, as an energy source – and in particular when transformed into liquid fuels – biomass creates a thermal burden, with a multiplier values around 2, a non-negligible amount, considering that this use of solar power is perceived as a solution to significantly reduce the carbon footprint.

Worse, US federal support for corn-ethanol production has created an economic burden, leading to an appreciable increase in the prices of food.

In quantitative terms, US gasoline consumption alone corresponds to some 2 kW/person. When one knows that the global biosphere production would work out at some 11- 17 kW/person, one can see how desultory any attempt to use biomass energy will be.

Frankly, I'm not surprised but saddened by how people announce their use of “green” plastics and “green” fuels, and I have to consider these events and trends as driven primarily by ignorance. Most people are not even aware of being unaware: few people understand the concept power from space, and the people who have heard about it have been conditioned to reject it.

But it’s up to us to fight ignorance by putting forward facts and constructive ideas. Here are a few suggestions:

Contribute to discussions about relevant technologies, like fuel management, propellant production, resources utilization, space assembly and manufacturing, etc.

Insist on having the technical heritage of pioneers (e.g., Cole, O'Neill, Ehricke, etc.) properly disseminated, understood, and expanded.

Argue in favour of an environment conducive to the growth of private space initiatives.

Recommend to space and energy agencies that advanced studies be performed by small, high-competence enterprises, independent foundations, research facilities, and academic institutes hosting original thinkers and experts.

Finally, define and present projects that can help develop the required technologies. Identify and discuss strategies for a constructive astronautical endeavour.

Modest efforts may not only receive enough voluntary support to move forward, but also they may stimulate a range of spontaneous ventures. These ventures could possibly create a better cultural, a better world, and give us a brighter future.

Even if we fail to actually alter the immediate course, we may garner some technical results or place the seed for future changes.

If not us, then who?


David R Criswell & Robert D Waldron (1991). Results of Analyses of a Lunar-Based Power System to Supply Earth with 20 TW of Electric Power. Proceedings of the 2nd International Symposium SPS 91 - Power from Space, Gif-sur-Yvette (France), August 27-30, 186-193; also in: Richard Geyer (Editor) (1993) A Global Warming Forum: Scientific, Economic, & Legal Overview -- Chapter 5. CRC Press, Boca Raton (Florida).

Scott W White & Gerald L Kulcinski (1998). “Birth to Death” Analysis of the Energy Payback Ratio & CO2 Gas Emission Rates from Coal, Fission, Wind, & DT Fusion Electrical Power Plants. Paper presented at the 6th IAEA Meeting of Fusion Power Plant Design & Technology, Culham (England), March 23-27; Fusion Technology Institute, University of Wisconsin at Madison, Report UWFDM-1063. (February 1999)

PG Meier & Gerald L Kulcinski (2000). The Potential for Fusion Power to Mitigate US Greenhouse Gas Emissions. Paper presented at the 14th Topical Meeting on the Technology of Fusion Energy, Park City (Utah), October 15-19; also: Fusion Technology Institute, University of Wisconsin at Madison, Report UWFDM-1143. (October)

PG Meier & Gerald L Kulcinski (2002). Life-Cycle Energy Requirements & Greenhouse Gas Emission for Building-Integrated Photovoltaics. Fusion Technology Institute, U of Wisconsin at Madison, Report UWFDM-1185. (April)

Marco C Bernasconi & W Weindorf (2004). SPS Comparison Study -- Energy Assessment. MCB Consultants document TDR-04-019, Issue A.

Marco C Bernasconi (1997). Space & Energy. Paper (invited) presented at the Kuffner Observatory Jubilee Celebration Symposium, Vienna (Austria), September 4-5; Claudia Schlögl & Peter Habison (Editors). Proceedings of the Vienna Symposium “Space Visions for the 21st Century.” Kuffner Sternwarte, Vienna (Austria).
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9 April 2008
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