Fossil fuels are inefficient and the consequences of extracting such energy destroy the balance of nature. Renewable energy options are vital for the future of our planet, writes Keith Prenell.
IT IS NO exaggeration to say that a rainbow is the icon of life on Earth. Rainbows reveal the energy spectrum that supports most life. The longer wavelengths (infrared) are a source of thermal energy; shorter wavelengths (ultraviolet) are a source of photonics or light energy.
As far as the immediate well-being of man is concerned, the energy that sustains us comes from the sun, with the main exceptions being tidal and elemental energies. Tidal energy is generated by gravitational forces exerted by alien bodies. Elemental energy is the energy embodied in the matter that makes up our universe.
In addition to incoming solar radiation, the earth radiates energy back into space. Nature had balanced this process over millions of years to create a stable environment that allowed enough time for complex life forms to evolve. Her balance included a cocktail of atmospheric gases, which maintained a relationship to each other favorable to the well-being of life as we know it.
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For life as we know it to continue, we must recognize that there are natural limits to growth. Economic growth equals increased demand, which is simply not sustainable in a finite world.
Solar energy is available as direct radiation from the sun or as indirect energy. Indirect energy includes bio-storage – achieved through natural photosynthetic processes – geothermal, wind energy, hydropower and chemical storage such as nuclear or hydrocarbon deposits.
In the time frame of Earth’s existence, energy stored chemically — or even stored as geothermal heat — is a finite resource. Temporary options such as direct radiation, wind energy, hydropower, tidal movements and biomass energy are all, within limits, renewable energy sources.
Photons of light can be artificially converted into electricity using cells made of semiconducting materials such as silicon. Photovoltaic cells convert sunlight directly into electricity. The panel they normally turn on should not be confused with a “hot water” solar panel. The latter uses the thermal end of the solar spectrum to heat water.
Surprisingly, a photovoltaic panel does not like heat. The standard for measuring the output of photovoltaic panels is 25C and each temperature increase is accompanied by a corresponding reduction in conversion efficiency. Cool, or even cold, sunny locations are best suited for the application of photovoltaic technology.
The stability of the Earth’s climate depends on society’s choice of energy supply, not on how much energy is consumed† The combustion of fossil fuels – supplemented by the production of cement from limestone – is the main cause of air pollution and climate destabilization. While the environmental impacts of using energy are minimal, the environmental impacts of extracting chemical energy from fossil hydrocarbon deposits are proving catastrophic.
Fossil hydrocarbon and limestone deposits were formed by ancient biological processes. It involved chemical reactions that extracted and sequestered various atmospheric gases (including carbon dioxide and methane). Those processes used huge amounts of solar energy over a very long period of time. Ultimately, they achieved a balance of atmospheric gases befitting life as we know it. By accessing that stored energy, the balancing mechanism is simply disrupted.
We are now causing the Earth’s energy balances to change at a rate beyond the ability of most life forms to adapt. Natural diversity is being decimated and the system that supports life is leaning towards chaos. Should we choose to restore a benign balance, we can assume that the bill generated by nature will demand an equivalent amount of energy, possibly with interest. The sooner humanity begins to pay its debts, the easier the burden on nature will be.
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Fossil fuels are an inefficient source of energy. The processes required to bring them to market from their solar origins provide a small fraction of 1% of the energy used to store the hydrocarbons in the first place. The organisms from which the hydrocarbon deposits originated were relatively inefficient solar energy converters compared to modern plants.
The nature of the sequestering mechanisms used for the storage of hydrocarbons have major inefficiencies. Nearly all of the residual energy stored in those deposits that we want to exploit is lost due to a combination of low extraction efficiencies and parasitic demands due to transport, processing and conversion.
Renewable energy options are much more efficient. Modern plants such as sugar cane are able to convert sunlight that falls on them into stored energy. Hydropower is a limited resource, but converting 80% of the available energy is possible. Modern wind turbines can extract more than 20% of the wind energy.
Direct conversion of sunlight is efficient and relatively unlimited. Photovoltaic solar technologies are now able to extract more than 40% of the sunlight that falls on them every day. Combined photovoltaic and solar thermal technologies are making a comeback even more. More use of temporary energy sources, including direct conversion of sunlight, would have a positive effect on climate stability.
There is no technology capable of meeting all of humanity’s energy needs without altering the natural balance. It seems like a bigger leap for humanity than when Neil Armstrong stepped on the moon if the energy demand was met by using a mix of renewables to meet the base load while limiting attacks on fossil fuels for emergencies.
Hydrogen-enriched natural gas as a transition fuel promises great versatility with a low environmental impact. Using emerging technologies such as fuel cells, hydrogen-enriched natural gas is as suitable for transportation applications as it is for power generation. It is not an untested fuel, which was common in most of Australia’s domestic gas supplies after the war.
Keith Presnell, now retired, was director of renewable energy research at Charles Darwin University and Australia’s representative on the International Energy Agency’s (IEA) photovoltaics subcommittee.