IT IS NO exaggeration to say a rainbow is the icon of life on Earth. Rainbows reveal the energy spectrum that supports most life. The longer wavelengths (infrared) provide a source of thermal energy; shorter wavelengths (ultraviolet) are a source of photonics or light energy.
Insofar as the immediate welfare of humans is concerned, the energy that supports us comes from the sun, the main exceptions being tidal and elemental energies. Tidal energy is generated by gravitational forces exerted by extraterrestrial bodies. Elemental energy is the energy embodied in the matter forming our universe.
As well as incoming solar radiation, the Earth re-radiates energy back into space. Nature had balanced this process over millions of years to produce a stable environment that provided sufficient time for complex life forms to evolve. Her balance included a cocktail of atmospheric gases, maintaining a ratio, one to the other, that was auspicious for the wellbeing of life as we know it.
Solar energy is available either as direct radiation from the sun or as indirect energy. Indirect energy includes bio-storage – achieved via natural photosynthetic processes – geothermal, wind power, hydropower and chemical storage such as nuclear or hydrocarbon deposits.
In the timeframe of the Earth’s existence, energy stored chemically – or even that stored as geothermal heat – is a finite resource. Transient options such as direct radiation, wind power, hydropower, tidal movements and biomass energy are all, within limits, sustainable energy resources.
The stability of the Earth’s climate hinges on society’s choice of energy supply, not on how much energy is consumed.
Light photons can be converted to electricity artificially, using cells made from semiconducting materials such as silicon. Photovoltaic cells convert sunlight directly to electricity. The panel they normally come on should not be confused with a solar “hot water” 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 photovoltaic panel output measurement is 25°C and any increase in temperature is accompanied by a corresponding reduction in conversion efficiency. Cool, or even cold, sunny locations are best suited for deploying photovoltaic technology.
The stability of the Earth’s climate hinges on society’s choice of energy supply, not on how much energy is consumed. The burning of fossil fuels – supplemented by the manufacture of cement from limestone – is the main trigger for atmospheric pollution and climate destabilisation. While the environmental repercussions of using energy are minimal, the environmental repercussions of extracting chemical energy from fossil hydrocarbon storages are proving to be catastrophic.
Fossil hydrocarbon and limestone deposits were formed by ancient, biological processes. They involved chemical reactions that extracted and sequestered various atmospheric gases (including carbon dioxide and methane). Those processes used vast amounts of solar energy over a very long period. Eventually, they achieved a balance of atmospheric gases that suits life as we know it. Accessing that stored energy simply unwinds the balancing mechanism.
We are now causing the Earth’s energy balances to change at a rate that is beyond the ability of most life forms to adapt to. Natural diversity is being decimated and the system that supports life, as it stands, is trending towards chaos. Should we choose to re-instate a benign balance, we can assume that the account rendered by nature will demand an equivalent amount of energy, possibly with interest. The sooner mankind starts paying its debts, the easier nature’s impost will be.
Fossil fuels are an inefficient source of energy. The processes involved in bringing them to the market from their solar origins yield a small fraction of 1% of the energy used to store the hydrocarbons in the first place. The organisms that the hydrocarbon deposits derived from were relatively inefficient solar energy converters compared to modern plants.
The sequestering mechanisms nature used for storing hydrocarbons have gross inefficiencies. Almost all of the residual energy stored in those deposits, that we seek to exploit, is lost to a combination of low extraction efficiencies and parasitic demands attributable to transportation, processing and conversion.
Sustainable energy options are much more efficient. Modern plants such as sugar cane are capable of converting the sunlight that falls on them into stored energy. Hydropower is a limited resource, but converting 80%-plus of the available energy is possible. Modern wind turbines can extract over 20% of the wind’s energy.
Direct conversion of sunlight is efficient and relatively unlimited. Solar photovoltaic technologies are now capable of extracting over 40% of the sunlight that falls on them each day. Combined solar photovoltaic and solar thermal technologies return even more. Increased use of transient energy resources, including direct conversion of sunlight, would have a positive impact on climate stability.
There is no one technology that is capable of sustaining all of mankind’s energy needs without altering natural balances. It would seem a bigger leap for mankind than when Neil Armstrong stepped onto the moon if demands for energy were met by using a mix of renewable energy sources to meet base loads while limiting raids on fossil hydrocarbons for emergencies.
As a transition fuel, hydrogen-enriched natural gas has the promise of great versatility with a low environmental impact. Using emerging technologies such as fuel cells, hydrogen-enriched natural gas is as suitable for transport applications as it is for power generation. It is not an untested fuel, being common post-war in most of Australia’s domestic gas supplies.
Keith Presnell, now retired, was director of renewable energy research at Charles Darwin University and Australia's representative on the International Energy Agency (IEA's) photovoltaic subcommittee.
*Note: Hero image via Uswitch.com | Flickr
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