Tag Archives: solar energy

Limitless energy

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neil hunterThe Sun supplies approximately 100,000 TeraWatts (TW) of energy to the Earth continuously. To put this into perspective the entire generating capacity of China is 1TW and the global population as a whole uses 15TW. Plants use about 100TW via photosynthesis. Most our energy consumption is derived from biomass created millions of years ago by photosynthesis and stored as coal, gas or oil when the plant died and was crushed by geological processes.

I am stealing and paraphrasing from Professor Neil Hunter’s presentation at the Royal Society’s Scientific Discussion Meeting on Bio-inspiration for New Technologies. Of course, as Neil pointed out, the energy from the Sun arrives across a range of wavelengths some of which are damaging to our health. So fortunately for us the Earth’s atmosphere filters out a number of wavelengths but nevertheless a broad band of wavelengths still arrives at the Earth’s surface. Photosynthesis only makes use of two relatively narrowbands of light….

Mankind’s efforts to use solar energy look pathetic alongside Nature’s performance and should be humbling to any engineer or scientist. But it is also an inspiration to do better. We need cheap clean energy for everyone. It is being delivered everyday but we don’t know how to use it.

Tidal energy

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Photo credit: Tom

Photo credit: Tom

The world is slowing down! According to Max Tegmark, in his book ‘Our Mathematical Universe’, the rotational velocity of the Earth is being reduced as some of its kinetic energy is dissipated as tidal energy. It is possible to estimate the age of planet from the rate of slow down by assuming that at its birth it was spinning as fast as possible without the centrifugal forces pulling it apart. The answer turns out to be about 4 to 5 billion years which roughly agrees with radioactive dating of the oldest rocks in Western Australia and bits of meteorites that imply the solar system came into being about 4.5 billion years ago.

So does this imply that tidal energy is not really a renewable energy source? I think it is just an issue of timescale. Fossil fuels are seen as non-renewable because the formation of coal and oil substrates happens on geological timescales. Biomass is a bit quicker because we skip the fossilisation process and renewal is measured in months. Fossil fuels and biomass are both ways of storing solar energy in chemical bonds. Nature is much better at converting and storing solar energy than mankind. But, solar energy would appear to be the ultimate renewable energy source. Every morning its there, though often hidden by cloud where I live. The sun will eventually die but again this won’t happen anytime soon but on a long geological timescale.