FHSST Biology/Contents/Index/ES/Ecosystems/Resources/Energy flow within environments

2.3. Energy flow within the environment

Energy on earth originates from the sun. What about undersea thermal vents? Energy on Earth allows life to exist. The sun facilitates the movements of air and water in the atmosphere. The sun also facilitated the formation of non-renewable resources such as oil and coal. Green plants at most capture 1/20 of the suns energy that reaches Earth. Plants use most of that energy for metabolisms and therefore only 1% of energy is converted to plant tissue.

Energy flow can be depicted in a food chain.

Plant - herbivores - carnivores Decomposer Organisms

Energy has allowed man to become more industrialised and even allowed man to travel to the moon!

Because of energy loss, biomass normally diminishes through the stages of secondary and tertiary production.


 * top carnivores
 * carnivores
 * herbivores
 * primary producers

The biggest animals tend to be on top of the pyramid. The world’s biggest land and sea animals, i.e. the elephant and Blue Whale have decided to cut out the middle man, and instead of being top carnivores, feed directly on plants.

Look up an interesting article on the net.

The term power is used for energy obtained for urban and industrial purposes, measured by the rate of flow of useful energy that can be made to work. Some measures of power are the kilojoule (KJ), the megajoule (MJ) and the kilowatt (KW).

Look up article on oil demand.

Wold consumption of energy has been doubling every 14 years. The development of new technology may rapidly change energy consumption.

Types of energy sources:


 * 1) Diversion of current energy flows:
 * 2) Solar flux (photosynthesis)
 * 3) Falling water & wind
 * 4) geothermal energy
 * 5) tidal energy
 * 6) release of stored energy
 * 7) fossil fuels – oil, coal, gas. All represent stored energy from photosynthesis from the geological past and which yield energy upon combustion.
 * 8) Nuclear energy. Liberates energy contained in the nucleus of the atom.

The advancement of societies followed the access and use of energy:


 * 1) Hunter – gatherer societies. Used solar energy via food and fuel wood.
 * 2) Agricultural societies. Used solar energy and the labour of beasts as well as wind and water power. The surplus food supported civilization and economy.
 * 3) Advanced industrial societies. ¼ used for transport, 1/5 in houses, 12% in offices, hospitals and schools, 42% in the industrial sector.

Different forms of energy supply:

Coal: This is the most secure and assured energy source. Causes large environmental pollution but may be utilized more as oil becomes more scarce.

Oil: Estimated to have a short remaining lifespan Oil has more uses then just a form of fuel. Once supply has passed its peak, oil may become too important to use as a fuel. It is estimated that the supply of oil will begin to run out by 2030.

Natural Gas: linked to petroleum.

Fossil fuels are not likely to run out soon. By 2030 most oil and gas resources will be exhausted and much coal reserved will have been depleted.

Nuclear power: This is generated when the nucleus of Uranium 235 is bombarded with neutrons – the uranium breaks into two fragments and a release of energy occurs. 1 kg of Uranium 235 can release the equivalent energy to 2500 kg of coal.

Hydropower: This is an ancient form of power generation. Basically the power that is generated is a function of volume and drop. The first large scale power generation was done at the Niagra falls. The impoundments of dams cause evaporation and silting.

Geothermal energy:

The thermal gradient is 25 degrees per KM but is steeper in some places, where there is tectonic instability. Often geothermal energy is in the form of water or steam. Heat is used to either generate electricity, or for other uses, e.g. heating a hotel in Paris and greenhouses and hotels in Iceland, for spas and crocodile farms in Japan. Italy, the USA have electrical power plants using this source.

Windpower: This has been in use since the 12’th century. The major problem is that wind speeds are so variable. Storage is important in this case. Wind could be used to hydrolize water to provide hydrogen as a fuel. A large land area is needed for wind power, 4 – 5 times that of direct solar collection. This form of energy is likely to be useful when coupled with other technology. This is the largest potential energy source.

Tidal power. Potentially using trapped water at high tide and allowing water to ebb through turbines, thereby generating electricity. Lookup this.

Wave power. Few attempts and low potential for new energy source.

Biomass: Generating power from organic waste i.e. straw, refuse, sewerage, pulp waste. Waste is fermented to give off methane. There are many such installations in use.

Solar energy:

Constant and inexaustable. The total energy falling on 100 km2 of tropics would cover all consumption. Solar energy is very diffuse, therefore needs to be converted to more palable forms of energy such as electricity or hydrogen. A common use of solar power is for the heating of water or space. Solar thermal electrical conversion uses an optical concentrator which focuses on an absorber which then transmits the heat to an electrical generating plant. Photovoltaic conversion turns radiation directly into DC current via a silicon cell. Producing hydrogen using this method may be a possibility. Solar power would be ideal for decentralised, low output use such as remote rural areas, small localised industries, clinics, schools and homes.

Stretching the resources.

This could be done by energy conservation i.e. using less energy and better use of energy. For instance, the heat generated by powerstations could be used to heat homes, insulation in homes, public transport.

All the energy transferred undergoes a change of form that will tend to heat energy.

Deep sea bed usually regarded as unproductive. However volcanically active areas of the sea bed heat sea water in crack systems – releasing hot water loaded with metals and dissolved sulfide. These areas are associated with fantastic diversity of animals – large limpits, clams, tube worms and mussels. Get pic. How does such a productive ecosystem occur amidst such poverty? Certain bacteria derive energy from oxidation of sulfide, providing a food source for animals.