Renewable energy resources overview

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  • Renewable energy resources and the future
    • Intermittency
      • Some resources are not available all the time so they could not be the only source of energy that is used if a continuous supply is needed.
        • Solar power
        • Wind power
        • Tidal power
    • Reliability
      • It is impossible to reliably predict the amount of energy that can be harnessed from some resources.
        • Solar power - affected by cloud cover
        • Wind strength is unpredictable so therefore wave energy is also unpredictable
    • Energy Density
      • Solar, wind and wave powers all have low energy densities
      • HEPs and biofuels have higher energy densities.
    • Ease of Storage
      • The light involved in solar power cannot be stored but the hot water produced in photothermal schemes can be stored for later use.
      • Wind and wave power involve harnessing kinetic energy that cannot be stored, although the electricity produced can be converted into other forms of energy that can be stored.
      • Water in HEP reservoirs can be held back until the energy is needed, although the water flow cannot be stopped completely, because of the effects on the river downstream
      • The chemical energy in biofuels such as wood, biodiesel and alcohol can be stored easily for later use.
    • Suitability for Current Uses of Energy
      • Many renewable resources produce large amounts of energy but it may be low temperature heat, or electricity that is not useful for powering most vehicles, which are the biggest single use of energy
    • Environmental Impacts
      • Renewable energy resources usually have low environmental impacts that do not affect the decision of whether to use them, but some impacts can restrict use.
      • The visual impact of wind farms and HEP reservoirs
      • The ecological impacts of tidal barrages and HEP reservoirs
      • The habitat loss due to increased biofuel production
    • Geographical Constraints
      • Most renewable resources can only be harnessed where natural processes or geographical conditions are suitable.
      • Solar power is most effective where sunlight is reliable and intense
      • HEP can only be harnessed where the climate, geology and topography are suitable
      • Geothermal power can only be harnessed where hot rocks are found near to the surface of the crust
    • Size of Available Resource
      • This may be limited by the natural processes involved and is linked to energy density
        • The velocity of the wind affects the kinetic energy that can be harnessed,
          • There is 8 times as much energy available in wind that is blowing twice as fast, which is why locating wind farms in the windiest areas is so important.
        • If sunlight is more intense then a smaller area of collector will be needed and the return on the financial investment will be maximised.
    • Level of Technological Development
      • Many renewable technologies are not yet fully developed. This may be due to lack of investment or the long time period it takes to perfect developments.
        • In-stream tidal turbines are a relatively new idea that is gaining support as the disadvantages of tidal barrages are being fully appreciated.
        • Photovoltaic cells have a rather low efficiency at converting a low energy density source of energy into electricity.
          • This makes the output of a given area of panel rather low so they are not economically viable for most applications
        • Photothermal panels are well developed as they use relatively simple technologies that already existed.
    • Economic issues
      • A variety of economic factors have hampered the recent development of renewable energy resources
        • Since the industrial revolution, the advantages of high energy density fossil fuels have led to the development of equipment, such as vehicles and steam turbine generators, which cannot easily be adapted to run on renewable energy resources
        • The early development costs of fossil fuel technologies  have already been paid for and mass production makes manufacture relatively cheap
        • The social and environmental costs are rarely included in the economic costs of the energy industry. These could include habitat loss, reduced quality of life, acid rain, photochemical smogs and global climate change.


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