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Case Study

Solar power

8.3.1 Describe how solar power can be harnessed for use in domestic products.

Consider active solar collection and various arrangements of photovoltaic cells (PVs), for example, small individual cells on portable equipment, use of PVs in sustainable building design for hybrid systems, incorporation of PVs into roof design to enhance the sustainability of buildings and also doubling as shelter over car parking areas.
  • Solar powered calculators are a good example of a widely used domestic product run by solar power.
  • In housing systems solar power is used to heat the water pipes which are conveniently painted black to absorb the intensity of the sun, however this only proves efficient high temperature areas.
  • With time domestic products are implementing solar power into their design for consumer convenience. An example of this would be the implementation of solar power in back packs, this enables people to charge their cellphones, laptops, etc...

8.3.2 Identify the advantages and disadvantages of solar power.

Consider set-up costs, running costs and maintenance, and continuity of supply.
  • Initially high set up costs, low running costs and minimal maintenance. No power on cloudy, rainy days or at night

8.3.3 Describe the design of a solar cooker.

A solar cooker is a simple machine that focuses the rays of the sun into a small area where they can be used to heat food. The sunlight, both direct and reflected, enters the solar box through the glass or plastic top then converting the sunlight into heat energy. This oven uses no power, making it easier to use in areas where electricity and fuel are scarce. Solar cookers work by using parabolic mirrors to concentrate the light at a focal point and heat up that point. This works because every parabola has a focal point at which all lines bouncing off the parabola will eventually reach. The box uses the greenhouse effect and traps the heat inside making temperatures high and sufficient enough for cooking.

8.3.4 Discuss the importance of solar cooking in sustainable development.

In some rural areas, for example, Nepal, traditional cooking methods involve the burning of biomass fuels and result in indoor air pollution, which is one of the four most critical environmental problems in developing countries. Women and children are more likely to be exposed to indoor air pollution as many women in developing countries spend hours per day cooking near an open fire often with a child strapped to their backs. Indoor air pollution can damage lungs, contributing to acute lower respiratory infections, chronic lung disease, lung cancer, asthma, low birth weight and heart disease. Collection of wood and other biomass fuels contributes to deforestation, with impacts on the water table.

Solar cooking is a different way to cook food by using natural solar energy rather than non-renewable resources. The purpose of this is to be useful to people, while simultaneously preserving the environment. A helpful video on this topic can be found at http://vimeo.com/7386533.

Another helpful link on this topic: http://cat.inist.fr/?aModele=afficheN&cpsidt=2936630

Energy and transport

8.3.5 Compare individual and mass transport systems for sustainable development.

For development in urban areas, mass transport systems are more likely and feasible. A shared vehicle is more efficient than a private vehicle, considering today's oversized cars and light trucks. It is always the green move for an individual to take existing mass transit over their cars, because the transit is running anyway, so there is no incremental cost for carrying one more passenger. USA Transit efficiency, portrayed in the picture below, can be made greener, reversing the trend of poor efficiency, but transit budgets are planned on decade scales. Ironically in Europe, transit is 2.5 times more efficient, and in Asia, 4 times more efficient, due to their more efficient vehicles.

Advantages to mass transit, other than energy efficiency, are:

  1. Provides cheap transportation to those who can't drive or can't afford to, such as children, the elderly and the homeless.
  2. Reduces congestion at rush hour since without transit, roads could never handle the commuter loads in many areas, and would get more inefficient due to heavier congestion.
  3. Reduces the need for parking and allows efficient one-way trips.
  4. It's generally safer against accidents than car travel
  5. Mass transit use electric motors, which moves pollution out of cities and over to power plants.

Further Reading: http://www.templetons.com/brad/transit-myth.html

8.3.6 Discuss the barriers to transition from individual cars to mass public transport systems.

Consider convenience, flexibility, systems integration, for example, park-and-ride systems.
  • People in general are unwilling to give up the luxury of a previously purchased automobile, this impedes the progress of governments trying to establish a successful transport system.
  • People are also unwilling to ride public transport because it does not guarantee that they will get to were they want to be on time, this is due to the fact that public transport becomes very inefficient when congestion is prevalent. However some countries are working around this by creating secluded sections of road for public buses which prevent them from slowing down during congestion, this privilege increases the amount of people who use public buses.
  • One major factor that contributes to why people tend not to use public transport is timing, most people do not like to worry about when they have to be ready to ride the bus, but they would rather take their time and use their auto-mobile whenever they are ready.
Park and Ride Transportation system

Wind energy

8.3.7 Identify the advantages and disadvantages of small-scale and large-scale wind energy generating plants.

Consider small-scale wind energy generating systems, for example, for isolated houses, and large-scale wind energy generating systems for communities and feeding into the national grid.

When making a large or small scale wind energy farm, certain advantages and disadvantages can be found.

Advantages:

  • When discussing a large scale wind farm, the advantage is the fact that with a large number of wind mills, a decent amount of electricity will be generated that could be used to power communities.
  • high capital cost on large scale will take a shorter time to recoup
  • One advantage to creating a small scale generating plant is that the energy may be harnessed and used to power a home or certain parts of a home.

Disadvantages:

  • The problem with making a small scale wind energy generating plant is the fact that there is not enough space to install enough windmills to create a substantial amounts of electricity.
  • high capital cost on small scale will take time to recoup
  • For large scale farms a lot of land is needed.
@ Zafarana, Egypt Home wind power

8.3.8 Discuss the issues associated with the siting of large wind farms.

Consider impacts on the environment; noise and visual pollution; community lobbying and “not in my back yard” (NIMBY); who pays for the developments; onshore and offshore developments.

Environment:

  • Large footprint, small power output. Industry rule of thumb has been that a conventional 1.5 MW turbine needs a turbine spacing of roughly 40 acres of cleared land/turbine to avoid wind turbulence interference. AWEA.org believes 75 acres/turbine required for larger new turbine designs. To displace energy from New England’s smallest coal unit (Somerset) would require 167 turbines covering 22 miles of mountain ridge line. As turbines have gotten larger (up to 3.6 MW offered), minimum spacing requirements have also increased. Need spacing of roughly 8-10 blade lengths (4-5 rotor diameters) between turbines. Newer larger model designs may require spacing equivalent to 75-100 acres/turbine.
  • Wind power — Green technology but a higher cost alternative

Who pays for the developments

  • At ENC-WEC shows the financing sturture.
  • High capital cost:
    • Project capital costs have been rapidly escalating due to high turbine demand, weak dollar and rapid increases in labor, materials and supplies. Capital costs have escalated to $2,100-2,400/kW
  • Heavily dependent upon large ratepayer & taxpayer subsidies and mandates to compete against conventional electrical power generation sources

Noise and visual pollution; community lobbying and “not in my back yard” (NIMBY)

Onshore and offshore developments

  • Offshore have higher capital costs
    • are larger
    • therefore average cost of production is lower
  • Wind speed
    • tends to be stronger offshore
    • produce more electricity
  • placed away from communities
    • no affect with regards to visual or noise pollution
    • no lobby groups

References

Numbered list and italicised paragraphs are excerpted from Design Technology: guide. Cardiff Wales, UK: International Baccalaureate Organization, 2007.

Images are clickable links to its location.

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Page last modified on November 11, 2013, at 07:11 PM