Sustainable Energy for the Future
Neil Detweiler
Biology Senior Seminar


In dealing with the needs of a growing world population, humans will need to develop a diverse array of sustainable energy sources and network them so that they compliment each other.


  1. Introduction
  2. Traditional Renewable Energy Sources
    1. Wind power
      1. Traditional windmills
      2. Modern wind turbines
    2. Hydro power
  3. Recently Developed Renewable Energy Sources
    1. Wave power
    2. Tide power
    3. Solar power
    4. Geothermal power
  4. Nuclear Power
  5. Moral and Ethical Issues
  6. Conclusion
  7. References

Introduction and Rationale:
One of the biggest problems that will be encountered as the global population expands is the need for more energy.  There are enough energy sources on this planet to supply power long into the future, they just need to be harnessed in a safe, efficient, and sustainable manner.  The sources of power that will be investigated are hydro, tidal, wave,  solar, wind, geothermal, and nuclear.  These renewable sources of energy will be evaluated for their cleanliness, renewability, economics, and reliability.

Traditional Renewable Energy Sources:
Hydro and wind power are two of the oldest forms of power used by humans.  Before electricity, mills were run by water wheels and wind turbines.  Historically, Holland is known for its windmills which were used to pump water and grind grain.  Early American settlements in the Midwest often included a mill powered by a river or stream which turned a turbine to grind grain.  Sailboats are also a good historical example of using wind power.  Wind and hydro power are still widely used in today’s world.  The beauty of these two forms of power is their simplicity and their cleanliness.  Neither of them produce a waste product of any kind, but they do have their drawbacks.  Hydro power has very significant effect on ecosystems in the river being damned, as well as in any body of water to which the river drains.  For example, damming of the Colorado River has led to habitat degradation in the Gulf of California.  The world’s most endangered cetacean, Phocoena sinus, is endangered because of this habitat degradation (Carwardine, 2007).

Wind power has evolved significantly since the days of traditional Dutch windmills.  Today’s wind power is harnessed by skinny-bladed turbines high up on poles or towers that convert the energy of the wind directly into electricity on the spot.  These turbines come in a wide range of sizes, and power companies install these large turbines in places that are ideal for wind generation.  Smaller units are available for anyone who has the money and a place to put it, people who install wind turbines on their farm or at their home can reduce their electricity bill by generating some of their own power.  Sometimes it is possible to make a profit by generating more power than you use.

Of the renewable technologies discussed in this report, wind power is the fastest growing.  The annual growth rate of wind power is 30% (European Wind Energy Association, 2004).  The cost of mass producing electricity with wind energy is very comparable to that of coal.  In 2006, the Energy Information Administration estimated the cost per megawatt hour for wind and coal to be 55.8 and 53.1, respectively (.  Given that the cost of producing wind energy does not depend on the price of a fuel should make it more stable.  As wind technology advances, it will get cheaper. 

The main issues with wind power are environmental, aesthetic, and timing related.  Aesthetically, wind turbines have a big impact because of their size and height, and the fact that they are moving.  They can drastically affect the scenery.  One negative environmental affect of wind turbines is that they tend to kill birds.  A human safety issue is the fact that aircraft will have more obstacles to avoid.  The timing issue with wind power is that windiness varies, and power may not be available when it is needed.  This underscores the importance of a good electrical grid that can distribute power from where it is available to where it is needed.

Hydro power is not quite as simple to set up as wind power.   The amount of power you can generate depends on the size of the stream or river that is being harness.  Large dams like the Hoover dam in Nevada are expensive to build, and there are environmental concerns.   Smaller water turbines can be installed, but they are not as common as small wind turbines.  There are many smaller dams that were created as cities and towns were developing in the Midwest, but are no longer in use for generating electricity.  Power companies have shifted electricity production to larger, cheaper power plants, often coal plants, but hydropower is by far the most significant form of renewable energy.  Of the renewable energy that the world produced in 2005, 58.23% was hydropower (Renewable Energy Policy Network for the 21st Century, 2006).  Although the use of hydropower is widespread, it is limited in its potential to expand.  New reservoirs take up lots of space.  They often displace established residents, human or otherwise.  New projects should be planned very carefully so that all of the effects are known.

Recently Developed Renewable Energy Sources:
Tidal and wave power are also technically forms of hydro power.  They are much newer than the traditional dam and turbine technique.  To get power from waves, buoys are used.  This is a very new technology, and it is not widely used.  The buoys have some sort of internal mechanism that allows them to convert the elliptical motion of the waves to generate electricity.  Many Danish, English, and Portuguese and other engineers have been trying to develop the technology.  There is quite a bit of energy in ocean waves, but it is a challenge to harness it.  Very complicated math is apparently involved.  The technology also is limited by the fact that you cannot surround a coastline with wave generators because boats need through.

Getting power from the tide is possible when you have large bays or other bodies of water that branch off from the ocean.  When the tide is coming in, the water runs one way, and when the tide goes out, the water runs the other way.  Large underwater turbines are placed in spots where the current is strongest.  These turbines are designed to generate power from water moving in either direction.  So to what mysterious force do we owe the power of the tides?  The moon!  And the sun a little bit too.  Tides come and go as the moon orbits around the earth, and to some extent, as the earth orbits the sun.

Much of the energy we use can be traced back to the sun.  The wind is driven by temperature variations that are caused by the sun.  Rivers and streams exist because of evaporation of ocean water by the sun.  Fossil fuels are the remains of ancient decayed plant and animal matter, most of which probably got their energy from photosynthesis.  Even a simple greenhouse is a way of harnessing the power of the sun.  The challenge that humans have been trying to overcome for the last century is how to efficiently convert solar radiation into electricity.

There are many strategies for capturing solar energy. Using oil as an intermediate is the strategy for one system.  A large field of mirrors direct a large amount of sunlight to a single central point where it heats oil, which then is used to drive a steam turbine.  This system is still in use at some solar power plants, but there is newer more efficient technology.  The most direct way to convert sunlight into electricity is with photovoltaic cells.  Photovoltaic cells have different layers of very carefully designed materials that capture the energy from photons and convert it into electrical potential with no mechanical devices involved.  These are a recent and still developing technology.  In 2005, only 0.42% of the world’s renewable energy came from photovoltaic cells(Renewable Energy Policy Network for the 21st Century, 2006).  One distinct advantage of solar energy is its relatively high power density(Vaclav 18).  This means that per unit surface area on the earth, more energy in the form of solar energy is available than energy in most other forms.  An environmental concern involving photovoltaic cells is the fact that they have cadmium in them, which is a toxic element known to bioaccumulate.  Also, like wind energy, solar power is dependent on the weather.  If the sun isn’t shining, the solar panel isn't making power.  Again, a good power grid is necessary to make the best use of this power source.

Using energy from within the earth is the idea behind geothermal energy.  There is a wide variety of technologies that fall under the category of geothermal.  One use of geothermal is for heating and cooling in the home.  Pipes can be run through the ground around your house and take advantage of the nearly constant temperature of the ground several feet below the surface.  Water or another liquid is cycled through the pipe and back to the house.  In the summer, the ground temperature is cooler than the outside air temperature, so the water can be used to aid the air conditioning.  On the contrary, the ground temperature is warmer than the outside air temperature in the winter, and so the water can be used to aid the furnace.  These systems often involve the use of a compressor, making them similar in theory to an air conditioning system.

Geothermal power can also be used on a larger scale to generate electricity.  This usually involves using energy from deep within the earth.  Greenland generates a large portion of their electricity using geothermal power.  In many places, it would be difficult to use geothermal power, because the outer crust of the earth is too thick.  In places where hot springs and other geothermal surface features are more prevalent, it is possible to harness the energy.  Very hot water  from underground is piped to the surface where it is either allowed to flash into steam and drive a steam turbine, or used to heat a second liquid with a lower boiling point which evaporates and drives a steam turbine.   Places where geothermal energy is available are generally places with more volcanic activity, or at least a history of volcanic activity.  One such example is Yellowstone National Park where there are abundant geothermal features, although it is not currently active volcanically.  In the past, however, there have been large eruptions.  Inside a National Park is probably not a suitable place for large scale power generation, however.  That is the problem with geothermal power; it is not widely accessible.

Nuclear Power, Sustainable?
Nuclear power derives its energy from a unique source: from the conversion of mass to energy.  Certain isotopes of some elements have a very unstable nucleus and are prone to breaking apart, releasing a large amount of energy in the process.  Typically these radioactive isotopes are not found in nature in high concentrations, though it is possible to concentrate them by centrifugation.  The most common element used in nuclear power generation is uranium, and there is enough uranium on the Earth to generate electricity for a very long time.  For this reason, nuclear power would seem to be as “renewable” as other renewable energy sources, but this does not make it sustainable.  The downfall of Nuclear power is the fact that when you concentrate these radioactive elements, they become very dangerous.  Radioactivity is very harmful to humans, and it takes great care and expense to protect ourselves from it.  The byproducts of nuclear power generation are radioactive for a for an incredibly long time, on the order of hundreds or thousands of years.  Unfortunately there is no known way to neutralize these byproducts.  Another safety concern is the fact that from time to time, nuclear power plants have meltdowns.  This is generally the result of human error, which is unavoidable.  When a nuclear power plant melts down, it is a major catastrophe.  Both immediate and long term damage is down to a large area surrounding the plant.  This Achilles heal could also be a target for terrorists.  The safety concerns are serious enough that many people are against the continued use of nuclear power plants.  Unless new innovations allow us to address these safety concerns, nuclear power faces a probable phasing out in the future.

Moral and Ethical Issues:
Americans have a huge affect on the world outside America.  By interacting economically with other countries, we are often encouraging them to live like we do.  If everyone in the world lived like us, it would be difficult to supply enough energy, and there would be even bigger pollution problems.  We have a moral obligation to be more efficient and to find better ways of supplying power than with fossil fuels.  Power generation occurs on an enormous scale; this makes it very important to carefully examine even the smallest issues with any given source of power.  As Christians, we are called to be stewards of the Earth.

There is hope for the future, even after we burn our last lump of coal, there will be sources of energy for us to exploit.  The key to a secure energy future, just like the key to a good economy, is diversity.  The idea that humans need to choose "the one" energy source of the future is false.  Each energy source has its strengths and weaknesses.  By having an intelligent electrical grid, we will be able to take advantage of a variety of energy sources that compliment each other.  We do need to be evaluating our options to make sure that they are safe and sustainable.  We may also need to become more efficient than some of us are today.  We need to develop a sustainable way of operating for a large and growing number of humans.


Carwardine, M. (2007, September 12). The baiji: So long and thanks for all the fish. New Scientist.

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European Wind Energy Association. (2004). Wind Energy The Facts (5th ed.) [Brochure]. Brussels: Author. Retrieved November 5, 2007, from

REN21. 2006. “Renewables Global Status Report 2006 Update” (Paris: REN21 Secretariat and Washington, DC:Worldwatch Institute).

Vaclav, S. Energy at the Crossroads. Retrieved October 25, 2007, from