In Part 1 of this series on “Solving the World’s Energy Problem,” I made the case that fossil fuels are finite and must ultimately be replaced. Biofuels are a suitable substitute for fossil fuels, as both fossil fuels such as coal and oil, and biofuels such as alcohols and biodiesel, are essentially equivalent: both are energy from sunlight stored in a concentrated form. However, since our capacity to produce biofuels is unlikely to ever be at the level to replace more than a fraction of the fossil fuels now in use around the world, the development of alternative energy technologies is essential to enable human civilization to replace fossil fuels at some point in the future. Part 2 focused on possible alternative energy technologies that were based on converting energy from the sun into usable energy. Included on the list were solar heating technology, solar photovoltaic power, and wind energy.
But in addition to energy from the sun, there is another source of energy that could help fill the energy gap created by the reduced availability of fossil fuels. This other possible source for sustainable, renewable energy is energy derived from the earth itself.
There are three earth-generated technologies that, I believe, can serve as large-scale energy sources.
The first technology is geothermal energy. Geological formations that give rise to volcanoes and hot springs can be tapped to produce enormous amounts of energy. Accessing geothermal energy is not easy, as it requires drilling deep into the earth. But once accessed, geothermal energy is available continuously 24/7 regardless of the weather. In this way it is a far more reliable and predictable energy source than solar or wind energy. And while I suppose that geothermal energy is finite in the strictest sense since earth has a finite size, the amount of energy available to the world from geothermal sources is so large as to be without practical limits.
The second technology is one that is vastly underexploited in my opinion: the geothermal heat pump for heating and cooling. The design of geothermal heat pumps takes advantage of the relatively constant temperatures in the ground below about 6 to 10 feet. If you have ever been in a cave, you understand what I am talking about. Underground, the temperature almost everywhere on earth is a relatively constant 55 degrees Fahrenheit (about 12-13 degrees Centigrade). This is as true of Alaska as it is of the Arizona desert. Therefore, it is possible to use the earth as a source of heat in the winter and as a source of cooling in the summer. The heat, or cooling, from the ground can be transferred to the home by circulating a fluid through pipes buried at the appropriate depth and then into a heat exchanger inside the home. While geothermal systems require an additional energy source for heating in the winter months, by providing a constant base temperature of 55 degrees, geothermal heat pumps can decrease the amount of additional energy required by a significant amount. As a sustainable energy source for the heating and cooling the home, a geothermal heat pump system is ideal.
A third option, at least for certain coastal regions, is tidal energy. As an example, Alaska has some of the world’s largest tidal fluctuations. Because the water moves so swiftly in and out of the inlets when the tide fluctuates, the flow of water offers a predictable source of energy that can be harvested with turbines that are turned by the water flow. There are environmental issues related to the location of turbines, to be sure, and the use of tidal energy is limited to coastal areas. But for certain regions of the world tidal energy offers a viable energy solution.
Taking advantage of the large amount of energy available from the earth in the form of geothermal energy and tides offers a way to replace fossil fuels over the intermediate term. Combined with expanded use of biofuels and better technologies for capturing and using the energy from the sun, I can envision a time in the future when fossil fuels will no longer be needed. They will be entirely replaced by alternative, renewable energy sources that are cleaner and cost effective.