New horizons: Canada’s untapped geothermal energy potential

The following is an edited excerpt from the Geological Survey of Canada’s report Geological energy resource potential of Canada. To download the full report visit http://geopub.nrcan.gc.ca.

Concerns over climate impacts of carbon-based fuel emissions, projected exponential growth in energy demand, as well as debate over long-term supplies of conventional oil have lead to growing interests in increasing renewable and clean energy supplies. A switch to more renewable energy will likely involve using numerous resources such as solar, wind, hydro and geothermal. 

Of these, geothermal energy has several advantages that make it an attractive energy resource. The first is its very high capacity factor (actual output versus generation potential) relative to other renewables. This allows geothermal to provide reliable base-load energy supply for electrical generation. 

Globally, geothermal energy has also shown to be a cost-competitive source of energy. Along with its low carbon footprint and minimal environmental impact, there is great potential for geothermal energy to become a significant contributor to the global energy market.

Geothermal energy production has shown global increase and for some countries it now forms a significant proportion of electrical supply. In the U.S. alone, electricity generation from geothermal sources totalled 2,564 MWe (or 18,000 GWh) at the end of 2005, making the U.S. the leader in total geothermal energy production. As of October 2009, this number grew to a total installed capacity of 3,153 MW with a 26% annual growth rate for new projects. 

The 188 projects currently underway in the U.S. are expected to provide another 7,000 MW of baseload power capacity to 15 states, feeding the energy demands of about 7.6 million people and replacing the total power used by coal-fired power plants in California. Current geothermal energy production in the U.S. already displaces consumption of 60 million barrels of oil
per year (about 29 million tonnes CO₂ emissions per year).

While geothermal energy has been developed extensively in the U.S. and other regions, it has not been taken advantage
of in Canada. Currently there is no electrical generating capacity in Canada. However, based on the last estimate in 2010 there is 1,126 MWt or 2,010 GWh of direct use installed. 

Shallow heat exchange systems are rapidly gaining interest in Canada, growing at an annual rate of 10-15% since 2000 and recently as high as 50%. There were an estimated 55,000 geoexchange units installed in Canada in 2010. This compares to a global installed capacity of nearly 76,000 GWh of direct use and a global annual growth rate of 10% in about 70 countries. More than half of this energy was used for space heating, and another third for heated pools. The remainder supported industrial and agricultural applications.

The now defunct National Geothermal Program (a Canadian government research program that ended in 1986) demonstrated that Canada has a geological environment favourable to geothermal development. This program defined high temperature
resources suitable for geothermal exploration and development, particularly in British Columbia, the Yukon and the Northwest Territories. 

Medium- and low-temperature geothermal resources were also defined within sedimentary basins and abandoned mines throughout Canada. Pilot projects drilled at Meager Creek, B.C., and Regina, Sask., further proved that geothermal power production in Canada is feasible. 

Now 25 years since the program ended, advancements in technologies have further increased the economic potential of these geothermal resources.

Geothermal energy 101

Geothermal energy is derived from heat in the Earth’s interior. The Earth’s heat is generated dominantly by radioactive decay of three key elements, uranium, thorium and potassium, in addition to primordial heat related to the original formation of the planet. This internal heat flows naturally to the surface by conduction and creates a gradient where temperature of the solid earth rises with increasing depth. 

In theory, geothermal energy potential is present below the entire surface of the Earth. In practice, however, special geologic conditions are required for geothermal energy to be economically exploited.

For a geothermal resource to become an economic supply of energy, three main factors are required: high temperature rocks within economic and technological drilling depths, a carrier fluid that can transport heat energy to the surface and a permeable pathway through hot rocks that the carrier fluid can move through. While these represent underlying geological controls on the economic feasibility of geothermal development, technology is progressively reducing these barriers. New technology is increasing drilling depths, enhancing the ability to induce flow systems through rocks where the natural permeability is too low, and lowering the temperature of the resource required to generate electricity.

This has progressively increased feasible depths to produce geothermal power and broadened the geological conditions in which geothermal development is possible. In addition, new heat exchange technology has progressively lowered the temperature of a resource required to produce electricity. These advancements have significantly increased the geologic environments where geothermal resources may be developed.

Canada’s potential

Canada has enormous geothermal energy resources that could supply a renewable and clean source of power. There are many constraints, however, in using this energy resource, including geological, technical and regulatory issues. 

Several projects are currently being examined by industry and government to develop electrical potential in Canada. A key economic constraint for these projects is the high risk of exploration due to the costs of deep drilling. The cost of delivered geothermal power is projected to decline and be competitive with coal-fired production within the next 15 years, given current
levels of technology.

Canada’s in-place geothermal power exceeds one million times its current electrical consumption. However, only a fraction of this total potential could be developed. Much of the resource lies beyond current drilling technology, outside of areas served by high-capacity transmission lines, and at some distance from load centres. Nonetheless, the available high-grade geothermal resource is considerable. 

High temperature hydrothermal systems can be brought on line with proven technology. Many of the tools required to bring geothermal energy to full realization, however, are not commercially proven to date and require further research and technology development. 

We can expect a strong learning curve and price response as geothermal energy is developed while other energy sources such as coal and nuclear will begin to see fleet and capacity retirements.