GEOTHERMAL ENERGY-CURRENT STATUS AND FUTURE POSSIBILITIES Coal
(lbs/MWh) Dry Steam Flash Binary Natural Gas
CO2 CH4
PM2.5 PM10 SO2 N2O
59.82
0.0000 - -
0.0002 0.0000
396.3
0.0000 - -
0.3500 0.0000
- - - - - -
861.1 2200
0.0168 0.2523 0.1100 0.1200 0.0043
0.5900 0.7200 18.75
0.0017 0.0367
Table 1. Comparison of Emission Levels of the Different Methods of Geothermal to Other Forms of Non-renewable Energy.
Figure 4. Carbon Dioxide Emission per Energy Method.
Geothermal ener- gy operational costs are lower than the costs associated with more traditional fos- sil fuel facilities. Once a geothermal plant is constructed, it is less capital intensive to keep it operational (Matek and Gawell, The Economic Costs and Benefits of Geothermal Power). Geothermal plants have no external costs related to the pur- chase or transportation of fuel stocks or the con- trol or management of emissions. Unlike fossil fuel produced energy, the cost of geothermal
energy’s basic raw material, heat from the Earth, is fixed. Good, But Not Perfect
Despite geothermal energy’s clean and renewable nature, there are several limiting factors that inhibit widespread reliance on it as a major player in the world’s total energy production. Geothermal energy currently accounts for less than one percent of the world’s energy production due in part to the difficulty of scalability and greater than average financial risk.
As with many real estate based businesses, geother- mal energy is all about “location, location, location.” Geothermal energy comes directly from heat radiating through the crust of the Earth and plant sites need to be placed where that heat is most accessible: where the crust is thin – near plate boundaries – or at hot spots, places where upwelling, near permanent mantle plumes are proximal to the surface. The more heat a plant can gather from the crust, the cheaper it will be to build and the more energy it can reliably produce.
In locations near plate boundaries such as California, the Philippines and Iceland, geothermal plants can be incredibly efficient. California generates more than five percent of its energy requirements from geothermal sources while the two island countries generate over 20 percent of their power needs (Duffield and Sass). In other parts of the United States, the western half of the
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country is higher in seismic activity than the eastern half. This leads to a warmer crust and a more suitable environment for siting geothermal plants. Note in Figure 5 that the distributions of geothermal plants are primarily in the western half of the country, where seismic activity is greater. Geothermal plants in Iceland, Japan, and California have long records of safe, reliable energy produc- tion in these and other seismically active areas (Major et al., 2007; Jousset et al., 2011).
The limited availability of hydrothermal activity also hinders scaling of geothermal technology. Unlike other power plants that use coal or nuclear energy, geothermal plants are bound to specific locations where heat is near the surface and readily available. For each proposed location, geologic surveys must be conducted to test the suitability of the site. These surveys quantify the extent of available heat and play a key role in final plant-site selection; however, the potential changes in land use may conflict with existing local economies as land owners may be reluctant to share existing infrastructure. As history has shown during the development of coal, hydro- electric, and (more recently) photovoltaics, the electrical distribution infrastructure will expand to accommodate new energy sources. Such trends currently are underway in the geothermal industry (Bosselman, 2011; Glassley, 2014; Braun & Hazelroth, 2015).
Similarly, the unique nature of each site poses a challenge to financing and cost projections. Due to site specific variations in heat flow, estimating the capital and long term operation and maintenance resource needs for a specific geothermal plant can vary greatly. These problems are not entirely unique to geothermal plants, but the challenges can serve as barriers to entry for widespread deployment of the technology.
Perhaps the most daunting concern related to geothermal scalability is the fact that other sources of energy dominant the market. This is due in part to the lesser-restricted (site) construction guidelines for other technologies, but mostly because of the relative production capacity. The majority of the world’s energy comes from coal, petroleum, and natural
Figure 5. Favorable Geothermal Zone and Plants in the United States.
Apr.May.Jun 2016 TPG 57
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