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Geothermal power, which uses the Earth's natural heat to produce electricity and heating services, is increasingly being recognized as a valuable resource by policymakers (Source: Energy Conservation Future).
Hydropower and geothermal technologies are some of the oldest and longest-standing renewables in use today. In 2011, the total capacity and use of both technologies continued to increase. The two technologies, however, are at very different stages of deployment. By year-end 2011, global installed capacity of hydropower reached 970 gigawatts (GW), roughly 2.5 times greater than capacity of all other renewable power sources combined. By contrast, geothermal installed capacity reached a new high of 11.2 GW as of year-end 2011. While overall capacity continued to increase, consumption growth slowed for both technologies compared to recent years with each growing at reduced rates not seen since the early 2000s.
The majority of geothermal power is found in a select group of countries, although capacity has now been developed in 24 countries worldwide. The United States continues to lead all others, accounting for 28 percent of geothermal power capacity. Beyond the U.S., only three other countries had over 1 GW of capacity installed as of May 2012. Geothermal is increasingly attracting the attention of policymakers and project developers with new projects under development or consideration in an additional 70 countries. Though expanding, geothermal sources accounted for less than 1 percent of global electricity production in 2011.
By contrast, hydropower represents slightly above 6 percent of total primary energy use and 15 percent of electricity production worldwide. China, Brazil, the United States, Canada, and Russia are the global hydropower leaders, together accounting for over 50 percent of all installed capacity. China, Vietnam, Brazil, India, and Canada accounted for 75 percent of all new installations, with China alone representing nearly half of all new capacity added in 2011.
Despite the potential for inexpensive, low-emission power generation, hydropower is not without its significant faults, specifically in respect to the development of large-scale projects. The damming of rivers to create the reservoirs needed for large-scale power generation is severely disruptive, harming both animal and human populations. In many cases, hydropower projects have led to the displacement of local populations and the adverse altering of downstream conditions, while building hydropower plants has its own significant emissions impacts. Despite these concerns, many new developments continue to occur in countries such as Brazil and China, among others.
There are a number of significant benefits associated with the development of both technologies. Small hydropower (SHP) offers similar advantages to larger-scale installations while lessening many of the negative impacts. Furthermore, SHP can be an important tool for expanding energy access.
Likewise, the cost and reliability of generation from both hydropower and geothermal power plants is very competitive with other renewable and non-renewable generation sources. Differing by size and technology, geothermal power can be generated for under 6 cents per kWh, while hydropower generation can be as cheap as 2 cents per kWh.
The reliability of generation provides another unique benefit of each technology, mitigating the variability that plagues certain renewable energy sources, such as solar and wind, which can pose a challenge when looking to integrate them within existing power systems. By contrast, both hydropower and geothermal power systems rival fossil fuel and nuclear generation in respect to their potential to provide baseload power, with geothermal power plants operating at capacity factors of upward of 90 percent in certain cases.
Both hydro and geothermal have additional uses besides power generation. Hydro is increasingly being used as an energy storage solution through the development of pumped storage hydropower. Geothermal technologies are particularly well suited to providing renewable heat energy. Geothermal heat installations are in operation in 78 countries, including Iceland, which sources 90 percent of its heat from its geothermal resources. The power and non-power sector uses of both geothermal and hydro technologies are important to the ever evolving global energy sector.
Evan Musolino is a Research Associate with the Climate and Energy Program at Worldwatch Institute.