Geothermal Power in Oregon-Part I

As the next installment in our continuing series on emerging renewable technologies, this post will examine geothermal energy, focusing on the status of Oregon’s geothermal development, as well as the benefits and limitations of geothermal power. Just like other emerging renewable energy technologies, such as wave power and biomass, geothermal can also be used to meet Oregon’s Renewable Portfolio Standard (RPS). Last week, Alex Sifford, a well-respected consultant on geothermal projects, gave CUB a briefing on the state’s interests in geothermal.

Intro

The term geothermal literally means heat from the earth. The earth is constantly producing heat at its core, which can be harnessed to meet both heating and energy needs. Naturally occurring instances of geothermal activity include hot springs, geysers, and volcanoes. Underneath the earth’s surface there are geothermal reservoirs, where heated water is trapped in the ground and can reach temperatures up to 350°C. To access this form of energy, wells are drilled into the ground that can extend over two miles deep. Depending on the geological structure and the amount of heat available, geothermal power can take many forms.

Geothermal reservoirs are grouped into three categories based on temperature. Low (less than 90°C) and moderate temperature (90°C -150°C) resources can commonly be found in “direct-use” heating buildings and district heating projects, or applied for industrial purposes. Hot water from geothermal reservoirs can also be used in agriculture and aquaculture. High temperature (great than 150°C) and some moderate temperature geothermal resources can be used to generate electricity.

There are three ways that geothermal resources can be converted to power. Existing geothermal power plants are predominantly flash steam systems, which extract hot pressurized liquid and turn it into steam to drive a turbine. A small number of geothermal resources are already accessible as steam. Rather than going through the flashing process, these can be used directly in a dry steam plant to produce electricity. Moderate temperature geothermal resources may not be suitable for flash steam plants, but can still be used to generate power through a binary-cycle plant. This type of power plant uses a heat exchanger to heat a secondary fluid, which vaporizes at a lower temperature. Some hybrid plants combine flash steam and binary systems to extract additional heat from geothermal resources. Since moderate temperature resources are more common and binary systems use reservoir water more efficiently, future geothermal power plants will predominantly be binary-cycle plants.

If geothermal resources are limited, the earth can still be used to create ground-source heat pumps. Since ground temperatures remain relatively constant regardless of seasonal changes in air temperature, the ground can be used to supply heat during the winter and cool buildings during the summer. Geothermal heat pumps do not need geothermal wells, and instead rely on piping fluid into the ground beneath or next to a building. Since no geothermal resources are required, ground-source heat pumps can be installed almost anywhere in the world.

Geothermal Resources in Oregon

In Oregon, geothermal exploration has occurred intermittently since 1959, leading to the discovery of many direct-use resources and some possible high temperature resources. Over the last 30 years, there have been several isolated attempts at power generation projects, but none are currently in operation. In 1982, two projects developed by Solar Power Systems were in operation, but both encountered technical difficulties and are no longer in operation. In 1995, plans for a 23 MW binary power plant in Pueblo Valley were scrapped after the developer Anadarko was unable to secure a power purchase agreement. Until recently, there has been very little activity in geothermal exploration.

There are an estimated 630 applications of direct-use geothermal in Oregon which collectively provide over 174,000 MWh of energy per year. A majority of the eastern two-thirds of the state contain some geothermal activity, and as a result a number of cities and towns use geothermal resources for heating, industry, and agriculture. The most notable system is in the City of Klamath Falls , which has a heating system that melts snow on bridges and highways and provides heat for downtown buildings. Overall, direct-use geothermal is well utilized in Oregon, but still has significant potential for further development. Many communities across the state could easily access known geothermal resources and are ripe for collocation opportunities. The Oregon Institute of Technology estimates that Oregon’s direct-use geothermal potential is 4600 MW over 30 years, and that as of 2007, only 1.4% of that potential is being utilized.

Currently, there is no electricity generated from geothermal sources within the Oregon, but two projects should soon change this. One project, located at Neal Hot Springs , is led by US Geothermal, Inc. and plans to sell its 26 MW output to Idaho Power Company starting in 2012. The second project is a joint venture between Nevada Geothermal Power and Ormat Nevada, Inc. to build a 30 MW plant at Crump Geyser. Nevada Geothermal Power is currently drilling exploratory production wells, and the project is expected to go online in 2013. Both the Neal Hot Springs and the Crump Geyser will use binary-cycle geothermal power plants.

Even with a combined 56 MW set to come online in the next few years, there is potential for Oregon to significantly increase its geothermal electricity production. The Newberry Known Geothermal Resource Area has recorded temperatures of 265°C in 1980, but lacks the steam or water to produce power with technology that is currently available. AltaRock Energy and Davenport Newberry are currently pursuing a new unproven technology called Enhanced Geothermal Systems (EGS) to build a power plant at Newberry. Outside of Newberry, there are very few known high temperature geothermal resources within Oregon. Other sites with high temperature resources may exist, but the extent of these resources will not be known until a developer drills a costly exploratory well to prove the site’s viability.

Part I on Geothermal Power in Oregon has given a brief introduction to how geothermal energy works as well as an overview of past, present and potential geothermal projects in Oregon. Part II will outline the advantages and disadvantages of geothermal power as well as give a brief summary of the future outlook for geothermal energy.

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