By Charlotte Helston
High-temperature geothermal power holds the promise of providing large quantities of cheap, carbon-light energy without the intermittency or land use issues that make other renewables like wind and solar problematic.
The heat for geothermal power comes from ongoing radioactive decay and primordial heat left over from the formation of the earth billions of years ago. The energy can be tapped anywhere on the earth's surface, though volcanically active regions make much more convenient access points to this underground heat.
A number of technologies have existed for almost a century to extract this virtually inexhaustible source of power, and today many countries in the world are investing heavily in developing high-temperature geothermal plants. Iceland, for instance, gets almost 80% of its electricity from geothermal power. Countries around the Pacific Rim are especially well placed geographically for high-temperature geothermal power, and the United States, Indonesia and the Philippines are world leaders in this field.
Oddly, British Columbia and Canada have no high-temperature geothermal power plants despite their proximity to the Pacific Ring of Fire. So far, all plans for development have become bogged down in permitting procedures and land use issues.
There are of course drawbacks to high-temperature geothermal power. The controversial practice of fracking is needed to access underground reservoirs of heat and it is suspected that this can potentially cause earthquakes.
Nevertheless many nearby countries continue to press ahead with this high-potential energy source, while British Columbia continues to have a moratorium on geothermal power development.
Geothermal energy arises from two primary sources: radioactive decay, and primordial heat created by compression during the original formation of the earth around 4.6 billion years ago.
- Radioactive Decay:
- Primordial Heat:
The decay of naturally-occurring radioactive species of elements, such as uranium-235 and thorium-232, in the ground below us, results in the generation of 860,000,000,000 gigajoules per year of heat.
Primordial heat, as the name implies, has existed since the creation of the earth 4.6 billion years ago when the energy and mass from colliding cosmic matter produced a planet. This smoldering piece of space debris began to cool from the outside in, creating the hardened "crust" upon which life and civilization was born. The solid outer layer acts as the cast-iron of the wood-stove, insulating and containing heat.
This primordial heat continues to flow from the earth's interior to its surface. This can occur through slow conduction through solid rock, and convective heat transport in areas with fluid interaction, such as water or magma. Much of this heat activity goes unnoticed by humans. It can also occur catastrophically, however, in the form of volcanic activity:
Geothermal energy is dependent on three things:
1) A large source of heat
2) A reservoir to contain the heat
3) A barrier to lock it in
4. A fluid to carry and transfer the heat
We know from the previous section that geothermal heat is produced in two ways; from radioactive decay, and from the primordial heat of the earth's core.
Let's look at the second and third requirements: a reservoir and a barrier.
Reservoirs are permeable, hot rock units, that, when surrounded by impermeable rock layers (the barrier), act as heat-storage containers. Geothermal reservoirs can be structurally similar to the reservoirs of oil and gas reserves.
Extraction of geothermal resources is conducted by drilling into these reservoirs. Sometimes, if the rock is porous, hot water is ready-made and waiting. This is known as a Conventional Hydrothermal Geothermal Resource. These sites are located in areas where magma has poked through the continental crust, creating convective circulation of groundwater. In the past, hydrothermal reservoirs have been the most common and economically feasible geothermal resources.
Other times, drillers find hot rock, but no water. In this latter scenario, a second well is drilled adjacent to the first. Water is injected down the new well and collected, once it has been heated, from the first well. This is known as an
Geothermal resources are used either for direct heating or for generating electricity.
Direct use systems use heat from low-temperature resources between 50°C and 150°C. The components of a direct use heat system are a source of heat (such as a well), a method of transportation from the ground to buildings (piping) and a disposal system (possibly reinjection of fluid into the well or a storage pond). Direct heating can, and does, provide heat for residential and industrial facilities. It is also often employed in commercial applications, such as greenhouses, fish farms and food processing facilities.
Electricity generation is achieved through the use of geothermal steam to drive turbines, which in turn power electric generators.
There are three geothermal power plant technologies being used to convert hydrothermal fluids to electricity. They include:
1. Dry Steam Power Plants:
This technology uses hydrothermal fluids (primarily steam) to directly drive a turbine, which then powers a generator that produces electricity. This is the oldest type of geothermal power plant, first used at Lardarello, Italy, in 1904. The Lardarello facility is still in operation today.
2) Flash Steam Power Plants:
Hydrothermal fluids above 182°C are sprayed into tanks held at considerably lower pressure than the fluid, causing some of the liquid to rapidly vaporize, or "flash". The vapour is then used to drive a turbine, which then drives a generator, thus creating electricity. Remaining liquid can be flashed a second time to extract as much energy as possible (and also eliminating wastewater).
3) Binary-Cycle (such as Organic Rankine) Power Plants
This technology involves two fluids: hot geothermal water and a second "working fluid" with a lower boiling point than water. Heat is exchanged between the two fluids, and the working fluid (usually a
Geothermal energy exists beneath all continents and oceans; however, the heat distribution is not uniform. Rather, the earth is made up of cooler regions and hotspots, like the
On a large scale, the intensity of this thermal energy increases with depth; the closer we get to earth's core (which is approximately 5000°C) the hotter it gets. A global average for earth's
Geothermal is being harnessed around the globe, from climatically cool regions like Iceland to tropical ones like Mexico. Worldwide, there are over 10,000 MW of installed capacity electricity generation, and 27,825 MW of direct heat produced from geothermal resources. Electricity production occurs in 24 countries, and direct heating in 72. The United States, the Philippines and Indonesia comprise over half the world's geothermal generating capacity, at 3,903 MW, 1,904 MW, and 1,197 MW respectively.
In Iceland, over 81% of the electric power and 95 percent of home heating is produced from steam and hot water that occurs naturally in volcanic rocks. Iceland produces enough geothermal energy to have the highest portion of its energy use provided for by geothermal, but not enough to rank as one of the top global producers in absolute terms. The country of Iceland resides on a highly unique geological foundation ideal for geothermal energy extraction.
Systematic investigation of geothermal resources in Canada commenced in 1973, when the worldwide oil crisis spurred countries to seek alternatives to imported oil. A formal program concluding in 1986, without leading to any major development projects. Momentum didn't pick up again until the early 2000s, when oil prices again began to rise.
Areas in Western Canada display strong prospects for geothermal energy extraction, and there have been extensive studies at Mount Meager, north of Whistler, BC. Electricity was successfully produced there during testing in the past, but as of 2010, the facility was not operational.
Two projects are proposed for construction in the North West Territories. The Fort Liard demonstration project would generate 1 MW of electricity and 1 MWh of heat. The project is a joint venture between Borealis GeoPower and the Acho Dene Koe First Nations of the area. The project has qualified for $10-20 million dollars in funding from the Federal Clean Energy Fund, and Borealis estimates that the plant will be online by 2013.
The Con Mine District Heating System in Yellowknife has also qualified for financial support from the Clean Energy Fund ($14.1 million) though a lack of support from city residents in a March 2011 referendum means that locals are unwilling to borrow funds for the project. The proposed heating system would produce 52,000 MWh/yr which could be used to heat nearly 40 commercial buildings in downtown Yellowknife, offsetting ~7.5 million litres of heating oil annually.
A pilot project to test the viability of electricity and heat production through the use of existing oil and gas infrastructure is underway in Swan Hills, Alberta. Various direct heating projects are also in development, including a demonstration for a greenhouse in Chilliwack, BC, and a plastics factory in Springhill, Nova Scotia.
According to the Canadian Geothermal Energy Association, numerous geothermal projects are currently underway. See a full listing of Canadian projects here.
The numerous hot springs found around the province point to the presence of high heat and energy geothermal deposits. CanGEA, referencing a 2007 study by Dr. Mory Ghomshei from the University of British Columbia, estimates the province's geothermal resources to be between 3,000-5,000 MegaWatts. Currently, the United States, global leader in geothermal energy, produces 3,903 MW from this source.
The Coast Mountains bear Canada's richest potential sources of geothermal energy. Here, just a few kilometers below the earth, magma rises with temperatures of approximately 200-300°C. These reservoirs could be used in heating, or in producing electricity through the use of steam-driven turbines.
A proposal for Mount Meager, 70 km northwest of Pemberton and within the Upper Lillooet Provincial Park at the headwaters of the Lillooet River, might produce enough electricity for over 90,000 households a year, estimates Green Energy BC.
North Meager or Pebble Creek, and Mount Cayley and Mount Garibaldi have also been explored. North Meager is likely fed by the same subterranean source as South Meager. It is speculated that North Meager may have more favourable lithology than South Meager, in terms of permeability.
Canada has been slow to advance development of known geothermal resources. It wasn't until March, 2004, that the BC government began accepting bids from companies proposing to develop geothermal resources in the Meager Creek and Kinbasket Lake regions. In June 2004, the BC government approved drilling permits for two deep production wells to assess the commercial viability at Meager Creek. At that time, the lease went to Western GeoPower, but it has since changed hands and is now held by American corporation Ram Power.
Ram Power has expressed that the Mount Meager site is a low priority and has not displayed efforts to develop it.
These developments, especially the transmission line, are strongly opposed by local First Nations who see the development as an infringement upon their traditional land rights to the area. The site is mostly set on traditional Lil'wat Nation (Mount Currie Band) territory, but other bands, such as the N'Quatqua First Nations, may be affected as well. The highly contested transmission line would link the Meager power plant to the B.C. Transmission Corporation (BCTC) system. The route preferred by developers runs through the Pemberton Valley, of which a substantial portion belongs to the Lil'wat First Nations. Alternative routes include the 80 km stretch through the Upper Lilouett and Birkenhead Valley, which would tie in to a substation at Poole Creek, and the 80 km route through the Hurley River valley, which would be more costly as it would require an upgrade of BCTC's local line. Both alternatives would use mostly Crown land, aside for some 4-5 km sections of unlogged forest.
According to BC MEMPR Titles Division, geothermal land tenure requests include the following land use types:
- Parks, protected areas, conservancies, recreation areas, ecological reserves
- Located within the Muskwa-Kechika Management Area
- Federal lands including Indian Reserves
- Areas with existing geothermal or petroleum and natural gas tenure
Geothermal legislation in BC requires that potential parcels of land go through a referral process, during which First Nations, local government and other agencies (such as environmental organizations) are consulted.
The Geothermal Resources Act of 1982 (which replaced the original legislation of 1973, which was faulty due to an absence of leasing regulation, and too open a definition) defines a geothermal resource as:
The act does not include control legislation for overdevelopment, such as restrictions on the rate of production to ensure sustainable exploitation.
In 2008, the BC government placed a moratorium on geothermal permitting applications and established a
It is uncommon for renewable energy markets to grow and compete with conventional markets without the support of government funding and policy-making. For nearly 25 years, geothermal science has not been funded by the Canadian Federal Government.
The BC Sustainable Energy Association, under its "Social, Economic & Political Matters" section suggests policy changes here to promote the use of high-temperature geothermal energy in BC.
Once a geothermal system is in place, and operating sustainably, geothermal heat is always available. Oil, gas, coal — these are finite resources. Solar, wind, wave — these are dependent upon the weather. Geothermal provides a predominantly carbon-free, secure, and continuous source of energy. Furthermore, it has one of the lowest levelized unit costs of any energy type.
Geothermal power requires no fuel except for pumps, and is therefore immune to fuel cost fluctuations. Capital costs are significant, sometimes up to $4 million per MW, depending on the size of the power plant, and the surrounding geography. Drilling accounts for over half the costs, and exploration of deep resources entails significant risks. The substantial up-front costs of drilling are risky; after spending millions on exploration, resources may be unfit for exploitation.
Once running, though, the high capital costs are neutralized by miniscule fuel costs and low operation and maintenance costs over the facility's lifetime.
The Geothermal Energy Association, referencing a 2007 report by the California Energy Commission, estimates the generation costs for a 50 MW geothermal binary plant at $92/MWh and $88/MWh for a 50 MW dual flash geothermal plant, which over the lifetime of the plant can be competitive with a variety of technologies, including natural gas. According to the California Energy Commission, natural gas costs $101/MWh for a 500 MW combined cycle power plant and $586/MWh for a 100 MW steam plant.
Erecting transmission lines where they do not previously exist poses another financial challenge. Roughly, 1 km of transmission costs $1 million, and 1 km of transmission can be necessary for every MW of power generation. With most geothermal sites located in remote areas, quite often accessed by logging roads, the costs of building transmission lines can add significantly to the up front costs.
The Canadian Geothermal Energy Association claims that tapping into our country's geothermal resources could create up to 9,000 permanent jobs, as well as 30,000 manufacturing and construction jobs nationwide. More site-specifically, the Clean Energy Association of BC estimates the South Meager Geothermal plant, if developed, would employ between 3-40 people in full time positions. Temporary jobs emerging from the construction of the plant, substations, transmission line and other facilities, could employ 250-350 personnel over an estimated two-year construction period.
Iceland, whose geothermal energy developments already supply at least 81% of the country's electricity, has announced plans to export geothermal energy to other European nations by channeling it under the ocean. The plan proposes to construct a giant cable that would lie on the seabed and transmit as much as 5 billion kWh/y of electricity, powering a potential 1.25 million houses. Learn more here.
IX. Environmental Impacts
Geothermal energy production can be considered a renewable resource, under specific conditions.
In his book Sustainable Energy — without the hot air, David MacKay uses the metaphor of a straw and a crushed ice drink to explain the concept of, as he puts it, "sustainable sucking" in geothermal energy extraction.
A straw inserted into the beverage represents the well we drill to reach the geothermal reservoir. If we slurp up the liquid at a rate faster than it can replenish itself, we are sucking unsustainably.
"Sucking" heat energy in conventional hydrothermal resources at the natural rate heat escapes anyway, would indeed be sustainable.
Using Enhanced Geothermal Systems to pump water into previously dry, hot rock units, would also be sustainable so long as the rocks were given time to "recover" and heat back up before more liquid is injected. Sarah Kimball furthers this argument: "If economic exploitation of geothermal fluids exceeds the natural replenishment rate there may be depletion in the heat and/or fluid content of the reservoir."
It must be understood that natural geothermal features, such as fumaroles, as well as human developed geothermal wells, emit carbon dioxide, hydrogen sulfide, ammonia, nitrogen and methane. In comparison to other energy sources, however, these emissions are negligible. Fewer nitrogen and sulfur emissions mean less acid rain, and reduced CO2 emissions mean a more stable ozone layer. The BC Sustainable Energy Association remarks that a 100 MW geothermal plant will reduce CO2 emissions by 600,000 tonnes a year, and nitrogen and sulfide emissions by 120,000 tonnes annually compared to a natural gas plant of equal size.
In a geothermal power plant, much of the activity occurs underground, which reduces its land-use impact substantially. Studies have placed geothermal's land requirements at 1.0 to 13.9 km2 per TeraWatt hour per year. This compares with 27.5 to 99.3km2/TWhr/yr for oil.
Cooling is a necessary step in the geothermal power conversion process. In order to condense the vapour feeding the turbine, a cooling mechanism must be employed. Cooling towers also safeguard against possible overheating of turbines. There are two types of cooling systems in use today: water cooling and air cooling. Most geothermal power plants — in fact most power plants in general — use water cooling systems. A geothermal steam power plant may consume as much as 5,300 litres/MWhr (though it may withdraw as much as 7,570 litres).
Geothermal fluids can contain high levels of arsenic, mercury, lithium and boron due to contact with the high temperature rocks in depth. If this waste-water is not disposed of properly, it could leech into lakes and rivers where ecosystems and safe drinking water can be damaged. To avoid contamination of surrounding water systems, the waste water is usually pumped back into the geothermal reservoir where it can help replenish the system.
Land subsidence is another land issue being raised by residents near geothermal developments. Subsidence describes the slow sinking of land, which has been linked in some areas to geothermal plants. This is from the geothermal reservoir decreasing in pressure as the fluid is pumped out. The largest known case of subsidence was Wairakei, New Zealand where the centre of the subsidence was 14 meters lower than initially and was sinking at a half a meter a year.
Hydraulic fracturing, or
Geothermal fracking is not reported to use any dangerous additives, however, it presents another concern: induced seismicity.
Because the best geothermal resources are found in areas of high tectonic activity, earthquakes, and the possibility that they could be sparked by drilling and fracking, must be considered.
High pressure injections and trickling wastewater open up and lubricate old fault lines, allowing them to shift and trigger earthquakes. In a 2009 speech, Calgary geologist Jack Century, president of J.R. Century Petroleum Consultants Ltd., explained that the human activity of altering the amount of fluid in the earth, changes the pressure where fault-lines exist, causing them to move.
A geothermal project in Basel, Switzerland in 2006 triggered a 3.4 Richter Scale earthquake that damaged buildings in the surrounding area. Read more about it here.
It's hard to know if geothermal development in a given area will result in induced seismicity. A good indicator is the region's history. There is no question, however, that once an earthquake is "turned on", there is no way to turn it off. Are the potential hazards of induced seismicity worth the availability of clean, renewable energy? The impacts of earthquakes can be treacherous, from devastated infrastructure to damaged wildlife habitats.
It is important to note that the risks of hydraulic fracturing are already a reality in the oil and gas industry. Some might say if we're going to "frack", we may as well do it in the name of clean, renewable energy. For examples of earthquakes induced by fracking in Canada and the United States, see this article from the Canadian Centre for Policy Alternatives.
As with all energy resources, it is essential to consider the land in direct use, as well as the surrounding area affected by the activity. In the case of the Mount Meager site, it is important to think about the impacts such development would have on the Upper Lillooet Provincial Park — its natural landscape and wildlife. Noise pollution remains an unavoidable by-product of geothermal construction projects that could affect animal populations.
However negative some of geothermal's effects may be, they are in no way unique to this type of energy resource. Oil, natural gas, and coal all account for massive habitat destruction, noise pollution, and shrunken nature reserves, not to mention greenhouse gas emissions.
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