Geothermal Energy Production In Ireland

Abstract

Among the various new and renewable energy sources, geothermal energy is known to be one of the clean energy without smoke and also without environmental hazards. Although it’s importance is realised long back in other countries, it’s exploitation is still far away in our country mainly due to lack of knowledge on the deep subsurface structure and deep drilling technology in high pressure, high temperature regions.

Geothermal electricity production is in operation in 24 countries worldwide and while it offers a more dependable source of power than solar and wind - since it keys into the constant energy coming from within the earth rather than the inconsistent energy from the elements around the planet - it is limited geographically to areas where access to geothermal sources in possible. While geothermal energy currently supplies less than 1% of the world's total energy demand, it has potentially to contribute significantly to climate migration, and become a key part of the diversified renewable energy infrastructure.

Introduction:

Geothermal Energy Production:

Geothermal Energy:

The name geothermal comes from two Greek words: ‘geo’ means ‘Earth’ and ‘thermal’ means ‘heat’.

Geothermal Energy is a way of generating heat and electricity from hot underground rocks. This form of power generation does not create pollution, and is renewable (as long as we do not extract too much, or the rocks cool down). However, we can only use this method to generate our power in certain places in the world, where suitable hot regions are near the surface.

Generation of Geothermal Energy

Geothermal electricity is electricity generated from geothermal energy. This electricity generation is currently used in 24 countries, while geothermal heating is in use in 70 countries. The conversion technologies are dry steam, flash, and binary cycle. The type of conversion used depends on the state of the fluid (whether steam or water) and its temperature. Dry steam power plants systems were the first type of geothermal power generation plants built. They use the steam from the geothermal reservoir as it comes from wells, and route it directly through turbine/generator units to produce electricity.

Currently existing geothermal energy production technologies may be categorized accordingly:

· Direct Use

· Electric Power

· Geothermal Heat Pumps

Direct Use:

In areas near geothermal reservoirs, hot water or steam is piped directly to the process requiring thermal energy. The below figures shows the geothermal reservoir sketch and direct use applications worldwide.

In areas near geothermal reservoirs, hot water or steam is piped directly to the process requiring thermal energy.

Electric Power:

Natural steam from the production wells power the turbine generator. The steam is condensed by evaporation in the cooling tower and pumped down an injection well to sustain production.

Source: Slide 37 of 122, © 2000 Geothermal Education Office

Flash steam plants are the most common type of geothermal power generation plants in operation today. They use water at temperatures greater than 360°F (182°C) that is pumped under high pressure to the generation equipment at the surface. Binary cycle geothermal power generation plants differ from Dry Steam and Flash Steam systems in that the water or steam from the geothermal reservoir never comes in contact with the turbine/generator units.

Like all steam turbine generators, the force of steam is used to spin the turbine blades which spin the generator, producing electricity. But with geothermal energy, no fuels are burned.

Source: slide 38 of 122

, © 2000 Geothermal Education Office

Below here is the turbine blades used inside a geothermal turbine generator

Source: slide 39 of 122, © 2000 Geothermal Education Office

Geothermal power stations are similar to other steam turbine thermal power stations - heat from a fuel source whereas in geothermal case, the earth's core is used to heat water or another working fluid. The working fluid is then used to turn a turbine of a generator, thereby producing electricity. The fluid is then cooled and returned to the heat source.

Dry steam geothermal power plant:

These steam plants use hydrothermal fluids that are primarily steam. They directly use geothermal steam of 150°C which goes directly to a turbine, which drives a generator that produces electricity. The steam eliminates the need to burn fossil fuels to run the turbine. (Also eliminating the need to transport and store fuels!)

This is the oldest type of geothermal power plant. It was first used at Lardarello in Italy in 1904, and is still very effective. Steam technology is used today at The Geysers in northern California, the world's largest single source of geothermal power. These plants emit only excess steam and very minor amounts of gases.

Dry steam power plant ^[5]

Source: slide 50 of 122, © 2000 Geothermal Education Office

Flash steam geothermal power plant:

Hydrothermal fluids above 360°F (182°C) can be used in flash plants to make electricity. Fluid is sprayed into a tank held at a much lower pressure than the fluid, causing some of the fluid to rapidly vaporize, or "flash." The vapour then drives a turbine, which drives a generator. If any liquid remains in the tank, it can be flashed again in a second tank to extract even more energy.

Flash steam power plant ^[6]

Binary cycle geothermal power plant:

Binary cycle power plants are the most recent development, and can accept fluid temperatures as low as 57°C. The moderately hot geothermal water is passed by a secondary fluid with a much lower boiling point than water. This causes the secondary fluid to flash vaporize, which then drives the turbines. This is the most common type of geothermal electricity plant being constructed today. The thermal efficiency of this type plant is typically about 10-13%

Binary cycle power plant ^[7]

Geothermal Heat Pumps:

A Geothermal Heat Pump system is a heating and/or cooling system, which uses the earth as a heating resource in the winter or as a heat sink to put the heat back into the ground in the summer. This is made possible because ground temperatures of a certain depth are stable all year long (around 50-60F).

The idea of using the natural heat of the earth to heat houses without consuming extra energy can be dated back to the time of the Roman Empire, when people started to utilize sources of hot water and steam that exist near the surface of the earth to heat buildings. With the development of technology and the reduction of electricity prices, people are allowed to use geothermal resources anywhere in the world.

Bases on technology, a geothermal heat pump system is also known as "Geo Exchange" system and "ground-source heat pumps". The system usually requires a length of buried tubing on the property, a liquid pump back and a water-source heat pump. Common systems include open loop systems and closed loop systems.

Open Loop System: In an open loop system (also called a groundwater heat pump), the secondary loop pumps natural water from a well or body of water into a heat exchanger inside the heat pump. ASHRAE calls open loop systems groundwater heat pumps or surface water heat pumps, depending on the source. Heat is either extracted or added by the primary refrigerant loop, and the water is returned to a separate injection well, irrigation trench, tile field or body of water. The supply and return lines must be placed far enough apart to ensure thermal recharge of the source.

Source: EERE (Energy Efficient Renewable Energy).

Closed Loop System: Closed loop systems are more commonly used in household usage. Horizontal systems are more cost-effective for residential installations. While, vertical systems are usually used for commercial buildings and schools. The closed loop system circulates the fluid through the loop pipes and exchange heat between the fluid and the earth across the pipe.

Source: EERE (Energy Efficient Renewable Energy).

Advantages of Geothermal Heat Pumps:

Compared to conventional systems, geothermal heat pump systems have notable advantages in saving energy, duration, safety and environmental influence.

· Reduced Electricity Costs - Geothermal heat pump systems save from 30% to 70% energy over conventional systems, since they simply use electricity to move heat from the earth into buildings instead of burning fuels to generate heat. Geothermal heat pumps systems thus bring in higher efficiencies up to over 400% compared to conventional systems. ^[8] Study shows these systems can save the average family from US $400 to $1400 per year. ^[9] In the summer, the domestic hot water is produced for free and at a small cost in the winter.

· Durability and Reliability - Geothermal heat pumps systems have a longer life span than conventional systems. Most loop fields are warranted for 25 to 50 years and are expected to last at least 50 to 200 years. You do not have to worry about replacing the system in the short term and once installed systems can last twice as long as conventional systems.

· Convenience and Safety - Close loop systems mean no freezing of the flue vents in the cold weather when you need heat the most. Also, there are no gas lines that have potential for a gas leakage or fire.

· Environmental Benefits - The switch from fuel to electricity reduces greenhouse gas emissions. There are more than 1,000.000 geothermal heat pumps already installed in the U.S. and the technology have reduced an estimated more than 5.9 million metric tons of CO2 annually and more than 1.6 million metric tons of carbon equivalents annually.

Disadvantages of Geothermal Heat Pumps:

· One disadvantage is that the initial installation cost of GHPs is more expensive than a comparable gas-fired furnace and central air-conditioning system. (More discussions about cost can be found below.)

· Open-loop systems have more potential problems than either conventional systems or closed-loop geothermal systems because they bring outside water into the unit. This can lead to clogging, mineral deposits, and corrosion in the system. Open loop systems also require a large supply of clean water in order to be cost effective. This often limits their use to coastal areas, and areas adjacent to lakes, rivers, streams, etc.

· Refrigerant Loop systems have several disadvantages, including: environmental issues related to the system's use of refrigerant, corrosion issues since they use copper piping which needs anodic protection, and the need to maintain refrigerant temperatures within certain limits to keep from freezing or baking the ground, difficulty in finding and fixing a refrigerant loop leak, should one occur. ^[10]

Enhanced geothermal or hot dry rock systems:

The concept of Hot Dry Rock (HDR), now referred to as Enhanced Geothermal Systems (EGS), was first evaluated in the United States in the Los Alamos project between 1970 and 1996. Oil supply uncertainties generated much interest in the potential for geothermal energy in the US at the time as it did a little later in Ireland in the 1970s. EGS is also sometimes referred to as heat mining and is based on the use of heat recovered from the sub-surface to create electricity. The process consists of a power plant connected to a ‘heat reservoir’ at depth with temperatures of 150degrees or higher. The reservoir is developed by drilling wells into hot rock at depths of 4km or greater, depending on the local geothermal gradient, and connecting the wells through hydraulic fracturing so that water can be pumped into the system through one well and collected through another. An European project is currently underway at Soultz-sous-Forêts, France to examine the parameters involved in this new technology. In the late 1980s and 1990s in Urach (Tenzer et al. 1996), southwest Germany hydraulic tests were carried out in a borehole of 2800m which intersected crystalline basement. At this site monitoring of water levels was carried out continuously over 13 years, giving unique and valuable information on the likely variations of water levels in deep boreholes which might be used for geothermal energy. During extended pumping tests, water levels were seen to continuously drop over the period, indicating that hydraulic potential decreases with depth and apparently potentially setting limits on the usage of EGS with depth.

Diagrammatical section of HDR

Current Scenario of Geothermal Energy in World:

Although the use of geothermal hot springs has been known since ancient times, active geothermal exploration for industrial purposes started at the beginning of the 19th century with the use of geothermal fluids (boric acid) in Larderello (Italy).At the end of the 19th century, the first geothermal

District heating system began operating in Boise (United States), with Iceland following in the 1920s. At the start of the 20th century, again in Larderello, the first successful attempt to produce electricity from geothermal heat was achieved. Since then, installed geothermal electricity has steadily increased.

In 2009, global geothermal power capacity was 10.7 GWe and generated approximately 67.2 TWhe/year of electricity, at an average efficiency rate of 6.3 GWh/MWe (Bertani, 2010).A remarkable growth rate from 1980 to 1985 was largely driven by the temporary interest of the hydrocarbon industry – mainly Unocal (now merged with Chevron) – in geothermal energy, demonstrating the considerable influence on the geothermal market of attention from the hydrocarbon sector, which has expertise similar to that needed for geothermal development.

Geothermal electricity provides a significant share of total electricity demand in Iceland (25%) El Salvador(22%), Kenya and the Philippines (17%), and Costa Rica (13%). In absolute figures, the United States produced the most geothermal electricity in 2009: 16 603 GWhe/year from an installed capacity of 3 093 MWe. Total installed capacity of geothermal heat (excluding heat pumps) equalled 15,347 MWt in 2009, with a yearly heat production of 223 Peta joules (PJ); China shows the highest use of geothermal heat (excluding heat pumps), totalling 46.3 PJ/year geothermal heat use in 2009 (Lund et al., 2010).

Until recently, utilisation of geothermal energy was concentrated in areas where geological conditions permit a high-temperature circulating fluid to transfer heat from within the Earth to the surface through wells that discharge without any artificial lift. The fluid in convective hydrothermal resources can be vapour (steam), or water-dominated, with temperatures ranging from 100C to over 300C.

High-temperature geothermal fields are most common near tectonic plate boundaries, and are often associated with volcanoes and seismic activity, as the crust is highly fractured and thus permeable to fluids, resulting in heat sources being readily accessible. Convective hydrothermal reservoirs are shown as light grey areas, including heat flow and tectonic plate’s boundaries.

0 40 50 60 70 80 90 100 110 150

Least favourable Most favourable

Source: Background figure from (Hamza et al., 2008), adjustments from (IPCC, forthcoming).

Investment Costs:

Geothermal electricity development costs vary considerably as they depend on a wide range

of conditions, including resource temperature and pressure, reservoir depth and permeability, fluid chemistry, location, drilling market, size of development, number and type of plants (dry steam, flash, binary or hybrid), and whether the project is a greenfield site or expansion of an

existing plant. Development costs are also strongly affected by the prices of commodities such as oil, steel and cement.

In 2008, the capital costs of a Greenfield geothermal electricity development ranged from USD 2000/kW_e to USD 4000/kW_e for flash plant developments and USD 2400/kW_e to USD 5900/kW_e for binary developments (IEA, 2010a). The highest investment costs for binary plants can be found in Europe in small binary developments (of a few MW_e) used in conjunction with low to medium temperature resources. It is not yet possible to assess reliable investment data for EGS because it is still at the experimental stage. Investments costs for district heating range from USD 570/kW_t to USD 1570/kW_t (IPCC, forthcoming). For use of geothermal heat in greenhouses, investment costs range from USD 500/kW_t to USD 1000/kW_t

Operation and maintenance costs:

Operation and maintenance (O&M) costs in geothermal electricity plants are limited, as geothermal plants require no fuel. Typical O&M costs depend on location and size of the facility, type and number of plants, and use of remote control; they range from USD 9/MWhe (large flash, binary in New Zealand) to USD 25/MWhe (small binary in USA), excluding well replacement drilling costs (IEA, 2010). When make-up wells are considered to be part of O&M costs, which is usual in the geothermal electric industry, O&M costs are estimated at USD 19/MWhe to USD 24 /MWhe as a worldwide average (IPCC, forthcoming), although they can be as low as USD 10/MWhe to USD 14 /MWhe in New Zealand (Barnett and Quinlivan, 2009).

Production costs:

Levelised generation costs of geothermal power plants vary widely. On average, production costs for hydrothermal high temperature flash plants have been calculated to range from USD 50/MWhe to USD 80/MWhe. Production costs of hydrothermal binary plants vary on average from USD 60/MWhe to USD 110/MWhe (assumptions behind cost calculations are included in Appendix I). A recent case of a 30 MW binary development (United States) showed estimated levelised generation costs of USD 72/MWhe with a 15-year debt and 6.5% interest rate (IEA, 2010).

New plant generation costs in some countries (e.g. New Zealand) are highly competitive (even without subsidies) at USD 50/MWhe to USD 70/ MWhe for known high-temperature resources. Some binary plants have higher upper limits: levelised costs for new Greenfield plants can be as high as USD 120/MWhe in the United States and USD 200/MWhe in Europe, for small plants and lower-temperature resources. Estimated EGS development production costs range from USD 100/MWhe (for a 300°C resource at 4 km depth) to USD 190/MWhe (150°C resource at 5 km) in the United States, while European estimates are USD 250/MWhe to USD 300/MWhe (IEA, 2010a).

Current geothermal energy production is very small compared to estimates of the economically viable technical potential in the near term. ^[11] Glitnir Bank estimates that current installed capacity represents less than 5% of the economically feasible potential in 2020 for electricity production, and 0.05% for direct heat applications. Part of the reason for this discrepancy is financing: geothermal projects are capital-intensive, and have difficulty getting loans, particularly in the early stages. ^[8] It should also be noted that geothermal wells are drilled with the same equipment as oil and gas wells, and drilling is a large part of geothermal project costs. For this reason, geothermal project costs will tend to increase with high fossil energy prices, due to heightened demand for drilling equipment.

Geothermal projects are typically developed in four phases: Identification, Exploration, Drilling, and Production. The time frame of each of these steps is such that about three years pass before any electricity is produced, and between $40 million and $60 million has been spent for a typical 50-MW plant. Of these costs, drilling accounts for between $35 million and $50 million. Most, if not all, capital prior to the development's proven feasibility is financed through equity and not debt. Due to the high risk at the early stages of the process, banks generally do not fund development with loans at phases prior to drilling. Therefore, the initial investment money comes from seed capital, venture capital, or equity financing.

This gap between available financing and required financing for a developer creates a substantial barrier to entry that explains in part why geothermal energy accounts for such a small share of global energy use, in spite of apparently favourable economics if one only looks at levelised cost of energy, for example. How the investment environment might change in the future will be a key determinant of global geothermal energy production.

Case study of Geothermal Production plant in Newcastle, Co Dublin:

The details of the phase two of the exploration programme for the Newcastle Geothermal Energy project were announced recently by Geothermal Energy Limited (GEL), the company leading the project which will cost an estimated €22m to complete. GEL, an associate of the civil engineering group, Liffey Developments is actively exploring opportunities in the geothermal sector.

In 2004 The Geothermal Potential for Ireland report was produced by SLR and SEAI

SLR is a leading international environmental consultancy with an unrivalled reputation for providing high quality tailored services and SEAI is Sustainable Energy Ireland. Existing temperature data from the deep mineral and oil gas exploration boreholes in Ireland used to map national geothermal resources. The report identified the Blackrock to Newcastle as a potential geothermal target. There are two types of geothermal energy. At present Ireland only exploit the energy available at depth of less than 100metres. A network of pipes is laid or a well is drilled to no more than 150metres to access the ground water. The heat collected is multiplied by a ground source heat pump in the building and this heat is then used to heat the building. Shallow geothermal energy is quite successful for one-off houses and single developments, according to Geothermal Energy Limited, but its potential is constrained.

Why only Newcastle?

Newcastle’s potential as the site for Ireland’s first geothermal energy system was identified in 2004 by a case study of geological consultants, CAS. They have produced a geological resource map of Ireland, in which they have identified suitable sites for development of geothermal resources. Hot water is easier to access along geological fault lines in the earth’s crust it is available at shallower depths and one such fault line exists from Newcastle to Blackrock, Co Dublin.

The Newcastle site has two critical factors necessary for deep geothermal energy.

· First, the indications from the geophysical testing are the heat source is at the required temperature.

· Water must be present in large quantities to bring the heat to the surface and the possibility of being able to access such water here in Newcastle along the fault line is high.

The first geothermal exploration project identified as a potential geothermal target at the Blackrock to Newcastle Fault (BNF). Some part of this project is also being funded by the SEI. They commenced in 2007 and the project consists of three phases.

Phase 1: In 2007, the drilling of two bore wells to a depth of 300metres.

Below are the pictures of Drilling of bore wells at New castle

Phase 2: In 2008, the drilling of two deep exploratory boreholes to a depth of 1,400m

Phase 3: In the Newcastle area, certain operations like logging, testing and mapping of the boreholes taken place to develop a deep geological model.

So, water bearing fractures with temperatures of 46.2°C and also an additional funding from SEI is given to continue exploration of geothermal resources in South Dublin.

^[12]GT Energy established the potential of the South County Dublin area by conducting drill testing of a site in Newcastle, Co. Dublin in 2007 and 2008. Hanly (Managing Director of GT Energy believes the geological conditions are such in South Dublin that the area could possibly support three heat and electricity harnessing facilities which between them could provide up to 100MW of base load thermal energy with potential also to generate enough electricity to heat 100,000 homes.

Future Development of Geothermal Energy:

The scale of the technical potential of global geothermal resources dwarfs global primary energy demand; the key question regarding future development of geothermal resources will be whether any technologies allow cost-effective deployment. One set of technologies that appears somewhat promising is producing geothermal energy from active oil and gas wells, known as coproduction. While this technology may offer a resource comparable in potential magnitude to traditional hydrothermal sources and at lower costs ^[13], to this point oil and gas companies have not shown interest in coproduction of geothermal energy.

Another potentially important class of technologies is known as Enhanced Geothermal Systems (EGS). EGS involves injecting water through present or human-created fissures far below the earth's crust so that it is heated by hot rock, then circulating the heated water back to the surface to generate electricity. If EGS works and is economically feasible, it would expand the resource base dramatically, as in situ below-ground water would no longer be required for energy production. This is particularly important in consideration of the global distribution of hydrothermal resources; EGS could allow development of geothermal resources in areas that do not have economically feasible hydrothermal resources (i.e. most of the world). However, it should be noted that because an EGS project would have to supply its own water in order to produce energy, the demands for the water would have to be weighed against competing uses of water in a given region.

Projections and estimates of future development and potential of geothermal energy outline a wide range of possible futures. For the United States, the National Renewable Energy Laboratory has estimated that economically viable hydrothermal resources could be 10 GW in 2015, and 30 GW by 2050 (current installed capacity is 2.8 GW). Coproduction may add anywhere from 10 to 100 GW, and EGS another 100 GW. However, the Energy Information Administration's 2009 Annual Energy Outlook projects that geothermal generating capacity will remain less than 3 GW through 2030. ^[14]

Estimates of global potential hydrothermal generating capacity developed by Glitnir Bank are shown in the table above. Estimates for EGS potential by region have not been developed, with a few exceptions. It has been claimed that Rehai and Yangbajing regions of China could supply about 100 GW of potential electric capacity ^[15], and a similar estimate has been offered for India.^[16] However, it should be pointed out that all estimates of potential geothermal energy production, particularly estimates that include coproduction and EGS, are highly uncertain.

References:

[1] http://en.wikipedia.org/wiki/Geothermal_electricity

[2] http://climatelab.org/@api/deki/files/199/=Geothermal_direct_uses.jpg

[3] http://en.wikipedia.org/wiki/File:EGS_diagram.svg

[4] http://en.wikipedia.org/wiki/File:Diagram-VaporDominatedGeothermal.jpg

[5] http://en.wikipedia.org/wiki/File:Diagram-HotWaterGeothermal.jpg

[6] http://en.wikipedia.org/wiki/File:Diagram-BinaryGeothermal.jpg

[7] http://en.wikipedia.org/wiki/File:Diagram-BinaryGeothermal.jpg

[8] http://www.bobvila.com/articles/529-geothermal-heating-systems/pages/1

[9] http://www.centreflow.ca/category/healthy_home/

[10] http://www.residentialgeothermal.ca/how-much-does-it-cost.html

[11] Green, B.D., and R.G. Nix (2006). Geothermal: The Energy under Our Feet. National Renewable Energy Laboratory, Technical Report NREL/TP-840-40665

[12] http://www.irishpressreleases.ie/2010/09/23/plans-announced-for-ireland%E2%80%99s-first-geothermal-electricity-generation-plant/

[13] Porro, G., and S. Petty (2007). Updated U.S. Geothermal Supply Characterization. National Renewable Energy Laboratory, Conference Paper NREL/CP-640-41073.

[14] Energy Information Administration, Annual Energy Outlook 2009, Year-by-Year Reference Case Tables (2006-2030), Table 16: Renewable Energy Generating Capacity and Generation

[15] IEA (2008). Annual Report 2006. International Energy Agency Implementing Agreement for Cooperation in Geothermal Research & Technology. p.2. Primary source: Wan, Z., Zhao, Y. and Kang, J. (2005) Forecast and evaluation of hot dry rock geothermal resource in China. Renewable Energy 30:1831-1846.

[16] IEA (2008), p.2. Primary source: Chandrasekhar, V. and Chandrasekharam, D. (2007) Enhanced geothermal resources: Indian scenario. GRC Transactions, 31, 271-273.