Deep geothermal FAQ s

Transcription

1 What is geothermal energy? Deep geothermal FAQ s What is the deep geothermal resource in Cornwall? What are the benefits for Cornwall? What are Engineered/Enhanced Geothermal Systems (EGS) or Hot Dry Rocks? Is the electricity grid in Cornwall able to take any more locally generated renewable energy? What will projects do with the waste heat? Why is it renewable energy? Is it possible to deplete reserves; is it sustainable? What are the environmental impacts? What is the risk of earth tremors? What impact will it have on water? Will there be increased traffic or heavy plant to the site? How noisy will the drilling be? What is the risk of radiation from the granite? What is the visual impact? What is the difference between deep geothermal and fracking for shale gas? Where will they be situated?

2 What is geothermal energy? Geothermal energy is heat within the Earth. The transfer of that heat from underground to the surface can provide a renewable source of thermal energy that can be used to generate electricity or to provide direct heat. For thousands of years hot springs have been used for bathing and in the early 1900 s the first power plant was built in Italy. Generally, geothermal energy has been associated with areas of tectonic or volcanic activity, such as Iceland and New Zealand, where the geology allows the natural transfer of very high temperatures to the surface. In recent years technological developments are enabling access to hot, medium and low temperatures from deep underground aquifers and from hot dry rocks. The International Energy Agency suggests that by 2050 geothermal energy can provide 3.5% of global electricity demand and 3.9% of global heat demand. What is the deep geothermal resource in Cornwall? The geothermal energy accessible in Cornwall is in the form of radioactive granite (hot dry rocks) that generates heat due to radioactive decay. The geological formation called the Cornubian Batholith, a vast mass of connected granite intrusions, between 10 and 20km deep, extends from Dartmoor to the Isles of Scilly. Temperatures of 150 to 200 C can be reached at depths of between 3 and 6 km. This temperature gradient was evidenced at the Camborne School of Mines, Hot Dry Rocks project at Rosemanowes Quarry, Penryn in the 1980 s. Although the granite is hot and has natural fractures, it lacks naturally circulating water to transfer the heat to surface. The granite, at depth, can be engineered to create pathways between boreholes (wells) through which water can flow freely and act as a radiator: this is done by injecting water at pressure into the existing natural fractures to open them up. This process is known as engineered or enhanced geothermal systems (EGS). What are the benefits for Cornwall? Cornwall Council, as part funders of the deep geothermal project, will be involved in the project from the start and will ensure the benefits to Cornwall will be taken full advantage of. If all the estimated resource could be captured it could provide Cornwall with significant economic and social benefits in a high value, knowledge based sector.

3 The resource could equate to more power than Cornwall s total demand. In addition to electricity, the waste heat can be utilised. This home grown, clean energy with price stability, could form part of a longer term plan to tackle fuel poverty, support and attract businesses with significant heat demand and safeguard jobs. The lower resource estimate would see a c. 500m investment, creating c.5k jobs whilst reducing Cornwall s emissions by about 20%. Geothermal electricity offers advantages over other renewable energy sources; it provides baseload generation (24/7, 365 days of the year) and is not affected by the weather or seasonal variations; it is also able to react quickly to changes and peaks in demand, contributing longer term to a smarter energy system. Geothermal has a very small footprint on the landscape when compared to the same power output of other technologies. The technology to be used in Cornwall is being developed across the globe; the US, Australia, Asia and Europe. There is an opportunity for Cornwall to be part of this promising, growing global industry. What are Engineered/Enhanced Geothermal Systems (EGS) or Hot Dry Rocks? An Engineered/Enhanced Geothermal System (EGS) is a man-made underground aquifer and circulatory system created in Hot Dry Rocks: rocks with insufficient permeability to allow water to flow. The hot dry rocks are generally granite; accessed to depths of 3-5km. During the engineering stage, water is injected into the borehole at pressure and under precise conditions: this process is known as hydraulic stimulation or hydro sheering, which causes natural fractures to open further, creating the required permeability. Recovery of the heat requires a fluid being injected into the closed loop, down the injection borehole, through the network of small interconnected fractures in the hot rocks, which act as a radiator, and then pumped back up to the surface through another borehole to a power plant. In the past 35 years there has been considerable research into EGS applied to the hot rock resource across Europe, the USA and Japan. The International Energy Agency Geothermal Roadmap predicts that more than half of the projected increase in geothermal will be in the form of EGS and the technology will be commercially viable by Is the electricity grid in Cornwall able to take any more locally generated renewable energy? Cornwall currently has spare capacity on the network, however because of connection agreements, yet to be used, and the time it will likely take to upgrade; there is very little capacity actually available for new connections.

4 Delivering geothermal in capacities such as the estimated resource of 100MW or 4GW will take many years; with each 5-10MW project having a 4-6 years construction time. Cornwall Council is working with the government as part of the devolution deal, and with the distribution network operator to find ways to facilitate more decentralised renewable energy generation. Potential solutions include; looking at the connection agreements, network management, smart technology solutions, energy storage (up to c.200mw of output) as well as traditional infrastructure upgrades. What will projects do with the waste heat? Cornwall Council as part funders will be proactive from the start and ensure the benefits to Cornwall are maximised. Many of the benefits of geothermal, such as jobs, increased GVA and reducing fuel poverty, are all related to the use of the heat, and projects will be more financially viable the more heat they are able to sell. Cornwall Council has recently commissioned a strategic heat opportunities study that will map all heat sources with existing and planned heat demand and include areas for potential development. The Council, as part of the devolution deal with government, is also investigating the opportunities for low carbon heat enterprise zones at potential geothermal sites to encourage new businesses with significant heat demand to relocate to Cornwall. Both pieces of work will form part of the evidence base to develop heat networks connecting geothermal heat sources with homes and businesses. Why is it renewable energy? Geothermal energy is heat within the Earth; from the Earth s core, volcanic activity and the decay of radioactive rocks in the Earth s crust: this resource is almost unlimited. In geothermal areas dependent on a reservoir of hot water, the water taken out can be reinjected, making it a sustainable energy source. Geothermal energy emits virtually no emissions. Is it possible to deplete reserves; is it sustainable? The heat that is extracted is very minimal in comparison to the heat stored in the earth s crust, so this level of extraction will not affect ground temperatures. The lifetime of a geothermal project is designed to be 25 years, after which time the heat in the surrounding rock will be restored.

5 What are the environmental impacts? Although geothermal has less of a land use impact than other technologies and produces virtually no emissions, there are some potential concerns over environmental impacts which need to be considered. These include seismicity or earth tremors, water use and risk of contamination, increased traffic, noise, and emissions of gas, liquid and solids. Information on each of these issues is set out in the sections below. All these issues will be fully considered as part of the planning process. Cornwall Council has worked with the industry to develop robust Supplementary Planning Guidance to ensure risks are mitigated and minimised. In addition to planning permission, projects must also obtain the necessary licenses from the Environment Agency. What is the risk of earth tremors? The hot granite deep underground does not naturally allow water to flow freely through it. To enable this, the granite needs to be enhanced or engineered. Preexisting factures can be opened by pumping pressurised water down the borehole. During this process rocks may slip along the pre-existing fractures and produce micro-seismic events: this is inevitable and expected. These events, detected with sensitive instruments, are necessary to pinpoint where the fractures are and help to understand the extent of the reservoir. These events almost always occur deep underground and are unlikely to be felt at the surface; however there is a risk of minor surface vibration, close to the site. This is comparable with mining blasts that were undertaken daily in the tin mines of Cornwall. In order to ensure that geothermal development does not create an unacceptable risk of seismic activity, as set out in the Council supplementary planning guidance, a seismic hazard assessment should be undertaken that considers: pre-project seismic activity, the likelihood of triggering an event and measures to avoid it. Ongoing monitoring throughout the lifetime of the plant will be adopted and maximum acceptable levels, as imposed by the Council, should not be exceeded. When looking at the risk, the earthquakes of at the Basel project in Switzerland are often mentioned. The geology in Basel is very different to Cornwall s: Basel is situated in an unstable tectonic region with a long history of earthquakes. What impact will it have on water? All projects will need a license from the Environment Agency alongside planning permission to ensure regulations are adhered to. During the early engineering stages to increase water flow, a large source of fresh water will be required. The Councils Supplementary Planning Guidance advises, as far as possible, that drilling and stimulation fluids should be re-used in order to reduce freshwater resource impacts and potential disposal issues.

6 Drilling stimulation fluids not reinjected should be stored in tanks, with appropriate spill protection. During operation the water requirement will be minimal. This is because the wells are encased and the water will circulate in a closed loop; down one well and up another. Because it is a closed loop there will be no risk to ground water supplies and any water that is released will be contained and treated, as with mine water. Will there be increased traffic or heavy plant to the site? The main impact to the local transport network will be during the mobilisation and demobilisation of the large drilling rig, each of which will involve HGVs transporting equipment on and off the site over a few days. A traffic management plan may need to be prepared and agreed with the Council in order to avoid unnecessary local traffic disruption during this time. How noisy will the drilling be? Rigs are hired from the oil industry, at high daily rates, probably from Europe, so drilling will take place 24 hours a day, 7 days per week to minimise the cost. It will take around 20 weeks per well. To maximise the benefits of geothermal, the plant needs to be situated within the proximity of heat users. The Councils Supplementary Planning Guidance sets out the noise limits for different proximity to receptors and states that developers should demonstrate throughout the construction, operation and decommissioning phases of a deep geothermal development, all practicable measures will be taken to minimise noise emissions. Drilling rigs specifically for use in a populated area and heavily soundproofed, can be utilised and the noise can be tempered by landscaping if required. What is the risk of radiation from the granite? Radon and background radiation is naturally produced by the granites and clays of Cornwall. The radioactive decay is the reason the granite is so hot at depth. During drilling the level of radon emitted is not considered to have a significant impact and water quality will be monitored and carefully managed. During operation, all water will circulate in a closed circuit so radon gas will not be emitted. Longer term, any build up of radioactive minerals will be safely removed from site and dealt with.

7 What is the visual impact? Geothermal power plants have a relatively small footprint on the landscape, and don't require the storage, transportation, or combustion of fuels. Either no emissions or just steam are visible during operation. Site selection, design and layout can minimise the visual impacts of all development. This is considered in detail in the Council s Supplementary Planning Guidance with specific consideration given to tourism, designated and protected areas, ecology, open areas, the character of an area and the views of nearby residents. What is the difference between EGS and fracking for shale gas? Before considering the process it is important to understand the benefits of geothermal energy; it is a clean renewable technology that emits very little gases and does not contribute to an increase in greenhouse gases and climate change. With the Council s involvement, the benefits from locally generated heat and power can be kept local. The process to enhance the water flow in the granite is similar to the fracking process used to capture shale gas. However, while both processes have the potential to create seismic events (tremors), the geothermal process takes place at far greater depths 4.5-5km as opposed to 1.5km for fracking and with lower pressures, so surface vibrations are less likely to be felt. There are also some important differences between the processes: Fracking for shale gas uses much higher pressures to initiate new fractures in un-fractured shale rock, which result in wide cracks that require additives (sand and chemicals) to hold them open. Only some of the fluid returns to the surface, where it is sealed in containers before treatment. Licences require operators to minimise the release of gases: when it can t be economically used, natural gas must be flared to reduce its global warming emissions and the gas may only be vented released into the air when necessary for safety. The process used to open and enhance pre-existing fractures in granite uses the rough surface texture of rock fractures to allow self-propping of open fractures, so there is no requirement for any chemical additives in the pressurised water: this reduces the risk of ground water contamination. This process takes place at depths of 4 km and deeper, where there is no natural gas or drinkable water present. During operation the water is circulated in a closed-loop: there can be no release of gas or minerals at the surface. Where will they be situated? Projects will need to secure planning permission and water abstraction licenses: this will ensure all environmental risks and impacts have been considered and assessed. Cornwall Council s Supplementary Planning Guidance clearly sets out:

8 Wherever geological and thermal conditions allow, geothermal development should be sited on previously developed/brownfield sites, contaminated land (which cannot easily be remediated for other uses) and industrial land. Where development is located on agricultural land it should avoid significant loss of Best and Most Versatile agricultural land. Where such agricultural land cannot be avoided clear justification of the benefits of the development and understanding of the impact on the supply of agricultural land would have to be demonstrated. The Council encourages measures that optimise the use of the available resource in a given location where it is acceptable to do so, taking into account considerations such as landscape, heritage and residential amenity impacts. Maximising the output, and social and economic benefits, requires plant to be sited in the proximity of heat users and connection to the electricity network. Cornwall Council has commissioned a consultant to undertake a strategic heat to identify preferred sites: mapping the resource with existing and planned demand, and areas suitable for development, alongside constrained and protected areas.