Hill of Banchory Geothermal Energy Project Feasibility Study Report

This feasibility study explored the potential for a deep geothermal heat project at Hill of Banchory, Aberdeenshire. The geology of the Hill of Fare, to the north of Banchory, gives cause to believe it has good geothermal potential, while the Hill of Banchory heat network, situated on the northern side of the town, offers a ready-made heat customer. The partners in the consortium consisted of academics and developers with relevant expertise in deep geothermal energy, heat networks, and financial analysis, together with representatives of local Government. They conducted geological fieldwork around the Hill of Fare, engaged with local residents to establish their attitudes to geothermal energy, and built business models to predict the conditions under which the heat network at Hill of Banchory would be commercial if it utilised heat from the proposed geothermal well. They also estimated the potential carbon emission reductions that could be achieved by using deep geothermal energy, both at Hill of Banchory and more widely

Geothermal Energy: Tapping the Energy in the Earth's Core

Key facts: - Geothermal energy comes from the heat in the Earth's core. This heat creates underground reservoirs of steam and hot water, which can be tapped to generate electricity or to heat and cool buildings directly. - Geothermal energy is the third largest source of renewable energy, behind hydropower and biomass. In 2003, it accounted for 7 percent of US electricity generated from renewable sources. - The United States is the world's largest producer of geothermal energy. About 2,800 megawatts (MW) of geothermal electrical capacity is connected to the electrical grid in the United States; 8,000 MW of geothermal electrical capacity is installed worldwide. - The US Geological Survey (USGS) has identified approximately 22,000 MW of geothermal resources sufficient for electrical power generation in the United States. In addition, low-temperature resources sufficient for direct-use and heat pumps are available across the country. - The largest geothermal development in the world is at The Geysers in California. This plant, in operation since 1960, has a capacity of over 850 MW and satisfies nearly 70 percent of the average electrical demand for the Californian North Coast region. - Electricity from The Geysers sells for $0.03 to$0.035 per kilowatt-hour (kWh), while electricity from newer geothermal plants costs between $0.05 and$0.08 per kWh. New geothermal power plants are now eligible for a Production Tax Credit for power produced in the first 5 years of operation

Heat buffers improve capacity and exploitation degree of geothermal energy sources

This research focuses on the role of heat buffers to support optimal use of combinations of traditional and renewable heat sources like geothermal heat for greenhouse heating. The objective was to determine the contribution of heat buffers to effective new combinations of resources that satisfy greenhouse heat, carbon dioxide and electricity demand at minimum cost. Tank buffers, basement buffers and aquifers were considered as short and long term buffers. Simulations were carried out for a 10ha sweet pepper and a 30ha tomato greenhouse (15ha intensively lighted). Standard heating systems based on central boiler and co-generation were used as a reference and compared with combinations of boilers, co-generators, geothermal heat and heat buffer strategies. Crop production and greenhouse climate were simulated and resource demand determined for normal greenhouse operation. A linear programming algorithm was used to apply resources and equipment available to the model at minimum cost. Results show that heat buffers help to reduce the required capacity of a geothermal heat source, and increase both the utilisation degree of the source and the cover percentage of greenhouse heat demand. The technically most feasible solution for long term buffering was the basement buffer which allows high buffer volumes without loss of useful space and heat loss contributes to greenhouse heating, however this solution was economically not feasible. Also the deep aquifer was a good option, however exploitation risks and manageability are potential problems. Integration of geothermal heat with other sources resulted in the best solutions that were both technically and economically feasible. Simulation showed at gas price level 30¿ct.m-3, that geothermal heat was cheaper than central boiler and even co-generation heat when hours of operation exceed 1000h.y-1. Instead of using large buffers, peak loads can also be covered by central boilers. Simulated solutions reduced gas consumption with 60 to 95%

Geothermal probabilistic cost study

A tool is presented to quantify the risks of geothermal projects, the Geothermal Probabilistic Cost Model (GPCM). The GPCM model was used to evaluate a geothermal reservoir for a binary-cycle electric plant at Heber, California. Three institutional aspects of the geothermal risk which can shift the risk among different agents was analyzed. The leasing of geothermal land, contracting between the producer and the user of the geothermal heat, and insurance against faulty performance were examined

Parsimonious numerical modelling of deep geothermal reservoirs

Numerical modelling has been undertaken to help improve understanding of a deep geothermal system being considered for development in the vicinity of Eastgate (Weardale, County Durham, UK). A parsimonious numerical modelling approach is used, which allows the possibility to develop a workable formal framework, rigorously testing evolving concepts against data as they become available. The approach used and results presented in this study are valuable as a contribution to a wider understanding of deep geothermal systems. This modelling approach is novel in that it utilises the mass transport code MT3DMS as a surrogate representation for heat transport in mid-enthalpy geothermal systems. A three-dimensional heat transport model was built, based on a relatively simple conceptual model. Results of simulation runs of a geothermal production scenario have positive implications for a working geothermal system at Eastgate. The Eastgate Geothermal Field has significant exploitation potential for combined heat and power purposes; it is anticipated that this site could support several tens of megawatts of heat production for direct use and many megawatts of electrical power using a binary power plant

Overcoming challenges in the classification of deep geothermal potential

The geothermal community lacks a universal definition of deep geothermal systems. A minimum depth of 400 m is often assumed, with a further sub-classification into middle-deep geothermal systems for reservoirs found between 400 and 1000 m. Yet, the simplistic use of a depth cut-off is insufficient to uniquely determine the type of resource and its associated potential. Different definitions and criteria have been proposed in the past to frame deep geothermal systems. However, although they have valid assumptions, these frameworks lack systematic integration of correlated factors. To further complicate matters, new definitions such as hot dry rock (HDR), enhanced or engineered geothermal systems (EGSs) or deep heat mining have been introduced over the years. A clear and transparent approach is needed to estimate the potential of deep geothermal systems and be capable of distinguishing between resources of a different nature. In order to overcome the ambiguity associated with some past definitions such as EGS, this paper proposes the return to a more rigorous petrothermal versus hydrothermal classification. This would be superimposed with numerical criteria for the following: depth and temperature; predominance of conduction, convection or advection; formation type; rock properties; heat source type; requirement for formation stimulation and corresponding efficiency; requirement to provide the carrier fluid; well productivity (or injectivity); production (or circulation) flow rate; and heat recharge mode. Using the results from data mining of past and present deep geothermal projects worldwide, a classification of the same, according to the aforementioned criteria is proposed

Impact of geothermal heating on the global ocean circulation

The response of a global circulation model to a uniform geothermal heat flux of 50 mW m-2 through the sea floor is examined. If the geothermal heat input were transported upward purely by diffusion, the deep ocean would warm by 1.2°C. However, geothermal heating induces a substantial change in the deep circulation which is larger than previously assumed and subsequently the warming of the deep ocean is only a quarter of that suggested by the diffusive limit. The numerical ocean model responds most strongly in the Indo-Pacific with an increase in meridional overturning of 1.8 Sv, enhancing the existing overturning by approximately 25%

Ranking the geothermal potential of radiothermal granites in Scotland: are any others as hot as the Cairngorms?

Prior investigations concur that the granite plutons in Scotland which are most likely to prove favourable for geothermal exploration are the Ballater, Bennachie, Cairngorm and Mount Battock plutons, all of which have heat production values greater than 5 μW m−3. This heat production arises from the significant concentrations of potassium, uranium and thorium in some granite plutons. A new field-based gamma-ray spectrometric survey targeted plutons that were poorly surveyed in the past or near areas of high heat demand. This survey identifies several other plutons (Ben Rhinnes, Cheviot, Hill of Fare, Lochnagar and Monadhliath) with heat production rates between 3 and 5 μW m−3 that could well have geothermal gradients sufficient for direct heat use rather than higher temperatures required for electricity generation. The Criffel and Cheviot plutons are examples of Scottish granites that have concentric compositional zonation and some zones have significantly higher (up to 20%) heat production rates than others in the same plutons. However, the relatively small surface areas of individual high heat-production zones mean that it is unlikely to be worthwhile specifically targeting them

Can you take the heat? – Geothermal energy in mining

In 2013, there are less than 20 documented examples of operational geothermal systems on mine sites worldwide. This is surprising, since on remote mine sites, where fuels may have to be shipped in over great distances, heating and cooling from low-enthalpy geothermal sources may have a significant advantage in operational cost over conventional energy sources. A review of factors affecting the feasibility of geothermal systems on mining projects has been undertaken, and has identified the possible configurations of geothermal systems suitable for the exploration, operational and closure phases of mine development. The geothermal opportunities associated with abandoned or legacy mines are also discussed. The potential categories of heat reservoirs associated with mine sites are: natural ground; backfilled workings; mine waste; dewatering pumping; and flooded workings/pit lakes. The potentially lower operational costs for heating and cooling must be offset against the capital cost of a geothermal system. The focus for mine operators should therefore be on identifying at feasibility stage those projects where conditions are favourable for geothermal systems, the potential risks are understood, the economics are likely to be beneficial, and geothermal systems can be established while minimising additional capital costs

The Colorado School of Mines Nevada geothermal study

Geothermal systems in the Basin and Range Province of the western United States probably differ in many respects from geothermal systems already discovered in other parts of the world because of the unique tectonic setting. To investigate this, a study of the geothermal occurrences at Fly Ranch, approximately 100 miles north of Reno, Nevada, has been undertaken. Ample evidence for a geothermal system exists in this area, including the surface expression of heat flow in the form of hot springs, an extensive area of low electrical resistivity, and a high level of seismicity along faults bounding the thermal area. However, geophysical and geological studies have not yet provided evidence for a local heat source at depth. Additional detailed geophysical and geological studies, as well as drilling, must be completed before the geothermal system can be described fully