The Emmaboda HT-BTES was taken into operation 2010. Since then ~10 GWh has been stored, only a fraction has been extracted, and a storage temperature of 40-45 oC has been reached. The purpose of the BTES is to utilize waste heat from the industrial processes. Heat sources have been added annually and in 2015 the predicted heat injection (3.6 GWh/year) will be reached. Performed simulations are based on actual heat injection and extraction. The simulation model can reasonably well predict the future operation of the BTES. Initial problems with circulating the heat carrier at a slight vacuum pressure have been solved by using vacuum pumps to degas the fluid. The BTES has reduced the amount of bought district heating by approximately 4 GWh/year. To improve the system further, and reduce heat losses, it is suggested that a heat pump should be installed for heat extraction.
The Lillpite River Valley stretches 45 km NV, from Piteå at the Gulf of Bothnia. The 619 km2 large catchment area comprises a dozen lakes. The average flow rate of the river is 6.24 m3/s. Lillpite Kraft AB, which owns the two power plants in the Lillpite River, has now applied for a demolition permit after 30 years of unprofitable operation. This demolition will take place in 2020, after which there are no obstacles to the fish's migration in the river. The Lillpite River was famous for its large salmon but also for its trout, grayling and lamprey. River crayfish and freshwater pearl mussel exist in the river, both upstream and downstream of the two dams, and in the brooks. There are even eel and pikeperch in the river, which also hosts beaver and otter. The Lillpite River Economic Association manages the compensation (~30M€ over 50 years) for the wind power intrusion in the area. This organisation is committed to make the river the fishing water it once was, as a driving force for the development of the river valley. At this seminar, we seek your help and advice based on knowledge and experience. How to determine the river status before and after dam removal? River erosion? Timeline after dam removal? Evaluation of ecology and biodiversity? How to improve conditions for fish, crustaceans and pearl mussel? How to meet sceptical locals? What should/could we do before the dam removal?
This paper describes research on a pilot plant in Luleå, Sweden. The plant consists of 19 boreholes, 52 mm in diameter, for heat supply and extraction; and 10 boreholes for temperature monitoring. All the boreholes are 21 m deep. The report describes in detail the performance and results of rock mass permeability and borehole permeability tests. It also discusses hydraulic fracturing and explosive fracturing in the boreholes. A simulation model of water flow in the test plant is described. The paper includes conclusions from the test results and recommendations for further study.
There is an increasing interest in Low Temperature Underground Thermal Energy Storage (LT UTES) for the purpose of space cooling. Some of the different types of UTES systems, with an anti-freeze heat carrier in a closed pipe system, tolerate injection temperatures below freezing. Thus, seasonal storage of cold with injection temperatures below freezing would be possible in large Borehole Thermal Energy Stores (BTES). The most obvious cold source is the cold winter air. There is however very little experience of low temperature cold extraction from air for injection into the ground.A low temperature cold injection field test was performed during the winter of 1997/98 at Luleå University of Technology. The test was performed in one 65 m borehole drilled vertically into the crystalline bedrock. Cold was extracted from the winter air at occurring air temperatures - i.e. sometimes well below -30°C. The aim of this test was to obtain experience of problems associated with cold extraction from the air and cold injection into the ground.
Seasonal air temperature variations and corresponding changes in groundwater temperature cause convective movements in groundwater similar to the seasonal turnover in lakes. Numerical simulations were performed to investigate the natural conditions for thermally driven groundwater convection to take place. Thermally driven convection could be triggered by a horizontal groundwater flow, Convection then starts at a considerably lower Rayleigh number (Ra) than the general critical Rayleigh number (Ra assuming that 10 degrees C groundwater is cooled to 4 degrees C, i.e. heated from below convection in porous media, This study supports the hypothesis that seasonal temperature variations, under certain conditions, initiate and drive thermal convection.
A water driven down-the-hole drilling equipment (Wassara) was developed some years ago at the Kiruna mine, Sweden, which is the largest underground mine in the world. This new drilling technology has been used in their mining production for a few years. It has several advantages to pneumatic drilling methods. This water driven hammer has now for the first time been tested in well drilling (110 mm) in hard rock. The first drilling was done in Örebro for the Swedish telephone company TELIA that is constructing a great number of borehole (direct cooling) systems for their telephone switching stations. The water hammer proved to be considerably more efficient; the drilling speed is about twice as high and the energy consumption is about 1/3, compared to that of the previously used air driven hammers. Another advantage is the possibility to drill several hundred meters in hard rock even in water rich and fractured rock. Experience of the first drilling is summarised.
Nature has found ways to laminarize turbulent flows, as demonstrated by the high swim speed of dolphins and the silent flight of owls. Owls locate their prey by hearing and need to fly silently. In both cases it has something to do with the soft pliable surface of the moving body and the wavy pattern that occurs on the dolphin skin and the owl feathers. Our objective was to investigate whether a pipe lined with a hairy soft carpet would “laminarize” air flows. The degree of laminarization was determined by the velocity profile. Manual pressure measurements were done to determine the air velocity at cross sections along the pipe. Varying flow rates were tested before the hair was cut increasingly shorter. It was found that for some hair lengths the velocity profile approached the parabolic form of laminar flow at very high Reynolds number.
The increase in the global air temperature is an inadequate measure of global warming, which should rather be considered in terms of energy. The ongoing global warming means that heat has been accumulating since 1880 in the air, ground and water. Before explaining this warming by external heat sources, the net heat emissions on Earth must be considered. Such emissions from, e.g., the global use of fossil fuels and nuclear power, must contribute to global warming. The aim of this study is to compare globally accumulated and emitted heat. The heat accumulated in the air corresponds to 6.6% of global warming, while the remaining heat is stored in the ground (31.5%), melting of ice (33.4%) and sea water (28.5%). It was found that the net heat emissions from 1880-2000 correspond to 74% of the accumulated heat, i.e., global warming, during the same period. The missing heat (26%) must have other causes, e.g., the greenhouse effect, the natural variations in the climate and/or the underestimation of net heat emissions. Most measures that have already been taken to combat global warming are also beneficial for the current explanation, though nuclear power is not a solution to (but part of) the problem.
The global air temperature increase is an inadequate measure of global warming, which rather should be considered in terms of energy. The ongoing global warming means that heat has been accumulating since 1880, in air, ground, and water. Before explaining this warming by external heat sources the net heat emissions on Earth must be considered. Such emissions, from e.g. the global use of fossil fuel and nuclear power, must contribute to global warming.The aim of this study was to compare globally accumulated and emitted heat. The heat accumulated in air corresponds to 6.6% of the global warming, while the remaining heat is stored in the ground (31.5%), melting of ice (33.4%), and sea water (28.5%). It was found that the net heat emissions 1880-2000 correspond to 74% of accumulated heat, i.e. the global warming, during the same period. The missing heat (26%) must have other causes; e.g. the greenhouse effect, natural variation of the climate, and/or underestimation of net heat emissions. Most measures already taken to combat global warming are beneficial also for current explanation, though nuclear power is not a solution but part of the problem.
Most types of renewable energy are available when the demand is low. So, summer heat is available during the warm season, when heating demand is low, and winter cold is available when the cooling demand is low. Therefore, seasonal storage of thermal energy is important for the large-scale utilization of thermal energy. Large-scale storage systems require large storage volumes. Such systems are therefore often constructed as Underground Thermal Energy Storage (UTES) systems. The UTES includes ATES, BTES and CTES i.e. thermal energy storage in aquifers, boreholes, and caverns. UTES systems have been developed during the last three decades and are now found all over the world. Sweden is one of the leading countries in this technology. This is underlined by the fact that borehole systems cover almost 20% of the Swedish heating demand. During the last decade it has been a UTES development towards larger systems for both heating and cooling. Here, different UTES applications are presented.
The objective of this project has been to employ chemical leaching to achieve sufficient hydraulic contact through fissures in the rock to enable them to serve as part of the circulation system of a borehole in the heat store.^The trials were carried out both in the laboratory and in the field.^The results obtained in the field were investigated by means of hydraulic tests that allowed the hydraulic conductivity to be determined.^The results were not as expected, rather they were the opposite.^Fissures in the rock were sealed instead of being opened up, and the hydraulic conductivity decreased instead of increasing.^The explanation for this lies in the fact that the leaching liquid, a solution of NaOH, became saturated by dissolved minerals which were then precipitated elsewhere in the fracture system.^However, this undesired result may turn out to have a number of geological engineering applications, as there is normally a greater need to seal fissures in rock than to open them.
The aim of this research project was to increase the hydraulic conductivity of fractured rock by pumping a leaching fluid (NaOH) through rock fractures. A 16-week field test was carried out in a borehole heat store consisting of 19 vertical boreholes to a depth of 15 m in gneissic rock. The leaching process was studied simultaneously in a laboratory test where rock samples from core drillings of the test site were used. The hypothesis that NaOH-solution would leach and thereby widen the fractuers, was not fulfilled. On the contrary, the fractures were sealed as the leaching test went on. The explanation for this is that the leaching rate was higher than expected, the leaching fluid was saturated and the dissolved minerals precipitated. In principle, the minerals were dissolved and moved from one part of the fractures to precipitate at another part, causing clogging. The effect of the leaching field test has been simulated by means of a numerical model. The conclusion is that a leaching of rock as described in this paper should be combined with a deposition tank for the clogging material in order to avoid precipitation in the rock fractures. The results of this project have demonstrated a way of sealing rock fractures that has many more applications in engineering geology.
This report summarizes the background, development and testing of the Crystal Plaster (CP), which refers to a (crystal) patch in which tiny quartz crystals are the active part in reducing pains. The physical background is the piezoelectric property of bone, i.e. bone subjected to pressure variations generates an electric current. The opposite, the piezoelectric effect is also at work, which means that if bone is subjected to an alternating electro-magnetic radiation then the bone will respond by volume changes and corresponding mechanical stress. The piezoelectric crystals of the CP are in different ways interacting with the corresponding properties of the body. It would be possible to read out much more of the test results from the CP tests that were made in 2006-2007. In any case, the performed study shows clearly that the Crystal Plaster reduces nociceptive pains. We can see that the placebo effect is adding to the results but the test also shows a clear difference between the Placebo and the real Crystal Plaster in favor of the real CP.
A preliminary study of a solar-heated low-temperature space-heating system with seasonal storage in the ground has been performed. The system performance has been evaluated using the simulation models TRNSYS and MINSUN together with the ground storage module DST. The study implies an economically feasible design for a total annual heat demand of about 2500 MWh. The main objective was to perform a study on Anneberg, a planned residential area of 90 single-family houses with 1080 MWh total heat demand. The suggested heating system with a solar fraction of 60% includes 3000 m2 of solar collectors but electrical heaters to produce peak heating. The floor heating system was designed for 30°C supply temperature. The temperature of the seasonal storage unit, a borehole array in crystalline rock of 60,000 m3, varies between 30 and 45°C over the year. The total annual heating costs, which include all costs (including capital, energy, maintenance etc.) associated with the heating system, were investigated for three different systems: solar heating (1000 SEK MWh−1), small-scale district heating (1100 SEK MWh−1) and individual ground-coupled heat pumps (920 SEK MWh−1). The heat loss from the Anneberg storage system was 42% of the collected solar energy. This heat loss would be reduced in a larger storage system, so a case where the size of the proposed solar heating system was enlarged by a factor of three was also investigated. The total annual cost of the solar heating system was reduced by about 20% to about 800 SEK MWh−1, which is lower than the best conventional alternative.
A solar heating system with underground storage of warm water in hard rock to meet demand in the colder months is described. There are no heat pumps. The system is being developed in a residential area north of Stockholm and will serve 36 family houses, four rows of terraced cottages and a service/nursing home with a floor area of 9,000 square metres. The solar collectors are on the roof and heated water is fed to the underground store through a borehole system in the underlying granite. Details of the thermal properties of the granite are given together with costs of construction and running of the whole system. The project is planned to be up and running in late 2001
Vattnet stängdes in i ett äggformat kärl med en rotator i botten. En liten lufvolym lämnades i toppen och syrehalt pH mm mättes under de olika försöken.
Since 1988, Sweden and Finland have collaborated bilaterally on thermal energy storage with respect to information exchange and collaborative R&D projects. The two countries have both investigated underground thermal energy storage for nearly two decades, and have similar bedrock-the Fenno-Scandian granitic rocks. This paper reviews the work performed in the field of combined rock cavern and borehole heat stores, concerned with construction technology, costs and design principles. One example is an asymmetric store, in the form of 40- to 60-m-long horizontal boreholes between two rock caverns, with the caverns themselves comprising only about 10% of the total storage volume. This design has a specific cost of $US0.40 million/ GWh and $US0.24 million/ GWh for storage capacities of 6 GWh and 36 GWh, respectively. Half of the total construction cost relates to the rock cavern part of the store.
The large-scale borehole layer (BTES) in Emmaboda was commissioned in 2010. Its aim was to make use of waste heat from the industrial processes at the Xylem plant. During all the years since its inception, additional heat sources have been included, and only now can the predicted annually amount of stored heat (3.6 GWh/year) be achieved. The average storage temperature is now 40-45oC. Very little of the injected heat has so been recovered (200 MWh) because the storage temperature was lower than expected. The reason for this is mainly that the amount of stored heat (12,000 MWh) is less than expected and that this heat also held a lower temperature than expected. Performed simulations based on actual storage data and presumed future operating data, show that the simulation model reasonably well predicts the future storage function. Initial circulation problems in the storage have been solved with the use of vacuum pumps for degassing of the liquid. The BTES has reduced the amount of annually purchased district heating by about 4 GWh. To further improve the system and reduce the heat losses, it is proposed to install a heat pump to heat withdrawal. This would enable the system to deliver high enough supply temperature for heating of the buildings. The system could then be operated according to planned annual heat injection/ extraction (3.6 GWh/2.7 GWh).
A newly started annex on implementation of underground thermal energy storage is described. The scope of the annex is to conserve energy, improve the environment by facilitating a broader use of Underground Thermal Energy Storage, UTES, in the building, into industrial, agricultural and aquaculture sectors. The objectives are to document successful and promising system applications and to identify boundary conditions, which make UTES economically feasible. The objectives also include proof of UTES environmentally benign by demonstration and information. The work-plan will be performed in several steps from state-of-the-art studies to R and D projects in the way to carry out user-friendly engineering tools and setting market barriers aside. The annex, which will be operated by task sharing, is divided into five sub-tasks with an estimated overall time schedule of three years
Ice storage for cooling is an ancient technology which was common until thebeginning of the 20th century, when chillers were introduced. During the past fewdecades new techniques using both snow and ice for comfort cooling and food storage have been developed. Cold is extracted from snow or ice by re-circulation of water or air between the cooling load and the snow/ice. The snow cooling plant in Sundsvall, Sweden, is used for cooling of the regional hospital. The stored natural and artificial snow is used for comfort cooling from May to August. It was taken into operation in June 2000 and is the first of its kind. Here the plant is described and the experience of its first six years of operation is presented.
Seasonal underground thermal storage is typically achieved through advection in aquifers using wells (ATES), and conduction using boreholes (BTES). When ATES is coupled with heat pump (HP) systems it can result in providing direct cooling, with HPs providing additional cooling during peak conditions, and in the heating mode HPs can benefit from higher ground temperatures for higher efficiencies. Case studies with realized COPs ranging from 8 to 60 are discussed as a range of expected efficiencies. This chapter discusses proper practices for well and well field design, ensuring long-term thermal performance and best practices of optimizing systems for heating and cooling.
Using the ground as a seasonal thermal energy store is referred to as underground thermal energy storage (UTES). In the vast majority of cases, there are only two basic methods of exchanging thermal energy with the ground: through advection in aquifers using wells and conduction using boreholes. They are referred to as aquifer thermal energy storage and borehole thermal energy storage. While heat pumps (HPs) or chillers are not always used in conjunction with UTES, it is the most common application since most buildings have both heating and cooling loads. In designing HP systems for moderate to large size buildings, it is often the case that the cooling demand is larger than the heating thermal energy demand over the year for large buildings; occasionally it is reversed. In addition, community systems with single-family houses and small residential buildings might have a heating-dominated energy demand. This chapter is largely devoted to the former; however, some notable exceptions are discussed as well.
This book was originally published at Luleå University of Technology in 1987 fulfilling a need within Sweden to disseminate the techniques of alternative heating using solar energy in association with energy storage. In the year 2000 it was realised that the book required updating. This second edition contains a number of changes that bring it up to date, and at the same time, it was made accessible to a much wider audience by being translated into English.
The objective of this study was to evaluate a method for continuous measurement of ice cover thickness. The measuring device consists of a water-filled bucket, floating with its brim at the water surface. A pipe is vertically mounted at the centre of the bucket and capped with an oil-filled balloon. The volume expansion of the formed ice results in a corresponding oil flow, from the balloon at the bottom of the bucket through the pipe into an expansion bucket above ground. By measuring the volume expansion continuously, the ice thickness can be determined at any time. The performance of preliminary laboratory tests confirmed the feasibility of the method.
The technology of underground thermal energy storage (UTES) has evolved considerably over the past 25 years. This article reviews this development and summarises the latest technologies and current trends for UTES with heat pumps. UTES is widely used for cold storage and combined cold and heat storage, particularly in Sweden, Canada and the Benelux countries (i.e. Belgium, the Netherlands and Luxembourg). Some new applications are also discussed: industrial process cooling, road de-icing, heat and cold supply at petrol stations, etc. Heat pumps frequently form an integral part of these applications. In addition to this overview, the topical articles found in this issue of the IEA Heat Pump Centre Newsletter give more detail of applied techniques, and present examples from various countries.
An accurate knowledge of aquifers properties is important 2 in many disciplines, from hydrology to site characterization in order to designing and implementing remediation strategies, as well as geothermal ground source technologies. In par5 ticular, the groundwater flow rate is a fundamental parameter to be considered in the ground-coupled heat exchangers (GCHEs) design, together with the thermal properties of the ground. In fact, even relatively low flow rate entail temperature changes considerably lower than in the case of pure heat conduction (Gehlin and Hellström, 2003; Fan et al., 2007) and then relatively stable underground temper10 atures which allow heat pumps to operate with very efficient performance coefficients, thereby reducing energy costs (Lee et al., 2012). Moreover, an accurate knowledge of groundwater velocity and ground thermal properties allows a better design and dimensioning of the GCHE, with further reduction of costs. The objective of this paper is to propose an expeditious, graphical method to estimate the groundwater flow velocity from TRT analysis.
The increasing popularity of ground-coupled heat pumps has resulted in almost20% of all Swedish family houses being heated this way. To avoid undesirableinteractions between neighboring boreholes and disturbance of the ground temperature, the general rule and recommendation of Swedish authorities is that the distance between two neighboring boreholes must be ≥ 20 m. However, according to previous studies, relatively low groundwater flow rates may significantly reduce the borehole excess temperature compared to the case of pure heat conduction. In this work the Influence Length is defined and its relations with flow rate, real thermal conductivity of the ground and effective thermal conductivity obtained by thermal response analysis are investigated. The aim of this study was to find a way to use the thermal response test as a means to determine the groundwater flow influence in order to reduce the borehole spacing perpendicular to groundwater flow direction. The results confirm that very low groundwater flow rates are enough to significantly reduce the Influence Length, hence this is a crucial parameter which should be considered. Moreover, a first estimation, even before the thermal response test analysis, of the Influence Length is possible if the knowledge of hydrogeological conditions of the site allows good predictions about real thermal conductivity of the ground and flow rate.