Danish Energy Agency Research Articles

Prefeasibility study on optimal site location for Power‐to‐X: An experiment for the Danish energy system

Denmark has set ambitious goals to cut greenhouse gas emissions by 70 % by the year 2030, and in an effort to reach this, the Danish Energy Agency has proposed a Power-to-X strategy that involves an overall capacity target of 6 GW of electrolysis by 2030. The objective of the following study was to identify the optimal site location for siting an electrolyser for Power-to-X as a prefeasibility analysis. The results indicated that Jammerbugt was an ideal area, for an add on solution to an already existing wind turbine, with 1303 h of excess wind energy available for Power-to-X. A financial analysis showed that there was an NPV of - €126,032 after a 20-year period, which improves with a theoretical 20 % governmental subsidy to €16,662. Therefore, it was found that Power-to-X is still currently reliant on governmental support as a viable business case. The study's findings highlight the importance of this support for Power-to-X to be a viable business case, such as the decision to allocate 1.25 billion DKK for hydrogen production by 2030.

Experts, stakeholders, technocracy, and technoeconomic input into energy scenarios

This paper confronts the broad question of the nature and quality of the contributions of experts, stakeholders, and the wider public to the development of detailed techno economical inputs used in scenario analyses used for discussions and decisions on the green energy transition and science, technology and innovation (STI) policies in general. The study focuses on stakeholder inclusion in developing the Danish Energy Agency's technology catalogues. The technology catalogues forecasts technoeconomic data up to 2050. The study reviews some well-recognised issues related to the inclusion of experts and stakeholders. The study contributes three new insights. First, a better understanding is developed of how expert and stakeholder inclusion in developing front-end inputs for energy models and scenarios aligns expectations and builds a shared understanding of detailed technoeconomic data. This shared understanding establishes a level playing field for wider public debate on visions for the future energy system. Second, a pragmatic approach is demonstrated for stakeholder inclusion in contexts – such as developing technology catalogues – with limited resources and only a few actors available for consultation. Third, the paper presents the argument that the concept of technocracy can bring useful insights for analysing expert and stakeholder inclusion in longterm energy planning.

(Invited) Sustainable Platinum Group Metal (PGM) Recycling of Proton Exchange Membrane Fuel Cells and Electrolyzer Cells (PEMFCs & ECs) As a Vital Step Towards Truly Renewable and Green Energy Conversion Technologies

Owing to their strong catalytic nature and high robustness under various conditions, platinum group metals (PGMs) are state-of-the-art electrocatalysts for proton exchange membrane fuel cells and electrolyzer cells (PEMFCs & ECs) of superior performance and long stability. However, PGM supplies involving limited natural reserves, energy intensive mining process and related environment issues raise increasing concerns. As an indispensable (though insufficiently developed) aspect of the PEM technologies, sustainable PGM recovery and reuse can fundamentally tackle those concerns and serve as a strong support to further secure widespread commercialization of the technologies.Due to the popular use of perfluorinated sulfonic acid as proton conduction component, PGMs in PEMFCs&ECs are not suitable for recycling through the traditional pyrometallurgical route, which operates at a temperature over 1500°C. Burning of the electrodes releases huge amount of emission, which is not only harmful to the environment and human, but also corrosive to the process infrastructure.An alternative PGM recycling process using a hydro-electrochemical route1, 2 reveals many advantages, including high extraction efficiency, environmental friendliness, recovery of multiple components, low demand for operation conditions & maintenance, etc. Adopting the intrinsic degradation mechanisms of the PGM nanoparticles in combination with surface potential modulation, dissolution behavior of typical PEMFC&EC electrocatalysts have been systematically investigated. Under optimal parameters, a recovery efficiency of over 99% was successfully achieved for platinum electrocatalyst. Moreover, new catalysts prepared from the recycled precursor demonstrated competitiveness to that of commercial equivalents.In project 3R, as a joint effort of fuel cell industries, recycling companies and academics supported by Danish Energy Agency, the achievements document a valuable milestone towards truly renewable and green energy conversion technologies.AcknowledgmentFinancial support from Danish Energy Agency EUDP project 3R, Nr. 64019-0551; Innovation Fund Denmark, InnoExplorer program, Nr. 9122-00112; Danish ESS lighthouse on hard materials in 3D, SOLID, Grant number 8144-00002B; Energi Fyns Udviklingsfond.Corresponding authorShuang Ma Andersen: mashu@igt.sdu.dkReference Sharma, R.; Gyergyek, S.; Andersen, S. M. ChemSusChem 2018, 11, (21), 3742-3750.Sharma, R.; Rode Nielsen, K.; Brilner Lund, P.; Bredmose Simonsen, S.; Grahl-Madsen, L.; Ma Andersen, S. ChemElectroChem 2019, 6, (17), 4471-4482.

Can public agencies facilitate efficient sustainable energy strategies? A climate partnership model

ABSTRACT Can public agencies efficient facilitate sustainable energy strategies that can be used to increase the efficiency of global climate policy? We focus on the specific case of climate partnership between Denmark, a global leader within wind power, and China, the world’s largest CO2 emitter. Based on theory and empirical data, we argue that the strategy of climate partnership can help both partners obtain a more sustainable energy policy with a larger positive effect on climate change as well as increase the income of both state and businesses through an increased level of green exports. The climate partnership model between Denmark and China, as facilitated by the Danish Energy Agency, creates such a win-win situation supported by the main stakeholders. This low-cost policy suggests that public agencies worldwide such as the European External Action Service (EEAS) should expand the number of such efficient climate partnerships.

The SOC4NH3 Project. Production and Use of Ammonia by Solid Oxide Cells

The Danish Energy Agency has sponsored a 4 million € project for production of ammonia synthesis gas and the use of ammonia by Solid Oxide Cells. The purpose of the project is to demonstrate a novel process for generation of ammonia synthesis gas without an air separation unit by means of Solid Oxide Electrolyzer Cells as well as using ammonia as a fuel for Solid Oxide Fuel Cells. The synthesis gas generation plant will be a 50 kW unit. The SOFC unit test will be carried out on one stack corresponding to 1.5 kW. In parallel socio- as well as techno-economic studies will be performed on ammonia as an energy vector for storing excess electricity and using it for shipping, heavy duty transport and stationary power production. The paper and presentation will provide details about the new synthesis gas production process and present experimental results from the ammonia to power part of the project.

Review of hydrocarbon potential in East Denmark following 30 years of exploration activities

Between 1993 and 2017, Denmark was one of the largest oil exporting countries in Europe having gained this position from its share in the highly prolific Danish Central Graben. However, outside the Central Graben few prospects have been adequately mapped, due to a lack of data in these socalled ‘white areas.’ As such, their potential for hydrocarbon accumulation remains uncertain. This paper presents an update of the prospect and play types in this area outside the Danish Central Graben, east of 6°15´E longitude (Fig. 1), based on results from the last 30 years of exploration activities. The paper is part of a resource assessment made by the Geological Survey of Denmark and Greenland (GEUS) to the Danish Energy Agency (Schovsbo & Jakobsen 2017) and is an update of a former review of the area made in 1987 (Thomsen et al. 1987). The succeeding exploration efforts have not changed the overall low expectation for the play types in the area. Here, we show that an uncertain resource is associated with both the Zechstein carbonate play in the North German Basin and the Upper Triassic – Lower Jurassic sandstone and lower Palaeozoic shale gas plays in northern Jylland. However, questions remain as to the source of hydrocarbons in the western offshore area. Specifically, we are unable to confirm (or refute) whether these structures are sourced via long-distance migration of hydrocarbons from the Danish Central Graben.

The impact of socioeconomic and behavioural factors for purchasing energy efficient household appliances: A case study for Denmark

Increasing the share of evermore energy efficient household electric appliances is one strategy to address environmental impacts arising from residential electricity demand. Hence, governments and energy actors are interested in the determining factors behind the consumer choice of conventional versus high efficiency labelled appliances. This study employs empirical survey data from the Danish Energy Agency to model influential factors behind Danish consumer choice of energy efficient appliances. To estimate consumer propensities, we use a logistic regression model over a set of socioeconomic, demographic, and behavioural variables. The study regresses over this unique combination of end-use behavioural variables by creating an energy efficiency index. Statistical results show that housing type, quantity of inhabitants, age, and end-use behaviour are strong predictors for choosing energy efficient appliances. Interestingly, income is a weaker predictor. Despite a relatively wealthy national income and well-educated population, information campaigns have been largely ineffective in driving high efficiency investments. In light of this study's results and exogenous factors such as urbanising demographics and shifting Danish housing stock towards apartments, the study suggests improved information campaigns by targeting key demographics.

Dynamic and Impure Perovskite Structured Metal Oxide Surfaces

During recent years a lot of results on segregation of metal oxide components to the surfaces of perovskite electrodes for solid oxide cells (SOC) have been published. The electrodes are typically of the families (La1-xSrx)sMO3, M = Mn, Fe, Co, Ni with 0 < x < 1, and s is the so-called A/B ratio, usually 0.9 < s < 1.1. M may in principle be a mixture of all four metals, and the mentioned transition metals are only examples. Especially SrO segregations have been reported, but other of the components of the perovskite may also segregate to the surface as well as impurities in the raw materials. Finally, impurities from the reactant gases may adsorb to the surface of such electrodes (1 - 5). However, it has been suggested that e.g. the SrO segregation is due to the vacuum based ex situ analytical tools such as low energy ion scattering (LEIS), x-ray photoelectron spectroscopy (XPS) and time of flight secondary ion mass spectrometry (ToF-SIMS). In general, the literature results are quite scattered, so the issue is still open for discussion.The aim of this paper is to settle this discussion. First a brief summary of some main literature results are given, and next some results of our own on studies on popular commercial perovskite materials are presented and discussed. The methods used are Raman spectroscopy and XRD, which are not vacuum techniques, and ToF-SIMS and XPS, which are vacuum techniques. The conclusion is that usually a perovskite surface will be covered with segregated material of as well components like SrO as impurities in the perovskite starting material. Furthermore, the available evidences point to the perovskite surfaces being very dynamic with relatively fast changes that are visible within periods of few hours with developments continuing for hundreds of hours. AcknowledgementWe acknowledge financial support from Energinet.dk through the ForskEL programme Solid Oxide Fuel Cells for the Renewable Energy Transition contract no. 2014-1-12231, and by The Energy Technology Development and Demonstration Program (EUDP) at the Danish Energy Agency via project “Maturing SOEC”, contract no. 64015-0523. References K. Norrman, K.V. Hansen, T. Jacobsen, RSC Adv., 5, 87679 (2015). F.S. Baumann, J. Fleig, M. Konuma, U. Starke, H.-U. Habermeier, J. Maier, J. Electrochem. Soc., 152, A2074 (2005). J. Druce, H. Tellez, M. Burriel et al., Energy Environ. Sci., 7, 3593 (2014) Z. Cai, Y. Kuru, J. W. Han, Yan Chen, Bilge Yildiz, J. Am. Chem. Soc., 133, 17696 (2011). K.V. Hansen, K. Norrman, T. Jacobsen, Y. Wu, M.B. Mogensen, J. Electrochem. Soc., 162, F1165 (2015).

The rescue of seismic field data from exploration activities in the Danish North Sea

In 2009, the Danish Energy Agency informed the Geological Survey of Denmark and Greenland (GEUS) that a new legal act (Lov om fordring/Forældelsesloven) would become effective in 2011. The new act introduced a limitation period of three years on the government’s right to request data from licensees’ oil and gas activities in Denmark (www.retsinformation.dk 2007), and it became the catalyst for a major change in the standard procedure for licensees’ submission of seismic data related to exploration activities to GEUS. A consequence of the new legal act was that the Danish authorities would have to request data from the licensee (following the Consolidated Act of the Use of the Subsoil) from the licensee no later than three years after their generation or publication; otherwise the authorities would have no legal right to the data. It was emphasised by the Danish Energy Agency that GEUS would have to submit all requests for outstanding data to the licensees no later than 1 January 2011.

Optimizing the supply chain of biomass and biogas for a single plant considering mass and energy losses

The share of renewable energy in the Danish energy sector is increasing and the goal is that biogas production should reach a production level of 17 petajoules (PJ) in 2020 according to the Danish Energy Agency. However, this goal is currently not reachable due to lack of investments in biogas plants.In this paper, a mixed integer programming (MIP) model for finding the optimal production and investment plan for a biogas supply chain is presented to ensure better economy for the full chain hopefully stimulating future investments in biogas. The model makes use of step-wise linear functions to represent capital and operational expenditures at the biogas plant; considers the chain from the farmer to the end market; and includes changes of mass and energy content along the chain by modeling the losses and gains for all processes in the chain. Biomass inputs are scheduled on a weekly basis whereas energy outputs are scheduled on an hourly basis to better capture the changes of energy prices and potentially take advantage of these changes.The model is tested on a case study with co-digestion of straw, sugar beet and manure, considering natural gas, heat, and electricity as end products. The model finds a production and investment plan for a predefined location of the plant within half an hour of central processing unit (CPU) time. The resulting project turns out to be profitable and gives a production plan for each process, which underlines the possibilities of optimizing the processes in a biogas project.

Long-Term Stability of Anode-Supported Solid Oxide Fuel Cells with a Co-Sintered Cathode Backbone and Infiltrated La0.95Co0.4Ni0.6O3 (LCN) Electro-Catalyst

Infiltration is a fabrication method that is offering potentially significant improvements in cell performance at reduced materials and fabrication costs, especially when combined with co-sintering. However, important questions regarding the long-term performance and microstructural stability of infiltrated electrodes, as well as the mechanical properties of such electrodes have remained unanswered.Here, we present the results of a three-year project, where large footprint (12 × 12 cm2) anode-supported solid oxide fuel cells with a co-sintered cathode backbone and infiltrated La0.95Co0.4Ni0.6O3 (LCN) cathode active phase were developed and thoroughly characterized. We report the initial and long-term (1500+ hours) performance of infiltrated cathode backbone cells hours running with 40% H2O/H2 as fuel and ambient air as oxidant, coupled with a scanning transmission electron microscopy - energy dispersive X-ray spectroscopy (STEM-EDS) investigation of microstructural changes in the infiltrated electrodes (Fig. 1). Some electrodes were further aged at elevated temperatures (750- 900°C) for periods reaching up to 5000 hours, while following changes in the electrode properties with scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area, and van der Pauw in-plane conductivity measurements. Finally, the mechanical properties of co-sintered cathode backbone cells were determined in four-point bending tests carried out both at room temperature and at 800°C in air. To our knowledge, this is the first time infiltrated cells have been characterized in such detail. The results of the study suggest that significant coarsening of the infiltrated phase takes place upon long-term testing and aging, resulting in decreased active surface area, reduced in-plane electronic conductivity, increased electrode impedance, as well as re-arrangement of the electro-catalyst in the porous backbone. The Weibull strength of the cells at room temperature was 400 MPa with a Weibull modulus of 12. Both the strength and the modulus were found to be lower at elevated temperature.This study was funded by EUDP (Danish Energy Agency) project 64012-0225 “SOFC Accelerated – Development to Accelerate Field Demonstrations”. Figure 1. STEM-EDS maps of infiltrated LCN cathodes after infiltration (left) and after (right) 1500-h cell-testing. Figure 1

Measurements of the Angular Distribution of Diffuse Irradiance

Abstract Advanced solar resource assessment and forecasting is necessary for optimal solar energy utilization. In order to investigate the short-term resource variability, for instance caused by clouds it is necessary to investigate how clouds affect the solar irradiance, including the angular distribution of the solar irradiance. The investigation is part of the Danish contribution to the task 46 within the International Energy Agency and financed by the Danish Energy Agency. The investigation focuses on the distribution of the diffuse solar irradiance and is based on horizontal measurements of the solar irradiance from 8 different parts of the sky as well as horizontal measurements of the total beam and total diffuse irradiance.

Inbicon makes lignocellulosic ethanol a commercial reality

Based on the IBUS process, Inbicon has built an advanced biorefinery at the port of Kalundborg in Denmark. In this biorefinery Danish wheat straw is converted to second generation (2G) ethanol, lignin pellets and C5 molasses. It is a demonstration plant working 24 h 7 days a week. In this way it is working as a commercial plant, but the size of the plant is not large enough to carry out a feasible production. It is possible to run as a commercial plant as the Danish Energy Agency has granted the design and construction phase and the European Commission's 7th Framework Programme for Energy Research (FP7) has granted the commissioning and first three years of operation.By the end of 2010 the demonstration plant has been totally commissioned and has gone into production phase. The first 2G ethanol has been sold to Statoil and is now distributed in 100 filling stations all over Denmark as Bio95 2G petrol. Lignin pellets are sold to DONG Energy and used as a high-quality solid biofuel in power plants. The C5 molasses is sold as biogas booster in local biogas plants. The demonstration plant has proved continuous operation from straw bales to fermentation and the expected yield of 2G ethanol (>198 L t−1 dry straw).The process is developed, the products are on the market, lignocellulosic ethanol is reality - but in the same way as for almost any other new energy technologies, further policy and market incentives are still needed before investors will construct the first full scale commercial plants.

SCENARIO DEVELOPMENT AND DELPHI APPLICATION IN LIFE CYCLE ASSESSMENT FOR ASSESSING ENVIRONMENTAL IMPACT OF NEW TECHNOLOGY CASE STUDY: REMOVAL OF WIND TURBINES PROJECT

Certain technology is intended to create eco-efficient products or process or is developed as answer to the recent challenge. This kind of technology consequently can also create another impact therefore it shall be assessed and analyzed. The focus of the study is on assessment method namely Life Cycle Analysis (LCA), Scenario development and Delphi application. The objective is to understand benefits and drawbacks of the combined methodology and observe practicality of its implementation for assessing new technology. The distinctive feature comes from the combination of social and technological foresight (as Delphi application) and future studies (as Scenario development) which are applied in the environmental assessment of a product (by Life Cycle Analysis). The utilization of LCA-Scenario-Delphi case study as an explanatory example is presented in the Removal Wind Turbines Project by the Danish Energy Agency. The wind turbine is considered new technology with some of it phases are yet to occur, for example: removal of turbines after phase out stage. Technology Assessment by LCA-Scenario-Delphi is complicated procedure, but necessary to validate the results. The drawbacks of this procedure are extensive time it consumes and the dependency on public participation and/or expert willingness to participate. Nonetheless, its advantages are due to its interactive feature; integration of knowledge from different areas of expertise and its assessment’s characteristic which focuses on process.

A revised lithostratigraphy for the Palaeogene – lower Neogene of the Danish North Sea

Intense drilling activity following the discovery of the Siri Field in 1995 has resulted in an improved understanding of the siliciclastic Palaeogene succession in the Danish North Sea sector (Fig. 1). Many of the new wells were drilled in the search for oil reservoirs in sand bodies of Paleocene–Eocene age. The existing lithostratigraphy was based on data from a generation of wells that were drilled with deeper stratigraphic targets, with little or no interest in the overlying Palaeogene sediments, and thus did not adequately consider the significance of the Palaeogene sandstone units in the Danish sector. In order to improve the understanding of the distribution, morphology and age of the Palaeogene sediments, in particular the economically important sandstone bodies, a detailed study of this succession in the Danish North Sea has recently been undertaken. An important aim of the project was to update the lithostratigraphic framework on the basis of the new data. The project was carried out at the Geological Survey of Denmark and Greenland (GEUS) with participants from the University of Aarhus, DONG E&amp;P and Statoil Norway, and was supported by the Danish Energy Agency. Most scientific results cannot be released until September 2006, but a revised lithostratigraphic scheme may be published prior to that date. Formal definition of new units and revision of the lithostratigraphy are in preparation. All of the widespread Palaeogene mudstone units in the North Sea have previously been formally established in Norwegian or British wells, and no reference sections exist in the Danish sector. As the lithology of a stratigraphic unit may vary slightly from one area to another, Danish reference wells have been identified during the present project, and the lithological descriptions of the formations have been expanded to include the appearance of the units in the Danish sector. Many of the sandstone bodies recently discovered in the Danish sector have a limited spatial distribution and were sourced from other areas than their contemporaneous counterparts in the Norwegian and British sectors. These sandstone bodies are therefore defined as new lithostratigraphic units in the Danish sector, and are assigned Danish type and reference sections. There is a high degree of lithological similarity between the Palaeogene–Neogene mudstone succession from Danish offshore boreholes and that from onshore exposures and boreholes, and some of the mudstone units indeed seem identical. However, in order to acknowledge the traditional distinction between offshore and onshore stratigraphic nomenclature, the two sets of nomenclature are kept separate herein. In recent years oil companies operating in the North Sea have developed various in-house lithostratigraphic charts for the Paleocene–Eocene sand and mudstone successions in the Danish and Norwegian sectors. A number of informal lithostratigraphic units have been adopted and widely used. In the present project, these units have been formally defined and described, maintaining their original names whenever feasible, with the aim of providing an unequivocal nomenclature for the Palaeogene – lower Neogene succession in the Danish sector. It has not been the intention to establish a sequence stratigraphic model for this succession in the North Sea; the reader is referred to the comprehensive works of Michelsen (1993), Neal et al. (1994), Mudge &amp; Bujak (1994, 1996a, b), Michelsen et al. (1995, 1998), Danielsen et al. (1997) and Rasmussen (2004).

Modelling of energy systems with a high percentage of CHP and wind power

This paper presents the energy system analysis model EnergyPLAN, which has been used to analyse the integration of large scale wind power into the national Danish electricity system. The main purpose of the EnergyPLAN model is to design suitable national energy planning strategies by analysing the consequences of different national energy investments. The model emphasises the analysis of different regulation strategies and different market economic optimisation strategies. At present wind power supply 15% of the Danish electricity demand and ca 50% is produced in CHP (combined heat and power production). The model has been used in the work of an expert group conducted by the Danish Energy Agency for the Danish Parliament. Results are included in the paper in terms of strategies, in order to manage the integration of CHP and wind power in the future Danish energy supply in which more than 40% of the supply is expected to come from wind power.

The Challenge of North Sea Oil and Gas

ENeRG, the European Network for Research in Geo-Energy, which groups various European research organizations involved in the development of energy resources contained in the earth's crust, has sponsored a study on The Outlookfor Oil and Gas Production in the North Sea , on behalf of the Commission of European Communities (DG XVII). The Institut français du pétrole (IFP) was the main participant in the group, which included the Centre for Marine and Petroleum Technology (CMPT, formerly PSTI, United Kingdom), Rogaland Research (RF, Norway), the Geological Survey of Denmark and Greenland (GEUS in association with the Danish Energy Agency, DEA, Denmark) and Eniricerche SpA (Italy). The main objectives of this analysis are as follows:- Identify the need for new technologies or technological improvements in order to increase the production of oil and gas in the North Sea. - Forecast recovery levels that result from the implementation of these technologies. - Estimate the impact of these forecasts on the volume of activity and employment in the European oil and gas industry.

Regional income effects and renewable fuels: Increased usage of renewable energy sources in Danish rural areas and its impact on regional incomes

CO 2 emission is a worldwide problem and in the attempt to reduce these emissions, renewable energy sources may be considered serious alternatives to the present usage of fossil fuels. As part of a research programme financed by the Danish Energy Agency, data concerning the different heating technologies based on oil and wood fuels have been collected. Private and social costs are estimated and these economic data are used when analysing regional income effects of increased consumption of fuels (e.g. wood) locally produced. The impacts on income and tax revenues are calculated from multiplier expressions, constructed with rights to the measurement of local effects.

Wave Power Test Plants

Ideas for wave power machines have existed for centuries but have rarely advanced beyond the drawing board. The technology needed to exploit the power of the waves commercially has not been sufficiently developed. A multi-disciplinary technical effort is required to achieve this goal. The structural engineering aspects of wave power conversion alone involve a number of substantial technical challenges. Since the end of the 1970s, wave power conversion has been the object of research in Denmark. In 1988 the consortium Danish Wave Power (DWP), has carried out most of the wave power development in Denmark, supported by the Danish Energy Agency and an electricity company. DWP has chosen to promote the development of second-generation systems based on offshore point absorbers. The main advantage of this approach is that the energy content of waves is far greater further out at sea and suitable locations are easier to find offshore.

Deep wells in Denmark 1935-1990. Lithostratigraphic subdivision

The lithostratigraphic data presented here represent the mid-1991 status of the lithostratigraphic database at the Geological Survey of Denmark. The database comprises basic well information such as well location, company, completion date, depths and seismic two-way travel times to top and base of lithostratigraphic units recognized in the wells. Well location maps, a stratigraphic scheme and a list of selected references are included in the present publication. The aim of the presentation is to make these abundant data available to those working with subsurface geology in Denmark and adjacent areas. The key information are depths and seismic two-way travel times to top and base of lithostratigraphic units. The units are primarily recognized by means of petrophysical wireline logs measured in the wells. The boundaries of the units are indicated by significant changes in log pattern and readings as defined in the relevant publications (see reference list). The stratigraphic subdivision of the individual wells has been undertaken over the years by various geologists at the Survey and the level of subdivision thus depends on the data and time available when the subdivision was made. The database is, however, continuously revised as new wells or further work increase our knowledge of the subsurface. The database contains all exploration and appraisal wells drilled on Danish territory. The wells are included irrespective of whether the purpose was exploration for hydrocarbons, geothermal energy, or investigation of possible sites of waste-deposits or gas-storage. However, the wells drilled on the Tostrup salt structure are not included nor are production, observation and injection wells from oil or gas fields since the additional stratigraphic information provided by such wells is generally limited. Wells related to exploration and production of rock salt are not included in the database; most of these were drilled before 1953 and are dealt with in Sorgenfrei &amp; Buch (1964, Table 1, p. 14-17). Further information concerning available logs, reports, and geological samples obtained from the wells, together with information on casings, bit sizes, and test intervals can be found in the Well Data Summary Sheets, vol. 1-16. These can be ordered from the Geological Survey of Denmark. Exploration data in Denmark are in most cases, subject to a 5-year confidentiality period. Therefore, the tables of wells drilled after mid-1986 only show data released by the Danish Energy Agency, such as location, total depth and lithostratigraphic unit at total depth. A few new wells have been released, however, due to relinquished concessions. These wells (Borg-1, Felicia-I, lbenholt-1, Mejrup-1) are presented with full data sets. Furthermore, DONG has permitted release of data from the Stenlille-2, -3, -4, -5, and -6 wells. The authors acknowledge the work of their colleagues who contributed to the database, especially Ole Vejbæk and Jens Jørgen Møller who initiated the data base together with Jens Christian Olsen. Heinke Andersen, Bent Katz, and Uli Heyden are thanked for technical assistance. Jon Ineson (Geological Survey of Denmark) and Olaf Michelsen (University of Arhus) made valuable comments on the manuscript.