Metrology for Smart Gas Distribution Grids

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Natural gas and in the future, gas from renewable sources, play a crucial role in Europe’s energy supply, both in industry and in households. 24.8 % of the primary energy consumption is provided by natural gas. At the end of 2008 the total number of gas customers connected to the EU27 natural gas grid was 112 503 900 customers, serving approximately 210 million individual consumers. The pipeline length of the EU25 natural gas grid (in 2005) amounted to 139 984 km for transmission and 1 189 265 km for distribution.
In January 2007 the European Commission adopted a communication proposing an energy policy for Europe, with the goal to combat climate change and boost the EU’s energy security and competitiveness. Natural gas and biogas play an important role in this scenario, because their use causes intrinsically less pollution than other fossil fuels. Gas from different sources has different and even changing composition, and hence calorific value. The physical properties of the gas also vary, impacting on the calorific value. With the liberalisation of the gas market in Europe, the gas qualities fed into the network will become increasingly diverse. In case of (natural or bio) gas transportation and distribution the grids are currently under-instrumented for the future requirements with regard to the measurement of gas composition and properties. There is a clear need for the development of capability to generate metrological and reliable quantitative information suitable for legal and contractual use, grid
control and prediction of spatial distribution in the network, based on a combination of advanced modelling and measurements in under-instrumented grids. Many, especially large gas companies, already use network state simulation software for dispatching purposes. With a set of comprehensive boundary conditions these state simulations can be used to calculate the calorific value and other gas quantities and, thus, the energy content of a gas portion when it is travelling through the grid to the customer. These boundary conditions, encompassing a very large number of precise measurements in the grid at many locations, are required to provide sufficient reliability to enable the calculated values to be used for billing purposes under legal control. When the required boundary conditions cannot be met completely the state simulation is not conclusive and cannot reliably be applied for contractual and legal purposes in distribution grids.
However, in recent years, progress has been made which is applicable in the case of under-instrumented networks. This development is due to progress in the theory and practice of numerically solving differential equations and in control theory. In particular the improved understanding of probabilistic differential equations achieved in recent years and the development of model-based Bayesian state-estimators for dynamic and distributed measuring systems promise to facilitate further progress in gas-grid reconstruction and simulation. Additionally, these techniques and tools will allow for processing uncertain and incomplete input information as well as providing the knowledge about relevant energy and transportation quantities (output quantities) by their degree of belief and uncertainties, respectively, as quality parameters. The latter is an indispensable prerequisite for establishing both metrological traceability and legal reliability. With the future introduction of smart gas meters in the households, state reconstruction might even be possible at the household level. The improvement of both network control and energy measurement/accounting is related directly to the savings that producers and users can earn from better knowledge of the state and distribution of energy and other relevant quantities in the grid and their particular extraction respectively. Along with better knowledge of the energy delivery and consumption costs, this allows for significant savings in production and distribution as well as on the consumption side.

 

Source:
Description of the Call for Joint Research Projects for ENERGY 2009 Topic 8 Metrology for Smart Gas Distribution Grids, EURAMET - European Association of National Metrology Institutes
Link to full-version:
http://www.emrponline.eu/energycall/docs/srt/srt08.pdf


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