1. Contribution to the Implementation of a Power-to-Gas concept in the Algerian Natural Gas Network Compression Stations.
LEMI
BOUZIANE Abdelkader*, BERRAZOUANE Sofiane, MOHAMMEDI Kamal, BELAIDI Idir
LEMI, M Bougara University Boumerdès Algeria
GOZO, MALTA ANNUAL CONFERENCE February   , 2012
ABSTRACT
Power -2- Gas Concept
The world’s present and future are confronted to serious and urgent environmental problems such as greenhouse effect and global warming, ozone layer destruction, water scarcity, biodiversity reduction, etc. The fossil resources are one of the major contributors to this disaster as they are necessary for the industrialization dynamics. In the same time and while most of OPEC and non-OPEC countries have crossed their “peak oil”, a radical change in energy policies is necessary. In the midterm and long term periods, Natural Gas, and hydrogen in a second step, are one of the energy alternatives that can meet demand and environmental constraints. Preliminary studies have shown that the transport of a mixture of natural gas and hydrogen is possible through the existing natural gas networks without pipeline modification as long as the mass fraction of hydrogen remains sufficiently low. Although hydrogen substitution perturbs little the fluid mechanics constraints of the system, the limitations fall into the tolerance of the construction materials of the pipes, compressors and other elements of the natural gas infrastructures.
Alternatives to the hydrogen transport in Natural gas pipelines are chemical storage concepts like power-to-gas, which interconnect power and gas grids. It enables access to storage and transport capacities of the gas grid to store renewable electricity. The power-to-gas concept includes two production steps: the water electrolysis to produce hydrogen (H2) and the methanation which uses CO2 to create CH4, a synthetic natural gas (SNG; also called renewable methane, or storage gas), and water. For the reconversion of CH4 into electricity, various technologies like gas power stations or gas combined heat and power plants (CHP) are state of the art. The natural gas grid provides an already infrastructure with transport and storage capacities of about. One disadvantage of chemical energy storage is the comparably low conversion efficiency. While the round-trip efficiency of renewable methane or hydrogen storage is about 30 to 40% .
In the future energy systems with high shares of fluctuating renewable energy generation, electricity storage will be attractive for the utilization of surplus energy. In periods of low renewable feed-in, the stored chemical energy can be reconverted into electricity. While German hydro pump storages, electric vehicles or demand side management are able to balance the fluctuating power generation within hours to days, long-term storage, which is able to shift energy over weeks or even month, will be necessary as well in a renewable energy system. Chemical storage concepts like power-to-gas, which interconnect power and gas grids, are able to access the tremendous storage and transport capacities of the gas grid to store renewable electricity (Fig. 1). The power-to-gas concept includes two production steps: the water electrolysis to produce hydrogen and the methanation which uses CO to create methane a synthetic natural gas (SNG; also called renewable methane, or storage gas), and water [1, 2]. For the reconversion of methane into electricity, various technologies like gas power stations or gas combined heat and power plants (CHP) are state of
The natural gas grid provides an already existing infrastructure with transport and storage capacities of about 200 TWh [3]. This storage capacity filled with gas is theoretically able to supply the German electricity demand of about two month in combination with gas power plants. One disadvantage of chemical energy storage is the comparably low conversion efficiency. While the round-trip efficiency of renewable methane or hydrogen storage is about 30 to 40% [2], new build pumped hydro storages achieve efficiencies above 70% [4]. However, if heat is utilized in a CHP process when combusting methane or hydrogen, the overall energy storage efficiency rises to 43-54%
INTRODUCTION
Algeria has 160 trillion cubic feet of proven natural gas reserves, ranking it in the top 10 worldwide. Several contracts with hundreds of millions of dollars are going to be concluded for investments in the gas industry. Feasibility studies are on the way to build a new gas pipeline linking Algeria directly to Europe via Spain. Billion dollar contracts have been signed to develop 7 of 12 existing gas fields in the In Salah area. Other highly valuable investments are under way. Every 200 km we need a compression station for transportation of the natural gas from the fields to the consumers., 5% of the transported gas is consumed for feeding gas turbines combustors which means GHGs emissions. Our contribution aims to help reduce the natural gas self consumption and GHGs emissions reduction of pipelines compression station. The idea is to substitute the gas turbine by a hybrid energy system integrating RE, PV, Wind turbines, Fuel cells. .A micro-grid’s dynamic control method, which secures a real power balance and enhances the operational capability to handle frequency fluctuation in multiple source energy hybrid micro-grid power system, is proposed. The fuzzy controller is introduced to compensate the power fluctuations in micro-grid power systems. Therefore, the proposed control helps to solve power quality issue resulting from real power imbalance fluctuations
CASE STUDY
The hybrid energy system consists of a Diesel Generator DG, Wind Turbine WT, photovoltaic PV, Fuel cell , battery bank, and load. On this system, sum action allow to correct the power produced and power consumed to achieve a balance between production and consumption and thus keep the frequency close to its reference value.
These actions will act on the production of renewable energy, diesel generator and battery bank. The battery and hydrogen tanks energy storage systems are the current attractive means of smoothing intermittent wind or solar power generatio. The DG is used to supply the HES when the other systems cannot sufficiently provide it. In this case, if we have a high variation of fluctuation of renewable sources, the DG turns on/off in short time. That, it is no recommended. Our simulation are done under HOMER environment.
CONCLUSION
Power-to-gas is a meaningful long-term storage option for future low emission energy systems but only a reasonable use will gain systematic and environmental advantages. The system analysis shows power-to-gas only makes sense as long-term storage facility when there is surplus renewable power. Otherwise, a storable fuel is used to create another storable fuel while accepting energy losses. The more detailed analysis by comparing the greenhouse gas emissions of primary power generation and power generation from the later reconversion of the storage gas shows the same tendencies. Consequently, the electricity for the electrolysis operation must be low-emission renewable power, otherwise the direct use of natural gas is not only cheaper but also lower in emissions.
From a systematic point of view a clearly low emission and renewable power-to-gas operation can only be reached when limiting the charging power to system surpluses from renewables, which occur by network congestions for example. Especially in the transition period, when surplus feed-in power becomes more frequent but does not induce economical attractive full load hours for a long-term storage system, additional operation concepts like offering power frequency reserve can increase the full load hours of the power-to-gas plant. In load leveling mode, the power-to-gas plant can
Fig.1: (a) Gaspiplines links from Algeria to Europe, (b) gas and oil fields in Algeria
HOMER Simulation and Optimization
HOMER, which stands for Hybrid Optimization Model for Electric Renewables helps design off-grid and grid-connected systems and performs analyses to explore a wide range of design questions:
• which technologies are most cost-effective?
• what size should components be?
• what happens to the project’s economics if costs or loads change?
• is the renewable resource adequate?
Homer finds the least cost combination of components that meet electrical loads. It simulates thousands of system configurations, optimizes for lifecycle cost, and generates results of sensitivity analyses on most inputs.
HOMER Software is a flexible tool that models a mix of conventional fuels and renewable energy to determine the most cost-effective configuration for each system.
Fig.2:Burj Cedria(Tunisia)Electricity consumption profil
Fig.3: Burj Cedria hourly wind speed data
Fig.4: Burj Cedria hourly solar irradiance data
Fig.5: Burj Cedria hourly ambient temperature data