|by Kas Hemmes, Projectleader, VG2 the greening of gas|
TPM Coordinates ‘The Greening of Gas’ Project [VG2]
|To mix hydrogen into the domestic gas network: that is the challenge that those taking part in the EET-subsidized project, ‘The Greening of Gas’ have set themselves. Project coordinator Dr Kas Hemmes (Associate Professor with the Energy and Industry section) describes the many technical and administrative difficulties of this promising idea.|
Under the Kyoto Climate Treaty, the Netherlands is expected to reduce its emission of greenhouse gases by six per cent (compared to 1990 levels). The main greenhouse gases produced by the combustion of fossil fuels such as oil, gas and coal are NOx (nitrogen oxides), SO2 (sulphur dioxide) and CO2 (carbon dioxide). The idea of using hydrogen as a supplementary energy source emerged in the 1970s. Hydrogen has a significant advantage in that its combustion produces only water and no greenhouse gases. “Because the environmental benefits are so obvious, some people do not understand why the idea was not implemented a long time ago,” states Kas Hemmes. “Perhaps they think we can just dig a well and pump hydrogen out. Unfortunately, it’s not that simple. Pure hydrogen does not occur naturally. It has to be derived from other energy sources such as natural gas, coal or biomass. It can also be extracted from water by means of electrolysis.”
Hemmes, who studied experimental and theoretical physics in Groningen, gained his doctorate in 1986 with his research into magnetic recording. However, he soon became interested in energy research. For fifteen years, he conducted research into fuel cells with the Material Sciences and Engineering department of Delft University of Technology. For the last eighteen months he has been involved in the systems design for a national hydrogen distribution infrastructure and the design of transition processes towards a hydrogen economy. This work has been conducted within TPM as part of the ‘Greening of Gas’ project, financed by the Ministry of Economic Affairs, the Ministry of Education, Culture and Science and the Ministry of Housing, Spatial Planning and the Environment (VROM) under the Economy, Ecolgy and Technology (EET) programme.
The use of hydrogen as an energy source is not only hampered by its limited availability. Another problem is that it is difficult to store or trans-port in large quantities. “If we want to use hydrogen on a large scale, there would have to be a network of pipelines covering the entire country,” explains Hemmes. “Needless to say, this would entail a huge investment. Our idea therefore becomes even more attractive: we are investigating the possibility of using the existing gas infrastructure. By mixing hydrogen into the natural gas, at least the transport problem is solved.” Because this ‘new look at the hydro-gen economy’ entails investigating a large number of technical and administrative considerations, the project has been split into two parts. The technical questions are being addressed by the Delft Laboratory for Process Equipment, (API), the Faculty of Civil Engineering and Geosciences, Electrabel, EcoCeramics, the Netherlands Organization for Applied Scientific Research (TNO), Gasunie and the Universities of Groningen and Eindhoven. These partners are concerned with such aspects as fundamental combustion research, the effect of hydrogen/ biogas/natural gas mixtures on pipeline materials, gas turbines and gas-fired engines, research into new burner types, and the safety aspects of transporting and distributing hydrogen-rich gas mixtures.
The other part of the project, coordinated by Dr Hemmes, involves TPM working alongside Hoek Loos, the Faculty of Civil Engineering and Geosciences, Schouten Research, Energy + i.d. and the City Of Rotterdam Port Authority (GHR). It is primarily concerned with infrastructural development in the technical, socio-economic and juridical contexts. Research is being conducted into the costs-returns ratio, national and international legislation, and the impact of the liberalization of the gas market. “From the technical perspective, mixing hydrogen with natural gas in the existing network could well prove the best solution, but this does not necessarily mean that it will actually be implemented. There are many factors to be taken into consideration. We live in an era in which economic interests are paramount. Everything must be cost effective and market forces must be allowed to prevail. We are looking at both the demand and supply side of hydrogen/ natural gas mixtures. We are designing a suitable infrastructure and conducting dynamic modelling for the transition process. In the final phase, we hope to implement our ideas in the Rotterdam harbour district.”
First and foremost, TPM’s part of the project involves investigating existing and potential hydrogen production techniques. These include the ‘non-conventional’ techniques such as extracting hydrogen from biomass. If this is indeed feasible, countless interesting scenarios emerge. “Suppose a group of farmers have a pile of surplus biomass which is serving no other purpose. They could use it to produce hydrogen which they will then add to the gas network, wherever they happen to be. This may seem somewhat far-fetched, but in the new liberalized gas market anyone will be allowed to produce and supply gas, in theory at least. Of course, existing legislation must be observed.
Gas must comply with certain quality requirements and must have a certain calorific value, as expressed by the Wobbe index. It is still uncertain whether natural gas to which hydrogen or biogas has been added will meet the quality requirements. If not, it may be appropriate to amend the legislation allowing gas of a different quality to be supplied. At the moment, the standard is the ‘Slochteren norm’, with all domestic gas-burning equipment and most industrial equipment designed, built and regulated accordingly. We simply do not know whether consumers and industrial users will be prepared to convert to new burners and gas turbines, as they were required to do in the 1960s when the Slochteren gas pocket first came ‘on line’.”
Consequences for the infrastructure
The addition of hydrogen to gas would not be without consequences for the existing gas infrastructure. Hydrogen has a lower calorific value than natural gas, which means that volumes must be increased.
Hydrogen-powered buses in Germany
|Kas Hemmes gives a brief refresher course in chemistry: “Natural gas is actually methane, or CH4, a com-pound of one part C and two of H2. One part of H2 has roughly one third of the calorific value of CH4. This means that if you add ten per cent hydrogen (by volume) to the natural gas, you have added only three per cent energy value. In order to main-tain the same calorific value, you have to transport a much higher volume of gas. It is not certain whether the existing network of pipes would be able to cope.”|
Another interesting research question with regard to the infrastructure is where the hydrogen should be physically introduced to the network. Gas is always transported in only one direction along each pipe, whereby the hydrogen can only be added ‘upstream’. This is the major difference between gas and electricity, which in theory can be returned from any point in the network.
The sub-project ‘Demand-side Analysis of H2/NG Infrastructure’ (NG stands for Natural Gas) is studying the possible applications for the hydrogen/gas mixture. Could consumers use it to fuel a central heating boiler? Would industry be better off, or would the disadvantages outweigh the benefits? “Of course, we want to ensure that there are only advantages,” states Hemmes, “since this would represent a significant motive for getting the process off the ground. For industry, it is extremely important that the use of hydrogen serves to reduce CO2 emissions, as this will enable future economic gains to be made. The Vogtländer Commission, appointed by the Ministry of VROM, favours a system of trading in ’emission rights’. This could prove a valuable and efficient instrument in tack-ling the emission of greenhouse gases. Companies which produce relatively little CO2 could make extra profit by selling their emission rights, their ‘quota’ as it were. This system is particularly interesting for the metals industry and companies such as Corus, which use cokes to convert metal oxides into the finished product, thus producing enormous quantities of CO2.”
“In the long term, it seems economically viable for industry to convert, at least partially, to the use of hydrogen/ natural gas mixtures. Unfortunately, this is not the case in the short term. We run up against a paradox. A familiar industrial process whereby hydrogen can be produced from natural gas itself is steam methane reforming. The petrochemicals industry uses this process on a large scale to remove sulphur compounds from crude oil. However, it always entails conversion losses: twenty per cent of the energy is simply lost. In the first instance therefore, if industry wishes to convert to the use of hydrogen, greater quantities of natural gas will be required, which will cost more.”
It is therefore extremely important that additional benefits are created for hydrogen mixtures, apart from the reduction in diffuse CO2 emissions. The transition process must include incentives to encourage consumers and industry to adopt the new fuel form. Transition -management and dynamic modelling of transition processes fall within the TPM sphere of expertise. What technical and administrative instruments can serve to promote a government objective such as emissions reduction, and how can one monitor the results? Kas Hemmes suggests one possibility: “If hydrogen is introduced to the main gas net-work, every household and every company in the Netherlands will be able to use it. One of the concepts we are investigating is that of micro-generation. Every building would have a fuel cell powered by hydrogen and producing electricity. Some energy is converted into heat during this process and would normally be lost. In our system, it can be used for heating. The gas is therefore used to the full. Because H2 will already be in the gas, no reformer (a sort of miniature chemical conversion plant) will be required. The fuel cell will filter the hydrogen out, as it were.”
Another possible application for the mixture is as an automotive fuel. A 80/20 mixture of hydrogen and natural gas (which is already on the market under the trade name ‘Hythane’) has extremely good combustion properties. It has lower NOx emissions, whereby great environmental gains can be made when used in cars with an internal combustion engine. Moreover, provided good separation techniques become available, the hydrogen can be extracted from the mixture for use in electric cars equipped with fuel cells. Research is also being conducted into possible industrial uses for the CO2 which is a by-product of hydrogen production. This could be used in oil and methane abstraction processes.
Hemmes concedes one fundamental problem in all this. “Although the addition of hydrogen to the gas net-work does seem to have some major advantages, there is a danger that this approach will lead to ‘path dependency’. It would stand in the way of a transition to a 100% hydrogen economy, since once the proportion of hydrogen in the mix has been established, it will not be possible to increase this time after time. Doing so would require further modifications to industrial gas turbines, which is an extremely expensive undertaking.
There is a very high likelihood that if this option is adopted, the percentage of hydrogen in the mix will be pegged at 5 or 10% for ever more. A one-step transition may therefore be preferable. We in the department of TPM are working alongside our partners to identify the pros and cons of all the various options.”
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