Thomas Grube

Closing the loop: captured CO2 as a feedstock in the chemical industry

The utilization of ‘captured’ CO2 as a feedstock in the chemical industry for the synthesis of certain chemical products offers an option for preventing several million tons of CO2 emissions each year while increasing independence from fossil fuels. For this reason, interest is increasing in the feasibility of deploying captured CO2 in this manner. Numerous scientific publications describe laboratory experiments in which CO2 has been successfully used as a feedstock for the synthesis of various chemical products. However, many of these publications have focused on the feasibility of syntheses without considering the ancillary benefits of CO2 emissions reduction if the CO2 is sourced from effluent or the potential profitability of this process. Evaluating these environmental and economic benefits is important for promoting the further development of benign CO2 applications. Given the multitude of CO2 utilization reactions in the laboratory context, an initial assessment must be undertaken to identify those which have the most potential for future technical exploration and development. To achieve this, 123 reactions from the literature were identified and evaluated with the help of selection criteria specifically developed for this project. These criteria incorporate both the quantitative potential of reducing CO2 and possible economic benefits of these syntheses. The selected reactions are divided into bulk and fine chemicals. Of the bulk chemicals, formic acid, oxalic acid, formaldehyde, methanol, urea and dimethyl ether, and of the fine chemicals, methylurethane, 3-oxo-pentanedioic acid, 2-imidazolidinone, ethylurethane, 2-oxazolidone and isopropyl isocyanate, mostly fulfil the selection criteria in each category.

Fuel cells for mobile and stationary applications - cost analysis for combined heat and power stations on the basis of fuel cells

Abstract Highly efficient energy conversion systems with fuel cells for vehicles and stationary applications are currently being discussed all over the world as a technology which will be able to reduce primary energy demand and emissions of limited and climate-relevant pollutants. The high flexibility of fuel-cell systems with respect to energy carriers opens up possibilities of modifying the energy market in the long term. New environmental legislation, above all in the USA, stipulating the introduction of emission-free cars from 2003, has led in the transport sector to an intensified search for alternatives to conventional drive concepts. In stationary applications, numerous demonstration plants and some field tests already implemented reflect the developmental stage of fuel-cell systems. In Germany, a new combined heat and power (CHP) plant modernisation law has been enacted. This act is of special significance for the market launch of fuel cells. A major milestone on the road to market success for all the above-mentioned systems—in order to compete with conventional technologies—is the reduction of costs. In this contribution systems analyses for mobile and stationary applications of fuel-cell systems are presented as well as economic analyses for different fuel-cell systems for stationary applications. In particular, CHP generation based on natural gas as the energy carrier is performed.

Fuel cell power trains for road traffic

Legal regulations, especially the low emission vehicle (LEV) laws in California, are the driving forces for more intensive technological developments with respect to a global automobile market. In the future, high efficient vehicles at very low emission levels will include low temperature fuel cell systems (e.g., polymer electrolyte fuel cell (PEFC)) as units of hydrogen-, methanol- or gasoline-based electric power trains. In the case of methanol or gasoline/diesel, hydrogen has to be produced on-board using heated steam or partial oxidation reformers as well as catalytic burners and gas cleaning units. Methanol could also be used for direct electricity generation inside the fuel cell (direct methanol fuel cell (DMFC)). The development potentials and the results achieved so far for these concepts differ extremely. Based on the experience gained so far, the goals for the next few years include cost and weight reductions as well as optimizations in terms of the energy management of power trains with PEFC systems. At the same time, questions of fuel specification, fuel cycle management, materials balances and environmental assessment will have to be discussed more intensively. On the basis of process engineering analyses for net electricity generation in PEFC-powered power trains as well as on assumptions for both electric power trains and vehicle configurations, overall balances have been carried out. They will lead not only to specific energy demand data and specific emission levels (CO2, CO, VOC, NOx) for the vehicle but will also present data of its full fuel cycle (FFC) in comparison to those of FFCs including internal combustion engines (ICE) after the year 2005. Depending on the development status (today or in 2010) and the FFC benchmark results, the advantages of balances results of FFC with PEFC vehicles are small in terms of specific energy demand and CO2 emissions, but very high with respect to local emission levels.

Kosten der Wasserstoffbereitstellung in Versorgungssystemen auf Basis erneuerbarer Energien

Als Speichermedium fur Energie aus erneuerbaren Quellen eroffnet Wasserstoff eine effiziente Perspektive zur Nutzbarmachung uberschussiger Stromproduktion. Zusatzlich kann die Verwendung dieses Wasserstoffs im Kraftstoffmarkt zur Reduzierung von Treibhausgasemissionen und Importabhangigkeiten substantiell beitragen. Der Einsatz von Brennstoffzellen im Kraftfahrzeugbereich hat insbesondere aufgrund der grosen Reichweitenvorteile ein hohes Potenzial auf dem Markt fur E-Mobilitat. Damit die Anwendung dieser Wasserstofftechnologien moglich wird, mussen noch wesentliche Schritte getan werden, die hinsichtlich der Kostendimensionen der zukunftigen Wasserstoffnutzung im dann vorhandenen Versorgungssystem abzuschatzen sind. In der Vergangenheit sind Wasserstoffbereitstellungspfade fur Verkehrsanwendungen bereits intensiv analysiert und diskutiert worden. Fortschritte bei der Entwicklung der benotigten Anwendungstechnologien aber auch veranderte energiestrategische Randbedingungen motivieren zu der nachfolgenden Analyse und Bewertung. Deren Ausgangsbasis bilden aktuell verfugbare Studienergebnisse, die sich schwerpunktmasig mit der Nutzung uberschussiger Stromproduktionen aus erneuerbaren Energien beschaftigen.

An option for stranded renewables: electrolytic-hydrogen in future energy systems

Future energy systems will likely be challenged by large quantities of stranded renewable electricity that cannot be used in the conventional electrical grid. Using surplus electricity for electrolysis and thereby producing hydrogen is seen as a valuable solution functioning as an energy storage and transport medium and providing other sectors, such as transport or industry, with required feedstocks at the same time. In this study, we suggest using a set of assessment tools to highlight the quantitative potential, cost and environmental performance of electrolytic hydrogen production, transmission and storage. Our approach employs power sector modeling for Germany with three sequential elements: (i) a market model, (ii) power flow modeling, and (iii) re-dispatch modeling. The results were then used to identify suitable locations for large scale electrolysis plants. Electrolysis, large-scale gas storage, a transmission pipeline and other system components were scaled-up and the total cost was calculated. In a final step, we looked at greenhouse gas emissions as one of the major aspects regarding the environmental performance of the hydrogen delivered. Based on our analysis, annual hydrogen production rates of up to 189 kilotons have been determined for the state of Schleswig-Holstein, which exhibits the largest potential for utilizing surplus power from renewables. The economic analysis reveals a hydrogen cost of 3.63–5.81€ kg−1, including installations, for large-scale storage and transmission. If surplus power from renewables is used for hydrogen production, the total greenhouse gas emissions of hydrogen provision were determined to be up to 435 gCO2-eq. kg−1. Using grid electricity, this value increased to some 17 000 gCO2-eq. kg−1.

Costs of Making Hydrogen Available in Supply Systems Based on Renewables

A complementary supply system consisting of electric power and hydrogen can solve the challenge of integrating renewable power into various economic sectors. In the transportation sector, direct-hydrogen fuel cell systems allow for highly efficient and clean transport systems, thus significantly reducing the demand for crude oil-based transportation fuels. One of the key factors for market success of hydrogen technologies is the cost of hydrogen at refueling stations, another key factor is the introduction of fuel-cell vehicles into the market. On the basis of a literature study, the following chapter will show that particularly in the transport sector, it is possible to achieve competitive cost levels compared to today’s transportation fuels. Information about individual elements of the various hydrogen value chains under consideration as well as the results from studies that focus on integrating hydrogen into future energy systems were analyzed with respect to greenhouse gas emissions and cost.