ABOUT HYDROGEN PRODUCTION
WHAT IS A FUEL CELL?
Fuel cells are an energy conversion technology experiencing a rapid development. Their advantages include quiet operation, a modular construction that is easily scalable and higher efficiencies than conventional energy technologies. Thus, fuel cells are attractive for a wide spectrum of potential applications, including combined heat and power (CHP), distributed power generation and transport. Fuel cells are electrochemical devices which convert the energy of a chemical reaction directly into electricity, with heat as a by-product. They are similar in principle to primary batteries except that the fuel and oxidant are stored externally, allowing a continuing operation as long as fuel and oxidant (oxygen or air) are supplied. Stationary fuel cell systems have been installed world-wide and have demonstrated excellent fuel efficiency and reliability. And fuel cells are also attracting interest for providing portable power for laptop computers, mobile telephones etc.
WHY USE HYDROGEN AS AN ENERGY RESOURCE?
Hydrogen is both an energy vector and a fuel. As the significant secondary energy source, it can store and deliver energy in a usable form. Hydrogen offers several advantages:
It can be produced using abundant and diverse domestic energy resources, including fossil fuels, such as natural gas and coal; renewable energy resources, such as solar, wind, and biomass; and nuclear energy. This diversity of energy supply would mean we do not need to rely on any single energy resource or on foreign sources of energy. Producing hydrogen from renewable and nuclear sources, and from fossil fuel-based systems with carbon sequestration, yields near-zero greenhouse gas or criteria emissions. Hydrogen can power all sectors of the economy – transportation, power, industrial, and buildings.
WHERE DOES HYDROGEN FIT IN AN ENERGY PORTFOLIO?
It is widely believed that our reliance on finite fossil energy is unsustainable, both environmentally and economically, increasing the necessity of nations to explore a wide range of potential energy solutions. Hydrogen could have a significant impact in the transportation market by replacing petroleum as an alternative energy. It carries higher density than pure electrons (more range than battery cars) and it can be produced via renewable energy generation. It could also act as catalyst in the proliferation of other renewable technologies such as wind and solar because of the demand hydrogen production creates for electricity. Therefore, the generation of hydrogen could go hand in hand with some of the other emerging alternative fuel sources. Since much of the success of hydrogen depends on further technological advancements, it is hard to quantify its future role; nevertheless, the R&D of hydrogen has yielded promising results, bolstering the potential of hydrogen as a reliable energy source. As a testament to this, many nations have invested significant funds towards the advancement of hydrogen energy.
WHAT IS THE ENVIRONMENTAL IMPACT OF USING HYDROGEN AS A FUEL?
Hydrogen overall is a very clean fuel. Replacing fossil fuels with hydrogen in providing energy services could bring major environmental benefits, depending on how it is produced. If hydrogen is extracted from a fossil fuel, then often CO2, one kind of Greenhouse Gases, is a by-product of the process, but the level of CO2 emitted in the hydrogen-production process is lowered. And burning hydrogen in the presence of oxygen in a fuel cell produces no harmful emissions. When it comes to hydrogen production, research is underway to combine CO2 sequestration (Carbon capture and storage – CCS) and hydrogen production, drastically reducing Greenhouse Gases emissions. If hydrogen is created from nuclear power of renewables, the process is emission-free, carbon-neutral and has virtually no adverse impact on the environment.
WHY IS HYDROGEN IMPORTANT?
The world’s consumption of energy will only go higher in the coming decades. Conventional hydrocarbon energy sources will become harder to be extracted and price of fossil fuel will become more vulnerable to different shocks and crisis. While research to enhance energy production from renewable energy is ongoing, methods and strategies to store excessive energy and to optimize energy produced are also required to achieve a sustainable economy. Hydrogen is a great candidate to serve as an intermediate energy vector and carrier to optimize energy efficiency, achieve energy sustainability and suitable storage in every sector of the economy. Hydrogen’s potential merits continued research and deployment.
HYDROGEN PRODUCTION TECHNOLOGIES
Hydrogen can be produced from renewable and nuclear energy, as well as the electrolysis of water, and fossil energy. The maturity of hydrogen technologies, whether production or storage related, ranges from the basic research stage through technical and commercial maturity. Biohydrogen and photoelectrolytic production technologies are at the early stage of the research spectrum. Biological organisms can produce hydrogen directly from sunlight and water. In addition, semiconductor-based systems similar to photovoltaics (PV) can be used for hydrogen production. Hydrogen can also be produced indirectly via thermal processing of biomass or fossil fuels. Global environmental concerns are leading to the development of advanced processes to integrate sequestration with known reforming, gasification, and partial oxidation technologies for carbonaceous fuels. These production technologies have the potential to produce essentially unlimited quantities of hydrogen in a sustainable manner.
HOW TO PRODUCE HYDROGEN FROM SPLITTING WATER?
Hydrogen can be produced from the splitting of water through various processes including water electrolysis, photo-electrolysis, photo-biological production and high-temperature water decomposition.
Water electrolysis is the process in which hydrogen is produced from splitting water through the application of electrical energy into hydrogen and oxygen.
Photo-electrolysis of water is the process whereby light is used to split water directly into hydrogen and oxygen. Photo-biological production of hydrogen is combined with photosynthesis and hydrogen production catalyzed by hydrogenases.
High-temperature water decomposition is the process in which water is split under high temperature conditions.
HOW TO PRODUCE HYDROGEN FROM CARBON-BASED MATERIALS?
The two most common fossil fuels used to produce hydrogen are natural gas and coal. For natural gas, the processes involve the conversion of methane and water vapor or oxygen gas into hydrogen and carbon monoxide (CO), which will be further converted to carbon dioxide (CO2) and hydrogen using a water-gas shift reaction. Coal often undergoes a similar reaction requiring high temperature entrained flow process with water vapor. Again, the products are hydrogen and carbon monoxide (CO), which is converted to carbon dioxide (CO2). Hydrogen production from coal is commercially mature but costs more than hydrogen production from natural gas. Carbon dioxide is a major exhaust in all production of hydrogen from fossil fuels; to obtain a sustainable (zero-emission) production of hydrogen, the CO2 should be captured and stored.
HOW TO PRODUCE HYDROGEN FROM RENEWABLE RESOURCES?
Other than producing H2 through water-splitting, many technologies for producing hydrogen from renewable resources are the subject of research and development. One promising renewable resources is biomass, which is characterized as any biological material that is living or recently deceased. Corn, sugarcane, and switchgrass are some of the common forms of biomass. A process similar to coal gasification is conducted to produce a hydrogen-containing gas from biomass. However, one of the significant challenges facing biomass is the quality of the material. Depending on climatic variations, crop type and location the production methods can vary greatly, making it difficult to gain consistency in product quality. Biomass collection is still viewed as a great challenge.
HYDROGEN STORAGE TECHNOLOGIES
Storage of hydrogen is an important area for cooperative research and development, particularly when considering transportation as a major user and taking the need for efficient energy storage for intermittent renewable power systems into account. Although compressed gas and liquid hydrogen storage systems have been used in vehicle demonstrations worldwide, issues of safety, capacity, and energy consumption have resulted in a broadening of the storage possibilities to include metal hydrides and carbon nano-structures. Stationary storage systems that are highly efficient and that have quick response times will be important for incorporating large amounts of intermittent PV and wind into the grid as base-load power.
Gaseous hydrogen usually involves being stored in steel tanks, or composite tanks that are made of a various series of material or composites such as carbon fiber and designed to endure higher pressure. Cooling gaseous hydrogen to near cryogenic temperatures is another option. There are two main challenges: first, the safety concern of the highly flammable gas rapidly escaping in an accident. The second challenge is meeting the vehicle range requirements with a storage device conformed to available space. A more novel concepts being tested is the use of glass microspheres. The main problems are the glass microspheres slowly peak hydrogen and are easy to break during cycling. Storage of hydrogen in solid materials has the potential to become a safe and efficient way to store energy, for both stationary and mobile applications. The suitable materials include: carbon and other high surface area materials; H2O-reactive chemical hydrides; thermal chemical hydrides; and rechargeable hydrides. These materials are utilized because of their ability to react or absorb with hydrogen and to subsequently be subjected to another reaction, which removes the hydrogen back out of the material when it is needed for fuel. Compared to gaseous and liquid hydrogen storage, solid hydrogen storage is on its very early development. However, it has the potential advantage of lower volume, lower pressure and higher purity hydrogen output. Currently, the most-developed option is metal hybrids. Options include cooling down hydrogen to cryogenic temperatures and storing it as a constituent of other liquids such as NaBH4 and rechargeable organic liquids. Although liquid hydrogen has a much better volumetric density than gaseous hydrogen, 30-40% of the energy is lost when creating liquid hydrogen. Often liquid hydrogen is stored in super-insulated cryogenic containers in order to maintain the low temperature needed for its liquid state. One advantage of liquid hydrogen is the relatively low pressure required for its storage, which alleviates some of the safety concerns that affect gaseous hydrogen. NaBH4 and rechargeable organic liquid can guarantee a safe and controllable production of hydrogen, but in general, along with cryogenic hydrogen, these processes require safe and well-organized industrial infrastructures, which are quite costly.
HYDROGEN UTILIZATION TECHNOLOGIES
Achieving the vast potential benefits of a hydrogen system requires careful integration of production, storage and end-use components with minimized cost and maximized efficiency, and a strong understanding of environmental impacts and opportunities. System models combined with detailed life cycle assessments provide the platform for standardized comparisons of energy systems for specific applications. Individual component models form the framework by which these system designs can be formulated and evaluated
HOW IS HYDROGEN CURRENTLY BEING USED?
There are two primary uses for hydrogen currently. One is making ammonia (NH3), which is used directly or indirectly as fertilizer, to satisfy the growing demand from intensive agricultural usage. The other one is hydrocracking and hydrotreatment, processes by which heavy fossil fuels are converted into lighter and more suitable forms.
OTHER USES OF HYDROGEN
Hydrogen has the potential to provide energy to all sectors of the economy: transportation, buildings and industry. It can complement or replace network-based electricity – the other main secondary energy carrier.
Hydrogen can provide storage options for renewables-based electricity technologies such as solar and wind. Besides, as input to fuel cell, it can be converted back to electrical energy in an efficient way in stationary or mobile applications.
Hydrogen may also be an attractive technology for communities cannot economically be supplied with electricity via a grid. Because hydrogen can be produced from a variety of energy sources including fossil, nuclear or renewable energy it can reduce dependence on imports and improve energy security.