| Hydrogen Essay, Research Paper
ANALYSIS
The Potential Markets For Non-Fossil Fuel Hydrogen
?Hydrogen, most of it produced from fossil fuels, is already widely used in the chemicals industry, notably in the
manufacture of fertilizers and petrochemicals. It would therefore be possible to substitute NFFH in this market.
However, the total that could be absorbed by 2040 is unlikely to represent more than about 3% of current total world
energy demand.
?NFFH could be used to satisfy much of the demand for heat. The existing UK natural gas distribution network could, for
instance tolerate the addition of up to 10% by volume of H2 . Higher concentrations would require a major investment
program, while the distribution of pure H2 hydrogen would require a totally new pipeline system.
?Perhaps one of the main future markets for NFFH is in the production of synthetic fuels from coal. This would reduce the
CO2 emissions normally associated with such processes, but would only become a viable option if limitations in the
supply of hydrocarbon fuels coincided with a requirement to reduce CO2 emissions.
?The use of H2 as a transport fuel is a possible option. It offers the potential for a marked reduction in both local and
global emissions and has already been used successfully in demonstration fleets powered by modified internal
combustion engines.
The main problems facing this technology are the comparatively large volume, weight and cost of on-vehicle storage and, for
passenger cars, the high infrastructure costs of a distribution system. For these reasons, buses and commercial vehicle fleets are
the most favorable applications. The future for this application will also be influenced by the development of fuel cells, which would
increase the efficiency of fuel utilization. However, the first practical application of fuel cells might involve alcohol fuels or natural
gas.
Hydrogen Production Methods
H2 can most economically be produced from natural gas, although refineries commonly obtain their process hydrogen in-house,
from the partial oxidation of fuel oil. H2 can also be produced by gasifying coal. Such production techniques do, however, give rise
to CO2 emissions and the future development of H2 technologies is more likely to depend on production from non-fossil fuel
sources. Two such sources are under development: biomass and water.
Although the technology is only at the demonstration stage, H2 can be produced by the gasification of biomass. This procedure,
however, only comes into the non-fossil fuel category if the biomass production does not itself involve the consumption of fossil
fuels.
The other important route for the production of H2 involves the electrolysis of water. This technique is already being applied in
locations close to sources of cheap electricity. Plant energy efficiencies of 70-75% are currently being achieved in practice, and
efforts are being made to enhance process efficiency by improving cell designs and increasing cell temperatures. Efficiencies of
93-98% have been demonstrated in the laboratory, but these have yet to be tested in a full-scale application. Solid polymer and
solid oxide electrolyte systems are also being investigated as possible methods of improving efficiency. Some indication of the
relationship between efficiency, electricity prices and H2 production costs is given in Table 1 .
In order to try to circumvent the inefficiencies of electrical power generation as well as electrolysis inefficiencies, much research
has been devoted to the thermochemical production of H2. Although the principles have been successfully demonstrated in pilot
plants, efficiencies are lower than those achieved in the best electrolysis plants and capital costs are likely to be higher.
Furthermore, the most promising of the thermochemical techniques involve the use of high-grade heat, and some difficulty exists
over finding an economic non-fossil fuel source of such heat.
Hydrogen Distribution and Storage
The most appropriate methods of H2 distribution and storage depend on the form in which it is required, and the size and location
of the market.
Pipelines normally offer the cheapest method of long-distance, overland transport, although usually only for H2 in its gaseous
form. It is cheaper to transport liquid H2 in road or rail tankers. Satisfactory transport by sea requires either liquefaction or the
preparation of a hydrogen-rich chemical ‘carrier’ such as ammonia.
Where H2 is derived using electrical power, direct transmission of the electricity to a market-located production site must he
considered as a possible alternative. This is unlikely to be the most economic option for distances exceeding 1,350 km, although
other factors may also need to be taken into consideration, including the terrain to be crossed and H2 demand characteristics.
Storage costs depend on the quantity of H2 to be stored, its physical form and the duration of the storage. Depleted gas wells are
the most economical method of large-scale storage, although surface storage in pressurized gas containers is feasible in the short
term. Cryogenic containers are required for long-term surface storage.
Imported Hydrogen – A Means of Importing Non-Fossil Fuel Energy
It has already been stressed that, for environmental reasons, any increased use of H2 technologies must be associated with
non-fossil fuel production. The two main sources of non-fossil electricity are hydro power and nuclear energy. Together these
account for about 11% of the world’s energy supply. Alternatives are also being developed, including wind power, biomass and
solar power. However, many of the best locations for renewable energy production lie outside the UK and can only effectively be
‘imported’ via the products made from them.
Cost estimates have been prepared for two possible scenarios:
?the importing into the UK of H2 produced in Canada using low-cost electricity (0.98p/kWh)
?the importing into Europe of H2 produced in North Africa using low-cost solar power (1.2-4.7p/kWh).
The cheapest method of importing H2 from Canada is in the form of liquid ammonia. The estimated cost is ?15.90/GJ, including
back conversion to 99% hydrogen and assuming an 8% discount rate. The cost of importing from North Africa is estimated at
?8.00-?18.60/GJ, depending on the cost of electricity. These costs should be compared with that of petrol, about ?5.00/GJ (1990
unleaded), before UK taxes.
Potential Contribution of Hydrogen Technologies to the UK Energy System
The potential contribution of H2 technologies to the UK energy system was determined on a least cost basis using the MARKAL
energy system model. The analysis has been based on the following assumptions:
?no dramatic changes in the under-lying factors affecting the energy market over the time-frame of the study
?the continuing development of renewable energy technologies onshore wind, tidal, small- and large-scale hydro,
photovoltaics, biofuels, waste incineration and wave energy
?the possibility of two potential development rates for nuclear energy: one assuming three additional pressurized water
reactors over the time-frame of the study, and one assuming the construction of up to 15GW of additional capacity in
each five-year modeling period
[Non-fossil Fuels]
Electrolysis EfficiencyElectricity Price 1.2p/kWhElectricity Price
4.7p/kWh
71%6.0 – 6.519.7 – 20.2
92%4.8 – 5.215.4 – 15.9
Table 1. Hydrogen Production Costs (at discount rates of 8% and 15%) ?/GJ
the possibility of producing H2 using off-peak electricity from the Grid
?the possibility of producing H2 from dedicated photovoltaic power stations
?the importation of renewable derived H2 and ammonia from 1995 onwards
?two possible gaseous H2 costs: ?10/GJ and ?20/GJ
?the continued existence of current markets for H2 – refineries and ammonia production
?the continued development of H2 for transport use
?the possible substitution of up to10% H2 in the natural gas system
The model considered four possible CO2 emissions scenarios
?no constraints
?emissions growth limited to a maximum of 0.3%/year
?emissions held constant at the 1990 level
?emissions reduced to 50% of 1985 levels by 2050.
The results showed that H2 technologies were not selected for the first two emissions scenarios.
With emissions held at the 1990 level and a low nuclear build rate, the model suggested that low-cost H2 would be imported after
2035 for use in oil refineries and for substitution in the natural gas grid. Imported non-fossil ammonia would he used after 2030.
With a high nuclear build rate however, H2 technologies were not selected.
The C02 emissions reduction scenario resulted in a significant uptake of H2 technologies by the model. This scenario also required
a high nuclear build rate and the considerable deployment of renewable technologies beyond 2030. The lower H2 import costs
also supported a more widespread use of this fuel for transportation.
Overall, the model has shown that H2 technologies are not likely to be selected until substantial CO2 emissions constraints are
imposed.
They are then likely to be introduced in the following order:
?the liquefaction of H 2 produced from natural gas for use in fuel cell buses
?the import of low-cost H 2 and ammonia produced from non-fossil fuel energy sources
?the mixing of H 2 with natural gas and the use of NFFH in oil
?the use of NFFH to fuel buses, heavy goods vehicles and cars.
Significantly, the model showed that none of the technologies were likely to be taken up before 2025 and that no significant
adoption was likely before 2035. In no case was H2 likely to be produced in the UK from Grid electricity or dedicated photovoltaic
plant.
Global Warming Projections
Worldwide adoption of the four CO2 reduction scenarios could have significant implications for global warming. The ‘business as
usual’ scenario, with recent trends continuing into the future, suggests a rise of 1.9-2.2oC by 2050 (50% confidence level).
However, if there is worldwide stabilization at 1990 emission rates, the warming is reduced to 1.4-1.6oC over the same period.
The adoption of more stringent regulations requiring the reduction of emissions to 50% of the 1990 level by 2050 is likely to lead
to a global warming of only 1.2-1.4oC. These results were obtained using the University of East Anglia’s Greenhouse Gas Policy
Model.
MAIN CONCLUSIONS
Hydrogen produced using non-fossil fuels can be used effectively both as a fuel and as an energy carrier without contributing
significantly to global warming. The two main methods of producing non- fossil fuel hydrogen (NFFH) are the gasification of
biomass and electrolytic production from water.
The take-up of NFFH technology will depend on a number of factors, including the continuing development of possible applications,
the availability of cheap hydrogen imports, advances in non-fossil energy sources, and initiatives to control C02 emission rates.
The modelling of four possible scenarios for future C02 emission rates indicates that only the scenario involving a significant
reduction in annual C02 emissions is likely to give rise to an uptake of hydrogen technologies. This also requires a high nuclear
build rate and the considerable deployment of renewable energy technologies. Furthermore, the model shows that none of the
technologies are likely to be adopted before 2025 and that no significant take- up is likely before 2035.
Projections suggest that the worldwide adoption of a ‘business as usual’ scenario, with recent emissions trends continuing into the
future, is likely to result in a global warming of 1. 9-2.2oC by 2050 (50% confidence level). This warming could be limited
to1.2-1.4oC if emissions are globally reduced to 50% of the 1990 level over the same period (the scenario resulting in an uptake
of hydrogen technologies).
|