Lupine Publishers | Open Access Journal of Environmental and Soil Sciences
Abstract
The wheels of technology are turned
by the conversion of energy from one form into another. Thus, energy is a key
element of sustainable development. Current trends in energy supply and use are
generally unsustainable, especially when the environment is affected by the
emitted green–house gases. These are expected to double by 2050, and increased
oil demand will heighten concerns over the security of supplies. Hence,
research on green favorites should continue vigorously. It is unfortunate that
these have their own limitations. In such a complex situation, consideration of
energy priorities in research and development should be organized carefully,
and drivers for future energy policy should be considered very critically. This
should give very careful foresight for the viable technologies, energy
efficiency, renewable energy, oil shale, nuclear energy, hydrogen energy, in
addition to any future innovations. Energy is of vital importance for the
processes of production and manufacturing. Thus, a key element of sustainable
development.
Keywords: Energy Status; Energy Conservation; Oil Shale; Renewable
Energy; Hydrogen; Fuel Cells; Energy Efficiency; Innovations
Abbreviations: CCS: Combined Cycle System; CO2 : Carbon
dioxide; GHG: Green House Gas; H2 : Hydrogen; HC: Hydrocarbon; HV:
Heating Value; HVAC: Heating Ventilation Air Conditioning; ICE: Internal
Combustion Engine; JUST: Jordan University of Science and Technology; MED:
Multiple Effect Distillation; NPPs: Nuclear Power Plants; PV: Photovoltaic; SHC:
Solid Heat Carrier; STPP: Solar Thermal Power Plant; TE: Thermoelectric; TEG:
Thermoelectric Generator; UF6: Uranium hexafluoride; UO2
: Uranium dioxide; US: United State
Introduction
With the increase in energy demand
and the expected shortage of the fossil fuel with time the need for sustainable
resources increases. Hence, this is initially handled by using clean fuels [1],
utilization of waste heat [2-6] and adopting different configurations [7,8],
where resources and environment are conserved. Energy is of vital importance
for the processes of production and manufacturing. Thus, a key element of
sustainable development. Energy is the convertible currency of technology. The
Wheels of technology are turned by the conversion of energy from one form into another.
Currently trends in energy supply and use are generally unsustainable.
Energy-related emissions of CO2 are predicted to more than double by
2050, and increased oil demand will heighten concerns over the security
supplies. Figure 1 shows the percentage of the (primary) worldwide energy use
provided by liquids, natural gas, coal, nuclear and renewables from 2005
through 2035. Renewables include solar and wind power, hydropower, geothermal
power, tidal and wave power and biomass.
Liquids, natural gas and coal are
collectively the “big three” fossil fuels that emit GHGs when converted to
energy. They constitute about 81% of the worldwide primary energy. The actual amounts
of energy used by source are shown in [9].
Figure 3 shows the importance in
assessing the GHG nature of a regional economy, it’s given by CO2 /
Energy Ratio (in metric tons of CO2 /GWh, GWh= 106 kWh) which Figure
4 shows the Global Market, Cumulative Installed capacity by Technology. There
are certain “Green” favorites, such as solar, wind and biomass with limitations
in capturing and storing, fluctuation, high cost, and being nonintensive. There
are many exciting variants on nuclear power which face significant risks of
cost overruns, limited investment, safety and health hazards. Petroleum and
natural gas are currently the main sources of energy. But the combustion of
these hydrocarbons contributes a large fraction of green-house gases and air
pollutant emissions. The search for an alternative fuel that provides as much
energy and is environmentally friendly has been a quest for quite sometimes
[10].
Energy
Status
Unfortunately, some countries import
almost all of its energy needs. In view of the increasing burden imposed by
energy imports, it is critical for them to look for indigenous sources of
energy. Switch to new, highly efficient and environmentally superior energy
technologies, is highly desirable. Relative contribution of energy sources in
the total energy mix over the period (2005-2020) is show in Table 1, for a
typical developing country. The typical distribution of final energy
(2000-2005) is shown in Table 2. Using energy has a direct impact on
environment due to:
a) Effluent gases [11].
b) Warming and climate change
Viable Technologies
Viable Technologies and Resources:
a) Combined cycles [12] and cogeneration (Figure 5) [13-21]
b) Energy conservation
c) Oil shale
d) Renewable energy
e) Nuclear power
f) Hydrogen and Fuel Cells
Energy Conservation
Fossil fuels are at present, and
will be for the following decades, the primary source of energy for satisfying
the region’s energy demands. However, CCS already faces many challenges that
are not only related to issues such as financing demonstration projects and
integration of adequate infrastructure, but also to efficiency [22- 24]. For
example, capturing and compressing CO2 would increase the fuel needs
of a coal-fired powered plant by 25-40 percent. Therefore, efforts should be
forwarded toward:
a)
Utilizing higher power plant conversion efficiency (combined cycle).
b)
Exploitation of low C/H content fuels, such as natural gas.
Oil Shale
The rise of oil prices in the global
market has increased the interest in production of oil from oil shale in
Estonia and other countries as well. The greatest problem of shale oil
production is the low thermal efficiency of the process [25]. Figure 6 shows
the theoretical (retorting in standard Fischer Assay) energy balance of thermal
decomposition of oil shale organic matter, as well as the real-life balance
compiled based on the long-term experience of shale oil production with the
solid heat carrier (SHC) method at the AS Narva Oil Plant Company [26]. Oil
shale is a kerogen-rich fine-grained sedimentary rock and its abundant reserves
are the second largest among all fossil fuels in the world if converted into
heat [27-30].
Oil Shale needs more detailed
studies that handle [31-33]:
a)
Realistic quantification.
b)
Appropriate Technology.
c)
Economics of conversion.
Jordan contains 40 billion tons of
oil Shale (30 years), Each ton oil shale contains 80-100 kg oil where Sulfur
content about 4%. The heating value= ¼ HV of HC fuel, Hence one ton oil shale
=0.025 ton of HC fuel but, it’s harmful to the environment(Open Pit
Mining),results in barren land and it has a high consuming of water: one barrel
oil needs one barrel water plus intensive energy consuming (In-situ
retorting):3 barrels of oil need one barrel of fuel [34,35].
Renewable Energy
Renewable energies are sources of
energy that are regenerated continually from nature and derived directly from
the sun (such as thermal, photo-chemical, and photo-electric), indirectly from
the sun (such as wind, hydropower, and photosynthetic energy stored in
biomass), or from other natural movements and mechanisms of the environment
(such as geothermal and tidal energy). Renewable energy does not include energy
resources derived from fossil fuels, waste products from fossil sources, or
waste products from inorganic sources [36]. Figure 7 shows an overview of
renewable energy sources [37,38].
While it is true that renewable
energy sources are environmentally friendly, or “green”, one has also to
consider their feedstock. Solar, wind, hydro, biomass and geothermal energies
are “free” at first glance, although they require huge land-use investments
with environmental unfriendly footprints especially biomass. However, active
research and development should continue until RE become competitive on all
grounds, to increase their share in the total energy profile due to their own
merits, not due to subsidies. Renewables account for 8% of the (world) and US
national energy product as Figures 8 & 9. Most of this market is not due to
symbolic renewables of wind and solar that dominates global discussion [39]. It
is from biomass and hydroelectricity. It is also obvious that electricity from
renewable energies has considerable problems in the way they are deployed
today. First of all, and foremost, they are dependent on certain conditions
(availability of wind, water and sunshine). Due to their intermittent nature,
this deployment method is overstraining the grid, which is additionally rather
inefficient in itself e.g. Germany. This not only requires improving the grid,
but also making it “smart”.
Renewable
Energy (RE) - Wind
At the end of 2008, the worldwide
capacity of wind-powered generators added up to 121 GW, a mere of 1.5 percent
of the world’s electricity usage. But the rapid growth continues, with China
doubling its wind power capacity for the fifth consecutive year since 2004
[40]. The strongest growth will be biomass and wind towards (2035). The solar
remains the perennial dark horse with tremendous but unproven potential.
Intermittency of wind turns out to be a big problem for the grid-operating
utilities, because electricity must be used as soon as it is produced. But how
easily can be forecast when and where the wind will blow? You can’t simply
start a wind mill up when you need it most. Thus, at least as the electricity
grids are operated today, the intermittency of wind always requires backup
systems (batteries) with an equal amount of dispatchable generation capacity.
Unfortunately, at the moment these back-up systems are mostly conventional
power plants that do not have short run-up times. In addition to the
unpredictability of wind, wind farms usually need high investments to be built,
and are also very expensive to properly maintain. At least 20 percent of the
windmills are shut off for maintenance or repairs. What is even worse, they are
often taken off the grid, because their electricity is not needed at that given
moment [41,42]. There are no commercially viable ways to store wind energy at
this time, other than pumping up water electrically in water reservoirs. But
this only makes sense when wind farm and water reservoir are close to each
other. Moreover, wind has noise emission, effect on animal species and birds.
There are objections by the military: disturbing microwave lengths, radar and
low-flying aircrafts [43-45].
Renewable
Energy- Solar
The amount of energy that comes from
the sun is phenomenal: If we could somehow gather all the energy that reaches
the earth on one day and store it, it would supply the energy needs of the
whole world for almost 30 years. Moreover, solar radiation is actually the sole
source for fossil or renewable energy that we use today. Electricity from
sunlight can be generated directly using photovoltaic solar cells, or
indirectly as with concentrating solar power [46-48]. Consider another
interesting aspect: PV solar cells convert the sun’s radiation into DC power on
which most of our appliances actually run [49]. But this power is converted
into AC power by inverters and fed into the inefficient grid, only to be
inverted again to DC [50]. At this point, the most cost-effective and efficient
technology for converting solar power into electricity are huge solar-thermal
power plants (Figures 10 & 11). Here, sunlight is gathered by a large solar-collecting
field with parabolic mirrors, so called troughs. These collectors track the sun
over the course of the day and concentrate the sunlight onto absorber pipes
where the radiation is converted into heat. A heat transfer fluid which is
circulating through the pipes is heated up to temperatures of almost 400⁰C
[51,52]. The heat is used to generate vapor or steam with which electricity is
then produced by conventional turbines. The process fluid or water is then
cooled and returned to the cycle. The surplus heat could be used for heating,
desalination, cooling, air conditioning, and other applications, but in most
cases, it is currently rejected to the atmosphere. Solar-thermal power plants
have been in commercial use for several decades since (1982). Thermal molten
salt storage enables electricity production even during the night, or on cloudy
days. The storage time, however, is estimated to be seven hours.
Water is mainly used for cooling the
steam circuit, i.e. from the vaporization of water in the cooling towers (about
1 million tons water/y for 150 MW plant, 400 sq km). So, the plant operators
not only have to capture the power of the sun, but also need immense amounts of
water for cooling the heat transfer media. As most solar power plants today is
located in deserts, this physical necessity may be an obstacle to development
on the long run [53,54].
Nuclear
Energy
There is now a plenty of uranium,
that present reactors can supply energy for some hundreds of years, where
fossil fuels are expected to run out in a few decades. So nuclear energy may be
considered semi-sustainable.
Using nuclear energy is assumed to
limit the pollution with greenhouse gases in an efficient and cheap way. It is
the only alternative to provide clean energy on a massive scale. However,
nuclear energy has the problem of accidents and there is still no proper
solution to store nuclear waste in a safe way [55]. Some consider nuclear power
plants to be a “clean” electricity source, since the plants themselves do not
directly emit CO2 and other GHGs. Nevertheless, the operation of
nuclear power plants results in the immense environmental impacts which are
displayed in Figure 12. After a cost intensive exploration process, uranium ore
is recovered from the earth’s crust under quite difficult conditions. It must
be extracted from the mined ore using strong acids and bases, and then be
converted into either uranium dioxide (UO2 ) for heavy water
reactors or gaseous uranium hexafluoride (UF6 ) for light water
reactors [56].<.
Most reactors require uranium fuel to have a U-235 (an
isotope of uranium) content of 3 to 5 percent. For this step, large amounts of
electricity, mostly provided by fossil fuel plants, are needed to increase the
actual concentration of 0.7 percent to 3 to 5 percent. Afterwards, the uranium
is manufactured into fuel pellets by pressing powdered UO2 or UF6
into cylindrical shapes and baking them at high temperatures, usually between
1,600 and 1,700⁰C. Finally, energy is released in a reactor by controlled
nuclear fission reactions just to boil water, produce steam and drive a turbine
that generates electricity. This process alone has an efficiency of only 35
percent. For steam production and for cooling, approximately 2.5 times more
water is needed for nuclear than is required for fossil fuel plants. This is
the reason why nuclear power plants are located at rivers or lakes. In 2008,
KIKK German committee reported a 60% increase in solid cancer incidence and a
120% increase in Leukemia incidence among children living within 5 km of all
German nuclear power stations [57]. In essence, this suggests that doses to embryos/fetuses
in pregnant women from environmental emissions from nuclear power plants (NPPs)
may be larger than suspected. It is now officially accepted in Germany that
children living near nuclear power plants develop cancer and leukemia more
frequently than those living further away [58].
After the nuclear fuel is consumed
in the reaction process, it is removed from the reactor and stored on site in
large water-filled pools for about five years. Later, the radioactive waste is
transferred to underground caverns for medium-term storage. At present, there
are no safe disposal facilities in operation anywhere in the world which can
accept radioactive waste for permanent storage [59]. In a radioactive waste
disposal facility since the seventies, the storage has recently been found to
be unstable. According to World Nuclear News, roughly 126,000 barrels filled
with lowlevel radioactive waste including contaminated clothes, paper and
equipment need to be brought to the surface for alternative storage [60,61]. A
challenge involves approximately Euro 3.7 billion and a rather gracious
heritage for future generation(s). We always need to keep in mind that already
a minor failure in a nuclear power plant can create severe consequences for all
forms of life on earth. Accordingly, decision makers should answer the
question: How much “clean” a process like this that poses health risks
exceeding that of any other process of electricity generation?
Hydrogen
and Fuel Cells
The key criteria for an ideal
alternative fuel are inexhaustibility, cleanliness, convenience, and
independence from foreign control. H2 is considered as one of the
most promising fuels for generalized use in the future. Mainly because it is
versatile, energy-efficient, low-polluting, and a renewable fuel. Hydrogen is
environmentally favorable replacement for gasoline, heating oil, natural gas,
and other fuels in both transportation and industrial applications [62-65]. In
nature, mostly the hydrogen is bound to either oxygen or carbon atoms. Hence,
to obtain hydrogen from natural compounds, energy expenditure is needed
[66-71]. Therefore, hydrogen is considered as an energy carrier a means to
store and transmit energy derived from a primary energy source. Presently
hydrogen is mainly used in production of gasoline, fertilizers and metals.
However, hydrogen requires energy to produce, store and distribute. Hence,
hydrogen technologies need to be developed to reach the stage of competing with
fossil fuels and other alternatives to produce power [72-75]. These technologies
should emphasize efficient systems to reduce energy losses, and emissions.
Among high efficiency technologies, fuel cells appear to be the most promising
with high efficiency and very low environmental impact. Fuel cells are able to
convert the fuel chemical energy into electricity, heat and water by reverse
electrolysis. This leads to much higher conversion efficiency [76].
Fuel cells can convert the fuel
chemical energy into electricity, heat and water by reverse electrolysis,
Figure 13. This leads to much higher conversion efficiency. Both considerable
primary energies saving and pollutant reduction, are achieved by upgrading
conventional systems to fuel cell hybrid plants, Figure 13. Oil is essential in
the transport sector while natural gas will become a more dominant fuel in
power generation. Hydrogen economy is expected to offer considerable
opportunities. Fuel cell development is an important step to the efficient use
of hydrogen hence, research must continue in this area, Figure 14. The preferable
solution is to produce H2 from sustainable sources such as, wind
energy, solar energy, waterpower or biomass. However, these energies will not
be able to provide a massive contribution to meeting the energy demand for many
decades to come: Environmental reasons (large scale tolerance of wind energy),
practical reasons (availability of surfaces), economic reasons (cost of
photovoltaic energy) and technological reasons (storage of intermittent
energies) [77]. Hence, the fuel cell is seen to be the most efficient energy
converter in the near future, using H2 . However, it still has major
problems, such as: Reducing the cost of fuel cells by a factor of 90%;
enhancing the performance and durability of fuel cell systems by a factor of 2,
and reducing the H2 production and distribution costs by a factor of
3 productions from water is not efficient [78].
Energy Efficiency
Energy efficiency is a convenient
technology to be adopted by the developing countries. Energy conservation
implies reductions in the consumption of energy, such as (turning thermostats
down) [79]. Consuming less energy results in protection of the environment and
preventing climate change through forcing people to make sacrifices in comfort,
pleasure and convenience. Efficiency implies obtaining more useful heat, or
work from each unit of energy supplied, either by technological improvements or
reducing waste. Consuming less energy results in protection of the environment
and preventing climate change through forcing people to make sacrifices in
comfort, pleasure and convenience [80]. Hence, Energy efficiency could be
described in three ways: Less energy for the same benefit (conservation), the
same energy for a greater benefit and more energy for an even greater benefit.
Only the first description of energy efficiency is sustainable. The second does
not lower gross energy use, and the third increases it [81]. If promoting
energy efficiency, enhances the benefits of the end users, and does not reduce
the impact of energy and environmental costs, this is not sustainable. Improved
energy efficiency must lead to measurably less gross energy use (reduced use of
fossil fuels) and polluting emissions. Improved “energy efficiency technology
“involves much more efficient: motors, air conditioners, furnaces, direct and
indirect water heaters and computers [82,83].
Variable speed drives and variable
volume HVAC with direct digital control, energy management systems with optimal
start, cogeneration and air-to-air heat pumps, reduce use of electricity and fuel
in commercial buildings [84]. For transportation, to have lighter aluminum
blocks, fuel injection, turbo charging, overhead cams, automatic speed
controls, and using unleaded fuel with catalytic converters to reduce
emissions. The bodies and frames of the cars need to become lighter, smaller
and more unified. They are made lighter with plastics and fiberglass shaped
into aerodynamic forms. Moreover, steel belted radial tires, front wheel drive,
disk brakes with anti-lock features, light emitting diodes, all yields a better
efficiency [85]. Interstate highway systems, speed limits legalized, carpooling,
and most recently, the internet, email, and telecommuting reduced gasoline
consumption and improved energy efficiency. In Power industry: combined cycles,
cogeneration systems, trigeneration: of power, heating and cooling enhance
energy efficiency. One-third of the oil used in most countries is used in
transportation, by passenger cars and light trucks. The overall fuel efficiency
of vehicles could be increased by improvements primarily in aerodynamics,
materials, and electronic control [86].
The most fuel-efficient cars are
compact with small engines, manual transmission, low frontal area, front wheel
drive and reduced vehicle weight. Radial tires usually reduce the fuel
consumption by 5 to 10 percent by reducing the rolling resistance.
i.
Before driving:
a)
Using fuel with the recommended minimum octane number; not overfilling the gas
tank.
b)
Parking in the garage.
c)
Starting the car properly and avoid extended idling.
d)
Not carrying unnecessary weight in the vehicle.
e)
Keeping tires inflated and the wheels aligned.
ii. While driving:
Avoiding quick starts and sudden
stops:
a)
Driving at moderate speeds.
b)
Maintaining a constant speed; avoiding sudden acceleration and sudden braking;
avoiding resting feet on the clutch or brake pedal while driving.
Using highest gear (overdrive)
during highway driving; turning the engine off rather than letting it idle; and
using the air conditioner sparingly. Regular maintenance improves performance,
increases gas mileage, lowers repair costs, extends engine life and reduces air
polluting [87].
Innovations in Energy Systems
The automobile industry and the
associate industries that serve as the base of the world’s economy and employ
the greatest share of the working population. They have played a significant
role in the growth of modern society by satisfying the need for mobility in
everyday life [88]. Presently, all vehicles rely on the combustion of
hydrocarbon (HC) fuels to derive the energy necessary for their propulsion.
Recent European green car initiatives are concentrating on advanced internal
combustion engine (ICE) research with emphasis on:
a)
new combustion techniques such as stratification with direct injection in
gasoline engines,
b)
using alternative fuels (bio-methane, ethanol, hydrogen etc.),
c)
intelligent control systems,
d)
mild hybridization and
e)
special tires for low rolling resistance [89].
A smart Controller for improving
fuel economy in vehicles was adapted with fuel saving ~ 11% ) (Figure 15).
Considering recent fuel prices, a country of (6M people)can save: 60.0 M JD/y.
The Environment is saved proportionally, from CO2 , Figure 3.
1.3 billion People – about 20% of
the worldwide population – are still without access to electricity, almost all
of whom live in developing countries [90]. Providing a minimum amount of
electricity can actuate the basic needs such as light, radio and some medical
electronic devices. Thus, making a lot of difference in their lives. TEG
coupled to the stove can be a very interesting option to provide such amount of
electricity. TEG is a device that harvests waste energy and converts some of it
to useful power. It operates on a fundamental principle termed the See beck
effect which states: when a temperature gradient is established between two
different metals or semiconductors, a corresponding voltage gradient is
induced. This causes a continuous current to flow through a complete circuit.
The major advantage of a TE generator in this case is requiring almost no
maintenance, since there are no moving parts. Only the battery needs to be
charged when needed. The TE generator works day and night in clear or rainy
weather unlike solar panels. Moreover, the battery does not need to be
oversized. On the other hand, there are some challenges involved in using the
thermoelectric generators. Mainly the low efficiency of the technology itself
is below about 10% [91] and the high price of the TEG models. The low
efficiency problem may be solved by new technologies evolved over time. The
price will decrease with more adoption of such systems. Figure 16 shows a
typical TE stoves which offers multitasks simultaneously such as: Space
heating, cooking, heating water and generating electricity for basic needs.
Moreover, generation of water is planned in the near future [92].
Conclusion
Viable
Technologies
Combined cycles, cogeneration,
natural gas, fuel cells and energy efficiency: Contribute toward
sustainability.
Power
Generation:
Presently, concentration should be
made on energy efficiency technologies. In the future, on fuel cells.
Oil
Shale Needs
a)
Realistic quantification
b)
Appropriate technology
c)
Economics of conversion: (requires huge amounts of fuel and water)
d)
Genuine assessment of environmental impacts Renewable Energy
Green Favorites, although clean they
have limitations in capturing and storing, fluctuation, high installation cost,
and are non-intensive when converted. Active present and future research should
proceed continuously, supported by all means possible, until RE become really
competitive on all grounds, to share a progressively higher portion of the
energy pie, with gradual replacement of fossil fuels.
Nuclear
Energy
a)
The nuclear energy has the problems of health hazards (during operation),
storing waste, escalating initial cost, and accidents.
b)
The risks of nuclear energy are too high for ourselves and the many generations
to come.
c)
Hence, the nuclear energy should not be an easy way for some policy makers to
ensure enough energy in the future.
Hydrogen
and Fuel Cells
More research and development should
be concentrated on hydrogen. Mainly because it is versatile, energy-efficient,
lowpolluting, and a renewable fuel.
a)
A hydrogen car is safer than NG or gasoline car in collisions in open spaces.
b)
But as safe as NG car and safer than gasoline or propane car in a tunnel
collision.
c)
However, H2 economy needs more efforts to reduce the cost of: FC, H2
production and distribution; plus, durability enhancement.
Energy
Efficiency,
a)
Energy efficiency is a convenient technology to be adopted by the developing
countries.
b)
Consuming less energy results in protection of the environment and preventing
climate change.
c)
Efficiency implies obtaining more useful heat, or work from each unit of energy
supplied, either by technological improvements or reducing waste.
Innovations
in Energy Systems
Innovations in energy systems should
continue and more devices developed to enhance energy efficiency and
sustainability
Acknowledgment
The author would like to thank
Engineers Duaa MH Kharouf and Ahmad Abu-baker for the valuable help.
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