Concentrating solar thermal power stations convert as little as 25 to 30 percent of collected solar energy into electrical energy and need large thermal energy storage systems that add to the cost of construction.
Existing technology allows solar thermal energy to be converted into electrical energy with an effective efficiency of 90 percent and eliminates the need for thermal energy storage systems.
What the diagram represents is that 1 kilogram (2.2 lbs) of brown coal is decomposed into carbon monoxide and hydrogen by absorbing 5.54 megajoules of heat energy.
The resulting carbon monoxide and hydrogen then releases 14.14 megajoules of heat energy when it combines with oxygen to produce carbon dioxide and water vapour.
The net heat energy available from burning this kilogram of brown coal is the difference between these two energy flows: 14.14 - 5.54 = 8.60 megajoules of heat energy.
Burning a kilogram of brown coal in a coal-fired power station allows a proportion of this 8.60 megajoules of heat energy to be converted to electricity. Typically only about 40 percent is delivered as electricity: around 0.96 kilowatt-hours.
A different way of converting brown coal to electricity enables a far greater amount of electricity to be produced from each kilogram:
First each kilogram of brown coal is decomposed into carbon monoxide and hydrogen by absorbing 5.54 megajoules of concentrated solar thermal energy.
Second, the resulting carbon monoxide and hydrogen releases 14.14 megajoules of
heat energy when it combines with oxygen to produce carbon dioxide and
water vapour in a gas power plant. Typically about 60 percent is delivered as electricity: around 2.36 kilowatt-hours.
The coal needed to produce 0.96 kilowatt-hours of electricity is reduced from 1 kilogram (2.2 lbs) to just 405 grams (14.3 ozs).
Concentrated solar thermal power stations using steam turbines or compressed air turbines are less efficient than they could be.
This video describes the difference between steam turbine power plants and gas turbine power plants. Concentrated solar thermal power plants use the same technology without using fossil fuels as the source of thermal energy.
Steam power plants and compressed air turbines can only convert about 35% of the energy collected into electricity:
On the back end of the steam turbine the steam must be condensed back into
water.
During this condensation process, heat is “rejected” up cooling towers and
into the atmosphere, resulting in a loss of 30% to 40% of the original heat energy supplied to the system. More energy is then used in pumping the condensed water back into the boiler at very high pressure.
Compressed air turbines discard a large amount of energy collected in the exhaust flow out of turbine. More energy is used by the axial flow compressor that compresses air on input to the turbine.
"Solutions" focus on methods to make use of the heat energy wasted by these engines. One often-used approach is to build an entire steam power station behind a compressed air turbine generator! This "solution" is known as a combined-cycle gas turbine or "CCGT" power plant.
For reasons that are not clear solutions that simply avoid the waste of thermal energy in the first place are overlooked.
Adding a high-efficiency compressor to the front of a conventional axial-flow air compressor and turbine generator allows the exhaust to cool to ambient temperature with no heat energy wasted.
Compression Basics
The Hicor technology achieves a more efficient compression process by minimizing the temperature rise associated with compression, improving efficiencies over conventional compressors by 30% or more.
At its most basic, compression is a mechanism by which work is
put into a fluid and results in an increase in pressure. Heat is also
generated as a by-product of compression, which serves to make the
process less efficient by turning some of the input work into heat
instead of pressure. As the gas being compressed heats up further and
further, the compression process gets less and less efficient.
Hicor’s technology achieves a more efficient compression process by minimizing
the temperature rise associated with compression, improving efficiencies
over conventional compressors by 30% or more.
Hicor’s proprietary compression technology provides a myriad of
additional benefits as well, including fewer moving parts, less
vibration and noise, and a variable pressure ratio. Finally, Hicor’s near-isothermal compression
technology allows for compression ratios of 30 to 1 or higher, reducing
system level complexity and resulting in lower capital and operating
costs.
Positive Displacement Compression
The compression process can be displayed graphically, as in
the pressure-volume (PV) plot shown below. The curves in a PV plot show
how the pressure increases as volume decreases. For different
compression processes, the curves will vary. The work of compression can
be visualized as the area under the curve corresponding to a given
compression curve.
All compression processes fall between two extremes: adiabatic,
where no heat is exchanged with the outside environment and the energy
put into the system remains internal; and isothermal, where energy is
removed from the system in the form of heat and the temperature of the
gas remains constant.
In practice, all compression processes fall
somewhere between adiabatic and isothermal and are known as polytropic
processes. To achieve a more highly efficient compression process, it is
ideal to reduce the polytropic constant to as close to the isothermal
process as possible, where the polytropic constant is 1.
The Hicor proprietary compressor design is capable of achieving
polytropic constants as low as 1.06, improving efficiencies over
conventional, near-adiabatic compressors by as much as forty percent.
"The renowned scientist Dr. Samar
Mubarakmand who is head of the Thar Coal Gasification Project ... was participating and Chairing the Clean Coal conference held here on October 23 and 24 to mark the World Clean Coal Week."
“The Future of Asia: Be Innovative” - Speech by Prime Minister Shinzo
Abe at the Banquet of the 21st International Conference on the Future
of Asia
Thursday, May 21, 2015
"...efficiency jumps remarkably through the use of the latest technologies
for the combustion of gasified coal. ...
By utilizing gasification technology, brown coal,
which until now has been regarded as unfit for coal-fired thermal power,
will become a promising resource.
...
By introducing Japanese gasification technology to Mongolia, your vast
resources of brown coal dormant in the ground of Mongolia will become a
treasure trove."
Special Feature. Dawn of a New Era for Coal. Clean Production of Energy Using IGCC (Integrated Coal Gasification Combined Cycle)
"Integrated coal Gasification Combined Cycle (IGCC) is a coal-based power
generation technology that achieves the twin objectives of reduced CO2
emissions and increased efficiency by "gasifying" the coal and then
using a gas turbine and a steam turbine in a two-stage generation
process.
MHI has been researching and developing this technology since
the 1980s. It has accumulated numerous proprietary technologies and
demonstrated their reliability primarily with test operations at an
enormous IGCC demonstration plant. The demonstration plant quite
successfully finished the test operations, satisfying all targets set.
With its capabilities highly evaluated through the series of test
operations, the decision was made to convert it to a commercial plant
owned by a utility company and to commence commercial operations in June
2013. This marks the long-awaited practical application of a pioneering
technology that will open a new era for the effective use of coal.
...
MHI has committed every possible technology towards the pursuit of the
IGCC plant's efficiency. As well as combining gas and steam turbines
with a highly efficient energy-converting gasifier, MHI also makes use
of the discharged heat to avoid waste.
This mechanism delivers 10-15 percent better thermal efficiency
than a state-of-the-art coal-fired conventional thermal power plant
(ultra-supercritical coal-fired thermal power plant: USC). Because it
can provide the same amount of power as a USC but using less fuel, it
also cuts CO2 emissions by about 10-15 percent. This puts it on a par with oil-fired thermal power plants in terms of emissions.
...
The IGCC plant is a complex system that combines a gasifier, a gas turbine, a steam turbine and other interconnected equipment.
It is a testimony to MHI's advanced design and engineering
skills that the plant succeeds in harnessing them together into an
efficient and reliable working unit. Within just a year of its start,
the Nakoso demonstration plant had racked up 2,238 hours of continuous
operation.
This unparalleled achievement owes its speedy progress to the smooth interaction of the plant's various equipment.
IGCC is expected to spawn new technologies in the future. There
is a real prospect of a MHI power plant achieving thermal efficiency of
over 65 percent when it launches the J-Series gas turbine"
