Yorke Biomass Energy - straw fuel could be used in place of thermal storage, reducing the capital expenditure of the concentrated solar thermal power station.
Another option for synergy of these two projects is perhaps less obvious but potentially far better. Concentrated solar thermal energy can be used to turn the straw into synthesis gas. This saves about 30 percent of the energy in the straw that is 'wasted' if the straw is burned without first being converted to gas.
We
report on the thermochemical conversion of inedible crop residues using
concentrated solar energy as the source of high-temperature process
heat. ... The
waste biomass feedstock consisted of unprocessed batches of cotton boll,
soybean husk, and black mustard husk and straw, which were pyrolysed
and steam-based gasified at nominal temperatures in the range 879–1266 °C, yielding high-quality syngas ... The heating
value of the feedstock was solar-upgraded by 7%, thus outperforming
autothermal gasification that typically downgrades by at least 15%.
The
ash contained 23% potassium.
The solar-driven thermochemical process
offers a sustainable and efficient path for the conversion of
agricultural wastes into valuable fuels and soil fertilizers.
The synthesis gas produced:
Avoids the cost of the thermal energy storage needed by the concentrated solar thermal power station. This is because the solar thermal energy is stored in the form of synthesis gas.
Allows the energy in both the straw and the concentrated solar thermal energy to be used for a gas-fueled internal combustion engine or combined cycle gas turbine electricty generation. This raises the conversion efficiency to 60 percent - far above the efficiency that either power plant can achieve now (assuming they both plan to use steam turbine generators at efficiencies between 20 percent and 40 percent.)
The cost of storing energy and meeting peak demand can be cut dramatically with a good combination of technologies and judicious use of available assets.
Depleted gas fields in South Australia have provided a return on investment over a number of years and when reused for new purposes, save the need for investment in locating and tapping similar geological structures.
Subsurface geological conditions which may be suitable for underground gas storage have been identified in the Two Wells - Port Wakefield area of the Northern Adelaide Plains. This area is within 100km of Adelaide. (See "Underground Gas Storage", Department of the Premier and Cabinet, South Australia)
A cutaway view of Solar Turbines' Taurus 70 engine,
which is similar to a jet engine, but is used to generate electricity in power plants on the ground.
In a solar thermal turbine compressed air is heated by concentrated solar energy...
CSIRO Solar Air Turbine Project
Heat energy in a solar thermal turbine can be supplemented with natural gas when there is partial cloud cover. At night natural gas can take over from solar thermal heating.
Whether a turbine engine is run on natural gas or solar thermal energy, about half the energy available from the turbine is used to power the compressor, leaving the other half to run a generator to supply electricity.
That is, a gas turbine power station with a nameplate rating of 100 MW is actually able to produce 200 MW of energy - if it did not have to drive a compressor.
Energy from renewable energy generators may be stored by driving compressors to compress air that is stored in depleted gas fields.
The compressed air energy storage can deliver electricity to the grid when it is required by supplying it to a gas turbine generator, relieving the generator of the need to drive a compressor while it is being supplied with compressed air.
A solar thermal power station can store energy in a compressed-air energy store and use the compressed air at night to significantly reduce the amount of stored thermal energy or natural gas needed for operation.
During peak demand periods, output from existing gas turbine generation plant can be quickly increased by reducing the energy used to drive compressors while supplying them with compressed air from storage.
There are 4 or 5 processes that do more-or-less the same thing in slightly different ways. Each was designed with a different purpose in mind, but that doesn't mean they can't be used for other purposes the designers hadn't considered.
Bioenergy, waste-to-energy, renewable energy storage as synthetic natural gas, biogas and synthetic natural gas from coal are different ways of doing the same thing.
Synthetic natural gas can be used to store energy, to generate electricity on demand, and as feedstock in manufacturing processes. Synthetic natural gas can also be manufactured for export in the form of LNG.
It can be made from 100 percent renewable energy, 100 percent fossil fuel energy, or some combination of both renewable and fossil energy. This allows a transition to a 100 percent renewable energy future, achieving the above requirement statement: ensuring reliable, affordable and clean energy.
The underlying process combines carbon dioxide, water and energy to create methane and oxygen:
CO2 + 2H2O → CH4 + 2O2
Photosynthesis by plants and algae to create biomass that methanogenic bacteria convert to methane is one way of doing this with solar energy.
Waste-to-energy can use methanogenic bacteria to produce methane using the solar energy embedded in the waste.
Electrolysis of water to produce hydrogen that is reacted with carbon dioxide to make methane is another way of doing this with solar PV systems and wind turbines.
Biomass can be converted to methane in high temperature superheated water reactors. The thermal energy to do this can be from concentrated solar thermal energy, or from reaction with either oxygen or hydrogen created by electrolysis of water.
Biomass can be converted to methane in very high temperature gasifiers that create carbon monoxide and hydrogen that is reacted in a separate step to create methane. The energy for this high temperature process can be obtained by burning a portion of the feedstock in air.
In each of the above processes that use biomass to produce methane, coal can be used in place of some or all of biomass.
When there is sufficient solar PV and wind turbine generating capacity, hydrogen can be produced whenever electricity supply exceeds demand. This hydrogen can be reacted with carbon dioxide to make methane for generating electricity whenever demand exceeds the supply.
With sufficient renewable energy generating capacity, synthetic natural gas can be manufactured for export - providing completely renewable energy to importing countries via existing LNG export, transport and import infrastructure.
Curiously, coal is presently being converted to synthetic natural gas in the most environmentally 'unfriendly' option available - burning a portion of the coal in air to create carbon monoxide and hydrogen that is reacted in a separate step to create methane. This technology has been criticised for its high level of carbon dioxide emissions and water usage.
Coal could be converted to methane by reacting it with hydrogen produced by electrolysis of water with electricity from solar PV systems and wind turbines. It can also be converted to methane in high temperature superheated water reactors. The thermal
energy to do this can be from concentrated solar thermal energy, or from
reaction with hydrogen created by the electrolysis of
water.
This is most suitable for low-grade lignite such as that found in Yallourn Valley in Australia that consists of 50 percent or more water. With this process it can be converted to high-value synthetic natural gas, avoiding the need for coal seam gas.
Its use can be gradually phased-out as renewable energy generating capacity increases to the stage where it can completely replace it.
Michael Dolan & Daniel Roberts, University of Adelaide, February 7, 2013
Highly endothermic gasification and reforming processes offer a significant opportunity for the penetration of Concentrated Solar Power into the chemical and fossil energy industries. The upgraded products incorporate solar energy in chemical form which enables the ready storage, distribution and use of concentrated solar thermal energy.
Yallourn
The Yallourn Power Station produces about 22 percent of the electricity used in Victoria. Every hour 2,400 tonnes of brown coal are needed to produce super-heated steam for 4 turbines. These turbines have a combined capacity of 1,480 megawatts of electricity. In 2015 annual generated electricity output was 10,256 GWh, up from 9,806 GWh the year before.
In 2015 Yallourn Power Station installed a new High Pressure- Intermediate Pressure (HIP) turbine in Unit 2. This resulted in an efficiency improvement for Unit 2 of around 2.7%. This marked the completion of a 5 year program of new HIPs on all four Yallourn Units.
Hazelwood
The Hazelwood Power Station produces up to 25 percent of the electricity used in Victoria. Up to 15.3 million tonnes of brown coal are needed each year for an annual generated electricity output of approximately 12,000 GWh. Steam from 8 water tube boilers drives 4 turbine stages. These turbine stages have a combined
capacity of 1,542 megawatts of electricity, just 62 megawatts more than the Yallourn Power Station.
Since 1996 more than $1 billion has been invested at Hazelwood to improve efficiency and reliability.
Lignite or brown coal from the Hazelwood mine is about 62 percent moisture at extraction.
Efficiency and CO2 Intensity
The brown coal used as fuel supplies about 9 gigajoules of thermal energy per tonne. The coal-fired power stations convert about 24 percent of this energy into electricity. The other 76 percent is output as waste heat.
Each tonne of brown coal contains about 250 kilograms of carbon and the balance, 750 kilograms, is mostly hydrogen and oxygen.
When burned the hydrogen and oxygen is converted to water vapour, while the 250 kilograms of carbon combines with oxyygen from the air to form 920 kilograms of carbon dioxide.
To generate 1 megawatt-hour of electricity at 24 percent efficiency, 1.667 tonnes of coal must be burned. This contains 417 kilograms of carbon that is converted to 1,528 kilograms of carbon dioxide when burned.
Solar Thermal Fuel in a Converted Coal Power Station
Brown coal can be converted into a mixture of gases using concentrated solar thermal energy.
One such process could convert each tonne of brown coal into 920 kilograms of carbon dioxide and 80 kilograms of hydrogen.
Solar thermal gasification of brown coal
The 80 kilograms of hydrogen gas from each tonne of coal supplies 9.67 gigajoules of thermal energy when burned.
This hydrogen fuel could be burned in one or more gas turbines added to an existing coal fired power station.
The hot exhaust gas from these gas turbines would be used to create superheated steam in the coal fired power station's existing boilers and drive some or all of its existing steam turbines.
The addition of the gas turbines fueled by hydrogen can raise the efficiency of the power station from just 24 percent to 60 percent.
The thermal energy available from the 80 kilograms of hydrogen fuel consists of the 9 gigajoules present in each tonne of pulverised coal together with 0.67 gigajoules of solar thermal energy.
At 60 percent efficiency this 9.67 gigajoules of thermal energy is converted into 5.8 gigajoules of electricity.
To generate 1 megawatt-hour of electricity at 60 percent efficiency, only 0.62 tonnes of coal must be converted to hydrogen that is burned.
This amount of brown coal contains 155 kilograms of
carbon that is converted to 570 kilograms of carbon dioxide when it is gasified using concentrated solar thermal energy.
The hydrogen, 50 kilograms, from the 0.62 tonnes of brown coal is all that is required to generate 1 megawatt-hour of electricity.
There is a saving in mining operations because much less coal needs to be processed for each megawatt-hour of electricity generated: a reduction from 1.667 tonnes to just 0.62 tonnes of coal.
Available technology boosts efficiency of thermal power plants to 60 per cent
Designers of solar thermal power stations may not realise that a few minor changes are all it takes to:
Reduce the cost of solar thermal power and
Provide reliable 24 hour, 7 days a week operations.
A substantial capital cost is the heliostat field that focuses solar energy on the tower where elecricity is generated. Two design options are available to lower this significant cost component.
Improve the efficiency of power generation in the solar tower, and
Simplify the two-axis tracking technology that repositions each heliostat as the sun moves across the sky.
Another substantial cost is the choice of components to provide power generation during cloudy periods and at night. The simplest design option is also by far the lowest cost solution:
Use an alternate energy source to maintain energy production at all times.
Improving efficiency
The size and cost of the heliostat field is directly related to the efficiency of power generation.
A 10 megawatt power station that achieves only 25 percent thermal efficiency requires a heliostat field able to focus 40 megawatts of solar thermal energy on its receiving tower.
The same power station with generating technology that achieves 50 percent thermal efficiency requires a heliostat field able to focus just 20 megawatts of solar thermal energy on its receiving tower.
The cost of the heliostat field is cut in half by this increase in efficiency.
Simplify the two-axis tracking technology
The cost of actuators to reposition heliostats is another significant component in the power station cost. Usually two actuators are needed for each heliostat.
Every heliostat in each row of heliostats needs to rotate by the same angle and at the same rate each day as the sun tracks from east to west. Just one actuator connected via a fixed beam is all that is required to provide the east-west movement of each row of heliostats. Another actuator on each heliostat is still required to provide tracking for the vertical movement each day.
Improve the efficiency of power generation
Concentrated solar thermal power stations typically use steam turbines for power generation. These are able to achieve thermal efficiencies around 25 - 35 percent at best.
A far more efficient technology is combined-cycle generation using a solar-air turbine in the first cycle with a steam turbine in the second cycle.
A conventional internally heated combined-cycle gas turbine power station achieves around 60 percent thermal efficiency. Using an externally heated solar-air turbine turbine reduces the efficiency to around 50 percent.
Use an alternate energy source until energy storage is much cheaper
Concentrated solar thermal energy varies steadily through the course of each day and can fluctuate in very short intervals if clouds cast moving shadows over the heliostats.
A simple and effective solution is to incorporate a temperature sensor on the output from the solar-air turbine to control a gas burner fitted to the turbine.
Optimising the price-performance ratio of concentrated solar thermal power stations is an interesting mathematics puzzle.
Fossil fuel power stations have traditionally been designed without the benefit of advanced compressor technology that achieves close to isothermal compression. Without this technology all designs necessarily aim to maximise the temperature at which fossil fuels are burned.
Optimising the price-performance of concentrated solar thermal power stations has two significant differences:
New compressor technology allows optimisation without the need for extremely high temperatures and substantial waste heat being discharged as a result.
Solar thermal energy able to be used in a solar thermal tower reduces as the temperature increases. At the maximum attainable temperature known as the "stall temperature" energy arriving in the collector is being re-radiated into space at the same rate as it arrives. No energy is available to be converted to electricity.
As a result of the last point above, an increase in efficiency that relies on a higher temperature will eventually result in less electricity being produced because less solar energy is being converted - even though the efficiency of conversion is greater. For instance 50 percent of 100 kilojoules is more than 75 percent of 60 kilojoules in the situation where 40 kilojoules are lost due to a higher temperature in the solar receiver.
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.
Hicor’s technology achieves a more efficient compression process by minimizing the temperature rise
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.
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.
Here's a challenge in financial optimisation while combining available technologies:
Algae Tec has commercialised a method of growing algae for nutrients, edible oil and biofuels. It includes solar concentrators - but green algae (like all green plants) can only use the visible light photons with wavelengths of 400 nanometres (nm) up to 700 nanometres.
Solar photovoltaic panels can convert concentrated solar energy into electricity - but silicon photovoltaic cells only use the photons with wavelengths up to 1100 nm. The infrared energy with photons having longer wavelengths only heat up the solar cells and reduce their performance.
Sundrop Farms has commercialised solar concentrators that use solar energy of any wavelength but only convert it to heat that is then used to convert seawater and saline ground water to fresh water for high-value food crops in arid regions.
An interesting possibility is to concentrate sunlight then split it into 3 beams - one with wavelengths that algae and other green plants use, one with wavelengths that silicon cells can convert efficiently to electricity, and the third that heats a transfer liquid to be used for, say, converting seawater to fresh water...
Calculating the return on investment is the challenging part of the puzzle. In particular, can the investment in concentrating sunlight that Algae Tec and Sundrop Farms exploit be made even more profitable by splitting the sunlight and using each of 3 beams in the most profitable application available for each?
The energy required to move an electron from the semiconductor atom to a conducting state is a fixed amount. The energy of a photon of light is determined by its wavelength, with shorter wavelength photons having higher energy than those with longer wavelengths.
Energy spectrum of sunlight and how it affects photovoltaic efficiency
A photon with wavelength 1,100 nanometres (nm), corresponding to short wave infra-red light has just enough energy to promote an electron in a silicon atom, the most commonly used semiconductor material.
All photons with a longer wavelength than this have insufficient energy to promote the electron and either pass straight through the PV cell or are absorbed as heat. This part of the solar spectrum cannot be used by the PV cell.
Photons with a shorter wavelength than 1,100nm have more energy than is required to promote the electron. The excess energy above that needed to move it into a conducting state is lost as heat.
These two factors combine to produce a theoretical upper limit to PV efficiency of around 31%.
All biological energy comes from sunlight and this energy encompasses the range of the electromagnetic spectrum known as light. The solar spectrum is shown below.
The green pigment, chlorophyll, plays a central role in photosynthesis. The
fact that it is green means that it absorbs blue and red light and reflects
green when it is illuminated by white (all wavelengths) light.
Light with wavelength longer than 700nm has insufficient energy to drive photosynthesis.
Ahmad Mojiri, Cameron Stanley and Gary Rosengarten
Royal Melbourne Institute of Technology
Melbourne, Australia
A photovoltaic thermal receiver that separates incoming light energy by wavelength can produce electricity and thermal output of 150° simultaneously.
8 January 2015, SPIE Newsroom. DOI: 10.1117/2.1201501.005704
Sunlight is an abundant source of energy that can be converted into heat and electricity using photothermal and photovoltaic technologies, respectively. Usually these devices are separate from each other, and occupy significant space on a rooftop or in a solar park. Combining thermal and electrical output in a single package would achieve several advantages, such as more efficient use of available space and light collection.
Figure 1. Spectral splitting mechanisms using (a) wave
interference effect and (b) selective volumetric absorption. HRI and LRI
correspond to high and low refractive index materials such as titanium
dioxide and silicon dioxide, respectively. A specific number (n) of
these layers are required to achieve suitable spectral splitting.
The solar spectrum consists of wavelengths in the range 400–2500nm, while silicon solar cells function most efficiently for the range 700–1200nm. Our beam-splitting mechanism separates light in the 700–1200nm range and directs it to the PV cells, sending the rest of the solar spectrum to a thermal absorber. The thermal and PV receivers are then being fed by two separate beams of light. The silicon cells remain cool at ambient temperatures.
We designed our system for a commercial parabolic trough: a partially curved, mirror-lined solar collector. We constructed a detailed ray tracing model (used to calculate the path of light waves through a system) for the proposed integration of our device in the solar concentrator, and optimized the dimensions of the receiver to maximize the energy yield of the system.
The University of Minnesota Solar Energy Laboratory develops technology using concentrated solar radiation for fuel and chemical production. It provided the inspiration for this article.
"In traditional biomass gasification, 20 to 30 percent of the biomass feedstock is burned to produce heat for the process. But if the required thermal energy is supplied from a concentrated solar source, all of the biomass can be converted into useful synthesis gas." (Read more...)
Burning any carbon-containing hydrocarbon or carbohydrate fuel - whether it is biomass or coal - uses some energy to break the chemical bonds that bind the atoms together in the molecules of the fuel and then releases some energy when those atoms combine with oxygen to produce carbon dioxide and water vapour.
Solar gasification of biomass: design and characterization of a molten salt gasification reactor
by Hathaway, Brandon Jay (2013)
A former doctoral student, Brandon Hathaway is now the lead research scientist at the University of Minnesota Solar Energy Laboratory.
"The reactor developed in this work allows for 3 kWth operation with an
average aperture flux of 1530 suns at salt temperatures of 1200 K with
pneumatic injection of ground or powdered dry biomass feedstocks
directly into the salt melt." (Read more...)
Post-run photo of the prototype solar biomass gasification reactor. It stays pretty hot under that insulation! pic.twitter.com/kkMwBopGVF
— Brandon Jay Hathaway (@DrBHathaway) August 6, 2014
Here is a diagram that represents the energy used and released by burning brown coal mined in the Gippsland Basin coal fields of Victoria, Australia:
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).
Tony Windsor recently wrote an article "No guts, no glory on clean energy" about the Abbott Government leading Australia backwards on clean energy.
Further to the statement, "In 2011, Tony Windsor spent some time in
Spain with Ross Garnaut, visiting a solar
thermal electricity plant that uses molten salts to store heat so that
power generation can take place at night or on bleak days", a modified
version of this Spanish solar thermal electricity plant with energy
storage is more economic.
The design may not be to everyone's liking but it serves an essential purpose.
At
present the coal industry is desperate to maintain market share against
inroads by renewable energy, natural gas and nuclear energy.
The
coal industry is deliberately increasing production of coal to drive
down the price. This helps to keep competitors out of the energy market.
The coal industry also has the capacity to pay financial
inducements to "buy" government decisions to build new coal-fired power
stations.
It can afford to lose money on this strategy for a
number of years. This is because every new coal-fired power plant will
operate for at least 40 years.
In the past decade a whopping 734 gigawatts of NEW coal-fired generating capacity has been built world-wide.
It
is essential to provide a financially superior large-scale power plant
design to place in front of every decision-maker before they commit to
constructing any more coal power plants. This may not be "ideal" but it
is pragmatic.
The capital cost of the Spanish solar thermal electricity plant can be reduced by almost seven-eighths:
A solar thermal plant (and coal power plants) only operate at about 30 percent thermal efficiency.
Solar thermal energy is available on average for about 6 hours a day.
To use solar thermal energy for 24 hours a day, the area of heliostats
must be 4 times greater than what is needed for operation for 6 hours.
The additional heliostats are needed to add thermal energy to a molten
salt heat bank.
If the efficiency of the power plant is doubled to 60 percent then the area of heliostats may be halved.
So,
how to double efficiency and collect solar thermal energy for only 6
hours - and be able to reliably generate electricity for 24 hours a day,
365 days a year? (Note this cuts the area of heliostats and their
capital cost and maintenance cost to just one-eighth of the Spanish
solar thermal electricity plant.)
The way to do this is to use
the solar thermal energy to convert coal and waste biomass to gas, then
use the gas to generate power in a combined-cycle gas turbine power
station. These can achieve 60 percent efficiency.
The amount of
coal used in this process is three-eighths of what a coal power would
use: solar energy provides all the energy needed for 6 hours out of
every 24. The efficiency is double what a coal power plant could
achieve, so only half as much coal is used in the remaining 18 hours of
each days' electricity generation.
CSIRO's solar air turbine meets BTOLA's indirectly-fired gas turbine
The CSIRO solar air turbine may be adapted to operate as BTOLA's indirectly-fired gas turbine - powered by either solar thermal energy or any combination of renewable biofuel or fossil fuel.
The result is a solar thermal power station that can generate electricity 24 hours a day, 7 days a week - on sunny days and cloudy days. The cost of solar thermal storage is avoided.
The BTOLA power generation system has reduced fuel-costs because the solar thermal heliostat field generates electricity from solar energy during sunny periods.
The capital cost of the integrated system is less than building 2 separate systems: the gas turbine and electricity generator are shared.
An indirectly-fired gas turbine used in a combined-cycle has slightly lower efficiency than a conventional combined-cycle gas turbine power station, but has lower maintenance costs as its turbine blades are not exposed to any combustion gases.
This approach complements the work CSIRO and GE are conducting with SolarGas power generation. In that approach, solar thermal energy is combined into the chemical bonds of biogas and/or fossil fuels.
This alternate approach leaves the different energy sources and fuels unchanged, and then uses them in any combination in an innovative power station design.
Both of these approaches overcome complaints that renewable energy sources are unreliable.
There is also a growing awareness that as the number of solar panels grows, the cost to consumers of an electricity grid and central power stations also grows as these energy resources are pushed to the margins in providing backup capacity on cloudy days.
The approach adopted by GE and CSIRO with SolarGas, and the approach described here - avoid this problem. No "stranded assets" are created. The same power generation infrastructure can be used with any combination of renewable and fossil fuels. A transition from reliance on fossil fuels to renewable energy need not be expensive or difficult.
CSIRO has designed and built Australia's largest solar thermal research facility which consists of a 30 metre high solar tower (the tallest in Australia) and high temperature receiver, and a 4000 square metre field of 450 heliostats. The facility is capable of concentrating solar energy at temperatures beyond 1000 ºC.
CSIRO will use the facility to develop and test one of the world’s most powerful solar air turbines to generate electricity from air and sunshine alone (almost all current systems require water as well as fossil fuel).
This 200 kiloWatt solar air turbine generates electricity which is then fed into the grid.
The pilot site covers an area of 4000 square metres and although this site is being used for research, a site of this size could generate enough electricity to power nearly 200 homes.
Technology Overview
BTOLA converts existing proven gas turbines to indirectly fired gas turbine engines allowing them to run on Biomass, waste products and other fuels lowering fuel costs and greenhouse gas emissions.
This is accomplished by
Removing existing combustion chamber
Installing BTOLA combustion chamber
Installing BTOLA start-up combustor
Installing BTOLA heat exchangers
Utilizing BTOLA heat recovery
Installing BTOLA control system
Cleaner Fuel Options
The gas turbine has been tested and achieved excellent results with these alternative fuels.
Why ?
Because the BTOLA solution is up to 70% cheaper to purchase, install and operate.
Capital Cost – Purchase and Installation costs over competing technology to utilize cheaper fuels
The solar and wind energy industries are in an "all-or-nothing" marketing campaign against coal and natural gas. At present the solar and wind energy industries have no commercial energy storage option to offer.
The CSIRO, GE Global Research and others are creating technology that solves all recognised issues. This technology is steadfastly ignored in media reports.
A combined cycle gas turbine (CCGT) power station fueled by natural gas that has been converted to syngas by solar thermal energy delivers 20 per cent renewable energy at the reliability and similar cost of a natural gas-only fueled CCGT power station.
Replace the natural gas with bio-methane and this power station will deliver 100 per cent renewable energy at the reliability and similar cost of a natural gas-only fueled CCGT power station.
Capture half of carbon dioxide collected in the bio-methane production process and this technology REMOVES carbon dioxide from the atmosphere. This is environmentally superior to both wind and solar technology.
SolarGas technology could help India’s efforts towards achieving energy security.
SolarGasTM technology was developed by Australia’s national science agency, the Commonwealth Scientific and Industrial Research Organisation (CSIRO).
Fueling Our Future
Vfos is the cleanest, quickest and most effective way to reduce carbon footprint and rein in the environmental impact of fossil fuels - while we still can.
Vfos product is prepared for shipment to power plants
Reduces emissions dramatically.
Converts waste into eco-friendly energy.
Total recycling - residue is then re-used.
Creates opportunities, high job creation.
No costly infrastructure changes needed.
What is Vfos?
Vfos is a renewable energy fuel that can be burnt alongside other fuels with a much greater heating value than conventional fossil fuels and 90% less CO2 emissions.
How does Vfos work?
Vfos is a total recycling package - made from salvaged wastes which are converted into an energy fuel with minimal residue.
Vfos contains no dangerous chemicals and has a near-zero sulphur reading of 0.001%, with ash content of 0.9% to coal's 15%.
BTOLA Indirectly fired gas turbine technology Technology Overview
BTOLA converts existing proven gas turbines to indirectly fired gas turbine engines allowing them to run on Biomass, waste products and other fuels lowering fuel costs and greenhouse gas emissions.
This is accomplished by
Removing existing combustion chamber
Installing BTOLA combustion chamber
Installing BTOLA start-up combustor
Installing BTOLA heat exchangers
Utilizing BTOLA heat recovery
Installing BTOLA control system
Cleaner Fuel Options
The gas turbine has been tested and achieved excellent results with these alternative fuels.
Why ?
Because the BTOLA solution is up to 70% cheaper to purchase, install and operate.
Capital Cost – Purchase and Installation costs over competing technology to utilize cheaper fuels
CSIRO has designed and built Australia's largest solar thermal research facility which consists of a 30 metre high solar tower (the tallest in Australia) and high temperature receiver, and a 4000 square metre field of 450 heliostats. The facility is capable of concentrating solar energy at temperatures beyond 1000 ºC.
CSIRO will use the facility to develop and test one of the world’s most powerful solar air turbines to generate electricity from air and sunshine alone (almost all current systems require water as well as fossil fuel).
This 200 kiloWatt solar air turbine generates electricity which is then fed into the grid.
The pilot site covers an area of 4000 square metres and although this site is being used for research, a site of this size could generate enough electricity to power nearly 200 homes.
Integration of a solar thermal heliostat field with a BTOLA indirectly-fired gas turbine
The solar air turbine may be modified to operate as an indirectly-fired gas turbine.
The result is a solar thermal power station that can generate 200 kiloWatts of electricity 24 hours a day, 7 days a week - on sunny days and cloudy days.
The BTOLA power generation system has lower fuel-costs because the solar thermal heliostat field is used to generate electricity during sunny periods.
The capital cost of the integrated system is lower than building 2 separate systems because they share the turbine and
200 kiloWatt generator.
On 17 November 2011, the NSW Government appears before a Parliamentary
Committee inquiring into Coal Seam Gas.
The NSW Government submission strongly favours rapid development of coal seam
gas.
It has no place for solar or any other zero emission technology.
A hybrid solar/biomass gasification option - if costed very
quickly - might persuade the Parliamentary Committee next Thursday to reject the
NSW Government's submission to commit NSW to 250 years reliance on Coal Seam
Gas.
At the least, it should defer a decision pending a more up-to-date analysis of alternative approaches to meeting future energy needs.
One such alternative approach - solar thermal gasification f biomass producing fuel for a Combined Cycle Gas Turbine (CCGT) power station is illustrated here - Providing Energy Without More CO2 Emissions.
Time is running out for real decisions that will determine the direction of the NSW energy industry throughout this century.
The NSW Government
believes that balanced co-existence of mining (including CSG) and
agriculture is not only possible, it is essential. ...NSW gas
consumption is projected to grow significantly from its current level
of around 160 Petajoules (PJ) per annum to 550PJ pa in the next 20
years. Current possible NSW CSG reserves represent over 250 years of
gas supply at that level. (Page 2)
The development of a
coal seam gas industry in NSW resulting from technological innovation
has created an opportunity for an abundant new cleaner energy
resource which was largely unknown until recently. The coal seam gas
industry has the potential to create thousands of regional jobs, and
add billions of dollars to the State economy, reduce our dependence
on imported petroleum for transport, and create new industries around
the availability of gas as a feedstock. (Page 4)
Table 3: Costs of CSG and other energy sources
Technology
Capital Cost (A$/kW
or $’000/MW)
Total
Cost or LRMC
$
/ MWh
Variable Cost
$
/ MWh
Black
coal - super critical (SC)
1,900
45.99
1.20
Black
coal - ultra super critical (USC)
2,400
54.00
1.20
Integrated
gasification Combined Cycle (IGCC)
2,100
56.85
1.50
Combined
Cycle Gas Turbine (CCGT)
1,050
58.38
4.85
Open
Cycle Gas Turbine (OCGT)
750
522.64
7.50
Nuclear
3,500
76.13
2.00
Hydro
2,000
71.93
2.00
Solar
thermal
5,000
224.37
1.50
Solar
Photovoltaic (PV)
7,529
384.38
1.50
Wind
2,400
93.31
1.60
Biomass
2,200
70.34
3.00
Geothermal
5,000
87.42
2.00
Coal
USC plus Carbon Capture & Storage (95%)
4,100
85.80
1.20
Gas
CCGT plus Carbon Capture & Storage (95%)
2,850
112.69
1.20
Source: ACIL Tasman
(May 2008), Projected energy prices in selected world regions
Notes:
Long Run Marginal
Cost (LRMC) is defined as the cost of an incremental unit of
generation capacity spread across each unit of electricity produced
over the life of the station. LRMC includes capital cost, fuel cost,
variable operating and maintenance costs.
Variable costs
include fuel costs and variable component of operating and
maintenance costs.
All costs are
based on A$ 2008 and exclude a carbon price.
CSG based base load
generation is in general less expensive compared to many other
technologies and when a carbon price is included it also becomes more
attractive than coal based power plants. (Pages 14-15)
