Introduction to your Supercritical CO2 Power Cycle

[:en]Supercritical carbon dioxide cycles have slowly become more popular in the engineering market for electricity generation from various sources. SCO2 is found to be an ideal working fluid for generating power cycles due to its high efficiency –more than supercritical or superheated steam, which results in lower cost of electricity.

Supercritical carbon dioxide is a fluid state where carbon dioxide is operated above its critical point which causes the compound to behave as both a gas and a liquid simultaneously with the unique ability to flow as a gas though at the same time dissolve materials like a liquid. SCO2 changes density over small difference in temperature or pressure, though stay in the same phase; allowing large amount of energy to be extracted at higher temperatures.

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Design Challenges of Boiler Feed Pump Turbines in Thermal Power Stations

[:en] The design of a boiler feed pump turbine features some unique characteristics that presents certain challenges in terms of efficiency management, varying operating ranges, and many other features.  In order better understand the accepted designs of Boiler Feed Pump Turbines (BFPTs), it is important to know how the operation of steam turbines used to drive boiler feed pumps can fundamentally improve fossil and nuclear plants.  Much like the design of mechanical drive turbines, feed pump turbines also feature the same thermodynamic objectives as the main turbine and all of the engineering difficulties with optimal blade design, rotor and bearing harmonic conditions, ideal flow path definitions, and so on.  However, some distinctions can make a BFPT design particularly distinct from a regular mechanical drive turbine.  Figure 1 shows a basic heat balance diagram for a plant using a boiler feed pump turbine arrangement.

boiler-post
Figure 1 – Simple Process Diagram for Plant with Boiler Feed Pump Turbine in AxCYCLE®

Inherent in its name, the BFPT must be fully compatible with the boiler feed pump. In other words, the necessary power and speed of the BFPT are determined by the requirements of the pump. In a fully integrated and dynamic system such as this, a large portion of the design requires developing a proper heat balance that will optimize the plant performance. In general, the boiler feed pump turbine uses both steam from the boiler and the main turbine to drive the mechanical shaft connected to the boiler feed pump. This arrangement has proven highly successful in efficiently applying the steam’s thermal energy throughout the plant. In certain arrangements, the BFPT can instead accept steam from cold reheat lines, main unit crossover piping lines, and different extractions from the main turbine. Regardless of the source, one distinction specifically unique to the BFPT is that it must accept steam from two separate sources.

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Explaining Geothermal Cycles

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Geothermal energy has become more and more popular globally due to its sustainability and economic stand point. Geothermal power plants run on a variety of temperatures and utilize hydrothermal resources (water/steam and heat) from below the earth surface to generate electricity for people’s daily consumption. Resources can come from dry steam or hot water wells.

There are three kinds of Geothermal cycle for power plants: binary cycle, dry steam and flash steam. Binary cycle power plants use the heat transfer from geothermal hot water to secondary fluids with a low boiling point at the lower end of standard geothermal temperature (225 to 360 F). This heat will cause the secondary fluid to bubble and turn into steam in the heat exchanger, which is then used to turn the turbine. Since water and secondary fluids are kept apart in the cycle, air emission is minimized.

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Minimizing Environmental Impacts of Geothermal Energy

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Geothermal energy is categorized as a “green energy”, with low emission of approximately 5% of carbon dioxide, 1% H2S, 1% sulfur dioxide and less than 1% of the nitrous oxide of an equal sized fossil or coal power plant. Concentrations of each environmentally disruptive gases are controlled by temperature, composition of fluid, and geological setting. Although most of the geothermal emissions commonly come from existing geothermal resource gas, some percentage of the emission also comes from various processes of the energy conversion process. Non-condensable gases are also emitted as a part of high temperature process of geothermal energy conversion.

According to various studies, the type of geothermal power plant design would really impact the production rate of the mentioned gasses. The selection between open-loop and closed (binary)-loop system is essential while taking into consideration air emission. Geothermal plants to this date are commonly separated into three main cycle design: dry-steam, flash-steam or binary –the first two extensively generate more greenhouse gasses (GHGs) compared to the last. In a binary loop system, gases which are removed from the system will not be transferred to the open atmosphere, instead, after transferring the heat gasses will be run through back to the ground, and result in minimal air pollution. In contrary, open-loop system emits all of the emission gas contained such as hydrogen sulfide, carbon dioxide and many more. There are also different factors which cause the technology to emits gases that are naturally present in the fluid such as fluid chemistry/composition, fluid phase, and geological setting to temperature.

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Development of Molten Salt Energy Storage

[:en]Over the past couple of years, energy storage technology has significantly evolved to meet engineering demand and political regulations. This wasn’t initially looked as a desirable investment due to the high production cost, however over time, exploration of such technology by bigger companies has driven down the manufacturing cost and generated more demand. With occurrences such as rapid capital raise of smaller start-up companies, to the acquisition of Solar City by Tesla, the market of energy storage is predicted to continue growing. The technology allows for collection of energy produced to be used at a later time. Energy storage systems have wide technology variation to manage power supply – from thermal, compressed air to everyday batteries.

blog-post-2-image-1Molten Salt Usage

The usage of molten salt in thermal energy storage applications has become more common. In commercial solar energy storage, molten salt (from potassium nitrate, lithium nitrate and more) is used in conjunction with concentrated solar energy for power generation. Molten salts are able to absorb and keep heat energy transferred from the fluid mediator, then to transfer it again when it’s needed. In the liquid state, molten salt has a similar state to water. It also has the capacity to retain temperatures of  1000 Fahrenheit. Though efficiency is known to be lower than other storage media such as batteries, (70% vs 90%), the main advantage of the usage of molten salt is lower costs which allows the technology to be implemented in a higher volume production.

How Molten Salt Energy Storage Works

Using solar energy as the main source of energy, heliostats (mirrors used to track sun/solar heat) are used to reflect the solar radiation into an energy receiver at the power plant. Molten salt then is used to collect this heat energy from the concentrated pool. The molten salt will later be stored. When power is needed, hot molten salt is transferred to a HX (or steam generator) to produce steam at a high pressure and temperature. The steam then will be used for electricity generation as the live steam in a conventional steam power plant. After exiting the generator, molten salt will then be transferred back to the thermal storage tank to again absorb energy.

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Working with Geothermal Heat Pumps

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A geothermal heat pump utilizes earth’s thermal energy as a way to manipulate temperature. This is seemingly attractive toward HVAC utilization due to the relatively high efficiency as well as economic benefit. Temperature fluctuations below ground are relatively low as earth absorbs solar energy all year round and insulates the heat underground. Taking advantage of this event, geothermal energy heat pump application for residential and commercial building uses the “underground” as a heat source/sink.

geothermal heat pumps
Source: http://tidewatermechanical.com/geothermal-heat-pumps/

How does geothermal heat pump work?

A heat pump system mainly consists of a heat-pump unit, a pipeline loop functioning as a heat exchanger for a desired area (it can be horizontal, vertical or installed to an aquatic medium), and a duct – to deliver the controlled temperature flow to the consumer.

Fluid is pumped through an installed pipeline loop which transfers heat based on the season. During the hotter season (summer), heat will be absorbed from the air in the building, transferred into the ground and then cooler air will be circulated to the designated area. The contrary happens during the winter. In colder months, heat will be transferred into the fluid from the ground and collected heat will be distributed.

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The Economic Optimization of Renewable Energy

[:en]Global warming has been a very popular topic these days. With up-trend of clean technology and realization that strict climate policy should be implemented, demand of renewable energy sky-rocketed as conservative plants popularity falls. Number of coal power plants have significantly dropped since its peak era, being known as the largest pollutant contributor as it produces nitrogen oxide and carbon dioxide, the technology is valued less due to its impact on nature. Renewable energy comes from many sources: hydropower, wind power, geothermal energy, bio energy and many more. The ability to replenish and having no limit in usage and applications make renewable energy implementations seems attractive. Aside from that, they also produce low emission, sounds like a win-win solution for everyone. Theoretically, with the usage of renewable energy, human-kind should be able to meet their energy need with minimal environmental damage. With growth rate ranging from 10% to 60% annually, renewable energy are getting cheaper through the technology improvements as well as market competition. In the end, the main goal is still to generate profit, though these days taking impact on nature into the equation is just as important. Since the technology is relatively new, capital cost still considerable higher compared to some cases with more traditional (–and naturally harmful) implementations. So the question is: how to maximize the economic potential of a renewable energy power generation plant?

The Economic Optimization of Renewable Energy

Living up to the maximum potential of any power generation plant starts in the design process. Few examples for solar power plant: designers should take into consideration type and quality of panels, it’s important to see the economic-efficiency tradeoff before jumping into investment; looking into the power conversion is also one of the most important steps, one should take into consideration that it would be worthless to produce more energy than the capacity that are able to be transferred and put to use, though too low energy generation would mean less gross income.

Another example, for a geothermal power plant, many studies have shown that boundary conditions on each components play a big role in determining the plant’s capacity and efficiency. High efficiency is definitely desired to optimize the potential of a power plant and minimized the energy loss. Though, should also be compared to the economic sacrifice; regardless of how good the technology is, if it doesn’t make any economic profit, it would not make sense for one to invest in such technology. Low capital cost but high operating expenses would hurt the economic feasibility in the long run, whereas high capital cost and low operating expense could still be risky since that would mean a higher lump sum of investment upfront, which might or may not breakeven nor profitable depending on the fluctuation of energy market.

Modern technology allows investors and the engineering team to make this prediction based on models developed by the experts. SoftInWay just recently launched our economic module, check out AxCYCLE to optimize your power plant!

Reference:

[1] Optimal design of geothermal power plants 

[2] Strategies in tower solar power plant optimization[:cn]Global warming has been a very popular topic these days. With up-trend of clean technology and realization that strict climate policy should be implemented, demand of renewable energy sky-rocketed as conservative plants popularity falls. Number of coal power plants have significantly dropped since its peak era, being known as the largest pollutant contributor as it produces nitrogen oxide and carbon dioxide, the technology is valued less due to its impact on nature. Renewable energy comes from many sources: hydropower, wind power, geothermal energy, bio energy and many more. The ability to replenish and having no limit in usage and applications make renewable energy implementations seems attractive. Aside from that, they also produce low emission, sounds like a win-win solution for everyone. Theoretically, with the usage of renewable energy, human-kind should be able to meet their energy need with minimal environmental damage. With growth rate ranging from 10% to 60% annually, renewable energy are getting cheaper through the technology improvements as well as market competition. In the end, the main goal is still to generate profit, though these days taking impact on nature into the equation is just as important. Since the technology is relatively new, capital cost still considerable higher compared to some cases with more traditional (–and naturally harmful) implementations. So the question is: how to maximize the economic potential of a renewable energy power generation plant?

The Economic Optimization of Renewable Energy

Living up to the maximum potential of any power generation plant starts in the design process. Few examples for solar power plant: designers should take into consideration type and quality of panels, it’s important to see the economic-efficiency tradeoff before jumping into investment; looking into the power conversion is also one of the most important steps, one should take into consideration that it would be worthless to produce more energy than the capacity that are able to be transferred and put to use, though too low energy generation would mean less gross income.

Another example, for a geothermal power plant, many studies have shown that boundary conditions on each components play a big role in determining the plant’s capacity and efficiency. High efficiency is definitely desired to optimize the potential of a power plant and minimized the energy loss. Though, should also be compared to the economic sacrifice; regardless of how good the technology is, if it doesn’t make any economic profit, it would not make sense for one to invest in such technology. Low capital cost but high operating expenses would hurt the economic feasibility in the long run, whereas high capital cost and low operating expense could still be risky since that would mean a higher lump sum of investment upfront, which might or may not breakeven nor profitable depending on the fluctuation of energy market.

Modern technology allows investors and the engineering team to make this prediction based on models developed by the experts. SoftInWay just recently launched our economic module, check out AxCYCLE to optimize your power plant!

Reference:

[1] Optimal design of geothermal power plants 

[2] Strategies in tower solar power plant optimization[:]

Upcoming Webinar: Power Plant Cost Estimation

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Cost Estimation and Economic Analysis for Power Plants

Thursday, January 21st | 10:00 – 11:00 AM EST

The Kendall Cogeneration Station in Cambridge, MA

Registration is open for our first webinar of 2016.

The processes of power plant design, enlargement, and redesign must consider certain factors, such as technological scheme, basic cycle parameters, equipment configuration, and fuel type. These factors have long reached beyond the scope of the technical and physical, and must consider economic criteria. Economic indicators are fundamental when selecting a specific solution. Therefore, even at the initial stages of a project, engineering problems should be considered in parallel with the assessment of economic efficiency. In addition, a power plant is a very complex entity, and introductory capital costs cannot be the only economic criteria considered. The economic indexes over the entire lifecycle of the plant must be accounted for.

The modern world has seen extensive investment in the field of cost estimation. The approximate estimation of cost and economic efficiency of a power plant, however, is a complicated and time-consuming process. It demands a high level of knowledge and information.

In order to simplify this process, and make it available for the engineering community, SoftInWay, a leading turbomachinery solutions provider, developed the new AxCYCLE Module for Economic Analysis. This webinar will demonstrate the module and discuss its extensive capabilities and applications.

We look forward to a great webinar and your challenging questions. Please register ahead of time and if you have any specific questions, let us know during the registration so that we can try to incorporate the answers into our presentation.

[su_button url=”http://www2.softinway.com/powerplanteconomics” target=”blank” background=”#ef322d” color=”#f6f1f1″ center=”yes” radius=”round” icon=”icon: arrow-right” title=”Register”]Register[/su_button]

 [:cn]

Cost Estimation and Economic Analysis for Power Plants

Thursday, January 21st | 10:00 – 11:00 AM EST

The Kendall Cogeneration Station in Cambridge, MA

Registration is open for our first webinar of 2016.

The processes of power plant design, enlargement, and redesign must consider certain factors, such as technological scheme, basic cycle parameters, equipment configuration, and fuel type. These factors have long reached beyond the scope of the technical and physical, and must consider economic criteria. Economic indicators are fundamental when selecting a specific solution. Therefore, even at the initial stages of a project, engineering problems should be considered in parallel with the assessment of economic efficiency. In addition, a power plant is a very complex entity, and introductory capital costs cannot be the only economic criteria considered. The economic indexes over the entire lifecycle of the plant must be accounted for.

The modern world has seen extensive investment in the field of cost estimation. The approximate estimation of cost and economic efficiency of a power plant, however, is a complicated and time-consuming process. It demands a high level of knowledge and information.

In order to simplify this process, and make it available for the engineering community, SoftInWay, a leading turbomachinery solutions provider, developed the new AxCYCLE Module for Economic Analysis. This webinar will demonstrate the module and discuss its extensive capabilities and applications.

We look forward to a great webinar and your challenging questions. Please register ahead of time and if you have any specific questions, let us know during the registration so that we can try to incorporate the answers into our presentation.

[su_button url=”http://www2.softinway.com/powerplanteconomics” target=”blank” background=”#ef322d” color=”#f6f1f1″ center=”yes” radius=”round” icon=”icon: arrow-right” title=”Register”]Register[/su_button]

 [:]

Explaining the Binary Power Cycle

Geothermal energy is known to be a reliable and sustainable energy source. As the world gives more attention to the state of the environment, people lean towards using more energy sources which have little to no impact on nature. Where it is true that currently no other energy source can outperform fossil fuel due to its energy concentration, geothermal energy is a good prospect as a temporary substitute until a better form of energy supply is found.

There are two types of geothermal power sources; one is known as the steam plant and the other is the Binary cycle. Binary cycles have the conceptual objectives of: high efficiency — minimizing losses; low cost to optimize component design; and critical choice of working fluid. This particular type of cycle allows cooler geothermal supply to be used, which has a huge benefit since lower temperature resources are much more common in nature.

blog - binary power1blog - binary power2

 

 

 

 

 

 

The way a binary cycle works can be explained using the diagram shown above. Since the temperature of geothermal source is not high enough to produce steam, hot water is fed into a heat exchanger. From there, secondary liquid with lower boiling water than water i.e. isobutane, absorbs the heat generated. As the steam of secondary liquid moves the turbine, electricity will then be produced. This whole process repeats in a cycle since the secondary fluid will then condense back to its liquid state and being used for the same process.

From the process described above, it can be seen that binary cycle is a self-contained cycle — ‘nothing’ goes to waste. This fact leads to the potential of having low producing cost energy source from binary power cycle. That being said, due to the lower temperature, the conversion efficiency of the geothermal heat is also considerably low. Consequently, Carnot efficiency of such process is lower than most power cycles. Large amount of heat is required to operate a binary cycle, leading to a better and larger equipment. Not only that since a bigger amount of heat energy has to be let out to the environment during the cycle, a sufficient cooling system must be installed. Although the production cost is found to be lower, the investment cost for installation would be very expensive. Then, the main question to this particular technology implementation would be how to improve the quality of production and economic feasibility?

First, one of the main aspect of binary power cycle is to overcome water imperfection as a main fluid. Consequently choosing optimal working fluid is a very essential step. Characteristic of optimal working fluids would include a high critical temperature and maximum pressure, lower triple-point temperature, sufficient condenser pressure, high vaporization enthalpy, and other properties.

Second, it was studied on multiple different events that well-optimized ORCs perform better than Kalina cycles. The type of components chosen in the cycle also affect the cycle performance quite substantially, i.e plate heat exchanger was found to perform better in an ORC cycle in the geothermal binary application compared to shell-and-tube. Addition of recuperator or turbine bleeding also have the potency to improve the overall performance of a binary cycle plant. It is important to model multiple thermodynamic cycle to make sure that the chosen one is the most optimized based on the boundary conditions. While designing ranges of thermodynamic cycles, it is common that the cycle is modeled based on ideal assumptions. For binary cycle in geothermal application, plant efficiency would be the most important parameter. In order to achieve a desired plant efficiency, both cycle efficiency and plant effectiveness should be maximized.

Additionally, pinch-point-temperature between condenser and heat exchanger is a substantial aspect to pay attention to, even the smallest change of in temperature is considered a significant change. Thus, including this parameter is a very important aspect.

This particular cycle has many potentials which haven’t been explored. Enhance the advantages of your binary power cycle using our thermodynamic tool, AxCYCLE.

Ref:
https://en.wikipedia.org/wiki/Binary_cycle
http://www.technologystudent.com/energy1/geo3.htm
http://www.researchgate.net/publication/229148932_Optimized_geothermal_binary_power_cycles

What Turbomachinery does to Avert Climate Change (Part 2 of 2)

[:en]Last week I described two ways which the turbomachinery industry addresses climate change. This week, I explain two more:

  1. Waste Heat Recovery

Even though processes are becoming more and more efficient they are still mostly wasteful (Figure 1).

Figure 5 Typical energy distribution in a system
Figure 1 Typical energy distribution in a system

The excess energy from processes is eventually released into the environment but bringing down the temperature of the exhaust allows multiple things; direct reduction of the global warming potential as well as possibility to utilize this heat to boil a working fluid before running it through a turbine where it can generate some power without requiring burning additional fuel. A well-known example of such a system is the traditional gas-steam cycle that allows turning a 45% efficient gas turbine cycle into a 60% system by utilizing the gas turbine exhaust heat to boil some water in a secondary loop before passing the resulting steam through a different turbine. In the same manner waste heat recovery can be applied with different fluids (including the trending refrigerants like R134a & R245fa, steam and the state-of-the-art supercritical CO2 as shown on Figure 2) and a multitude of applications; internal combustion engines, steel production plants, marine transports, etc.

Figure 6 Example of a simple, recuperated Brayton, supercritical CO2 cycle that uses the exhaust flow of a gas turbine to heat its working fluid
Figure 2 Example of a simple, recuperated Brayton, supercritical CO2 cycle that uses the exhaust flow of a gas turbine to heat its working fluid
  1. Selection of the best working fluid

Whether it’s deciding to design the main energy conversion cycle or its waste heat recovery system one of the critical parameters to pay close attention to is the working fluid selection; good selection of the fluid will often lead to make a compromise between cost/availability, thermodynamic performance (see Figure 3) and environmental friendliness. One must make sure that the performances of the designed cycle with the chosen fluid are high enough and the fluid cheap enough to make the concept financially viable without sacrificing pollution considerations which can prove devastating in case of leaks.

Figure 7 Example of a fluid performance comparison at different temperatures
Figure 3 Example of a fluid performance comparison at different temperatures

The working fluid selection is also performed so that in addition to the environmental footprint being reduced the physical footprint is minimized as well; this is done through the selection of high density fluids (helium, SCO, etc.) which allows for a reduction in component size and therefore cost (as portrayed on Figure 4), – indirectly it also allows for less material being produced which also “saves trees”.

Figure 8 Example of difference in power density between supercritical carbon dioxide (left) and steam (right) for a 10 MW power turbine
Figure 4 Example of difference in power density between supercritical carbon dioxide (left) and steam (right) for a 10 MW power turbine
[:cn]Last week I described two ways which the turbomachinery industry addresses climate change. This week, I explain two more:

  1. Waste Heat Recovery

Even though processes are becoming more and more efficient they are still mostly wasteful (Figure 1).

Figure 5 Typical energy distribution in a system
Figure 1 Typical energy distribution in a system

The excess energy from processes is eventually released into the environment but bringing down the temperature of the exhaust allows multiple things; direct reduction of the global warming potential as well as possibility to utilize this heat to boil a working fluid before running it through a turbine where it can generate some power without requiring burning additional fuel. A well-known example of such a system is the traditional gas-steam cycle that allows turning a 45% efficient gas turbine cycle into a 60% system by utilizing the gas turbine exhaust heat to boil some water in a secondary loop before passing the resulting steam through a different turbine. In the same manner waste heat recovery can be applied with different fluids (including the trending refrigerants like R134a & R245fa, steam and the state-of-the-art supercritical CO2 as shown on Figure 2) and a multitude of applications; internal combustion engines, steel production plants, marine transports, etc.

Figure 6 Example of a simple, recuperated Brayton, supercritical CO2 cycle that uses the exhaust flow of a gas turbine to heat its working fluid
Figure 2 Example of a simple, recuperated Brayton, supercritical CO2 cycle that uses the exhaust flow of a gas turbine to heat its working fluid
  1. Selection of the best working fluid

Whether it’s deciding to design the main energy conversion cycle or its waste heat recovery system one of the critical parameters to pay close attention to is the working fluid selection; good selection of the fluid will often lead to make a compromise between cost/availability, thermodynamic performance (see Figure 3) and environmental friendliness. One must make sure that the performances of the designed cycle with the chosen fluid are high enough and the fluid cheap enough to make the concept financially viable without sacrificing pollution considerations which can prove devastating in case of leaks.

Figure 7 Example of a fluid performance comparison at different temperatures
Figure 3 Example of a fluid performance comparison at different temperatures

The working fluid selection is also performed so that in addition to the environmental footprint being reduced the physical footprint is minimized as well; this is done through the selection of high density fluids (helium, SCO, etc.) which allows for a reduction in component size and therefore cost (as portrayed on Figure 4), – indirectly it also allows for less material being produced which also “saves trees”.

Figure 8 Example of difference in power density between supercritical carbon dioxide (left) and steam (right) for a 10 MW power turbine
Figure 4 Example of difference in power density between supercritical carbon dioxide (left) and steam (right) for a 10 MW power turbine
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