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

Upcoming Webinar: Design of Waste Heat Recovery Systems Based on Supercritical ORC for Powerful Engines

C836150Our next webinar is on October 8th! Join us as we discuss Design of Waste Heat Recovery Systems Based on Supercritical ORC for Powerful Engines.

Waste heat recovery is a hot topic (pun intended) that SoftInWay embraced rapidly. Numerous projects have been successfully performed on both the thermodynamic and the turbomachinery components levels.

In this webinar, we will discuss the case of a powerful ICE that can now benefit from a 20% boost in power due to waste heat recovery using a supercritical organic Rankine cycle (SORC). Different configurations, levels of complexity and parameters are studied and compared for the thermodynamic cycle as well as different fluid. Moreover, to show you that SORC is the way to go the results obtained are compared to what would be obtained with a different type of WHR system; double-pressure water steam cycle.

The session will include:

  • Introduction to the powerful ICE considered and its waste heat sources
  • Working fluid and parameters selection for the waste heat recovery system (WHRS)
  • Comparison of different configurations of WHRS SORC
  • Preliminary design of the turbine(s)

Who should attend?​

  • Engineers actively contributing to making their processes more efficient.
  • Engineers working in the mechanical, aerospace, automotive, marine, power generation industries who want to optimize their process equipment by utilizing untapped heat.
  • Engineering students looking for a comprehensive and state-of-the-art case study to optimize existing equipment allowing them to widen and deepen their understanding of waste heat recovery to meet the requirements of future employers.
Register

Analyzing Thermal Power Generation Efficiency

Figure 1 - Thermal Power Plant Layout
Figure 1 – Thermal Power Plant Layout

Steam turbine power generating plants, also known as Thermal Power stations, are the most conventional type of electricity production today. Most of today’s electricity power is generated though this technology. Naturally, as implied by its name, a thermal power station uses steam power as its prime mover to convert energy in coal, or other fossil fuel, by heating water to steam and utilizing Rankine cycle principles to generate heat and electricity.

The basic theory of thermal power generation is pretty straight forward: in a simple thermodynamic cycle, saturated liquid water is heated to steam. The working fluid will then pass through a steam turbine, where its energy is converted to mechanical work to run the generator and produce the electricity. Then fluid will be condensed to be recycled back in the heater. Just as simple as that, electricity power is generated from the cycle based on Rankine cycle principle.

The utilization of thermal power station comes with the advantage of economical initial and generation cost, easy maintenance and simple cycle operation in practice. That being said, there are also couple major drawbacks associated to the technology, primarily, low overall efficiency –due to the nature of Rankine cycle’s characteristic of thermal efficiency and environmental issues.

There are many scientific reasoning behind thermal power generation’s low efficiency. It is important to know the reasons why to engage in a better technology. These are the primary reasons:

  • During the combustion of carbon, effective conversion more or less is found to be 90%, this happen primarily due to limitation of heat transfer where some heat are lost into the atmosphere. Coal also contains moisture that vaporizes and take the latent heat from combustions.
  • The thermodynamic step, working on Rankine cycle principle, is where 50% (or more) efficiency is consumed. When the steam is condensed for re-use, latent heat of condensation is lost in the cooling water, which decreases the energy input by a very significant magnitude. Losses can also happen in the blades and other components. The Rankine cycle efficiency is determined by the maximum temperature of steam that can be transferred through the turbine, which means the efficiency is also constrained by the temperature associated with the cycle. Two other main factors that affect the thermal efficiency of power plants are the pressure of steam entering the turbine and the pressure in the condenser. That being said, a cycle with supercritical pressure and high temperature usually results to a higher efficiency.
  • During a conversion of mechanical to electrical, some efficiency loss happens in the generator and transformer. A small percentage of energy generated will then be used for internal consumption.

Knowing the causes of low efficiency leads us to the next question: What are the steps to optimize our thermal power plant efficiency?

  • Since thermal efficiency depends on temperature and pressure, it can be improved by using high pressure and temperature steam, though obviously it will be limited based on the boundary conditions of the operating system. A lower pressure can also be set in the condenser.
  • Improvement could also be implemented by the application of reheating steam technology between turbine stages.
  • Waste heat recovery optimization, capture excess heat for reuse, and install insulation to reduce any losses.
  • Upgrading major systems/components of thermodynamic cycles and renewing materials to reduce natural losses in efficiency due to age.
  • Improve efficiency monitoring system to enable instant detection of losses as well as analyzing efficiency based on real data.

These are just some ways that could be utilized to optimize power generation efficiency, indeed each of the steps come with their own specific obstacles of implementation, but there are infinite ways that can be explored to advance the technology.

Learn more about maximizing your power plant productivity through our webinars and explore our tools to help with your efficiency optimization for power generation and component design!

Sources:
http://www.learnengineering.org/2013/01/thermal-power-plant-working.html

New Release: AxCYCLE v. 4.0

We have just released the newest version of AxCYCLE, our software tool for thermodynamic cycle design and analysis. AxCYCLE 4.0 has some brand new features that will inevitably aid you in designing optimal Gas, Steam, Combined, Turbocharger, Supercritical CO2, Organic Rankine, and Waste Heat Recovery Cycles.

Take a look at the latest updates and additions:

Turbine Efficiency Calculation
In previous versions of AxCYCLE, efficiency was an input parameter that needed to be changed manually for each off-design condition. The Calculated Efficiency option will automatically recalculate the efficiency for off-design conditions.

blog - axcycle 4.0

New Components
Several new components were added to the AxCYCLE library for more sophisticated and customizable cycles.

Bearing: Used to simulate mechanical energy losses in bearings. The estimated mechanical losses are assigned as a power value and are accounted for in the total energy balance

Gearbox: Used to simulate the mechanical energy transfer between two shafts considering mechanical energy losses in the gearbox. These losses are measured using a gearbox efficiency value.

End Seal: Used to simulate seal leakage. The value of the leakage depends on the difference between the upstream and downstream pressure.

Steam Cycle Builder
AxCYCLE’s new wizard for the creation of basic steam cycles. It can be used for steam cycles with regenerative heating, optional moisture separators, and re-heaters. The Builder creates a cycle diagram with the correct fixed conditions and initial values, meaning the generated cycle is ready for calculation! It does all of the work for you!

Learn more about AxSTREAM and AxCYCLE on our website, or email us at info@softinway.com to find out exactly how we can help with your next turbomachinery project.

How much more can I get with what I have?

Gas turbines are continuing their trend in becoming more efficient with each generation. However, the rate at which their efficiency increases is not significant enough to match more and more constraining environmental goals and regulations. New technologies like combined cycles therefore need to be used to increase cycle-specific power (more power produced without burning additional fuel).

The first generation of combined cycles featured a bottoming steam cycle that uses the heat from the gas turbine exhausts to boil off water in order to power a turbine and generate power. This traditional approach has been around since about 1970 and nowadays allows obtaining an additional 20% in cycle thermal efficiency (40% in simple gas turbine cycle configuration vs. 60% as a combined gas-steam cycle).

Figure 1: General efficiency increases over time for simple and combined cycle gas turbines
Figure 1: General efficiency increases over time for simple and combined cycle gas turbines
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
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

While this traditional approach is definitely effective, it does have some drawbacks; the equipment usually takes a significant amount of 3D space, there is always the risk of corrosion and substantial structural damage when working with 2-phase fluids, and so on. This, therefore, allows for different technologies to emerge, like supercritical CO2 cycles.

A supercritical fluid is a fluid that is used above its critical pressure and temperature and therefore behaves as neither a liquid nor a gas but as a different state (high density vs gas, absence of surface tensions, etc.). As a working fluid, supercritical CO2 has numerous advantages over some other fluids, including a high safety usage, non-flammability/toxicity, high density, inexpensiveness and absence of 2-phase fluid.

 

Figure 3: Example of difference in power density between supercritical carbon dioxide (left) and steam (right) for a 10 MW power turbine
Figure 3: Example of difference in power density between supercritical carbon dioxide (left) and steam (right) for a 10 MW power turbine

Moreover, steam turbines are usually difficultly scalable to small capacities which mean that they are mostly used in a bottoming cycle configuration for high power gas turbines. On the other hand supercritical CO2 (Rankine) cycles can be used for smaller machines as well as the bigger units while featuring an efficiency comparable to the one of a typical Rankine cycle and estimated lower installation, operation and maintenance costs.

Figure 4 Cycle efficiency comparison of advanced power cycles (source: A Supercritical Carbon Dioxide Cycle for Next Generation Nuclear Reactors. Dostal, V., 2004
Figure 4 Cycle efficiency comparison of advanced power cycles (source: A Supercritical Carbon Dioxide Cycle for Next Generation Nuclear Reactors. Dostal, V., 2004

The paper I presented at the ASME Power & Energy 2015 compares different configurations of SCO2 bottoming cycles for an arbitrary case for different boundary conditions before applying the selected cycle to a wide range of existing gas turbine units. This allowed determining how much additional power could be generated without needing to burn additional fuel and the results were far from insignificant! For the machines studied the potential for power increase ranges from 15% to 40% of the gas turbine unit power. Want to know how much more power you can get with your existing machines? Contact us to get a quote for a feasibility study before designing the waste heat recovery system yourself or with our help.

Turbo Expo 2015 – What We’re Excited For

In a few weeks, SoftInWay will be on its way to Montreal, Canada for ASME’s Turbo Expo! We are looking forward to a busy and exciting conference.

What we’re most excited for:

1. Montreal AfterWork: Professional Networking Event
This event is being held for professionals involved in Energy, Technology, Finance, and Startups to meet and network in a casual and enjoyable environment. All Turbo Expo attendees and local Montreal professionals are welcome to come by, have a drink, and chat about the latest developments in their field!

Date/Time: 6:30-9:00pm | Tuesday, June 16, 2015
Location: Santos Tapas Bar | 191 Rue St Paul W, Montreal, QC, H2Y1Z5 Canada
Attire: Business Casual
Registration: www.zurichafterwork.com/rsvp/

2.  SoftInWay Stage Presentations

Continue reading “Turbo Expo 2015 – What We’re Excited For”

Innovative Boost of Larger Internal Combustion Engines

The last few decades have brought with them a dramatic increase in the development and use of turbochargers in automobiles, trains, boats, ships, and aircrafts. There are several reasons for this growth, including rising demand for fuel efficiency, stricter regulations on emissions, and advancements in turbomachinery design. Turbochargers are appearing more and more and are replacing superchargers.

turbocharger
Turbocharger

 

Turbochargers are not the only turbomachinery technology growing in popularity in the marine, automobile, and railroad industries. Organic Rankine Cycles are being applied to take advantage of the exhaust gas energy and boost engine power output. ORCs, a system for Waste Heat Recovery, improve the overall efficiency of the vehicle, train, or boat, and reduce specific emissions.

As the size of the engines we consider increases, there is more heat available to recuperate, and more potential WHR systems to use. For instance, we can consider different combinations of these systems with both non-turbocharged and turbocharged engines. We are able to design and compare engine boost system combinations, with and without a turbocharger, with and without a blowdown turbine, and with and without a WHR system, at the cycle and turbine design levels.

In our upcoming webinar, we will do just that. We will design different combinations for larger ICEs and compare the results. This webinar will also cover introductions to these systems and application examples for supplementary power production systems in the automotive and marine industries.

We hope you can attend! Register by following the link below.

Register

 

Power Production Does Not Have To Be So Wasteful

Whether it’s to drive you to work, power up your electronic devices, fly you to your holiday destination (extraterrestrial or not), or even set up the perfect lighting for this Valentine’s Day, your daily life requires power production. Although renewable energies are gaining popularity, many people remain unprepared to make the complete switch to these innovative power sources (except Iceland). Making the things we have more “energy efficient” or “green” has become an attractive marketing tool for many of businesses.

Presentation of the boundary conditions, unrecuperated and recuperated waste heat recovery cycles in AxCYCLE™
Presentation of the boundary conditions, unrecuperated and recuperated waste heat recovery cycles in AxCYCLE™

Continue reading “Power Production Does Not Have To Be So Wasteful”

Sustainable Turbomachinery

iStock_000015544357MediumThis past Tuesday was the 44th celebrated Earth Day. On Earth Day, more than 100 countries join together to literally stop and smell the roses, appreciate the splendor and beauty of Mother Nature and take extra efforts to be more conscientious for our shared home.

Turbomachinery, though not always the first thing that comes to mind when speaking on the subject of green technology, plays an important role toward our efforts for a more sustainable environment.
Continue reading “Sustainable Turbomachinery”

Should You Be Implementing the Organic Rankine Cycle?

To have a successful application of an ORC system, the availability of an adequate heat source is crucial. In principal every heat-generating process, such as burning fossil fuel, can be taken as a heat source for ORC.

However, the aim is to improve energy efficiency and sustainability of new or existing applications with the focus on waste heat and renewable energy sources.

Three sectors have been identified as potential sources for the application of ORC power generation: Continue reading “Should You Be Implementing the Organic Rankine Cycle?”

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