Many factors have converged over the last few years to increase the opportunities for generating plants to take advantage of high spot market power prices. There is increasing value in improving the ability of existing gas turbines units to get on-line quickly (fast start) and/or to produce more power when they are on-line.
TTS has supported customers in identifying multiple ways to achieve both of these goals. The strategies to support fast start include reconfiguring fuel systems to eliminate purge requirements during startup, addressing other startup delay issues and improving start reliability and repeatability.
Opportunities to increase power output include optimizing existing firing temperature settings, increasing mass flow, implementing and optimizing peak firing operation and associated combustion system performance. Our recent webinar covers all of these strategies and the associated cost/benefit estimates. You can view our webinar here:
In our latest blog, we are reviewing the points we covered in our CCJ webinar. Learn more about how to take advantage of opportunities in the market with minimal upgrades and modifications to keep your legacy asset relevant.
- Electricity consumption – As coal plants are retired and phased out, electricity demand continues to grow across the country.
- Vintage Units – If they are reliable, flexible and available, vintage gas fire turbines can fill the need in the energy market.
- Renewables – while they are projected to make up to 50% of power generation in the United States by 2035, they will always need a reliable backup source due to unpredictability.
- New power plant – Planning and building a new plant is time-consuming, expensive and requires navigating regulatory and planning permissions.
- Natural Gas – Compared with coal, natural gas is a cheap and clean fossil fuel. Likewise, it will continue to serve the energy market for the future.
- Margin – The reserve margin is decreasing.
- Market Opportunities – Spot market opportunities are increasing the high value generation windows. Fast start opportunities increase with the increase of renewable capacity increases.
High-Value Generation Opportunities
The goal is to get the most out of your legacy machinery. This includes optimizing your plant with updated capabilities and technology to produce more output when market prices are higher.
This includes Fast Start programs, which require plants to be ready to output power in as little as 10 minutes to maintain grid stability.
Ways to Get Output Optimization
Optimize existing firing temperature – There are several reasons the firing temperature can be sub-optimal:
- Original design was too conservative
- Changes in unit mass flow
- Changes in unit components
- Fuel changes
- Unit configuration changes
- Tuning changes
Thermodynamic modeling of the unit can identify optimum firing temperatures. It can gain significant MW with only control setting changes. Ultimately, what you are doing is moving the temperature control line based on the outcome of your analysis.
Increase mass flow – This is the most common way to increase output in legacy assets. Increasing mass flow is important for gas turbines because their output is a function of the mass flow through the compressor. As the air temperature goes down, the air gets denser on a base load. Thus, as the temperature goes down, you get more output from the machinery. Options to do this include the following:
- Inlet Fogging
- Inlet Cooling (Evaporative & Refrigeration)
- Wet Compression
- Water / Steam Injection
- Air Injection
- IGV Adjustment (7EA/7FA)
The cost-to-benefit varies with the ambient conditions, access to suitable water/steam and Initial Unit Setup. It depends on what it already available in the environment for the power plant. Optimizing firing temperature when implementing these approaches will further increase output.
Implement peak firing – Most units are designed for a specific firing temperature where you operate base-load and you have a predictable maintenance life and maintenance factor for all components. The goal with peak firing is to increase the firing temperature to result in an increase in output. Features of this upgrade include:
- “Peak” mode is normally selectable as an alternative to “Base” Operation
- Operating in the Peak Range may shorten maintenance intervals
- Firing temperature increase is limited to prevent component damage
- Setting of Peak can be automatic or manual
The benefit of this upgrade is that it is a simple way to take advantage of high spot market prices.
Optimize peak firing – The goal of optimizing peak firing is to take advantage of what an existing unit can do, what the emissions capabilities are, and what the permitting is on your application.
- Units must operate within site permit emissions limits
- Peak firing may cause emissions to exceed limits
- Need to understand what the site permit allows, hourly versus daily/monthly rolling average limits
- Variable peak approach allows operation up to the peak firing value while the unit remains in compliance
- If compliance is not possible at peak firing value, variable peak approach allows maximum firing temperature while maintaining compliance
- CC units with SCR allow for additional optimization and for additional output
The goal is to make assets, especially older assets, more flexible. It improves the ability of the generation fleet to change its output (ramp) rapidly, start and stop with short notice and achieve a low minimum turn-down level. There are two categories for asset flexibility:
- Non-Spinning Reserve: Generation and responsive load that is off-line but can be fully responsive within 30 minutes.
- Supplemental Reserve: Generation and responsive load that is off-line but can be fully responsive within 10 minutes. Premium is available for 10 minute start in many markets.
The chart below gives a general overview of Start up time and loading rates for diesel and motor devices.
Getting to 10 Minutes
There are different strategies for different units, but the following are some of the most common implementations for most units:
Eliminate purge, implement changes to comply with NFPA 85 Purge Credit Standard – After a normal stop, the unit is purged and this purge counts as the purge for the next start, resulting in significant start up time savings. NFPA(R) 85 2015 has specific requirements that must be adhered to in order to establish and maintain the Purge Credit.
Implement Fast Load – Increase the loading rate; a review of the generator capability is required. Load in extended lean-lean and fast transfer to premix (FTP).
Eliminate “Warm-up” delays – Increase the time it takes to start a turbine, effectively eliminating delays for the plant to be available for output.
- On-base device upgrade and rationalization
- Hydraulic/Pneumatic system removal/Fuel system simplification
- Control system upgrade (turbine)
- Excitation/Production system upgrade (electrical)
|Potential Upgrades/Modifications||System Benefit||Drivers/Costs|
|On-Base Device Upgrade and Rationalization||
|Hydraulic/Pneumatic System Removal/Fuel System Simplification||
|Control System Upgrade (Turbine)||
|Excitation/Protection System Upgrade (Electrical)||
TTS Stands with You
While the energy market continues to evolve, we are confident that fossil fuels will stay relevant well into the future for their reliability and accessibility. If you are interested in learning more about how to make your turbine or legacy asset a high-value generation option, talk to our team members at TTS. We are a team of engineers and technicians with over 30 years of experience providing high-value expertise to improve unit reliability and performance. Call us at 407.677.0813 or contact TTS Energy Services.
About the Presenters
Pat Begley, VP Sales
Pat brings over 29 years of gas turbine experience to Turbine Technology Services.
Prior to his current role, Pat was employed by Sermatech Power Solutions serving as Executive Manager of Corporate Sales. In the 1990’s, Pat worked for TTS as Vice President of Corporate Sales and with HSDE Inc. as Manager of Industrial and Marine Business Development.
In his early career with General Electric, Chromalloy, Unitech and HSDE, Pat developed his extensive knowledge of heavy rotating equipment by performing engineering roles including Mechanical Field Service Engineer (GE and Chromalloy), Speedtronic Control System Service/Startup Engineer (GE and Chromalloy), PLC Control System Development Engineer (Unitech) and Controls Group Engineering Manager (HSDE).
Pat was born in Ireland. He earned his Bachelor’s degree in Mechanical Engineering from the University of Dublin and MBA from the University of Houston.
Ricky Morgan, VP Engineering
Ricky brings over 30 years of electrical and controls engineering experience and is responsible for all technical aspects of TTS’ products and services. Prior to joining TTS, Ricky was employed by Sermatech Power Solutions, serving as the International Executive Manager for the Middle East and previously as Vice President of Turbine Systems Engineering.
Ricky was born in Scotland, where he earned his Bachelor’s degree in Electrical and Electronic Engineering from Strathclyde University, Glasgow. More recently, he graduated from the University of Central Florida with his MBA.