Power generating companies have always relied on the best available information and analysis to optimize operations. What is different today is that rapid advancements in technology make it possible for organizations to take asset management to a new level by fully integrating their data and extending their analytic capabilities as never before.
Jeffrey Williams, Emerson Process Management, USA.
Asset management may be a hot topic in today’s power industry, but it really is not a new concept. Forecasting, lifecycle costing, operations and maintenance planning have always existed with the long-term aim to operate plants with optimal performance, reliability, and cost-effectiveness. To these ends, power generating companies have always relied on the best available information and analysis. What is different today is that rapid advancements in technology now enable organizations to fully integrate their data and extend their analytic capabilities as never before.
The ongoing sophistication of process control technology, including advances in monitoring and control systems and optimization software, as well as the increasing utilization of digital field devices, represents significant opportunities to take the optimization of production assets to new levels. Far from being a luxury, these new capabilities are increasingly necessary to meet the challenges of today’s operating reality in which utilities are expected to satisfy a growing number of stakeholders – from customers and the public to environmental regulators and financial shareholders. Such challenges can also be compounded by the scope of many utility ventures, which can stretch across an entire fleet of plants.
The fleet emissions optimizer
Asset management value
Asset management, as an operating discipline, enables utilities to more effectively deploy limited resources to provide higher levels of customer service and reliability while balancing other obligations such as financial objectives or tightening environmental regulations. This is accomplished by setting criteria tied to these financial, regulatory, service, and operations requirements and leveraging information resources and comprehensive statistical analysis to support value-driven decision making.
The lifecycle of an asset is considered to be the entire span from design and procurement through operation and maintenance and eventual disposal and replacement. The lifecycle of an asset can span decades, so knowledge about the asset – which can include design specs, locations, asset hierarchy, data ownership, change histories, maintenance requirements, connectivity protocols, etc. – can be considered as critical as the asset itself.
Fundamental to any comprehensive asset management effort is an integrated architecture to manage the many system layers, including process automation, plant management and enterprise management. At the process automation and plant management layers, asset optimization, process control and management execution can be delivered through a digital plant architecture that utilizes intelligent field devices, standards and scalable platforms and integrated modular software.
Intelligent field devices give customers immediate access to vital data from plant analysis and measurement instrumentation via the plant’s distributed control system (DCS). This timely access and control of real-time information helps assure both process quality and compliance with environmental regulations.
A next step toward an integrated enterprise-wide information system is to tie in predictive maintenance and optimization applications that ensure critical equipment assets (such as mechanical equipment, electrical systems, process equipment, and instruments and valves) are properly operating through application of advanced monitoring and diagnostic technologies and that resources are optimized for maximum economic results. This information is integrated with other business management information systems, resulting in a single seamless system that gives management the information it needs to make informed decisions.
Of course, optimization efforts are scaleable and can be focused on any or all system layers depending on management’s goals and budgets. It is also important to understand that asset management is an ongoing, dynamic process of continuous improvement and refinement, not merely a means to an end. And because asset management can vary widely in definition, scope, and scale, it is beneficial to understand how improving asset management even in one area can significantly impact an organization’s generating assets and bottom line not only at a single plant, but for an entire fleet of generating facilities. To illustrate this concept, let’s take a look at an area that provides unique challenges and opportunities for power producers – emissions monitoring, control and optimization. We can also provide a case study that demonstrates how a progressive utility Xcel Energy, in a novel application of optimization software, improved environmental compliance and profitability across a fleet of operating facilities.
The overview log on screen
Challenges such as NOx and SO2 compliance have caused power producers to look for ways to help older plants do what once seemed impossible – to simultaneously produce more power, increase profitability and become more environmentally friendly.
Optimization software as part of an overall pollution abatement plan has been shown to not only improve environmental compliance, but also to exhibit a number of financial benefits for users, such as a decrease in overall operating costs, an increase in equipment life span and the ability to make valuable air pollution trading credits available to other power generation assets. The benefits are particularly noteworthy when multiplied across a fleet of operating units, making an emission reduction strategy agreeable to both power producers and environmental interests.
The goal of fleet emissions optimization software is to determine the optimum emission rate for each plant so that the total amount produced does not exceed the yearly cap and that the flue gas is scrubbed in the most cost effective manner. The software can reside on a computer or server located in a central location and should receive key parameters from each of the plants. These parameters should facilitate the calculations for cost of a scrubbed megawatt and provide emissions control system(s) set points that can be sent from the central computer to each of the plant’s control systems to provide operational advice or even closed loop control.
The amount of emissions being produced from each plant can be continuously integrated at the central machine and the predicted yearly amounts will be continuously updated so that the difference between the maximum allowed and the predicted amount can be calculated. The difference is the error that must be continuously compensated for by the optimization software.
The integration of data from dissimilar sources is a key element of this application. The need to account for operating labour costs, additional operating heat rate penalties and maintenance cost factors have a large impact on the ease of integration for fleet-wide emissions strategies.
Facilitating data exchange
Fleet-wide information exchange is possible by linking the DCS system architectures to various islands of automation. The use of “open” interfaces can facilitate this data exchange. This may pose a challenge for older DCS products, but is seamless in more modern renditions of DCS technology. The preferred open interfaces like OPC, NetDDE and Modbus transmitted over an ethernet data network can be supplanted by dedicated links if data sources are less open or if reductions in network traffic are an issue.
The fleet-wide application must gather the plant data, track various costs and calculate the economic trade off between the many relationships and the cost functions. The heat rate penalty of additional parasitic load from scrubbers and selective catalytic reactors (SCRs) must be factored for many measured and unmeasured variables. The fuel type and impact on the need for reagent is a relationship for consideration in the optimization strategy. The non-linear functions of these costs are all challenges for the optimization application. The ability to capture a dynamic real-time heat rate curve for the units and deploy that as the basis for the optimization solution are novel ideas for a fleet emissions optimizer. Linear models can be developed for unmeasured flows and related cost functions that have relationships that follow the generation profile of the plant.
A critical aspect of fleet-wide optimization is the integration of data sources and data collection elements from the business networks down to the control networks and local area plant networks. For this reason, the IT departments at the corporate and plant locations should be involved in the process to allow for the smoothest possible integration.
The plant automation systems and the various PLCs used by subsystem vendors are an additional integration consideration. Upgrade to or development of custom interfaces to these systems to permit communication to a central data server or main automation system can be important for accurate plant models. In some situations, hard wiring sensors to an easily integrated system may prove more cost effective than upgrading older balance-of-plant automation systems.
In what is the first commercial application of fleet-wide optimization using real-time data, Xcel Energy of Denver, installed the SmartProcess Fleet Emissions Optimizer module from Emerson Process Management to optimize SO2 emissions at three Denver area power generation facilities.
The module, which began running in September 2003, is to be used in conjunction with Xcel Energy’s voluntary Metro Emissions Reduction Program for the metropolitan Denver area. Through the installation of additional emission controls at three Xcel Energy power plants (Arapahoe Station, a two-unit, 156 MW, steam electric generating station; Cherokee Station, a four-unit, 717 MW, steam electric generating station; and Valmont Station, which has a single 199 MW steam electric generating unit), Xcel Energy seeks to optimize the SO2 emission rate so that the total amount of SO2 produced by these units does not exceed the yearly cap (10 500 t of SO2 per year), and ensure that the flue gas is scrubbed in the most cost-effective manner. The module installed was designed to determine the optimum SO2 emission rate for the FGD systems at these generating facilities.
The optimization software is further enhanced by the SmartProcess Fleet Emissions Optimizer Portal, which provides a single window into the plants, enabling headquarters emissions managers and plant personnel to remotely view the output of the SO2 optimization programme, plant process graphics and other relevant information.
These menus show key applications and functionality for reports, tracking emissions and optimization etc with what-if analysis
The portal also allows what-if analysis through the browser to determine the cause and effect of fuel variables and scrubber / SCR maintenance activities. Via secure internet access (VPN or virtual private network encryption), designated personnel can see into the plants and monitor the programme on a real-time basis. This is a valuable tool that helps personnel to keep close tabs on SO2 compliance – even when they are off site.
The three Xcel plants are located several miles apart. However, each is connected to the corporate network, making it possible to gather data from each plant and deliver it to a central location. The optimization software receives all of the primary process data from each of the plant’s control systems. The software also evaluates a number of related factors, including data collected from the continuous emission monitoring system located at each plant; the load/outage schedule; coal train and load forecast data; as well as dry reagent, water and waste disposal and maintenance costs associated with the two types of FGD systems used by the units – dry sodium injection and lime spray dryers .
Based on this information, the optimization software sends FGD system setpoints from the central computer to each of the plant’s control systems. The actual amount of SO2 being emitted from each plant and the predicted yearly SO2 amount are constantly updated so that the software can calculate the difference between the two and make the necessary adjustments.
The software responds dynamically to plant operating conditions. For example, if a scrubber goes offline, the software weighs the overall load against the target compliance and costs to determine whether it is necessary to run gas units – and for how long – until the scrubbers go back online.
When modifications have to be made, there are many combinations of actions that can eliminate the error. However, some combinations are better than others. For example, some FGD systems are more efficient than others, while others cost less to operate although they are not as efficient. The goal is to find the solution that satisfies SO2 requirements at minimum cost. While still in its early stages, early indications of the success of the Xcel programme provide the power industry with a compelling case for adopting a fleet-wide approach to managing emissions reductions.
Taking full advantage of today’s advanced technologies can help optimize and manage production assets. The ability to monitor and analyze the fleet performance from anywhere within the corporate infrastructure has many benefits. Remote support from anywhere where an internet connection is available is facilitated via the portal technology. Return on investment occurs in both the short term and long term, and embracing asset management – even on a smaller, targeted level – can deliver operational flexibility, improved reliability, increased operating efficiencies, the ability to meet operations and maintenance budgets and maintain environmental and regulatory compliance.
Furthermore, while incremental increases in efficiency can have a long-term effect on the bottom line, more comprehensive asset management plans can profoundly impact the business as increased efficiencies are multiplied across all assets and the enterprise as a whole is aligned with larger corporate goals and responsibilities. With no end in sight to the industry’s fiscal and operational pressures, power producers would be well served to continue their ongoing pursuit of strategic asset management.