Soteica Visual Mesa MES solution for Thermal Power Plants

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The following text was written by Bulat Nizameev of Yokogawa Advanced Solutions and Diego Ruiz of Soteica VisualMesa earlier this year.

In writing this article, it is my intention to explain the challenges and potential solutions to gain efficiency in thermal power plants (TPP) around the world. The following text is meant to serve as a short introduction to the problems in optimal load distribution and optimal planning modes/structures of equipment; explain operational monitoring of key performance indicators, and also give suggestions on how to avoid penalties by minimizing excess emissions (CO2, SO2, NOx).

Improving efficiency and increasing contribution margin from the production and sale of heat and electric power are among the main objectives in this particular TPP example, and these goals can be achieved by solving the issues stated in the previous paragraph. Currently, the solution for such issues is not possible without the use of modern computer techniques and information technologies that can be attributed to systems-level MES (Manufacturing Executive System), and Soteica Visual Mesa offers a compelling solution.

Fig.1.  Steam System Example

The basis of Visual MESA serves as an integrated model of all energy flows. In addition to energy units, the system considers money equivalents of energy flows, which is a necessary condition for the solution of problems of minimizing energy costs and maximizing profit from the sale of thermal and electric energy. The system has an intuitive environment for adjustment, maintenance, and modernization of the design decisions of the system through the built-in library of pre-configured functional blocks and with a graphical way to organize data flows between functional units by means of communication lines (Fig. 1.), which also contain thermodynamic and energy characteristics of the process streams (pressure, temperature, enthalpy, calorific value, heat capacity, etc).

Visual MESA allows us to obtain the results of the optimization of the distribution of thermal and electrical loads, the planning and configuration of the power equipment with the aim to obtain the maximum profit from the sale of heat and electric energy that is capacity based on forecast data for the price of electric energy and heat consumption requirements of wholesale planning regimes, and the composition of the equipment for a few days ahead with the possibility of operational adjustments. Also additional constraints on emissions (the single integrated model can account for and calculated emissions of CO2, SO2, NOx based on the stoichiometry of combustion and correlations), contract penalties and restrictions (e.g., strict selection of the natural gas in equal parts), and technological limitations (e.g., minimum downtime of the boiler, the simultaneous start-up of equipment, etc).

I believe that Visual MESA provides the most accurate optimization solution in the energy sector, which can be configured specifically for use with the systems that generate steam and electricity. Unlike most software available on the market, Visual MESA allows us to solve problems in large-scale system modeling and optimization.

Visual MESA provides its customers with the following key features:

  1. Monitoring
  2. Audit
  3. Accounting
  4. Calculation of key performance indicators
  5. Operational reports
  6. Optimization and planning

Although Visual MESA is applicable for almost all industries, Visual MESA specifically for TPP contains a combination of two sets of functional licenses:

  • Visual MESA ERTO Open Loop (energy real-time optimization) with recommendations for optimal use in a report)
  • Visual MESA-MPO (multi-period optimization for optimal planning of equipment configuration to time limits, e.g. maximum or minimum uptime). This module operates offline.

The description of these modules is presented below.

Visual MESA- ERTO

Visual MESA is a Real-Time On-Line Optimizer which we also refer to as “Energy Watchdog.”

At a certain frequency, for example every 15 or 30 minutes, Visual MESA retrieves real-time plant measurements as well as utilities prices and emissions regulations. It then calculates and finds the optimal way to rebalance the utilities loads within the site so that the overall energy bill is at its lowest possible value. Visual MESA does this within operational, contractual and, more importantly, environmental constraints.

 

Fig.2 Visual MESA structure

 

In open-loop mode, Visual MESA produces MS-Excel based reports indicating the actions that need to be taken to capture optimization savings. These reports are also exported in html format so that they can be accessed by the operators via a browser from the server. In closed-loop mode Visual MESA sends the changes in setpoints directly to the corresponding DCS.

Visual MESA- MPO

Fig. 3. Structure of Visual MESA-MPO

Visual MESA Energy Multi-Period Optimizer allows scheduling engineers and operators to find the optimal operation of the utility plants on a time horizon when dealing with time dependent constraints. These constraints are often related to fuel tank farms, thermal energy storages, minimum/maximum start/stop time of equipment, and planned out-of-service periods. As part of the Visual MESA Solution, VM-EMPO shares the same model environment and look and feel of VM-ERTO and VM-EM. This greatly facilitates the user experience and eliminates the need of multi-model maintenance and extra training effort.

  • Forecast: For planning and developing the optimal schedule of the equipment for a certain time in advance it is necessary to have forecast values of some parameters (e.g., electricity prices, steam demand, ambient temperature). Visual MESA MPO uses these forecasts to develop an optimal operating schedule of equipment to minimize energy cost. It is assumed that the forecast data should be provided by the customer.
  • Visual MESA model: To be able to develop an optimal schedule of the required accurate model of the energy system. Visual MESA provides a convenient framework for representing such models.
  • VM-MPO: VM-MPO is the core of the system that built into Visual MESA model environment. Multi-period restrictions can be customized with a user-friendly interface (constraints, time-varying) in conjunction with the site model and forecast data. Examples of multi-period constraints are represented in the tables below:

Single Unit Constraints Description
(ONOFF): On/Off Constraints Constraint allows the user to force a unit on or off at any time in the schedule
(MAX/MINOP): Max/Min Total Time Operation Constraints Constraint allows the user to limit the total time a unit should work
(MINUT): Min Up Time Operation Constraints Constraint allows the user to ensure a unit is not turned off unless it has operated a reasonable amount of time
(MINDT): Min Down Time Operation Constraints Constraint allows the user to ensure a unit is not turned back on unless a reasonable resting time has passed

Multi Unit Constraints Description
(CONAC): Conditional Active Constraints Constraint allows the user to define the on-off state of a unit based on the on-off state of another unit
(SIMSS): Simultaneous Start-Up Constraints Constraint allows the user to ensure a unit starts when another unit starts
(PRECE): Delayed Start-Up Constraints Constraint allows the user to ensure a unit starts after another unit starts plus a predefined delay

The procedure for designing the optimal schedule consists of 5 main steps:

Fig. 4. Multi-periodic reports-trends

  1. Calibrate the energy system model
  2. Select forecasted prices and power/steam demand;
  3. Run the optimization
  4. Review and analyze the results: tables, graphs, Gantt charts (Fig. 4)
  5. Adjust data/constraints and run again, if necessary

Economic Benefits

The primary economic effect in the implementation of Visual MESA is achieved by implementing the following functions of Visual MESA:

1. Optimization of the distribution of energy flows

  • Operation optimization of loads of parallel running equipment (boilers, turbines)
  • Choice of the cheapest energy source taking into account production, environmental, and contractual constraint

2. Optimal planning and scheduling

3. Leveraging utilities auditing and accounting features to detect and eliminate the wasted steam

  • Identification of wasted steam and various operating problems
  • Alerting for changes by periodic scan of all the flow meters inside the model and warning of any changes that occur which exceed a pre-defined thresholds.

4. Emissions management and monitoring

  • NOx and SOx constraints
  • CO2 trading (according to Kyoto protocol)
  • Equipment performance monitoring
  • Utilities planning and scheduling

5. Evaluate effect of production plans on utilities system

6. Planning of Shutdowns

7. Export Nominations

8. Investment planning and basic engineering

  • Plant expansion, process change
  • Change of configuration of the energy system (e.g. a new co-generation unit)‏

9. Soft cost savings can be found through allowing the entire organization:

  • To access the site-wide energy system through one model and one environment
  • Visibility to all the decision variables and associated constraints (which are sometimes hidden or ignored)
  • Centralize responsibilities for system optimally.

In addition to direct benefits from the introduction of Visual MESA and new approaches to monitoring energy efficiency, TPPs will receive a number of additional advantages:

  • The possibility of convenient analysis of the operation of energy systems in real time, the availability of direct access to the indicators of the entire energy system of site from a unified model and a unified environment
  • Ability to monitor all process variables and related constraints, which in some cases may not appear or be ignored
  • Active involvement in the process the operators of units due to the centralization and personalization of responsibility for energy efficiency of the process, which is made possible by the creation of a single robust information system that will allow operators to understand the challenges they face, deciding that they will provide a minimum level of power consumption.

Conclusion

The economic benefits from implementation of Visual MESA are estimated to be in the range of a 1-5% increase in marginal power plants. Thus, the implementation of MES technology for is an important tool for solving problems in maximizing the marginal profit of TPPs, optimizing and improving operational processes in the planning regimes and the composition of power equipment within the requirements of energy and environmental management.

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Read a blog by Visual Mesa expert Dr. Carlos Ruis, here.