Energy management system controls costs

Scada system evolves with demand to manage and control energy usage across all areas of distributed manufacturing plant.

In order for industry to control energy use and its associated environmental impact, it is first necessary to understand how and when energy is used.

Citect is meeting this requirement with an energy management system that is allowing a major manufacturer with widely distributed site facilities, to both understand and control his energy use.

Based on a CitectScada platform, the total plant energy management system provides not only usage information for each building in the manufacturing facility, but also assists operations managers in controlling energy consumption and costs and contract compliance.

In addition, the system allows plant managers to track greenhouse gas emissions and tie them directly to the energy requirements of specific production facilities.

Developed by Centric Design a Citect Integration Partner (CIP) in the USA, the Scada-based energy management system was first commissioned in 2002 by a major US manufacturing company that required a tool to understand electrical use in multiple buildings on its large manufacturing campus.

The facility has a 13kV distribution system consisting of multiple feeders that provide electricity to multiple buildings.

Most feeders on the system feed multiple transformers, so the building load cannot be determined simply by reading individual feeder loads.

Furthermore, the complexity of the distribution system and the building transformers is such that most building loads could not be defined simply by installing meters on a limited number of connection points.

The client had already chosen an electrical meter manufacturer and was installing its meters at the start of the system project.

This made it necessary that the energy management system provide an open architecture and support for multiple protocols.

The client also required access to the system from multiple locations around the facility so that key personnel to check electrical system conditions in real-time from their daily work locations.

The initial system was designed using CitectScada 5.41.

Communication to I/O devices was achieved through a combination of Ethernet and serial channels.

The system initially connected 20 advanced electrical meters and two electric utility billing meters to the power monitoring system.

The advanced electrical meters were installed on each of the 13kV feeders in the facility's electrical substation and at selected locations around the plant to provide the ability to calculate individual building usage.

The original system design included the following: an active plant electrical system graphic displaying electrical conditions and breaker (switch) status in the facility's electrical substation; electric energy consumption for each building (achieved by adding and subtracting various electric meter kilowatt-hour readings); electric demand for each building (calculated from individual building consumption data); power flow, energy, and demand through the two power transformers that feed the plant; alarms on breaker (switch) status; alarms on high current and low/high voltage around the facility; trending of power and demand for the plant and buildings; tracking electric energy delivered through the electric utility billing meters; and two Internet display clients installed to allow engineering personnel to access system data from various locations in the facility.

As a result of the initial system installation, facilities engineering, operations, and management personnel began to see benefits and identify improvements in operations that would provide additional value.

In 2004, facility energy managers decided to add gas and steam monitoring to the energy system.

The addition was complicated by the desire to use available transducers to minimise installation cost.

Steam lines had flow transducers.

Gas lines had only pulse outputs from the gas utility billing meters.

The client desired to have consumption, demand, and flow data for high and low pressure gas connections and various steam lines feeding the plant.

I/O devices were connected to the various inputs to collect this raw data, which is processed in a PLC to calculate the required consumption, demand, and flow data.

This approach saved the client thousands of dollars, which would have been required for shutdowns and installation of the necessary metering devices to collect the raw data directly.

Changes in the electrical energy market resulted in additions to the system in 2005, when the facility changed its energy supplier.

To improve its ability to stay in compliance with the new energy contract, the facility energy manager decided to make two major changes to the energy system.

First, the system was modified to automatically report energy usage to the energy supplier every fifteen minutes.

Total electric and gas energy consumption for each 15 minute interval is captured.

At the end of each interval, the system automatically connects to the energy supplier's servers via an Internet connection and downloads the consumption data.

For each interval the system reports total imported electric energy, total on-site electric generation, and total gas consumption.

Secondly, the new energy contract had a specified monthly limit in kilowatt-hours.

In order to ensure that the facility does not exceed this limit, the system tracks energy consumption for each day and month to date.

A calendar screen displays the daily and month-to-date energy use and percentage of budget.

The screen also provides visual warning when daily or month-to-date usage is higher than the calculated budget.

Further alterations to the electrical supply contract, in 2007, resulted in changes to the method of operation of two large cogeneration units installed by the company in 2002.

The new contract gave the company the ability to sell generation onto the electrical system.

As a result, the facility needed to be able to track energy into and out of the plant.

To achieve this, the system was modified to gather pulse outputs from the billing meters for energy flow in both directions, rather than only incoming energy.

The system tracks energy in each demand interval and calculates demand and peak demand in each direction.

The usage numbers are tracked monthly and stored to provide a record of energy use and sales.

Also in 2007, facility managers decided that there was a need to integrate additional data into the energy system, from the Wonderware system that was originally installed to monitor and control the cogeneration units; and a Honeywell EBI system that is used for facility management.

The objective of this addition was to replicate selected system views from the external systems inside the energy system.

Successful OPC connections have been installed to both external systems.

The data pulled from the Wonderware system enable plant management to better monitor the conditions of the co-generation facility and the load-shed control system.

As a result of this addition, plant management has identified a problem with the load shed system that prevents it from fully protecting the plant for the loss of the utility feed.

The data pulled from the Honeywell system are used to provide plant floor views of electrical use.

The new views also provide real-time access to electrical conditions at machine tools located throughout the facility.

In 2008, the facility added a new heat-treat furnace.

This furnace is fuelled by natural gas and electricity.

Plant and corporate management desired to track both energy inputs and the results of inputs for the furnace.

As a result, the Citect energy system is now connected to an EIG Shark electrical meter and a Mercury Instruments gas meter.

Data from both meters have been added to the system.

The system collects energy inputs to the furnace and calculates daily and monthly energy use.

In addition to reducing costs and improving energy efficiency, the Citect energy management system also helps the system user pursue a policy of environmental sustainability by tracking greenhouse gas emissions.

In 2008 the first additions to the system were made enabling tracking of the greenhouse gas impacts of electrical consumption and of selected natural gas uses.

These additions allow plant managers to track greenhouse gas emissions and tie them directly to the energy requirements of specific production activities.

The system is designed to track direct Scope 1 emissions, and Scope 2 indirect emissions, providing the company with the facility to meet all future targets regarding greenhouse gas emissions.

This article is a shortened version of a Citect White Paper entitled: "Energy monitoring: a foundation for effective energy management", copies of which can be downloaded from Citect's website.

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