Reaping the Benefits of Energy Efficiency: Part 2

Read part one of Reaping the Benefits of Energy Efficiency

Renewable energy projects

Cemex understands the importance of sustainable development and continually seeks ways to reduce the environmental footprint of its operations. Incorporated in 1906, Cemex is one of the largest building materials suppliers in the world. Cemex produces, distributes and markets cement, ready-mix concrete, aggregates and other building materials to customers in more than 50 countries. Its sustainable operations strategy is based on increasing the use of renewable energy sources, replacing traditional fuels with carbon neutral alternatives, reducing clinker content in cement, and improving energy efficiency in its operations.

Cemex started evaluating the feasibility of developing wind power generation projects at facilities in the US. Subsequently, detailed review of various sites in California and other states were conducted with respect to wind source availability and project economics. Cemex teamed up with Foundation Windpower to develop wind power projects in California. Foundation built, operates, and maintains the wind turbines that supply electricity to three Cemex California facilities.

Cemex utilised incentives available under California’s Self Generation Incentive Programme (SGIP), which provides financial incentives for the installation of new technologies to meet all, or a portion, of the electric energy needs of a facility. The purpose of the SGIP is to create a more reliable electric transmission and distribution system and facilitate reductions in greenhouse gas emissions and utility grid demand by reducing customer electricity purchases.

Energy efficiency projects

Energy surveys and audits are conducted at Cemex plants on a regular basis by corporate technical services and external energy consulting organisations to identify improvement areas and develop projects. Incentives and grants from utilities are considered when undertaking these projects to improve the financial aspects and justification. Two of the many projects undertaken in Cemex US cement plants using utility incentives and the savings achieved are described below.

Variable frequency drive (VFD) project

A large process fan of 2500 hp was running at constant speed with the airflow being controlled by an inlet damper. After detailed investigation, the plant identified that replacement of the damper on this fan by installing a VFD to control airflow would save significant electrical energy. Since the project was capital intensive, Cemex approached the energy efficiency division of the local utility and submitted a proposal for consideration of incentive funds to undertake the project.

After initial review, the utility nominated a third party consultant to conduct independent baseline measurements for power consumption and confirm the potential savings. The utility approved the project and reserved incentive funds based on the predicted demand improvement, energy savings, and estimated project cost. After completion of the project, the plant collected actual data for a period after installation of the VFD and incentive funds were adjusted based on the actual power demand of the fan and actual cost of the project. The plant received about US$500 000 incentive from the utility for this project. In addition to this process fan, the plant also reduced power consumption of the downstream baghouse fan by reducing the pressure drop across the system; the baghouse fan does not have to overcome the damper restriction to get the same flow of gases.

Compressed air project

Cemex identified the importance of replacing old, energy-intensive air compressors with modern high-efficiency systems to reduce energy consumption in their cement plants. Air Demand Analysis (ADA) studies were conducted by a major compressor supplier to identify compressed air demand and supply issues at many of the plants. Projects were developed as a result of the studies to replace all older, less efficient, and maintenance-intensive compressed air systems with new generation efficient compressors, driers, and upgraded control and piping systems.

At one plant, the company replaced an aging compressed air system that consisted of five compressors of varying horsepower operating 24 hours a day and consuming more than 4.5 million kWh annually to meet the plant’s air demand. Five new units now serve the plant’s compressed air needs on a significantly less 2.0 million kWh of electricity annually, for savings of more than 2.5 million kWh each year. In addition to the power cost savings, the plant also reduced maintenance costs as fewer repairs were needed for the new compressors. All with a higher availability of quality compressed air.

This specific plant applied for a rebate from the local utility established under a state law that mandates investor-owned utilities reduce electric power consumption by 22% by 2025. The project was approved by the utility and Cemex qualified for the rebate. Measurement and verification of actual performance was completed by a third party organisation appointed by the utility. After the project savings were confirmed, Cemex received the highest rebate that the utility has ever sanctioned in their territory.

Sources

• US EPA - ENERGY STAR® website, www.energystar.gov/guidelines
• State of California, “2013 Self-Generation Incentive Programme (SGIP) Handbook”, 1 February 2013.

Written by Bhaskar Dusi, Corporate Energy Manager, and Kevin Kelley, VP – Process Technology & Sustainability, Cemex, USA. This is an abridged version of the full article, which appeared in the October 2013 issue of World Cement. Subscribers can view the full article by logging in.

Read the article online at: https://www.worldcement.com/the-americas/25092013/reaping_the_benefits_of_energy_efficiency_part_2_214/