Effective Energy Management

Introduction

An effective energy management strategy includes.

  • Developing a baseline of current energy use practices
  • Identifying, quantifying, and prioritizing energy saving opportunities
  • Measurement and benchmarking

These components are discussed in the sections that follow.

Developing an Energy-Use Baseline

Understanding and documenting current energy use patterns is called developing a baseline. The components of an effectiveenergy-use baseline are:

  • Utility analysis
  • Plant energy balance
  • Lean energy analysis

Utility analysis refers to understanding how energy entering the plant is measured, how the cost of energy is determined, and how energy use and costs have changed over time. A plant energy balance quantifies how much energy is used by equipment and processes within the plant. Lean energy analysis looks at the statistical relationship between energy use, production and weather to determine drivers of energy use. Taken together, a utility analyis, plant energy balance and lean energy analysis provide a thorough understanding of current energy use.

Utility Analysis

Most facilities purchase electricity and fuel. The baselining process begins by understanding how:

  • The energy entering a plant is measured
  • The total cost of energy is determined
  • Energy use and costs have changed over time.

It is important to perform a utility analysis for each type of energy used by the plant, i.e. electricity, natural gas, coal, etc.

Plant Energy Balance

Accurate utility and lean energy analyses are the precursors to a total plant energy balance. The total plant energy balance tracks energy as it enters the plant, is converted into useful forms, and used in processes and operations. Thus, the plant energy balance has three components:

  • Energy supply
  • Energy conversion
  • Energy use

Energy supply is determined from the utility analysis. All electrical and fuel energy entering a plant is then converted to into other forms of energy by lights, boilers, air compressors, etc. In the energy conversion section of the energy balance, the energy supply is disaggregated into the primary energy conversion equipment. Converted energy is then delivered to processes and operations. In the energy end-use section of the energy balance, the energy is disaggregated into principal end uses.

The resulting whole plant energy balance:

  • Provides a clear understanding of the energy transformation from supply to conversion to end use within a plant.
  • Focuses attention on the most promising areas for reducing energy use
  • Improves calibration of equipment energy use models to increase accuracy of savings estimates.

Carbon dioxide emissions from energy use are proportional to energy use. CO2 emissions from electricity use depend on the fuel mix and efficiency of the electric utility. CO2 emissions from the combustion of fuel can be calculated from combustion equations.

Lean Energy Analysis

Lean energy analysis (LEA) is a technique for accurately quantifying how much energy is used for production, space conditioning, and general support activities. LEA uses statistical and graphical analysis of energy, weather and production data to make these determinations. The technique is called lean energy analysis because of its synergy with the principles of lean manufacturing. In lean manufacturing, “any activity that does not add value to the product is waste”. Similarly, any energy that does not add value to a product or the facility is also waste.

The statistical LEA models disaggregate electricity and fuel use into the following components:

  • Weather-dependent energy use
  • Production-dependent energy use
  • Independent energy use

Thus, LEA quickly quantifies how much energy adds value to the product and facility, and how much is waste. LEA provides direct insight to the minimum energy requirements and the steps required to improve overall energy efficiency. This quick but accurate disaggregation of energy use:

  • Improves calibration of energy use models with utility billing data
  • Focuses attention on the most promising areas for reducing energy use
  • Accurately quantifies the energy not adding value to product or the facility
  • Provides an accurate baseline for measuring the effectiveness of energy management efforts over time.

Summary

In summary, developing a baseline:

  • Helps define potential energy savings
  • Helps focuses efforts on the most important areas
  • Determines accurate avoided energy costs for calculating cost savings
  • Helps identify energy saving opportunities
  • Provides a baseline from which to measure the effectiveness of energy management activities.

Identifying, Quantifying and Prioritizing Energy Saving Opportunities

Developing an energy baseline provides a foundation for identifying, quantifying and prioritizing energy saving opportunities. However, because of the diversity and complexity of products and manufacturing processes, the process of identifying, quantifying and prioritizing energy saving opportunities can seem overwhelming. Even when a few energy saving opportunities are identified, the lack of a systematic approach can still result in a feeling that many opportunities were missed. This hit or miss approach can be minimized by understanding plant energy use in terms of primary energy systems and using an inside-out approach to identifying energy saving opportunities within each system.

Energy Systems

Although every product and manufacturing facility is different, plant energy use can be understood in terms of a few primary energy-delivery systems. The principal energy using systems are:

  • Lighting
  • Motor drive
  • Fluid flow
  • Compressed air
  • Steam
  • Process heat
  • Process cooling
  • Heating, ventilating and air conditioning
  • Combined heat and power

Virtually all energy conversion equipment falls within one of these systems. Thus, a practical, yet comprehensive, way to analyze energy saving opportunities is on a system basis.

These systems are sufficiently independent that many energy saving opportunities can be identified by considering a system independently of other systems. However, interaction effects between systems do exist, and a whole class of energy saving opportunities can be identified by considering these interactions. For example, optimal heat exchanger placement can simultaneously reduce both heating and cooling loads. Reducing electric lighting, fluid flow friction or process heat loss simultaneously reduces cooling loads. In combined heat and power systems, both power and heat can be generated more efficiently that purchasing these forms of energy independently. Thus, the best analyses are aware of interaction effects between systems and purposely seek to maximize benefits from these interactions.

Principles of Energy Efficiency

The systems approach described above is an effective way to organize energy efficiency efforts. However, certain principles of energy efficiency apply to multiple systems. These principles include:

  • Inside Out Analysis
  • Minimum Theoretical Energy
  • Conversion and Control Efficiency
  • Match Source Energy to End Use
  • Maximize Counter-flow
  • Avoid Mixing
  • Whole-system, Whole-time Frame Analysis

Integrated Systems + Principles Approach

The integrated systems + principles approach (ISPA) is a combination of the systems and principles of energy efficiency approaches. Applying the systems approach is conjunction with energy efficiency principles creates an integrated energy assessment that is both thorough and effective.

Quantifying Energy Saving Opportunities

Engineering analysis is typically employed to calculate or estimate projected energy savings. Common sources of this engineering expertise are:

–Equipment vendors (compressed air, boiler, etc.)

–Energy savings performance contractor (ESPC)

–Independent energy audit

Equipment vendors often have detailed knowledge of their equipment can provide a quote for the project cost. However, equipment vendors have a direct interest in selling their equipment, and that interest may influence their estimates and judgments. Energy savings performance contractors (ESPC)can finance energy efficiency projects and structure the payments to be in line with expected energy cost savings. In addition, some ESPCs will also measure pre and post-retrofit energy use and guarantee that the project delivers the expected savings. These benefits are often very attractive to firms that find it difficult to obtain funding for an energy efficiency project through the in-house capital budget, or that seek assurance that the project will perform as expected. However,the ESPC is essentially charging for this financing option and the “insurance” of guaranteed savings. Thus, direct financing may improve the overall cost effectiveness of a project. Independent energy auditors are typically not influenced by the desire to sell equipment or financing; however, independent energy auditors must eventually rely on vendors for cost estimates and system design, and cannot typically provide financing or guaranteed savings.

Prioritizing Energy Saving Opportunities

Most companies use multiple filters to prioritize energy saving opportunities. These filters include:

  • Financial return on investment
  • Rank versus other energy saving opportunities
  • Rank versus other requests for capital
  • Risk
  • Consistent with other priorities
  • Available and knowledgeable staff to manage project

Implement Savings Opportunities

Implementing savings opportunities requires commitment for management, maintenance personnel and equipment operators. Effective communication about the benefits and requirements of the project is essential to this shared commitment.

Sustaining Energy Efficiency Efforts through Measurement and Benchmarking

Sustaining energy efficiency efforts over time requires that the effectiveness of past efforts be accurately evaluated. Accurate measurement of energy savings informs the selection of future energy efficiency initiatives and can help determine appropriate budgets for future initiatives.

The simplest way to measure savings is to simply compare energy use from before and after an energy saving project. However, in most cases, the energy drivers of weather and levels of production have changed between the pre and post-project periods. Thus, direct comparison of pre and post-project energy use is likely to measure changes in weather and levels of production as much as the success of the energy efficiency project.

To properly account for these changes, an equation of energy use during the baseline period as a function of energy use drivers such as weather and production should be developed. This baseline model can then be adjusted to determine how much energy would have been consumed before the project under current weather conditions and levels of production. Savings can then be measured as the difference between the adjusted baseline model and post-retrofit energy use. This method is called ‘past-performance bench marking’.

In addition to past-performance benchmarking, comparing energy use between similar facilities can also identify energy efficiency opportunities and develop targets for future efforts. As with measuring savings, multi-facility benchmarking requires that differences in weather and levels of production between facilities be adjusted using baseline models.

Together, measurement and benchmarking using energy baseline models:

  • Verify the performance of past energy-efficiency efforts
  • Inform the selection of future energy-efficiency initiatives
  • Help develop energy-efficiency targets

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