Roadmaps to Higher Efficiency

Energy audits for building systems

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We spend a lot of time and ink within the pages of this magazine discussing the latest advances in distributed energy technology. Microturbines and microgrids, electric vehicle energy storage, loadbanks, sound enclosures, solar and wind generation, and combined heat and power are all very interesting topics and vitally important technologies. But we often neglect the most basic element for the success of any distributed energy system—the human element. Not just the human operators of a local grid or distributed energy source, but the one task that can only be performed by humans: the energy audit.

An energy audit is key to the efficient running of a facility’s integrated energy systems. Whether commercial, residential, or industrial, an energy audit can evaluate the current operations of a building’s HVAC (heating, ventilation, and air conditioning), lighting, controls, and communications, computers, escalators and elevators, fire detection, and security systems, refrigeration, electrical power, and water heating systems. After the evaluation, the resultant data can provide the information needed to improve the function and efficiency of these systems. Subsequent audits can evaluate the improvements brought about by these modifications and suggest further upgrades.

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Building Energy Audits 101
Most people usually dread being audited. Financial auditors are a special breed, trained to sniff out any irregularities in the balance sheets of a business or the budget of a governmental office. Energy auditors, by contrast, are not looking for faults—they are looking for improvements. An energy auditor is defined as a specialized consultant who helps improve the energy efficiency of both residential and commercial buildings. They are building inspectors with a focus on energy efficiency. And their main tool is the comprehensive energy audit.

An energy audit is performed to identify areas of avoidable waste and opportunities to save energy. But that is only the direct benefit. Indirect benefits also accrue from an energy audit. These include improved worker health and safety, environmental improvements, and a positive impact on the owner’s bottom-line. Ownership and operating costs can be greatly reduced by more efficient use of available energy, which next to salaries is often a facility owner’s largest single operating cost. Energy audits are both profitable and sustainable.

What are the major boxes that get ticked off during an energy audit? First, they start with the paper trail. This includes an in-depth analysis of the client’s utility bill—investigating utilities’ (electrical and gas) meter readings and bills—and a look at who is using these services (building areas and floors, industrial processes, computer use and server cooling systems, etc.). From this raw data, the auditors can determine average load factors, analyze patterns of demand (time of day, seasonal, etc.) and summarize billing rates and how they have changed over time.

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Next comes a thorough energy survey of the facility. This goes beyond the traditional examination of the building envelope to detect where heating or cooling is escaping and being wasted. It also makes a detailed examination of individual types of energy demands, both light (lighting, HVAC, hot water, refrigeration, computer server cooling) and heavy (industrial equipment and processes). This data is obtained from meters, data loggers, environmental controls (thermostats, fan operations, humidity settings, etc.). Direct heat consumption can be ascertained from the rate of hot water circulation through the building’s radiant heat system as well as the amount of natural gas being flared. Heat consumption is then compared to usable floorspace and room volume to provide a consistent comparison. With a complete set of data, trend curves can be drawn and projections of future use made. And lastly, significant data can be obtained from interviews with management, staff, and system operators. Not only can they provide important information, but they can also give valuable advice and suggestions for improving the facility’s energy systems.

After reviewing documents and performing the physical survey, the energy auditor will move on to diagnostic testing. Basically, this is done to physically track leakage and pinpoint the exact locations where heat and air are escaping. Smoke tracing and infrared camera observations are used to examine the building envelope. Within the building, the auditor will nail down the locations of air leakage from the ductwork, pipes that are leaking air coolant and refrigerant, exhaust fan flow rates, and the energy requirements of auxiliary environmental systems such as fans and cooling coils. Internal furnaces and boilers will be rated for combustion efficiency, carbon monoxide testing, and carbon dioxide pollution. Lastly, energy usage over a typical work day will be measured to determine variable kW draw and kWh usage. All of these use patterns will be compared to weather and climate data, including radiant sunshine throughout the day and ambient outside air temperatures, and the resultant passive heat gain from the surrounding air.

Once all of the footwork is done, the resultant data is organized and collated to produce a report that is intended to achieve four main goals: determine the facility’s baseline for energy use, break out this overall energy consumption into various categories of use, compare the results with similar facilities located in the same region or similar climate, and determine where current energy costs can be cut (and how these cuts can be achieved) without reducing the functionality of the facility.

In simple terms, an energy audit is performed to balance total energy utilization with energy supply. Due to the laws of thermodynamics, no system will ever be 100% efficient. So, energy utilization will always be less than energy supplied to a building. The difference is measured in waste heat and dollars and cents. The results of an energy audit are put to work to minimize both waste heat and wasted money. Not every energy audit strictly follows the patterns described above. In fact, the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) has set the standards for various types of energy audits each with a different focus and level of effort.

The Level 1 Audit involves a simple walk-through of a facility, followed by an analysis that provides a preliminary audit. This is the basic level that provides a broad-brush assessment of energy usage to find the most obvious problems. It includes only a minimum number of basic interviews with facility management and personnel, a simple walkthough of the facility, and a preliminary review of its operating data and utility bills. Its goal is to provide a description of the most obvious problems and recommendations for low-cost/low-effort solutions. These solutions include simple estimates of implementation costs, projections of potential cost savings, and duration of the payback period. It does not possess the same level of detail for a complete plan of action, but it will allow planners to prioritize future efforts and allocate resources.

A Level 2 Audit involves a more in-depth energy survey and detailed analysis. It is the next step after the Level 1 Audit. As such, it utilizes more detailed energy calculations and sophisticated financial analyses. The result is a more accurate and detailed proposal for energy efficiency initiatives. The financial analysis includes an in-depth look at projected life cycle costs with detailed rates of return, payback periods, and projected cash flows. The basis for this is an extensive review of past energy costs with review of utility bills going back as far as 36 months. The proposed plan of action identifies and prioritizes all appropriate energy-saving measures that should be utilized by the facility. Site-specific and system-specific proposals are provided that target specific areas of improvement to provide adequate justification of each proposal.

Lastly, the Level 3 Audit is referred to as a “comprehensive audit” and provides a detailed analysis of energy efficiency issues and equally detailed analysis of capital-intensive modifications. This is the level of audit used to justify major changes in a facility’s operations. It uses the Level 2 analysis as the foundation for a more in-depth report and a more thorough engineering design for the proposed improvements. Matching the detail of the engineering design are the fine-tuned projects for capital costs and anticipated operational savings. This analysis is dynamic in the sense that the various options can be modeled to come up with the optimum mix of proposed energy savings. Load variations and changes in energy consumption throughout the facility operating cycles (work day, seasonal, etc.) are worked into the analysis to provide an even higher level of detail including an examination of why these energy use patterns change over time. Furthermore, this inclusion of variable energy use patterns is applied to each of the facility sub-systems to produce multiple overlapping models of concurrent energy use. In short, it provides a level of detail that allows for both accurate projections and fine-tuning of proposed modifications.

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Implementing the Plan: Achieving Sustainability and the Green Building Certification
General Dwight Eisenhower once said that “Plans are useless, but planning is everything.” That is to say, no plan is perfect or survives in its initial form once it is initiated. But the planning process itself is essential to any further action. The next step is to take the energy efficiency measures (EEMs) described in the audit and put them into action. These should provide detailed instructions as to how they are to be implemented along with projected costs and anticipated savings.

The proposed changes are typically grouped into short-term options (less than a five-year payback period) and long-term options (those with a payback period exceeding five years). Short-term options include: retrofitting and replacement of lighting fixtures, adjusting fans and pumps, changing control systems, installing day light controls, and basic enhancement and repairs. Long-term options include: complete rewiring and lighting and electrical systems, replacement of boilers, and overhaul of HVAC systems.

The facility operator must never lose sight of the fact that an energy audit is a powerful source of sustainability—not just for one building, but for the economy as a whole and the environment itself. The final long-term goal of an energy audit is the award of a Green Building Certification to the facility. This can be either through the United States Green Building Council’s Leadership in Energy and Environmental Design (LEED) program or the United States Environmental Protection Agency’s ENERGY STAR label.

The LEED rating is the most widely used green building evaluation system in the world. LEED provides the framework and standards needed to promote healthy and environmentally sustainable buildings. On a point system ranging from 40 points to over 80, the LEED system awards four levels of certification (certified, silver, gold, and platinum). Rating systems have been developed for a wide variety of facility-related activities: building design and construction (LEED BD+C), interior design and construction (LEED ID+C), building operations and maintenance (LEED O+M), and neighborhood development (LEED ND). These are applied to a wide range of building types, from schools to multifamily midrise apartments, to commercial interiors, and data centers.

A building that has received an ENERGY STAR rating is a facility that has met very stringent energy efficiency and utilization standards as mandated by the US EPA. An ENERGY STAR building has to receive a score of 75 or more (out of a possible 100). This shows that the building is utilizing energy more efficiently than 75% of similar buildings nationwide. To ensure an apples to apples comparison, the ENERGY STAR factors in differences in regional climate, seasonal weather, and operating conditions.

A rated building is compared to other buildings in a group of “peer” buildings nationwide that have the same primary use (office building, factory, commercial school, etc.). Peer data is provided by a quadrennial audit (the Commercial Building Energy Consumption Survey, CBECS) performed by the US EPA which gathers data on building types and energy utilization for thousands of buildings. Data is acquired either directly by the US EPA surveys or provided by certain industry associations for the types of buildings they use (hospitals, retirement homes, universities, etc.).

The rating algorithm actually works the analysis backwards. Given all the data for a building’s characteristics (regional location, occupants, and activities, amount of equipment) the algorithm estimates how much energy a similar building should be using at multiple performance levels between best and worst. The analysis takes into account the source of the building’s energy, weather, property use, and other external factors. Then the US EPA compares a building’s actual energy use with the projected performance levels for buildings of its type. The final result is the building’s energy efficiency rating.

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Energy Audits: Costs Vs. Benefits
The cost of an energy audit depends on multiple factors. Begin with the size and type of facility being audited. The energy utilization of a hospital is going to be different than that of a commercial space, university, or factory. Each has different times of day when demand loads peak, and certain types. Some are open around the clock while others are closed on weekends and holidays. In general, energy demand (and inefficiency) increases with size. Smaller facilities have a more limited and focused energy use profile. A small retail space, smaller than a few hundred square feet, will utilize less electricity for fewer tasks than a large factory spread out over a large area, with heavy electrical load demand for robotics, computers, environmental controls, and material processing, etc.

The level of complexity and the scope of the energy audit determine the level of effort required to carry out the assessment and with it, the cost of the effort. Energy audits can go through several levels of effort, starting with a simple walk-through assessment, followed by detailed financial analyses, and a comprehensive audit with modeling of proposed actions. The scope can be confined to a small business or shop, the office space used by a single tenant, and entire multi-story building or factory, to an entire neighborhood, college campus, or industrial complex.

What is inside the building also counts. This does not include just the number of people working there and how their office space is laid out. At a greater level of detail, the audit can take into account the level of insulation in the walls and ceilings, as well as the design and layout of the building’s electrical, lighting, and HVAC systems, including their existing controls and data management systems. Physical aspects include the building’s shell/envelope and how much energy is lost through cracks, the foundation, windows, and doors. Equipment utilized by the facility can include personal laptops and heavy machinery with assembly lines. Each of these pieces of equipment defines the facilities’ load demand and the timing of that demand. Their layout can result in isolated floor spaces where electrical demand load is heavily concentrated.

The building’s exterior and location also factor into its energy usage. Even paint and stains can prevent infiltration or reflect sunlight, as can the right kind of roofing material. Window size, orientation, and construction (such as high energy efficiency double-paned windows) will either reduce or increase demand load. Outdoor lighting requirements for entryways and adjacent parking lots need to be included in the building demand load. Shade trees and the shade cast by adjacent buildings also serve to reduce exterior heat gain and minimize wind loads on the building envelope.

The file search and interviews needed to establish sufficient documentation can be time-consuming or a simple matter of collating these documents depending on the amount and quality of the tenants’ filing system. Conversely, the level of documentation for the proposed changes to the facility operation can be equally extensive, depending on the level of detail required.

Commercial energy audits, depending on the above factors, could run from $1,000 to $15,000. Follow-up work to track and manage the proposed operational changes can cost tens of thousands of dollars more until completion. However, the operator needs to compare this upfront cost with longer-term cost savings. According to the US DOE, a typical commercial building space has an electrical demand load of 14 kWh per square foot each year. Table 1 provides estimates of electrical and natural gas utilization for different types of commercial buildings.

For example, the annual electrical utilization of a large hospital with a total floor space of 75,000 square feet would use 1,725,000 kWh per year. At an average nationwide cost of $0.12 per kWh, the hospital’s annual electrical bill would run as high as $207,000. An energy audit that discovered a means to reduce electrical demand by 20% would reduce costs by $41,400.

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Major Suppliers
Hubbell Control Solutions, a Hubbell Lighting brand, provides advanced systems and lighting controls combined with an extensive portfolio of solutions for both indoor and outdoor energy usage applications. These solutions are focused on particular energy use systems and provide simple, scalable solutions that integrate seamlessly with other aspects of a facility operation and coordinate smoothly with other Hubbell applications. For example, their advanced lighting control technologies support flexible deployment, intuitive operation, comfort enhancement, improved worker productivity, improved efficiency, and energy savings, all while meeting applicable energy and lighting codes for any size facility. Controlling these applications are control systems that can be either wired or wireless. Physical controls include standard panels and switches, color tuning controls, occupancy sensors, photocell sensors, luminaire integrated sensors, and emergency relays.  BE_bug_web

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