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The energy crisis in the present day world has led us to the design of new energy efficient buildings. However the existing buildings consume a lot of conventional energy and minimizing them will help us to conserve them for future. Moreover it would help us to meet the Energy Efficiency standards.

The capital costs for this conversion would be very high, but lower energy bills over a long period of time would offset them and helps to achieve significant profits for the industry as well as the environment. Energy audit involves the systematic collection and analysis of energy data from a particular facility for implementing energy conservation measures.

An energy audit establishes both where and how energy is being used, and the potential for energy savings. It includes a walk-through survey, a review of energy using systems, analysis of energy use and the preparation of an energy budget, and provides a baseline from which energy consumption can be compared over time. An audit can be conducted by an employee of the organization who has appropriate expertise, or by a specialist energy-auditing firm. An energy audit report also includes recommendations for actions, which will result in energy and cost savings. It should also indicate the costs and savings for each recommended action, and a priority order for implementation.

As per the Energy Conservation Act, 2001, Energy Audit is defined as “the verification, monitoring and analysis of use of energy including submission of technical report containing recommendations for improving energy efficiency with cost benefit analysis and an action plan to reduce energy consumption”.

TYPES OF ENERGY AUDITS

Energy auditing of buildings can range from a short walk-through of the facility to a detailed computer simulation of the analysis. Generally, there are four types of energy audits which are as described below.

1. Walk-Through Audit

This consists of a short onsite visit for the inspection of the facility. By this, simple inexpensive actions can be taken for immediate energy savings. This consists of repairing broken glass windows, lowering the preset temperatures of HVAC systems according to utility, adjusting the boiler-air fuel ratios. This is usually a maintenance procedure done periodically to improve the efficiency of energy systems.

2. Utility Cost Analysis

In this type of audit we carefully analyze the operating cost of the facility. The data obtained over a long period of time energy bills, peak demands, energy use patterns, weather effects are identified. This helps us to establish a relation between cost and utility. Usually this step includes,

  • Checking utility charges and ensuring that no mistakes are made in calculating the monthly energy bills. This is important because the energy rate structures for industrial facilities can be quite complex.
  • Determination of the dominant charges in the energy bills is another part of this analysis. Peak demands take-up a major share of the power consumption cost. Thus for shaving off the peak demand supplemental energy measures can be recommended.
  • Checking whether the facility can benefit from alternative fuels which are more cost effective than the prevailing ones. This will make significant reductions in energy bills. Moreover, the energy auditor can determine whether or not the facility is prime for energy retrofit projects by analyzing the utility data. Indeed, the energy use of the facility can be normalized and compared to indices (for instance, the energy use per unit of floor area for commercial buildings — or per unit of a product for industrial facilities).

3. Standard Energy Audit

The standard audit provides a comprehensive analysis of the energy systems of the facility. In addition to the activities described for the walk-through audit and the utility cost analysis described above, the standard energy audit includes the development of a baseline for the energy use of the facility and the evaluation of the energy savings and the cost effectiveness of appropriately selected energy conservation measures. The step by step approach of the standard energy audit is similar to that of the detailed energy audit, which is described in the following subsection.

Typically, simplified tools are used in the standard energy audit to develop baseline energy models and to predict the energy savings of energy conservation measures. Among these tools are the degree-day methods, and linear regression models. In addition, a simple payback analysis is generally performed to determine the cost-effectiveness of energy conservation measures.

4. Detailed Energy Audit

This is the most comprehensive but also time-consuming energy audit type. Specifically, the detailed energy audits include the use of instruments to measure energy use for the whole building and/or for some energy systems within the building (for instance, by end uses: lighting, office equipment, fans, chiller, etc.). In addition, sophisticated computer simulation programs are typically employed for detailed energy audits to evaluate and recommend energy retrofits for the facility. The techniques available to perform measurements for an energy audit are diverse. During an on-site visit, hand-held and clamp-on instruments can be used to determine the variance of some building parameters such as the indoor air temperature, the luminance level, and the electrical energy use. When long-term measurements are needed, sensors are typically used and are connected to a data acquisition system so measured data can be stored and be remotely accessible. Recently, no intrusive load monitoring (NILM) techniques have been proposed. The NILM technique can determine the real-time energy use of the significant electrical loads in a facility by using only a single set of sensors at the facility service entrance. The minimal effort associated with using the NILM technique compared to the traditional multi metering approach (which requires a separate set of sensors to monitor energy consumption for each end use) makes the NILM a very attractive and inexpensive load-monitoring technique for energy service companies and facility owners. The computer simulation programs used in the detailed energy audit typically provide the energy use distribution by load type (i.e., energy use for lighting, fans, chillers, boilers, etc.). They are often based on dynamic thermal performance of the building energy systems and usually require a high level of engineering expertise and training.

In the detailed energy audit, more rigorous economical evaluation of the energy conservation measures is generally performed. Specifically, the cost-effectiveness of energy retrofits may be determined based on the life-cycle cost (LCC) analysis rather than the simple payback period analysis. LCC analysis takes into account a number of economic parameters such interest, inflation, and tax rates.

Continuation Topics:

  1. GENERAL PROCEDURE FOR A DETAILED ENERGY AUDIT
  2. COMMON ENERGY CONSERVATION MEASURES
  3. NEW TECHNOLOGIES FOR ENERGY SAVINGS IN BUILDINGS

About Gopal MishraVerified

Gopal Mishra is a Civil Engineer from NIT Calicut and has more than 10 years of experience in Civil Engineering and Construction. He is the founder of The Constructor.