Is it Time for an Energy Audit?

March 14, 2007

About the author: Patrick Clifford is a senior associate at CTE Engineers. He can be reached at 312/373-6669 or by e-mail at [email protected].

After all, electricity is an inherent element of the process of treating water and wastewater. The electric costs that these water and wastewater facilities incur are a significant portion of their annual operating budgets. Water and wastewater treatment plants are using more electricity than ever, due to demands for increased service and new regulations for upgraded treatment. Increases in these electrical costs will have significant budgetary consequences for these facilities.

It is estimated that the energy consumption at water and wastewater facilities will grow by over 20% over the next 15 years.

New solutions

The electric utility generation and transmission markets have experienced various challenges over recent years, such as deregulation, increases in power usage, aging and deteriorating infrastructures and large scale power outages.

Traditionally, capital has been invested into building or improving upon generation and transmission facilities to address the aging and growth issues. However, this traditional model does not seem to be effective in this new environment and new solutions are being presented.

In an effort to reduce energy consumption, increase power grid reliability, and reduce costs, several progressive electrical utilities have implemented energy management programs. Energy management is a broad term used to describe various energy monitoring and conservation techniques that can include power metering, renewable energies, load reduction equipment, peak shaving, power quality, or other solutions that can lead to positive long-term power system improvements.

Energy management at wastewater facilities can reduce costs, improve equipment operations and increase system reliability, with the ultimate goal of providing cost-effective treatment service to your customers.

Large-scale initiatives are currently being successfully implemented in New York and California, with the goal of identifying the need for energy management at water and wastewater facilities, recommending areas for energy management improvements, providing funding for improvements and overseeing the completion of the improvements. The level of energy savings can vary significantly from facility to facility, but some have reported usage savings exceeding 25% annually.

In addition to energy savings, water and wastewater utilities greatly benefit by receiving new or upgraded equipment.

Programs similar to these turnkey solutions on the east and west coasts will soon make their way to other parts of the country and will work in conjunction with some of the existing programs. Education about the benefits and success stories associated with these types of programs is important in order for additional funding to be made available.

Opportunities abound

One reason that these energy management programs have been successful at water and wastewater facilities is because there were great opportunities for energy savings.

In order to successfully reduce energy consumption at water and wastewater facilities, it must first be understood where the energy is being used. It is very easy for a wastewater treatment plant to determine that a majority of their electrical usage is a result of their blowers and pumping (approximately 65%). At a water treatment plant, the most usage goes to pumping (approximately 85%).

However, in order to really understand how the facility is operating the next few layers of energy consumption must be exposed.

One of the most economical ways to understand a facility’s energy consumption and to investigate the potential for energy optimization is to conduct a needs assessment or an energy audit.

An energy audit is a good tool to identify opportunities for improving plant efficiency and reducing operating costs. Someone who is experienced in treatment plant design and energy management strategies should perform the audit. It usually consists of a one- or two-day visit to the facility to determine how, where, and how much energy is being consumed. Each unit process should be analyzed for cost-saving opportunities, and utility rate schedules should be evaluated.

The following are some typical energy management opportunities at water and wastewater facilities:

  • Variable frequency controllers;
  • Peak shaving/load shedding;
  • Aeration controls;
  • Solids handling/hauling;
  • Operational considerations;
  • Renewable fuel sources;
  • Cogeneration;
  • Lighting controls;
  • Power management software and SCADA; and
  • HVAC and other non-process related improvements.

Other simpler and less expensive solutions should also be looked at as part of the audit—for example, operational modifications, fixing broken or leaky piping, or modifying/renegotiating electric rate schedules. The energy audit will typically develop a long list of energy savings opportunities that are specific to the facility, with some preliminary capital costs and potential energy savings.

As a follow-up to the initial audit, a more detailed feasibility study can be performed to further evaluate all or some of the potential energy savings opportunities:

  • Overall facility history and capacities;
  • Utility rate information;
  • Operational descriptions;
  • Creation of optimal operational procedures;
  • Comparison of energy use to the billing structures to determine possible savings through better use of off-peak loading;
  • System improvements and their costs;
  • Constructability;
  • Computations of payback periods for recommended changes; and
  • Identification of funding needs as well as funding opportunities.

The feasibility study is a valuable decision-making tool for plant improvement options. The results from the study will help make “go/no-go” decisions based on the availability of paybacks from each improvement. Sometimes exceptional paybacks associated with one or more of the proposed improvements can help offset the poorer paybacks on the rest of the projects.

Finally, the feasibility study can be used as a gateway to the detailed design in order to gain approvals from boards or authorities, secure funding, or act as a preliminary design.

Beneficial processes

Needs assessments, energy audits and feasibility studies can be extremely beneficial processes to a facility and are typically performed as milestone projects. In other words, they are not performed on an annual or biannual basis, but either once every 10 to 15 years or as major plant improvements or additions are implemented. Therefore, in order to get a handle on the energy usage of a facility on on a daily basis, facilities can use another tool called benchmarking.

Benchmarking is the process of looking at your water or wastewater facility and comparing it to energy use averages at similar plants (size and type) across the country. The information from these facilities is gathered, consolidated, and published by a few different organizations and is easily obtainable on the Internet.

Typically, the information is broken down by overall plant load and critical plant processes. The benchmarking process is something that can be ongoing and easily integrated through an existing plant SCADA system, energy management system, or even a simple manual data gathering. The benchmarking process allows a facility’s personnel to get a better handle on the plant as a whole, as well as the individual plant processes, and compare that information with similar plants in order to determine how efficient the facility is operating. The results could indicate that the plant is operating extremely efficiently and there are no further energy optimization opportunities or, conversely, that the plant is extremely inefficient. In this case it may be a good idea to perform an energy audit.

In addition, benchmarking is a good tool to notify personnel that some condition in the plant has suddenly changed or that the plant is operating unusually.

The opportunity for energy management in the water and wastewater industry is real. The current condition of the electric utility market, compounded with increases in energy prices, will put strain on water and wastewater operations and financial budgets.

The energy management techniques described above are valid methods of better understanding where energy is being used, how much it is costing a facility and what improvements can be made in order to optimize the facility and its energy usage.

About the Author

Patrick Clifford