The online RCAP Resources Library has a variety of resources that are useful to small, rural drinking water and wastewater systems.
by Scott A. Strahley, P.E., C.E.A.
How can a drinking water or wastewater system in a rural community become more energy-efficient and, at the same time, reduce its operating budget? There are a few quick answers and easy targets in the pursuit to conserve energy. However, as with most changes to procedures, there are caveats and a few potential hazards lurking that you must take into account should you decide to address your energy usage. Here are five areas to focus your efforts on in order to have an effective energy-reduction program.
But before we get to that list: You may be hesitant and a little wary of scams, schemes, and unrealistic projections when energy efficiency is mentioned. Some of these things do exist, and some communities have made poor decisions. However, by understanding your facilities and your energy usage, you can make good decisions and implement positive changes for your community.
1 Understand your current energy use by benchmarking.
Benchmarking is simply determining where you are at the moment. You must first know where you are in order to determine how you will get to where you want to be. How much energy are you using? Where are you using it? What are your costs for energy right now?
You will need to collect and analyze billing information and budget data over a 12- to 24-month period to identify trends and habits. Additionally, you can establish key performance indicators (KPIs), such as: cost per kilowatt-hour; kilowatt-hour per million gallons; cost per hour of street lighting; kilowatts per fixture. These allow for apples-to-apples comparisons with potential alternatives and modifications.
This process can be time-consuming, but there are tools and guides to help you do it yourself. The U.S. Environmental Protection Agency will soon release a free benchmarking tool specifically targeted to rural facilities, so watch for this.
In addition, making your employees aware of the cost of energy in your facilities typically leads to more conscientious and efficient energy behavior, and thus energy reduction and savings. The sharing of information can empower your employees and open the lines of communication.
Teamwork is the cornerstone of every successful project, and energy efficiency is no exception. While there may be hesitation to share billing and account information with the field crews and operators, this cooperation between the office and the field can reap rewards for the bottom line.
2 Shed light on your technology and location of fixtures.
By now most of us are aware of new lighting technologies, including compact fluorescent lights (CFLs), light-emitting diodes (LED), and halogen. There is legislation to discontinue the manufacturing of some incandescent light bulbs, with 100-watt bulbs ceasing on Jan. 1, 2012, 75-watt bulbs ceasing on Jan. 1, 2013, and 60-watt bulbs ceasing on Jan. 1, 2014.
You can address replacing incandescent bulbs in your facilities. They can be replaced all at once or as they burn out. Pay special attention to the lumen output and the correlated color temperature (CCT) for your replacement bulbs to assure a good quality of light. Also, CFL bulbs contain small amounts of mercury, so in the event of a breakage, there are safe cleanup and disposal procedures to follow.
On a similar scale, every facility should address the replacement of older, overhead 4-foot T-12 fluorescent fixtures (magnetic ballast and bulbs) with more efficient technology, such as T-8, T-5, or even LED. Legislation has stopped the manufacture of the energy-hungry magnetic ballasts as of July 2010, although they may still be for sale. Replace these with the more efficient electronic ballast that can save more than 20 percent of the energy used.
Moreover, current legislation calls for the popular T-12 fluorescent bulbs to no longer be manufactured beyond 2015. Each system will need to address its lighting needs to suit its planning goals.
Another easy lighting step is to replace incandescent exit signs with LED exit signs, which will lead to consistent savings due to their 24-hour operation. A typical incandescent exit sign uses approximately 30 watts, while an LED exit sign uses only about 2 watts. There are simple and inexpensive conversion kits for around $15 to help make the change.
Most communities have exterior lighting for their buildings, parking lots, sidewalks, and streets. There are retrofit fixtures and bulbs to reduce the energy consumption of most types of fixtures. It is important to note that lights are designed to illuminate the roadways, crosswalks, and other important areas, and they cast their light in a controlled, designed pattern. Deviation from this design may affect the illuminated areas (create dark spots), potentially putting pedestrians, vehicles, or other items in harm’s way. Be sure to not decrease safety or security while trying to decreasing energy consumption.
And, lastly, you can install lighting controls, including motion sensors, light sensors, or even simple timers. The savings comes from using fewer kilowatt-hours for shorter periods of time. Identify the proper control for the right space to assure effective usage. There was a case of a motion sensor that was installed in a restroom, and a user got stranded while sitting in the stall as the sensor could not detect any motion. Be sure to consider potentially embarrassing or impractical situations like this!
3 HVAC: What is comfort?
Heating, ventilation, and air conditioning serve many roles, including: climate control for comfort, humidity control for equipment and personnel, and air quality for safety and the work environment. You must take these functions into account before you modify settings or working parameters.
Potential energy-saving opportunities include adjusting the thermostat slightly during working hours and adjusting the thermostat significantly during non-working hours. A rule of thumb is that by adjusting the thermostat 10 degrees for 10 hours, it is possible to save up to 10 percent of your energy use. It is important to respect the comfort levels of your employees who work inside. Proposed temperature changes can affect their attitudes and level of satisfaction with the workplace, and those are a few heating or cooling dollars worth spending.
An important physical aspect of HVAC controls and operations includes the building envelope, the building orientation, and the existing equipment. A dark roof or structure will absorb more heat than lighter-colored ones. Windows allow for higher heat transfer than solid walls. Focus on proper insulation, minimizing structural air gaps, addressing the use of doors and windows, providing regular service and maintenance of the filters and equipment, and even the replacement with more efficient equipment. These will all help to manage the HVAC system efficiency.
HVAC opportunities typically have very long paybacks, even with utility company incentives. It is important to understand the full scale of the proposed work. You should evaluate whether immediate action, or possibly waiting until equipment fails, is the most prudent and economical path forward.
4 Water production: The cost for clean water
Whether you have a groundwater or surface water system, the treatment processes are relatively similar. You treat the water, store it, and then distribute it. Your water-production facilities are full of capital-intensive assets, from the clear well, to the storage tank, and including the pipe network and appurtenances.
The largest energy users in these systems are the pumps, accounting for approximately 85 percent of the costs. You can replace pumps with higher-efficiency models or use combinations of pumps to better meet the actual pumping volumes. It is also important to address your system pressure, your time of use, check for throttled valves, consider variable speed drives, and to review your controls. Ohio RCAP has identified potential water system cost reductions ranging from 20 to 70 percent with an average of 1-year simple payback for communities through energy audits.
Brand new water systems are tested and allowed to have minimal leakage. As time passes, these leaks, and potentially new leaks, can and do become larger, and water loss increases in the system. A community should track and understand how these losses impact the design and operation of their water facility. It may be more prudent to address water loss rather than upgrading and increasing the water treatment pumps and tanks. Water quality is paramount and cannot be compromised to save a few dollars.
5 Wastewater treatment: Energy to eliminate waste
There are many different types of wastewater treatment plants and designs, and typically the largest energy users in a system are the pumps and aeration systems. It is critical to first understand the operations and the design of the pumping system before any changes are recommended or implemented. It is very common for pumping systems to be very inefficient, so the potential for savings is most likely present.
Significant modifications may require regulatory review and may need professional design as well. Ohio RCAP has identified potential energy-cost reductions ranging from 6 to 62 percent, with an average of less than 1-year simple payback for communities through energy audits.
Other opportunities for energy savings in wastewater treatment are in solids management and also include the use of variable-speed drives and automated controls.
The area that is most likely to result in significant savings is the overall operations of the facility. While most rural wastewater systems are overdesigned and under-performing, it is important to understand why these conditions exist. Some communities anticipated growth and have instead experienced a population and industry reduction. Keep in mind that systems are designed for peak flow conditions, so the typical daily operating condition is not the design parameter to drive your modifications. It is also very important to maintain permit and discharge requirements along with operations and process constraints.
Conclusion of this article but only the beginning of your process
It is important to note that this list and article are only tips and suggestions and by their nature are not meant to be comprehensive or an exhaustive process for evaluating the potential energy savings in your system. This article is mainly to give you areas to start considering in a longer, more systematized process. The best way to become educated and initiate this process is to start with an energy audit.
There are many sources for audits, along with a variety of costs. You are encouraged to explore the options for energy audits and evaluate the auditor’s experience and qualifications. Pay particular attention to any contract-related requirements for your community that may follow the audit. You should also compare not only the potential for savings but also the cost of changes, the payback period, the possible funding mechanisms, the potential for financial incentives, and the urgency of the proposal.
Contact the RCAP field staff member in your state for assistance with these options and opportunities. Find him or her at www.rcap.org/regions.
Strahley is an engineer for Ohio RCAP, which is part of the Great Lakes RCAP.