"Low-Tech/No-Cost" Control Strategies to Save Energy in K-12 Schools.
The Center for Energy Research and Technology, (C.E.R.T.) located on the campus of North Carolina A&T State University performs energy audits and assessments for facilities in North Carolina. C.E.R.T. focuses on outreach and extension activities and education relating to renewable energy energy efficiency alternative fuels and vehicle technologies sustainable green building and the environment. C.E.R.T. is funded through a grant from the NC State Energy Office (NCSEO), and most activities focus on K-12 energy awareness, conferences, fairs and expositions, workshops and audits/assessments. Through the different levels of energy audits, many good investment opportunities have been discovered that can achieve payback return on investment (ROI), in as little as one-month to under two-years, but we will only focus on the "low-tech/no-cost" strategies that should be implemented immediately to start saving money. "Nocost" signifies that no capital expenditures are needed; however maintenance employees' time is required to implement these strategies Energy costs are the largest operating expense for school districts after salaries and benefits. America's schools spend more than $75 billion annually on energy, more than they spend on textbooks and computers combined and in recent years those costs have increasingly strained their budgets (USEPA, 2008)
An energy audit or assessment is a "snapshot" in the life of a building that systematically investigates methods to advance and optimize a building's operation and maintenance. The process focuses on the energy utilized by the building's mechanical and electrical equipment such as HVAC, lighting and controls The objective of an energy audit is to analyze the energy usage in a facility, while identifying potential problems and opportunities for energy and cost savings. Using the information gathered the auditor may suggest the implementation of pertinent and cost effective energy conservation measures (ECM) for the building. The audit involves obtaining equipment documentation and its operation through a site visit. The facility's staff and operating schedules are interviewed and recorded. If further information is required, systems can be monitored with data loggers to graphically visualize the operation, and gain actual data to statistically create informed energy savings decisions. Energy savings approximations are calculated for the important discoveries where sufficient data was available.
Commissioning existing buildings can reduce energy costs up to 20%. The payback for investment in low cost opportunities typically ranges from a few months to two years. The energy assessment process involves a coordinated effort between C.E.R.T. and the building operating staff. The standard information collected is:
1 The building's age (including any renovations and additions)
2 A description of the typical areas or spaces within the facility
3 The square footage
4 The hours of occupancy or building schedule
5 One-year's utility data
6 Several photographs that identify equipment and document the building's current condition
7 Interviews with employees and building operators
8 Specifications of major electrical mechanical and plumbing related equipment (anything that uses energy)
Energy data and building information collected in the field are analyzed to determine the baseline energy performance of the building. Using spreadsheetbased energy calculations, C.E.R.T. estimates the energy and cost savings associated with the installation of each of the recommended Energy Conservation Measures (ECM). The energy assessment or audit report presents the results of these efforts.
CLASSIFICATION OF ENERGY AUDITS OR ASSESSMENTS
Energy Analysis, Assessments and Audits can be mentioned interchangeably. As stated in ASHRAE Procedures for Commercial Building Energy Audits (2004) the assessments can require different levels of effort depending on the needs and resources of the owner These classifications are:
* Preliminary Energy Audit (PEA)--typically a spread sheet based report identifying the top five ECMs
* Level I Energy Audit--this report elaborates on the PEA in a basic Word document
* Level II Energy Audit--this is a more detailed report with several ECMs and ROI calculations
* Level III or Detailed Energy Audit (DEA)--this is a thorough report, where commissioning of the building is sought
BUILDING AUTOMATION SYSTEMS (BAS)
Building Automation Systems (BAS) are centralized, interlinked networks of hardware and software, which monitor and control the environment in commercial, industrial and institutional facilities (KMC Controls, 2013). While managing various building systems, the automation system ensures the operational performance of the facility as well as the comfort and safety of building occupants. Generally, building automation begins with control of mechanical, electrical, and plumbing (MEP) systems (KMC Controls, 2013).
Regardless of what type of MEP system exists in a facility, it can be controlled intelligently, effortlessly and more efficiently with a BAS using typical energy management strategies as shown in Table 1. These strategies can be implemented without a BAS, using thermostats and/or time control time-of-day schedulers, and a bit of common sense. Typically a building's single largest expense is energy costs. Utilizing a BAS, to monitor and manage your building's lighting, HVAC and other systems automatically, and building specific scheduling programs will gain control of energy costs.
When a BAS is not present, a more "hands-on" approach is necessary. Training and commitment to control strategies will save money; as long as the building's energy use systems are running properly, the systems can be controlled efficiently. Failure to utilize available features restricts equipment use, especially with controls. It is surprising how many schools spend hundreds of thousands or even millions of dollars on control implementation, but fail to use many of the features provided by the systems. The site visits and school assessments show that most schools are using only a small portion of their control capabilities. There are a number of common human factors that contribute to this problem, as shown in Table 2.
By avoiding obstacles that hinder energy efficiency and following these simple low-tech/no-cost strategies, school administrators can increase the chances that the systems they purchase and install will not only meet their needs, but also help them lower the utility costs of their schools immediately.
LOW-TECH/NO-COST CONTROL STRATEGIES
C.E.R.T.'s suggested top three low-tech/no-cost opportunities to save energy in schools are: develop and implement an energy awareness program, coordinate an energy competition similar to National Energy Education Development Project (NEED), and optimize HVAC and lighting through proper scheduling.
Implement an Energy Awareness Program
As thoroughly stated in the FEMP's, A Handbook for Federal Energy Managers, an energy awareness program is essential to saving energy in schools. Four key components are:
1. Planning--set goals and objectives, recruit, assess communication channels and financial resources and create data reporting and evaluation measures.
2. Design and Implementation--solicit input, identify behaviors, develop motivational techniques, develop schedule and produce visual materials.
3. Evaluate and Report Results - obtain feedback on evaluations, document the savings and share results.
4. Sustainability - develop ways to launch the program, continue to implement incentives and publicly recognize accomplishments and conduct regular meetings (FEMP, 2007).
Research has uncovered that energy savings up to 10% can be achieved in a school district simply through awareness. A large school district in North Carolina claims that some schools have saved up to 40% when comparing a single month to its previous year. (Obviously there are many factors that can influence these figures including outdoor air temperatures, occupancy levels, etc.) Teachers, students, custodians and administrative staff all generate a new school spirit around saving energy by turning off lights, televisions, computers, printers and monitors, utilizing window shades, and daylighting techniques. There is also proof that the participants in the program spread their newfound knowledge to the community.
Coordinate Energy Competitions
Energy competitions within a school district are educational and save utility costs. The most recognized national competition is the National Energy Education Development Project (NEED). All NEED schools have outstanding classroom-based programs in which students learn about energy. This program combines academic competition with recognition to acknowledge everyone involved in NEED during the year, and to recognize those who achieve excellence in energy education in their schools and communities. The students and teachers set goals and objectives, and keep a record of their activities. In April, the students combine their materials into scrapbooks and send them to their state coordinators (NEED, 2013). This competition requires reports to be submitted with proof of implementing energy conservation techniques that save money for the school and community. A district in North Carolina implemented their own "Energy Challenge" and awards schools based on specific goals that must be met. Their program is loosely based on the NEED program and has been in place for the last 3 years. This author received e-mails reporting energy savings of between l%-30% in 2012, and l%-40% in 2013, from schools that competed in an energy awareness and conservation program, as compared to schools in the district that did not participate.
Utilize Control Scheduling Strategies with BAS, Time Clocks, and Thermostats
These strategies and others are thoroughly described in Murphy's article, Using Time-of-Day Scheduling to Save Energy, published in ASHRAE Journal, May 2009. Night setback and optimal stop, is the strategy that allows indoor temperature to drift during unoccupied periods; in other words, the systems are turned off when nobody is in the schools. Obviously, the systems must be set to optimal start, allowing the system time to reach the desired indoor temperature comfort levels prior to anyone entering the school. Murphy also mentions that fresh outdoor air louvers can be shut during unoccupied periods to further save energy. If a manual system is installed or the operations department is hesitant to completely turn-off systems at night, then the systems can at the very minimum be adjusted a few degrees (+/-10[degrees]F depending on cooling or heating mode) so the HVAC systems don't work as hard during unoccupied periods (evenings and weekends).
Too many schools have extremely conservative schedules; which means the systems are started too early (6:00am) and stopped too late (6:00pm). If students start getting to the classrooms by 7:25am and the majority leave around 2:30pm, then a schedule should mirror the occupancy. Why are we conditioning these spaces in the same manner when the building has 500 fewer occupants? Typically teachers get to their classrooms between 15 and 30 minutes prior to the children, and leave closer to 5:00pm. The majority of school administration and custodial staff are on similar schedules. The building's HVAC systems could be turned on at 6:30am if the teachers begin their day at 7:00am and turned off at 4:30pm if the teachers tend to leave at 5:00pm. Large spaces in schools like the cafeteria, gymnasium, media center, library, stage and computer labs are perfect opportunities to modify specific mechanical and electrical systems. Several school audits consistently show energy waste in lighting and HVAC systems in hallways, stairwells, restrooms, and other large spaces. The habits do not change whether the audit is performed during the summer months, during the school day, or in the afternoons when the students have left the building. There is a strange habit of leaving cafeteria and gymnasium lights on when they are unoccupied. Several schools leave hallway lights on around the clock. These practices can be costly from an energy perspective, since the entire school may be operating to maintain occupied temperature setpoints, although only a few spaces are occupied (Murphy, 2009), such as during the summer months when only the administrative and custodial staff is working. Schools go from hundreds of occupants to under ten during school breaks.
Another energy saving strategy is to set the override feature for a 2-hour period of time. If a space or zone needs conditioned air during an unoccupied mode and the override is employed, ensure it is not on indefinitely. Therefore, automatically returning the zone to the unoccupied mode after the 2 hour defined time limit. This feature goes hand-in-hand with less conservative time-of-day operating schedules.
Create separate time-of-day operating schedules for areas of the school with significantly different usage patterns. This author has seen a Media Center's schedule that specifies no classes on Mondays and no classes until 8:50 am Tuesday-Friday, with nothing after 2:40 pm. This specific media center is occupied roughly 28 hours per week when school is in session or 17% of the week it needs MEP equipment running. Gymnasiums, cafeterias, and all specials (music, art, etc.) have separate schedules that can save energy. If administration, teachers and custodians communicate with the operations departments per school in a district, millions of dollars in utility costs can be conserved.
Results from Actual Energy Retrofit Projects
The tables and figures shown are developed from actual utility data recorded during energy audits in North Carolina. The first example refers to two middle schools built in the same district in 2007, with approximately the same number of students and staff. The school buildings are identical, however they are in two different locations with different site orientations, and vary in annual energy consumption between 16% - 20%. "School A" is in an open field with direct sunlight with a west-southwest position, and "School B" is in the shade of a mountain with a southeast position. All classrooms had individual heat pumps controlled by manual thermostats in the classrooms.
The total electrical energy used by both schools was recorded for five years. "School A", as shown in Figure la, follows an unusual annual pattern where the spring, summer and fall seasons are relatively flat. "School B", as shown in Figure lb, follows a normal annual pattern where more energy is used during cooler weather. C.E.R.T. assumed building orientation had some effect on the pattern, but after modeling both buildings, the difference in orientation resulted in only a l%-2% energy difference.
The schools had two different electrical contractors program their twelve channel electronic time control, time-of-day schedulers. There were 12 channels set into the controller and each channel had two events (On and Off). The channels were identified as: Gymnasium, Classrooms Wing 1, Classrooms Wing 2, Kitchen, Cafeteria Dining Room and Stage, Classrooms Wing 3, Classrooms Wing 4, Administration and Main Office, Media Center and Library, Classrooms Wing 5, Locker Room Water Heater, and Kitchen Water Heater.
"School A" had a programmer error that was identified during the audit where a channel was always ON because the event to turn it OFF was accidently programmed into another channel. As a result, since 2007 the HVAC systems in that zone were always ON, but being controlled by manual thermostats. C.E.R.T. identified that both schools had an extremely basic program with little to no thought process built into the scheduler; all zones were turned ON at 6:00 am and turned OFF at 6:00 pm Monday through Friday year round. "School A" set the same schedule (6:00 am-6:00 pm) for weekends, and "School B" was set to be ON in all zones from 8:00 am-1:00 pm on Saturdays and Sundays. No holidays, vacations, or teacher workdays were entered into either scheduler. In a school facility, this is a critical component when considering energy conservation.
Simple math shows that scheduling alone makes up the large discrepancy between the two identical schools. "School A" had its systems ON for 84 hours per week and "School B" had its systems ON for 70 hours per week, which is a difference of 16.67%. The 5-Year Average School Energy Comparison between schools "A" and "B", as shown in Table 3, and 2011 School Energy Comparison, as shown in Table 4, both show the average difference in electrical costs range from $15,000-$17,000 annually (Ave. Cost $0.08/kWh includes Demand Charges and Sales Tax).
C.E.R.T. reprogrammed both schools to further minimize their energy consumption. We identified that the school day began at 7:30 am and ended around 2:30 pm, with teachers leaving closer to 5:00 pm. The revised schedule was set for the systems to turn ON at 6:45 am and OFF at 4:30 pm Monday through Friday, and OFF during weekends. (The kitchen, gym, and administration office had different settings.) The school's holiday and summer schedule were also implemented. In the summer months (half of June, all of July, and half of August) the administration zone was ON for 8 hours per day Monday-Friday, and all other zones were set at minimum levels of operation to avoid any unforeseen mold and moisture issues. It is possible to override all events within the scheduler as required. Both schools are now on identical energy saving schedules, and it is estimated that an additional 16%-20% will be achieved for both schools annually in addition to the original 16% for School "A" having a different schedule than School "B", for a total annual savings of $30,000 for the district. These were the two newest schools in the district at the time of our audits, and the only schools we addressed. There were 21 schools in the district, and similar scheduling efforts could save the district a minimum of $10,000 per school for annual savings over $200,000. Reprogramming the electronic time control, time-of-day scheduler required only one hour per school, and since C.E.R.T. is a university-based center, we use our time for students to gain experience and develop energy related research; our efforts were free for the district.
One District's Elementary School EUI Comparison, as shown in Figure 2, has a fluctuating pattern among the 62 elementary schools in the district. Most schools in America tend to cluster around the median energy use intensity of approximately 68,700 BTU per square foot ([ft.sup.2]) or 780.2 MJ/[m.sup.2] from all energy sources (Energy Star Building Upgrade Manual). As noted in Figure 2, this district has an average EUI of 84 kBTU/sf or 953.9 MJ/[m.sup.2], which exceeds the national average by 20%. Scheduling and awareness could easily bring the EUI average in line and save this particular district an estimated $500,000-$1,000,000 annually in the elementary schools alone.
There is a disturbing trend in the summer months at another elementary school in the district, as shown in Figure 3, Elementary School Energy vs. Outside Air Temperature (OAT).
The graph shows that the OAT follows a standard bell-curve, the natural gas usage trends accordingly, and the electrical usage is almost flat from May to September, yet the school has 600 fewer occupants from mid-June to mid-August. This is a "red-flag" to energy auditors, as efficient school data should reflect a binodal pattern during summer months. This specific school is obviously not on a summer HVAC and lighting schedule when fewer than 10 employees are in the building for two months. During the audit it was discovered that all of the lights were on, the school was at a comfortable 72[degrees]F for only eight employees limited to two zones- the cafeteria and the front office. These "bad-habits" are common in schools and universities and simple awareness programs cure these issues. The principal of each school can be required to control energy usage during the school breaks as part of their annual goals. A local district has implemented a summer energy management initiative. The plan involves four-day summer work weeks, as well as a district-wide effort to minimize energy and water usage. Summer energy conservation initiatives such as this should be developed and implemented for all schools nationwide.
Developing and implementing an energy awareness program, coordinating an energy competition, and optimizing HVAC and lighting through proper scheduling are three low-tech/no-cost strategies to save energy in schools. Avoid overly conservative scheduling by using night setback, optimal start and stop, and timed override buttons, use separate time-of-day schedules for areas with differing usage patterns, and identify "bad-behavior." These simple strategies help improve this low-tech idea to save energy in schools without sacrificing student, teacher, and administrative staff's comfort.
This article was produced under the direction and guidance of my PhD advisor, Dr. Nabil Nassif, who is an assistant professor in the Department of Civil and Architectural Engineering at NC A&T State University. In addition, several individuals at NC A&T State University including the Center for Energy Research and Technology were instrumental in the writing and development of this document, including the center's director, Dr. Harmohindar Singh who is a Professor Emeritus in the College of Engineering, my wife Michelle for her editing, and Carol Graydon, the Energy Engineer for Guilford County schools, who provided valuable data documented in this article.
ASHRAE = American Society of Heating, Refrigeration and Air Conditioning Engineers BAS = Building Automation System C.E.R.T. = The Center for Energy Research and Technology EMCS = Energy Management Control Systems HVAC = Heating Ventilation and Air Conditioning MEP = Mechanical, Electrical, and Plumbing NEED = National Energy Education Development Project USEPA = United States Environmental Protection Agency 1 kWh/sf = 3.412 kBTU/sf lkBTU/sf = 11.356 MJ/sq.m
ASHRAE. 2004. ASHRAE Procedures for Commercial Building Energy Audits (2004).
KMC Controls. 2013. Understanding Building Automation and Control Systems. www.kmccontrols.
Murphy, J., and N. Maldeis. 2009. Using Time-of-Day Scheduling To Save Energy. ASHRAE Journal, May 2009, 42-48.
NEED. 2013. National Energy Education Development Project, www.need.org
Piper, J. 2004. Stepping Up To BAS Success. Building Automation, www.facilitiesnet.com/buildingautomation
U.S. Department of Energy Federal Energy management Program, FEMP, July 2007 Creating an Energy Awareness Program: A Handbook for Federal Energy Managers.
USEPA, United States Environmental Protection Agency, Office of Air and Radiation 2008 Edition. Energy Star Building Upgrade Manual. www.energystar.gov/index.cfm?c = business.bus upgrade manual
Student Member ASHRAE
Nabil Nassif, PhD, P.E.
Harmohindar Singh, PhD, P.E.
Student Member ASHRAE
R.C. Tesiero is a Mechanical Engineer, PhD graduate student and Research Coordinator for C.E.R.T. at North Carolina A&T State University, Dr. Nabil Nassif is an Assistant Professor in the Department of Civil and Architectural Engineering at NC A&T SU, Dr. Harmohindar Singh is a Professor Emeritus in the College of Engineering at NC A&T SU and Carol Graydon is an Energy Engineer with Guilford County Schools.
Table 1: Typical Energy Management Strategies Strategies Time of day scheduling Chilled/hot water reset Avoid conservative scheduling Separate schedules for area or zone usage Night setback Zone temperature sensors Optimal start/stop Chiller/rower optimization Implement an energy awareness program Develop distria energy competition (NEED) Economizers VAV fan pressure optimization Occupied standby mode Systems integration Demand limiting Demand Control Ventilation (DCV) Supply air reset Variable flow pump pressure optimization Table 2: Human Factors that Waste Energy in Schools Common Factors Fear of change Lack of energy conservation awareness from top-down approach Lack of training Need to please co-workers' individual comfort levels Lack of planning Simplicity of "overriding" system parameters Insufficient staffing Lack of fundamental HVAC theory Fear of internal politics Tack of propramming knowledge Failure to tune the system Failure to maintain the system Table 3. 5-Year Average School Energy Comparison Month/Year School "A" kWh (MJ) School "B" kWh (MJ) January 133,560 (480,816) 134,880 (485,568) February 146,760 (528,336) 127,920 (460,512) March 127,620 (459,432) 104,220 (375,192) April 107,100 (385,560) 76,200 (274,320) May 83,160 (299,376) 79,980 (287,928) June 97,140 (349,704) 73,140 (263,304) July 98,160 (353,376) 52,260 (188,136) August 92,340 (332,424) 68,040 (244,944) September 98,640 (355,104) 97,440 (350,784) October 102,640 (369,504) 78,000 (280,800) November 86,700 (312,120) 77,760 (279,936) December 93,240 (335,664) 111,360 (400,896) Annual Total 1,267,060 (4,561,416) 1,081,200 (3,892,320) Month/Year Ave Cost "A" S0.08/kWh Ave Cost "B" S0.08/kWh January $10,684.80 $10,790.40 February $11,740.80 $10,233.60 March $10,209.60 $8,337.60 April $8,568.00 $6,096.00 May $6,652.80 $6,398.40 June $7,771.20 $5,851.20 July $7,852.80 $4,180.80 August $7,387.20 $5,443.20 September $7,891.20 $7,795.20 October $8,211.20 $6,240.00 November $6,936.00 $6,220.80 December $7,459.20 $8,908.80 Annual Total $101,364.80 $86,496.00 Table 4. 2011 School Energy Comparison Month/Year School "A" kWh (MJ) School "B" kWh (MJ) January 167,700 (603,720) 164,400 (591,840) February 147,000 (529,200) 141,600 (509,760) March 126,600 (455,760) 100,800 (362,880) April 123,900 (446,040) 77,100 (277,560) May 91,800 (330,480) 80,100 (288,360) June 107,400 (386,640) 82,500 (297,000) July 99,900 (359,640) 58,200 (209,520) August 89,700 (322,920) 92,100 (331,560) September 116,400 (419,040) 89,100 (320,760) October 102,600 (369,360) 73,200 (263,520) November 82,200 (295,920) 77,400 (278,640) December 92,700 (333,720) 85,500 (307,800) 1,347 900 (4,857,4401 1,177,000 (4,039,200) Month/Year Ave Cost "A" S0.08/kWh Ave Cost "B" S0.08/kWh January $13,416.00 $13,152.00 February $11,760.00 $11,328.00 March $10,128.00 $8,064.00 April $9,912.00 $6,168.00 May $7,344.00 $6,408.00 June $8,592.00 $6,600.00 July $7,992.00 $4,656.00 August $7,176.00 $7,368.00 September $9,312.00 $7,128.00 October $8,208.00 $5,856.00 November $6,576.00 $6,192.00 December $7,416.00 $6,840.00 $107,837,00 $89,760.00
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|Author:||Tesiero, R.C.; Nassif, Nabil; Singh, Harmohindar; Graydon, Carol|
|Publication:||ASHRAE Conference Papers|
|Date:||Dec 22, 2014|
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