Summary Paper on Controls for Metering and Feedback

Transcription

1 Summary Paper on Controls for Metering and Feedback Measured performance for commercial buildings, the actual collection of data and use in benchmarking and efficiency assessments, is making significant inroads into areas such as codes and utility programs as well as traditional areas like facility operational maintenance and owner/manager asset management. The future portends that measurement, analysis and feedback of performance will become even more of a priority for building owners and managers, as well as occupants. Additionally, understanding this trend will allow controls vendors to better prepare for the best practice efficiency methods of the future. Advanced metering and active feedback is not widespread in commercial buildings of any size. In small to medium commercial buildings (those approximately 50,000 ft 2 and smaller) there is an even more difficult cost/benefit problem to justify metering and feedback. Recent trends towards app -based integrated controls for smaller spaces, performance based policy and regulation, designing for meterability, and growing familiarity with equipment and options indicate that these technologies will eventually provide the foundation for widespread metering and feedback. Energy Information System Technology The use of meters and sensors, data acquisition, remote data storage, and software for building energy analysis is generally called an energy information system (EIS). This covers a broad spectrum of technologies and levels of application within the building, data acquisition methods, and purposes of the software that analyzes the data. Figure 1. Simple EIS System Diagram

2 In general a sub-category of EIS where the Building Automation System (BAS) is used to collect meter and sensor data is called an Energy Management and Control System (EMCS). An EMCS is rare in small to medium commercial buildings where the HVAC and controls are usually isolated and not sophisticated, there are no dedicated site personnel, maintenance is handled by a third-party contractor, and the cost is viewed as too high. Software Tools. Feedback to managers or occupants is enabled through software that parses the EIS data. Software as a Service (SaaS) appears to be emerging as a successful model where users pay a service fee to use the web-based software and have data transferred directly from hardware purchase from another vendor or via another database to the software. Software capabilities and methods vary based on the intended audience for the package. These fall into a few broad categories: Enterprise Energy Management (EEMS) A tool for portfolio managers to track building assets in a portfolio and often benchmark internally or by Portfolio Manager Facility Manager Software A tool with more detailed interval data analysis, regression, and reporting capabilities of whole building, system, and equipment level meters and sensors for use in operational upkeep of a building. Utility Data Management A software tool intended for use by a utility administrator to process large amounts of interval data simultaneously. Typically not useful for buildings. Occupant Feedback and Dashboards A tool to convey information to tenants or occupants with simplified metrics using its greater graphical capabilities. An NBI survey of available software tools reveals the following breakdown in intended audiences for these tools: Table 1. Survey results of 50 software tools for energy data analysis Tool Dashboard Facility Manager Enterprise EEMS Utility Data Mgmt Target Occupants Operator/Eng Owner/manager Program Manger # out of 50 Total

3 Cost/Benefit for Small-Medium Buildings An EIS is often prevented from being employed in small-to-medium commercial buildings because of cost/benefit concerns. Figure 2 shows how many years it takes for simple payback to occur for buildings of different sizes for whole building electric and gas interval data with data retrieval and feedback for a 10 year span. It is assumed that 5% savings, on $1.50 per ft 2 of expenditures, will result from the use of the metering and the cost of the package is a Net Present Cost over 10 years of $7500. Years to Simple Payback Years to Simple Payback For Facilities ,000 20,000 30,000 40,000 50,000 Facility Size - SF Figure 2. Payback for Basic EIS Common Whole Building Analysis Analysis of energy performance at the whole building level involves simple metrics, inspection of data, and regression with Baselining and Benchmarking. These techniques may be used to analyze small-to-medium building performance and are available in various software interfaces for meter data. Analysis methods can also be looked at as periodic measurements, ones that are based on billing cycles or larger blocks of time to smooth out transients, and continuous measurements that use short interval data from advanced meters that are used in day-to-day operations. Periodic Analysis E.g. Monthly, Annually Energy Use Intensity (EUI) Baselining Simple tracking of usage per square foot tracked for energy bill management and to look for gross performance deviations but not particular good for performance analysis. Weather-normalized EUI Baselining Slightly more advanced analysis with EUI adjusted for weather variations. ENERGY STAR Portfolio Manager Benchmarking Score A common benchmarking tool well known in the real estate community and useful as an operational first step. It uses the CBECS, a USDOE survey data set, to normalize a building s energy against like type properties and assess relative performance on a scale. This is used by asset managers and operators, and is becoming more prevalent in program and policy requirements as discussed below. More than 65,000 buildings received an ENERGY STAR energy performance score in 2009, a 50 percent increase over

4 Average Power Density W/ft Site Energy Signatures Rico Seco El_ Thru May Monthly Average Degrees F Ref: Site total Site Total: EUI 56.3 kbtu/sf Site electricity Site gas Figure 3. Example of the energy signature and a chart showing the extent of EPA benchmarking to date Energy Signature The energy signature is an evocative display of energy usage normalized for temperature, SF, and monthly data (though any interval can be used). The reduction of the usage into average power in W/ft2 demonstrates how the building reacts to temperature and allows operational characteristics like baseloads and heating and cooling performance to be examined more intrinsically. Continuous Analysis Advanced meters provide access to short interval data that can reveal problems in operations. Direct examination of the data can often reveal to operators or occupants the existence of savings opportunities. These methods are less likely to be used in small to medium buildings where an operator is not present. Interval Data Regression Baseline Analysis Shorter interval data can also be normalized and linearly regressed by comparing to independent variables. This feature reveals to operators and occupants when there are deviations from normal behavior that may not be discernable by direct examination. Advanced Regression and Neural Network Analysis A more advanced from of Baselining where operational anomalies can be automatically detected and listed as potential improvements for operators or occupants without system level metering. System- and Equipment-Level Metering and Feedback System-level metering consists of meters or groups of meters that measure usage by a particular building system category such as HVAC, heating, cooling, ventilation, lighting, plug and process loads, or common areas. This separation of system-level metering is not common in commercial building but may become more prevalent with the advancement of new building codes. The 4

5 ability to isolate system loads, though complicated by technical and definitional problems, assists in maintaining persistence in building energy performance. Submetering tenants to charge for electrical usage, also known as submetering for utility allocation, can be considered a system level meter. In this case the system is the tenant whose usage may include lights, plugs, processes, and even HVAC. The PlaNYC in New York City is requiring submetering for utility allocation in spaces 10,000 ft 2 or larger and tenants are increasingly asking for actual submetering to avoid gross lease estimates and potential overpayment. Occupants and Tenant Feedback Tenants are increasingly asking for direct submetering for utility allocation where possible, and LEED for Commercial Buildings and many software tools are looking to provide a dashboard for occupants to display whole building or tenant space level metered data. NBI sees the submetering and feedback of tenant data as a growing trend. The display of data may not be enough. To drive tenants or occupants to savings, the use of social networks and organizational strategies will be necessary. In one example, Perkins and Will is implementing metering and energy savings competitions among their office throughout North America and Canada. This use of a strategic network or competition seems to enhance the participation of tenants and their control of their loads. No data is available on this trend. Policy Intersections State and local policies are affecting whole building performance in a few jurisdictions, and voluntary energy codes, like AB Core Performance and the IgCC, are also looking at metering and performance requirements. The State of California has notably led the way with AB1103. The legislation is intended to require that the building s performance, via the ENERGY STAR score, be determined and reported when the building is sold to a new owner. The City of Seattle has followed suit by requiring disclosure of the ENERGY STAR portfolio manager rating at the time of building sale or to any potential tenants. The EISA 2007 federal law has mandated that government facilities install advanced metering when cost effective. This doesn t include many small-medium commercial buildings which fall below the cost-effectiveness criterion. These legislations set a precedent for the broader goal of building performance labeling. A regular and systematic program of building performance labeling is still some years away. The IgCC 2010 is the first energy code, though a voluntary code, that sets a measured building performance requirement via the zero Energy Performance Index (zepi). The 5

6 scale measures energy performance relative to an historical benchmark EUI for the same building use-type in the year 2000 and requires permanently installed whole building advanced metering. In addition, the code requires new construction to Design for Meterability to isolate loads. What this means for small-to-medium commercial buildings is the energy distribution design provide easy-to-access meter points that can isolate system loads. This allows for diagnostic evaluation with only whole building advanced metering required for permanent installation. Utility Program Intersections AMI/AMR and the Smart Grid. Whole building advanced metering may happen through a utility upgrade in certain territories. In 2008 approximately 4.2% of electrical meters were characterized as AMI (two-way) and 35% as AMR (one-way) automated interval data collection. Though currently over 50% of meters are still electromechanical. AMI penetration is expected to expand to 35% by A few utilities are offering feedback, based on the AMI/AMR meter data, which can be used by the customer as a rudimentary EIS, and may even include a portfolio manager score. For electriconly buildings this may prove useful. Unfortunately gas data for buildings is not easy to acquire automatically by an owner or manager. Gas AMI roll-outs are spotty and the landscape for interfacing with their data is still unclear. Anecdotal evidence suggests utility programs are increasing becoming interested in measurement and verification of savings for utility energy efficiency programs and requiring benchmarking for buildings that participate in programs. Monitoring-Based Commissioning (MBCx). A successful program model that was demonstrated for utility program use of EIS is Monitoring-Based Commissioning or MBCx. Developed by LBNL and the energy lab at Texas A&M University, the approach uses meter data to enhance the retrocommissioning process and then monitor subsequent use to ensure savings are persistent. This program is now offered in some utility areas of California. Small to Medium Commercial Building Metering and Feedback Trends Whole building interval data Whether it is through utility Smart Grid installations or other drivers, the small to medium building sector should see increasing use of whole building interval data for at least periodic analysis, if not continuous analysis. The buildings control system or network should be designed to easily incorporate these data sources. Regular tracking via benchmarks or energy signature Codes and ordinances are looking like the harbingers of increased disclosure of building energy benchmarks. The 6

7 energy signature or another more expressive periodic analysis method should be readily calculable for any building. Submetering and feedback for occupants and tenants As building energy performance improves, the largest share of energy use starts shifting to lighting and plug loads. Tenants will need simple metrics and a feedback mechanism to influence the hard-tocontrol tenant plug loads. Organization and social network strategies will play a role in optimizing the feedback. Load isolation design, DFM, or automated diagnostics for major components Load isolation during the design phase will allow for easier periodic evaluation of buildings and control systems may want to anticipate the need for data collection during a checkup where additional system meters are installed. Smart Grid The scope of requirements for a building s participation in the smart grid of the future is still difficult to predict. The Open ADR is a standard that is emerging for demand response notifications and may be part of metering and feedback picture. The need for integrated controls including metering and feedback is an efficiency concern and the success of the Smart Grid may help expedite achieving the desired metering and feedback. 7