1、 4706 (RP-1146) Benefits of Mu It -Building Electric Load Aggregation: Actual and Simulation Case T. Agami Reddy, Ph.D., P.E. Member ASHRAE Associate Member ASHRAE Jason K. Lukec Studies Leslie K. Norford, Ph.D. Member ASHRAE ABSTRACT The structure of the electric utility market and the complex rela
2、tionship between suppliers and consumers has undergone (and is undergoing) changes in recentyears as a result of elec- tric deregulation and real-time pricing schemes. This paper reports some of the results from an ASHRAE research project entitled “Building Operation and Dynamics Within an Aggre- ga
3、ted Load” (RP-1146), which was meant to (a) identih situ- ations and conditions under which aggregating individual building loads is attractive for managing total, multi-building load, and (b) identifi and evaluate operating and control strat- egies for use in individual buildings that will reduce e
4、nergy operating costs at the aggregate level by taking advantage of the diversis in demand among buildings. This paper presents two case studies: one based on an actual urban university with multiple buildings of di8erent spes and functions and one based on a DOE-2 simulation study that consisted of
5、 aggre- gating three diferent building types (an ofice building, a hotel, and a retail store). The bene$ts of multi-building load aggre- gation and control are presented and discussed in this paper. It is found that both case studies are consistent in their results. About 5% to 6% demand savings can
6、 be achieved due to load aggregation across multiple buildings as compared to the sum of the individual peaks even when each of these buildings is under active load control. INTRODUCTION This paper summarizes pari of the work performed under an ASHRAE research project entitled “Building Operation an
7、d Dynamics Within an Aggregated Load” (W-1146) (Reddy and Norford 2002), which was meant to: a. identie situations and conditions under which aggregating individual building loads is attractive for managing total, multi-building load and b. identi and evaluate operating and control strate- gies for
8、use in individual buildings that will reduce energy operating costs at the aggregate levei by tak- ing advantage of the diversity in demand among buildings. Research was done in two phases. Tasks undertaken as part of Phase I involved an extended backgroundand historical perspective on electric util
9、ity aggregation, a detailed descrip- tion of each of three case-study sites where multi-building load aggregation and subsequent energy management strate- gies were performed, and a summary of the lessons learned from the above case studies. The second phase of the work consisted in formulating and
10、developing a list of 1 1 tools that could be used by aggregators and their customers to alter the operation of buildings to control load. These are described in technical papers by Reddy and Norford (2003) and Norford and Reddy (2003). This paper presents the historical perspec- tive and the results
11、 of one of the case studies. Further, we present the results of a siniulation case study that involved aggregating three different types of buildings-an ofice building, a hotel, and a retail store-along the same type of load aggregation and energy management strategies as iden- tified under Phase I.
12、 Agami Redy is a professor in the Civil, Architectural and Environmental Engineering Department at Drexel University, Philadelphia, Pa. Jason Lukes is with R.G. Vandenveil Engineers, Princeton, N.J. Les Norford is principal at Tabors Caramanis and Associates, Cambridge, Mass. 130 02004 ASHRAE. HISTO
13、RICAL PERSPECTIVE ON ELECTRIC UTILITY AGGREGATION This section explains the conditions prevalent in existing deregulated electric utility markets, primarily in Massachu- setts andPennsylvania, which give customers a choice of elec- tricity suppliers. The information presented here is a result of per
14、sonal discussions with several load consultants participat- ing in the deregulation process and from books such as one by Thumann (1 999). The emphasis of the discussion presented below is on load control, which arises from a change in the util- ity environment and is not meant to be an authoritativ
15、e discus- sion on deregulation per se. Note also that the deregulation scenario is in a state of constant flux and has evolved greatly in the last few years. Because building load control is more attractive under demand-based rate structures, the focus is on the characteristics of these rates and th
16、e behavior of customers who must respond to them. Participation in Deregulation While many of the players in the competitive electric market are larger commercial and industrial campuses, smaller customers also have the option to take advantage of unbundled prices and better rates for electric usage
17、. The prob- lem is that many small customers must be aggregated for the supplier to ensure the demand of a significant portion of his generating capacity. From the supply side, this involves great risk and, therefore, incentives for such activity are presently minimal. The following sections describ
18、e, in more detail, the process of deregulation and break down customers who take advantage of it. Restructuring and Retail Access Electric industry restructuring has introduced retail access. Retail access enables end-use customers to “shop” for the electric services that suit their needs. Such serv
19、ices include both the energy component (the electricity itself) as well as other “value added” options. Such options may include billing choices, energy pricing options, and various support services. Examples of these are: i. Aggregate or coincident (also known as conjunctive or consolidated) billin
20、g-This pertains to the case when a customer receives one monthly bill for the aggregate peak demand of all his or her electric meters as compared to a bill that reflects the sum of all the individual peaks of his or her electric meters. This type of aggregation takes place at the facility levei-usua
21、lly a large institution-where it is feasi- ble to combine all existing electrical services into one large service. . Some load consultants consider the term “electric deregulation” to be a misnomer, preferring instead to use the term “re-regula- tion.” In any case, what we imply here is an important
22、 change from the former regulatory environment in which generation, transmis- sion, and distribution have been separated into distinct activities, which are no longer under the exclusive jurisdiction of one company. 2. Budget billing-A customer is billed the same amount each month with minor correct
23、ions annually (available for some time). Energy priced at a benchmark plus or minus some percent- age. 3. Fixed price energy. 4. 5. Energy use analyses. 6. Energy efficiency engineering and design services. The term “load control” refers to changes in the operation and dynamics of individual buildin
24、gs, which come from shift- ing load from high-priced hours to low-priced hours. While energy-saving measures may also be employed to reduce consumption, they cannot be considered to be load control measures unless the customer has the ability to curtail load in response to some demand signal. So far
25、, retail access has been implemented in California, Massachusetts, and Pennsylvania. Additionally, restructuring legislation has been enacted in eighteen states, including Arizona, Arkansas, Connecticut, Delaware, Illinois, Maine, Maryland, Montana, Nevada, New Hampshire, New Jersey, New Mexico, Ohi
26、o, Oklahoma, Oregon, Rhode Island, Texas, and Virginia (EIA 1998). Most remaining states are investi- gating the possibility of electric restructuring. In December 1999, the Federal Energy Regulatory Commission (FERC) ordered all electric utilities to file plans to be part of Regional Transmission G
27、roups by late 2000. This order, Order 2000, has subsequently been watered down in 2002, with FERC currently having a market structure white paper for discussion (Fernands 2003). In states where electric retail competition has been imple- mented, building owners have three major categories of oppor-
28、tunities to reduce their annual electricity bill-changing suppliers (supply choice), shifting consumption from high- price hours to lower-price hours (load control), and reducing the level of consumption (efficiency improvement). Of these, changing suppliers is the newest option and is the least cap
29、ital intensive. The remaining two options-load control and effi- ciency improvement-have been available for many years and often require major capital investments. To assist customers who elect not to choose an energy supplier, states have created “default service.” Default service, also called the
30、standard ofer, is a price-regulated service offered by providers meeting state-set criteria. The method used to set prices for standard offer service varies from state to state. For example, in Pennsylvania, prices were set for each customer class, by utility, to approximate retail levels. In contra
31、st, in Massachusetts, a single price was set for all customer classes within each utility. The Massachusetts prices were set at or below wholesale levels in the initiai years and are now increasing to estimated retail levels over a seven-year transition period. The terms and conditions of “standard
32、offer” service have a major impact on the benefits that may be accrued through the use of the energy control strategies mentioned above. In some ASHRAE Transactions: Research 131 utility service territories, the savings due to load control may be lower during post-deregulation relative to pre-deregu
33、lation because of the design of standard offer service and the policy governing the recovery of a utilitys stranded costs. In some instances, standard offer service prices are so low as to discourage competition from other energy suppliers because the margins available to them do not exceed the cost
34、 of customer acquisition. Similarly, some standard service offer- ings are attractive to customers, and the opportunity cost of researching options may appear to outweigh the savings avail- able; hence, the consumer is not encouraged to leave the default service. Building owners in states with retai
35、l competition have begun to switch from “standard offer” service to competitive energy suppliers. Suppliers are soliciting building owners with attractive pricing and other service options. The attractive pricing is available because if a supplier can guarantee suffi- cient load over a pre-specified
36、 duration, the supplier can frequently obtain power at lower rates than could a building owner acting alone. Such suppliers may be able to offer elec- tricity at a price less than “standard offer” because their partic- ipants have entered multi-year purchasing commitments and not because they have a
37、 load profile materially different from the load profile of customers who chose the standard offer service. Power suppliers focusing primarily on buildings with a load profile appreciably different from standard offer service appear to be the exception rather than the rule. Building owners in these
38、situations benefit because the savings on the energy component can outweigh benefits that may be achieved through load control or efficiency improvements. This is due in part to how electric prices are currently structured. ACTUAL CASE STUDY SITE #I Site#l is an average urban university with a wide
39、variety of building types that includes offices, classrooms, labs, and dormitories. Even more importantly, buildings of like use are often in close proximity to one another. For this reason, even in cases where individual building information is not present, a use profile may be relatively easy to d
40、iscern, especially in those areas where a complex of similar buildings is served by one mechanical plant. Also, the senior plant engineer has extensive knowledge of the optimization techniques that have been used to shave demand peaks in the past eight years. The building automation system (BAS) dat
41、a for the primary mechanical plants on campus are readily available in elec- tronic format. Facilities personnel have been most helpful in sharing information regarding load control strategies, utility rate information, and personal experiences with load aggrega- tion and deregulation. Site Characte
42、ristics This site consists of 23 buildings, representing just over 2,190,000 fi2, and includes dormitories, offices, laboratories, classrooms, two theaters, a parking garage, a library, and an athletic center. Restricted to a few city blocks, the residence halls are grouped on one end of campus whil
43、e research and laboratory facilities are similarly grouped on the other end of campus. The site is served by nine substations, each with its own meter. In 1998, following electric utility deregulation in Penn- sylvania, this site sought to reduce overall energy costs. The university experienced an a
44、verage monthly load factor as high as 0.70 and had a favorable electric usage profile on a diurnal and seasonal basis. Historically, this was because the north end of campus, primarily residence halls, dominated the university demand in winter while the south end of campus peaked during the summer m
45、onths. These characteristics made this university campus a target for load aggregators who offered a decreased rate for power generation and supply to university officials if they would sign a supply contract for up to three years. The university declined, assuming correctly that it could shop for a
46、 better rate on its own than what the load aggre- gators could offer as part of a larger portfolio. In the end, the university found it better to negotiate an agreement with its local distributor and an independent competitive supplier. An aggregate billing arrangement was implemented that took adva
47、ntage ofthe fact that each zone peaks at a slightly different time of day. Building Operations and Dynamics With its rate structure and utility information fixed, the facilities manager then focused on how to change building operations and dynamics to take full advantage of the oppor- tunities prese
48、nted by aggregation. Various load control strat- egies using an already available BAS have been initiated to further augment the savings from the long-term billing agree- ment. This resulted in approximately an additional 10% reduc- tion in the total annual electric energy cost. These measures inclu
49、de HVAC equipment replacement, curtailing of non- priority loads, changing of operation setpoints for chiller and AHU operation, alternate fuel selection, an energy-efficient lighting program, and even pre-cooling in the several univer- sity buildings. In the library building, the mass of the building and library stacks is cooled to below comfort levels so that as occupants and equipment warm the building into the after- noon, less cooling capacity is required to maintain design temperatures. It was estimated by the facilities manager that this active pre-cooling scheme saved about $25
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