>> The Pennsylvania State University, Steam Demand Limiting Study
Location: State College, PA
Firm: Abacus Engineered Systems
Role: Lead author of the study, cost estimating, energy analysis, financial analysis
Synopsis: Penn State has a firm boiler capacity of 470,000 lb/hr, at 250 PSIG and 530 deg F, and an estimated distribution capacity of 382,000 lb/hr. On cold winter mornings, steam demand comes very close to exceeding production capacity, distribution capacity, or both. These five to fifteen “worst case” case peaks per year increase in size as the campus grows. At the current rate of campus growth, demand is expected to begin exceeding capacity in the winter of 2005-06, or 2006-07 at the latest. This is forcing the timing on Penn State’s planned replacement steam plant and associated distribution, estimated to cost in excess of $100,000,000. Abacus was commissioned to perform a demand limiting study, to see if the worst case steam peaks could first be predicted, and then, widened and flattened, clipped, reduced, shifted in time, or some combination thereof. The goal of the study was to propose and prove, through financial and technical analysis, a series of measures that would allow Penn State to put off the building of the new plant by ten years. The study was divided into two parts; 1) production and distribution, which I performed, and 2) building end-use, produced by my co-author.
> The study proposed a series of ECMs and Demand Management Measures (DMMs). The DDMs included measures increase capacity, as well as to decrease peak load. Among the DMMs were new, more efficient steam turbines to produce saturated steam at a higher backpressure than the existing units (which do not remove all of the superheat). The higher efficiency would increase the electrical output by almost 100 percent; the higher backpressure would lower the specific volume of the steam, increasing the carrying capacity of the piping. In addition, it was recommended to hook the 680 BHP steam turbine driven ID fans to new motors in addition to the turbine drives. This again lowered the specific volume of the output steam, at a time of year (winter) when the electrical peak is minimal. As a side benefit, it would allow Penn State to switch the ID fans to motors in the summer, diverting that steam to the main turbines at a time when they commonly have to vent low pressure steam to atmosphere to keep the main turbines on line. A new, 100,000 lb/hr boiler was also recommended, to increase steam output – this boiler would remain in place as a backup even when the new plant was built.
> The recommended measures were estimated to cost $22,000,000 to install, and to save $10,000,000 over the ten year period of the study. The opportunity cost of not having to build the plant for another ten years was estimated at $30,000,000, putting Penn State $18,000,000 ahead in year 10.
Synopsis: The final report was submitted in January 2005; it is under review.
>> Providence St Peter Hospital, Boiler and Chiller Plant Mods, Heat Recovery
Location: Olympia, WA
Firm: Abacus Engineered Systems
Role: Energy audit, mechanical design, project management, financial analysis.
Synopsis: PSPH is a 702,000 sq.ft. tertiary care hospital. Building steam was provided by 25 year old watertube boilers that cycled heavily in summer. The DA was non-functional, the chemical feed system was antiquated, and the boiler feedwater pumps cavitated. The plant had no meters, and the building gas meter served more than just the plant. There were no baseline energy numbers for the plant operators to use, and no easy way to create them. The Hospital requires a small but significant amount of chilled water at 44 deg F 8,760 hours per year; prior to the project, this need was served by a 550 ton centrifugal chiller, again, cycling heavily. A single 1,100 ton cooling tower served both chillers, creating a redundancy/reliability issue. All pumping was constant volume. The main 100 percent outside air AHUs had no heat recovery, and, in an effort to save static pressure on the larger fans, they were piped with four pipes to the unit, but only two to the coil (which then functioned as either a heating or cooling coil, eliminating one coil). The two-position, three-way valves which controlled the local switchover from heating to cooling were leaking, false loading either or both systems. The Plant controls were pneumatic, or obsolete DDC controls.
> Abacus installed new meters on gas, steam, chilled water, chiller power/energy, and boiler and cooling tower make-up. Baseline energy consumption was established and used as a benchmark for further work.
> New burners and burner controls were retrofit onto the boilers; they no longer cycle.
> A new DA, chemical feed system, and feedwater pumps were installed.
> The chilled water system was converted to variable-speed primary-only pumping; in order to make this work, all of the heating/cooling cross-overs had to found and eliminated.
> A new air-cooled process chiller was added for winter process load. Two-way isolation valves were placed in the coil piping at all space-cooling units to prevent them from bypassing chilled water into the return system in the “process” mode. Flow limited was added at all end-users.
> New AHUs were installed, with heat recovery.
> Shutdowns were limited to two for the heating system, and one for the cooling system. No surgeries had to be rescheduled, and no patient complaints resulted from the shutdowns.
Synopsis: The plant has been running since 1998; gas prices have tripled since the plant was completed, and the Hospital has added square footage in that time also. Operating costs are only now in 2005 reaching the level they were at prior to the project.
>> Hiram G Andrew Center, New Boiler Plant and Steam Turbine
Location: Johnstown, PA
Firm: Abacus Engineered Systems
Role: Energy audit, mechanical design, lead engineer, financial analysis.
Synopsis: HGAC is a Labor and Industries facility housing and training developmentally and physically handicapped people in a 500,000 sq.ft. building. It was built in 1954, and the three coal-fired boilers were original, as was all the associated coal transport and other balance-of-plant (BOP) equipment. The building also contained one wing of Hospital (Group I Occupancy), and is inhabited 8,760 hours per year. At the time the project began, one boiler was permitted to run only in emergencies (thin tube walls), and parts for the boilers and BOP equipment were increasingly hard to come by. Perhaps for future expansion, or for other reasons, the steam piping was oversized for the loads. For the most part, steam was not used for heating; instead it was converted to hot water for distribution. This steam to hot water conversion took place locally, in over 18 separate mechanical rooms. The facility also 1,000 tons of absorption chilled water capacity – peak steam load actually occurs in summer, when these single stage units fired up.
> Abacus designed and a new boiler plant, including two new 600 BHP, 300 PSIG, gas/oil boilers, operating at 270 PSIG. This pressure is reduced through a 500 kW backpressure steam turbine-generator set to produce electrical energy.
> In the winter, the backpressure is set at 8 PSIG, and monitored at the most remote mechanical room to ensure at least 5 PSIG at heat exchanger. The key to winter operation is the oversized piping, which allows distribution at very low backpressure. This measure eliminated over 18 pressure reducing stations (the steam is distributed at end-use pressure), and the associated safety relief valves, and many of the steam traps associated with the PRV stations. This is a significant reduction in maintenance burden.
> In summer, the turbine backpressure is set at 13 PSIG to ensure that the absorption chillers can meet the required capacity.
> Steam shutdowns were limited to one, and scheduled such that the tenants were unaware it.
Synopsis: The plant has been running since 2002; energy savings in the remainder of the building have exceeded expectations, thus turbine output has been lower than expected. However, the savings in oil/gas costs due to greater than expected building energy savings exceed the projected turbine output savings by an order of magnitude. The largest single-day output of the turbine to date has been 10 MWh.
>> University of Pittsburgh Medical Center - Shadyside, Chilled Water Study
Location: Pittsburgh, PA
Firm: Abacus Engineered Systems
Role: Lead engineer, lead author.
Synopsis: Shadyside is the largest of the 18 hospitals in the UPMC system. The total installed chilled water capacity is 8,000 tons. The distribution system was intended to be primary/secondary/tertiary; the primary loop is constant volume, the secondary loop is variable volume, and the tertiary systems include some of both. Over the years the system was added to by many engineers using differing techniques. The result is that in many instances, two or even three sets of pumps are in series. Many different schemes for controlling the interfaces between the loops were also implemented with various results. Most of the loop interface controls are now in operator priority; in effect being operated manually. There is no flow limiting on the system, and low plant delta T is an issue – chillers are frequently turned on not to provide capacity, but to provide flow.
> Phase I of the study documented the physical condition of each secondary/tertiary loop interface. The control hardware, software, and sequences for each bridge were documented as well. The intent is to standardize control and introduce flow limiting.
> Phase II will concentrate on the primary circuit, and automating chiller staging.
> Phase III will attempt to eliminate one level of piping and pumping.
> Once the distribution system is operating properly and at minimum energy, major energy savings can be realized at the Plant and at the end-use devices.
Synopsis: Phase I has been submitted and is under review.