Technical Articles and Books

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Our technical team continues to make significant
contributions to the field of energy systems design.

Sustainable Thermal Storage Systems
Planning, Design and Operations
Book written by Lucas B. Hyman  P.E., LEED-AP,
Co-Founder, Goss Engineering, Inc.
Published by McGraw-Hill, 2011.

Sustainable On-Site CHP Systems
Design, Construction and Operations
Book co-edited by Lucas B. Hyman  P.E., LEED-AP,
Co-Founder, Goss Engineering, Inc.
Published by McGraw-Hill, 2009.

Commissioning Chilled Water TES Systems
from Engineered Systems Magazine, 2004

The Facts on Protecting Art and Artifacts
from Engineered Systems, January, 2006

Thermal Tracking CHP and Gas Cooling
from Engineered Systems, 2005

Overcoming Low Delta T
from ASHRAE Journal, February 2004

Primary Chilled Water Loop Retrofit at UC Irvine
from ASHRAE Journal, December 2000

Designing Sustainable On-Site CHP Systems
from January 28, 2007 ASHRAE Meeting

 

The Facts on Protecting Art and Artifacts

from Engineered Systems, January, 2006

full article pdf

Designing a museum HVAC system requires a solid understanding of how to best maintain various conditioned space requirements consistent with known local microclimate variability and the preservation needs of the contents of the museum’s collections.

Above all, when selecting among the various HVAC systems and operating control strategies available, HVAC designers must carefully consider their combined environmental impacts on valuable collection contents ranging from historical artifacts and irreplaceable rare books and documents, to artwork, specimens of natural history, and much more.

MUSEUM DESIGN CONSIDERATIONS

Eight indoor environmental design issues can threaten collections, thus requiring the attention of MEP engineers and their architect clients: light, rh, temperature, air quality, shock, vibration, pest/mold infestation, and potential MEP system failures. …

more: full article pdf

 
Thermal Tracking CHP and Gas Cooling

from Engineered Systems, 2005

full article pdf

Fully dedicated on-site combined heat and power (CHP) systems present both challenges and opportunities for large multi-building projects; particularly when employing a combined cycle approach in the 3 to 20 MW range.

While some distributed power generation systems hedge their bets through reliance on both the sale and export of power (e.g., paralleling with a serving utility to achieve favorable economics), disappointing de-regulation benefits and the failure of energy trading to smooth out power supply vs. demand cost uncertainty has been a sobering experience for many customers.

Recent rethinking by concerned CHP designers has focused on exploring smaller footprint alternatives to the use of higher cost heat-recovery steam generators (HRSGs). One such approach involves use of prefabricated and fully integrated steam generators. These units come complete with associated heat exchangers, controls, and pumping systems employing low pressure, non-volatile, recirculating heat transfer fluids (HTF) capable of direct heat extraction of turbine exhaust gas waste heat to generate steam and allow cascading of the remaining captured waste heat to drive absorption chiller(s). They also include space and domestic hot water heating systems enabling greater utilization of available heat reclamation potentials in satisfying highly variable annual building power, heating, and cooling load demands.

Thermal tracking CHP utilization can be optimized through maintaining favorable log-mean-temperature-differentials (LMTDs) at the turbine gas extraction coil, also resulting in a lower exhaust gas temperature discharge to ambient. Various examples of such alternative HRSG cycles will be presented for gas turbine driven chiller and/or generator application, as well as gas turbine combined cycle operation to demonstrate the operational versatility and life cycle benefits of this approach for the above referenced range of commercially available gas turbines. … 

more: full article pdf 

 

 
Overcoming Low Delta T

from ASHRAE Journal, February 2004

full article pdf

By Lucas B. Hyman, P.E., ASHRAE, and Don Little, senior project manager with the Farnsworth Group, Los Angeles.

The University of California, Riverside (UCR) in Southern California is the fastest growing campus in the UC system. The campus has approximately 3 million ft2 (279 000 m2) of assignable facilities, including many science buildings with 100% outside ventilation air. Planning and modifying the campus’ chilled water system has occurred slowly, as resources were available. Unfortunately, those modifications have not always kept up with the campus’ rapid expansion.

Moreover, a lack of enforced chilled water system design standards resulted in many different building interfaces. The resulting problems with the chilled water system included unexpected low, and even negative, differential pressure (Delta P) near the end of chilled water distribution mains, and high chilled water system Delta P near the central plant. The unexpected low and negative Delta P resulted in low chilled water flow and thermal comfort complaints in buildings located at the affected ends of the distribution system. At the same time, high Delta Ps near the central plant forced open control valves, contributing to the central plant experiencing low chilled water temperature differential (Delta T). This resulted in loss of thermal energy storage (TES) capacity, increased pumping energy, and reduced available cooling capacity.

Specific causes of the chilled water problems included:

1. A mixture of constant-speed series tertiary pumps and tertiary pumps with bridge connections;

2. Secondary distribution piping constraints caused the secondary pumps to be inadequate to the task of keeping the distribution system positive;

3. Lack of variable speed drives (VSDs) on the series tertiary pumps;

4. Flow limitations through the TES system which could no longer carry the full peak load;

5. Coils selected for low Delta Ts (10°F to 12°F [5.5°C to 7°C]);

6. Some chilled water bypassing; and

7. Reverse or inoperable controls.

Thermal comfort complaints resulted primarily from a lack of chilled water flow to the buildings experience negative differential pressures. The chilled water systems for the affected buildings were not designed for negative differential pressures (i.e., the chilled water pumps did not have enough head for this condition). The design team developed a multifaceted approach to solve the problems.

Solutions included:

1. Modifying the existing chilled water distribution system to reduce system drops and system constraints;

2. Adding a central plant secondary chilled water distribution pump to increase pumping capacity;

3. Installing, at buildings near the central plant, modulating two-way pressure independent control valves (PICVs) to improve controllability at high Delta Ps and to help prevent chilled water bypassing via forced open control valves;

4. Converting from a full storage TES operational strategy to a partial storage strategy; and

5. Stopping short circuits (bypass of chilled water supply to return), correcting reverse logic on some control valves, and addressing other control deficiencies.

VFDs were not added to tertiary pumps because the campus limited the scope of any actual building chilled water system work. After the modifications were completed, the UCR chilled water distribution system achieved a positive Delta P at the end of the piping mains, achieved cooling thermal comfort in previous problem buildings, and attained a 20°F (11°C) Delta T in the chilled water and TES system. …

more: full article pdf

 

Primary Chilled Water Loop Retrofit at UC Irvine

from ASHRAE Journal, December 2000

full article pdf

By Lucas B. Hyman, P.E., ASHRAE, and

Fred R. Bockmiller, P.E., ASHRAE

[Excerpt]  Before the retrofit work, UCI measured the actual average power kilowatt draw of each of the existing throttled primary chilled water pumps. The annual pumping energy cost for the existing throttled pumps was estimated by multiplying the average measured electric power by the estimated number of annual operating hours by UCI’s calculated annual average cost of electricity ($0.06 per kWh based on SCE’s TOU-8 rate schedule). The estimated energy cost for throttled primary chilled water pump operation was approximately $91,600 per year. One year after the completion of the project, UCI read the operating hours and kilowatt-hours from each of the pump’s VFDs. The average kilowatt draw and the estimated cost of operation was calculated as approximately $14,600. The estimated first-year savings is approximately $77,000. Table 5 and Table 6 provide these findings.

This system has provided UCI not only energy savings and a payback of approximately six years, but also the ability to better control chiller operation. Now, regardless of the campus chilled water return temperature and varying header differential pressures, the central plant operators have the ability to:

  • Keep the chillers fully loaded.
  • Maximize each chiller’s Delta T by setting the minimum evaporator flow rate.
  • Provide the minimum allowable leaving chilled water supply temperature.
  • Easily operate the chilled water plant without complex decisions of how many pumps to run. …

more: full article pdf

 

Designing Sustainable On-Site CHP Systems

January 28, 2007 ASHRAE Meeting

full article pdf (6MB)

By Milton Meckler, P.E.,  Lucas Hyman, P.E.,

and Kyle Landis, P.E.

Sustainable on-site cooling-heating-power (CHP) systems for large multi-building projects require a simplified design and implementation approach from conventionally designed mini-utility type CHP systems employing large volume/footprint, costly, high thermal mass heat-recovery-steam-generators (HRSGs) and 24/7 stationary engineers.

This paper will demonstrate the use of prefabricated, skid-mounted hybrid steam generators with internal headers, fully integrated with low pressure drop heat extraction coils located in the gas turbine exhaust, and employing environmentally benign heat transfer fluids.  The proposed thermal tracking Integrated CHP Gas Cooling System (ICHP/GCS) includes close coupled plate and frame heat exchangers, pumps, and self-regulating controls, interconnected via a closed, low-pressure, non-volatile recirculation loop capable of efficient, year-round transfer to on-demand HVAC&R building heat sinks including absorption chillers.

Available waste heat is transferred directly to a gas turbine exhaust extraction heat exchanger, interconnected to a recirculating, closed circuit, non-volatile, low-pressure heat transfer fluid loop.  Available waste heat is cascaded to serve multi-building space cooling, heating, and domestic hot water loads, which permits maintaining high log-mean-temperature-differentials (LMTDs) at the subject extraction coil, significantly lowering gas turbine back-pressure, and permitting significant life-cycle-cost savings.  These benefits were demonstrated during a recent, comparative CHP study of a 3.5 MW gas turbine installation at a central California university campus. …

more: full article pdf (6MB)

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