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Green Energy Services - Commercial - High Efficiency Systems

Sustainable Design Protects Our Environment

Energy costs are constantly escalating and clients are concerned about reducing their carbon footprint and the impact they have on the environment.

High efficiency commercial HVAC systems are a combination of high efficiency equipment selection, sustainable system design and high quality installation practices along with a measurement and verification of the system operation. Even if your project is not seeking LEED certification we always include cost effective high efficiency measures in our designs. Please review our Design Build Contractor of the Year Award.

Introduction
Sustainable HVAC (heating, ventilation and air conditioning) refers to the equipment, distribution network and terminals that provide heating, ventilation and/or air conditioning to a building. HVAC accounts for 40% to 60% of the energy used in commercial and institutional buildings, and 12% to 15% in industrial facilities. This represents an opportunity for substantial energy savings using proven technologies and design concepts. A recent study estimates that California commercial businesses alone have the potential to save 46% of their energy costs through cooling and ventilation energy efficiency efforts by 2011.

Technology Options
HVAC systems are typically replaced or upgraded when they have reached the end of their useful life. Because HVAC systems are expensive, it may not be cost-effective to replace them on the basis of improved performance or estimated annual energy savings alone. To optimize the purchase and selection of these systems, perform an energy analysis and review the purchasing tips provided below.

When early retirement of the HVAC system is not an option, there are two general guidelines for improving the energy performance of existing HVAC systems:


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  • Make the system as efficient as possible.
  • Control the system as efficiently as possible.

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Routine maintenance of an HVAC system should be performed at least annually. Inspect motors, belts and steam traps, and rebuild or replace them as necessary. Filters should be replaced, dampers adjusted to ensure a tight seal, and linkages, boiler heat transfer surfaces and coils should be cleaned. Other low-cost improvements to improve your HVAC unit's efficiency include:


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  • Install tight-sealing, insulated dampers. The outside air and the exhaust dampers should have edge and jamb seals. The damper between the return air duct and the outside air duct should be tightly sealed.
  • Insulate duct system. Supply ductwork and ductwork that is exposed to outside air — including the mixed air duct, exhaust duct and outside air duct — should be insulated.
  • Seal duct joints. Duct joints should be sealed with mastic.
  • Balance air-handling systems. Air-handling systems should be balanced so that each zone receives the design air flow. The returns registers should also pull as much as air back as is supplied.
  • Control ventilation to match occupancy of facility/building. Heating and cooling of outside air prior to its delivery to occupied spaces should be controlled to match the occupied hours of the building.
  • Control heating to match occupancy of facility/building. During unoccupied periods, the heating temperature can be reduced by 10°F to 15°F.
  • Adopt an "optimal start" strategy. Many systems are controlled by a time clock or an energy management system to begin regular operation. An optimal start strategy utilizes a database and outside temperature measurements to determine when the system should resume heating or cooling.
  • Control the air-handling unit to match occupancy of facility/building. Program the air-handling unit to cycle off during unoccupied periods.

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More extensive and expensive system improvements can be considered as well, such as:

 

 

  • An Economizer: An economizer system uses large quantities of outside air to meet the cooling load rather than operating the mechanical cooling system. This involves providing the following: additional controls to evaluate outside versus indoor air, ductwork to allow up to 100% outside air to be brought into the building, and an exhaust or relief fan.
  • Variable Air Volume: A variable air volume (VAV) system maintains a constant supply air temperature and varies the amount of air delivered to each space. Therefore, spaces requiring less cooling receive less airflow, while those requiring more cooling receive greater airflow.
  • Heat Recovery: Heat recovery is a general term relating to the useful application of heat that normally would be wasted or exhausted from a building. Heat recovery is often cost-effective in industrial facilities, but is not usually cost-effective in commercial buildings because of the low temperature and small quantity of exhaust from them. One exception is commercial or restaurant kitchens, where exhaust from the kitchen often can be used for heat recovery.
  • Thermal Energy Storage (TES): TES systems are ice-making systems that are employed at night to produce ice that can then be melted during the day to provide a chilled-water source for air conditioning. Energy demand is shifted, since the air conditioning load changes from standard hours to late night. In some cases, thermal storage systems actually use more energy than conventional systems, since making ice is more energy-intensive than producing chilled water. However, since the system operates at night (during off-peak periods), this strategy is less expensive when lower off-peak power rates are available.
  • Part-Load Boilers and Chillers: HVAC systems are selected to meet the building's heat loss and gain during the coldest and hottest times of the year. For this reason, individual boilers and chillers tend to be oversized for most of their operating times. Many engineers are now designing systems with multiple boilers and chillers. One unit can be sized for 75% to 80% of the design load, while another is sized for part-load performance, or roughly 30% to 40% of the full load. This allows the operator to select which unit to operate based on energy efficiency performance.

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Efficiency Benefits
Between Pacific Gas and Electric (PG&E), Southern California Edison (SCE) and San Diego Gas and Electric (SDG&E), there is a total of 2432 GWh and 1069 MW of savings potential for cooling and ventilation alone. This is particularly important in terms of peak demand. Energy efficiency measures addressing high-efficiency chillers and packaged units, as well as chiller tune-ups and controls, make up a large share of total potential savings in this area. There also are potential savings from improving the performance of existing package and chiller units through better maintenance and operating practices as described above.

The following table shows savings as a percentage of total commercial sector energy consumption and peak demand for the three utilities across HVAC potential measures, aggregated across market segments and utilities in California.


Levelized

Measures

GWH
Savings

Cumulative
GWH Savings

Energy
Cost $/kWH

Percent
Savings

HE Chiller

478

1,990

$0.017

2%

HE DX

246

769

$120

4%

Prog. T-Stat

46

815

$135

4%

Chiller Pumps

73

1,572

$224

9%

Cool Tune-ups

186

2,394

$372

13%

HE Vent. Motor

28

2,422

$397

13%

Pre-Cooler

95

3,396

$587

19%

Vent. VSD

26

3,422

$596

19%

Levelized

Measures

MW
Savings

Cumulative
MW Savings

Demand
Cost $/kW

Percent
Savings

HE Chiller

315

315

$26

2%

Prog. T-Stat

277

2,616

$0.022

3%

Vent. VSD

453

5,251

$0.034

7%

HE DX

445

9,658

$0.066

12%

HE Vent. Motor

156

9,814

$0.071

12%

Chiller Pumps

110

11,802

$0.148

15%

Cool Tune-ups

308

12,110

$0.225

15%

Pre-Cooler

170

14,444

$0.326

18%

Manufacturers
Some of the largest HVAC manufacturers include:


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Purchasing Tips
When purchasing new equipment, several items need to be evaluated before proceeding. Specify the highest-efficiency boiler, furnace, chiller, air handler and rooftop unit that your budget allows. In determining an acceptable cost limit, take into account the achievable energy savings over the life of the equipment.

Evaluate thermal loads as well before installing equipment, since changes to the building are likely to have occurred since the original equipment was purchased. Downsizing equipment can save substantial energy when replacement cooling or ventilating equipment is needed. Other efficiency measures such as reducing lighting levels, sealing duct leaks, installing low-emissive (low-e) windows and integrating building operations with an energy management system may allow smaller equipment to cool and ventilate your building.

Emerging Technology
Advanced technologies have already demonstrated success in increasing the energy efficiency of heating, cooling and ventilation, without compromising occupant comfort or equipment performance. Yet the opportunity for further energy efficiency improvements remains large. There are several related advances that affect HVAC usage as well, such as cool roofs and evaporative pre-coolers. At this time, costs and savings estimates are less certain for these measures.

One direction pursued by Department of Energy (DOE) research and development is improved performance in chiller systems used in cooling large commercial facilities. Another promising direction is advanced combined, heat and power (CHP) systems that use waste heat to cool and heat buildings, significantly increasing system efficiency. According to DOE officials, integrated CHP systems can offer up to a 30% to 40% improvement in building efficiency. DOE goals for CHP development include helping manufacturers integrate their components into packages and ready them for the marketplace.


 

   
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