OPPORTUNITIES WITH NEW TECHNOLOGY

For energy performance truly to be optimized, proven energy-saving measures need to be augmented with newer technology. Two technologies that apply well to existing buildings are:

• Building management/automation

  With a modern, integrated building-management/automation system, continuous optimization is possible. Such a system knows the set points and tolerances of all equipment, which it continuously monitors, alerting operators of problems. This allows operators to continuously fine-tune a building, realizing extra energy savings.

• On-site renewable energy

  Combining a renewable energy source, such as biomass, geothermal, solar, or wind power, with an overall energy-efficiency strategy can be an elegant solution to high energy costs, uncertainty of energy supply, and the need to reduce greenhouse-gas emissions. Consider, for example, a biomass-gasification plant covering 85 percent of a university's energy consumption (see “Biomass-Gasification Plant” sidebar) or a geothermal heat pump and an in-floor radiant heating and cooling system in a “net-zero”-energy building (see “Net-Zero-Energy Building” sidebar). Creative solutions such as these can be implemented with available technology. Plus, there are organizations capable of taking responsibility for the design, engineering, installation, commissioning, operation, and maintenance of renewable-energy solutions.

Chiller-Driveline Retrofits

Equipping an older chiller with a new compressor-motor driveline while retaining the heat-exchanger shells is uncommon, but merits consideration under any of the following circumstances:

• Chiller capacity exceeds the maximum building load

  Downsizing a compressor driveline to match chiller capacity to actual load would result in more-efficient operation. If retained, the now-oversized heat-exchanger shells would provide greater heat-transfer-surface area, further increasing chiller efficiency.

• The chiller is aged, and maintenance costs are escalating

  Because of the number of maintenance-intensive parts involved, a new compressor-drive system can upgrade a chiller plant significantly — and at less cost than a completely new chiller system. For example, some new compressors eliminate oil management from chiller operation. Additionally, the new modern control center that generally is part of a driveline retrofit may include a variable-speed drive.

• The equipment room is not easily accessible

  Removing an older chiller from a sub-basement or other difficult location may require extensive work, including partial building demolition and reconstruction. New driveline components usually can be delivered through standard doorways.

Biomass-Gasification Plant

At the University of South Carolina, where energy is one of the largest annual budget items, the escalating price of natural gas had university planners concerned. From that concern came plans to develop a world-class biomass-gasification cogeneration plant that would furnish steam and electricity fueled by local wood-product waste.

The plant was one of 18 projects recommended as part of an audit of energy- and water-saving opportunities on campus. After the university reviewed and prioritized the opportunities, the plant construction was bundled with the other priority projects into a performance contract. The $19 million investment in the biomass project will be paid back over 14 years.

The integrated gasification-based system will reduce the university's use of natural gas by almost 390,000 dekatherms and produce 302 million lb of steam a year. It not only will provide energy, it will reduce harmful greenhouse-gas emissions. Another benefit of the project is that it will provide the university's engineering department with a hands-on laboratory for students to study and optimize this alternative fuel technology.

Net-Zero-Energy Building

When Integrated Design Associates (IDeAs) Inc., a consultancy providing electrical-engineering and lighting-design services, bought a 7,200-sq-ft former bank building in San Jose, Calif., to serve as its new headquarters, David Kaneda, principal, saw an opportunity to bring the concept of a zero-energy building to life.

“We felt we should walk the talk, not just talk,” Kaneda said.

The goal was to transform the 1960s-era, windowless concrete structure into a highly efficient and comfortable building using a full complement of sustainable-design techniques and technologies. The result is a building that:

• Uses renewable energy to meet 100 percent of its energy requirements.

• Burns no fossil fuels.

• Produces zero net greenhouse-gas emissions.

The building's HVAC system was designed to maximize performance, energy efficiency, and indoor-air quality while keeping construction costs comparable to those of more traditional designs. The energy efficiency of the HVAC system and building envelope is estimated to be 40-percent below 2005 California Title 24 requirements.

The HVAC design incorporates a geothermal heat pump, which takes advantage of the fact that the temperature below ground remains constant year-round — about 50°F in this case. Water flows through pipes laid under an open-landscape area and enters the building, where a heat exchanger collects heat from the water during winter and uses the cooling effect of the water during summer. A radiant floor system with cross-linked-polyethylene (PEX) counterflow tubing uses the water to convey heating and cooling. The system uses less energy to provide the same level of comfort as traditional forced-air systems because of the temperature variance between the occupant and the floor. Radiant systems typically can use higher-temperature water to provide effective cooling and lower-temperature water to provide effective heating, meaning equipment operates at higher efficiency levels.

“Since the system has been operating, it has already provided a very cool and comfortable environment during some very hot weather,” Kaneda said. “It is a very efficient system that will help us meet our net-zero-energy target.”

A building-management system accurately controls flow rates and slab temperature to enable maximum performance using the least energy. Pumps are kept at their lowest demand speed using power-inverter technology. Floor condensation is monitored; if needed, dehumidification is provided by the air handler, which uses chilled water and condenser water for temperature control via a pair of dual coils.

The building receives its energy from a photovoltaic system, the panels of which are part of the single-ply-membrane roof. The electrical system is tied into the grid, drawing power at night and sending excess energy back to the grid during the day. The result is “net-zero” energy use.

To reduce the amount of energy used for lighting and to take advantage of available daylight, Kaneda's team added windows and skylights. High-efficiency windows block infrared and ultraviolet light, which helps to keep the office cool. South-facing windows are shaded by an overhang, while east-facing windows incorporate electrochromic window glazing. Low-energy fluorescent bulbs used throughout the building either are controlled by occupancy sensors or use dimming ballasts. Sensors turn off select lights when daylight is sufficient.

Energy conservation extends to computers and office equipment as well. Flat-screen liquid-crystal-display monitors are used in place of traditional monitors, which use 50-percent more energy, while laptop computers are used in place of desktop computers where possible. Office equipment is integrated with the building security system, automatically shutting down when the security system is armed.

“All of the technologies we are using are readily available,” Kaneda said. “Some of them are more expensive from a first-cost standpoint, but the reduction in energy use will pay long-term dividends. And, it's the right thing to do from the standpoint of reducing our impact on the environment.”

MORE ABOUT THE MECHANICAL SYSTEMS

Additional facts concerning the IDeAs headquarters building's mechanical systems:

• High pumping efficiencies are achieved with a low-pressure-drop piping system coupled with open-port ball-type control valves.

• The electric water-source heat pump has a cooling energy-efficiency ratio of more than 19.

• The PEX piping is buried 6-ft and 4-ft deep.

• When outside air is too cold or too hot for the operable windows and doors installed throughout the building to be utilized, a dedicated outside-air handler with high-performance filtration and constant temperature control provides the required ventilation.

SUMMARY

Global and regional climate-change policy will continue to drive energy efficiency. Green-building practices can be applied to optimize all types of existing facilities. Achieving continuous optimization requires a combination of proven energy-efficiency strategies and new technology, including monitoring and control capabilities and clean energy via on-site renewable-energy sources. The technology is readily available, and the improvements can pay for themselves. Performance contracting is an effective approach, as it can help achieve the scale necessary to address climate change while offering a proven model for financing significant energy-saving projects.

For past HPAC Engineering feature articles, visit www.hpac.com.

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David Clark is vice president of North American systems sales for Johnson Controls Inc. He has more than 20 years of building-automation experience.

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