NREL Solar Energy Research Facility

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Overview

• Location: Golden, CO
• Building type(s): Laboratory
• New construction
• 115,000 sq. feet (10,700 sq. meters)
• Project scope: 3-story building
• Suburban setting
• Completed October 1993

NREL's Solar Energy Research Facility (SERF) is a research facility used to develop technologies for converting sunlight into electricity. Completed in October 1993, SERF houses approximately 190 employees in 42 laboratories, conducting research on photovoltaic (PV) technology, solar electricity, superconductivity, and related material and basic sciences.

The building consists of three adjoining modules. Each module has a laboratory pod in the back and an office pod in the front. The facility has two main levels and a basement level. A corridor runs through the space between the labs and the offices, enabling researchers to move from lab to lab without entering the area occupied by other staff members.

Environmental Aspects

When it was designed in 1992, SERF's annual energy costs were predicted to be 30% lower than a 10CFR435 (federal) reference case. Today (based on data collected in 2002), its energy use is still very close to the 1992 predicted levels. The building has experienced an increase in both occupants and equipment, causing an increase in energy use. However, this was more or less negated through smart retrofits and changes in controls so that the building still operates using approximately 30% less energy than the reference case.

The project's long axis faces a few degrees east of due south to capitalize on sunlight for heating and daylighting. This design allows extensive daylighting in the office. Other environmental features include energy-efficient lighting, direct evaporative cooling, a heat recovery system to pre-condition incoming fresh air, oversized cooling towers to provide indirect evaporative cooling, window glazing and automatic controls, and a Trombe wall.

Owner & Occupancy

• Owned and occupied by U.S. Department of Energy, Federal government

• Typically occupied by 200 people, 40 hours per person per week

The SERF is most heavily occupied during normal office hours (8:00 a.m. to 5:00 p.m., Monday through Friday.) However, researchers sometimes use their labs late at night. This use varies by project, so it is hard to give an accurate estimate of after-hours usage of the building.

Building Programs

Indoor Spaces:	Laboratory (60%), Office (25%), Restrooms (5%), Conference (5%), Dining (5%)
Outdoor Spaces:	Wildlife habitat (85%), Parking (10%), Drives/roadway (5%)

Keywords

Integrated team, Design charrette, Simulation, Performance measurement and verification, Open space preservation, Wildlife habitat, Indigenous vegetation, Drought-tolerant landscaping, Massing and orientation, Insulation levels, Glazing, Passive solar, HVAC, Lighting control and daylight harvesting, Efficient lighting, On-site renewable electricity, Adaptable design, Recycled materials, Occupant recycling, Daylighting, Natural ventilation, Ventilation effectiveness, Moisture control, Thermal comfort, Noise control, Indoor air quality monitoring

Team & Process

From the outset of the project, sustainability and energy efficiency were defined as goals for the building. A nine-step energy design process that uses building energy simulation and economic analysis was followed from pre-design through construction.

NREL solicited an A/E firm with a reputation for lab design as well as expertise in passive solar design concepts and energy efficiency. NREL also assembled an outside group of experts on energy-saving design techniques to advise the A/E. As a first task the design team devised a set of energy-design guidelines for SERF and used energy simulation as a tool in the design process.

Representatives from NREL’s Center for Building and Thermal Systems provided input throughout the energy concept development process. The A/E team hired both a daylighting consultant and an energy consultant. The initial design concept was tested using a series of physical models. The largest model of the office pod was approximately four feet square, and it was used for video and photography studies under natural lighting conditions. Full-building energy modeling was used to integrate the results of the daylighting with hourly simulations using the DOE-2 program.

An additional design concern was the control of luminous ratios on the major surfaces in the visual field. To control the luminance from the clerestory and east and west windows, glazing was selected with specific visual transmittance values.

A study of the SERF daylighting design was initiated in the summer of 1997 to evaluate the visual and energy performance of the system, because most of the lighting circuits were on continuously during sunny periods. The emergency circuits were rewired to reduce the number of lamps in the circuit and to turn them off when daylight is adequate. The location of the occupancy and light sensors was also a problem. Because they were located about three feet above the floor along the east and west walls, several sensors were hidden by office furniture.

SERF staff performed an Assessment of Load and Energy Reduction Techniques (ALERT) audit through the DOE Federal Energy Management Program in 2002 to identify modifications to operation that could save energy. In 1997 and 2000 energy audits were also performed to look for measures to save energy. These audits included running new DOE-2 simulation models.

As part of the study of the daylighting system, the east office pod was monitored for a week in each of June, September, and December 1997. During this time period, a post-occupancy evaluation survey was given to the people working in the SERF building. When asked to rank the most important environmental feature in their workspace, the SERF occupants selected “good lighting.”

NREL installed four electric meters at the SERF in 2002 – one for each pod (West, Center, and East) and another for the Energy Center, where HVAC equipment is located. The building also has one gas meter.

• DOE-2 version 2.1d energy modeling software.

Jack DeBartolo Anderson DeBartolo Pan, Inc. Architect (Energy and daylighting design) Tucson, AZ

Will Brown Anderson DeBartolo Pan, Inc. Architect (Energy and daylighting design) Tucson, AZ

Steve Ternoey, IESNA LightForms Lighting designer Boulder, CO

Ron Judkoff National Renewable Energy Laboratory Energy consultant (Energy and daylighting design (Resaercher)) Golden, CO

Pete Jacobs Architectural Energy Corporation Energy consultant Boulder, CO [http://www.archenergy.com](http://www.archenergy.com)

Ed Szydlek National Renewable Energy Laboratory Owner/developer (Building engineer) Golden, CO [http://www.nrel.gov](http://www.nrel.gov)

Finance & Cost

The project was funded by a congressional line item.

• Equity: Government appropriation

Cost data in U.S. dollars as of date of completion.

• Total project cost (land excluded): $19,600,000

The project cost was $19.6 million for design and construction (about $170 per square foot). This cost is low, even in 1992, for a typical research facility.

During the design process, life-cycle costing was done for a series of energy-efficiency measures. The measures recommended for implementation included: daylighting, direct evaporative cooling, indirect evaporative cooling, high-efficiency motors, variable frequency drives, energy-efficient lighting, and upsized cooling towers. The simple payback for these measures ranged from a low of 1.4 years for daylighting to a high of 8.9 years for upsized cooling towers. By employing all of these recommended technologies, the annual cost of energy decreased by $171,168 or 30.3% compared to a 10CFR435 reference case.

Site Description

The building was constructed into a gently sloping southern hillside with no solar obstructions.

• Lot size: 538,000 ft2
• Building footprint: 65,600 sq ft (6,090 sq meters)
• Previously undeveloped land

Water Conservation and Use

Water use was studied in 2002. Total water use was found to be 4,965,500 gallons per year. According to the study, 39% of that water was used for the cooling tower, 25% was for evaporative cooling, 9% was used in bathrooms, and 1% was for irrigation. Fully 25% was unaccounted for.

Water Use -

Indoor potable water use: 4,920,000 gal/yr
(18,600,000 liters/yr)

• Outdoor potable water use: 49,700 gal/yr (188,000 liters/yr)

• Total potable water use: 4,970,000 gal/yr (18,800,000 liters/yr)

• Potable water use per unit area: 43.2 gal/sq ft (1,760 liters/sq meter)

• Demand for Irrigation

  • Select plants for drought tolerance

• Site Planning

  • Provide for solar access

Energy

Based on actual energy use collected in 2002, the SERF uses 6,018,557 KWh of electricity and 207,990 therms of gas per year, for a total cost of $316,089. This works out to 357 kBtus or $2.72 per square foot annually.

Because the SERF is a laboratory building, it is energy intensive, requiring 12 air changes per hour in the labs. Of the total electricity use, 37% is for ventilation, 30% is for cooling, 7% is for lighting, and 26% is for process and plug loads.

The original simulation, done in 1991, projected total energy costs for the reference case at $565,130 and for the as-designed case (at 90% design) at $383,893. In 1997 and 2000, the as-designed model was calibrated and re-simulated. The 2000 simulation for the as-designed building predicted energy costs of $314,591, which is close to the actual energy costs in 2002 of $316,098. Over the last ten years, the building has experienced load growth through both more people and increased equipment. This load growth has been offset by smart retrofits and changes in control strategies.

Utilities are distributed to the lab portion of the building via a service corridor. This scheme allows labs to be more easily reconfigured than if utilities were distributed above a suspended ceiling or vertically behind walls and doors.

 

Lessons Learned

NREL believes it is important to understand what is driving the energy use in buildings and the relative sizes of various loads. For this reason, it is important to meter, and preferably submeter, building energy use.

Simulation tools allowed us to identify ventilation as the main driver of energy at the SERF, but we overestimated the equipment loads by a factor of two. This had a cascading impact on the size of heating and cooling equipment as well as ducts and pipes.

Energy recovery in labs makes good economic sense. We designed the SERF with a constant-volume air distribution system using reheat. However, a variable-air-volume (VAV) system would have been more efficient and cost effective.

Learn More

It is possible to visit this project and tours are available. NREL provides public tours of the SERF periodically. Persons interested should see the "Visit NREL" page of the NREL Web site.

Jim Bosch (Tour Contact) National Renewable Energy Laboratory 1617 Cole Blvd. Golden, CO  80401 303-384-6567 [http://www.nrel.gov](http://www.nrel.gov)

• Web sites

  • Solar Energy Research Facility: National Renewable Energy Laboratory

    This Web site offers a thorough technical description of the Solar Energy Research Facility.

• Others

  • Brochure: The Solar Energy Research Facility (June 2001)
    Part of the U.S. Department of Energy's "Highlighting High Performance" series, this brochure is available online in PDF form. (PDF 559 KB) Download Acrobat Reader

*Primary Contact* Paul Torcellini National Renewable Energy Laboratory 1617 Cole Blvd. Golden, CO  80401 303-384-7528