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Desert Living Center Exhibits Arid Green

Credits: ©2011 Las Vegas Springs Preserve

The Desert Living Center (DLC) is a 46,000-square foot environmental education complex that showcases green building methods, materials and technologies for a desert climate, including straw bale, rammed earth, and cooling towers that lower heating and cooling energy use. The designers - Lucchesi Galati Architects of Las Vegas – incorporated many sustainable features into the DLC, such as a roof built with recycled railroad trusses; orientation to maximize solar for heat and light using passive design principles; stormwater collection and reuse to irrigate gardens; walls insulated with shredded blue jeans; minimal mechanical systems; daylighting ; towers for evaporative cooling; and solar panels covering parking areas. The DLC won the award for Best Public Green Building Project in Nevada in 2007. The five DLC buildings are part of the Las Vegas Springs Preserve, a 180-acre park that features a 1.8 mile trail system with interpretive overlooks, historic structures and archaeological sites; an eight-acre botanical garden with thousands of native and drought-tolerant plants, outdoor classrooms and a cooking demonstration area, and an accessible garden; the Cienega desert wetland that serves as a home for hundreds of native plant, bird and animal species; and a reconstructed cauldron pool depicts the natural springs that once bubbled from beneath the valley floor. (Scroll to bottom for additional resources)


Springs Preserve Solar Panels

The Springs Preserve uses photovolatics to shade a parking area on its 180-acre site that includes the Desert Living Center in Las Vegas. ©2008 J. Siegel Designs

Sustainable features at the Desert Living Center include:

Sustainable Sites: Bike racks and alternate fuel vehicle parking are provided. Light-colored roofing and paving reduce heat islands. More than 60 acres of desert and wetlands have been restored on site. All lighting is designed to reduce light pollution.

Water Efficiency: Irrigation systems are water-efficient. Black and gray water is treated and reused onsite. Waterless urinals and water-efficient fixtures are used throughout.

Energy & Atmosphere: Mechanical systems achieve a 40 percent to 50 percent reduction in energy use and are free of HCFC's and Halons. Photovoltaic power and solar water heating are used to reduce grid dependence.

Harris Consulting Engineers provided provided complete HVAC, plumbing and electrical design.

Materials & Resources: Building materials use recycled content and are locally sourced. Materials also are of rapidly renewable crops and from certified sustainable forests. Recycling collection bins are placed onsite.

Indoor Environmental Quality: All indoor materials and coatings meet VOC limits. Individual occupants can control lighting and operable windows, and all regularly occupied spaces provide daylight and views.

DLC Solar System Is Part of Larger Las Vegas Project
In its efforts to create a more sustainable community, the Las Vegas Valley Water District (LVVWD), owner of the Springs Preserve and DLC, built solar power generating systems at the Springs Preserve along with six other facilities. The entire 3.1 megawatt photovoltaic solar energy project is one of the largest ever built by a public agency in the United States. Its Distributed Solar Array systems generate approximately 5.3 million kilowatt-hours of clean electricity per year without impacting water district rates. The electricity generated by the solar arrays supports onsite operations, including pumping operations and water-treatment processes. The solar panels at the Springs Preserve have dual functions to provide shaded parking over the parking area that is actually the roof of the reservoir; and the shade structures’ photovoltaic cells generate power. In its efforts to use renewable energy, the Springs’gardens also use a fleet of hydrogen powered utility vehicles. The vehicles are refueled on site by a solar powered hydrogen fueling station.

The following article describes the innovative combination photovoltaic/fabric power system that also shades parking spaces.
By Craig G. Huntington, Fabric Architecture, March 2008
Green Car Park’s Photovoltaic System Incorporates Fabric

Fabric complements the sustainably-inspired photovoltaic system at Springs Preserve, Las Vegas
The high reflectivity of architectural fabrics has long been used to minimize heat gain in buildings constructed in warm climates. At Las Vegas Springs Preserve, this same high reflectivity is employed to bring more daylight to overhead photovoltaic arrays and substantially improve their energy production. Springs Preserve, located at the site of the original spring where Las Vegas was born, is a public visitor center with displays and events focused on sustainability in the desert environment. Its six new photovoltaic arrays, constructed over grade level parking, provide the center’s most dramatic display of sustainable building technology.

Evolving strategies for photovoltaic performance
The growing market for photovoltaic (PV) arrays has brought with it the exploration of increasingly sophisticated means of supporting and configuring PV panels, as well as greater diversity in siting of photovoltaic arrays. Most are constructed at grade or on building roofs. However, ground mounted arrays consume substantial acreage, reducing the eff ective sustainability of such installations, while the unsuitability of many building roofs to PV array installation limits roof top installation as a means for satisfying the growing market for solar power. Carports are one of several emerging venues for array installation. By using framing to support solar panels overhead of outdoor parking areas, the land becomes “dual use,” and no additional site area is consumed by the solar array.

Consideration of the strategies for optimizing the positioning and orientation of PV panels within an array provides the background for understanding how fabric is used to enhance the output of the arrays at Springs Preserve. Panel orientation relative to the sun strongly influences photovoltaic output, and panels are sloped perpendicular to the direction of sunlight for maximum power gain. Shading of any part of the array critically impacts output, as shading not only reduces the power gain from the shaded panels, but has the disproportionate effect of reducing the efficiency of all of the panels grouped into an electrical string.

Strategies for high efficiency in PV array design must therefore carefully consider panel orientation and shading. The most basic array configuration uses panels that lay flat on grade, rooftop, or supporting structure. These flat arrays may be economical to construct, (and they allow panels to be closely spaced without shading), but their oblique orientation to the sun means that they offer the lowest output per panel. To improve output, some designs tilt the panels towards the south so that the panel slope is a compromise between the ideal slope at the summer solstice (when flat panels are highly efficient) and the winter solstice, (when substantial slope, depending on latitude, may be optimum.) A slope of about 15 degrees provides optimal overall efficiency in moderate latitudes. Space must be provided between the panels in order to avoid shading in certain sunlight conditions, so that tilted arrays may make less efficient use of space than flat arrays.

More advanced arrays are designed as “trackers” that rotate the panels to follow the path of the sun during the course of the day. Whereas tilted panels improve winter PV performance, tracker panels provide improved performance early and late in the day. The most sophisticated arrays employ both tilting and tracking to optimize power output.

Further increases in array power output have been recently achieved through the use of bifacial panels, which are photovoltaically active on bottom as well as top, so that light reflected from the ground or other surfaces below the panels also contributes to power output. The gain associated with bifacial panels is a function of several factors:

• Albedo, a measure of the portion of light striking the surface beneath the panel that is reflected back upward. (Typical albedos range from 0.10 for foliage or asphalt, to 0.30 for concrete, up to approximately 0.80 for snow.)

• Panel spacing. When panels are closely spaced, insufficient direct sunlight passes between the panels for substantial reflection of light on the panel bottom sides to occur.

• Panel height above the reflecting surface. Panels that are too close to the reflecting surface restrict the amount of light that can be reflected to the underside of the panels.

• Obstructions. Framing or other obstructions below the PV panels that cause shading will reduce the efficiency of all panels grouped into an electrical string.

Spacing the panels widely increases the total surface area required by a given number of panels, but wide spacing, in combination with 457.2mm or more of elevation difference between the panels and reflecting surface below, results in the highest output for individual bifacial panel.

Fabrics boost power output
Panel height and spacing, along with obstruction free installation, are geometric considerations critical to maximizing the output from bifacial panels, but a strategy for their effective use must also consider how albedo can be raised to increase the light energy reaching the bottoms of the panels. Here, the high reflectivity of architectural fabrics, which is so useful in reducing building energy use by keeping building interiors cool in sunny climates, comes into play on the production side of the energy equation. At Springs Preserve, tensioned fabric membranes were installed to create a reflective interlayer between the parked vehicles and overhead arrays of bifacial PV panels. The gain in photovoltaic output associated with fabric membranes is primarily a function of the high albedo of fabric relative to that of the typical asphalt or concrete parking lot paving that it replaces as a reflecting surface.*

Springs Preserve has a total of six PV arrays constructed over visitor parking areas to create dual land use. The panels tilt to the south for improved orientation to the sunlight in five of the six arrays. Two of the arrays are designed to track as well, through the use of steel pipe “torque tubes” that rotate the panels from a slope 45 degrees to the east in the morning to 45 degrees to the west in the afternoon. While panels in all of the arrays are bifacial, the two tracker arrays also incorporate fabric membranes installed over the heads of parking area users but below the PV panels. In the four arrays without fabric, the bottom surfaces of the bifacial panels are reliant on the low albedo of the concrete paving. Testing by the panel supplier Sanyo on prototype panels indicate that the bifacial panels have a power output approximately 6 percent greater than that of single sided panels in similar conditions. By contrast, Sunpower’s own testing on prototype panels indicates that bifacial panels over white mesh fabric increase power output approximately 18 percent.

Shaping for economy and efficiency
The need for uniform reflectivity dictated that the fabric be nearly horizontal throughout its surface, as did the need to place the fabric both overhead of the parking and below the array while at the same time avoiding the added expense of raising the elevation of the array. PV contractor Sunpower initially conceived the fabric as flat and uncurved membranes, as a result, and proposed a white mesh as a means of allowing water drainage on the flat panels.

A flat piece of woven fabric, while very strong in resisting tension loads that pull on it directly, is unable to carry a load across a span unless it is curved along its length, in the manner of a suspension bridge cable. However, through the use of rigid mast or beam elements to manipulate its shape, it is possible to pretension a fabric surface into a curved shape so that in can successfully resist both upward and downward wind, live, and snow loads. Fabric membranes are typically curved into “anticlastic” shapes like that of a saddle, which rises in the middle from side to side and sags in the middle from front to back. Upward loads are resisted by tension in the fibers that “hog” or rise along their length, while downward loads are resisted by the sagging fibers spanning in the opposite direction. The load resistance of these anticlastic forms is dependent on curvature about opposing axes of the membrane. As the curvature in the fabric membrane is increased, the resulting tension stress in the fabric and the loads on the supporting structure under load decrease proportionally.

Not surprisingly, initial analysis of the flat membranes proposed for Springs Preserve by engineer Huntington Design Associates found high stresses in the fabric and cables, excessive loads on the supporting structure, and large deflections, demonstrating the inefficiency of flat membranes in resisting loads. To achieve curvature in the membranes, the rectangular fabric panels were redesigned with six attachment points to the supporting steel. The four corner points connect at the same workpoint elevation on the top surface of the primary steel girders. Intermediate attachment points along two opposing sides, though, are secured at lower elevation. The offset in attachment point elevations forced the membranes into anticlastic curvature, and the reanalysis that followed showed the payoff in reduced fabric and cable stresses and supporting steel loads.

The South Elevation of one of the arrays (Fig. 4) provides a different perspective of the curved membrane shape. It also shows other important features of the photovoltaic design strategy: the range of rotation of the trackers, the positioning of the membrane beneath the array, and the gaps that are provided between the rows of panels on each torque tube to allow light to penetrate between the panels and be reflected from the fabric back up to the panel bottom.

Analysis of the curved membrane design indicated that the some of the fabric panels would still deflect sufficiently at midspan under moderate wind to impact the large transverse girders above them. Valley cables were therefore added on top of the fabric between the intermediate anchorages. These cables pull the fabric into a lower profile along the valley line, not only preventing the fabric from touching the steel above, but also providing a more visually dynamic curvature. The slope of the fabric remains small near mid-span, even after these modifications, so that the danger of ponding was not eliminated, and the final design therefore retained the use of mesh fabric. The mesh provides a “soft” barrier to vision and light, both relieving the visual clutter of the arrays overhead and providing gentle shading of vehicles and visitors below. Besides increasing the comfort of those using the parking areas, the shading provides a small ancillary energy benefit: drivers can turn their air conditioning down as they exit the parking on hot days.

In order for the fabric to provide economic value to the project, it was important that its installed cost not exceed the value of its contribution to energy generation. Simplicity in fabrication and erection were therefore critical elements of the design strategy. Structural bay widths are generally uniform, so that fabric contractor Eide Industries could maximize the speed and economy of membrane fabrication.

Fabric panels are bordered by galvanized steel catenary cables, and the catenaries are secured to membrane plates at the corners of each fabric panel that are in turn anchored to the supporting steel. Simplicity, repetition, adjustability, and visual elegance were the goals of the connection design. All membrane plates and stainless steel Frontier jaw fittings are identical, and the stainless steel all thread rods anchored to the supporting steel provide both tensioning mechanisms and adjustability for fit up. The intermediate panel connection points employ custom fabricated Frontier fittings, in which the catenary cable rides across the head of the valley cable spade end fitting.

The fabric panels extend past the edges of the array to provide their benefit throughout, but the gaps between fabric panels created by the catenaries reduce the effective albedo beneath a small portion of the panels. The loss in power production was deemed acceptable, in view of the improved economy, speed of erection, and visual richness provided by the curved fabric openings. The enlivening visual character of the fabric catenary edges is particularly evident at the edges of the structure, where the playfulness of the membrane contrasts with the hard lines of the steel structure. The steel was treated with muriatic acid to cause oxidization, then coated with a clear sealant. Its finish mirrors that of other steel elements throughout Springs Preserve, and complements the colors of the surrounding desert.

The Springs Preserve carport PV arrays provide a visually dramatic and environmentally effective use of solar power, and the incorporation of fabric membranes into the array structures represents a step forward in both the photovoltaic performance and architectural quality of these applications. Ongoing testing will provide more concrete data about the effect of fabric membranes on the performance of bifacial PV arrays, but development of this technology continues in the meantime, and the team of photovoltaic contractor Sunpower and engineer Huntington Design Associates have recently completed a second structure using similar design strategies at the Carmichael, California Water District Headquarters Building.

Author Craig G. Huntington, S.E., is principal of Huntington Design Associates, Oakland, Calif., and a regular contributor to Fabric Architecture.

*In the extreme case, albedo may be increased from the 0.10 of asphalt to the 0.75 of a typical solid, white fabric. At Springs Preserve, where parking areas are paved in concrete and the fabric is a white Ferrari mesh, albedo was increased from 0.30 to 0.65.

The following article is about the Springs Preserve water
by Derrick Penner, Vancouver Sun, February 2007

City firm helps Las Vegas turn off the tap
The Bellagio Hotel's three-hectare fountain on the Las Vegas strip, with its 1,000 jets and twice-an-hour choreographed water shows, evokes a sense of tropical luxury. About five kilometres west, bordered by major thoroughfares, the Southern Nevada Water Authority is spearheading construction of a $310-million US nature preserve to remind people they are in the middle of the Mojave Desert. "[Las Vegas] is a community that should not exist by any stretch of the imagination," Isaac Marshall, a principal of the Vancouver design firm AldrichPears Associates, which helped guide the centre's creation.

"And yet it's the fastest-growing city in North America, and has been ... for the last six years. Six thousand people a month move [to Las Vegas] and have no clue they're moving into a completely unsustainable lifestyle." That is where the Las Vegas Springs Preserve comes in. It is a 72-hectare section of desert which sits on top of the artesian springs that were Las Vegas' reason for being. Its waters provided sustenance for the Mojave Desert's Anasazi and Paiute peoples and an oasis for the first European settlers.

Poignantly, those springs stopped running decades ago, Marshall said, but the site has been recreated as way to recapture the springs' cultural history and show today's Las Vegas residents and visitors a way forward. It has been an eight-year project for AldrichPears, slated to conclude with the preserve's opening in June.

Marshall said Las Vegas Springs Preserve is the brainchild of Patricia Mulroy, general manager of South Nevada Water Authority for the past 16 years. At one point, Las Vegas' water crisis was so severe, Mulroy was told the city would run out of water by 2008. Mulroy contacted AldrichPears in 1999 for help drawing up a water conservation program that could be used to engage the public. Marshall told Mulroy that water conservation wasn't really something that AldrichPears did. The firm is known for designing museum, science and cultural centre exhibits. But in corresponding with the water authority, Marshall added that the firm realized there was something it could do to highlight the need for sustainable living in the desert.

AldrichPears drew up a master plan for the Las Vegas Springs Preserve, which includes natural gardens, a desert wetland created by channelling rainwater and runoff from adjacent neighbourhoods that has been a magnet for hundreds of wild birds. The site also incorporates a new Nevada State Museum (that won't be open until 2008), the Origen Experience visitors' centre and a Desert Living Center, which AldrichPears also designed. All buildings are energy efficient and limit their impact on the environment.

Marshall described the living centre as the preserve's "jewel," because it will be a resource centre for Las Vegas residents, showing them how to reduce their water use and live more in harmony with the desert environment. "We're trying to inspire them to take actions to affect their lives," Marshall said.

Marshall added that the centre will have a big impact if it can change the behaviour of one per cent of Las Vegas' 1.6 million permanent residents and 42 million annual visitors. And for the record, Marshall noted that the Bellagio's fountain, as ostentatious as it seems, is actually a model of sustainability. The hotel taps runoff water that is trapped beneath the desert but blocked from getting back into the city's aquifers. The fountain water is then used to flush toilets and water its lawns, and when it goes down the drain, is recycled in the city's state-of-the-art treatment system as fresh water for the city.

Desert Living Center On-Site Wastewater Treatment
By Natural Systems International
The Desert Living Center emerged from a desire for sustainability in a challenging environment and ecosystem, with a mission to promote sustainable living in the Mojave Desert. The DLC architecture consists of five main buildings and several small structures which are all integrated into the landscape and function as sustainable exhibits. Each building has different sustainable characteristics to experiment with the effectiveness of the different design principles. The buildings and gardens are designed to work seamlessly together.

Natural Systems International, well versed in passive and energy efficient design, created a beautiful, functional onsite wastewater treatment system. The system includes a primary treatment tank, constructed wetlands, a recirculating sand filter, mechanical filtration equipment, and an irrigation system. The system was designed to produce reusable water from the blackwater collected in the Springs Preserve buildings. The treated graywater is reused within the DLC and the gardens to reduce potable demand.

The Meadows Detention Basin, previously a vacant and unmanaged eye-sore in the community, became the heart of the restoration efforts at the Las Vegas Springs Preserve. The principle goal of Meadows Detention Basin was to recreate a riparian wetlands with a cauldron pool spring as a primary water source. The Project was designed to demonstrate the effectiveness of riparian wetlands for the treatment of non-point source pollutants and mitigation of stormwater runoff.

One of the challenges of the design was incorporating parks and public spaces in the flood control basin. In addition to providing treatment of stormwater, the project creates significant habitat and bounty for local flora and fauna. Inclusion of the Cauldron Pool provides a historical simile with the original Las Vegas Springs, and therefore provides an opportunity for its 600,000 annual visitors to understand the relationship of water to the development of the City of Las Vegas. All project goals were accomplished without affecting the Flood Districts requirements to operate this site as a flood control detention basin.

Four walking / hiking trails wind through the picturesque Springs Preserve as interpretive displays take visitors through both a cultural and environmental history of the Las Vegas Valley. The trails lead to the Preserve’s cienega, a desert wetland that serves as a home for hundreds of native plant, bird and animal species including peregrine falcons, snowy egrets and black-crowned night herons.

View map


  Desert Living Center Lighting Case Study (465 kb)

  Springs Preserve LEED Case Study (622 kb)

  Las Vegas Springs Preserve Natural Stormwater Plan (503 kb)

  Map Springs Preserve Las Vegas (1,095 kb)


Desert Living Center Inside Out

Springs Preserve (Las Vegas, Nevada, USA)