The Sustainable Warehouse
The same options hold true for warehouses—just on a much larger scale. Don’t think of sustainability in terms of costs; think of it as an investment resulting in dollar savings—a better bottom line and a better image that win the respect of your customers and your community.
In today’s competitive environment, warehouse designers and operators are not necessarily designing new structures to be altruistic. “We are seeing three key trends in designing warehouse facilities. All provide greater sustainability, but these changes have been driven by the desire to achieve higher returns on investment [ROIs] and/or increased energy efficiency,” says Greg Hammond, Hixson Architecture & Engineering senior project architect.
According to Hammond, first, there is a trend to install materials that feature higher R values to provide greater insulation. Second, more companies are choosing cool or reflective roofing systems to reduce energy load. Finally, high-efficiency lighting systems with occupancy sensors have picked up in demand.
“We find the best energy-saving designs are the ones that include LED lighting with motion detection, reflective white roofing materials and variable speed drives [VFDs] on compressor and condenser fans,” adds Steve Tippmann, Tippmann Group/Interstate Warehousing executive vice president. Other important design elements include increasing the surface area of refrigeration heat transfer surfaces, which reduces the temperature difference on both the air cooling coils and the evaporative condenser.
Tippmann suggests that designers and engineers need to work closely with the local utilities to understand their rate contracts, which are typically driven by their supply costs. “A better understanding of their contracts means we can design the refrigeration system and [lift truck] battery charging system to utilize power at the most opportune times.”
Tippmann’s engineers also install condensate collection systems to reuse condensed water from air-cooling coils as a source for evaporative condensers. This reduces both water consumption and water being dumped into the public water treatment system.
While it might seem practical to install solar photovoltaic cells on the roof of a warehouse structure to supply additional energy to the facility, the trend has been to use white roofing and design for lightweight roof loading to accommodate pre-engineered buildings, according to Brent Kapelski, SSOE senior architect industrial facilities. These structures typically use batt insulation sandwiched between the structure and wall and roof panels. Due to updated energy codes, these walls must change to different insulation systems with higher, continuous R values.
“Upgrading the building envelope (walls and roof) is a major area of focus to increase sustainability in a food facility,” says Brian King, partner, A M King Construction. Company. “The easiest upgrade is to utilize thicker insulation in the wall panels and the roofing systems.” King also recommends increasing building height (where and if it’s feasible) before adding additional floor area. A good reason to design a taller structure is to accommodate an AS/RS if it’s in the plans.<br><br>
However, there are several tradeoffs with warehouse design, so it’s a good idea for processors/operators to know exactly what products will be stored in the warehouse, for how long and refrigeration/freezer requirements. For example, storage of packaged finished goods contained in glass bottles will require one approach while storage of raw, incoming goods in a refrigerated building will need another, according to Roger DeGood, SSOE project manager industrial facilities.
While there is a trend toward pre-manufactured metal buildings for some food and raw material applications because they’re less expensive when covering large areas, they are notoriously difficult to seal from the elements and vermin, warns DeGood. They are also single-purpose structures. If the owner is considering warehouse space that can also accommodate manufacturing, then other approaches should be used.
Correct facilities siting is essential to the sanitary vs. sustainable compromise. Docks shouldn’t be located facing prevailing winds. The remaining walls should be faced with regard to solar gain, the heating effect of the sun.
When some people think “green,” they envision a building with a literally green roof, i.e., with plants and soil on it. DeGood suggests that if the owner actually wants a “green” roof, it will require a significant structural investment to support it and maintenance costs that could easily outpace any savings from thermo mass. In addition, maintaining even a level-3 sanitary zone below an area with life forms on it would be exceedingly difficult.
Updating older structures
Existing structures may not have been designed for sustainability, but there are opportunities to make them more sustainable, beginning with repairs that have to be done anyway. “If the existing roof is worn and needs replacement, then it makes sense to install a new white, reflective roof with a higher level of insulation—even though it will be a premium over a new roof that may not be as energy efficient,” says King. The payback on an improvement under these conditions will take a relatively short time, he adds. However, the changes that result in the shortest payback period are related to equipment that uses the most electricity, e.g., lights, refrigeration, battery chargers, etc.
In addition to the roof, there are other areas to check. “Building envelope retrofit measures include new weather stripping for doors and windows, window caulking, new insulation for roof-wall intersections and the sealing of penetrations through the building shell,” says Bryan Genevick, SmartWatt project development engineer/mechanical division. These measures can help prevent outside air from getting in and conditioned air (air that costs money to heat or cool) from escaping, resulting in decreased costs associated with heating and cooling a facility.
“When designing a building envelope retrofit project, we generally try to do it as part of a comprehensive energy-efficiency solution,” adds Genevick. This includes a whole-building energy assessment of all lighting, mechanical and electrical systems to determine what energy-efficiency upgrades can be implemented. Grouping these together can reduce the payback period of the more expensive projects as the lower-cost, high-savings project can be used to help pay for these more expensive ones.
“Many retrofits can have less than a three-year ROI depending on the scope of the project, utility cost and current consumption,” says Tippmann. LED lighting, new freezer doors, refrigeration computer control systems and the repair/rework of vapor seals tend to have the best payback for those looking to make an existing facility more “green.”
“A green building will minimize environmental impact during its construction and useful life,” says Doyle Cotton, SSOE project manager industrial facilities. The three parts of the Federal 2005 EPAct Energy Efficient Commercial Building standard addressed the building envelope (insulation value of walls, roof, doors and windows), lighting system and building mechanical systems (water heaters, HVAC, etc.). The target was a 50 percent energy savings over an earlier recommended building standard. This forms a reasonable goal for what a retrofitted building project should attempt to achieve from a capital-versus-operating cost analysis. However, ROI should include all factors such as tax incentives to retrofit or rehab existing buildings reusing company assets. Capital and operating costs are a small part of a complete business case analysis.
The loading dock
One way to save energy would be to cut the dock off from the rest of the warehouse, but this is typically not a feasible option. However, docks can be designed for energy efficiency regardless of their relation to the warehouse. In a refrigerated dock, the installation of dock seals, insulated dock doors and dock equipment seals can provide a tremendous benefit in reducing energy usage, suggests King. The use of insulated wall panels separating the dock area from the cooler areas can also provide great benefit. In addition, dock areas can be designed with less height than the warehouse, lessening cooling loads.
For one client, Hixson designed a refrigerated warehouse with a partial height wall suspended from the roof separating the warehouse storage from the shipping dock areas. The partial wall was positioned directly behind unit coolers serving the dock. It was designed to collect the air that infiltrates through the dock doors and allow the unit coolers to collect and cool the air before it migrated into the storage area of the warehouse.
“On loading docks, we typically install an air door, which is effective at preventing air infiltration from occurring,” says Genevick. Dock seals and shelters are also very energy efficient and effective at keeping inclement weather out of the facilities, if used properly by warehouse workers.
For tighter sealing, Hammond recommends designing and installing vertical-style dock levelers in a continuous dock pit. This arrangement allows doors to close and seal against the dock pit, and minimizes infiltration by eliminating the continuous air gap that is present with standard leveler applications. A pit seal can also be used to close off the pit entirely when the leveler is in use loading trucks.
“We recommend sealing the fourth side with an under-leveler seal,” says Kapelski. “For example, the PitMaster from Frommelt helps to keep insects, dust and debris out and heating and cooling energy in by closing off the pit and sealing up air gaps.”
Infiltration is a large load on refrigerated buildings, and mitigating the time a door is open greatly reduces thermal load, according to Jordan Kuhn, Primus Builders director of marketing. Kuhn recommends fast seal and air doors to keep interior spaces at their intended temperature and humidity. <br><br>
“Air doors make sense from a sustainability perspective only if they make sense for the facility operator,” says King. “The selection of a door should hinge more on the intended usage of the door, the number of times it is opened, the level of access, etc. Once these factors are determined, then sustainability can be introduced into the equation.”
In the right application (e.g., cold storage), an air door can provide up to 80 percent efficiency at stopping air filtration between rooms of different temperatures. The doors are also extremely energy efficient, states Genevick. In cold temperatures, air doors significantly reduce moisture from entering the cold room and prevent ice and condensation from developing on floors, walls and products. Reduced frosting of the refrigeration cooling coils equals fewer defrost cycles, resulting in increased energy savings. Air doors are also safe and great for applications where there is a lot of high-speed lift truck traffic, according to Genevick.
High-speed curtain doors are considerably more efficient in terms of energy than air doors, but are not suitable for all applications, adds Genevick. For instance, the curtain doors tend to freeze when placed between normal temperature rooms and super-cold rooms, so in these applications, air doors are the better choice. On the other hand, high-speed curtain doors are recommended where there is a lot of traffic and where rooms are above freezing.
Overhead doors should be designed for the amount of use the door will receive, according to Kapelski. High-speed roll-up doors are preferred in high-traffic areas because they greatly minimize the time the interior is exposed to the exterior. However, the cost for a high-speed roll-up door can be as much as three times that of an overhead coiling door and five times the cost of a sectional overhead door, so a combination of doors is typically used. Until recently, in food facilities, cleaning issues have often prevented the use of high-speed rolling doors. Products like Rite Hite’s FasTrax Clean door has full USDA and FDA compliance for design, parts and materials, according to Kapelski.
For cold storage warehouses, the refrigeration and air-handling systems vie with older lighting systems for using the most electricity in a facility. Andy Scott, The Dennis Group mechanical engineer, recommends the following:
• Have the system(s) audited by a third-party group to identify deficiencies and improvements.
• Check to see if equipment can be upgraded with VFDs.
• Assure the system loads have not changed significantly from the original installation.
• Determine whether a two-stage refrigeration system might be appropriate.
• Optimize evaporator defrost cycles, particularly for electrically heated evaporators.
Older refrigeration and air-handling systems are very energy inefficient, according to Genevick. Consequently, replacing these older systems with newer, more efficient systems can result in huge energy savings. Even if the system is fairly new, opportunities for energy savings can be found by replacing inefficient or damaged mechanical components within the units, such as controls, piping, circulators, compressors and fan and filtration systems. On air-handling systems specifically, a common component that can be replaced is the evaporator fan motor. The most efficient motor that can be used in this application is an electronically commutated motor (ECM).
Another source for energy savings on equipment is the addition of energy management control systems, says Genevick. These control systems log data about energy usage throughout the facility, revealing what equipment is operating efficiently and what equipment isn’t. Once operators see how their equipment is using energy, they can begin to schedule its operation, avoiding costly peak loads. Yet another recommendation is to change out large compressors that run all the time with smaller, more distributed units that can be staged by the control system, providing the right amount of refrigeration to match the need, decreasing energy usage.
“Refrigeration equipment operates effectively if the refrigerant charge is correctly maintained and operating conditions are optimal,” says Jim Yerke, SSOE mechanical engineer industrial process. “The operational ‘sweet spot’ is generally near fully loaded conditions.” Water-cooled equipment is typically more efficient than air-cooled chillers and can be more efficient than unitary direct expansion (DX) units in larger applications. Factors that reduce equipment efficiency include:
• Extensive use of hot gas bypass
• Dirty or damaged evaporator and condenser coils
• Age of equipment
• Frost on a DX evaporator coil
• Chilled water temperature and ΔT of chilled water or air
• High condenser water temperature for water-cooled systems and high ambient air temperature for air cooling.
About 15 percent of inefficient refrigeration systems are those with a single large chiller or a DX unit that has been sized for the maximum load, according to Yerke. Oversized equipment operates at lower efficiency when partially loaded and accounts for roughly 85 percent of the cases Yerke encounters. He recommends the following strategies to improve system efficiencies:
• Use variable speed compressors
• Use multiple compressors and refrigerant circuits to match incremental changes in loads
• Check defrost cycle controls
• Control condenser water temperatures
• Control chilled water (CHW) flow rates to maintain higher ΔT across the evaporator and CHW temperature reset to raise or lower the CHW temperature as the load demand changes
• Use variable speed control on fans, low-pressure-loss ducting and diffusers
• Clean coils and filters
• Use destratification fans to keep large rooms uniformly temperature controlled with minimal fan horsepower.<br><br>
Shedding some light
Older fluorescent and sodium/mercury vapor high-intensity discharge (HID) lamps are problematic, especially in a refrigerated or frozen warehouse where the trend is to install proximity sensors to shut them down when nobody is present in the space. Fluorescent lamps are sluggish in the cold and have low light output until they warm up; HID lamps take a few minutes to start and come up to temperature and reach maximum light output. Therefore, HID lamps are not a good choice for frequent start/stop operations where they can be damaged by restarts while they’re still hot.
Upgrading a lighting system from older technologies, such as a T-12 or HID lighting system, to newer technologies like a T-5 or T-8 fluorescent lighting system can result in considerable energy savings, says Genevick.
Plus, many utilities offer financial incentives to business owners for upgrading to newer, energy-efficient lighting systems. For example, rebates may be available to help offset the cost of purchasing and installing a new T-8 or T-5 fluorescent lighting system. These upgrades usually generate a fairly short payback period of one to three years and can result in energy savings as high as 45 percent. Using T-5 fluorescent fixtures with sensors is the most economical lighting option today, says King. However, in the next few years, LED fixtures are expected to become the new standard as their upfront costs continue to drop. “LED lights can be cost effective if all costs associated with lighting and changing the bulbs are considered,” says Jerry Carter, SSOE senior account executive industrial facilities. LEDs have a long life, so placing them in locations where access is very limited either by schedule or ease-of-access may make sense.
US Cold Storage (Tracy, CA) looked at several energy-savings alternatives before replacing its old lighting with LEDs, for which it received a PG&E incentive valued at $69,222. “As part of our company-wide sustainability program, we conducted an IRR (internal rate of return) of various supply-side energy saving options—wind, solar, etc.—and none of them made financial sense,” says Dan Dietrich, US Cold Storage project engineer. “The paybacks were just too long. In comparison, SmartWatt’s value-engineered LED lighting retrofit had an IRR of 35.2 percent, and it’ll pay for itself in 1.6 years.” Replacement of HID fixtures with Albeo Technologies LED lighting shed 76 kW from the operator’s facility.
Lights out warehouse
The “lights out” factory was an automation engineer’s dream some years ago, but its primary purpose was not to save energy; it was proof that automation could work without human intervention. In this case, newer warehouses that house an AS/RS can work in almost total darkness without people, saving energy and money.
“In Westfalia’s high-density AS/RS, fewer aisles and less lighting are needed, as virtually no one works within the aisles—except for maintenance or service,” says Laura Worker, Westfalia Technologies marketing manager. “In fact, many cold facilities, such as Hershey Creameries, operate in almost darkness. The reduced need for lighting is one of the operational cost savings of AS/RS, which has anecdotally been reported to be a 40 percent drop in electrical costs.”
“One of the primary advantages of an AS/RS is the ability to store material in a very small footprint by using multiple levels,” says Doug Ferguson, Hixson A&E manager, manufacturing engineering. “Typically AS/RS systems have 12 or more levels of products in a structure that is often over 100 ft. tall.” Most existing spaces are more in the 30- to 40-ft. range, which limits the amount of storage capacity available, explains Ferguson.
This is not to say an AS/RS won’t work in a building that’s under 40 ft. tall. “We recently completed an AS/RS within an existing facility 21 ft. high,” says Worker. Located in Germantown, WI, Gehl Foods’ 300,000-sq.-ft. warehouse handles sterile, non-refrigerated dairy products in a compact, six- and eight-pallet deep storage solution that is three levels high.
Overcoming problems in retrofitting an AS/RS into a warehouse can be accomplished with a little extra planning and work. “AS/RS requires a level surface to run on. If the existing floor is not level enough, floor rails can be added from the building to make the picker stable,” says Cotton.
An AS/RS obviously saves energy expended for lighting, but several other advantages make it an option over a non-automated warehouse. For example, an AS/RS can typically cram twice the products in its space compared to a conventional warehouse. Traceability and the accuracy of order fulfillment mean orders are picked correctly the first time. The automation system can provide faster throughput than humans, and speaking of humans, the equipment can work around the clock with very little or no human intervention.
Lift trucks still employed
Most of the typical lift trucks available today can be effectively employed in refrigerated warehouses. However, they must be equipped for protection against the environment, says Ferguson. Cold and condensation can cause rust, so adequate protection must be available to keep them out of the shop. Controls should be sealed from the environment and may require the addition of heaters to assure good performance.
Electric battery and fuel cells are suggested for use in food manufacturing facilities. However, fuel cells require a different infrastructure (availability of hydrogen and oxygen gas) and are more likely to provide an attractive payback for new facilities as opposed to conversions, according to Ferguson. Fuel cells are also more cost effective for large operations with more than 50 trucks or with large throughput requirements where the cost of electricity is high.
“Batteries do suffer performance loss in refrigerated operations,” says Frank Devlin, Raymond manager of advanced technologies. “Careful battery monitoring, charging and maintenance are critical to maximizing battery shift life and performance.” For example, Raymond’s iBattery module, available with the company’s iWarehouse fleet optimization system, can be very helpful in ensuring batteries are properly maintained.
“Lift trucks built for freezer applications require a freezer conditioning package,” says Maria Schwieterman, marketing product manager, Crown Equipment. “This includes hydraulic oil/anti-freeze mixture and several heaters that help keep the electrical components dry.” She says a forklift that primarily works in a freezer application should stay in a refrigerated ambient temperature.
“While a freezer environment is not ideal for hydrogen fuel cells, they do not suffer performance loss as batteries do,” adds Devlin. “Turning hydrogen into electricity creates liquid water that must be exhausted while the fuel cell operates, or captured and drained off during refueling.” There is typically some residual water in a fuel cell stack, so turning off a fuel cell in a freezer and allowing the system to freeze could damage it, says Devlin.
“Unlike batteries, fuel cells do not incur any decrease in performance levels when used in cold storage environments,” says Schwieterman. A fuel cell operating in a cold environment creates internal process heat that allows it to warm up sufficiently to operate near its most effective operating point. This, in turn, effectively increases runtime compared to a battery-operated system doing the same work, suggests Schwieterman.
If 50 is the magic number for a fleet of fuel-cell powered lift trucks, then Wegmans Retail Service Center in Pottsville, PA is the perfect match. The first of its kind in Pennsylvania, the fleet is serviced by a hydrogen infrastructure supplied by Air Products fueling station technology. The Crown lift trucks are powered by GenDrive hydrogen fuel cell power units.
“Our folks tested the equipment early last year and could immediately see what it would mean to equipment performance and productivity,” says Dave Allar, Wegmans’ RSC maintenance manager. “Whether a gas tank is full or down to a quarter-tank, a car will travel at 60 mph. Not so when battery power is used; performance diminishes as the battery discharges.”
Beyond productivity improvements, Wegmans points to the environmental benefits of the changeover: A hydrogen fuel cell emits some heat and water, and that’s it. “We are always looking for ways to improve our sustainability,” says David DeMascole, general manager—Pottsville Distribution Facility for Wegmans. “There is also pride associated with being the first in Pennsylvania. We are proud of what we can achieve for our environment, community and employees.”
Sustainable design should never be an afterthought. It must be committed and supported from the highest level, beginning to end. “We should never hear, ‘Oh, by the way, let’s make this one LEED,’” says DeGood. Sustainability is a paradigm shift that must be reflected through the entire supply chain to be ultimately successful.
For more information:
Greg Hammond, Hixson A&E, 513-241-1230, firstname.lastname@example.org
Steve Tippmann, Tipmann Group/Interstate Warehousing, 260-490-3000,
Brian King, A M King Construction Company, LLC, 704-365-3160, bking@amkingconstruction
Roger DeGood, SSOE, 419-255-3830,
Bryan Genevick, SmartWatt, 518-406-5079,
Doyle Cotton, SSOE, 419-255-3830,
Brent Kapelski, SSOE, 419-255-3830,
Jordan Kuhn, Primus Builders, Inc., 770-928-7120, email@example.com
Jim Yerke, SSOE, 419-255-3830,firstname.lastname@example.org
Jerry Carter, SSOE, 419-255-3830,
Laura Worker, Westfalia Technologies Inc.,
Doug Ferguson, Hixson A&E,513-241-1230,
Frank Devlin, Raymond Corp., 607-656-2311,
Maria Schwieterman, Crown Equipment,