• Contractingbusiness 1602 0410rst

    Going Green and Spending Less Of It

    April 1, 2010
    Innovation helps a refrigeration systems engineer save customers money.

    Nick Shockley's favorite customers are those that crave innovation. Shockley, P.E., is a senior refrigeration engineer and director of engineering services for Henderson Engineers, Inc., based in Lenexa, KS. It's music to his ears when he hears from customers who are committed to saving energy, and are willing to pay more up front to ultimately save money in the long run.

    "Those customers realize that innovation is going to save them money down the road. They look at cost, carbon footprint, energy, and refrigerant charge. There are many factors in the equation," he says.

    The payback scenario is easy to explain. "Much of the green technologies coming out today show paybacks of less than two years typically, and no more than five," Shockley explains. "Those include variable frequency drives, which have very favorable paybacks. Secondary coolant — such as glycol or CO2 — is another method that costs more up front, however, there's savings to be realized in reduced refrigerant charge and fewer emissions. Ultimately, if there's a tax on a business's carbon footprint, the payback will be even better. But for now, we're seeing three or four year paybacks on secondary coolant systems."

    Shockley says retailers are combining air-cooled condensers with variable frequency drives to control fan speeds, which saves a great amount of energy, and tends to stabilize the compressor head pressure. "I've seen Danfoss, Baldor, and Emerson VFDs used most often. I also like the Copeland® Scroll Digital™; it stabilizes the suction pressure on the rack," he says.

    He adds that many of today's electronic valves are beneficial in system retrofits. "They've replaced old mechanical refrigeration control valves (such as evaporator pressure regulators) with electronic valves. They have a much tighter control range, and take some of the drift out of the system, such as the Sporlan CDS and Danfoss KVS stepper valves. "These improved valves can typically hold case temperatures within plus or minus a half-degree of set point. The old mechanicals valves tend to drift one or two degrees off of set point," he explains.

    Taking Ownership
    One of Henderson Engineers major retail customers has made them responsible for "refrigeration design ownership." The engineer of record designs the systems in such a way that it could be competitively bid to multiple installers. Henderson performs most of the applications engineering, as well as construction documents, creating a controls profile, and writing operation sequences. Henderson also conducts functional performance testing on new refrigration systems in the field, to ensure they're working properly.

    Reduced Piping + Reduced Charge = Reduced Costs
    Loop piping designs are another important innovation: they don't cost more, and show immediate savings. With loop piping, several supporting refrigerant lines are fed by a main supply, and they branch off to reach individual circuits or cases. Shockley compares it to a zoned HVAC system.

    "Loop piping can reduce copper piping lengths by about 50%, with a commensurate reduction in the in-store refrigerant charge. There are fewer brazed joints, and reduced insulation. It's a cheaper install all around, and results in a smaller check for the end-user to write," he says.

    This savings story gets even better. "If the end user decides to use glycol secondary coolant, the contractor could then also select ABS plastic pipe rather than copper," Shockley explains. "It’s a quicker installation, and cheaper than copper."

    Original Ideas at Work
    Henderson Engineers is experimenting with ways to bring HVAC and refrigeration "together" from a heat reclaimation standpoint. Prominent among those ideas is a combined water-cooled refrigeration and HVAC system.

    "Refrigeration systems produce a lot of waste heat that for the most part is rejected into the atmosphere. But in the winter, the HVAC system needs heat. We're working on ways to push waste heat to the HVAC system and reduce natural gas bill, by using water coils to reclaim the heat.

    "Rather than taking water from the refrigeration system and sending it to a cooling tower, we send it through the HVAC reclaim coil, which pulls the heat out of the water and uses it by way of a water source heat pump or a pre-heat coil and an air handler," he explains. "It's been great. It cuts down on your gas bill, and spares the cooling tower."