“Later” can become never. If some energy-saving opportunities are saved for another day, it is likely that simple inertia will prevent that day from ever coming at all. Moreover, those lost days are savings that are lost forever. Everyone involved, from the business owners, the installing contractors, to the rebating authorities, should have an interest in making an efficiency upgrade project as comprehensive as possible. It makes the most of everyone’s time, effort and money, and begins the energy savings sooner.
There are many different strategies to save energy in refrigeration. How do you decide what to invest in? Some are different approaches to reducing the same energy use, and are competitive technologies that would not normally be combined. For example, reach-in door heaters can be controlled so that they run less of the time. Alternatively, zero-energy doors requiring no heaters to control at all can be used instead. It’s a case of one or the other.
However, most efficiency measures are not mutually exclusive and can be used in various combinations. It is often good to integrate different technologies to work together harmoniously to save energy, each in its own way. Usually multiple efficiency measures should be undertaken simultaneously when possible.
There are two basic ways to save energy:
- More efficient equipment (Do the same work with less energy.)
- Smarter control (Use energy less often.)
Improved refrigeration efficiency can result from more efficient equipment, like ECM evaporator fan motors. It can come from operating those motors only when necessary, like with an electronic controller. Another way is with a walk-in cooler economizer. These three efficiency measures, using various combinations of better equipment and better control, can, and often should, be used in unison to minimize the amount of electricity used.
Often, however, the order in which efficiency measures are considered determines which ones are actually undertaken. This is because, although there is more than one way to save any given kilowatt-hour of electricity, each unnecessary kWh can only be saved once.
For example, consider the case of an old-fashioned incandescent light bulb burning continuously inside a convenience store’s walk-in cooler. A highly efficient LED light bulb may use 90% less energy to light the space than the incandescent bulb. A motion-detecting switch connected to that bulb may reduce its runtime by 90% compared to a bulb that never gets switched off. Either measure by itself will save 90% of the electricity needed by people to see inside the cooler. If you first install the LED bulb, you might consider it to have saved 10 times as much energy as the motion-detecting switch, perhaps choosing to not even install the switch. Alternatively, you might have first just installed the switch, and considered it ten times better than the bulb. You might be better off to see them both equally responsible for the total savings and install them both at the same time. By combining them, the energy used in the cooler can be reduced by 99%. Actually, the total amount of energy saved on the electric bill would be even greater, 140%, because the compressor would not have to cool down what the bulb warms up. As long as both efficiency measures are undertaken, they can be considered equally responsible for the huge reduction of energy. So, as long as each solution lasts long enough, and is not too expensive, which is probably the case, for maximum benefit, they would both be worth doing.
A utility seeking to encourage investment in energy efficiency will calculate an incentive based on its cost and expected life, as well as on the expected improvement when compared to historical performance. In some cases, these authorities evaluate each individual piece as a separate “measure” and look at the savings and return of each measure. In these cases, the order of analysis makes a huge difference and would skew the results.
We think the better way to look at the project is to consider all of the measures as components of a holistic solution. The analysis should be done on the basis of the cost and efficacy of the entire system taken together against the “baseline” energy usage. Does the system make sense?
This holistic analysis also makes more sense in the context of something like a controller. Each controller can be used to do a variety of different things: fan control, door heater controls, door light controls, novelty cooler control, and managing an outside air system. It is the same core hardware with one or more additional services hooked up as needed. The reality is that there is not a distinction between a fan controller or a door heater controller. They are one and the same.
Finally, the last consideration is that in the case of these orphan energy savings, “later” does mean “never”. A feature that would be a small incremental cost as part of a large project becomes cost prohibitive done on its own. Using the example above, an incremental 9% savings may make sense as part of a larger job, but would not make sense if it required a separate audit, application, sale, and site visit. That delay has turned a cost effective project into a cost prohibitive one that will not be done.
As an example, if considered first, ECM evaporator fan motors, evaporator fan control, or a walk-in cooler economizer can each save more energy than the other two efficiency measures. However, by combining all three as a comprehensive pool, you can get a cost effective solution for the largest possible pool of kWh savings. Those savings will be captured over the long term and validate the generous financial incentives offered by the utilities. However, left undone, there will be little incentive for the customer or vendor to come back.