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How to Pare Down Energy Consumption During Non-Productive Hours

SPT110126

This is not yet another article about energy in times of economic and environmental concern. Instead, it is about the effectiveness of managing energy use during the “dark times,” when the office is closed, when the plant is not producing, or when the skeleton or maintenance shift is on-site. These are when energy usage should be as near zero as is feasible. In my experience this is rarely the case, presenting yet another opportunity to capture short-term cost benefits and deeper long-term productivity and environmental gains.

I have recently had two occasions to contemplate this often overlooked aspect of energy management. The first was at home. I am relatively sensitive to the energy use of my home and home office and was looking at ways to drop the electricity base load. I went through the house and switched off everything — lights, computers, appliances. What will be no surprise to most of you, the building continued to pull substantial amounts of electricity and cash. Being in Ohio where electricity is mostly coal based, this also causes substantial amounts of greenhouse gases. This is somewhat embarrassing for a so-called “energy expert.”

The second occasion was during a conversation I had with a senior-level Toyota energy manager. Toyota has a very rigorous energy management process which includes regular formal energy audits, known as “treasure hunts,” each taking up to three days. Part of the approach is to include an audit with at least one shift with no production. This allows them to evaluate how well and how fast energy consumption is as close to zero as possible at a time when no cars are being made.

As with all energy productivity, there are obvious measures that can be taken quickly that cause minimal disturbance and incur little cost. The first step is to gather as much data as possible. Historical time interval data should be available from utilities or internal records, which can be matched against working patterns. It is important to understand not only the steady-state dark-time usage, but also how fast it drops after productive work stops. It is common for one shift team to be better than others at shutting down processes efficiently. If so, this is an obvious potential for best-practice sharing between shift teams.

Existing data already will indicate the size of the opportunity and maybe even provide some indicators as to where energy continues to be used. Usually, though, new questions arise over the causes of dark energy use and then the detective work begins. If a scheduled maintenance or rebuild period is coming up, the energy manager should prepare a protocol to measure the shutdown process and ongoing energy use in detail, ideally with adequate submetering to localize the usage. Similar detail should be gathered for the normal working cycles, possibly accounting for seasonal differences.

Armed with this background, the triage begins. First and most obvious is to change practices that would shut down lighting and equipment that is unnecessary, which is often an embarrassingly high amount. The next step is to identify energy usage that is necessary but can be curtailed. A typical area for this is security and safety lights, or set-back levels of heating and cooling. I remember evaluating the energy use of one of the largest Ikea stores in Europe. Energy use was mysteriously high between 5:00 in the morning and the store opening at 10:00. The reason was found to be one or two storeroom staff conditioning the entire building to make one small office comfortable. In this instance, simply investing in an efficient space heater saved tens of thousands a year.

Then there are the grey areas where energy use could be shut down, but tradition demands that it stays active. Compressed air networks are a classic example of this. At a minimum, fix the leaks and make sure compressor cycling and equipment choice is as effective as it can be. In parallel, evaluate what really needs to be kept on standby and what can safely be shut down. As in the home, this may involve splitting up systems and, equally important, changing deeply ingrained habits.

The growing gorilla in the room is standby power for computers, displays and other devices, and chargers. Some of this can be tackled with changes in behavior and easy access to hard cut-off switches. Unfortunately, these rarely deliver expected savings and tend to quickly be overtaken by the growing inventory of devices. This is a classic area where the energy manager and the procurement manager need to be completely in synch to systematically shift habits to procure deep-standby devices. In some U.S. states and in the European Union, these are increasingly likely to be required by law in the very near future.

None of this is rocket science and many measures can be taken with minimal cost. However, they do call for behavioral changes that are not always easy to implement. A good energy manager should not let that be a deterrent and should aim to make the dark times even darker.


Peter Garforth's columns regularly appear on our sister site PlantServices.com

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