By Ron Auvil
I know it's stating the obvious, but maintenance and capital budgets are tight. So tight they squeak. “We are looking for pennies in the furniture” tight. Most of my personal time is spent with clients in commercial facilities, and I hear this all the time. Nowhere is this true more than in the area of energy and maintenance retrofits. The vast majority of my clients have a large amount of maintenance that is ”deferred” - put off into the (distant?) future. This deferred maintenance, along with aging equipment and lower staffing levels, is causing these facilities to bleed energy dollars at an alarming rate. At the same time, the pressure is on by administrators to reduce energy to help keep the doors open and offset reductions in other areas. So what is someone to do? The answer may be good old-fashioned ingenuity. What this article will do is suggest some low-cost/high payback energy retrofits.
One of the biggest changes in the last few years is much shorter payback times. Up until recently three years was considered a decent payback, with anything less than two years considered outstanding. My how things have changed! In many facilities, it takes a calculated payback time of a year or less to free up the dollars to fund it.
One of the first things to consider is to establish what are acceptable temperature and humidity levels in the facility. These then become a standard to which all adhere. Keep in mind that organizations such as ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) publish standards regarding what “comfort” is. Use these standards as you establish what’s acceptable in your facility.
While it is difficult to generalize, many buildings are over ventilated. The old statement about “10 percent OA” is functionally obsolete. Over-ventilation wastes energy because the outdoor air must be conditioned.
- Ventilation control systems. You can easily use the building automation system (BAS) to measure and control ventilation air levels. You can monitor the specific amount of ventilation air using airflow monitoring stations. Ventilation air can be reduced, generating a quick payback in reduced energy costs. In addition, indoor air quality can be measured and controlled more effectively.
- Introduce only enough ventilation air to satisfy the needs of the space and the occupants.
- New burners. A quick payback approach for a heating system may be replacing an old low-efficiency burner with a newer, more efficient one. This is in lieu of replacing the entire boiler or heating device. A burner replacement may have a payback measured in months, not years.
- Heat exchangers. Many old heat exchangers operate at a low efficiency. Replacement with a new heat exchanger can result in a payback in one operating season or less.
- Insulation. Don’t ignore adding insulation where needed. Many older systems have been repaired multiple times due to leaks, and often the technicians remove the old insulation and do not replace it.
- Damper repair/replace. Outdoor air dampers may stick in the open position and not close properly. They will then admit too much cold air into the building, which increases the amount of heating energy needed. You can use a good airflow meter to check the amount of airflow.
- Check steam traps and insulation with an infrared meter. One steam trap blowing through live steam can cost thousands of dollars a year in energy waste. You can pretty much figure that at least 10 % of steam traps will fail per year, so if you have not checked them within the last few years you are sitting on a “gold mine” of savings! Rebuilding a failed steam trap is simple and rebuild kits are cheap.
- Steam leaks. Any steam leaks identified should be repaired as quickly as possible, regardless of size or location. Usually, they leak 24/7, wasting precious energy dollars.
- Burner tune up. Without even replacing a burner, your existing one can be checked with a combustion analyzer with increased efficiency as a result.
As you might imagine, there is a large variety of cooling systems, with large facilities using central chiller systems and smaller buildings using smaller packaged equipment.
- Tower economizer. One of the most energy saving retrofits, with a payback of less than a year in many cases, is the cooling tower economizer. What it does is allow the cooling tower condensing water to be used to cool the building, while leaving the chiller off. A client in the South told me recently that he was able to shut the chiller off in mid-October and leave it off until April. Normally during this time period the chiller would be cycling on and off to provide chilled water for their computer data center. His estimated payback was around six months.
- Tower fans. Variable speed drives on the cooling tower fans can provide better control of condensing temperatures, allowing energy savings on the fans and the chiller systems.
- New chiller controls. Often, the addition of modern microprocessor controls can extend the operational life and save energy at the chiller. Older control systems, such as pneumatic, are often out of calibration and do not allow the implementation of advanced control strategies. The energy savings permitted by a chiller control retrofit are often measured in a year or less.
- Water treatment. Contaminated cooling tower water will deposit sludge and slime on the tube surfaces, inhibiting heat transfer. Since these systems use such a large amount of energy, a small short-term investment can generate a payback measured in one cooling season or less.
- Damper repair/replace. Often outdoor air dampers are not working properly. In many cases they are stuck and will not move as they should. Often they are stuck in an open condition. They will then admit too much air into the building. This air must be cooled, heated, humidified, or dehumidified. All of this can cause enormous energy waste. These dampers can be easily repaired or possibly replaced. The payback, again, is often less than a year.
- Set point change. Way too many facilities allow the occupants to change their set points a large amount. Not long ago, I was in a facility that allowed occupants a ±10°F (-24°C) set point adjustment. Frankly, this is crazy. One or two degrees F will save large amounts of energy over a cooling season. The set points should also be consistent in the entire building (i.e. a standard), instead of everybody adjusting it to what they want. There is a lot to be said for the 68°F (-6.7°C) heating / 78°F (-3.3°C) cooling set point standards of the late 1970s and early 1980s.
- Sensor calibration. Many temperature sensors in rooms and mechanical systems may be off by a few degrees. These inaccuracies can cause large increases in the amount of energy used. Many of these sensors can be calibrated with an accurate test instrument and corrected in the BAS system programming. A 10 or 15 minute calibration can save big money with a payback in a matter of weeks. Some buildings have hundreds of sensors that need this calibration. Accurate handheld devices, such as those manufactured by Fluke Corporation, are highly recommended. The potential savings far outweigh the initial cost of the instrument, which can then be used repeatedly in the future.
- Chiller sequencing. A sophisticated chiller sequencing strategy may allow the most efficient chiller to come on first and run the longest. Implementation of this strategy will drive dollars to your bottom line quickly. Also, using a sophisticated strategy will allow a longer time between chiller starts, saving energy dollars.
- Basic maintenance. In the midst of what seems to be some complex solutions, don’t ignore basic preventive maintenance. Package units need basic filter changes and coil cleaning to ensure maximum heat transfer.
- Constant volume to variable air volume (VAV). The conversion of a constant volume system to variable air volume can be a quick payback retrofit. This would involve the addition of a variable speed drive (VSD) on the supply and/or return exhaust fans. This has the possibility to dramatically reduce the electrical energy consumed by the fans, as well as allowing “soft start.”
- Inlet vanes to variable speed drive (VSD). Many older conversions to variable volume systems involved the use of inlet guide vanes to regulate air flow through the centrifugal fan housing. This was usually accomplished using pneumatic controls and actuators. While they worked satisfactorily, the use of a VSD will still allow significant energy savings and a quick payback.
- Motor retrofits. Older motors are often at a at a lower efficiency design. New motors can often offer a quick payback due to their higher energy efficiency.
- Controls retrofits. If any of the air handlers still have older pneumatic controls on them, a retrofit may allow a quick payback due to energy savings strategies being available.
- Control system strategies. Most air handling systems today are controlled by building automation systems. The control strategies that are implemented often do not take advantage of the capabilities of their control system programming. Examples would include reducing the static pressure in the ductwork based on either highest or average VAV terminal box demand or reducing static pressure during high electrical demand peak periods.
While all of the above retrofits and strategies involve a quick payback, it very often pays to address the utility issue directly.
- Consider installing meters on water lines for cooling towers. Since the water evaporates from the tower, the water is not dumped into the sewer system. Thus the sewer charge may be reduced from the water utility bill. This alone can dramatically reduce the water bill and generate a quick payback. A client of mine at a large airport installed the metering and saved over $300,000 in the first year alone!
- Install utility metering on leased space in your facility and charge the tenants for the amount of utility they actually use. They will end up paying their fair share and generate a quick payback for you.
- When replacing or updating controls, install those with occupancy sensing. This will allow spaces such as conference rooms and many others to remain at a different set point since nobody is using the room.
- Contact the utility. Many facility managers do not have a relationship with their utility providers. This is a mistake. Ask the utility providers what grants and programs are available to generate a quick payback for energy saving investments. They may install advanced metering and monitoring equipment at a reduced price. Consider participating in utility programs that allow them to reduce your equipment runtime. While you may experience some short term discomfort you will get a break on your utility cost, often in the first month!
- Ask others. Don’t be afraid to use professional organizations and peers; ask them what generates quick paybacks for them. As you look through these retrofits and strategies pick and choose the ones that work for you, and then use them to quickly generate some savings!