Posts Tagged ‘energy’

Thoughts on Industry Trends

Posted on: No Comments

Thoughts on Industry Trends

Back in late January, I attended the ASHRAE Winter conference and AHR show – right in the middle of when the polar vortex was unleashing its fury on the northeast! As I look back on the messages that our industry is pushing, a few topics really popped out.

The phrase “conservation is our best energy resource” – we see ways to conserve energy every day, yet still get stuck in the “I can’t do anything about that” mode. Mention to a client that window upgrades may be a more feasible alternative than upgrading the boiler installation.

In a session on ASHRAE 90.1, one of the speakers pointed out this: Why do we stick to the usual temperature rises on water systems? A chilled water system design temperature is 12oF, always has to be 12oF. But shooting for the higher temps of 16oF or even 20oF is achievable. I can take that idea one step further. An existing chilled water system is designed for 12oF, but you can add to that system with loads that are designed for a higher rise. We’ve all heard the horror stories of low delta T on a chiller, but it’s the opposite if the load comes back at higher than design! If you can change the loads so the peak temperature rise is 14 or 16 or more, the existing chiller can handle it more efficiently. Plus you get the benefits of lower pumping cost.

Another sector of our industry which has received little attention, the rooftop unit (RTU), is hitting the energy radar screen. Keep in mind that almost 40% of space in the USA is cooled by an RTU. Efficiencies are going up, and the manufacturers have made it easy to retrofit by providing roof curb adaptors to fit the 1980s RTU you are replacing. I don’t do a lot of RTU work, but realized that the energy bar is still pretty low in ASHRAE 90.1, (EER of 11). There is talk of setting minimum SEERs of 15, and that is coming from outside of ASHRAE (DOE, I think). In many cases across strip malls in this country, the energy use in an existing space can be cut by 40% with a new RTU coming out in the next year.

It’s an exciting time to be in the business of heating and cooling, with many opportunities to make a lasting difference in energy consumption. I try to not get stuck in the usual ruts of design philosophy, and challenge everyone out there to do the same.

Sustainable Laboratories

Posted on: No Comments

Sustainable Laboratories

Darryl Beals and I recently attended the 2013 I²SL (International Institute for Sustainable Laboratories) conference (formerly Labs 21 conference) in Minneapolis, MN. It was a pleasure being back in Minneapolis where I went to college at the University of Minnesota. The weather was perfect in the high 70s and I had a chance to catch up with some old friends in the evenings after attending seminars all day.

As you can imagine with a conference focused on lab sustainability, much of the 3-1/2 days of seminars and workshops was focused on saving energy in laboratories. As much as 2/3 of the energy usage of a typical research campus is from the laboratory space that is typically less than 1/5 of the buildings on campus. There is a lot that can be done to improve energy efficiency in new and existing laboratories, but one area that is of special interest to me is to reduce airflow. Electricity is our highest cost driver these days, with natural gas prices being historically low across the country. As most engineers are aware from the fan laws any reduction of airflow amounts to a reduction in fan energy to the third power. For instance, a 25% reduction in CFM will reduce fan power usage by 58%. This is savings you can get excited about!

One big opportunity for savings in airflow is in the laboratories themselves. The first step to reducing air flow is to have a lab with Variable Air Volume (VAV) controls to allow varying the flow of air to and from the lab based on the cooling loads and fume hood sash position while maintaining safe minimum airflow during occupied and unoccupied times. With a VAV system and by sizing equipment for the actual expected loads in the space and establishing minimum Air Change Per Hour (ACPH) based on science, airflow can often be greatly reduced. Many times engineers use a minimum ACPH in the lab, such as ACPH of 6, based on a rule of thumb rather than informed understanding of the work actually being done in the lab. Ideally the facility owner would consult with an Industrial Hygienist to determine safe minimum ACPH during occupied and unoccupied times. At the conference, the University of California (UC) – Irvine presented the success they have had reviewing lab air changes with their Industrial Hygienist to reduce ACPH in 85% of 1,610 lab rooms. Often times this reduction in airflow is in conjunction with an air contaminant monitoring system that will increase airflows in the event of a chemical spill or other accident.

Some of speakers at the conference focused on how further reductions in airflow can be made by reducing the minimum exhaust from fume hoods. Assuming you have a variable flow fume hood, the minimum exhaust when the sash is closed is determined by the AIHA/ANSI Z9.5 standard. The latest version (2012) of this standard allows a minimum range from 150 ACPH to 375 ACPH. This equates to about 10 CFM/SF to 25 CFM/SF of fume hood bench top surface with a typical hood. The old ANSI Z9.5 standard required 25 CFM/SF minimum. The new standard allows significantly lower minimum exhaust air flow in less hazardous fume hoods. The facility’s Environmental Health and Safety personnel or Industrial Hygienist should be consulted to establish the correct minimum fume hood flow. Where many fume hoods are in a lab, this minimum flow can have significant affect on unoccupied and even occupied minimum supply air flow.

Reducing airflow is one area of “low hanging fruit” where lab energy efficiency can be greatly improved. If you have a facility that is currently running with a constant volume lab, you could experience significant energy savings by converting to variable volume and making the above improvements. Sometimes budget gets in the way of full implementation of variable flow in existing laboratories. In those cases, you can take a step-by-step approach as we are doing at Purdue Wetherill Laboratory of Chemistry. In this case, exhaust fans have been prepared for variable flow operation and await future phases to implement variable flow within each lab. As explained at the I²SL conference, these improvements, along with some other items, allowed UC Irvine to save 50% or more in energy costs in their labs.

WTHR 465 Lab