The word “green” is now unavoidable during an average day in North America. You’re likely to first read this word on the front page of the morning newspaper. Later, you’ll see it repeatedly used in trade journals, as well as consumer magazines. That afternoon you will notice it on several products or advertisements at the local store. By the end of the day chances are you’ll hear it used as the focus of a new government job incentive program.

American culture now interprets “being green” as a Zen-like sense of consciousness about how we should relate to and protect our environment. We have been relentlessly conditioned to view green as something we should aspire to, a never-ending quest to minimize any adverse impact we may inflict on our planet. Many people now view themselves as needing more of whatever green happens to mean to them.

Going green can be anything from installing a bike rack at a public building, to using glass mulch made from crushed bottles for landscaping, to adding insulation to one’s attic. The word “green” has become an envelope for older terms such as recycle, conserve, and reduce. Going green also describes actions such as increased use of renewable energy, planting grass and flowers on your roof, or bringing your own bags to the grocery store.

Within the context of mechanical systems I see “green” categorized as follows:

  • Low Energy Use:  
    •  High thermal efficiency
                 
    • High distribution efficiency
                 
    • Low or no standby heat loss
                 
    • Interior comfort that reduces occupant-induced wasted energy
                 
    • Appropriate use of renewable energy

  • Long Equipment Life:
    • Minimal maintenance and simple serving
                 
    • Reduces travel to/from installation site
                 
    • Reduced installation energy (electrical use, temporary heat, soldering fuel)
                 
    • Reduces use of expendables
                              -Less soldering flux 
                              -Less VOC emissions
                              -Less stripped wire insulation
                              -Less unusable lengths of tubing
                              -Less packaging materials to dispose of
                              -Less clean up materials
                              -Less need for replacement components (filters, nozzles)

  • Environmental Stewardship:
    • Low emissions
                 
    • Use of recyclable materials


  • Figure 1.

    Practice What You Preach

    Last year I attended a session on solar water heating at an international conference on solar energy use. The conference had record attendance, and the room where the session took place was packed with more than 100 people, who made time in their schedules and paid good money to be there. 

    One speaker began the session by asking how many in the audience had a solar water heating system installed on their home. By a show of hands I estimated no more than 10% of the people in that room lived with solar water heating. 

    Granted, some of those present were new to the subject and wanted to get more involved. Some may also have lived in rented quarters where such a commitment was not theirs to make. On the other hand, modern solar domestic water heating systems have been available in North America for more than three decades. Government-based financial incentives for such systems have also been in place for several years. Fuel prices, especially that of oil, didn’t just become unstable last year. The speaker’s subtle implication was that many of those present have had ample opportunity to demonstrate what they advocate, and in many cases, what they hope to profit from. In short - practice what you preach!

    Over the years I’ve had the opportunity to do this by installing a wide range of what are now considered “green” energy systems in our home. They include solar energy systems (active thermal, passive thermal, and photovoltaic), a ground source heat pump, a heat recovery ventilator, and a wood-burning stove. 

    I can assure you that living with these systems has exposed their benefits, as well as their shortcomings in ways I would never have discovered by reading through literature, surfing Web sites or making occasional site visits. The knowledge gained from this experience has been invaluable in influencing how I currently design systems, and what I write about.

    If you sell energy-efficient equipment, you should make a diligent effort to use some or all of this hardware in your own home and/or place of business. You’ll be in a better position to advise your customers. The fact that you personally use what you sell is also a huge confidence booster for most consumers. Want proof? How often, after describing multiple options to a potential customer, have they responded, “If this was your house, what would you use?”

    Achieving Deeper Green

    As a professional, you also have the responsibility to teach your customers how to operate the systems you provide to maximize their benefits. Challenge them to use these systems in ways that optimize their benefits. Keep in mind that this sometimes involves compromises in what most North Americans are accustomed to. For an example of this, see Figure 1, which shows a solar thermal combisystem. It uses a combination of solar energy and conventional (gas) energy to supply a home with heating and hot water.

    An external, stainless steel brazed plate heat exchanger is used to transfer heat from the antifreeze-filled collector circuit to system water in the storage tank. 

    A second stainless steel brazed plate heat exchanger is used to separate domestic water from system water. It’s mounted adjacent to the storage tank and has its own circulator (P3), which moves water from the tank through the hot side of the heat exchanger. The circulator (P3) is turned on by a flow switch, which closes whenever there’s a domestic hot water demand of 0.5 gpm or more. When operating, (P3) only draws about 10 watts of electrical power. Cold domestic water is instantly heated as it flows through the brazed plate heat exchanger.

    A Concept Looking for a Market

    The standard way to operate a system like that shown in Figure 1 would be to maintain the top of the storage tank at or above a temperature that assures domestic hot water is always available. With a properly sized heat exchanger, that temperature would likely be in the range of 125ºF to 130ºF. If the sun has been out, the tank may be at or above this temperature during the afternoon and evening. If not, the boiler operates as necessary to maintain the required temperature.

    Most North Americans would assume that domestic hot water should be available 24/7 - whenever they choose to open the tap. Herein lies a great opportunity to alter conventional thinking in a way that could have a profound impact on how Americans use energy.

    This system could have another operating mode - let’s call it domestic hot water setback. This mode would be in effect when normal domestic hot water service is not deemed necessary, let’s say from 11 p.m. to 5 a.m. During this time, the temperature at the top of the tank is maintained based on an outdoor reset curve appropriate for the low temperature space heating system. This temperature will usually be lower than that required for normal domestic hot water delivery, especially during spring and fall. 

    During this reduced temperature mode the system retains some ability to heat domestic water, but not necessarily to normal delivery temperature. If the occupant has to take a shower at say 3 a.m., and there was insufficient solar gain during the previous day, a temporary override button - one that could be placed on the bathroom wall - could fire the heat source in a time-limited priority mode to quickly boost upper tank temperature and restore normal hot water delivery temperature. Sufficient hot water for a comfortable shower would be available within 5-10 minutes. That’s the only compromise.

    The reduced temperature mode allows greater use of the solar energy delivered to the tank during the previous day. It also improves the efficiency of the modulating/condensing boiler when operated in that mode. The top of the tank would be increased back to normal DHW delivery mode before the typical morning demand for domestic hot water. Following this high demand period the system could revert to reduced temperature mode to improve collector efficiency during the midday period. Adaptive controls could even monitor domestic hot water usage trends and adjust tank temperatures to optimize solar utilization and provide high satisfaction with domestic hot water delivery.

    Challenge Your Customer

    Perhaps you’re worried that customers would complain about having to push a button and wait 5 to 10 minutes if they want to shower in the wee hours of the morning. Herein lies the opportunity to challenge them about their “greenness.” 

    Rather than complaining about a very minimal compromise, customers who really want to be green should embrace such a scheme once they understand the benefits. This is a way for people who profess a green lifestyle to demonstrate their commitment and influence others about appropriate energy use. Eventually, the American cultural mindset about having convenience at any cost (i.e., hot water standing ready for the unlikely event of a 3 a.m. shower) could be changed to champion responsible energy use with minimal compromise. I think there are quite a few green-minded customers who want to go there, but simply don’t understand how to get there. This is a teachable moment that benefits both the seller and the customer.

    As I see it, hydronic heating has always been a “greener” choice compared to other heating methods (i.e., forced air or electric resistance heating). Emerging technology, and modified use patterns such as described above, could push hydronics technology into a whole new shade of deep green. 

    Learn it, live it, teach it!

    Links