The U.S. Department of Energy last week released a notice of proposed rulemaking on energy efficiency for commercial boilers.
Energy managers and building owners shopping for units today should be aware that standards continually change. Though standards set by the DoE are for new boilers – buildings won’t be forced to replace units due to new standards – it is important to track where the industry is going. Joanna Mauer, the Technical Advocacy Manager of the Appliance Standards Awareness Project, says that the most common commercial boilers sold today have an average lifespan of 25 years and a minimum energy efficiency level of 80 percent. The standard being proposed by the DoE hikes that efficiency level by 5 percent.
The current process is part of a legal requirement for the DoE to consider changes to standards once every six years, Mauer said. The DoE had been informally considering an efficiency level of 95 percent. The 85 percent level suggested in the proposal apparently was lower than many anticipated. “There clearly is a lot of room for improved efficiency,” Mauer said. “Based on some preliminary DoE data 85 percent is most common and is offered in a number of models. There are products available with a wide range of efficiency levels, including many with significantly higher efficiency levels than the proposed standards.”
Mauer said that the DoE didn’t share its thinking on why it opted for a lower efficiency in the NPRM. Mauer posted a blog at the ASAP website highlighting the savings that the new standards could generate:
DOE estimates that customers on average would save between $500 (for small gas-fired hot water boilers) and $36,000 (for large oil-fired steam boilers) over the life of the equipment with the proposed standards. On a national level, commercial boilers meeting the new standards sold over 30 years would save about 0.4 quadrillion Btus (quads) of energy–enough to heat all the natural-gas-heated homes in New England for two years–and net savings of $0.4-1.7 billion for customers. However, higher cost-effective standards for small gas-fired hot water boilers, which make up about 30% of sales, would more than double national energy savings to 1 quad while saving customers $0.3-2.6 billion.
Mauer said that the key element of a boiler’s efficiency is its heat exchanger. The heat exchanger, as the name implies, is where the energy that is fed into the boiler from an outside source is transferred into usable heat. Some of this heat invariably is wasted. The lower that wasted heat, the higher the boiler’s efficiency.
There is a break point at about the 90 percent efficiency level, Mauer said. It is quite possible that the conservative stance taken by the DoE on energy efficiency rules is that is to stay shy of that break point. Until about the 90 percent level, Mauer said, a non-condensing boiler is used. After that, the switch is made to condensing units.
The gases that are the emitted by the boiler contain water vapor. In a non-condensing unit, these gases are expelled through the flue and escape into the air. In a condensing unit, this gas is cooled, which leads to condensation of the water and the recovery of what in essence is a second round of energy. This, she said, generally requires a second heat exchanger. “That’s a more significant change,” she said.
The next step is a public hearing on April 21. Written comments are due 60 days after the NPRM is posted in the Federal Registry. That, Mauer said, could happen in about two weeks. The DoE will consider written comments and input from the public meeting in crafting the final rules, which likely will be published later this year. They will take effect three years after being published.
Thus, new rules for commercial boilers are likely by the middle of 2019. That sounds like a long time. Commercial boilers, however, have extremely long lifespans. Building owners and managers are best advised to consider boiler efficiency and the new rules as they research boilers purchases.