Advanced electric boilers offer output equal to fuel burning units with 100% energy efficiency, zero emissions, and minimal installation, operation, and maintenance costs
In many areas of the U.S. and Europe, district heating remains popular for space and water heating of residential and commercial buildings. Although the source of the heat supplied can vary, one common approach is to utilize fuel-burning boilers that produce steam. Unfortunately, conventional boilers present several challenges, including low efficiency when transforming fuel energy to heat; high installation, operating, and maintenance costs; environmental impact from harmful emissions; and some inherent safety issues.
There is growing interest in utilizing a new generation of jet type electrode boilers as an environmentally friendly solution. Due to considerable advances in the technology, these electric boilers can match the capacity (up to 65 MW) and output (270,000 pounds of steam per hour) of traditional gas or oil-fired boilers. When more output is required, multiple electric boilers can be connected to provide hundreds of megawatts of steam for district heating, and effectively replace gas fired boilers in a much smaller overall footprint.
There are a growing number of compelling reasons for municipalities to utilize high voltage, jet type electrode boilers for district heating, according to Robert Presser, Vice President of Acme Engineering, a manufacturer of industrial and commercial boilers with operations in the U.S., Canada, and Europe.
“Jet type electrode boilers can match the heating output of fuel burning boilers while converting almost all the energy to heat,” says Presser. “Electrode boilers also resolve many of the inherent drawbacks of fossil fuel burning boilers: they are much smaller, put out zero emissions, and minimize installation and maintenance costs.”
Today, the spiking cost of gas and oil is often a factor when considering an upgrade of an existing district heating system. In some cases, the concern is minimizing environmental impact. Natural gas-fired boilers and furnaces emit dangerous nitrogen oxides (NOx), carbon monoxide (CO), nitrous oxide (N2O), volatile organic compounds (VOCs), sulfur dioxide (SO2), particulate matter (PM), and the notorious greenhouse gasses carbon dioxide (CO2) and methane (CH4).
Regardless of the motivation, upgrading entails retrofitting or replacing boilers (the heat source) with cleaner, more efficient electric alternatives, along with the heat distribution network (pipes/heat exchanger stations).
Designed for Optimal Performance
Jet type electrode boilers have existed in various forms for many decades. However, recent design improvements have closed the output gap while surpassing conventional units in terms of efficiency, simplicity, responsiveness, and safety.
Modern jet type electrode boilers utilize the conductive and resistive properties of water to carry electric current and generate steam. An A.C. current flows from an electrode of one phase, through neutral, to an electrode of another phase using the water as a conductor. Since the water has electrical resistance, the current flow generates heat directly in the water itself.
“The more current [amps] that flows, the more heat [BTUs] is generated and the more steam produced. Nearly 100% of the electrical energy is converted into heat with no exhaust stack or heat transfer losses,” says Presser.
As an example, in the CEJS High Voltage Jet Type Steam Boiler from Acme Engineering, the electrodes are vertically mounted around the inside of the pressure vessel, which enables the unit to produce maximum amounts of steam in a minimum amount of floor space. The units operate at existing distribution voltages, 4.16 to 25 KV with exceptional efficiency – up to 99.9% efficient at converting energy into heat. Models can produce steam in capacities up to 270,000 pounds per hour, with pressure ratings from 75 psig to 500 PSIG. All CEJS boilers are designed to ASME Section VIII Division1 and are certified, registered pressure vessels.
The advanced steam boilers also have a 100% turndown ratio, the ratio between a boiler’s maximum and minimum output. Most gas boilers have a 10:1 or 5:1 ratio.
“The turndown means you can leave the boiler in standby at low pressure and, when needed, bring it to full capacity in about 90 seconds, which no other boiler type can achieve today,” says Presser.
“With the electric boilers, the energy input and adjustment are very precise and virtually immediate. In contrast, increasing or decreasing the temperature in a gas fired boiler is a slower process because it takes time for the heat in the boiler to rise or dissipate before reaching the targeted output,” he adds.
Jet type electrode boilers also lower costs for installation, operation, and maintenance. Gas-fired boilers require fuel lines, storage and handling equipment, economizers, and emission control equipment. Advanced jet type electrode boilers have a minimal number of components and electrical controls, with fewer parts. Under normal operation, the absence of excessive temperatures and electrode burnout also assures long operating life.
The units further lower operating costs with automatic controls that reduce the need for operating personnel.
Presser points out that the most advanced types of these boilers, such as Acme’s CEJS, also offer greater safety than traditional fuel burning models.
“With the jet type electrode boilers, there are no combustion hazards because there are no flames, fumes, fuel lines or storage tanks. There are no problems with heat buildup or electrode burnout even if scaling should occur, and thermal shock is eliminated. Also, there is no low water danger since the current cannot flow without water,” says Presser.
Communities utilizing district heating appreciate the eco-friendly nature of these boilers as well. Without combustion, jet type electrode boilers are clean and emission free. The design also eliminates many environmental issues associated with fuel burning boilers such as fuel fumes, fly ash, and large obtrusive exhaust stacks.
Finally, the electric units are exceptionally quiet compared to fuel fired boilers. Unlike gas-powered burners that throttle like turbine engines almost continually, electric boilers keep operational noise levels down. Because the loudest boiler component is a circulating pump motor, it is easy to have a conversation next to one without having to raise your voice.
With all the advantages of high output jet type electrode boilers, a growing number of communities are selecting them for district heating.
Presser concludes, “We have spoken to utilities with massive boiler plants that are traditionally stuck feeding steam lines all over major city cores like New York City. In urban centers, they really want to get away from the associated emissions. A large utility has been talking to us about putting a 60 MW steam boiler in the center of Manhattan to replace gas-fired boilers, providing a centralized theme to several buildings.”