By Michael F. Carmichael
May 5, 2011
How can an electrical generating plant that burns coal and wastes about two-thirds of its energy possibly be considered “green”? When that waste energy is used to heat or cool thousands of office workers and apartment dwellers who keep warm or cool by way of a district energy system.
In a previous article, Corp! discussed briefly how a district system was providing heat and air conditioning to many of the buildings in Detroit’s Entertainment District as well as others in its downtown core. Instead of each building having its own capability to provide an appropriate temperature range for its tenants, steam, hot or chilled water is created at a centralized plant and sent to each client facility through an underground piping system.
There are hundreds of these district energy systems across the world, serving not only downtown office and other buildings but also large college campuses - some with as many as 200 buildings including classrooms, administrative areas and residential housing units.
More than three-quarters of these districts use natural gas as the primary material to power the machinery needed to heat and cool the hundreds of thousands who benefit from these centralized operations. Coal provides about 15 percent, with the remaining fuel sources coming from industrial waste, biomass or other sustainable resources. Unlike individual buildings with a permanently installed heating and cooling system, a centralized district energy system often has the ability to use alternative sources when necessary - whether to moderate market price or supply fluctuations - yet another plus for their clients.
The idea of district energy goes back to Roman days but, in Detroit for example, it dates back just to 1903. There, giant tunnels were dug some 80 feet below the surface, lined with brick, then filled with some of the total of 39 miles of pipe that carried steam generated from the original plant - still operating, by the way - out to municipal and private office structures.
Today, says Victor Koppang, CEO of Detroit Thermal the current operator of the system that serves nearly 150 properties - including Ford Field, the domed home of the Detroit Lions, some 75 percent of the energy used comes from the combustion of industrial and commercial waste in a government-certified “renewable resource” facility - more commonly known locally as “the incinerator.” In the coldest days of Detroit winters, says Koppang, “the original plant uses natural gas to augment the steam supplied by the main plant.”
Koppang points out that having individual heating and cooling plants in each customer building can be expensive. “There’s the initial cost of the boiler and the infrastructure supporting it; while at the same time there’s no need for space to house the equipment; there’s thus no need for licensed on-site boiler operators, or insurance to cover an individual system. There’s still the cost of natural gas to run it and regular maintenance to keep it running. Many of the licensed operators, by the way, come from the U.S. Navy - and you have to have at least four of them because there has to be coverage 24/7.”
“I tell individual building owners who are considering installing their own system,” Koppang continues, “-why do you want to be in a business that’s not your core business and when you get it all purchased and installed, as soon as it gets bolted down, it begins to get old?’
He says that one new customer, the Rehabilitation Institute at Detroit Medical Center, told him he was right; “we’re not in the heating and cooling business, we’re in the critical care business, so you allow us to sleep at night.”
Koppang is growing the Detroit system as, it seems, are other district energy system operators. Rob Thornton, president of the International District Energy Association (IDEA), says that since 1990 “the district energy industry in North America has added nearly 500 million square feet of customer space.” That’s the way the industry measures things - by how much building space they have to provide for. Their average annual growth rate is about 37 million square feet a year.
During that same time period, explains Thornton, more than “35 completely new ‘Greenfield’ downtown district cooling systems have been built in North American cities.” Thornton includes “North America” in his comments because some of these systems have been built in Toronto and other Canadian locales as well as Chicago, Boston and Indianapolis.
Asked if the economics are still favorable for retrofitting an area with district energy, Thornton says, “These systems can typically provide a rate of return similar to or slightly better than utility-regulated returns in the range of 8 to 15 percent, depending on a wide range of factors.”
One of those factors is fuel source. Detroit’s Koppang, speaking fondly of his sustainable fuel supply, says, “garbage is renewable. Americans create a lot of garbage. European culture produces much less than we do. Here there will always be garbage.” The same holds true for Baltimore, according to Thornton. Additionally, says Thornton, “Another fine example of sustainable district energy is in St. Paul where they use waste wood from the Twin Cities to create district heating, district cooling and co-generate 30 megawatts of electricity to the local grid. Having a district energy network in an urban setting is a key advantage to leverage the economies of scale to invest in cleaner, more sustainable energy supplies.”
St. Paul is also taking things a step further, says Thornton. “District Energy St. Paul in January, 2011 commissioned a 1 Megawatt solar thermal array on the roof of the Convention Center downtown. It provides primary hot water supply to the building and excess heat is distributed to the district heating network to heat nearby buildings. In Europe, solar is a growing component of the heating networks in community scale systems, especially Germany.”
Just applying current technology to existing traditionally fueled generating plants can make the environment cleaner while it’s reducing overall fuel consumption, Thornton says. “Across Denmark, nearly 80 percent of the district heating supply is from waste-to-energy facilities and surplus heat from power generating stations. District heating is the essential infrastructure that enables communities to conserve enormous amounts of fuel and reduce greenhouse gas emissions.”
Those communities do not always have to be huge office parks or downtown cores. They can also be planned residential and mixed-use developments. Thornton says, “We are finding that developers, owners and tenants want to live in ‘Green Communities’ and district energy thermal infrastructure is an essential infrastructure component to optimize heating and cooling. The Dockside Green development in Victoria, British Columbia, is a LEED Platinum brownfield development that integrated biomass district energy for a multi-use residential development. It was one of the most successful real estate developments in Canada in the past five years and had a district energy network at its core.”
Saving energy, saving money, relying more on sustainable resources, all seem to be in the DNA of the IDEA of district energy.