Did You Know District Energy Offers More Favorable Carbon Footprint?
In cases where buildings are considering electric resistance heat, utilizing District Energy for heating results in a more favorable “Carbon Footprint.” Within the TVA service area, electric energy delivered to the customer comes from a variety of sources including coal, nuclear and hydroelectric. The inclusion of nuclear and hydro aid in reducing the total level of CO2 related to TVA production of electrical energy in this region. But, when compared to the delivery of heat energy to the customer from a gas-fired District Energy plant, District Energy can deliver the same amount of energy at 45% of the CO2 level resulting from electric resistance heating. If developers are seeking to achieve material environmental benefits, District Energy is a good choice.
For more information about the services offered by the Nashville District Energy System to assist developers in this consideration, contact the NDES Project Administrator, Harry Ragsdale at 615-264-6411 or via email at hragsdale@thermalegi.com.
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Incorporating District Energy at the Design Stage of a Project Yields Greatest Savings.
Incorporating district heating and cooling services (DHC) from Nashville District Energy System (NDES) into a new development at the design/conception stage can achieve reduced capital costs and reduced operating costs over the life of the development.
Perhaps the most significant economic benefit is in the form of avoided capital costs. Capital cost avoidance can have a material affect on the customer’s project viability. This is particularly true if the proposed facility is large enough to warrant chilled water generators. When DHC is designed into the project, the total building area, as well as the costs, can be reduced as a result of removing the chillers, cooling towers and a portion of the pumps and related piping and electrical. There are also structural savings, as well as aesthetic benefits, by not having to locate cooling towers atop or adjacent to buildings.
Utilizing district heating in lieu of boilers or electric resistance heat can achieve similar opportunities for cost reductions.
Unfortunately, once a design concept begins to mature, and DHC is a post-design alternative, the full-avoided costs are lost. If the initial design concept does not incorporate DHC, the larger utility infrastructure costs remain, structural systems relating to cooling towers and other central plant equipment remain unchanged and little credit, if any, is given for the elimination of space dedicated to in-building chillers since the balance of the facility is often developed around the mechanical room envelope.
Additionally, it is particularly challenging to encourage a designer or contractor participating in the development of design or costing to move from in-building/self-generation to utilizing DHC because such changes reduce overall project construction costs and can impact respective fees. If in-building design has already been completed, then a significant amount of time already committed to the project becomes a sunk cost and is not necessarily recoverable. Conversely, if the project starts under a DHC concept that is later determined to not meet the developers objectives, the costs to add the infrastructure, space and necessary equipment for self generation into the planning is not significantly different than if such work was incorporated initially.
In short, project owners and developers can benefit greatly by considering DHC at the earliest point in the project concept and design.
For more information about the services offered by the Nashville District Energy System to assist developers in this consideration, contact the NDES Project Administrator, Harry Ragsdale at 615-264-6411 or via email at hragsdale@thermalegi.com.
Article taken from February 6, 2008 paper by Harry Ragsdale, Thermal Engineering Group, Inc.
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Metro DES Customer Meeting Recap
At a recent customer meeting, Metro DES management made a financial presentation that reviewed and compared unit costs from FY07 to FY08 and capital projects for FY07 and FY08.
Read More or View Customer Meeting Presentation
Capital Projects Provide Condensate Savings
Three completed capital projects and two projects currently in the design stage will complete refurbishment of the condensate line for the District Energy System.
The condensate return line is a major component of the District Energy System. It carries hot water that results from steam condensing during the heat transfer process back to the District Energy Plant. The condensate lines were in pretty bad shape prior to the refurbishment projects that started several years ago.
As a closed system, the hot water being returned to the plant is important because it is reheated in the steam generation process and uses less energy than cold water that otherwise has to be added to the system. Condensate comes back to the plant at about 170 degrees F as opposed to 60 degree city water that would have to be used instead. Prior to the work on the system, less than 1% of the condensate was making it back to the plant. Now, 60% to 70% is returned. The result is significant energy and water savings in the overall operation of the system.
Pesky Leak Discovered and Repaired
A sonic listening device operated by Metro Water detected a chilled water leak that has eluded CEPS for more than a year. Located near 3rd Avenue North and Deaderick, the leak was discovered and repaired as a result of the cooperative effort between Metro Water and CEPS. CEPS employees had attempted to locate the leak for more than a year but the volume of water was not sufficient enough to create visible evidence. A corroded valve fitting on an abandoned bleed line used to bleed air off the system during installation was the cause of the leak. Since abandonment, the line was buried below ground.
DES officials knew of the leak because additional water had to be added to the closed system. While the volume of water required was not a significant cost issue, the ongoing addition of water also required treating the new water with chemicals to reduce corrosion and prevent solids buildup.
"This ends a long and frustrating search," said Mike Bradley. "It is good to have this item off our agenda."
DES Paying Dividends, Subsidies Continue to Shrink
The Metro Finance Department recently reported that the Metro DES facility provides the city with significant value. An audit released by the department found that the facility's value comes from declining subsidy and solid waste costs, combined with a more efficient energy source.
The Metro Nashville District Energy System (DES) provides energy for heating and air conditioning of nearly 40 buildings in downtown Nashville. The city has used district energy services for three decades, pioneering the waste-to-energy method of district energy in the early 1970s via the Nashville Thermal Transfer Corporation (Thermal).
The DES facility replaced the aged Thermal facility in January 2004 to provide its customers with more reliable, efficient, cost-effective and environmentally friendly heating and cooling.
Fast Facts:
- Steam and chilled water are pumped to the buildings through 26,000 feet – or five miles – of underground pipes.
- The facility operates nine chillers and four boilers, and has the capacity to provide 23,400 tons of chilled water for cooling and 260,000 pounds of steam for heating.
- The largest pipe in the DES system measures 42 inches in diameter; the smallest is only a half inch.
DES circulates roughly 2 million gallons of chilled water at any given time. - Each minute, up to 42,000 gallons of chilled water are pumped through the system.
- Steam travels through the pipes to downtown buildings at an average rate of 70 miles per hour.
- Nearly 100% of the water used for chilled water cooling is recycled, while only 30 percent of the water used for steam is new water, and 70 percent is recycled.
- DES employs 24 people
- Visit the links to the left to learn more about the Metro Nashville DES.