The main goals for the network design at both the Trafalgar and Davis campuses can therefore be summarized as follows: 1. Low operating supply temperature for minimal heat/energy loss, which reduces operating costs; 2. Maximum delta T at energy transfer stations for maximum energy transfer and maximum value for pumping costs, which reduces operating costs; and 3. Maximized pipe flow capacity to allow for smaller pipes, which reduces capital investment. Hydraulic optimization Besides being a very important part of feasibility studies for investigating the potential for district heating or district cooling networks in different areas, hydraulic calculations and thermal analysis are prerequisites for their correct dimensioning and efficient operation. This applies as much to the expansion or renewal of existing networks as it does to new district energy schemes. The design team performed hydraulic calculations and thermal analysis in optimizing the district energy networks on both Sheridan campuses.
The Davis Campus in Brampton in principal already has a relatively efficient hot water-based district heating system, but it is heavily interconnected between primary and secondary systems and operates at a fairly low delta T. Most Davis buildings are connected to this system. Upgrades on the Davis Campus will include connection of a presently islanded building and a new student residence to the new network as well as construction of a new energy centre to be located in a new engineering building. The energy centre facility is similar in concept to that of the Trafalgar energy centre. The upgraded 1.5-km (trench) hot water network will serve 93,000 sq. m of building space; and the 0.35-km (trench) chilled-water network will supply 25,000 sq. m. Extension of a new, hot water network at each campus will allow the heating plants to be optimized and operate at higher levels of efficiency. The heat supply portfolio can be adapted over time, eliminating the least efficient sources as more efficient or less-polluting alternatives are added. The new Trafalgar Campus energy centre is being designed to maximize the operation and heat contribution of a new primary CHP plant. This will be achieved by minimizing return temperatures via a variable-flow network and through the utilization of thermal storage.
The hydraulic calculations ensure that pipe dimensions are optimized both technically and economically.
With an optimized hydraulic system, the pipeline dimensions can often bemade smaller than in a system that is not optimized, without a loss of capacity. Reducing dimensions can save money – both capital and operating costs. When integrated with a geographical information system (GIS) (fig. 3), hydraulic analysis can also be a very powerful tool for maintenance and planning for upgrades and expansion, as the GIS data from the pipeline registry can be quickly combined with an analysis of the impact on the network of capacity, heat loss and price.
The design team also aimed to maximize distribution network efficiency while minimizing costs.
At Sheridan College, as elsewhere, lower hot water system operating temperatures will result in lower heat losses. However, pumping energy and the capital cost of the network will be lower if flow rates are reduced by increasing the difference between supply and return temperatures. As these two requirements cannot both be satisfied, it is necessary to optimize the temperatures within any heat network. The network cannot be analysed in isolation from the building services within connected buildings and the heat source(s). Lower operating temperatures and lower return temperatures can be achieved through appropriate building services design, i.e., by using larger heat emitters and selecting suitable approaches to controls. This may lead to higher costs for the building services but lower costs overall. The operating temperatures selected for the network can have an impact on the efficiency of the heat source and hence its cost and CO2 content.
Figure 3 – Integration of GIS with hydraulic analysis.
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