District energy systems produce steam, hot water or chilled water at a central plant. The steam or water is then piped to individual buildings or residences for space heating, domestic hot water heating and air conditioning. This means individual buildings connected to the network do not need to have their own heating or air conditioning units. District energy is efficient, reliable and cost-effective.
Cogeneration or combined heat and power (CHP) is often used and involves recycling the thermal energy surplus from electricity generation. In addition to such recycling of energy, more efficiency can be obtained via the aggregation of the heating or cooling loads of multiple buildings in close proximity. A central plant providing even loads is typically more efficient than individual building systems. Additionally, district energy systems may employ technologies such as deep lake water cooling or biomass combustion, making it an attractive option for situations where flexibility in fuel sources is viable.
According to the U.S. Department of Energy, district energy systems have been operating in the U.S. for over 100 years and currently serve more than 4.3 billion sq. ft. of building space, including landmark buildings like the U.S. Capitol and Supreme Court, the Empire State Building, the Mayo Clinic and Harvard Medical School. District energy networks are very common in dense downtown areas and at colleges and universities.
Internationally, district energy offers a number of benefits for its customers and for the environment. Not surprisingly, geospatial technology plays a key role in the engineering and operation of district energy networks. The remainder of this article examines the role of geospatial technology at two European owner-operators.
Kelag Wärme GmbH is part of a utility group called Kelag , which has 40 years of experience as a leader in district energy technology. The company operates in Austria, Romania, Bulgaria, Slovenia and the Czech Republic. In Austria, Kelag Wärme operates 77 district heating networks and more than a thousand heating plants, varying in size from micro-generation to very large installations. The district energy network exceeds 700km in length. Kelag Wärme is also a leader in finding ways to generate heat in a more sustainable way, leading to a major shift toward the burning of a renewable fuel – biomass – in the form of woodchip pellets. Kelag Wärme is the largest producer of biomass-based heat in Austria.
The data in Kelag Wärme’s GIS, which is based on Bentley sisNET, are used in engineering and planning, operations and maintenance, sales and marketing, and by senior management for strategic decision support. Most of the planning for new networks or extensions to existing networks is conducted in Bentley sisNET. Operations and maintenance uses the data for planning upgrades and equipment replacement strategies. Replacing aging equipment is very important for safety reasons to minimize the risk of the very hot water used in the district energy systems causing harm through pipe ruptures or valve failures. Sales and marketing uses the ortho-photos in the GIS to locate potential new customers by finding new buildings that are close enough to an existing network to be connected.
The GIS is also used by the planning group to schedule the depressurization of parts of the network for repairs or improvements. The GIS can be used to identify the impacted customers so they can be notified of any downtime. Shafts and fittings need to be inspected frequently to ensure that they are functioning properly and to avoid valve failures.
Kelag Wärme’s Norbert Fischer explains how the GIS has brought value to Kelag Wärme. “We have seen a substantial reduction in the amount of time it takes to locate data for new projects and for field work. What used to take hours or days happens almost instantaneously now. This is making us all more productive. The data is in one location so there’s no need for a combination of legacy GIS work prints, Excel spreadsheets and Word documents. Our thermal hydraulic modeling processes are improved and, in sum, the quality of the GIS is helping us all, in our different departments, make better informed decisions – and that’s exactly what we were looking for when we started this project.”
Essent Local Energy Solutions (ELES) is a provider of sustainable district energy solutions using waste heat from power plant cooling water in the Netherlands. Part of RWE AG, one of Europe’s leading utility companies, ELES has 300 employees, more than 80,000 customers and is a major provider in both Breda and Tilburg in the Netherlands. ELES also operates several smaller networks in the country that are connected to biogas and biomass plants. The company is developing its use of waste heat from other sources, such as waste incineration plants.
ELES also manages its district heating network with Bentley sisNET. The rapid implementation, achieved over a period of six months, was driven by Dutch government legislation requiring energy utilities to split or unbundle their network, production and trade operations.
The system complies with the Netherland’s “call-before-you-dig” legislation. Contractors must call the Cable and Pipes Information Center to determine which network owners have below-ground assets in a given location. The center then sends out a request to the network owners to provide the position of the various assets. This time-consuming and expensive manual process was replaced by an automatic system that results in substantial cost savings. The information is extracted automatically using Internet robots and the center collates the replies for all utilities and sends the reply to the requester.
The GIS data are held in an Oracle Spatial data store, making them easily available to enterprise systems. Bentley sisIMS is used to make the network infrastructure data available in a Web viewing environment providing fully accessible network data and redlining capabilities to enable field workers and others to easily locate work locations, disruptions and other items.
The ELES GIS system also enables data to be readily available to the Bentley sisHYD network modeling and analysis application for hydraulic and thermal calculations, which are necessary to optimize the piping in the district heating networks.
Bentley sisHYD is designed for hydraulic calculations of pressure pipe systems with compressible or incompressible media for district heating networks (two and three conductor networks, steam networks) and district cooling networks. Bentley sisHYD performs complex analyses on distribution networks to identify the asset usage costs, present operational status, location of critical points, failure simulation scenarios and the calculation of all major hydraulic and thermal parameters of the network. Analysis results can be presented in several ways including reports, profiles and color maps. For district heating, Bentley sisHYD calculates both the hydraulic and the thermal situation. Analysis and reports can include media flows, pressures, temperatures and heat losses. Bentley sisHYD can also model scenarios in both a static and semi-dynamic situation. Semi-dynamic situations model the changes in the input temperature (such as when a power plant changes its service temperature level) as the heated water travels through the network. Bentley sisHYD executes the thermal calculations dynamically while modeling the hydraulic component as a series of static calculations. The results are particularly useful for utilities investigating how temperature changes can result in heat energy improvements in the network.