Abstract
Proper adjustment of domestic hot water (DHW) load structure can balance energy demand with the supply. Inefficiency in primary energy use prompted Omsk DH company to be a strong proponent of a flow controller at each substation. Here the return temperature is fixed to the lowest possible value and the supply temperature is solved. Thirty-five design scenarios are defined for each load deviation index with equally distributed outdoor temperature ranging from +8 for the start of a heating season towards extreme load at temperature of -26°C. All the calculation results are listed. If a flow controller is installed, the customers might find it suitable to switch to this type of DHW supply. Considering an option with direct hot water extraction as usual and a flow controller installed, the result indicates that the annual heat consumption will be lower once network temperatures during the fall or spring months are higher. The heat load profiles obtained here may be used as input for a simulation of a DH substation, including a heat pump and a tank for thermal energy storage. This design approach offers a quantitative way of sizing temperature levels in each DH system according to the listed methodology and the designer's preference.
Highlights
District heating (DH) systems have historically consisted of large-scale conventional production units owned by utilities
In EU DH systems run with supply line water temperatures between 50–55 °C or 60–70 °C with return line water temperatures of 25 °C to 40 °C and still meet heating requirements for space heating (SH) and domestic hot water (DHW) in residential or commercial buildings [8]
Im & Liu [11] indicate that such difference between return and supply temperatures does not succeed in reaching the design temperature of SH or operating temperature of auxiliary equipment, and more heat is required from a combined heat-and-power (CHP) plant
Summary
District heating (DH) systems have historically consisted of large-scale conventional production units owned by utilities. Thermal energy produced at a DH plant is transported via a branched network and is transferred to the consumer. This connection is commonly called a substation or an energy transfer station. Malmö, Sweden is pioneering building-level facilities, creating the concept of prosumers [1] – consumers of heat that can provide heat into the system. This has driven an energy company (1) to modernize equipment at a demand side and (2) to lower network operating temperatures, leading to the so called fourth generation district heating (4GDH)
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