Energetic and exergetic analysis of a low- Temperature based district heating substation for low energy buildings

• District Heating (DH) technology contributes to the low GHG emissions energy system, facilitates a renewable energy usage, and increases the overall system efficiency, while providing the necessary heating services to the built environment. However, the existing DH technology may not be technically and economically effective to service buildings with low-energy demands. Here, low- Temperature based district heating (LTDH) provides a better match between supply and demand in terms of energy quality. This paper deals with the energy and exergy analyses of a LTDH substation supplying a secondary LTDH network as a subnet of the existing DH system. The substation is supplied with a mix of supply and return flows from the main DH network. An energy and exergy analysis was employed based on modelling and simulation to compare the performance of two proposed substation configurations to that of a conventional DH substation operating at low- Temperature. The study was performed for a year round outdoor temperatures scenario under steady-state conditions. The exergy destruction at the system components was identified and compared. The results of this analysis show that by using the low- Temperature flow from the DH return pipe, the final exergy efficiency of the overall system is increased. On the other hand, assuming an adiabatic system the energy performance stays the same. As compared with the conventional DH network, the integration of the proposed LTDH substation reduced the share of energy demand covered by the main DH supply by 20-25% and improved the overall exergy efficiency from 79% to 85-87% depending on the substation configuration. Based on the results, the solution presented is seen as an effective approach to reduce the system's losses, and to increase the quality match between the low-energy heating demands and the supply.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Maskinteknik -- Energiteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering -- Energy Engineering (hsv//eng)

Nyckelord

District heating

Efficiency

Exergy

Low temperature

Substation

Temperature cascading

Economic and social effects

Economics

Environmental impact

Greenhouse gases

Heating

Temperature

Energetic and exergetic analysis

Energy and exergy analysis

Low energy buildings

Low temperatures

Modelling and simulations

Steady-state condition

Substation configurations

Energy efficiency

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