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Utilization of district heating return water and backup heating in new apartment buildings
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School of Engineering |
Master's thesis
Electronic archive copy is available via Aalto Thesis Database.
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en
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108
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Abstract
Climate change requires urgent action, and improving the energy efficiency of building is a key part of the solution. In Finland, district heating covers 46% of the heating energy for buildings, and improving its efficiency is essential. Utilizing return water from district heating in heating of apartment buildings requires auxiliary heating, but it allows for lower system temperatures, which can enhance the efficiency of district heating production and distribution. The return water system also impacts investment and operating costs for consumers. Developing economically viable pricing models is crucial to making the use of return water attractive to consumers, potentially leading to lower energy costs and reduced emissions.
The aim of this research was to study the auxiliary heating demand in district heating return water system in heating of an apartment building by using dynamic simulations. Additionally, the study examined the impact of the return water system on investment and operating costs, and assessed what kind of pricing model would make the use of district heating return water economically feasible for consumers. The auxiliary heating methods selected for the study were district heating supply water, electric boilers, and return water heat pump.
Based on the study, 77% of the annual heating energy demand and 91% of the peak heating power demand of the studied building can be covered using district heating return water. The choice of auxiliary heating system does not affect the amount of energy that can be utilized from the return water but can influence the amount of auxiliary heating energy purchased. In the studied building, a district heating tariff offering a 30% discount on the energy from return water and the peak power component of the basic fee, the discounted payback period for all the auxiliary systems studied is ten years or less, assuming a real interest rate of 3% and an escalation rate of 2%.