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3. Doktoritööd

Selle kollektsiooni püsiv URIhttp://hdl.handle.net/10492/7081

Sirvi

Sirvi 3. Doktoritööd Autor "Allik, Alo (advisor)" järgi

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  • Pisipilt
    Kirje
    Control of air-to-water heat pumps used for heating nearly zeroenergy buildings with algorithms considering renewable energy availability
    (Estonian University of Life Sciences, 2025) Pihlap, Heino; Allik, Alo (advisor); Lehtonen, Matti Ilmari (advisor); Annuk, Andres (advisor); Institute of Forestry and Engineering; Gevorkov, Levon (opponent)
    ABSTRACT. Air-water heat pumps are widely used for heating and cooling buildings because they are economical to install in both new and renovated dwellings. Typically, the operation schedule of installed heat pumps depends solely on changes in outdoor temperature. When examining their operation throughout the day, it is evident that they work the most during the colder hours. Since the efficiency of a heat pump depends on the outdoor temperature (the lower the temperature, the lower the efficiency), air-water heat pumps used for heating buildings also operate the most during the hours when their efficiency is the lowest. Therefore, it is possible to reduce the amount of electricity used for heating a building by installing a thermal storage system and scheduling the operation of the air-water heat pump. The aim of this doctoral thesis was to develop a methodology that allows minimizing the amount of electricity taken from the grid by air-water heat pumps used for heating nearly zero-energy buildings. To achieve this goal, a novel parameter (RCOP) was introduced, which combines the temperature-dependent efficiency of the heat pump with the reduced demand for grid electricity due to the use of renewable energy. The doctoral thesis demonstrated that the developed methodology, which uses the RCOP parameter to optimize the operation of the air-to-water heat pump, is universal. This methodology is suitable for all buildings that use air-water heat pumps for heating and have thermal energy storage capability. By monitoring a building's energy usage over a longer period, the effectiveness of the method can be increased using machine learning techniques. By connecting the control systems of air-water heat pumps in buildings to the cloud, it is possible to reduce the volatility in the power grid caused by renewable energy production more broadly.
  • Pisipilt
    Kirje
    Novel application principles for energy storage technologies in nearly zero energy buildings
    (Eesti Maaülikool, 2021) Lill, Heiki; Allik, Alo (advisor); Annuk, Andres (advisor); Colak, Ilhami (opponent); Hamburg, Arvi (opponent)
    In this thesis the renewable energy storage options in residential buildings are under investigation. This is to store cheap electricity due to the temporary overproduction of large wind farms and also on-site solar and wind farms. In an electric system, there should be a balance at all times between energy production and consumption: as much as is produced should also be consumed. Deviating significantly from this balance can damage electrical equipment or cause serious network failures and even blackouts. Unfortunately, both solar and wind energy generation possibilities are associated with (rapid) changes in production. The simplest examples are wind gusts for wind turbines and intermittent cloud cover for solar panels where the electric output power changes in seconds. In order to smooth out the rapid changes in electricity production, the work proposes the possibility to add ultracapacitors to the battery bank for temporary energy storage, which would act as a buffer and are able to temporarily store the produced electricity. So far, the sale of green energy to the electricity grid has been supported at the state level. However, this paper examines the next step in how to support the storage capacity of the produced energy in order to increase self-consumption. To this, a state subsidy measure for battery banks is proposed. Due to short-term overproduction of electricity, there are more and more situations where electricity is sold at zero or even negative prices on the power exchange. The reason is simple - it is more practical for producers to temporarily pay to consumers for electricity consumption than to stop production for a while. This work also proposes a method for storing energy in heat carriers under favorable conditions for the consumer in order to ensure a balance between the production and consumption of the electricity network.