Application of ground energy in ventilation
Plaksa, Alexei (2014)
Mikkelin ammattikorkeakoulu
2014
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Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:amk-201405198478
https://urn.fi/URN:NBN:fi:amk-201405198478
Tiivistelmä
One of the main goals of this research work was to evaluate the effectiveness of a system based on the direct utilization of ground energy. The effectiveness is estimated and compared to more traditional systems. The effectiveness is assessed only in the aspects of recovering and spending heat energy.
The observed systems have elements such as heating, cooling coils and heat recovery units as most of the traditional systems. The peculiarity of such systems is that one of coils for heating or cooling is connected to a ground loop, not to more popular energy sources as a district heat network or others. Thus they allow transferring energy from the ground to the air in case of winter air heating or transfer energy from the air to the ground in the case of summer air cooling. It should also be noted that in such systems there is no heat pump between the ground loop and the air coil. A heat carrier circulates directly between the ground loops and the air coil without the transformation of energy, which could take place in the case of installed heat pump.
The operation of the system is analyzed based on the available data from the automation system of an air handling unit. The air handling unit is located in an office building (N-building), in the campus of Mikkeli University of Applied Sciences. Available data is for the winter 2012-2013.
The result of the research is that for the winter period such a system based on the utilization of the ground energy is not so effective as more common systems based only on a heat recovery unit in energetical aspects. The energy gain is achieved only if it is possible to replace the system in the case with a system based only on a heat recovery unit with the temperature ratio less than 0,65. In practice temperature ratios are 0,7-0,8. Ensuring average temperature ratio for the winter period of the heat recovery unit in a system based only on this heat recovery unit, at least 0,65, provides no energy profits compared to the system in this case. Ensuring higher values of temperature ratio results in ineffectiveness of the system in the case compared to more common systems. Aspects of additional expenditures for ground works, more equipment, running costs are to be taken also into account.
The observed systems have elements such as heating, cooling coils and heat recovery units as most of the traditional systems. The peculiarity of such systems is that one of coils for heating or cooling is connected to a ground loop, not to more popular energy sources as a district heat network or others. Thus they allow transferring energy from the ground to the air in case of winter air heating or transfer energy from the air to the ground in the case of summer air cooling. It should also be noted that in such systems there is no heat pump between the ground loop and the air coil. A heat carrier circulates directly between the ground loops and the air coil without the transformation of energy, which could take place in the case of installed heat pump.
The operation of the system is analyzed based on the available data from the automation system of an air handling unit. The air handling unit is located in an office building (N-building), in the campus of Mikkeli University of Applied Sciences. Available data is for the winter 2012-2013.
The result of the research is that for the winter period such a system based on the utilization of the ground energy is not so effective as more common systems based only on a heat recovery unit in energetical aspects. The energy gain is achieved only if it is possible to replace the system in the case with a system based only on a heat recovery unit with the temperature ratio less than 0,65. In practice temperature ratios are 0,7-0,8. Ensuring average temperature ratio for the winter period of the heat recovery unit in a system based only on this heat recovery unit, at least 0,65, provides no energy profits compared to the system in this case. Ensuring higher values of temperature ratio results in ineffectiveness of the system in the case compared to more common systems. Aspects of additional expenditures for ground works, more equipment, running costs are to be taken also into account.