Abstract
This study examined an integrated solution of the building energy supply system consisting of flat plate solar thermal collectors in combination with a ground-source heat pump and an exhaust air heat pump for the heating and cooling, and production of domestic hot water. The supply energy system was proposed to a 202 m2 single-family demo dwelling (SFD), which is defined by the Norwegian Zero Emission Building standard. The main design parameters were analyzed in order to find the most essential parameters, which could significantly influenced the total energy use. This study found that 85% of the total heating demand of the SFD was covered by renewable energy. The results showed that the solar energy generated by the system could cover 85–92% and 12–70% of the domestic hot water demand in summer and winter respectively. In addition, the solar energy may cover 2.5–100% of the space heating demand. The results showed that the supply air volume, supply air and zone set point temperatures, auxiliary electrical volume, volume of the DHW tank, orientation and tilt angle and the collector area could influenced mostly the total energy use.
The aim of the study was to define an energy supply solutions for a low-energy commercial building in cold climates. A new low-energy office building built with high quality building insulation better than the Norwegian passive building standard was analyzed by using EnergyPlus. The results showed that the heat pump solutions could be used to cover the building base load, while the peak load should be covered by additional energy sources. Due to a high indoor temperature caused by the high quality building insulation standard, an increase in ventilation air flow was necessary during the summer. To fully utilize the heat pump technology possibilities and avoid unnecessary use of the electric boiler, the control strategy without night setback was preferable. The techno-economic analysis showed that the best energy supply solution seemed to be an air-to-water heat pump without solar assistance, while a 50% increase in the energy price could make the solution with the solar collector economically attractive. A similar trend might be noticed for other building types under the same economic conditions, because the relative ratio between the savings and the total energy use would be similar.
Freeze protection in ventilation systems is important to avoid freeze damages and increase in maintenance costs. Freezing in a ventilation system can appear in construction and operation phase. The aim of this study was to test a new method for freeze protection in ventilation system. This method implies use of an additional heat exchanger. The method used two hydronic circuits: the first one with water on energy supply side, and second one with mixture of glycol and water at the secondary side. The mixture transfers heat from the energy source via an additional heat exchanger to the coil in the air handling unit (AHU). AHU with freeze protection from a manufacturer was tested in the laboratory. Since it was not possible to obtain a supply air temperature of -20 oC in the laboratory conditions, a model was developed on the MATLAB\Simulink platform. Several operation scenarios were tested on the Simulink model and they included use of three types of energy sources: boiler, heat pump, and district heating with outdoor temperature compensation. Results showed that even new method with mixture of glycol and water could tolerate low air temperature, the AHU would require known sequence control for freezing protection, where the circulation pump between energy source and heat exchanger starts first. This sequence control is necessary regardless of energy source. Finally, the article gave recommendations on how to define sequence control to avoid freezing in AHU.