An airtight triple outer glazing with a U-value of 0.5-0.6 W/m2K thermally isolates the cavity from the outside atmosphere.
The triple glazing is coated and has the g value of typically 0.3, which means that about 30% of the solar radiation which hits the vertical glazing enters the cavity.
The inner glass pane between the cavity and the room is a simple safety glazing with U-value of 5-6, which provides the desired thermal connection between the cavity and the room.
While the design of the inner pane is dustproof, it allows for slow air diffusion. HyWin, contrary to CCF, is not a closed cavity system and is therefore not susceptible to condensation. No dried air supply is needed.
It consists of a water-flowed pipes with vertical fins and one or more radial fans. The total surface of the heat exchanger is roughly two times the surface of the triple glazing. For a Window of 2 x 2.5m the heat exchanger surface will be around 10m2.
The low noise radial fans provide for an air speed in the heat exchanger up to 5-6m/s, which results in a heat transfer coefficient up to 35 W/m2.K, sufficient to cool or heat the air in the cavity to the desired temperature even for extreme temperatures and sun radiations.
The heat removal can reach over 2000 W for the present setup.
HyWin continuously adapts its operational mode to the solar radiation and the ambient temperature.
1. COOLING ONLY
HyWin cavity is heated by the solar radiation and the outside temperature. The heat exchanger removes the heat from the cavity and provides for sufficiently low temperature to climatize the room.
The Energy surplus is stored in the seasonal storage
2. HEATING ONLY
HyWin is cooled by the outside temperature. The heat exchanger must provide for the energy to maintain the desired temperature level.
The stored energy is used
3. HEATING OR COOLING (Mixed zone)
HyWin cavity is heated by the solar radiation and cooled by low ambient temperature. The Hywin heat exchanger will maintain the overall thermal balance and the required level of internal temperature. Little or no additional energy is needed for balancing the temperature.
Energy saving is achieved using the solar radiation to heat
4. COOLING ONLY
Similar to 1. However, the energy amount to be cooled is much lower due the absence of solar radiation.
Energy surplus is stored in the seasonal storage
In contrast to a room with a conventional facade, there is virtually no heat flow from the outside to the room. Therefore, only the internal heat sources, like persons, electrical appliances, or visible light need to be controlled to avoid temperature increase.
By regulating the internal temperature in the HyWin cavity, the heat flow between the cavity and the room can be either eliminated or restricted to the desired amount and direction.
In hot periods and strong sun radiation the cavity temperature will be set below the room temperature, thus providing a cooling effect to the room. The safety glass will be somewhat cooler, offering a comfortable climate in the vicinity of the window.
The advantage of HyWin equipped room is, that it is sufficient to compensate for the internal heat sources.
Our measurements confirm literature values, which suggest that the overall heat transfer coefficient from conduction and radiation on the inner safety glass is about 8-11 W/m2K. In the Test Unit with an active window size of 4.5 m2 we reach a heat flows up to 200-250 W. The process is relatively slow, comparable to heating/cooling ceilings.
The HyWin concept is to collect the energy from the facade during the hot period and store it in the earth probes for use in cold periods.
The annual simulation shows that for typical high-rise building and average storage capacity of the earth probes the energy collected might even exceed the winter usage.
The test unit has been designed based on previous investigations, laboratory units and simulations.
The concept for the Test Unit is to operate and measure a realistically large HyWin unit and attach it to a thermally well-defined room. We have decided to use a trailer which gives flexibility regarding the location and orientation.
The heat exchanger is provided with hot and cool water from a second, smaller trailer equipped with the necessary hydraulic equipment, cooling, and heating devices. Both trailers are connected with electrical, hydraulic and data links.
The effect of the sunshield is tested using a remotely controlled sunblind which can bea adjusted in position and angle.
The infrastructure trailer is protected by a tent, so that the side walls can be kept open for cooling. It has been operated 24/7 since beginning October 2020.
Measurement points inside and outside the test unit monitor temperature at different locations, solar radiation, humidity, light intensity, power consumption, water flow and more. The data is collected and stored on a digital datalogger. The energy balance and further important system parameters are calculated inline. A universal controller with dedicated software package is used to control all the devices and to maintain the set temperature. A remote setup allows monitoring and operation via internet from external locations.
the heated air is sucked in by the fan from the externally facing channel, cooled down and blown upwards into the channel facing the room. Thus, the air flow forms a vertical roll over the entire width of the cavity.
Project success the system behaves the same except that the cold air is drawn in, heated, and blown into the channel facing the room.
On a hot day with strong sun radiation the sunblind will prevent the radiation from entering the room. The heat is trapped in the cavity and cooled down to the desired temperature, typically few degrees Kelvin below the room level.
On a cold day, without radiation and with or without sunblind the cold air in the cavity is heated up, so that the air channel facing the room carries the warm air.
The hot summer case is thermally challenging, due to the high amount of heat to be extracted from the cavity. The limiting factor is not the heat exchanger. The heat exchanger reacts instantaneously to the incident heat by adjusting the speed of the fans and the supply temperature of the cooling water. The challenge is rather to store the significant amount of thermal energy from the facade for later use, ideally in a seasonal storage.
The cooling and the heating functions are available all the time. On a cold summer morning, with no internal sources present, the thermal balance can necessitate some heating. On a cold day with internals sources and sun radiation the system may require a cooling.
In contrast to a room with a conventional facade, there is virtually no heat flow from the outside to the room. Therefore, only the internal heat sources, like persons, electrical appliances, or visible light need to be controlled to avoid temperature increase.
By regulating the internal temperature in the HyWin cavity, the heat flow between the cavity and the room can be either eliminated or restricted to the desired amount and direction.
In hot periods and strong sun radiation the cavity temperature will be set below the room temperature, thus providing a cooling effect to the room. The safety glass will be somewhat cooler, offering a comfortable climate in the vicinity of the window.
Conversely, in cold days the temperature in the cavity may be raised above the room temperature, resulting in a pleasant temperature up to the window. Today’s glass facade use some sort of warm air curtain to avoid unpleasant cold pane.
In essence the overall heat balance of a room consists of heat from:
The first four components of the balance are given by the room design and its use. The last component, the heat flow through the inner glass pane is controls the overall balance in the room by adapting the temperature in the cavity and thus the heat flow.