VRF air-conditioning system as an air-to-air heat pump and decentralised ventilation units
State-of-the-art heating, cooling, and ventilation in the planetarium
UrsensollenThe Ursensollen planetarium and observatory are located away from the large urban centres in the municipality of Ursensollen in Bavaria’s youngest natural preserve, the Hirschwald Nature Park. Here, the night sky is not brightened by artificial light sources and therefore offers good conditions for astronomical observations of the night sky. As part of the observatory modernisation, the municipality also focused on the construction of a new planetarium. The location posed a particular challenge when choosing the proper systems technology: Being outside the village, there was neither a water connection nor a sewer or gas connection on the site. Nevertheless, the requirements for adequate operation of the complex were ventilation, heating, and cooling.
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Requirements:
- Modern system solution for heating, cooling and ventilation
- Innovative technology not requiring any existing infrastructure
- High energy efficiency, climate comfort, and user-friendliness
- Pleasant, continuous air conditioning
- Separation of comfort air conditioning and technical cooling
- Ventilation system with heat recovery
Which solution was chosen for the planetarium?
SolutionSplit type air-conditioning units as a heat pump for cooling and heating – supplemented by ventilation units
The technical building equipment of complexes with special functions often presents planners and installation companies with particular challenges. A conventional heating system based on fossil energy carriers for the new planetarium in Ursensollen – one of only three 3D planetariums in all of Germany – was out of the question from the very beginning. A pellet system also seemed rather unattractive, as this would have required additional storage space and a chiller for cooling. So the choice was quickly made for a heat pump solution using air as the energy source. As a solution for switching from refrigerant to a heat-dissipating medium, a system concept with air-based split type air-conditioning units for cooling and heating was developed – supplemented by Lossnay ventilation units for aeration and venting. With this simple solution, a compact and highly efficient system can meet all the operator’s requirements for comfortable room air conditioning and fresh air supply. Moreover, the system concept is a particularly economical solution in terms of the investment required for the entire complex. This is because the VRF air-conditioning system eliminates the need for an additional plant room, for example for installing a buffer tank or a distribution system.
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Another aspect made an air-to-air system particularly interesting for this complex. Due to its timber frame construction, the mass of the building is very low. It can therefore be heated very quickly without having to heat up a building structure at the same time. This is a good prerequisite for the energy-efficient operation of a building that is only used temporarily. After all, the building is generally only open to the public three days a week. Fast heating or cooling operation using an air-to-air system is therefore an advantage.
Advantages of the system concept
BenefitsMaximum climate comfort, user-friendliness, and energy efficiency
The solution is a VRF air-conditioning system for heating and cooling, a split type system for cooling the plant room and two decentralised ventilation units as well as a central remote control. For comfort air conditioning, the building is equipped with a Mitsubishi Electric City Multi Y series VRF system for either cooling or heating. Thanks to its heat pump function, the VRF system can also be used for space heating and offers maximum climate comfort, user-friendliness and energy efficiency, making this technology particularly suitable for this application. Thanks to the inverter-driven compressor technology, the VRF system also allows quick and continuous adjustment of the output to the current demand of the indoor units.
In the outdoor area, a state-of-the-art PUHY-EP200YNW-APUHY-EP200YNW-Aand a heating output of 25 kW is installed. The outdoor unit supplies a total of five indoor units. Two of them – compact Euro grid 4-way ceiling cassettes – are located in the planetarium foyer, another one – a ceiling cassette – in the conference room, and the last two are ducted units located in the domed auditorium.
Pleasant, continuous air conditioning in the planetarium dome
The domed auditorium not only especially requires the air-conditioning system to ensure a pleasant climate for visitors during shows, but above all to guarantee constant temperature maintenance and stratification.
“This is particularly important for smooth operation. If the temperature deviates too much from the set-point, in this case 21 °C, the aluminium star dome would expand considerably and cause blurred images of the starry sky”, explains Dipl.-Ing. Roland Schillmaier of the executing specialist company Kälte SELEQ GmbH & Co. KG.
“We solved this challenge by installing numerous temperature sensors, which ensure precise temperature stratification in the ±2 Kelvin range and guarantee stable temperature maintenance by the air-conditioning and ventilation system during the shows”, says Schillmaier.
Concept for separation of comfort air conditioning and technical cooling
Due to the high heat generation of the central computers and projectors, cooling of the plant room is necessary during 3D planetarium operation. The dissipation of the heat load ensures smooth operation, especially during the shows. To implement the professionally recommended separation between comfort air conditioning and technical cooling, one wall mounted Mr. Slim system unit is used to cool the plant room.
With its high operational reliability and low energy consumption, the Mr. Slim air-conditioning unit is particularly suitable for applications in a plant room. Thanks to the large-surface heat exchanger and the high air flow, this device series offers high sensitive cooling capacities. In this way, room temperature and humidity can be maintained as constant as possible to ensure smooth operation of the servers and projectors.
State-of-the-art ventilation system with heat recovery
The third key requirement for the planetarium is a controlled fresh air supply. It is designed to ensure that the large auditorium with public access and the conference room are supplied with fresh ambient air. As regular air exchange cannot be accomplished by opening windows, a controlledventilation systemtakes over this task. Two Mitsubishi Electric LossnayLGH-RVX-E fresh air systemsare being used. They supply the relevant rooms with 100 % fresh air. The Lossnay unit for the auditorium was installed above the large starry sky dome. The air supply duct is located at shoulder height, while the exhaust air is extracted at the top.
Beyond that, automatic aeration and venting offer numerous other benefits. Generally, the ambient air is either too warm or too cold to be fed directly into the building. With uncontrolled ventilation, ambient air conditioning requires a lot of energy. For this purpose, the two Lossnay units are equipped with heat exchangers that ensure heat and moisture recovery of up to 80 %. This significantly reduces the required heating and cooling capacity and ensures a pleasant temperature and the right amount of fresh air for everyone in the room at all times. The free cooling function also ensures that the building is supplied with cool ambient air during the night, resulting in an even further reduction of the energy requirement.
A useful addition is theAE200for operating and controlling the system. It offers operators the option of remote access, for example to read out the operating status or any fault diagnosis data from a distance. The specialist company in charge has remote access to the system data as well and can rectify faults remotely – without an on-site visit.
The key points
Summary- The Ursensollen planetarium is a very special project that presented planners and installation companies with particular challenges.
- Lack of infrastructure, limited space and temporary utilisation intervals played a key role in choosing the proper technical equipment for heating, cooling and ventilation.
- At the same time, there were high requirements of the complex in terms of energy efficiency, climate comfort and user-friendliness.
- The solution is a system concept with a VRF air-conditioning system used as an air-to-air heat pump and decentralised ventilation units to ensure fast heating and cooling operation as well as fresh air supply.
- Thanks to its heat pump function and the absence of supply losses, the Mitsubishi Electric City Multi Y series air-conditioning system for either cooling or heating is ideal for this application.
- The decentralised Lossnay ventilation units supply the rooms with public access with 100 % fresh air.
