SmallHouse IV

A new building component was developed as part of the LEXU+ research project. It enables the renovation of existing buildings by utilizing the building structure through active temperature control of the exterior walls. The sandwich facade element was technically and statically developed in advance, as well as energetically simulated. A monitoring phase of one year is planned to validate the effect of an existing wall renovated with the SF element on the thermal building behavior. For this purpose, the developed sandwich facade element was installed in the large-scale demonstrator SmallHouse IV at the RPTU Kaiserslautern-Landau on February 7, 2023.

The new heat pump can adjust the thermal power. This changes both the electrical power consumption and the efficiency (COP). In order to study this in detail, additional measuring equipment has been installed, which allows to measure the electrical voltages and currents. Thus, the electrical power can be determined and the efficiency (COP) of the heat pump can be determined by comparison with the thermal power.

The new LEXU+ project is concerned with the development of a new facade element for the energy-efficient refurbishment of existing buildings. For this purpose, a sandwich element for holistic low-exergy temperature control is being developed and tested. After researching the technical and static requirements, as well as the thermal simulation of the facade element, a demonstrator for the Small House IV will be built towards the end of the project and the theoretical results verified by its monitoring.

A variable speed heat pump replaced the existing heat pump. On the one hand, this allows adapting the thermal power output to the thermal demand or the electrical supply. On the other hand, the new heat pump has several more measuring points, so further information, such as temperatures or the operation status of the pumps, can be monitored. Thus, it is possible to investigate speed-controlled heat pumps in detail, especially in storage unit interaction. In addition, it is possible to take into account the supply of electrical energy, e.g. from a photovoltaic system, when controlling the heat pump. Essential findings in this area have already been obtained in the ThermSpe4EE project.

The new MULTIFACE project is concerned with the development of a multifunctional, slim and thermally insulating facade element. After researching the technical and static requirements and the thermal simulation of the facade element, a demonstrator for the Small House IV will be built at the end of the project period and the theoretical results verified by its monitoring.

A multifunctional structural component was developed as part of the MuFuBisS research project. This building part allows the load-bearing shell of the element to be heated via functionalised reinforcements. It is also equipped with a hydraulic thermal activation in the core of the load-bearing layer. The heat flux to the interior can be controlled via adjustable thermal insulation. By monitoring the building part, further findings are obtained, such as the influence of thermal activation on thermal bridges and controllable thermal insulation.

Pressure sensors were installed in all circuits and connected to the measuring system to monitor the heating system. These allow the pressure in the heating system to be monitored and thus detect leaks or excessive system temperatures at an early stage, as this permanently changes the pressure in the system.

The control of the heating system has the task of maximising the solar yield and thus minimising the need for electrical energy. For this purpose, the control system, which was initially developed using simulations, must be adapted to actual conditions and available measurement data. For example, overheating of the solar thermal collector in summer must be prevented.

The more than 150 temperature measurement sensors and the control system for the heating system are connected to the CuroControll-Box interface and set up. As a result, control programs and measurement results can now be generated that span multiple heating periods. Thus, the measurement results can be used to observe the efficiency and effects of the control and heating systems.

The concrete-look floor slab was sealed. Thus, the abrasion is minimised, and the concrete is protected against penetration of liquids.

The heart of the SmallHouse IV is the heating system, which is essential for the energetic use of the multifunctional building parts. For this, a heating system including control was developed. This system, consisting of, among others, solar thermal, buffer storage and heat pump, was installed. In addition, the multifunctional building parts and the ground storage were hydraulically connected to the heating system.

The large-scale demonstrator is designed so that individual wall components can be subsequently replaced. This should make it possible to investigate different component cross-sections in the existing energy concept of the Smallhouse IV. The first two exchangble test walls will be used for this purpose.

After completing the floor slab, the previously manufactured thermally activated sandwich elements were placed in their final position, anchored and connected to the distribution pipes in the floor slab.

The solid absorbers on the roof of the building are the second heat source of the heat pump and the ground (storage) below the building. These absorbers consist of a 7 cm thick outer concrete slab with an integrated pipe register. They are intended to counteract the daily fluctuations in air temperature and thus reduce the energy consumption of the heat pump.

As the last work step on the 30 cm thick floor slab, the formwork is filled with about 13 m³ of concrete. During concreting, the floor slab is provided with anchor sleeves to fasten and support the components to the floor slab later on.

The upper reinforcement layer is attached to the already existing reinforcement after completing the piping. Two circuits will then be attached to the top reinforcement. Once completed, these two pipe registers will lead to a near-surface thermal activation of the floor slab, which will then be connected to the ground storage tank via a heat pump.

After completing the formwork, the bottom reinforcement layer and the stirrup reinforcement are placed. Then, the distribution pipes are routed from the technical block to the outer edge of the floor slab. These pipes will later connect the control and regulation elements of the technical block with the thermally active walls, the solid absorbers, the ground storage tank, the heat pump and the solar collector.

A layer of filter material is first applied to the surface of the ground storage tank, followed by 200 mm of insulation. The insulation results in thermal decoupling between the ground storage tank and the building.

After completion of the insulation work, a formwork is created to be able to concrete the 300 mm thick floor slab.

The ground storage tank is insulated via a 14 cm thick insulation apron to reduce lateral heat losses to the ground. The excavation pit is backfilled with the excavated material and compacted in layers. Thus, the ground can serve as a storage medium and store heat in the medium to long term.

Four circuits are laid on the bottom of the excavation pit to introduce heat into the ground. These circuits serve the solar collector for thermal loading and the heat pump for thermal unloading of the ground storage tank. The pipes are covered with concrete for optimal heat transfer to the ground.

For medium- to long-term thermal storage, heat is stored under the floor slab of the large-scale demonstrator in the so-called 'ground storage tank '. For this purpose, an excavation pit with a depth of 140 cm will be dug.

On 24.11.2016, the foundation works of the large-scale demonstrator 'Smallhouse IV' started on the Smallhousevillage site. A small settlement of walk-in model buildings is being built on this site to demonstrate innovative construction methods. The research approach of 'Smallhouse IV' deals with one of the central problems in using renewable energies: storage. The core is the short- to medium-term buffer storage of heat in the massive concrete components and the medium- to long-term storage in the ground.

After completion of the planning phase, the production of the precast concrete elements in sandwich construction was started by means of the formwork plans prepared. These sandwich elements consist of 7 cm facing shell, 14 cm insulation and 21 cm core-tempered load-bearing shell. In addition to the static function, these components also perform the thermal functions: Heat storage, air conditioning and thermal insulation.

The necessary plans were drawn up based on the energy, static and architectural requirements. In addition, the building application for the construction of the large demonstrator on the premises of the TU Kaiserslautern was prepared with all necessary documents.