Montoring program for an optimasation of new type of energy supply system with heat pump and battery storage for single family houses

Project  was to document and optimize the energy systems of the future for single-family homes, for which oil burners and gas boilers can be replaced by new fossil-free, aesthetic and comfort assured solutions based on innovative PVT-E modules.

In principle the system can be seen as similar to geothermal installations, in which all year, day and night, liquid-filled pipes bring clean energy from the environment to a heat pump inside the house. This heat pump then converts the energy to hot water and heating. The difference is that, in addition to bringing energy from the surroundings to the house, PVT-E has several other additional features:

• (A) PVT-E modules produce power from solar cells for the electricity consumption of the house and for operating the heat pump. There is therefore no need to buy power from the grid for the heat pump.
• (B) In contrast to geothermal installations, the PVT-E modules have built-in fine, thin pipes placed under the solar cells, saving the costs of digging up the garden.
• (C) PVT-E modules can also be compared to air-to-liquid heat pumps, which draw energy from the air 24 hours a day. But since PVT-E has no movable parts, they produce no noise and require no maintenance.
• (D) PVT-E modules can constitute the fixed self-supporting roof of the house itself or they can protect an underlying roof from degrading UV-light and general wear and tear.
• (E) During summer and on sunny days, the PVT-E module functions as a solar collector, absorbing the sun’s heat radiation.
• (F) On clear and dry nights, the PVT-E modules can emit heat and draw large amounts of cold to a storage tank, which can be used for cooling the building during daytime. The advantages listed here constitute many parameters which have to be coordinated and can only be utilized through safe and intelligent control software for optimal functioning of the energy system.
   

Other challenges for the control software are the parameters due to the fluctuating dynamic consumption of electricity and heating by the inhabitants of the house, also may be due to electric cars, changing weather conditions, variations in tariffs for exchange of energy with the grid etc.

The present project is crucial for gathering the many types of data and for documenting the interplay between the various energy flows in order to finally be able to optimize all components of the energy system and the control software. With these measurement data and experience gained, the project enabled the design of more effective and less costly PVT-E systems.

The ELFORSK project clearly documented that the concept and the system work. In addition to the house in Stengården the results were based on the dimensioning and implementation of optimized energy systems for two additional single-family homes. A further upgrading would be crucial for Denmark’s 400,000 homes that are not connected to the district heating network in Denmark and that are powered by oil burners and gas boilers. Optimization of components (work package 1 - WP1) was initially based on simulations for 5 different single-family homes respectively in Arnager on Bornholm and in Stenløse, Gentofte, Virum and Kirke-Såby on Zealand.

For the first installation, the house in Stengården, the simulation programs used were not yet fully developed. At the same time as the heat pump did not tally with the PVT-E concept. Similar problematic issues applied to the battery and its control software. Likewise, the prototype PVT-E elements were too heavy and costly. However, many measurement points were set up on 8 different PVT-E module types (e.g., with or without in-built insulation), enabling the revision of the simulation program so that it could include unknown parameters and finally correspond to the data measured. Notably point (F) turned out to create problems since the radiation of heat in PVT-E on clear winter nights brought the temperature down to a level where the heat pump already at -2°C could no longer keep up. After a winter period, it became clear that all components tested in Stenløse had to be changed significantly and optimized. The following optimization of components provided beneficial new features applied to the two houses in Gentofte and Virum. These new features included new PVT-E module types; new mounting types; new heat pumps with bult-in control software; new inverter and battery types, in addition to new control systems and units with redundant control system possibilities.

Design of measurement program, data collection and optimization of control systems (WP2) were set up in more advanced form and can now be further developed together with new interfaces that might continuously emerge with the introduction of new upgraded components such as heat pumps, inverters and batteries and their individually dependent control systems. For the houses in Gentofte and Virum simpler control systems were also tested to reduce the costs of the entire energy installation.

The control system for and the development of the forthcoming heat pump from Metrotherm will be able to manage the low temperatures during the winter down to -15°C.

Examination of design material (WP3) led to that the design material for the pilot energy installation, as part of the planning of the monitoring package, was examined with the aim of incorporating the results of the activities from WP1 and WP2. An important result was the design of four fixed sizes of energy systems as four standard systems which tally with different typical single-family homes and their energy consumption, to avoid having to tailor a special system for every single house. Likewise, the entire PVT-E system can easily be built up as a modular system with the same common components.

Analysis of the measurement-data of the construction concept regarding the goal achievement (WP4) gave amongst several results, notably one important result i.e., it was financially interesting to connect several houses to one common heat pump and a common battery storage, for instance 5 houses in a group. Already for the first installation, the house in Stenløse, we managed to obtain indoor climate comfort and stable energy supply. However, low investment costs, achievement of better payment conditions, and efficient use of the energy of the installation had to wait till the PVT-E installations were in place on the houses in Gentofte and Virum.

Prospective analysis (WP5) for the utilization of the concept regarding e.g., more electric cars; individual installations vs. energy communities; common storage facilities; common components for groups of houses are needed. Socioeconomic investigations show that there is a variety of possible solutions but also great uncertainty about the economy if there is an exchange of energy across houses or an interconnection with the grid. Therefore, during the project, we developed optimized designs and system concepts where the focus was on individual systems, cost efficient components, high energy yield, a flexible multifaceted system, and safe and stable control regarding comfort. Flexibility created the possibility to link up with future energy communities.

An important aspect was that the energy consumption and energy gain of each component can be measured and used as a basis for later distribution of operating costs and energy gains. The measurement program and the optimization goals of the ELFORSK project thus became the key to future system designs.

The assessment is that with the expected cost reduction of the components of the PVT-E systems; withcost effective and simple mounting; and by utilizing the flexibility of the multifaceted system plus using the modules as actual useful building elements, then the economy for such installations will be competitive with most other non-fossil energy systems for housing. The expectation is that mass production of both PVT-E modules and related heat pumps with built-in control will quickly take over the market for supplying single-family homes with electricity, heating, hot water, and cooling. Since we are dealing with island systems and a high degree of self-sufficiency, a payback time of 5 years independent of electricity tariffs will be realistic already in 2023.