Research in focus

The age of positive energy balances has come

»To us, the energy turnaround is not exactly a new challenge«, says Hans Erhorn, head of the Heat Technology Department at Fraunhofer Institute for Building Physics IBP. »For almost 30 years now we've been doing research into buildings that require only a minimum amount of energy, or no energy at all«. Given the topicality of the issue, people often forget that the current debate has been preceded by decades of developing modern technologies for energy saving construction methods. A graduate engineer, Hans Erhorn has been working on lighthouse projects investigating the energy performance of buildings for many years now. He and his team can rely on a wealth of experience in this domain.

For quite a long time, experts considered zero energy buildings or buildings that do not require a heating system (as the passive house was inappropriately described) to be landmarks in this development process. The vision of a building that produces more energy than it uses for running the technical building systems (and thus becomes an energy-generating unit itself) once belonged to a distant, perhaps even unattainable future. Undoubtedly, the development of the surplus energy house marks another quantum leap in the field of energy research to which Fraunhofer IBP research staff contributed their share, proving great commitment and initiative. In the meantime, IPB's Heat Technology team has extended its scope, now providing surplus energy building concepts not only for various residential buildings, school buildings and other educational buildings, but also for office buildings and even for existing buildings. »Each of the 190 exciting building projects we have realised so far has taken us a step further«, remarks the versatile energy expert.

Politics paving the way for exploring new standards
But newly launched pilot projects need strong partners who pull together to ensure that such pilot schemes will have the necessary effectiveness. When it comes to setting and supporting sustainable trends in society, the challenge for policy is to initiate demonstration projects, to provide start-up financing, and to create the appropriate framework for change. It is equally important to involve a dedicated team that is committed to advancing the scientific implementation of the project. Hans Erhorn regards the management of German and European accompanying research initiatives as one of his key tasks. In particular, these tasks include supporting the legislative authorities in carrying out the programmes launched, partnering with practitioners in implementing these schemes, developing and monitoring demonstration projects, and eventually evaluating these projects using sophisticated measurement concepts. The high relevance of these research projects is confirmed by the fact that emerging superior trends need to be analysed in the course of the project, that guiding principles have to be derived from these analyses, and that experience gained from the project has to be summarized in guidelines, for instance. In this context, media work cannot be underestimated, as knowledge transfer and keeping the public informed are major objectives of all parties involved. Maintaining excellent relations with the ministries (particularly in the sectors of construction and economics), but also with project management organisations and building authorities or designers/ planners from the building industry is essential for a research institution, and also distinguishes energy expert Hans Erhorn.
Turning a building into a power plant
But how can a conventional building, which usually still requires a considerable amount of fossil energy for space and DHW heating (despite observing energy conservation measures) actually become an energy producer (in relation to its annual energy balance)? The exemplary surplus energy building called Effizienzhaus Plus in Berlin, which has been accompanied and intensively monitored by Fraunhofer IBP researchers from competition to evaluation, clearly demonstrates the immense development efforts implied by innovative, trend-setting projects of this kind. Such lighthouse projects are distinguished by two strategies, namely by optimizing the building's energy efficiency on the one hand while minimizing its energy need for building services and related technical processeson the orther hand. The residual energy demand of the building is exclusively covered by renewable sources of energy, which are available in the immediate vicinity of the building (like solar or geothermal energy). This may sound simple, yet involves complex technologies.
The central question is: What does it take to make a building highly energy efficient? Basic requirements include a compact structure and the optimum orientation of the building. Additionally required are optimum quality windows. All constructions and connections to building components must strictly avoid thermal bridges. Finally, high-tech control systems and technical building systems should employ the latest and most efficient technologies. The integration of  heat recovery systems in ventilation and waste-water systems will limit losses; systematically performed hydraulic adjustments in all parts of the systems involving water- and airflows will reduce the energy need for driving pumps and fans, for instance. Further, using energy-efficient domestic appliances and installing energy-efficient lighting systems (for instance, LED lighting in conjunction with systems that prioritize the use of daylight) will help to limit the energy requirement. As these buildings no longer need fossil fuels, the question of alternative fuels arises. Which renewable sources of energy are available? Glazed window surfaces can be used absolutely free of charge: firstly, they allow for passive energy gains; secondly, they reduce the energy need for artificial lighting as they provide daylight. More actively, renewable energy can be utilized by means of thermal solar collectors, biogenic fuels, geothermal energy, or ambient heat. Finally, electricity generating systems like photovoltaic systems or wind power plants help to achieve the »(Sur-)Plus«. The volume of electric power that is not used on-site is surplus electricity that will be fed into the public grid. Battery systems are used to minimize the quantity of feed-in power, so as to reduce fluctuations in the power supply and to prevent associated problems.

Verifying visionary building concepts
To ensure the application of uniform rules when evaluating the energy performance of buildings (which is a prerequisite for achieving comparability of building concept parameters), IBP's Heat Technology team has developed a calculation procedure for the surplus energy building 'Energiehaus Plus', including all its relevant energy components. This calculation procedure is currently being implemented in a series of standards and in accompanying software. In addition, IBP researchers have developed a detailed measurement concept, which allows evaluating the simulation results obtained for different building concepts. It is thus possible to verify the airtightness of the building envelope, to identify thermal bridges (by checking the correct execution of the window connections, for instance) or to detect differences between nominal (COP) and actual figures regarding the efficiency of technical building systems. The measurement configuration allows to establish a comprehensive balance of energy flows on a monthly basis, thus visualizing the performance of the installed plant components. In this way, users will keep informed on the current status of their energy balances. Besides, the air temperatures and CO2-levels measured in relevant spaces (like living rooms or bedrooms) are continuously recorded.

For instance, it will be recorded how much energy is delivered by the PV system, whether this energy is used for on-site consumption or fed into the grid, and how much electricity is used by domestic appliances. Also collected and analysed are data describing the efficiency of the heat pump, the quantity of heat the pump emits to the distribution of the heating system, and consumption values related to space and water (DHW) heating. Based on these extensive data, each concept will be evaluated with regard to its practical suitability. This verification procedure is to ensure that predicted results will prove reliable in practical applications.
In parallel with the heat supply, an evaluation based on measurements is carried out. To this end, the working data of all major consumers and the battery storage unit are recorded separately, including the volume of energy required for charging the electrically powered vehicles. These data are compared to the amount of electricity generated by photovoltaic systems and then related to the total energy requirement. In the annual balance, the electricity »yield« from the photovoltaic plant shall exceed the total consumption of electricity for habitation and E-mobility.

Transparency and transfer of research results

To prevent R&D insights from »gathering dust« on scientists' desks, IBP measurement projects are made accessible to everyone and presented on the web, like the surplus energy building 'Effizienzhaus Plus' in Berlin or the 'Museum as a low-energy building'.
Buildings functioning as energy providers create a scenario that opens up completely new ways of securing the energy supply. »To ensure sustainable success, it takes both: detailed, fully developed concepts of building types and excellent quality of building construction«, Hans Erhorn summarizes the facts. Equipped with these parameters, energy solutions for districts or even for entire cities can be tackled.


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