The main objective of this paper is to contribute to the discussion on the role of Net Zero Energy Buildings (Net ZEBs) on future energy systems by the interplay between on-site generation and the building loads, often called load matching, and the resulting import/export interaction with the surrounding electricity grid, commonly named grid interaction. This investigation analyzes five case studies with high resolution data, three of which are based on real monitored buildings. The research aims at selecting and suggesting a limited set of quantitative indicators that: (a) can provide practical information for building as well as grid designers and operators, and (b) are understandable for a wider audience and do not require complex simulation tools or additional resources. This paper also presents novel graphical representations describing the yearly or daily variation of the indexes in an understandable manner.
It has been found that the hourly values of the cover factors (namely, the load cover factor and the supply cover factor) provide quite a good picture of the correlation between on-site demand and supply of energy. These factors illustrate both the daily and seasonal effect, the production pattern of different renewable energy technologies, and applied operation/control strategies. The loss-of load probability factor shows how often the on-site supply does not cover the on-site demand but it provides limited information. Several grid interaction indicators are presented in a normalized form based on the connection capacity between the building and the grid. The generation multiple is an index that compares peak values of exported/imported energy; it may also be used with generation/load values. The dimensioning rate and the connection capacity credit relate the building with the electrical grid. These indexes can be used to analyze individual buildings and extend their use in the case of cluster of buildings. Although some general trends have been identified in the results and the usefulness of these indicators is demonstrated, it should be noted that further studies are needed in order to define reference values for particular building topologies, clusters of buildings and climates, which could be used as a rule-of-thumb for grid/building designers.
The passive house (PH) standard is seen as the future minimal requirement for buildings in Norway, where a specific definition has been developed (NS 3700). Nevertheless, the relation between this standard and air heating (AH) is not clear while both concepts are often associated. The present contribution investigates challenges for AH in terms of thermal dynamics (e.g. temperature distribution and control) as well as the feasibility of the AH concept. This is done using detailed dynamic simulations on a typical detached house typology. Results show some limitations of the AH concept in Nordic countries, as well as provide guidelines for the design procedure.
The Research Centre on Zero Emission Buildings - Annual Report 2012
Monodisperse hollow silica nanospheres have been prepared by using a polystyrene nanosphere template-assistant approach and their potential as antireflection (AR) coatings for window applications has been discussed. The as-prepared hollow silica nanospheres have a typical inner diameter of 200 nm and a shell thickness of 15–20 nm. The AR effect over the ultraviolet-visible-near infrared spectral region has been observed for the hollow silica nanospheres, with a minimized reflection of about 5.2 % at 500 nm, compared to 8.5 % of a plain float glass substrate. By modifying the structural features of the hollow silica nanospheres, their AR properties can be further enhanced.
A large amount of the buildings in Norway is from the 1970s. Many of these buildings have timber frame walls and are now ready to be retrofitted. Application of vacuum insulation panels (VIPs) can make it easier to improve the thermal insulation in building walls with a minimal additional thickness. Retrofitting of buildings using VIPs may therefore be done without large changes to the building, e.g. extension of the roof protruding and fitting of windows. Additionally, U-values low enough to fulfil passive house standars or zero energy building requirements may be achieved. Thus, contribute to a reduction of the energy use and CO2 emissions within the building sector. This work investigates two different ways of retrofitting timber frame walls, one with VIPs on the cold side and one with VIPs on the warm side. A wall module containing four different fields is built and tested between two climate rooms with indoor and outdoor climate, respectively. The module consists of one reference field representing a timber frame wall built according to regulations in the 1970s in Norway, and three fields representing different ways of improving the thermal insulation of the reference field with VIPs. As VIP is a vapour tight barrier, the fields are tested with respect to condensation risk. A new sensor for measuring surface condensation called the wetness sensor is introduced. The results of the experiment show that this method of retrofitting may be acceptable in certain structures within limited climate zones, humidity classes, and building envelopes.
Solar technologies in the form of photovoltaics and thermal collectors have not been used to the expectation specially in building sector to replace the use of fossil fuels. The main reason for these technologies not being popular in building integration is the lack of good architectural quality rendered not meeting desired design considerations. Hence, the objective of the thesis is to pave possible ways of integrating these technologies into buildings, both on existing and new constructions to add emphasis on the overall architectural expression in addition to producing energy. Basic focus is on the appearance of aesthetics part of integration as this makes the major impact on the people. PVs and thermal collectors can deliberately be used as architectural design elements in a distinctive way. Integrating these systems into buildings is not only for clean energy but also to use them as multifunctional elements where they replace the conventional building elements.
The building skin is often called the third skin of a human being after the body skin and clothes since it provides protection from the elements, creates privacy and provides contact between the indoor and outdoor space. Moreover, it is the most important element regarding the total energy balance of buildings. Solar energy systems, and in particular solar cells, have an important role to play in reducing energy needs of buildings. Several building surfaces are ideally suited for the use of solar panels, but high costs as well as technical and aesthetical considerations have long kept building owners and architects from using even a small part of this potential. The paper is the result of a study that investigates the architectural potential of existing photovoltaic materials and product development trends. The main goal is to give an overview of current possibilities and discuss their relevance for future development regarding architectural integration.