Abstract
The Zero Village Bergen consists of a total floor area of ca. 92 000 m2, with more than 700 dwellings divided between terraced houses (68% of total floor area) and apartment blocks (25%) and some area dedicated to non-residential purposes such as offices, shops, and a kindergarten (7%). The project is currently in the planning phase and the strategy for achieving the ZEB-O goal1 is based on three steps: first, minimize energy demand through energy efficiency of the buildings; second, maximize PV generation on the buildings' footprint; and third, consider additional measures onsite and nearby (e.g. local heating system with biomass based cogeneration). At the current stage the project has reached the evaluation of step two, and the results are presented in this report, together with some useful insights for step three.
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Abstract
Zero Energy Buildings (ZEBs) are considered as one of the key elements to meet the Energy Strategy of the European Union. This paper investigates cost-optimal solutions for the energy system design in a ZEB and the subsequent grid impact. We use a Mixed Integer Linear (MILP) optimisation model that simultaneously optimises the building’s energy system design and the hourly operation. As a ZEB have onsite energy generation to compensate for the energy consumption, it is both importing and exporting electricity. The hourly time resolution identifies the factors that influence this import/export situation, also known as the building’s grid impact. An extensive case study of a multi-family house in Germany is performed. The findings show that the energy system design and the grid impact greatly depend on the ZEB definition, the existing policy instruments and on the current energy market conditions. The results indicate that due to the feed-in-tariff for PV, the cost-optimal energy design is fossil fuelled CHP combined with a large PV capacity, which causes large grid impacts. Further, we find that heat pumps are not a cost-optimal choice, even with lower electricity prices or with increased renewables in the electric power system.
Abstract
Modeling simplification related to occupant’s behavior is a major cause of gap between actual and model’s predicted energy use of buildings. This paper aims to identify those parameters of realistic occupants-related heat gains that actually cause this gap. The investigation therefore, systematically distinguishes the occupant behavior using three behavior parameters, namely: the occupancy behavior, the appliance use behavior and the family size. The effect of these parameters is investigated on a building for two different insulation standards using heat pump as energy supply system. The results identifies the occupancy patterns and the household size as two major parameters that explains a large portion of the gap between actual and model’s predicted energy use of the building. Results further show that variation in household sizes is an important parameter to understand the variation in the actual energy use for similar buildings. The study also shows a clear influence of occupant’s behavior on the performance of heat pumps and pinpoints the variations in share of space heating needs compared to domestic hot water needs as a major cause for this influence. Sensitivity of findings is tested against building thermal mass and condensing gas boiler. Analysis shows no significant variations in the conclusions. The study therefore concludes that using identified parameters in modeling practices can contribute to improve the prediction of actual energy use of buildings.
The aim of the Norwegian research centre on Zero Emission Buildings(ZEB) is to develop competetive products and solutions of buildings with zero emission of greenhouse gases related to their production, operation and demolition.
However, to develope solutions and concepts for zero emission buildings it is first necessarry to develop a sound definition of ZEB (for single buildings, and also cluster of buildings). During the first 3 years of the centres running, significant work have been done to adress different issues related to the ZEB-definition, among them defining CO2 factors for various energy wares. Work done in the International Energy Agency (IEA), and European organisations in light of the revised Energy Perfomance Buidling Directive (EPBD) have been an important basis for the ZEB-defintion work. Experience from the design process of 7- 8 ZEB pilot building projects comprising approximately 100 000 m2 floor area has also been an important background for the agreed ZEB-definiton. The ZEB-definition consist of nine points
Improving the interaction between Net-ZEB and the grid using advanced control of heat pumps
Authors:
Design principles in Net-ZEB considers the local energy infrastructure as virtual storage leading to large amount of energy exchange with the grid. Nonetheless, with high Net-ZEB penetration scenarios, such exchange could compromise the effectiveness of Net- ZEB concept in a total energy infrastructure. As the current market trends, heat pumps along with photovoltaics are seen as an emerging energy supply solutions in Net-ZEB buildings, effectiveness of an all-electric Net-ZEB (that is using air-to-water heat pump with photovoltaic) is analysed. Two concrete control cases of energy storage (compared to reference case) to assess Net-ZEB ability to self-consume vs. grid empowerment are studied. Results shows that introduc tion of storage buffer in such concept leads to a flexibility of almost 6 % in self-consumption and 13 % in grid-impact factor and in-turn provide significant manoeuvring space to the demand-supply balance at the grid level.
It is becoming conventional approach to evaluate the building envelop losses using detailed dynamic tools such as EnergyPlus, ESP-r and TRNSYS. However, the user-related loads (and their variations) in the building are usually oversimplified during performance evaluation of those buildings and associated HV AC systems. This paper presents a methodology to evaluate the performance of buildings and their energy supply systems while taking into account the user-related loads (non-HV AC & DHW) at individual household levels. For this purpose, a single family house (two different insulation cases) built in Oslo climate using an alternate duty air to water heat pump is used as a case study. The investigation shows that a large variation occurs in space heating needs for the same standard house when actual user loads are considered. The study also shows that the storage losses dominate the performance of total heat supply system in case of passive house insulation.