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Net zero energy- , energy-plus or climate-neutral buildings in the next generation of electricity grids

Net zero-energy buildings and energy-plus buildings demonstrate just what is possible. With these buildings, a neutral annual energy balance can be achieved by integrating architecture, energy efficiency and renewable energy sources in a systematic manner. These new breeds of buildings are liberating themselves from dwindling fossil energy sources and rising energy prices. The operator of a net zero-emission building will thus no longer be contributing to climate change.

Attention generally turns to our buildings whenever climate change is the focus of public debate and the right energy policy is being discussed. Indeed, this attention is fully justified. Living and working in buildings is responsible for large proportions of energy consumption and greenhouse gas emissions. This applies to the entire lifecycle – from the construction, maintenance and use of buildings right through to their deconstruction. However, proven approaches and measures to drastically reduce energy requirements and emissions are available for all types of buildings.

Energy-independence demonstrates the potential, but not the direction to be taken

Energy-independent buildings show just what can be achieved under extreme conditions: Independently of any grid infrastructure, it must also be possible to meet their energy requirements using renewable energy sources alone even when they are not connected to an energy grid. This is technologically feasible, but is not ideal when energy grids are actually available. The considerable amount of equipment that is necessary for stand-alone energy supply demonstrates that this is not a model for the future for our cities and residential estates. The main engineering bottleneck here proves to be the storage of energy over longer periods – this particularly applies to electricity. For this reason, it is a significant advantage if the building is connected to the public electricity grid. After all, buildings are both electricity consumers and electricity generators in the next generation of electricity grids.

A grid connection is desirable, but…

A building only achieves climate neutrality when more renewable energy is generated on site than is consumed or when electricity grids are based 100% on renewable energy. Until this becomes possible, buildings can be supplied with certified “green electricity”. However, green electricity is definitely too precious to be wasted due to poor building efficiency. What’s more, the large-scale changeover to electromobility that is taking place will leave little room for wasting energy. As long-term storage of electrical energy is not employed in net zero-energy buildings, the public electricity grid has to carry out this function. The grid balances the (seasonal) variations in energy generation and energy generation, which also fluctuates. In the future, buildings will be integrated more closely into generation and load management than before. The grid infrastructure will be able to operate in a reliable manner even with a significantly higher proportion of electricity from renewable sources only with the help of so-called smart grids.

Buildings as decentralised power plants

In contrast with vehicles, buildings offer sufficient surface area, space and infrastructure for implementing decentralised energy generation and grid feeding. Solar power systems are suitable for this purpose. Cogeneration systems that are integrated into the building are also an option, particularly in the case of larger, energy-intensive non-residential buildings. In the future, these will increasingly be run on biomass. Today’s net zero-energy buildings are often so-called “all-electric buildings”. This particularly applies to residential buildings. Their energy systems are confined to solar energy systems and heat pumps, meaning that electricity is the only energy carrier used.

Net zero energy, energy-plus & co.

More and more net zero-energy and energy-plus buildings are being constructed worldwide, especially in Germany. The design and realisation of these buildings is not necessarily easy, but proven approaches and technologies are already available. We present here projects that have been implemented around the world, along with a current architecture competition in this area. We will also investigate issues regarding the methods employed – how are balances carried out for net zero-energy buildings in a fair and accurate manner, and how are the boundaries of the building system defined?

Net zero-energy buildings as built reality

It all started off with initial experimental projects that were often conceived as small, energy-independent buildings with no connections to energy grids of any kind. The origins of (net) zero-energy and energy-plus buildings can be traced back to the early 1990s. Since around the year 2000, the number of constructed projects has been rising steadily. These projects now generally involve buildings based on the passive house concept or the Minergie standard. They achieve a neutral or positive energy balance with the aid of cogeneration or solar energy systems. We present here three sample projects from Germany.

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International projects on carbon neutral buildings

Net zero energy and energy-plus buildings – these are pioneering concepts first and foremost that still have to be specified in detail and analysed for broader use in the construction sector. It is worthwhile looking at what is happening outside of Germany in this field. Which approaches are being taken in other countries? How is balancing carried out? Which technologies and systems are being used? An International Energy Agency (IEA) research group has been working on these issues since October 2008. As part of this project, which is entitled “Towards Net Zero Energy Solar Buildings”, experts from 19 countries are documenting and analysing sample net zero-energy projects from 19 countries.

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Architectural competition for net zero-energy projects

These competition entries set the standard for the buildings of the future. Over the following pages, we present the building designs that have been honoured with the German Federal Ministry of Economics and Technology’s “Architecture with Energy 2011” award. These entries are impressive in terms of design, technology and the conceptual approach taken. In addition, they boast very low energy requirements in their annual balances.

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Energy-plus buildings in European competition for university-level institutions

This third-level competition takes the form of an architectural decathlon: teams of students from all over the world build small energy-plus buildings as part of the Solar Decathlon Europe, an offshoot of the competition with the same name that is held in the USA. The entries have to prove themselves in the disciplines of Architecture, Engineering and Construction, Comfort Conditions and Sustainability. In 2010, four German universities took part in the competition in Madrid. The teams achieved excellent placings. Details of the four very innovative buildings by the universities in Rosenheim, Stuttgart, Wuppertal and Berlin can be found on the following pages.

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"Net zero energy buildings"

International projects of carbon neutrality in buildings

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Publications

Here you can find some professional articles:

Net zero energy buildings
A consistent definition framework
Energy and Buildings, Elsevier, 13 S.

Zero Energy Building
A review of definitions and calculation methodologies
Energy and Buildings, Elsevier, 9 S., PDF, 399 kB

Criteria for Definition of Net Zero Energy Buildings
Presentation at the Euro Sun 2010 Conference in Graz
Euro Sun, 8 S., PDF, 126 kB

Load Matching and Grid Interaction of Net Zero Energy Buildings
Presentation at the Euro Sun 2010 Conference in Graz
Euro Sun, 8 S., PDF, 836 kB

Net Zero Energy Solar Buildings
An Overview and Analysis on Worldwide Building Projects
Euro Sun, 9 S., PDF, 391 kB

Net Zero Energy Buildings
Calculation Methodologies versus National Building Codes
Euro Sun, 8 S., PDF, 58 kB

From Low-Energy to Net Zero-Energy Buildings
Status and Perspectives
Journal of Green Building, Volume 6, Number 1, 12 S., PDF, 954 kB

Goal: Zero Energy Building
Exemplary Experience Based on the Solar Estate Solarsiedlung Freiburg am Schlierberg, Germany
Journal of Green Building, Volume 4, Number 4, 8 S., PDF, 339 kB

Ziel Null Energie
Erfahrungen am Beispiel der Solarsiedlung Freiburg am Schlierberg
DBZ 1/2009, Bauverlag, 4 S., PDF, 170 kB