Zero Energy Building

A zero energy building (ZEB) or net zero energy building is a term applied to buildings with a net power consumption near zero in a typical year. In other words, the energy comes from the own building by means of renewable energy sources that will have to be equal to the energy demanded by the building

Energy demand = Energy Generation

A building that approaches an use of energy next to zero denominates near building zero energy or building ultralow energy. Those that produce an excess of energy are known as plus energy buildings.

Although zero energy buildings continue being infrequent in developed countries, they are gaining in importance and popularity. The proximity to make massive zero energy buildings implies a potential solution to a range of social and environmental problems, including the reduction of the emissions of CO2 (carbon dioxide), the reduction of dependency on fossil energy for the operation of air conditioning systems, petroleum imports and derivatives, and the rational use of fossil fuel for other uses improving problems of supplying in an energy crisis scene, increasing prices and exhaustion of the fossil resource.

The debate: generation of energy v.s. energy conservation

One of the key areas of the debate concerning zero energy buildings is on the balance between energy conservation and the use of renewable energies.

The building in its conception, construction and operation must demand the minimum amount of energy, and this minimum demand must be covered by the renewable energies. This takes us to think about the passive house next to a power efficient building. This, on the other hand, implies to surpass the standards proposed by the norms and codes of construction of the majority of the countries that has these instruments of regulation of the energetic quality of the construction.

However, whereas it recognizes that the energy conservation is an important piece in the game, another good part of the designers it considers that this is has lower importance and valorizes in greater degree the “active” techniques (photovoltaic solar energy, wind energy, etc.) to compensate the energy / heat deficit.

Generation of energy

In the particular case of individual houses, several technologies of microgeneration provides heat and electricity to the building.

- Electricity: by means of solar cells (photovoltaic), aerogenerators (Aeolian energy) and fuel cells (hydrogen).

- Heat: by means of thermal biocombustibles, biomass, solar collectors (hot water, hot air, steam to low pressure), accumulation in the thermal mass of the building, water walls, Trombe-Michel walls, among others thermal strategies of the bio-climatic arsenal. Synthesized in the passive house. These heating techniques can offer, refreshment and refrigeration to atmosphere of the house or building. Between the most recent developments is the phreatic heat accumulation by which wells with depths between 40 become and 70 ms of approximately 30 cm of diameter are created. Thus the heat of the summer is accumulated to be used in winter and viceversa. The most well-known example is the building of the German Parliament in Berlin by the architect Norman Foster.

-* Fluctuations in the demand: In order to battle against fluctuations in the demand of heat or electrical energy, the zero energy buildings, usually are connected to the network and their wn measurers of double via. In this way they export electricity during the day and they import it during the night. The great advantage is to avoid the high costs of the stationary batteries and their maintenance to accumulate the electricity. A policy of subsidies is required, and specific legislation to implement it. It is very difficult in countries where the services are private and power of the state is weak. Another possibility is that buildings were completely independent (not connected to the network), but the initial costs are hardly recovered without subsidies.

Residential districts or zero energy sets are feasible, as for example BedZED constructed in England although there are several examples in Germany. In these cases the concept of generation distributed along with district heating is used. Zero energy are recent examples of construction of whole cities as the case of Dongtan near Shanghai in China. In Japan urban sectors with heating and district refrigeration have been equipped distributing to hot water and cold water like a public service more

Design and Construction

In order to reach a minimum use of the energy, the design and construction of zero energy buildings are different significantly in their formal image of the conventional buildings. In the buildings of conventional design the emphasis is normally in the reduction of the cost of initial construction to the minimum. The designers do not consider costs of maintenance, operation, air conditioning, analysis of the service life of energy; being satisfied with fulfilling, to the limit, the established thing in the codes of construction of the place.

In position EEC each decision on the important selection of each edilicio subsystem, evaluates in terms of its future consequences with respect to its energetic demands, for which the technique of power analysis of service life is used. The EEC designers admit an increase of the initial cost of construction, if with this, they manage to reduce to the demand energetics and the expenses of operation. A postulate for the design of an EEC is the first energy.

Besides using renewable energies, the buildings zero energy also are designed to make use of the gained energy of other sources, including electric home appliances, efficient illumination and advantage of metabolic heat (people). The buildings are optimized to take advantage of the sun energy (passive house), use of the thermal mass with the purpose of maintain constant inner temperature independent of the external variations of temperature, elevating in addition the inner average temperature in several degrees with the purpose of reach the comfort with the aid of heat insulation or superisolation. At present it exists all the knowledge and mature technology to construct an EEC.

Designers typically use sophisticated tools of numerical simulation that allow to consider an ample range of design variables such as direction of the building ( respect to the sun), the type and location of windows, the shades projected by the other buildings or the own building on itself, the depth of the glass finish with respect to the outer surface of walls, the values of the heat insulation in edilicio house subsystem, sensible heat content and latent heat of the air, the efficiency of heating, illumination and other equipment as well as the local climate. These simulations help designers to say if the building behaves before it is constructed, and it will allow them to model financial implications and costs of construction.

The designer architect usually contracts environmental or bio-climatic experts as advisors and provides the initial steps who soon will be adjusted. Usually the environmental consultant is trained by a interdisciplinary or transdisciplinary team in which participate, architects, industrial engineers, physiques, designers and technologists. This based on the magnitude and complexity of the building.

Solar Energy is becoming today’s future

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