net zero energy
chapter: 2
Net Zero Buildings
The concept of a Net Zero Buildings is getting more and more attention and is currently being implemented in some form or the other in South Africa and other countries worldwide. Currently a limited number of building could qualify as Net Zero Buildings, but developments in energy saving and renewable energy technologies, building materials and construction techniques are advancing rapidly, enabling Net Zero to become a mainstream requirement for new developments. As with any evolving field of attention, several definitions exist for Net Zero Buildings. However, it is commonly understood that a Net Zero Building combines a design to minimise energy requirements with the generation of energy by means of renewable energy technologies. The NREL publication “Zero Energy Buildings: A Critical Look at the Definition” explores definitions in detail, and it suggests four ways in which net zero energy may be defined: • Net Zero Site Energy: A site Zero Energy Building produces at least as much energy as it uses in a year, when accounted for at the site. • Net Zero Source Energy: A source Zero Energy Building produces at least as much energy as it uses in year, when accounted for at the source. Source energy refers to the primary energy used to generate and deliver the energy to the site. To calculate a building’s total source energy, imported and exported energy is multiplied by the appropriate site-to-source conversion multipliers. • Net Zero Energy Costs: In a cost Zero Energy Building, the amount of money the utility pays the building owner for the energy the building exports to the grid is at least equal to the amount the owner pays the utility for the energy services and energy used over the year. • Net Zero Energy Emissions: A net-zero emissions building produces at least as much emissionsfree renewable energy as it uses from emissions-producing energy sources. In general, when using the terminology “Net Zero Energy Building”, we are referring to a building for which the annual amount of energy used in its operations is equal to the amount of energy generated by the building. If the amount of energy produced by the building is exceeding the amount of energy used, we are talking about Net Energy Plus Buildings.
How to reach Net Zero Energy?
Net Zero Energy can be reached in three easy steps: 1) Sustainable design 2) Reduce energy consumption 3) Renewable energy generation
Sustainable design
For a sustainable design of a building we will have to look at passive solar design foremost. Orientation of the building, fenestration and daylighting, ventilation, insulation and materials use as well as heat and cold sinks are the most important elements to look into.
Reduce energy consumption
A very critical look at the energy consumption in the building is required, with a specific emphasis on the use of energy efficient lighting, high energy efficient appliances, water saving shower heads, motion detectors, etc.
Renewable energy generation
The most obvious form of renewable energy generation for buildings is using the roof (and façade) for solar PhotoVoltaic (PV) electricity generation and solar thermal energy generation for hot water, but also wind energy could be considered. If the location of the building allows, on-site energy generation with biogas or small hydropower are options as well. Alternatively the energy use at the building site The green building handbook
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