Optimising solar energy in building design

Optimising solar energy in building design

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By Jack Ward, CEO of Soltra Energy

One of the objectives demanded by many supporters of modern, sustainable buildings is carbon neutrality. Carbon neutral buildings are engineered to release no greenhouse gasses at all or to balance the emissions they produce using trade-offs.

These emissions usually come from electricity consumption, the burning of fossil fuels, on-site waste water treatment and a range of other processes that might be performed in the building. Key to reducing emissions is the use of renewable energy resources, of which one of the most popular and prolific is solar power.

Solar power is a clean sustainable energy technology drawing on the most plentiful and widely distributed renewable energy source – the sun. Solar power is seen as an ideal complement to the classical building design goals of economy, utility, durability and comfort.

Despite any official encouragement or support for roof-top solar installations in South Africa, many architects are realising the benefits associated with designing buildings that follow energy efficiency guidelines.

Today, architects are increasingly likely to design buildings for residential, commercial and industrial use that readily integrate solar photovoltaic (PV) panels – together with their power inverters and batteries – thereby increasing the efficiency and reliability of the installations.

Before setting out to design a ‘solar friendly’ building, it’s important for architects as well as the contractor, engineers, electricians, roofers and other installers associated with the project to have a clear understanding of the responsibilities of each party in the building process.

They also need to have specific details of the energy yield objectives associated with the project. These usually include goals for the reduction of grid-linked energy consumption to a point approaching zero.

The main starting point is to determine the maximum power that is required to be generated. Power is related to size and the designer has thus to allow for a certain number of solar PV modules to achieve a given energy output. Will there enough surface area available to install a given size PV array?

In this light, the integration of solar PV panels can be done with a view to optimising the aesthetics of the structure for a more cosmetically-pleasing result. Many examples exist of the ‘ex post facto’ connection of PV panels resulting in a distinct lack of aesthetic integrity.A good rule of thumb is that the colour and texture of the PV system should be consistent with all other materials with which it is associated.

Taking the concept a step further, the entire appearance of the building should be consistent with the PV system used. In a traditional building, for example, a tile-type solar PV system will often be more visually appealing than large modules which, on the other hand, may well suit a modern, high-tech construction.

Integrating PV systems into roofing structures is better done at the design phase when the slope of the roof can be angled optimally and attention can be paid to the strength of supporting structures. Ideally the roof should accommodate an additional loading of 20 to 25 kilograms per square metre to adequately and safely support PV panels (without tilt-tracking mechanisms).

One of the benefits of designing a green building from the outset is the optimisations that can be made in the electrical infrastructure. Essential and non-essential circuitry (from a solar perspective) can be designed and then installed at the construction phase in a simplified process, compared to a retro-fit.

For example, burglar alarms, outside lighting and key main lights inside the building can be treated as essential and given priority, while swimming pool pumps, air conditioning and similar systems can be treated as non-essential. This becomes a key exercise, especially when battery backup and storage is to be included in the design.

Solar PV systems can be attached to facades, sunshades, louvers and canopies. There is a logical combination between shading a building in summer and producing electricity at the same time.  Architects who recognise this have produced examples of solar PV shading systems for entrance protection, and many analogous systems for similar applications.

Solar PV systems can also be part of the thermal envelope of a building. One of the by-products of solar energy production is heat radiating from the back of the solar cells which can be channelled and put to good use for winter heating, particularly if provision is made at the design phase.

While solar systems have been used in many applications there are still countless new ways to be developed – a number of which are sure to lead to new architectural models possibly in combination with other types of renewable energy resources.