Construction World March 2015

CONSTRUCTION WORLD

MARCH

2015

ENVIRONMENTAL ENGINEERING

Background

This requires close co-operation between the

design team, the architects, engineers, and

the client at all project stages.

One of the objectives demanded by

many supporters of modern, sustainable

buildings is carbon neutrality. Carbon

neutral buildings are engineered to release

no greenhouse gases at all or to balance the

emissions they produce using trade-offs.

These emissions usually come from elec-

tricity 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 planet’s most

plentiful and widely distributed renewable

energy source – the sun.

Emerging green building design prac-

tices accept solar power as an ideal comple-

ment to the classical building design goals of

economy, utility, durability and comfort.

Embracing solar power

Today, designers and architects are looking

beyond the now traditional solar-powered

hot water geysers – which remain important

elements in solar-powered buildings – to

embrace the full extent of solar photovoltaic

(PV) power generation.

Solar PV installations convert solar

radiation into direct electricity current

using semiconductors that exhibit a photo-

voltaic effect. Solar PV panels or modules

are composed of a number of solar cells

which transform sunlight into electricity

without the need for moving parts or envi-

ronmental emissions.

How solar PV system

works

In a solar PV system the PV modules are

connected to create an array, either in series

or in parallel configurations depending on

specific voltage and current requirements.

Combiner boxes are used to combine the

inputs from multiple strings of modules into

one output circuit.

An important component of any array is

the inverter which converts the DC current

from the PV modules into an alternating

current (AC) that can connect seamlessly

to a building’s conventional electricity

wiring circuits.

In a grid-tied installation (where the solar

circuitry is linked to the utility company’s

grid, for example) the inverter is also tasked

with sensing the utility power frequency and

must synchronise the PV-produced power to

this frequency.

When utility power fails (due to a power

outage) the inverter will automatically stop

producing AC power to prevent ‘islanding’

or putting power back into the national grid

when workers might assume the system is

de-energised. This safety feature is built into

all grid-tied inverters.

Optimising electrical

infrastructure

One of the benefits of designing a green

building from the outset is the optimisations

that can be made in the electrical infrastruc-

ture. 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. No ‘chopping and hacking’ required.

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 if battery backup and

storage is to be included in the design.

In the domestic area, for example, the

solar PV-based house will have a number of

special design features, including non-elec-

trically-powered ovens and hobs, solar

powered swimming pool pumps (set up

to run during the day to minimise storage

demands), LED lights and a lack of under-

floor heating – the planning and simplifica-

tion of which ahead of construction will mini-

mise costs.

Energy efficient

guidelines

Despite any official encouragement or

support for solar installations in South

Africa, many architects are beginning to

design buildings following energy efficiency

guidelines. These include creating structures

that readily integrate solar PV panels and

systems, rather than fitting them ‘as an after-

thought’ to existing structures.

The efficiency and reliability of solar

installations including PV modules, inverters

and batteries can be substantially improved

in residential, commercial and industrial

buildings by their architects’ early ‘buy-in’ to

solar technology.

Before setting out to design a ‘solar-

friendly’ building, it is important for archi-

Design for

SOLAR ENERGY

By John Hope-Bailie, a director of power provisioning specialist, Powermode.

Globally, the move towards the construction of green or sustainable buildings is gaining

momentum. The terms refers to an environmentally responsible structure that is resource

efficient. The concept encompasses all stages of the building’s life-cycle, from siting to

design, construction, operation, maintenance, renovation and demolition.