Energy

Designing homes to conserve energy and use it efficiently, from sources that cause least environmental harm.

Inverters

An inverter converts DC electricity to AC electricity and is required where electricity is a DC current such as from photovoltaic generation or where electricity has been stored in batteries, to convert the DC into AC.

On this page:

  • Requirements for provision of AC or DC power
  • Inverter types
  • Installation

The inverter can supply AC current at any voltage or frequency by transformers, switches and control circuits.

Requirements for provision of AC or DC power

Electricity supply to buildings must be provided as:

  • AC at 240 V and 50 Hz for single-phase power – for most household applications and wiring circuits
  • AC at 415 V and 50 Hz for three-phase power – for permanently wired and heavy load systems
  • DC if there are appliances with a DC supply.

There are losses each time power is converted from AC to DC and vice versa.

Inverter types

Several options are available:

  • True sine wave inverters produce voltage equal to or better than the grid supply. They may incorporate a battery charger, which allows a generator or CHP unit to be used to charge up the batteries when natural charging conditions are poor.
  • Modified sine wave inverters are less complicated but they may not successfully run some appliances, and they may produce a hum.
  • Grid-connected inverters allow for a connection to the grid, they may incorporate a battery charger and they can provide back-up power if the grid power fails.
  • AC coupled inverters are designed for use for a micro-grid, i.e. a property with several houses or a remote rural settlement with no national grid connection.

Installation

Inverters should:

  • be mounted above the floor and on a wall or shelf
  • have ventilation or cooled air flow
  • be protected from sunlight
  • be easy to access for emergency operation
  • have a switch or fuse to isolate the inverter from the electrical systems
  • be in close proximity to the batteries.

They must also be:

  • protected from dust
  • protected from overheating
  • electrically isolated in case of an emergency
  • protected from damage by lightning
  • connected to the batteries with large cables, as there may be substantial current flows, voltage drops and heat dissipation.