666 ABC Radio

Centre Manager Ray Prowse is interviewed by Alex Sloan on 666 ABC radio in Canberra.

Date: 19th October 2006

Topic: Grid Connected Solar Electric Systems

Content: Ray explained the system components, cost, rebates and greenhouse gas savings of a typical 1kW system.

The components are the photovoltaic (solar electric) array of panels, an inverter to convert the DC electricity produced by the panels to AC which can be fed into the local electricity grid and a change over switch (generally used only if the home owners want to run their house directly from the solar array at times of high output).

The cost of a typical 1kW system is in the range $16,000 to $18,000.

The federal government provides a rebate of up to $8,000 under the Photovoltaic Rebate Program (PVRP), which brings the cost of the system down to between $8,000 and $10,000.

There are presently about 10,000 grid connected solar electric system in Australia.

Greenhouse Gas Reduction. The same 1kW system at a location where there are 5 peak sun hours per day will produce 5kWh of electricity and will prevent about 5kg of CO2 from being released into the atmosphere from coal fired power stations.

Date: 3rd November 2006

Topic: Un-interruptible Power Supplies (UPS)

Content: Following on from the previous topic of grid connected solar (PV) systems, Ray explained the technology and operation of un-interruptible power supply systems (UPS).

A UPS uses a bank of batteries to store energy during normal operation and, if there is a power outage from the electricity grid, power can be drawn from the battery bank to run essential items. Essential items could be computers and other IT devices for a business or an air-conditioner for a domestic residence. In fact any load item that the owners cannot do without can be run from the UPS.

The size of the battery bank is determined by the power rating of the items to be powered and the time that it needs to be run before the grid comes back on again. For large items the battery bank capacity can be quite large and the cost high, so a decision has to be made about what level of autonomy os required.

Such batteries must be installed to the appropriate Australian Standard for battery installations (AS 4086.2 is a good start). Depending on the size and type of battery used they can be installed close to the load item or , for example, on the back verandah provided that the battery enclosure is secure and well ventilated and all requirements of the standard are met.

Other equipment required is a battery charger to keep the battery bank fully charged at all time, a bi-directional inverter to feed electricity between the electricity grid, the battery bank and the load and a change over switch to automatically switch from grid to battery bank and back again as required.

Date: 16th November 2006

Topic: Reducing Energy Demand

Content: The way to make a stand alone or grid connected solar system more economic is to reduce its size, i.e. reduce the size of the load that it is intended to run or reduce the amount of energy to be fed back to the electricity grid.

Load reduction can be achieved firstly by identifying those load items which consume the most energy. To do this look at the power rating on the appliance label and estimate the amount of time that item will be switched on. Multiply these together to get the energy consumed per day.

Secondly, replace high energy consumption load items with either more efficient appliances or replace them all together by using a different energy type to provide the energy service. e.g. replace the electric strip radiator with an efficient gas heater or reduce the demand by adding insulation to the walls and ceiling or increase the solar heat gain by installing north facing windows.

New houses in the ACT must be built to a 5 star energy efficient rating. (Click here for details of the house energy rating scheme.) Existing houses can be retrofitted to improve their efficiency. The HEAT program in the ACT provides such services to residents in the ACT.

Date: 30th November 2006

Topic: Phantom Loads and Switching Fluoro Lights

Content: What is the latest thinking on switching fluoro lights off when you leave the room?

From the point of view of energy consumption due to the operation of the light, switch it off immediately on leaving the room. A fluoro light uses about 5 times its normal power to start to tube. However this takes a few milliseconds with modern electronic ballasts, so the energy used is negligible.

Remember that a light which is switched off uses no energy at all!

If the energy required to manufacture the fluoro tube and the reduced lifetime of the tube are taken into account then it makes sense to leave it running if out of the room for short periods of time. There is much debate about the length of time with estimates varying from as little as a minute to as much as 20 minutes. The exact time requires a whole of life cycle assessment taking many externalities into account, e.g. the energy used to transport the fluoro tubes from the manufacturer to the retail outlet and a portion of the lighting required at that retail outlet.

A definitive answer is not presently available.

What are phantom loads and what can be done to reduce their impact?

These are electrical devices which continue to consume energy even though they are turned off. They may also be small electrical devices which run 24 hours a day. Examples are clock radios, LCD displays on the DVD and TV, bubblers in the fish tank, water beds etc.

Many of these devices can be turned off at the power point when they are not in use. The hassle is that the programming and time need to be re-set when the device is turned on again. That decision is up to the individual, but they must remember that energy consumption, electricity charges and greenhouse gas emissions will continue to rise if we use more and more electrical devices which use small power, but are switched on all the time.

Date: 14th December 2006

Topic: Cooling Systems

Content: What are our options for keeping cool in summer - apart from leaving the house and going to the shopping mall?

The simple answer is that a house which doesn't heat up doesn't need to be cooled. Applying good energy efficient design practices will work well in winter to reduce heat loss and maximise heat gain through north facing windows. The same house will reduce the heat gain in summer by keeping solar radiation off all windows by the use of appropriate shading devices and will reduce heat gain through the building envelope via the use of good insulation practices.

If the house does heat up the most effective way to cool it down is by providing obstruction free paths for cross flow ventilation.

When all else has failed and you need to install an air conditioner what sort should you get?

There are two types - evaporative and refrigerative.

Evaporative uses a fan to blow air across a mist barrier and then into the house. These work well in a dry climate like that in the ACT. They do not work so well in a humid, moist environment (typically coastal or tropical) because evaporation does not happen so efficiently and the cooling effect is minimal.

Refrigerative units use a motor to drive a compressor; it's effectively a refrigeration cycle with the house being the interior of the fridge. There are often reverse cycle so that they can provide heating in winter.

The fan in an evaporative unit is typically about 80 - 100 watts and the motor in the refrigerative unit may be several kilowatts. Hence the evaporative unit is considerable cheaper to run because it is lower powered and uses less energy.