QUICKTIP

Put an overcoat on your windows!

In winter we put a coat on ourselves if we have to go out in the cold. We need to do the same for our windows. Closing your curtains at night is like putting an overcoat on your windows. In fact if the curtains seal well (ie you have pelmets and they are a reasonably snug fit at the bottom and sides, they halve the loss. In addition to keeping the heat in, curtains block the direct radiation of heat from your body to the outside. This fact isn't included in the calculation of the U-value of a window and is one reason that even if you have double glazing, you still need curtains at night. Even a poor quality curtain or blind will give this benefit as it just has to be opaque to stop the direct transfer of radiation.

Because you only get the benefit if you actually remember to close your windows, I am looking at home automation products to automatically do this. Unfortunately this is not as easy as it should be. When I have a reliable system, I will let you know.

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EDITORIAL

How will we store wind energy?

One of the criticisms of wind energy is that it is variable and doesn't generate energy when you want it. This is an issue which needs to be dealt with as the proportion of wind energy on the grid increases.

One way currently being developed in the Netherlands is to use large commercial cold stores (freezer rooms)as a store for the energy. When there is excess wind power being developed, the refrigeration system is made to reduce the temperature in the store below the normal level. Then when less wind power is available, the cold store temperature is allowed to rise, reducing the electrical use by the cold store. The technology is relatively easy to implement. Because the refrigeration system is sized for extreme conditions, it typically has 30-40% spare capacity so there is no cost to increase the refrigeration capacity, just the cost of an appropriate controller. The main issue that needs addressing is that the cold store needs to be on an hourly tariff.

Once hourly tariffs are common (initially for large commercial users of electricity), many similar ways of effectively shifting the load will be developed. Other examples are ice storage air conditioning, storage hot water and concrete slab underfloor heating. Even these examples add up potentially to a substantial portion of the total electrical demand. This means the limit to our use of wind electricity is our ability to appropriately price electricity, and not any inherent technical limit.

If you have any comments please contact us.

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PRACTICAL ENERGY SAVING

What are my heating options?

It is important to decide what you need to achieve first, and then choose an option that will achieve what you need, but not more. This is because the more you try to do, the more you will pay in purchase cost, running costs, and greenhouse gas production.

Most heating equipment costs more to run in its lifetime than the original purchase cost. (Some can cost more to run in one year than the purchase cost.) Hence it is worth making sure that your money is spent as wisely as possible. The first step is to decide what you really need (in terms of how much to heat). Remember the objective is to keep warm, not necessarily to buy an air conditioner or heater. The next step is to determine what changes to the house you will make and what type of equipment you will use in order to achieve the objective. The final step is to choose the features and the brand that you want. If you have bought a copy of House Taming: How to reduce greenhouse gases in comfort you can download the Heating & Cooling Needs Worksheet from www.coolmax.com.au/ht to help you with this task.

Step 1 How to work out your needs

AUSTRALIA is a land of extremes. Although we think of it as hot, in much of Australia winters are too cold to get by without heating unless you have an exceptionally well designed home.

How large an area do you need to heat or cool?

When deciding what areas to heat you need to balance cost against convenience. The more you heat the higher the cost of the equipment and the higher the running costs and greenhouse gas emissions. The running cost should not be ignored, as heating is often the largest single energy user.

The ideal from the greenhouse gas perspective, would be to not heat any of the house. Given that it is difficult to modify an existing house so that it needs no heating or cooling, most people will need to heat at least one room. If you are heating only one room, generally the main living area is chosen. If your home is well designed and operated, you may well find this takes the edge off (most of) the other rooms so this might be all you need.

Whole of house heating

If you intend whole of house heating, there are too many issues to go into here, so I suggest you get a copy of House Taming: How to reduce greenhouse gases in comfort which goes into this in more detail.

What is your climate?

In some climates (eg. Brisbane) heating requirements are minimal and if you have a reverse cycle air conditioner, heating will be satisfactory. Further south reverse cycle air conditioning only provides acceptable heating in mild climates. In cool climates you may be better off with gas or a slow combustion heater. Hot air rises so if it is supplied at high level like in a reverse cycle air conditioner, it wants to stay there, leaving cool air at feet level. For maximum heating comfort the air needs to be supplied at low level (near the floor). As the warm air rises it mixes with the colder air leading to a more even temperature throughout the room. This means that for colder climates (eg Melbourne) or for poorly insulated buildings (or buildings with lots of large windows) reverse cycle may not be adequate, as the ducts (or wall unit) are usually up near the ceiling. Because of this problem many people use gas heating, even though they have a reverse cycle air conditioner. If you are on green power then reverse cycle heating will produce less greenhouse gas than gas heating. Otherwise, provided you compare similar star rating appliances, there is not a dramatic difference between greenhouse gas production from gas heating and reverse cycle heating.

How important is aesthetics?

The ideal heater or cooler is completely invisible. However, in practice (except for electric floor or ceiling heating,) all heaters take up space and need grilles or vents to get the heat in or out. Depending on the design of your house, different heating systems will have different levels of impact on the appearance of your home. For example flat roofed houses that use ducted air conditioning have ugly visible ducts on the roof. On the other hand ducted systems generally have the minimum impact on indoor aesthetics. Quite often there is a trade-off between costs, greenhouse gas emissions and aesthetics.

Comfort level

The next thing you need to decide is the level of comfort you desire and whether you are prepared to pay for it. There are a number of things you need to consider.

Getting the correct size air conditioner is critical to achieving comfort. Australia’s most accurate cooling load calculator intended for use by the general public can be purchased at www.coolmax.com.au.

Purchase cost

A low purchase cost is of course attractive, however it may be better to air condition a smaller room with a good quality, correct size unit, than to attempt to heat a large area with a 'cheap' unit.

Running cost

Electricity costs are projected to rise over the longer term. This means that running an electric heater is likely to be prohibitively expensive, particularly if it relies on convection not radiation. The exceptions are if it is only on for a short while, like a bathroom heater, or it is on night tariff (a storage or underfloor heater).

In spite of the fact that electricity shortages occur in summer not winter, most people will find they will spend more on heating than cooling. The reason for this, is that heat waves tend to be followed by cooler periods, which don't require cooling, whereas winter never really gets warm in much of Australia, and heating is required more or less continuously.

Choose an efficient brand (check the star ratings (www.energyrating.gov.au- the more stars the better),

Other issues

• Noise levels
• What restrictions does the house design place on you?
• Is mains gas available?
• Do you have any specific needs?

More on all these issues is included inHouse Taming.

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