In the developed countries, we are exceedingly wasteful in our domestic utilisation of energy. With little or no hardship, we can immediately make substantial reductions in energy consumption and energy costs. If energy efficiency is incorporated into the design of new buildings, the design improvements may require little or no additional expenditure on construction.
For many years, the C.S.I.R.O. has carried out valuable research into improved, more energy-efficient, building design. Their recommendations should be universally adopted.
In 1967, I designed and had built an energy-efficient house. It was a comfortable dwelling, without air conditioning. It embodied design principles having moderate construction cost, which would be just as applicable today.
Electrical Power Consumption
Every consumer can make an immediate and substantial reduction in electrical power costs, simply by replacing incandescent lamps by inexpensive LED equivalents. They are around 5 times more efficient than filament lamps, last for at least 50,000 hours, and save cost for electrical power.
Recently, there have been doubts of the wisdom of increasing the usage of mercury vapour fluorescent lamps, because of the problem of disposal of waste mercury from worn-out domestic lamps. Fluoroscent lighting equipment may also utilise PCB (polychlorinated bi-phenyl) insulating oil in power factor correction capacitors, which is highly carcinogenic, and which may be released if the metal case ruptures as a resdult of failure. There should be no such problems with white LED lamps.
If you have air conditioning, save a considerable amount of power by adjusting the thermostat upwards by 2 or 3 degrees. During cool periods, turn the air conditioner OFF and circulate external air, make use of natural ventilation. In new construction, revert to the old system of high ceilings, to encourage natural ventilation with cool air. More use could be made of passve air-conditioning systems, in which thermal energy is stored and released through liquid/crystalline solid phase change of eutectic salt solutions, without the use of electrical power.
Heat-reflecting paint will significantly reduce the input of thermal energy through exposed roof or walls.
Use solar photo-voltaic or solar thermal water heating for the bathroom. There is absolutely no sense in wasting power to heat water to an unecessarily-high temperature, when we have to add cold water to bathe or shower without scalding. We should avoid the circulation of hot water throughout the house.
Individual solar hot water systems for kitchen and bathrooms may prove adequate for domestic needs, augmented if necessary by single-point electric, gas or lpg instantaneous on-demand water heaters. Central storage systems waste energy and potable water by piping hot water to multiple distribution points. Must we flush the entire system when we wish to draw a cupful of warm water into a handbasin?
The waste heat from refrigerators and airconditioners should be transferred, through liquid-cooled heat exchangers, to heat the water for kitchen sinks and handbasins. Why add to the heat load in a kitchen by air-cooling the appliances? Fitting liquid-cooled heat exchangers would be a simple design change for appliance manufacturers, and would offer reduced running costs and increased efficiency. Alternatively, the waste heat which is generated by appliances should be exhausted to the outside air, by fitting ventilation hoods in the ceiling.
Alternative Energy Supply - Solar Power
(See also Renewable Energy Sources)
At a cost of several thousands of dollars, it is possible to install a solar-powered domestic power source, using silicon photovoltaic cells. Government subsidies are available in Australia to householders who install solar power systems, and this is commendable.
The system can draw upon the normal mains supply for power when there is insufficient sunlight to meet demand. Larger, more expensive systems can return surplus power to the public supply and the householder can receive a rebate on the electricity account. However, it may be more cost-effective to install storage batteries, use surplus power for water heating, and to operate fully Off the Grid.
In remote areas, where connection to the mains power grid is not available, backup is provided by storage batteries, by wind power, and by diesel generators for higher power systems. Since installing solar power, the owners of such systems are benefitting from very significant savings in the costs of maintenance and of diesel fuel. (A commercial example of such a system has been developed by Sundrop Farms of Port Augusta in South Australia.)
Recent design improvements to silicon photovoltaic solar panels (sliver cells) are lowering manufacturing costs and increasing efficiency. New types of photovoltaic cell, e.g. using organic materials, offer reduced cost.
Attention is now being given to solar thermal power generation. During daylight hours, solar energy is concentrated by steerable solar-tracking parabolic reflectors, or by parabolic trough reflectors, onto "boilers", which melt mineral salts. The hot molten salt is stored in large tanks, where it is used to raise steam for power generation. The thermal capacity of the system is sufficient to generate base-load electrical power throughout the night. This method of power generation is especially suitable for small regional communities, where there is adequate available land area, but modest power requirements.
Alternative Energy Supply - Wind Power
(See also Renewable Energy Sources)
Rural property owners with sufficient space may use a wind generator to supply power needs, with battery or diesel generator backup for periods of low wind speed. In future, the diesel generator may be replaced by fuel cells and a gas storage tank for methane or hydrogen gas.
Larger "wind farms" which feed into a local grid are already operating in several areas of Australia. These have an estimated operational life of the order of 25 years. Individual turbines may have a maximum output power of the order of 25kW - 1.5MW. Grid connection over a large region will reduce periods of "no wind" for the system. The DC "Supergrid" offers improved performance and operational benefits for such systems. Unlike solar power, wind power is available throughout the day and night.
Alternative Energy Supply - Stirling Engines
The Stirling engine was invented in the 1830's by a Scottish clergyman. It was a safe alternative to the steam engine, which required a dangerous pressurised steam boiler, regular maintenance, and a trained operator.
The Stirling engine still has supporters, because it satisfies low-energy requirements, is an "external combustion" engine with no boiler, is quiet in operation, and has a long operational life.
However, as with all heat engines, the thermodynamic efficiency is determined by the temperature differential between the energy source and sink, and this is low for the Stirling engine, significantly less than for a modern steam reciprocating engine or steam turbine.
However, in commercial applications, a Stirling engine may utilise the waste heat from, say, a gas turbine power station and increase the overall efficiency to almost 90%.
A manufacturer in New Zealand produces gas-powered Stirling engine modules, which heat water, provide space heating, and generate grid-connected electrical power. These are designed for domestic use and may be housed in a cupboard. The standard module is claimed to generate 2.5kW of electrical power and provides 5kW of heat for space heating and water heating. Late in 2006, it was announced that 200 of these modules had been ordered for installation in a new housing project in Manchester, U.K., to be powered by natural gas. However, this type of application would only be economic in cold climate countries.
Recently, a German ceramic fuel cell has been used by an Australian manufacturer to produce a similar domestic power module, which uses methane, natural gas or lpg as a fuel source. The fuel cell operates at high temperature, resulting in an efficiency as high as 65% at rated load. The waste heat may be used to heat water, with an increase in overall efficiency. This module would be very suitable for domestic installation in Australia. Because of its high efficiency, it would result in a significant reduction in CO2 emissions, when compared with a conventional source of mains power.
Evaporative Cooling Systems
In some locations, the relative humidity is sufficiently low during hot periods to allow the use of evaporative cooling systems. Air is passed through a wet filter, before being circulated in the building. The evaporation of the water extracts latent heat from the air, which is therefore cooled. It is important to recover the water or to exhaust the humid air from the building, to maintain a comfortable internal environment.
Larger, more sophisticated systems circulate the cooled air through a secondary heat exchanger, to reduce the humidity of the cooled air.
Relatively little energy is required to circulate the cooling air, so evaporative cooling is attractive in many situations. It works well in Adelaide, for example, on all but perhaps 5 or 10 humid days per year, but is totally unsuitable in the invariably humid climate of Singapore.
Depending upon the location and local environmental conditions, it may be posible to use one or more of a number of passive air-conditioning systems. They have been used in limited applications in Outback Australia in the design of unattended shelters for low-power telecommunications equipment.
Smart systems use thermal convection current to circulate air or coolant fluids, supplemented by solar-powered pumps where necessary. The traditional Australian house had high ceilings, to encourage natural air circulation by convection.
Passive systems may incorporate thermal energy accumulators, which use physical phase change of the contents to exchange energy over a relatively small temperature differential. They may provide a large thermal storage capacity in a small volume.
In the U.S.A., buried heat exchangers seem to be popular as thermal heat sinks. These rely upon the relatively constant temperature of the earth at a depth of just a few metres. (more than 50 years ago, Professor Mike Tyler of Adelaide University established that desert animals enjoy a benign micro-climate, cool and humid, in their burrows. Buried houses and underground cellars, as in Coober Pedy, offer similar benefits.)
Inexpensive solid-state heat-pump wafers, which apply the peltier effect with low voltage DC power, are now available with energy pumping capacities up to 500W. At lower power ratings, they are already in service in portable refrigerators and water-coolers. They are directly compatible with photovoltaic power sources, which is possibly of benefit in portable installations.
One or more modules will provide enougth cooling effect to function as a domestic airconditioner or refrigerator. They would be ideal as simple, inexpensive airconditioners for motor cars. There is no refrigerant charge, such as is used in conventional devices, so the fans or pumps which may be required to heat or cool heat sinks are inexpensive and consume little power. They are non-polluting.
Peltier heat pumps are most effective with a low temperature differential between the hot side and the cold side, but may easily be cascaded for more demanding applications. The direction of heat transfer is reversed by reversing the polarity of the electrical connection.
We feel smugly self-satisfied that we are able to spend perhaps $200,000 or more upon a spacious, pretentious, energy-inefficient house, while a resident of East Timor would be delighted to have a comfortable, smaller house costing $2,000. Be prepared to tighten the belt as we make essential changes in our lifestyle.
(Lease the land! The State should retain ownership of land for housing subdivision. If the individual house allotments are leased to the house owner, over say 49 or 99 years, the cost of construction may be separately financed by the house owner so that total mortgage costs may be considerably reduced.)
The key to energy conservation in a building is to design for minimum unwanted transfer of thermal energy, both in and out of the building.
This is determined by the method of construction, by the location of the site and of adjacent structures, by the orientation of the surfaces of the structure, i.e. walls, windows and roofs, and by surface finishes.
In most domestic buildings, energy transfer is primarily through the roof. In conventional constructions, the roof structure should be well-insulated, using mineral or glass fibre batts or incombustible fibre fill placed over the ceiling, and the roof space should be ventilated. This technique reduces the conduction of heat between the roof space and the accommodation area. If reflective foil is installed under the roof surface, then in winter the roof ventilation may be disabled and the hot air in the roof space may be diverted into the house to provide space heating.
The incorporation of overhanging eaves or a verandah, particularly on the north-facing aspect of the building in the southern hemisphere, can assist in energy conservation. This may shade the wall during summer when the elevation angle of the sun is greatest, while allowing low-angle radiation to warm the wall during winter.
Espalier-trained deciduous trees on the sunny face of the building, located perhaps 5 metres from the footings, will provide valuable shade in summer but allow warming of the building during winter. A deep trench with waterproof membrane, located between the trees and the footings, is necessary to prevent wetting of the footings and possible seasonal soil movement.
The ultimate in roof insulation is provided by buried construction. Cave dwellings and dugouts are familiar and accepted in such arid desert locations as Coober Pedy in Australia, and are renowned for the cool, stable temperature of the accommodation. Buried construction may be economical on a sloping site, using reinforced concrete construction in an excavation into the hillside, and with earth fill over the building. In order to prevent dampness, the whole of the building must be sheathed with a specialised constructional plastic membrane, e.g. Fortecon, before casting the floor slab and before backfilling over the walls and roof.
Walling normally serves two purposes, namely (1) structural support of the roof and of other components such as doors and windows, and (2) cladding the structure. Conventional building construction usually clearly separates these two functions.
For example, double-brick construction uses the inner leaf as the structural member, while the outer leaf provides the cladding. The combination of two brick leaves separated by an air cavity provides excellent thermal insulation, since the transfer of heat from the outer to the inner leaf is primarily by radiation across the air cavity and is quite inefficient. It is important to avoid bridging the inner and outer leaves with mortar during construction.
In brick-veneer construction, a timber, galvanised steel, or aluminium structural frame is combined with an outer non-structural leaf of brick, or some other material such as ceramic tiles, fibreboard, structural ply, marine ply or weatherboard. The frame is usually wrapped with a vapour-permeable building paper. Mineral or glass fibre batts are installed inside the frame before applying internal finishes, e.g. plasterboard or panelling.
Steel frame or post-and-pole construction employs a structural frame, with infill panels using materials such as mud bricks, straw bales, on-site cast reinforced concrete panels, lightweight concrete blocks, glass bricks, bottles, wattle and daub, or whatever else is handy at the site.
Heat-reducing film or tinted glass, or external sun screens, may be fitted to east- or west-facing windows to reduce glare or unwanted heat transfer in summer. Heat reflecting paint, applied to exposed walls and roof surfaces, has been popular in the U.S.A. for many years and has more recently become available in Australia. As a result of the rapidly reducing cost of consumer electronics, it may now be economic to replace one or more windows by large-screen TV/video monitors.
If these measures are incorporated during construction, then little if any air conditioning may be necessary for comfortable living.
The higher project cost of public buildings allows the consideration of more energy-efficient environmental control systems. Some of these systems have been in service for more than fifty years. Since the rate of environmental energy exchange is proportional to the square (i.e. the second power) of the dimensions of the building, while volume is proportional to the cube (i.e. the third power) of the dimensions, it follows that the larger the building, the greater the possible energy efficiency.
Probably the first such energy-efficient project was the South Bank Theatre in London, which uses pumped heat from the River Thames for temperature control of the interior of the theatre.
A more recent example, in the 1960's, was BHP House in Melbourne, which is powered entirely by natural gas, with back-up connection to the electricity grid.
The Bolivar Sewage Treatment Works in South Australia generates its own electrical power for pumping, by utilising methane gas from sewage treatment, in i.c. gas engines.