Author : Hans De Keulenaer
Nine possible systems and a consideration
Until 250 years ago, wood and peat were the only means to heat a home. At present, there is a growing variety of residential heating systems. It is not easy to formulate an opinion which system is best in terms of environment, economy and comfort. But does the ideal heating system of the future really exist?Each system has its own advantages and disadvantages. Which technology is the best should be evaluated on a case by case basis, without any prior exclusion of technologies.Primarily nine different systems are being used today:
Natural gas is the most environmentally friendly fossil fuel, especially when it is burned in a high efficiency boiler with heat recovery. Yet it requires a gas network. And maybe natural gas should be used for generating electricity?The oil boiler is a similar system to the gas boiler, yet with a higher emission rate. It doesn't require a network but a storage tank and road transport. The oil boiler is likely to loose market share in the upcoming years.Electrical heating has been out of grace for some time in some countries, but today it is again seen as one of the heating systems of the future. An electrical system can be an efficient and cost-effective alternative when electricity is generated from low carbon sources, or when the heating demand is relatively low - for instance in new, compact, and well isolated houses. The heat pump. Since it takes over 2/3 of its energy output from the environment, it has a very high efficiency. But a ground-water heat pump requires a large surface. It should be combined with a low temperature heating system in a well insulated house, but the investment is only cost-efficient if there is a sufficient heating demand. A best practice solution for relatively large buildings in temperate to cold climates. Reversible heat pumps could be used in climates where there is both a heating and cooling requirement. Domestic CHP (Combined Heat and Power) is an emerging technology. It has the advantage that it makes fully use of the capacity of natural gas to produce electricity - a high quality energy carrier. But it requires matching heat and electricity demand, and may produce too much heat for well insulated dwellings with relatively low heat requirements. District heating with a central CHP plant is only efficient in (compact) cities where buildings have a sufficient heat demand. So the better houses are insulated, the less interesting it becomes. Only in cold climates, the heating demand will still be large enough to justify an investment in district heating. An important consideration: if a district heating network already exists, reducing the heat demand of dwellings (e.g. by improved insulation) is still a good idea, since new technologies allow producing more electricity for a lower amount of heat. Coal stoves are regarded as an old-fashioned way for residential heating. Nevertheless, they are still commonly used in many countries. They produce a comfortable heat atmosphere and have a fairly good efficiency. But they are inconvenient to operate, and CO2 emissions are high. In Europe, the market share of coal as an energy source for heating will probably continue to decrease.Most coal stoves can also burn wood or wood pellets. The influence of wood pellets on the global CO2 emissions requires more investigation. Maybe wood should ideally be used for CO2 storage rather than energy carrier? Solar energy. A solar water boiler can be combined with low temperature heating. A wind or photo-voltaic system can be the energy source for electrical heating. None of both systems will be able to supply large power, so they should be used in houses with small heating demand or combined with other sources. Photo-voltaic systems have the disadvantage that they produce most power when the least heating is necessary, but solar cooling is an application where ambient generation will naturally match demand.
And to conclude a consideration. A house can be seen as our third skin, while our second skin consists of clothes. Reinforcing both skins can save a lot of energy, money, and CO2 emissions. The third skin can be improved by a maximum insulation, an excellent airtight construction, use of sun heat by intelligent glazing, and ventilation with heat exchange. The second skin can be improved by simply wearing an extra sweater! This allows setting the thermostat a bit lower - we know 1 degree results in a few % less energy per year.Or we could use electricity even more intelligently. In Asia, so-called 'kotatsu' tables have an (electric) heating element underneath and a blanket and they are being used to heat just a small amount of space. They're quite comfortable, provide the emotional center for the home and one of the most efficient ways possible to provide high heating comfort to occupants. A similar system exists in Southern Spain.In short, it is not easy to compare a variety of heating systems, used in different climates to provide various lifestyles.------------------------------------------------------
Hans De Keulenaer manages Leonardo ENERGY initiative, the Web portal for sustainable energy professionals.http://www.leonardo-energy.org
Category : Reference-and-Education:Science
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